800MHz auction: Co-existence of LTE systems in 790-862 · PDF file800MHz auction: Co-existence of LTE systems in 790-862 MHz with Digital Terrestrial Television - August 2011 Contents

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800MHz auction: Co-existence of LTE systems in 790-862 MHz with Digital Terrestrial Television

August 2011

Contents i

800MHz auction: Co-existence of LTE systems in 790-862 MHz with Digital Terrestrial Television - August 2011

Contents

1 Introduction 10

1.1 Structure of this document 13

2 Overview of approach and main assumptions 14

2.1 Approach taken 14

2.2 Main assumptions 15

2.3 DTT coverage and frequency plan 17

2.4 LTE network assumptions 27

3 Analysis of LTE networks operating at maximum power levels 30

3.1 Summary of results 30

3.2 Effect of interference on indoor coverage of DTT 35

3.3 Conclusions from the initial analysis 35

3.4 Observations on relevance of the initial analysis to real LTE deployments 37

4 Impact of interference assuming realistic LTE deployment assumptions 39

4.1 Determination of individual EIRP levels 39

4.2 Impact of realistic EIRP levels on potential for receiver overload 47

4.3 Composite overload effect from three networks 51

4.4 Impact of using realistic EIRP levels on the potential for ACI 52

4.5 Impact of realistic EIRP levels on ACI in DTT Channel 60 areas 61

4.6 Effect on indoor coverage 70

4.7 Effect of site sharing between the three networks 74

4.8 Near-field interference effects 74

4.9 Summary of results 75

5 Evaluation of possible mitigation measures 79

5.1 Use of DTT receiver filters 79

5.2 Mitigation via additional filtering on LTE base stations 82

5.3 Use of cross-polarisation between LTE and DTT 83

5.4 Improving the DTT signal level via on-channel repeaters 84

5.5 Mitigation via improving DTT receiver design 85

5.6 Platform change 87

5.7 Other forms of mitigation 88

6 Interference from LTE uplink emissions 89

7 Conclusions and recommendations 91

7.1 Summary of the main interference issues 91

7.2 Conclusions on the suitability of different mitigation techniques 92

ii Introduction

800MHz auction: Co-existence of LTE systems in 790-862 MHz with Digital Terrestrial Television – August 2011

7.3 Recommendations 94

Annex A Blocking results by geo-type within Danish broadcast regions (initial analysis) 96

Annex B : DTT site characteristics for Channels 60, 59 and 58 in Denmark 98

Annex C : Maps showing areas of interference (initial analysis) 99

Annex D : LTE link budget 104

Annex E : Summary of modelling steps 106

Contents iii


Tables & Figures

Table 1 Channel plan for DTT multiplexes 1 to 6 [Source: NITA] .................. 20

Table 2 Regions in Denmark using upper DTT channels [Source: Analysys Mason] ........................................................................................................ 20

Table 3 DTT planning assumptions [Source: Analysys Mason] .................... 23

Table 4 DVB-T PRs in the presence of LTE interfering in a Gaussian channel environment [Source: ECC] ........................................................................ 24

Table 5 LTE-DTT channel offsets in MHz used in the ACI analysis [Source: Analysys Mason]......................................................................................... 24

Table 6 Correction factors applied to PR values [Source: Analysys Mason] . 25

Table 7 Interpolated PR values – Gaussian channel [Source: Analysys Mason] ........................................................................................................ 25

Table 8 Interpolated ratios with correction factors – Boxer DTT coverage [Source: Analysys Mason] .......................................................................... 26

Table 9 Interpolated ratios with correction factors – Digi-TV DTT coverage [Source: Analysys Mason] .......................................................................... 26

Table 10 PR values plus correction factors, Boxer coverage – fixed outdoor reception [Source: Analysys Mason] ........................................................... 27

Table 11 PR values plus correction factors, Digi-TV coverage – fixed outdoor reception [Source: Analysys Mason] ........................................................... 27

Table 12 Cell radii for LTE model [Source: Analysys Mason] ......................... 29

Table 13 Summarised results of blocking calculation from LTE to DTT, initial analysis (59dBm EIRP, with 56dBm in Channel 60 areas) – fixed outdoor reception [Source: Analysys Mason] ........................................................... 31

Table 14 Number of existing GSM900 sites of each operator in the area of analysis [Source: Analysys Mason] ......................... 32

Table 15 ACI to Channel 60 in Vordingborg, portable indoor reception [Source: Analysys Mason]......................................................................................... 35

Table 16 Calculated cell ranges for different EIRP levels [Source: Analysys Mason] ........................................................................................................ 41

Table 17 Theoretical site separation for different EIRP levels [Source: Analysys Mason]27 ..................................................................................................... 41

Table 18 Number of base stations within the North Copenhagen sample area [Source: Analysys Mason] .......................................................................... 42

Table 19 Number of sites per geo-type within the North Copenhagen sample area [Source: Analysys Mason] .................................................................. 44

Table 20 Receiver overload per network [Source: Analysys Mason] .............. 47

Table 21 Receiver overload using realistic LTE EIRP levels scaled nationally from the North Copenhagen sample area [Source: Analysys Mason] ......... 51

Table 22 Interference power sum of receiver overload from three networks for sample area [Source: Analysys Mason] ...................................................... 52

iv Contents


Table 23 ACI per network – Network A in blocks FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 53

Table 24 ACI per network – Network B in blocks FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 53

Table 25 ACI per network – Network C in blocks FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 53

Table 26 ACI from LTE block FDD 1 to DTT Channel 59 using realistic LTE EIRP levels, scaled nationally [Source: Analysys Mason] ........................... 58

Table 27 Number of sites per geo-type within the Ringsted-Sorø sample area [Source: Analysys Mason] .......................................................................... 63

Table 28 ACI per network – Network A in blocks FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 66

Table 29 ACI per network – Network B in blocks FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 66

Table 30 ACI per network – Network C in blocks FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 66

Table 31 ACI from LTE block FDD 1 to DTT Channel 60 using realistic LTE EIRP levels, scaled nationally [Source: Analysys Mason] ........................... 70

Table 32 PR values plus correction factors, Channel 60 coverage, portable indoor reception [Source: Analysys Mason] ................................................ 70

Table 33 ACI per network for indoor coverage – Network A in blocks FDD1/FDD2 [Source: Analysys Mason] ...................................................... 71

Table 34 ACI per network for indoor coverage – Network B in blocks FDD1/FDD2 [Source: Analysys Mason] ...................................................... 71

Table 35 ACI per network for indoor coverage – Network C in blocks FDD1/FDD2 [Source: Analysys Mason] ...................................................... 71

Table 36 ACI from LTE block FDD 1 to DTT Channel 60 using realistic LTE EIRP levels, scaled nationally, indoor coverage [Source: Analysys Mason] 73

Table 37 Site sharing in North Copenhagen sample area [Source: Analysys Mason] ........................................................................................................ 74

Table 38 The effect of using realistic LTE EIRP levels and increased site sharing on receiver overload [Source: Analysys Mason] ............................. 74

Table 39 Estimated reduction in the potential for blocking from use of DTT receiver filters using realistic EIRP analysis for selected Channel 59 area [Source: Analysys Mason] .......................................................................... 81

Table 40 Estimated reduction in the potential for ACI from use of DTT receiver filters using realistic EIRP analysis for selected Channel 59 area [Source: Analysys Mason] ......................................................................................... 81

Table 41 Estimated reduction in the potential for ACI from use of DTT receiver filters using realistic EIRP analysis for selected Ringsted-Sorø area [Source: Analysys Mason] ......................................................................................... 82

Table 42 Impact of improving the blocking threshold – modelled for one LTE network interfering with DTT, operating at maximum licensed EIRP [Source: Analysys Mason] ......................................................................................... 87

Contents v


Table A.1 Site data for DTT Channels 60, 59 and 58 [Source: NITA] ........... 98

Table D.1 LTE link budget for downlink [Source: Analysys Mason] ........... 104

Table D.2 LTE link budget for uplink [Source: Analysys Mason] ................ 105

Figure 1 Band plan for 470–870MHz in Europe [Source: Analysys Mason] ... 11

Figure 2 FDD channelling arrangement for 790–862MHz [Source: ECC] ...... 11

Figure 3 DTT directional receiving antenna [Source: ITU-R BT.419] ............. 18

Figure 4 Danish broadcast regions [Source: NITA]........................................ 19

Figure 5 Regions using Channel 60 [Source: NITA] ....................................... 21



Figure 8 Jaybeam antenna pattern [Source: Jaybeam, Analysys Mason] ...... 28

Figure 9 Areas of blocking from the three LTE networks [Source: Analysys Mason] ........................................................................................................ 32

Figure 10 Areas affected by ACI into DTT channel 60 from two LTE networks [Source: Analysys Mason] .......................................................................... 34

Figure 11 Illustration of areas of coverage overlap in one LTE800 network deployed on GSM900 sites [Source: Analysys Mason] ............................... 38

Figure 12 Selected area for analysis [Source: Analysys Mason] .................. 40

Figure 13 Approach to setting EIRP per base station site [Source: Analysys Mason] 40

Figure 14 EIRP required for different site separations [Source: Analysys Mason] 42

Figure 15 Site to geo-type matching – Network A [Source: Analysys Mason]43

Figure 16 Site to geo-type matching – Network B [Source: Analysys Mason]43

Figure 17 Site to geo-type matching – Network C [Source: Analysys Mason]44

Figure 18 EIRP per site and coverage – Network A [Source: Analysys Mason] 45

Figure 19 EIRP per site and coverage – Network B [Source: Analysys Mason] 46

Figure 20 EIRP per site and coverage – Network C [Source: Analysys Mason] 46

Figure 21 Areas affected by receiver overload – Network A [Source: Analysys Mason] 48

Figure 22 Areas affected by receiver overload – Network B [Source: Analysys Mason] 49

Figure 23 Areas affected by receiver overload – Network C [Source: Analysys Mason] 50

Figure 24 Areas affected by ACI – Network A in FDD1/FDD2 [Source: Analysys Mason]......................................................................................... 55

vi Contents


Figure 25 Areas affected by ACI – Network B in FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 56

Figure 26 Areas affected by ACI – Network C in FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 57

Figure 27 Areas affected by ACI only, compared to ACI and blocking – Network A in FDD1/FDD2 [Source: Analysys Mason] ................................. 59

Figure 28 Areas affected by ACI only, compared to ACI and blocking – Network B in FDD1/FDD2 [Source: Analysys Mason] ................................. 60

Figure 29 Areas affected by ACI only, compared to ACI and blocking – Network C in FDD1/FDD2 [Source: Analysys Mason] ................................. 61

Figure 30 Selected Ringsted-Sorø sample area for ACI Channel 60 analysis [Source: NITA] ............................................................................................ 62

Figure 31 Geo-types assigned to existing GSM900 sites in Ringsted- Sorø [Source: Analysys Mason] .......................................................................... 63

Figure 32 EIRP per site and coverage – Network A [Source: Analysys Mason] 64

Figure 33 EIRP per site and coverage – Network B [Source: Analysys Mason] 64

Figure 34 EIRP per site and coverage – Network C [Source: Analysys Mason] 65

Figure 35 Areas affected by ACI – Network A in FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 67

Figure 36 Areas affected by ACI – Network B in FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 67

Figure 37 Areas affected by ACI – Network C in FDD1/FDD2 [Source: Analysys Mason] ......................................................................................... 68

Figure 38 Density of households near Ringsted city area [Source: Analysys Mason] 69

Figure 39 Areas affected by ACI (indoor reception) – Network A in FDD1/FDD2 [Source: Analysys Mason] ...................................................... 72

Figure 40 Areas affected by ACI (indoor reception) – Network B in FDD1/FDD2 [Source: Analysys Mason] ...................................................... 72

Figure 41 Areas affected by ACI (indoor reception) – Network C in FDD1/FDD2 [Source: Analysys Mason] ...................................................... 73

Figure 42 Characteristics of UHF filter [Source: Braun Telecom] ................. 80

Executive Summary 7


Executive Summary

The National IT and Telecom Agency (NITA) is responsible for planning and preparing an auction of 800MHz spectrum for the final decision by the Minister of Science, Innovation and Technology („the Minister‟). In this regard, NITA has engaged DotEcon and Analysys Mason as advisers. Particularly, we have been tasked with: analysing the scope for use of this spectrum; assessing the risk of interference from the use of this band to digital terrestrial television (DTT) services; considering whether, and how, any coverage obligations may be imposed on the licences in pursuit of the government‟s overall broadband goal; and designing a suitable auction.

This report presents the results of theoretical modelling and analysis that DotEcon and Analysys Mason have conducted for NITA considering the potential interference to DTT from future mobile use of the 790–862MHz band („the 800MHz band‟) in Denmark.

The results of our analysis suggest that between 9 000 and 10 000 households nationally might be at risk of some kind of interference from mobile use of the 800 MHz band.

Two modes of interference have been considered; receiver overload and adjacent channel interference (ACI).

More detailed results of our analysis suggest that:

Between 2 500 and 3 000 households nationally might be at risk of interference from receiver overload

Between 4 500 and 5 000 households might be at risk of interference from ACI in areas of Denmark receiving DTT services using Channel 60, and up to 2 000 households in areas using Channel 59

Our analysis was conducted in two parts. The purpose of the first high-level analysis was to establish whether interference from LTE to DTT could potentially be a problem. This first part of the analysis considered the potential interference mechanisms into DTT that might occur from one or several long-term evolution (LTE) network(s) operating at assumed maximum licensed power levels, and the extent of interference created.

The results of this initial analysis suggested that there is considerable scope for interference from LTE to DTT if it is assumed that all LTE base stations operate at their maximum licensed power level.

Having established from our initial analysis that there could be an interference problem from LTE to DTT, we then conducted more detailed analysis to model the effects of a series of realistic LTE network deployments. This further analysis took into account that in practice, only a proportion of LTE base stations will transmit at the maximum licensed power level, and the majority will use lower power levels for various practical reasons (e.g. due to planning restrictions, other site restrictions or management of internal interference).

We found that the number of DTT households affected by receiver overload from three LTE networks across Denmark was reduced to around 2 500 - 3 000 DTT households. The effect of ACI is also substantially reduced for areas of the country using DTT Channel 59, with an estimate of around 2 000 DTT households in total being affected.

8 Executive Summary


We found that around 4 500 – 5 000 DTT households might be affected by ACI in areas of the country using DTT channel 60, as a result of interference from one LTE network.

The third and final part of the analysis was to assess the feasibility of further reducing the impact of interference predicted from LTE to DTT, through the consideration of various possible interference mitigation techniques.

Considering the range of possible mitigation methods that can be used to reduce the impact of LTE interference to DTT and/or to restore the DTT service, we found that the use of filters at DTT receivers appears to be the most cost effective and practical mitigation technique. Our modelling suggests that use of filtering will substantially eliminate interference from both overload and ACI, leaving a small number of households for which filtering is not suitable. These are most likely to be households viewing DTT services using Channel 60 and receiving interference from LTE block FDD1.

Other suitable forms of mitigation, which can be applied on a case-by-case basis, include filtering of LTE base stations (which can be used in conjunction with DTT receive filters to further reduce the number of households affected), cross-polarisation between LTE and DTT antennas (i.e. using the opposite of DTT polarisation at LTE sites), and installation of DTT on-channel repeaters. The latter might be particularly considered in areas where television viewing households are located at the edge of DTT coverage.

A possible further means of mitigation against DTT receiver overload and ACI would be to improve the immunity of DTT receivers, by designing them with a higher interference threshold (called overload threshold, or Oth) and protection ratio (called PR). A higher Oth and PR limit could be specified within receiver standards for DTT services, to ensure that future receivers are designed with a higher threshold and protection ratio in mind. Recent measurements conducted by the European Communications Committee (ECC) suggest that some DTT receivers on the market today already exhibit a better Oth and PR than assumed within the modelling for this report. It is noted that Denmark would not be able to make this change to DTT standards itself. It is possible that a change to standards could be market driven; if regulatory action is required, this would potentially require EU-wide cooperation, since standards for DTT are pan-European.

In conclusion, we have found that, whilst our initial analysis suggested that interference from LTE to DTT is a problem, in practice assuming that mobile operators will optimise the power and characteristics of individual base stations within their network (and not use maximum licensed power limits at all sites), the interference problem is substantially reduced. Application of the further mitigation methods discussed above could almost eliminate any issues, leaving only a very small number of affected DTT households – possibly of the order of a few hundred in total across Denmark. For the remaining few households that continue to suffer receiver overload or ACI after all appropriate mitigation methods have been considered, the only option would to use an alternative television (TV) platform such as cable, satellite or IPTV.

Given that operators are likely to apply reduced power levels in many areas of their network, we do not think it is necessary for NITA to consider any specific licence conditions within the 800 MHz licences other than a maximum EIRP limit. However, it is possible that additional requirements could be considered in relation to managing interference from the lowermost LTE blocks (FDD1/FDD2)

Executive Summary 9


to DTT services in areas of Denmark using Channel 60, which our analysis has suggested could be particularly problematic in terms of potential for ACI. It might be necessary to consider a reduced EIRP limit for base stations using blocks FDD1 and FDD2 although it is noted that this limit should be considered carefully in view of its impact upon the ability of mobile operators to provide LTE coverage, particularly in suburban and rural areas.

10 Introduction


1 Introduction

The migration from analogue to digital terrestrial TV (DTT) transmission is now well underway in most European countries, and was completed in Denmark on 1 November 2009. In Denmark, all terrestrial TV services are now being delivered digitally using DVB-T technology. These digital services, like the superseded analogue services, use UHF spectrum for their transmission. The UHF spectrum used for broadcasting was originally 470–862MHz, but the ITU World Radio Conference in 2007 (WRC-07) decided to allocate the upper part of this spectrum, from 790–862MHz, for mobile services on a co-primary basis with broadcasting.

Following WRC-07, the European Commission (EC) recommended that Member States make the sub-band from 790–862MHz („the 800MHz band‟) available for electronic communications services, via a decision published in 2010 (EC Decision 2010/267/EC). The EC also requested the European Communications Committee (ECC) to consider harmonised technical conditions, including a frequency plan. The Danish government has decided to award licences in the 800MHz band in line with the European harmonisation efforts: the underlying band plan will follow the European plan.

The harmonised European plan for the 800MHz band (as described in ECC Decision (09)03) divides the spectrum into two 30MHz blocks for FDD1 downlink and uplink respectively.2 There is an 11MHz duplex gap, which is intended for use by PMSE3 in Denmark.

According to the European Common Allocation Table (ERC Report 25), the band above 862MHz is designated for use by various short-range devices (SRDs), including RFID.4

There is a 1MHz guard band between 790 and 791MHz, which divides the top of the DTT spectrum and the first long-term evolution (LTE) channel.

The European band plan for 470–870MHz is summarised in Figure 1 below.

1 Frequency Division Duplexing

2 The conclusion of CEPT Report 31 was that the preferred frequency arrangement for the

800MHz band was an FDD plan. The 230MHz FDD plan with an 11MHz duplex gap was 2 The conclusion of CEPT Report 31 was that the preferred frequency arrangement for the

800MHz band was an FDD plan. The 230MHz FDD plan with an 11MHz duplex gap was subsequently defined in ECC Decision (09)03.

3 Programme-Making and Special Events

4 Radio-frequency Identification: applications that exchange data between a reader and an

electronic tag attached to an object, for the purpose of identification and tracking.

Introduction 11


Figure 1 Band plan for 470–870MHz in Europe [Source: Analysys Mason]

Assuming that the 800MHz band is divided into 5 MHz channels, this suggests six FDD channels can be accommodated within the band as illustrated in Figure 2 below (it is noted that the ECC also considered other frequency arrangements, including unpaired spectrum for time division duplexing (TDD) systems, but the recommended channelization is using paired channels).

FDD1 FDD2 FDD3 FDD4 FDD5 FDD6605958

DTT channels LTE FDD downlink

1 MHz

8 MHz 5 MHz

790 MHz 791 MHz821 MHz

11 MHz

Figure 2 FDD channelling arrangement for 790–862MHz [Source: ECC]

Throughout our report we therefore refer to FDD1, FDD2, FDD3, etc., as being consecutive FDD downlink channels of 5MHz bandwidth, starting from the 791MHz band edge, in line with the channel plan illustrated above.

As a result of various compatibility studies conducted within the European Conference of Postal and Telecommunications Administrations (CEPT), the band plan shown above for mobile use of the 800MHz band employs a duplex direction that is reversed when compared to the normal European convention. Normally, mobile bands are planned with the uplink (base station receive/mobile transmit) in the lower band and the downlink (base station transmit/mobile receive) in the

upper band. However, due to concerns regarding interference from future mobile transmission to DTT below 790MHz, it was decided for the 800MHz band to reverse the duplex direction, so that the downlink is in the lower band.

For the purposes of the interference analysis presented in this document, we have assumed that:

future mobile use of the 790–862MHz band will be based on LTE technology

LTE will use a 5MHz carrier width, which results in six channels (blocks) being available.5

5

In the remainder of this report we refer to these six blocks as FDD1 –FDD6.

12 Introduction


Although a 1MHz guard band has been incorporated into the European plan, it was recognised during the compatibility studies conducted by CEPT that such a 1MHz guard band might not be sufficient to resolve potential interference from LTE base stations to DTT reception below 790MHz. Two modes of interference are possible:

Adjacent channel interference (ACI) – interference caused by a transmitter operating in an adjacent channel.

Receiver overload (blocking) – occurs when a strong in-block LTE signal overloads the DTT receiver front-end, making it unable to detect the DTT transmission (regardless of the level the DTT signal is at).

Overload is primarily dependent on the absolute level of the LTE signal within the

DTT operating band, and has only limited dependency on frequency.6 ACI is

frequency-dependent, however, and is dependent on the ratio between the DTT and the LTE signal levels. The channels closest to 790MHz (DTT Channels 60, 59 and 58) are therefore likely to be the channels that are most susceptible to ACI.

The EC‟s 800MHz Decision defines certain baseline technical requirements for use by electronic communications networks deployed within the 800MHz band, which are aimed at reducing the potential for interference, while recognising that they will not resolve all cases of interference and that further restrictions might be required. The conditions specified in the EC Decision are defined using block

edge masks (BEMs) based on technical work conducted within the CEPT.7 The BEMs consist of in-block and out-of-block components, which specify the permitted emission levels for frequencies within, and outside of, the 800MHz block respectively (with particular regard to protection of adjacent DTT services below 790MHz).

The in-block limits incorporated into EC Decision 2010/267/EC provide flexibility for national regulators to determine an in-block EIRP limit if required. The Decision suggests that, unless otherwise justified, limits would normally lie within the range 56dBm to 64dBm (in a 5MHz bandwidth).

For the purposes of this study, NITA has asked us to initially assume a maximum licensed EIRP value of 59dBm in each of the LTE channels, except for two areas (Sjælland and Lolland-Falster) where DTT Channel 60 is used: in these areas a maximum value of 56dBm is assumed for LTE Channels FDD1 and FDD2 only. In our initial analysis, we assume that all base stations transmit at these maximum limits. In our subsequent analysis, we apply different EIRP levels at individual base stations, in line with more realistic mobile deployments.

The DTT-to-LTE interference analysis that is being conducted as part of this study therefore uses these assumptions as inputs to evaluate the potential for interference from LTE to DTT caused by overload and ACI, and the various ways that this impact can be reduced. All of the analysis described in this report has

6

This is illustrated by Table 5b of ECC Report 148, which lists overload threshold (Oth) values for different frequency offsets.

7 CEPT Report 30: Identification of common and minimal (least restrictive) technical conditions for 790–862MHz for the digital dividend in the European Union.

Introduction 13


been conducted using a radio planning tool to predict (area) coverage of interference caused by overload and ACI, and how this reduces when different mitigation techniques are applied either individually or collectively.

1.1 Structure of this document

The remainder of this document is structured as follows.

Section 2: Describes the approach and main assumptions used throughout the analysis.

Section 3: Assesses the impact of interference from one or several LTE network(s) operating at maximum power levels, summarising the main interference issues identified, and the various deployment scenarios and operational environments within which different issues are most likely to occur.

Section 4: Describes the results of our modelling of the impact of interference from multiple LTE networks operating at power levels consistent with actual power levels we believe might be used by mobile operators in practice, rather than all transmitting at the maximum licensed power level. In this analysis, we have selected a sample area to the north of Copenhagen, and evaluated the potential for receiver overload (blocking) and ACI to occur from LTE networks designed using base station locations based upon existing GSM900 networks, but with power levels at individual base stations individually determined based upon the location of the base station with respect to its nearest neighbour. In order to assess the potential for ACI to DTT Channel 60, we have also selected a further sample area – Ringsted-Sorø – which uses this channel.

Section 5: Describes our assessment of possible mitigation approaches – this describes the different approaches that could be used, and the deployment scenarios and operational environments in which they might apply. It also presents the analysis we have conducted into the suitability of different possible mitigation techniques, in terms of reducing the impact of predicted effects of overload and ACI from LTE to DTT.

Section 6: Describes potential interference effects from LTE uplinks (i.e. mobile devices) to DTT.

Section 7: Presents our conclusions and recommendations, including the conclusions on the use of practical EIRP limits below the maximum licensed limit, and the suitability of different interference mitigation techniques, along with various recommendations for NITA to consider in relation to finalising policy with regards to the conditions for award of 800MHz licences.

14 Overview of approach and main assumptions



2.1 Approach taken

The overall approach to modelling interference that we have adopted throughout our analysis uses a radio planning tool to predict coverage and interference. The tool used is the ATDI ICS Telecom radio planning tool (version 9.8.0). This has been used alongside a Microsoft Excel model and MapInfo software, to estimate coverage loss from interference and the associated impact in terms of the numbers of Danish households affected.

We have used the following data sets within our analysis:

Danish household data from The National Survey and Cadastre of Denmark (KMS)

digital terrain (height) data from Denmark with 50-metre resolution

clutter data with 50-metre resolution

site and frequency data for existing DTT sites from the ITU-R Geneva 06

(GE-06) agreement8 as modified through associated bilateral agreements for Denmark, provided by NITA – the DTT channel plan taken into consideration in this study is therefore the modified version of the original GE-06 plan, taking account of DTT re-planning out of the 800 MHz sub-band

base station mast data for current 2G and 3G mobile deployments in Denmark, as provided by NITA (March 2011 version)

measured overload threshold (Oth) and protection ratio (PR) values from the ECC Report 148, with selected values consistent with protecting 90% of receivers

DTT wanted field strength maps produced in CRC-Predict and IRT2D, provided by the Danish terrestrial broadcasters (Boxer and Digi-TV).

The analysis conducted using the radio planning tool is based upon the potential for interference due to receiver overload or ACI from LTE base stations. The results from this analysis are presented in Sections 3 and 4.

We have also undertaken a literature review of a number of published reports, as agreed with NITA, which consider the potential for interference from the LTE uplink (i.e. mobile devices) to DTT receivers. It is noted that the ECC band plan provides a 42MHz frequency separation between the upper edge of DTT Channel 60 and the first uplink channel, which is expected to mitigate the majority of interference problems from the uplink channel. The documents we have reviewed, which are further described in Section 6 of this report, are as follows:

CEPT Report 30 – identification of common (and least restrictive) technical conditions for 790–862MHz for the digital dividend in the European Union

8 ITU-R: Final Acts of the Regional Radiocommunications Conference for planning of the digital

terrestrial broadcasting service in parts of Regions 1 and 3, in the frequency bands 174-230MHz and 470–862MHz (RRC-06).

Overview of approach and main assumptions 15


material presented by the European Broadcast Union at various

workshops9

A study conducted in the UK by the government-sponsored Digital

Communications Knowledge Transfer Network10

A contribution from the UK to ECC Task Group 4, on UK measurements

of LTE into DVB-T conducted by Cobham Technical Services.11

2.2 Main assumptions

Our analysis makes various assumptions in relation to DTT and LTE deployment in Denmark, in the absence of any interference mitigation being applied. A summary of the main assumptions is as follows.

DVT-T transmission in Denmark uses two system variants: the multiplexes operated by Digi-TV use a 64-QAM 2/3 code rate, while the multiplexes operated by Boxer use a 64-QAM 3/4 code rate. This leads to differences in DTT planning levels for the two networks, and impacts receiver protection ratios (the minimum carrier-to-interference ratio necessary to avoid performance degradation to DTT viewing as a result of LTE interference, at a given frequency offset). In particular, for our analysis, the different code rates give rise to a 2dB difference in the required protection ratio for Boxer‟s multiplexes compared to Digi-TV,

which we have incorporated into our analysis.

We have assumed from our household dataset that there are a total of 2 359 106 households in Denmark. The number of households receiving DTT on one or more television set is assumed to be 20% of total households in Denmark (i.e. the remaining 80% receive television using alternative platforms). The source of this assumption is Gallup statistics (for end 2010). Results throughout this report for households that could potentially be affected by interference are presented as affected DTT

households, which is 20% of total households in Denmark

The DTT coverage criteria are assumed to be 95% of locations, with a

lognormal field strength standard deviation of 5.5dB.12

We have also assumed that interfering LTE signals are subject to lognormal fading with a standard deviation of 5.5dB, which has been

9 http://tech.ebu.ch/docs/events/ecs10/presentations/ebu_ecs10_workshop_sami.pdf

10 http://docbox.etsi.org/Etsi_Cenelec/PUBLIC%20FOLDER%20on% 20DD/UK%20DKTN%20DD/DCKTN%20Digital%20Dividend%20 Technologies%20Spectrum%2011Jun10%20v11%20(SR).pdf

11 ECC TG4(10)317, UK measurements of LTE into DTT, presented to the 15th meeting of ECC

TG4.

12 Location probability is the probability that within a given (small) area a field strength level is exceeded at a required percentage of points – see ITU-R JTG 5/6 Methodology for sharing studies between the mobile and terrestrial broadcasting service in the band 790–862 MHz, Section 3.1.1.1.



reflected in the link budgets used for the overload and ACI thresholds

within our planning tool.

We have modelled the actual antenna polarisation and patterns for DTT, which are taken from the GE-06 agreement and plan data for Denmark,

as modified by NITA to account for cross-border coordination agreements.

We have assumed fixed outdoor (rooftop) reception for DTT throughout the majority of our analysis, but have compared the effects of reception to portable coverage within a selected area of Denmark, as described in

Section 3.

We have assumed that LTE antennas will use slant polarisation (i.e. employing two sets of antennas slanted at ±45 degrees to the horizontal plane), providing 3dB discrimination against horizontal/vertical polarised DTT signals. However, we have also separately considered the impact of using vertically polarised antennas for LTE as a means of comparison with the use of slant antennas, and as a possible means of improving

interference mitigation.

For field strength predictions, a height and clutter database with 50 metre resolution has been used. This is not always sufficient to detect very small

coverage gaps, which is noted as a limitation of our analysis.

For our initial analysis using maximum licensed EIRP limits, we first calculated theoretical LTE cell radii necessary to provide a downlink data rate of 8Mbit/s using a link budget (for details see Annex D). We then used these theoretical cell radii values to develop a theoretical LTE network providing coverage across Denmark, based upon using the base station locations of an existing GSM network in Denmark as the basis of the network, but adding additional cell sites where required to achieve the calculated cell radii for LTE. We then assumed that all sites would transmit at their maximum licensed power level of 59dBm EIRP (or 56dBm EIRP in areas where DTT Channel 60 is used), irrespective of the

actual power level required at the site from the link budget.

For our subsequent analysis using individually determined EIRP levels per base station, we used the same link budget to develop a theoretical relationship between the required EIRP of a site and the separation between the site and its nearest neighbour (assuming sites are located in line with the existing GSM900 networks currently operating in Denmark). We then applied these individual EIRP levels within the base stations of three networks, modelled on different GSM900 networks in Denmark, referred to as Network A, Network B and Network C. Each of the three networks modelled therefore exhibits different site densities and EIRP per site.

Protection ratios for DTT interfered with by mobile services are based upon interpolated values obtained from ECC Report 148.



2.3 DTT coverage and frequency plan

2.3.1 DTT coverage

Frequencies for DTT services have been planned within Europe and across ITU Region 1 via the GE-06 agreement and plan. The Final Acts of GE-06 contain DTT planning parameters assumed within the agreement, along with the detailed methodology for coordination of DTT networks between neighbouring countries. GE-06 describes three reception modes for DTT:

fixed reception – where a rooftop-mounted directional receiving antenna is used

portable reception – where a portable receiver with an attached or built-in antenna is used, either outdoors or indoors

mobile reception – where reception is via a receiver in motion.

The different reception modes affect the height and gain of the receiver assumed when calculating the field strength for acceptable reception. For fixed reception, a 10 metre height (above ground level) is assumed, whereas for portable and mobile, a 1.5 metre height is assumed.

Standard radiation patterns for fixed receiving antennas are provided in

Recommendation ITU-R BT.419.13 For portable and mobile reception it is usually assumed that an omnidirectional antenna is used.

Within our analysis, we have assumed DTT fixed reception throughout the majority of our analysis, with antenna characteristics according to ITU-R BT.419, as illustrated below.

13 Recommendation ITU-R BT.419-3: Directivity and polarisation discrimination of antennas in

the reception of television broadcasting.



Figure 3 DTT directional receiving antenna [Source: ITU-R BT.419]

In the current Danish DTT coverage plan, coverage is defined to exist when 95% of locations within a 50x50 metre pixel receive field strength above a specified threshold. The minimum field strength is taken to be 47dBµV/m for the 64-QAM,

2/3 coded mode of DTT in channel 60, in line with the GE-06 agreement. In accordance with the JTG 5/6 methodology, in order that an area can be considered as covered, the wanted field strength must exceed the minimum field strength at 95% of the locations within the area. An uplift of 9dB is therefore added to the minimum value, to correspond to the reception of an un-interfered DTT signal at 95% of locations, giving a minimum median field strength in the

pixel of 56dBµV/m for 2/3 coded transmission, and 58dBµV/m for 3/4 coded.14

Danish DTT networks are planned on the basis of 15 broadcast regions, and we have used these regions within our analysis to enable calculation of households covered with, and without, interference, per region. The 15 regions are illustrated in Figure 4 below.

14 Section 5.3.2.2 of the JTG methodology



Figure 4 Danish broadcast regions [Source: NITA]

2.3.2 Frequency plan

In line with many other European countries, the DTT deployment in Denmark uses a multi-frequency network, which means that many households do not use the upper DTT channels (i.e. 58, 59 and 60), which are particularly susceptible to ACI. It is noted that receiver blocking can occur irrespective of frequency offset, and so all households in Denmark could theoretically be affected by that.

The frequency plan for DTT in Denmark is based on five multiplexes, with a sixth reserved for mobile television (using DVB-H technology). DTT services are provided by two broadcast companies – Digi-TV (DR and TV2) and Boxer. The frequency plan for multiplexes 1–6 is summarised below.



Area name MUX 1 MUX 2 MUX 3 MUX 4 MUX 5 MUX 6

Tolne-Nibe 29 57 50 37 35 39

Thisted 31 42 22 43 21 49

Videbaek 40 59 52 48 34 28

Viborg 40 59 52 56 21 45

Hadsten + Aarhus 26 44 24 56 55 36

Hedensted 30 44 33 46 55 36

Varde 30 54 33 46 53 28

Aabenraa 37 50 32 22 49 41

Tommerup + Svendborg 25 43 27 22 49 41

Vordingborg + Nakskov 58 34 42 38 60 48

Jyderup 58 51 42 31 60 23

København 53 51 54 31 59 23

Rø 59 56 51 39 31 32

Table 1 Channel plan for DTT multiplexes 1 to 6 [Source: NITA]

From the table above it can be identified that the following regions in Denmark use the upper DTT channels, which are the most susceptible to ACI.

DTT channel Regions affected

60 (782-790MHz) Vordingborg + Nakskov, Jyderup

59 (774-782MHz København, Rø, Videbæk, Viborg

58 (766-774MHz) Vordingborg + Nakskov, Jyderup

Table 2 Regions in Denmark using upper DTT channels [Source: Analysys Mason]

The regions in Denmark that uses the upper DTT channels are shown in Figure 5 to Figure 7 below.



Legend

CH60 coverage region

Other regions

Figure 5 Regions using Channel 60 [Source: NITA]

Legend


Other regions




Legend


Other regions


Digi-TV operates services using Channels 58 and 59 in Vordingborg + Nakskov, Jyderup and Rø. Boxer operates services using Channels 59 and 60 in København, Vordingborg + Nakskov, and Jyderup. Since the Digi-TV and Boxer networks use different DTT configurations (3/4 coding and 2/3 coding respectively), we have modified our analysis of ACI for the affected channels to reflect the difference in planning and protection parameters (minimum received signal strength and PR) resulting from the different coding rates. Also, since the coverage areas of Channels 58 and 60 overlap, we have not conducted specific analysis within the study on Channel 58 areas.



2.3.3 Characteristics of DTT transmitters and receivers

A summary of other parameters used in our analysis is provided below.

Value Assumption and source

Modulation and coding 64-QAM, 2/3 coding (MUX 1 and 2) and 3/4 coding (MUX

3, 4 and 5) (Source: NITA)

DTT channel bandwidth 8MHz (Source: ITU-R GE-06)

Minimum field strength for fixed

outdoor reception (DTT Channel 60)

47dBµV/m (Source: ITU-R Recommendation1368-8)

Location probability 95% (leading to an operating field strength of 56dBµV/m,

including 9dB uplift to account for 95% location probability

as indicated by ITU-R15)

Receiving antenna gain 12dBd (Source: ITU-R GE-06), with antenna pattern as

illustrated in Figure 3.

Receiver feeder loss 5dB (Source: ITU-R GE-06)

Directivity discrimination 3dB (between slant polarised LTE antennas and

horizontal/vertical DTT – source JTG5/6 methodology for

sharing studies between the mobile service and DTT,

section 4.2.2.4)

Wanted and unwanted signal

standard deviation

5.5dB – giving a combined location correction factor of

12.8dB

Building penetration loss 8dB with a 5.5dB standard deviation

Table 3 DTT planning assumptions [Source: Analysys Mason]

2.3.4 DTT protection ratios and overload threshold

Two of the key parameters used within our analysis are the protection ratio (PR) between the DTT and the LTE signal, and the DTT overload threshold. We discuss each of these below.

DTT PR values – fixed outdoor reception

Protection ratio refers to the ratio (in dB) of the power of the wanted signal to the total power of interfering signals, usually expressed at the receiver input. PRs for a DTT signal interfered with by another DTT signal are well understood, and are specified in various ITU-R recommendations, and also in the GE-06 Final Acts. For the purposes of this analysis, however, PRs for a DTT signal interfered with by an LTE signal are required. This has been the subject of recent study within the CEPT and the ITU-R, and studies within the CEPT have led to ECC Report 148 being published in 2010, detailing measurements on the performance of

15 For example, in ITU-R JTG 5/6: Methodology for sharing studies between the mobile service,

on the one hand, and the terrestrial broadcasting service, on the other hand, in the band 790–862MHz.



DVB-T receivers in the presence of interference from the mobile service. The report provides the combined results of measurements conducted in a number of European countries, for a range of DTT receiver types and models. Table 5.1 of Report 148 provides the following PR values for a 64-QAM, 2/3 coded DTT

signal16, for the stated frequency offsets.

Channel edge separation DVB-T protection ratio (dB)

1 -33

9 -40

17 -44

25 -48

33 -49

41 -50

49 -50

57 -51

65 -45

Table 4 DVB-T PRs in the presence of LTE interfering in a Gaussian channel environment [Source: ECC]

The PRs quoted above are presented for a 64-QAM, 2/3 coded signal at the stated channel edge separation (e.g. from the edge of the 790–862MHz band in 8MHz offsets). In order to obtain PRs suitable for our analysis, we have interpolated the values above to reflect the frequency offsets of interest to this study, which are detailed below. We have also applied a number of correction factors, as detailed in the ECC report and other sources, as shown in the following tables.

LTE/DTT

channel

DTT 58 DTT 59 DTT 60

FDD1 17 9 1

FDD2 22 14 6

FDD3 27 19 11

FDD4 32 24 16

FDD5 37 29 21

FDD6 42 34 26

Table 5 LTE-DTT channel offsets in MHz used in the ACI analysis [Source: Analysys Mason]

16 90 percentile values are quoted in Figure 3.4, and for silicon tuners, although ECC Report 148

also presents results for 10 and 50%, with the percentage referring to receivers measured, i.e. the 90 percentile values should be used to protect 90% of receivers measured, and also for can and silicon USB tuners.



Factor Value/source

Correction for fixed reception conditions

(Ricean channel) relative to Gaussian channel

(for 2/3 coding)

1.1 dB

Correction for fixed reception conditions

(Ricean channel) relative to Gaussian channel

(for 3/4 coding)

2.8 dB

Location correction factor 12.8dB

Table 6 Correction factors applied to PR values [Source: Analysys Mason]

Interpolation of the PR values given in Table 4 above provides the PRs calculated for LTE Channels FDD1, 2 and 3, with respect to DTT Channels 58, 59 and 60, as follows.

DTT/LTE channel FDD1 FDD2 FDD3

60 -33 -37 -41

59 -40 -43 -45

58 -44 -47 -48

Table 7 Interpolated PR values – Gaussian channel [Source: Analysys Mason]

Within our planning tool, we have then applied the various correction factors described in Table 6 to the PR values above, to account for alternative DTT coding, reception conditions and locations margin. This gives the following input values to our planning tool (see Table 8 and Table 9 below), using the PR values above in combination with the various correction factors. There are two different sets of inputs to reflect analysis for the Digi-TV and Boxer DTT coverage areas, respectively.



Frequency offset Interpolated PR from

ECC Report 148

Plus location

correction factor

Plus 2.8 dB correction for 3/4

coding and fixed reception (Ricean

channel)

1 -33 -20 -17

6 -37 -25 -21

9 -40 -27 -24

11 -41 -28 -25

14 -43 -30 -27

16 -44 -31 -28

17 -44 -31 -28

19 -45 -32 -29

21 -46 -33 -30

24 -48 -35 -31

25 -48 -35 -32

27 -48 -35 -32

29 -49 -36 -33

Table 8 Interpolated ratios with correction factors – Boxer DTT coverage [Source: Analysys Mason]

Frequency

offset

Interpolated PR from

ECC Report 148

Plus location correction

factor

Plus 1.1 dB correction for

fixed reception (Ricean

channel)

1 -33 -20 -19

6 -37 -24 -23

9 -40 -27 -26

11 -41 -28 -27

14 -43 -30 -29

16 -44 -31 -30

17 -44 -31 -30

19 -45 -32 -31

21 -46 -33 -32

24 -48 -34 -33

25 -48 -35 -34

27 -48 -35 -34

29 -49 -36 -35

Table 9 Interpolated ratios with correction factors – Digi-TV DTT coverage [Source: Analysys Mason]

This gives the following PR inputs to our planning tool for the various frequency offsets of interest to the study (incorporating correction factors).




60 -17 -21 -25

59 -24 -27 -29

58 -28 -30 -32

Table 10 PR values plus correction factors, Boxer coverage – fixed outdoor reception [Source: Analysys Mason]


60 -19 -23 -27

59 -26 -29 -31

58 -30 -33 -34

Table 11 PR values plus correction factors, Digi-TV coverage – fixed outdoor reception [Source: Analysys Mason]

This means that, in our planning tool, the median field strength predicted from LTE FDD1 must be a maximum of 17dB above the median wanted (DTT) signal in Channel 60 for the Boxer coverage, to avoid interference.

DTT overload threshold

Receiver blocking or overload refers to the effect of a strong out-of-band interfering signal on the receiver‟s ability to detect a low-level wanted signal. The DTT overload threshold (Oth) is defined in ECC Report 148 as “the interfering signal level expressed in dBm, above which the receiver begins to lose its ability to discriminate against interfering signals at frequencies differing from that of the wanted signal, i.e. the onset of non-linear behaviour”.

ECC Report 148 describes the measured Oth for various DTT receivers, suggesting that overload typically occurs at a level of LTE interference of between -15dBm and -5dBm.17 For our analysis, we have selected a value at the lower end of this scale, and we have used an overload threshold of -15dBm throughout our modelling. This therefore represents a conservative assumption, and it should be noted that most TV receivers and set top boxes will perform

better than this18. Our analysis can therefore be considered to represent a worst case in terms of possible TV receiver performance.

2.4 LTE network assumptions

To simulate an LTE network in our analysis, we have needed to make assumptions on the number and location of base stations within a typical LTE network.

17 This is the typical range – the full range of measurements described in ECC Report 148 range

from 03dBm to -26dBm.

18 According to ECC Report 148 the -15dBm value corresponds to the value at which the 10% worst performing receivers overload.



The following parameters have been assumed:

LTE base stations transmit in the 791-821 MHz band

Channel bandwidth is 5 MHz

Location probability is 75% at the cell edge

Receiver height is 1.5 metres

Base station maximum licensed in-band EIRP is 59 dBm/5MHz (reduced to 56dBm/5 MHz for the lower most LTE BS channel on islands of

Sjaelland and Lolland-Falster, where DTT Channel 60 is used)

Base station antenna gain is 15dBi

Tri-sectored cells are assumed

Propagation model used for predicting LTE coverage is ITU-R P.1812

It is noted that mobile networks can deploy a hierarchy of macro, micro and pico-cells, with micro and pico cell base stations typically operating at reduced power and height. We have not incorporated micro and pico-cells into our analysis but have instead focussed on macro cells.

Throughout our analysis we have assumed an antenna height of 30 metres being applicable to macro-cell base stations, and have assumed a Jaybeam B800A085 antenna, as illustrated in Figure 8 below.

Figure 8 Jaybeam antenna pattern [Source: Jaybeam, Analysys Mason]

To calculate the theoretical cell radii of LTE base stations within a typical network, we have used a link budget (see 0). The link budget has been derived to achieve an 8Mbit/s downlink service in different outdoor coverage environments (urban, suburban and rural). We have assumed a 75% cell edge probability when deriving the cell radii for LTE, which is consistent with typical assumptions made



by the cellular industry when developing link budgets.19 The resulting cell radii calculated from the link budget and used in our model are listed below.

Geo-type Cell radius (km)

Urban 2.1

Suburban 3.6

Rural 5.8

Table 12 Cell radii for LTE model [Source: Analysys Mason]

These cell radii have been calculated as being representative of cell radii needed to achieve an LTE 800MHz coverage layer. In practice, it is assumed that operators will also deploy LTE at 1800MHz, 2100MHz and/or 2600MHz to meet capacity requirements. Therefore, the above cell radii do not take into account the level of traffic to be delivered within a network, but are designed primarily to achieve coverage.

In our initial analysis using maximum licensed EIRP levels, we have modelled an LTE network using base station locations based upon an existing GSM900 network in Denmark, but have added additional sites, where required, to provide a network of the required dimensions to achieve the cell radius above, consistent with requirements for a network achieving around 98% population coverage at a downlink data speed of 8 Mbit/s. In this initial analysis, the actual power level required at each base station site relative to neighbouring sites has not been accounted for.

In our subsequent analysis, we modified our approach to individually vary the EIRP of base stations as necessary, relative to neighbouring sites. In this case, we have again used the existing base station locations of GSM900 networks in Denmark as the basis of LTE site locations, but have modified the EIRP per site based upon its geo-type (urban, suburban or rural) and distance with respect to its nearest neighbouring site. This subsequent analysis has focussed on one area of Denmark in particular, to the north of Copenhagen; this area uses DTT Channel 59.

19 For example, see WCDMA for UMTS: HSPA Evolution and LTE, Holma and Toskala, 2010

30 Analysis of LTE networks operating at maximum power levels



The first part of the analysis considered the potential interference mechanisms into DTT that might occur from LTE networks operating at maximum licensed power levels, and the extent of interference potentially created under that assumption. The purpose of this first high-level analysis was to establish the extent to which interference from LTE to DTT could be a problem, and to assess the main characteristics of both LTE and DTT networks that influence the extent of interference.

In practice we expect that the majority of LTE base stations, particularly those in urban areas, will use a lower power level than the maximum allowed limit, for various practical reasons. In the section, we consider the impact of this in more detail, by predicting interference effects caused by receiver overload and ACI under the assumption that individual power levels at LTE base stations might be varied depending on the location of the base station and its proximity to neighbouring sites. In this section, interference is modelled assuming that all base stations transmit at their maximum licenced transmit power (EIRP) level.

3.1 Summary of results

Our initial modelling using maximum licensed EIRP levels per base station site has considered two interference mechanisms from LTE to DTT, namely blocking and ACI. Overall, our analysis suggests that the dominant interference issue affecting DTT households in this case could be blocking, rather than ACI. A summary of our results is provided below.

3.1.1 DTT receiver overload

Our initial modelling suggests that around 54 000 of DTT households could be affected by receiver overload in Denmark from a single LTE network, assuming an LTE base station EIRP of 59dBm in most areas (and 56dBm in Channel 60 areas). The network modelled consisted of a total of 1445 macro base stations, distributed between urban, suburban and rural areas. The number of households predicted to be affected by receiver overload corresponds to around 2.3% of the total households in Denmark, and 3.4% of the total country area could be affected.

Our results suggest receiver overload could potentially affect a proportion of households in almost all urban areas of Denmark. This is due to the higher density of base stations in urban compared to suburban or rural areas and the fact that in areas where there are mixed geo-types, the highest number of affected households are in urban areas. For example, within the København broadcast region, 72% of affected households are in geo-types we have defined

in our model as urban20.

20 The geotypes in our initial analysis are defined based on municipal areas in Denmark and

population density.

Analysis of LTE networks operating at maximum power levels 31


A full breakdown of results is presented in Table 13 below. A map showing the areas of interference is included in Annex C.

Broadcast region Total area

(km2)

Total

households in

area

Affected area

(km2)

Affected DTT

households

Anholt 21 588 1.1 0

Laeso 117 3526 8 37

Tolne-Nibe 6140 266 939 166 5 777

Viborg 2599 85 044 68 1 348

Thisted 1529 44 170 28 977

Videbaek 5094 150 321 106 2 573

Hadsten + Aarhus 4507 279 245 195 7 490

Hedensted 3060 163 648 102 3 462

Varde 2684 99 804 70 1 930

Aabenraa 3810 124 076 96 1 911

Tommerup + Svendborg 3473 231 985 148 4 797

København 2844 551 716 233 16 549

Vordingborg + Nakskov 3339 151699 180 3 178

Røe 585 27 820 32 892

Jyderup 2956 178 525 99 3 125

Table 13 Summarised results of blocking calculation from LTE to DTT, initial analysis (59dBm EIRP, with 56dBm in Channel 60 areas) – fixed outdoor reception [Source: Analysys Mason]

We have repeated this analysis for one area of Denmark assuming three LTE networks operate in the same area, to illustrate the increase in blocking compared to a single network. We have chosen to model three networks since it is likely that there will be three 800MHz licence winners in Denmark, as has been the case in other European countries where 800MHz frequencies have been auctioned. The area selected is to the north of Copenhagen; it was chosen because it contains predominately urban areas. The number of base station sites within each of the three networks within the area of our analysis is shown below. As before, we assume that each base station operates at its maximum licensed EIRP of 59dBm (or 56dBm where Channel 60 is used).

We have assumed that three LTE networks operate within the selected area, which we refer to in our analysis as Networks A, B and C. Base station locations within each network are based upon existing 900MHz base station locations in

Denmark21.

21 We have manually modified coverage in some areas to reflect a target coverage of 98% population within the area.



Operator Number of sites

Network A 74

Network B 128

Network C 129

Table 14 Number of existing GSM900 sites of each operator in the area of analysis [Source: Analysys Mason]

In terms of the impact of three networks operating in the same area, we have found that the number of households potentially affected by receiver overload could increase from around 5 900 for one network, to 16 000 DTT households if three networks are operating in the same area. This equates to just over half (52%) of all households within the area at risk of blocking from at least one of the LTE networks.

It can be seen that many of the areas affected by blocking from the three separate networks overlap, as shown in Figure 9 below.

Figure 9 Areas of blocking from the three LTE networks [Source: Analysys Mason]

Of the households affected, we have found that the majority (88%) of these in the area considered are located in urban areas. This is in line with expectations that the risk of blocking is likely to be higher in areas where there is a high concentration of LTE sites, which normally occurs in highly populated areas.

The results demonstrate the following.

Having three LTE networks within the area increases blocking by almost three (2.8) times the amount caused by a single network. Given our initial result that one network operating at maximum licensed power levels could



cause receiver overload to around 54 000 households nationally, this could scale to around 150 000 DTT households if three national networks operating at maximum licensed power levels were deployed in the 800MHz band.

The majority of blocking is predicted to occur in areas where there is a high concentration of LTE base stations – typically in urban areas. This suggests the highest risk of blocking to DTT services will be in urban areas, which concurs with the results for a single LTE network.

The high incidence of receiver overload is due to the assumption that all base stations will transmit at their maximum licensed EIRP level, whereas in practice it is likely that operators will choose to use lower EIRP at some base stations depending on the environment (urban, suburban or rural) and density of base stations deployed. Our subsequent analysis, described in the section 4, therefore explores this effect in more detail.

3.1.2 Adjacent Channel Interference (ACI)

Our initial analysis suggests that ACI is predicted to affect less households than receiver overload (when assuming that LTE network operate at maximum licensed power levels). Households affected are limited to those located in areas where DTT services using Channels 60, 59 and 58 are operating. We found that around 5 600 DTT households in Channel 60 areas could potentially experience interference from LTE services using the closest channel (FDD1). This number reduces to around 4 800 DTT households affected by ACI from FDD2, and around 1 400 DTT households from FDD3. FDD2 and FDD3 produce less interference because of the increased frequency separation between FDD2 and FDD3 and the DTT channel(s), compared to FDD1.

We also found that around 4 800 households might be affected by ACI from the closest channel (FDD1) within channel 59 areas.

Areas of interference from ACI from one LTE network using Channel FDD1 are illustrated in Annex C.

We have also considered the cumulative effect of ACI from multiple LTE networks using different channels within the 800MHz band, to DTT areas using Channels 60, 59 and 58. This shows that the lowermost LTE block (FDD1) contributes the most significant cumulative ACI into adjacent DTT channels. Blocks FDD2 and FDD3 interfere with a sub-set of households affected by ACI from FDD1. Channel 60, which is only used by Boxer in Denmark, is most affected by ACI.

Whereas our analysis suggests that around 5 600 DTT households could be affected by ACI from a single LTE network within Channel 60 areas, the analysis also suggests that the cumulative number of households affected by ACI from two LTE networks (one using Channels FDD1 and FDD2, and the second using



Channels FDD3 and FDD4) could be up to 7 800 DTT households. We estimate that around 1 000 of these might receive interference from both networks22.

This is illustrated in Figure 3.2, where the blue areas represent ACI caused by the network using FDD1/FDD2 and the yellow areas represent ACI caused by the network using FDD3/FDD4.

Figure 10 Areas affected by ACI into DTT channel 60 from two LTE networks [Source: Analysys Mason]

It is noted that a large proportion of households suffering ACI will also suffer from receiver overload, since the areas affected by ACI overlap with the areas affected by receiver overload, as described above. Our analysis suggests that, of the 5 600 DTT households in Channel 60 areas who are affected by ACI from LTE block FDD1, around 3 800 might also suffer receiver overload.

Overload is also potentially the more severe of the two modes of interference because, in the presence of receiver overload, reception of all DTT services is lost, whereas with ACI the interference affects reception of services using particular DTT MUXs (in particular, those broadcast using Channel 60 and Channel 59).

22

The sum of the households affected by ACI from FDD1/FDD2 and FDD3/FDD4 is 42 905, compared to the cumulative number of households of 37 947, equating to a difference of 4958.



3.2 Effect of interference on indoor coverage of DTT

To illustrate the effect of LTE interference on indoor DTT reception23, we have repeated our ACI analysis for the Vordingborg area only. For this, we have applied the height-gain correction factor of 18dB, as provided in ITU-R GE-06. We have also assumed an omnidirectional antenna with a gain of 0dBi. For portable reception indoors, a building penetration loss is also required – we have used a value of 8dB, with a standard deviation of 5.5dB. No feeder loss has been included.

Within the Vordingborg area, DTT coverage is provided using Channel 60. The total area is around 1000km2, and the total number of households in the area is 45 600.

The results of our analysis into the effects of ACI on indoor reception are summarised below (these number represent the potential maximum total households in the area rather than the proportion of households receiving television using DTT).

LTE channel Number of DTT

households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

FDD1 253 2.8% 6 0.6%

FDD2 120 1.3% 3 0.3%

FDD3 55 0.6% 1 0.1%

Table 15 ACI to Channel 60 in Vordingborg, portable indoor reception [Source: Analysys Mason]

Our initial analysis suggests that, for fixed rooftop reception 4.0% of households using Channel 60 are potentially interfered from LTE Channel FDD1 within the Vordingborg sample area, with the affected area being 0.9% of the total area modelled. For portable indoor reception the potentially interfered households reduces to 2.8% of DTT households, with the affected area being 0.6%. This difference is potentially due to the lower height of the receiving antenna for portable receivers compared to fixed reception, and the fact that penetration of signals within buildings provides some mitigation from interference.

3.3 Conclusions from the initial analysis

Our initial analysis, assuming that each base station within an LTE network transmits at its maximum licensed power, concludes that

Blocking could affect 11.5% of DTT viewing households, equating to a total of around 54 000 DTT households, based on an assumed LTE EIRP of 59dBm (or 56dBm in Channel 60 areas). This mainly affects

23 i.e. where DTT services are not received via a fixed outdoor antenna but use a portable antenna located inside the building



households in urban areas – for example, within the København broadcast region, 72% of affected households are in geotypes we have

defined as urban.24

The effect of having three LTE networks operating within the area increases blocking by almost three (2.8) times the amount caused by a single network. This could scale to around 150 000 DTT households nationally, if three national networks operating at maximum licensed power levels were deployed in the 800MHz band.

ACI from a single LTE network using Channel FDD1 could affect up to around 5 600 DTT households in Channel 60 viewing areas. For two LTE networks (one using Channels FDD1 and FDD2, and the second using FDD3 and FDD4) the cumulative number of households affected by ACI within Channel 60 areas rises to 7 600 DTT households. Some 1 000 DTT households could receive interference from both networks.

We have also considered the impact of ACI on indoor reception in the Vordingborg city area, for households covered using Channel 60. Our analysis suggests that 4% of households using fixed rooftop reception could experience ACI from LTE Channel FDD1. The affected area is 0.9% of the total area modelled. For portable indoor reception, the proportion of affected households reduces to 2.8% (affected area 0.6% of the total). This may be due to the lower height of the receiving antenna for portable receivers compared to fixed reception, and the fact that penetration of signals within buildings provides mitigation from interference.

Blocking is predicted to be the more significant of the two interference modes using our initial assumptions on LTE base station EIRP. ACI has a more localised effect, occurring only in areas where Channel 60 and Channel 59 are used, and where the DTT field strength is also low. Typically, DTT field strength is low where households are located at the edge of DTT coverage and so receive a weak TV signal compared to households with a better signal path to the DTT transmitter.

A large proportion of households suffering ACI will also suffer blocking, since the areas affected by ACI overlap with those affected by blocking. Of the 5 600 DTT households in Channel 60 areas who are affected by ACI from LTE block FDD1, around 3 800 might also be subject to receiver overload. Overload is potentially the more severe of the two modes of interference because it leads to the loss of reception of all DTT services, whereas with ACI affects reception of services using particular DTT MUXs (in particular, those using Channels 60 and 59).

The potential for blocking to occur is not frequency dependent25 (i.e. it could occur from any FDD block to any DTT channel, regardless of

24 The geotypes are defined based on municipal areas in Denmark and population density.



frequency), and is sensitive to the distance between the LTE base station and the household, primarily as a result of the design of DTT receivers and their overload threshold.

3.4 Observations on relevance of the initial analysis to real LTE deployments

Of particular relevance to the initial analysis is the assumption that a uniform EIRP, equivalent to the maximum licensed EIRP level, is deployed across the entire LTE network: that is, all sites transmit at the same power and with a similar height of antenna – with the exception of base stations in Channel 60 areas, where we have assumed a slightly lower EIRP.

As described earlier in this section, our assumption has been that LTE800 will be deployed by mobile operators using existing 900 MHz sites where practical. It is noted that the density of 900 MHz sites deployed in some areas of Denmark will lead to significant overlapping coverage between neighbouring sites if all sites are assumed to transmit at the maximum licensed power level of 59 dBm.

As an illustration of this, the figure below illustrates the substantial coverage overlap that could occur if it is assumed that LTE800 is deployed on all GSM900 sites within a 2G network in Denmark with an EIRP of 59 dBm at all sites.

25 Although blocking is generally not frequency dependent, measurements of overload threshold (Oth) of different DTT receivers presented in ECC Report 148 indicate some dependency between the measured Oth and the frequency offset between the LTE and the DTT signal. Specifically, measurements suggest a variation in the Oth when the TV receiver is tuned to a channel at a frequency offset of 33MHz or less (which corresponds to the offset between LTE block FDD1 and DTT channels 56-60), compared to the Oth when the receiver is tuned to a lower channel (i.e. 21 to 55).



Areas covered by

more than 1 site

All sites with EiRP of 59dBm

Figure 11 Illustration of areas of coverage overlap in one LTE800 network deployed on GSM900 sites [Source: Analysys Mason]

In practice, we expect that operators will deploy base stations with a lower EIRP than 59 dBm in different parts of their network. This will be done in order to avoid significant coverage overlap between to sites (which would lead to increased interference within the network) as well as to comply with specific planning restrictions in some areas, which can affect the installation of base stations (e.g. due to height or antenna size restrictions), leading to lower EIRP levels being radiated. In particular, site availability and planning differences between urban, suburban and rural areas will mean that EIRP levels will vary in different parts of the network, with significantly lower EIRP levels typically being used in urban areas compared to the most rural sites, for example.

Since the assumption in our initial analysis that all LTE sites will transmit at maximum licensed levels is unlikely to reflect how LTE networks will be deployed in practice, the next section of this report considers the impact of assuming more realistic EIRP levels being used within an LTE network, and how this affects interference to DTT.

We have conducted this subsequent analysis focussed on two sample areas of Denmark (one to the north of Copenhagen and one in the Ringsted-Sorø area), where we have varied the EIRP per individual base station site in line with a more practical network deployment.

Our approach and results to this analysis are described in the section 4.

Impact of interference assuming realistic LTE deployment assumptions 39


4 Impact of interference assuming realistic LTE deployment assumptions

Our first high-level analysis as described in the previous section assumed a uniform EIRP level is used across all sites in an LTE network, and also assumed that the maximum licensed EIRP level would be used at all sites. In practice, since mobile operators will use different EIRPs levels at different sites to manage interference within their networks, and in response to site planning restrictions in some areas, the initial analysis does not reflect how a real LTE network might be deployed in practice

This section therefore describes further analysis to consider the effects of more realistic assumptions being taken on LTE base station transmitted power levels.

The effect of altering EIRP at selected sites is discussed in more detail in this section, and the corresponding impact on the potential for receiver overload and ACI to DTT assessed.

4.1 Determination of individual EIRP levels

Mobile operators use a number of techniques to optimise the field strength transmitted from individual base stations, including varying the output power from the base station, use of antenna down-tilt, use of sectored antennas and, for LTE, use of MIMO (Multiple In, Multiple Out) antennas. Also, in WCDMA and in LTE networks, power control is used to optimise the power of individual links between the network and a device. The combination of these factors leads to variation in the transmitted power from individual base stations within a network, depending on the base station location, its distance from the nearest neighbouring site, and the characteristics of the traffic load.

For this analysis, we firstly selected a sample to the north of Copenhagen, which we have divided into urban, suburban and rural geo-types based upon the clutter

data used within our planning tool, as illustrated below26.

26 The morphology (clutter) data set for our planning tool includes urban, suburban and rural areas, shown as red, yellow and white in the diagram, as well as forest, shown as green. For our analysis we have incorporated forest areas into our rural geo-type. Our morphology data set also includes water and sea categories, which we did not use in our analysis.



Figure 12 Selected area for analysis [Source: Analysys Mason]

Figure 13 below illustrates the methodology we have used to determine the EIRP at individual base station sites within several LTE networks operating in the same area.

Derive required

site separation

from cell range

Calculate cell

range for different

EIRP

Modify EIRP curves

based on planning

tool

Verify EIRP-site

separation curves

using planning tool

Assign sites in

LTE networks to

geo-types

Produce final

coverage plot per

network

Assign EIRP per

site based on

site separation

Re-run overload

and ACI effects

Figure 13 Approach to setting EIRP per base station site [Source: Analysys Mason]

We first calculated theoretical cell ranges for a range of EIRP levels between 30 and 60dBm using the link budget listed in Annex D, which assumes an Okumura-Hata propagation model. This gave the following theoretical cell ranges for different geo-types, for a range of EIRP levels from 30 to 60dBm (see Table 16).



EIRP

(dBm)

Cell range – urban

(km)

Cell range – suburban

(km)

Cell range – rural

(km)

30 0.40 0.69 2.28

35 0.55 0.95 3.16

40 0.76 1.32 4.38

45 1.06 1.83 6.07

50 1.46 2.53 8.42

55 1.55 2.69 8.94

60 1.55 2.69 8.94

Table 16 Calculated cell ranges for different EIRP levels [Source:

Analysys Mason]27

We then calculated the theoretical site separation required between base stations for the given EIRP range (assuming some overlap in coverage for handover, as is usual in practice), as shown in Table 17Error! Reference source not found..

EIRP

(dBm)

Theoretical site

separation – urban

(km)

Theoretical site

separation – suburban

(km)

Theoretical site

separation – rural

(km)

30 0.69 1.20 3.95

35 0.95 1.65 5.48

40 1.32 2.29 7.57

45 1.84 3.17 10.52

50 2.53 4.38 14.59

55 2.69 4.66 15.49

60 2.69 4.66 15.49

Table 17 Theoretical site separation for different EIRP levels [Source: Analysys Mason]27

Verifying the theoretical distances using the planning tool, we found the rural EIRP levels to be lower than required for the range of separation distances of interest to our analysis. We therefore adjusted the rural curve by adding 10dB to the EIRP, giving the following relationship between site separation and EIRP for urban, suburban and rural geo-types (see Figure 14).

27 The link budget becomes uplink-limited at around 51dBm, and so cell ranges do not change above this level.



0

1

2

3

4

5

6

7

8

25 30 35 40 45 50 55 60

Sit

e s

ep

ara

tio

n (

km

)

BS EIRP (dBm)

Urban Suburban Rural

Figure 14 EIRP required for different site separations [Source: Analysys

Mason]

Using the existing GSM900 site locations within Denmark, we identified the number of base stations within the North Copenhagen sample area for our analysis, for each of the three existing GSM900 networks. This provided the following base station numbers for three networks within the sample area (Table 18).

Network ID Number of base stations

Network A 55

Network B 129

Network C 128

Table 18 Number of base stations within the North Copenhagen sample area [Source: Analysys Mason]

For each of the three networks based upon the existing GSM900 networks, we mapped the location of the base stations within the sample area, and assigned a geo-type to each site. This is illustrated in the maps below. In each of the following maps, red represents urban areas, yellow sub-urban and white rural. (Note that green and blue areas represent forest, water and sea. We have combined the forest areas into the rural geo-type (white). Water and sea areas are not used.)



Figure 15 Site to geo-type matching – Network A [Source: Analysys Mason]

Figure 16 Site to geo-type matching – Network B [Source: Analysys Mason]



Figure 17 Site to geo-type matching – Network C [Source: Analysys Mason]

This resulted in the following number of sites per network for each geo-type:


Network A 14 26 14

Network B 26 73 29

Network C 33 76 20

Table 19 Number of sites per geo-type within the North Copenhagen sample area [Source: Analysys Mason]

Finally, based on the site locations within each of the three networks, we calculated the distance from each base station to its nearest neighbour. Using the EIRP-to-site-separation curve illustrated above (Figure 14), we then assigned a unique EIRP to each site, based upon the required EIRP for the calculated site separation.

We then modelled a series of coverage predictions for each network in our planning tool to validate coverage. Coverage was predicted using propagation model ITU-R P.1812, with receiver height at 1.5 metres, and predictions based upon predicting coverage for 50% locations and 50% time within the cell (noting that theoretical cell ranges assume a 75% cell edge probability (i.e. the probability that a mobile device will receive a signal above the specified threshold value, at the edge of a cell).

We also modelled „best server‟ and simultaneous site display predictions to highlight the areas of overlap between sites, which resulted in some manual



adjustment of the assigned EIRP level per site in a number of locations where overlapping areas were calculated to be too large with the assumed EIRP.

The final composite coverage results from each network, along with the assigned EIRPs per site, as predicted in our planning tool, are illustrated in the maps below. It is noted that the resulting population coverage from the three networks is 82% of the population within the North Copenhagen sample area for Network A, and 96% for Network B and Network C. The coverage figures are different for each network because the number and location of the base stations differ. This is in line with expected LTE deployment, since it is noted that different numbers of base stations are employed within existing 900 MHz networks in Denmark.

It is also noted that the percentage coverage is useful in our analysis only to compare the interference effects of the three networks. It is expected that coverage in practice will be better than predicted by our analysis, since in practice the GSM900 networks that we have used as the basis of determining base station locations have base stations just outside the selected North Copenhagen sample area, which have been excluded from our coverage calculation.

Figure 18 EIRP per site and coverage – Network A [Source: Analysys Mason]



Figure 19 EIRP per site and coverage – Network B [Source: Analysys Mason]

Figure 20 EIRP per site and coverage – Network C [Source: Analysys Mason]



It is noted that the assumed planning level for the LTE service is 53 dBµV/m (for a 10 Mbit/s downlink service with 75% probability of reception at the cell edge), and so the diagrams above illustrate different receive signal strength indicators (RSSI) with respect to that planning level: the blue colour represents areas where the planning level is achieved, white areas are those with an RSSI lower than the planning level, and aqua/green areas are where the RSSI is higher than the planning level. Since the LTE link budget used for our analysis calculates cell ranges for an 8Mbit/s LTE (downlink) outdoor service, the blue areas in the diagrams above can be considered to be areas where an 8Mbit/s service (outdoors) will be received. Areas where the 8Mbit/s service will potentially be exceeded are shown as aqua/green.

4.2 Impact of realistic EIRP levels on potential for receiver overload

Once we determined the EIRP level per base station site and the coverage per LTE network, we then followed the same modelling approach as described in Section 3 to estimate the potential impact of interference into DTT from the three LTE networks caused by receiver overload and by ACI.

It should be noted that DTT provider Boxer operates using Channel 59 in Copenhagen and so our analysis of interference within this area uses the DTT coverage maps provided by Boxer as the basis of determining DTT field strength. PR values for the ACI analysis also assume a 64-QAM, 3/4 coded signal (as per Boxer‟s network).The following results summarise the number and percentage of households and area affected by receiver overload for each of the three networks within our North Copenhagen sample area.

For reference, the total number of households within the North Copenhagen sample area is 154 534 (total DTT households is therefore 30 906) and the total area is 586.52 km2.

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network A 111 0.4% 1 0.2%

Network B 51 0.2% 0.5 0.1%

Network C 48 0.2% 0.5 0.1%

Table 20 Receiver overload per network [Source: Analysys Mason]

Maps of the areas affected by blocking from each network are provided below.



Figure 21 Areas affected by receiver overload – Network A [Source:

Analysys Mason]

LTE Site



Figure 22 Areas affected by receiver overload – Network B [Source: Analysys Mason]



Figure 23 Areas affected by receiver overload – Network C [Source: Analysys Mason]

It can be seen from these maps that there is some overlap between the areas in which households are subject to receiver overload from each of the three networks – i.e. some households may be subject to receiver overload from signals of multiple base stations. Our estimate is that, of the total of around 210 households that could be subject to receiver overload, up to 25% of these (i.e. around 50) are in areas receiving overload from more than one network. The total receiving overload from the three networks might be up to around 170. However, this does not take into account the power sum of interference from different LTE base station sources, which could increase this number slightly, and is described in the following section (4.3).

These results highlight the significant reduction in the number of households affected by receiver overload assuming that base stations within LTE networks do not radiate at their maximum licensed limit. Extrapolating the results from our

North Copenhagen sample area to a national level28 shows that between 700

28 We have extrapolated the results from the North Copenhagen sample area to the national area of Denmark by weighting the number of households affected by geo-type within the area, scaled across the country.



and 1600 DTT households could suffer receiver overload per LTE network (see Table 21 below).

As noted in the previous section, the three LTE networks modelled contain different numbers of base stations, and use different base station locations. Our analysis assumes that as the number of base stations deployed within a network increases the EIRP that is necessary per site reduces.

The location of households affected by receiver overload varies between the three networks. For Networks A and C, just over half of the households affected by receiver overload are in suburban geo-types. For Network B, the majority of households affected are in rural geo-types. This suggests a different distribution of affected households compared to our initial analysis using a uniform EIPP level at all sites, which predicted the majority of households affected were in urban areas.

Our results therefore suggest that as the average EIRP within networks reduces, the potential for blocking to DTT also reduces (i.e. this reflects the fact that typically in urban areas, lower EIRP is used per site). Compared to our initial results assuming maximum licensed EIRP at all sites, the results below indicate a 98% reduction in the potential for receiver overload.

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network A 1 600 0.3% 60 0.1%

Network B 833 0.2% 48 0.1%

Network C 689 0.1% 35 0.1%

Table 21 Receiver overload using realistic LTE EIRP levels scaled nationally from the North Copenhagen sample area [Source: Analysys Mason]

The total households affected by overload, calculated by summing the effects of the three networks, is therefore around 3 100 DTT viewing households. This represents a reduction in receiver overload of around 98% compared to our initial estimate calculated assuming three national networks using maximum licensed EIRP levels at each base station site.

4.3 Composite overload effect from three networks

As noted above, our modelling predicts that some areas will receive LTE signals at levels sufficient to cause DTT receiver overload from more than one LTE network. To confirm this effect, we re-ran the analysis described in the previous section using an interference power sum prediction method in the planning tool, in order to more accurately estimate the cumulative effect of having several LTE



networks operating in the same area, compared to the sum of individual

networks29.

The maps presented earlier (Figure 4.17 to Figure 4.19) illustrate that some areas are affected by receiver overload from base stations in more than one LTE network. The earlier analysis suggested that around 210 households in total could suffer receiver overload within the North Copenhagen sample area. However, since there is some overlap between areas, the actual households affected (without an interference power sum calculation) is around 162 in total. Comparing this with a calculation using an interference power sum, we found that the number of households is very similar, around 164. The difference in the results is summarised below (Table 22).

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Non-composite 162 0.5% 2 0.3%

Composite effect 164 0.5% 2 0.3%

Table 22 Interference power sum of receiver overload from three networks for sample area [Source: Analysys Mason]

Scaling this result nationally, according to the results per geo-type in the North Copenhagen sample area aggregated by geo-type nationally, suggests that between 2 500 and 3 000 of the households in Denmark that receive television via DTT could be subject to receiver overload from the combined effects of three LTE networks operating in the 800MHz band.

4.4 Impact of using realistic EIRP levels on the potential for ACI

Assessing the impact of LTE on ACI in the North Copenhagen sample area if the LTE networks are using realistic EIRP levels, we also found a significant reduction in the ACI effects, compared to a situation where all sites use their maximum licensed EIRP level. The results of the ACI analysis are shown in the tables below. In the ACI case, since effects are frequency-dependent, we have repeated the analysis to investigate the effect of a different network (A, B or C) using the lowermost LTE channel (FDD1), which our initial analysis showed to cause the most ACI.

For each calculation we assumed a network would use a 2x10 MHz bandwidth within the 800MHz band – hence in the first set of results below (Table 23), Network A is assumed to use blocks FDD1 and FDD2, Network B uses blocks FDD3 and FDD4, and Network C uses blocks FDD5 and FDD6.

29 The power sum calculation takes account of the aggregated effect of LTE signals arriving from different sources at the receiver.



DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network A

(FDD1/FDD2)

485 1.6% 4 0.6%

Network B

(FDD3/FDD4)

65 0.2% 1 0.1%

Network C

(FDD5/FDD6)

49 0.2% 0.5 0.1%

Table 23 ACI per network – Network A in blocks FDD1/FDD2 [Source: Analysys Mason]

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network B

(FDD1/FDD2

290 0.9% 4 0.6%

Network C

(FDD3/FDD4)

100 0.3% 1 0.2%

Network A

(FDD5/FDD6)

95 0.3% 1 0.1%

Table 24 ACI per network – Network B in blocks FDD1/FDD2 [Source: Analysys Mason]

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network C

(FDD1/FDD2

314 1% 3 0.5%

Network A

(FDD3/FDD4)

240 0.8% 2 0.3%

Network B

(FDD5/FDD6)

46 0.1% 1 0.1%

Table 25 ACI per network – Network C in blocks FDD1/FDD2 [Source: Analysys Mason]

The areas affected in each case are illustrated in the maps below. We have also illustrated the location of DTT sites within the North Copenhagen sample area. In the maps, blue areas show ACI caused by Network A, green by Network B and yellow by Network C.

Comparing the maps below with our geo-types for the sample area suggests that ACI only affects suburban and rural areas; none of the urban areas within our sample were affected by ACI. This is assumed to be due to two factors; firstly more DTT households in suburban and rural areas being located further from



DTT transmitters, and so at the edge of DTT coverage (noting that ACI depends on the ratio between DTT and the LTE signal levels), and secondly, the density of LTE base station sites, which means sites will transmit at lower powers in general.



Figure 24 Areas affected by ACI – Network A in FDD1/FDD2 [Source: Analysys Mason]



Figure 25 Areas affected by ACI – Network B in FDD1/FDD2 [Source: Analysys Mason]



Figure 26 Areas affected by ACI – Network C in FDD1/FDD2 [Source: Analysys Mason]

Extrapolating the ACI results from our North Copenhagen sample area to a national level provides the results shown below, suggesting that up to 2 000 DTT households could be affected by ACI from a network using LTE blocks

FDD1/FDD230.

30 We have scaled the results from the sample area to the national area of Denmark using DTT channel 59 by geo-type.



DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

total area

Network A 1935 1.5% 35 0.5%

Network B 1164 0.9% 43 0.9%

Network C 1270 1% 36 0.5%

Table 26 ACI from LTE block FDD 1 to DTT Channel 59 using realistic LTE EIRP levels, scaled nationally [Source: Analysys Mason]

It is noted that the North Copenhagen sample area for our analysis is not an area that uses Channel 60 and so the national ACI results in this case relate to the number of households receiving ACI within areas of the country viewing services

via DTT Channel 59 and not via DTT Channel 6031. Noting this, Section 0 of this report provides further analysis within another sample area of the country using DTT Channel 60 using the same approach to setting realistic EIRP levels as described previously.

From our initial analysis described in Section 3 (using maximum licensed EIRP at all sites) we found that around 4 800 DTT households would be affected by ACI in areas using Channel 59, and so the revised results described in this section using realistic EIRP levels suggests a 60% reduction in affected households.

As with our initial analysis, it should be noted that a proportion of households suffering ACI will also experience receiver blocking, which is the more severe of the two interference effects since it can result in loss of the entire DTT service, rather than just the MUX being broadcast on the channel(s) affected by ACI.

The maps below illustrate the overlap that occurs between areas predicted to suffer from receiver overload and ACI within the North Copenhagen sample area, for each of the networks considered. It also illustrates that ACI affects more DTT households than receiver overload. As noted previously, in the North Copenhagen sample area considered, all of the predicted ACI falls outside urban areas.

31 The North Copenhagen sample area was chosen because it contains a distribution of different geo-types and because a similar area was assessed in our initial analysis in Section 3 in our initial analysis of receiver overload.



Figure 27 Areas affected by ACI only, compared to ACI and blocking – Network A in FDD1/FDD2 [Source: Analysys Mason]



Figure 28 Areas affected by ACI only, compared to ACI and blocking – Network B in FDD1/FDD2 [Source: Analysys Mason]



Figure 29 Areas affected by ACI only, compared to ACI and blocking – Network C in FDD1/FDD2 [Source: Analysys Mason]

4.5 Impact of realistic EIRP levels on ACI in DTT Channel 60 areas

The analysis described in the previous sections focuses on an area to the north of Copenhagen which is served by DTT Channel 59. However, as indicated by our initial analysis in Section 3, it is areas using Channel 60 that are likely to suffer the most ACI, due to the smaller frequency separation between LTE Channel FDD1 and DTT Channel 60, compared to between FDD1 and DTT Channel 59.

To consider the impact of ACI on DTT Channel 60, we selected an area of Denmark served by Channel 60, in order to repeat our analysis using realistic EIRP levels for LTE base stations within the selected area.

The area selected is between Ringsted and Sorø, as illustrated below. The total number of households within the Ringsted-Sorø sample area is 27 491 and the total area is 705.20 km2. This area was selected for further analysis because our initial analysis suggested that this area might be particularly susceptible to ACI (as indicated in Figure C.2 in annex C of this report), possibly due to there being



a lower DTT field strength in parts of this area, as a result of its location relative

to the nearest DTT transmitters32.

Figure 30 Selected Ringsted-Sorø sample area for ACI Channel 60 analysis [Source: NITA]

We followed the same approach as described in Section 4.1 to determine an individual EIRP per site for several LTE800 networks, assuming that LTE800 is deployed on existing GSM900 sites in the area.

For each of the three networks, we firstly assigned a geo-type for each of the existing GSM900 sites in the area, illustrated below.

32 The area is served by two DTT transmitters – Vordingborg and Jyderup, however the city of Ringsted, which appeared from our initial analysis to be particularly affected by ACI, is located between the two sites and so is possibly receiving a lower field strength relative to other areas located closer to one of the sites.



Figure 31 Geo-types assigned to existing GSM900 sites in Ringsted- Sorø [Source: Analysys Mason]

This resulted in the following distribution of sites per geo-type, per GSM900 network in the Ringsted-Sorø sample area.


Network A 1 5 11

Network B 2 10 21

Network C 1 12 12

Table 27 Number of sites per geo-type within the Ringsted-Sorø sample area [Source: Analysys Mason]

It should be noted that because the sample area is a predominantly rural, it has a significantly lower number of sites compared to the north Copenhagen area considered in the previous section of this report.

We assigned an EIRP level to each site with the sample area, relative to the distance from the nearest neighbouring site, as before.

Predicting coverage for each of the networks using the assigned EIRP levels in our planning tool resulted in the following estimates of coverage within the selected area.



Figure 32 EIRP per site and coverage – Network A [Source: Analysys Mason]

Figure 33 EIRP per site and coverage – Network B [Source: Analysys Mason]



Figure 34 EIRP per site and coverage – Network C [Source: Analysys Mason]

Assessing the potential for ACI from these LTE networks to households in the Ringsted-Sorø sample area using the same approach as described previously, we found a reduction in the number of households affected by ACI from Network A compared to our initial analysis (described in Section 3) where all sites use their maximum licensed EIRP level. Networks B and C exhibited higher levels of ACI that our initial analysis. This is primarily because Networks B and C both contained more base station sites than the network we modelled our initial analysis on – although some of those base stations are at a lower power than

those assumed in our initial analysis33.

The results are shown in the tables below. As before, we repeated the analysis to investigate the effect of different networks (A, B or C) using the lowermost LTE channel nearest to DTT (i.e. LTE FDD1) and so the results for each network are presented below.

33 Because of the predominantly rural nature of the Ringsted-Sorø area it should be noted that many of the base stations in our „optimised‟ network were estimated to require between 54 and 56 dBm EIPR using our approach to calculating EIRP relative to the nearest neighbouring site,



DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network A

(FDD1/FDD2)

370 6.7% 20 2.9%

Network B

(FDD3/FDD4)

148 2.7% 6 0.9%

Network C

(FDD5/FDD6)

50 0.91% 2 0.2%

Table 28 ACI per network – Network A in blocks FDD1/FDD2 [Source: Analysys Mason]

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network B

(FDD1/FDD2

588 10.7% 33 4.7%

Network C

(FDD3/FDD4)

159 2.9% 5 0.7%

Network A

(FDD5/FDD6)

43 0.8% 1 0.2%

Table 29 ACI per network – Network B in blocks FDD1/FDD2 [Source: Analysys Mason]

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network C

(FDD1/FDD2

580 3.7% 26 3.7%

Network A

(FDD3/FDD4)

124 2.3% 3 0.5%

Network B

(FDD5/FDD6)

38 0.7% 2 0.3%

Table 30 ACI per network – Network C in blocks FDD1/FDD2 [Source: Analysys Mason]

The areas affected in each case are illustrated in the maps below.



Figure 35 Areas affected by ACI – Network A in FDD1/FDD2 [Source: Analysys Mason]

Figure 36 Areas affected by ACI – Network B in FDD1/FDD2 [Source: Analysys Mason]



Figure 37 Areas affected by ACI – Network C in FDD1/FDD2 [Source: Analysys Mason]

The results show that Networks B and C using LTE blocks FDD1/FDD2 affected more households compared to Network A using the same frequency blocks. This is potentially because Networks B and C provide a higher proportion of population coverage around the Ringsted city area than Network A, where there is a higher concentration of households affected by ACI.

Within Network A there is only one existing GSM900 site close to the Ringsted city area and so, although we have assumed that this site operates at a maximum licensed EIRP of 56 dBm, the percentage of population coverage from Network A is lower than provided by Networks B and C.

It is also noted that whilst it was possible to reduce the EIRP levels for some sites with the selected area within our revised analysis, compared to the maximum levels assumed in our initial analysis, a number of sites in each network in our revised analysis remained at the maximum EIRP level of 56 dBm.

This is because the selected Ringsted-Sorø area is a predominately rural area with fewer GSM900 sites than other suburban or urban areas, and hence use of the maximum allowed EIRP is necessary to provide sufficient area coverage.

We also believe that lower DTT wanted field strengths assumed within our model in the Ringsted city area are potentially contributing to the level of ACI that our model has estimated. According to the revised Danish DTT plan (described earlier in this report), there are two DTT sites serving the Ringsted-Sorø area, but the Ringsted city area (where our modelling indicates ACI to be particularly prevalent), sits between the coverage of the two sites. This suggests the wanted field strength to Ringsted might be lower than the field strength received at other conurbations within the area that are located closer to one of the DTT site, as illustrated in the diagram below.



Legend

DTT coverage from

site JYDERUP

DTT coverage from

site VORDINGBORG

Location of households

Figure 38 Density of households near Ringsted city area [Source: Analysys Mason]

Extrapolating the ACI results from our Ringsted-Sorø sample area to a national level (i.e. for all areas of the country where Channel 60 is used) provides the results below, suggesting that between 4 500 and 5 000 DTT households could be affected nationally by ACI from Network A in our analysis using FDD1. This number could increase to between 7000 and 7 500 if Networks B or C use blocks

FDD1 and FDD234. This compares to our previous estimate (from our initial analysis in Section 3) of around 5 600 DTT viewing households in channel 60 areas being affected from ACI from an LTE network using block FDD1.

However, it is possible that our extrapolation to a national figure in this case is misleading, because of the specific characteristics of DTT coverage in the sample area and in particular around the Ringsted city area that we believe has led to a higher predicted number of households affected by ACI in that area. Extrapolating that result could therefore result in an over prediction of households likely to be affected within Channel 60 areas nationally. We would therefore recommend caution when interpreting these figures and expect that the actual number of households affected by ACI within Channel 60 areas across Denmark may be less that the numbers predicted by our extrapolation from the Ringsted-Sorø sample area.

It should also be noted that the difference in results between Network A and Networks B and C reflects the different coverage levels between the three networks – in our modelling, Network A has a lower number of base stations

34 We have scaled the results from the Ringsted-Sorø sample area to the national area of Denmark by geo-type.



within the Ringsted-Sorø area than Networks B and C and therefore the coverage from Network A is lower than the equivalent coverage from Networks B and C.

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

total area

Network A 4 750 7.0% 192 2.9%

Network B 7 265 10.7% 314 4.8%

Network C 7 250 10.7% 248 3.8%

Table 31 ACI from LTE block FDD 1 to DTT Channel 60 using realistic LTE EIRP levels, scaled nationally [Source: Analysys Mason]

4.6 Effect on indoor coverage

Noting that some households do not receive DTT services using an externally mounted antenna, but use portable antennas indoors, we have repeated the ACI analysis for the selected Channel 60 Ringsted-Sorø sample area, as described in the previous section, to consider the impact on households if portable indoor reception is assumed. It should be noted that indoor DTT coverage in this area is very limited due to low DTT field strength.

For this analysis, rather than the correction values listed in Table 6 in Section 2, we have applied a locations margin of 22dB (from section 6.2.3 of the JTG 5/6 methodology), and an indoor reception correction factor of 8.2dB (from Table 4 of ECC Report 148).

The PR values for indoor coverage, with correction factors, assumed in our analysis are therefore in Table 12 below.


60 -6 -14 -19

Table 32 PR values plus correction factors, Channel 60 coverage, portable indoor reception [Source: Analysys Mason]

A 3dB polarisation discrimination value used in our earlier analysis also no longer applies. This is because, for portable reception, an omnidirectional antenna pattern is normally assumed, and hence neither directivity nor polarisation discrimination is applied.

The minimum median field strength for portable reception is assumed to be 66dBµV/m, which is calculated from the original value of 58dBµV/m for outdoor coverage for the Boxer DTT network, plus an in-building penetration loss of

8dB35.

35 We have also re-predicted field strength maps for LTE coverage relative to a 1.5 metre receiving height for DTT.



Results are shown below. As with previous analysis, we have repeated the analysis to illustrate the effect of the different LTE networks (A, B and C) using the lowermost LTE channel (FDD1).

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network A

(FDD1/FDD2)

216 3.9% 11 1.6%

Network B

(FDD3/FDD4)

70 1.3% 4 0.6%

Network C

(FDD5/FDD6)

29 0.5% 1 0.2%

Table 33 ACI per network for indoor coverage – Network A in blocks FDD1/FDD2 [Source: Analysys Mason]

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network B

(FDD1/FDD2

279 5.1% 17 2.5%

Network C

(FDD3/FDD4)

84 1.5% 3 0.5%

Network A

(FDD5/FDD6)

31 0.6% 1 0.1%

Table 34 ACI per network for indoor coverage – Network B in blocks FDD1/FDD2 [Source: Analysys Mason]

DTT households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

area affected

Network C

(FDD1/FDD2

290 5.3% 14 2%

Network A

(FDD3/FDD4)

71 1.3% 2 0.4%

Network B

(FDD5/FDD6)

23 0.4% 1 0.2%

Table 35 ACI per network for indoor coverage – Network C in blocks FDD1/FDD2 [Source: Analysys Mason]

The areas affected in each case are illustrated in the maps below, which illustrate that the locations of households predicted to be affected by ACI are similar for indoor and outdoor reception (i.e. by comparing these results with those presented in Figure 35, Figure 36 and Figure 37).



Figure 39 Areas affected by ACI (indoor reception) – Network A in FDD1/FDD2 [Source: Analysys Mason]

Figure 40 Areas affected by ACI (indoor reception) – Network B in FDD1/FDD2 [Source: Analysys Mason]



Figure 41 Areas affected by ACI (indoor reception) – Network C in FDD1/FDD2 [Source: Analysys Mason]

Extrapolating the ACI results from the Ringsted-Sorø sample area to a national level (i.e. for indoor reception for all areas of the country where Channel 60 is used) provides the results below, suggesting that between 2 800 and 3 700 DTT households would be affected by ACI from a network using LTE blocks

FDD1/FDD2 for indoor reception36.

Households

affected

Percentage of

households

affected

Area affected

(km2)

Percentage of

total area

Network A 2840 4.2% 104 1.6%

Network B 3441 5.1% 165 2.5%

Network C 3622 5.3% 136 2.1%

Table 36 ACI from LTE block FDD 1 to DTT Channel 60 using realistic LTE EIRP levels, scaled nationally, indoor coverage [Source: Analysys Mason]

These results are consistent with the results from our earlier analysis of indoor coverage (described in Section 3.2), where we found that the number of households affected by ACI for indoor reception could be slightly lower than the equivalent number affected if fixed outdoor reception is assumed.

36 We have scaled the results from the Ringsted-Sorøsample area to the national area of Denmark by geo-type.



4.7 Effect of site sharing between the three networks

We have also evaluated the impact of increased site sharing between the three networks. This is expected to reduce receiver overload since the overall number of sites within the area will be reduced. We estimate that within the North Copenhagen sample area, mobile operators currently share about 23% of their sites. For our analysis, we have increased this to 30%, as shown below.

Total sites Sites shared

amongst two

operators

Sites shared

amongst three

operators

Percentage site

share

Existing site sharing 311 57 15 23%

Increased site sharing 311 78 15 30%

Table 37 Site sharing in North Copenhagen sample area [Source: Analysys Mason]

The results of our analysis are shown in Table 38 below. They suggest that increasing site sharing and using realistic EIRP levels are effective as a means of substantially reducing the risk of receiver overload. It is expected that operators will voluntarily deploy a combination of both reduced EIRP and increased site sharing – within urban areas in particular – in order to comply with planning regulations and to deal with a lack of availability of base station sites, as well as other practical considerations.

DTT

households

affected

Percentage of

households

Area affected Percentage of

total area

Receiver overload with

reduced EIRP levels

163 0.5% 1.76 0.3%

Receiver overload with

reduced EIRP levels and

increased site sharing

34 0.1% 0.43 0.1%

Table 38 The effect of using realistic LTE EIRP levels and increased site sharing on receiver overload [Source: Analysys Mason]

4.8 Near-field interference effects

Within the „near field‟ of LTE antennas, propagation characteristics vary from the

typical „far field‟ range assumed within our analysis37. Accordingly, a household located within the near field of an antenna will typically experience more interference that one located in the far field.

37 The electromagnetic field of an antenna in the far field (free space assumptions) generally falls in amplitude by 1/r (meaning that the total energy per unit area at a distance r is proportional to 1/r

2).

In the near field, by contrast, the energy level and coupling mechanism is very variable.



We estimate that the near field range of an LTE800 antenna will be around 20 metres, and on this basis we have estimated the number of households within this distance of our modelled base stations (noting that our modelling is based on existing 900MHz site locations). We estimate that around 217 households in the north of Copenhagen area used in the analysis through this section of the report are located within the near field of an LTE base station from one LTE network. However, since some LTE sites of different networks are very close together and therefore affect the same household, our estimate is that the total number of households affected is only 191.

Considering this effect across Denmark (assuming LTE800 is deployed on existing GSM900 sites of the three 2G mobile operators), we estimate that up to 500 households in total could be located within 20 metres of an LTE800 antenna.

The total equivalent area affected (i.e. the sum of the areas located within 20

metres of LTE800 antennas, nationally across Denmark) is 5.13 km382.

4.9 Summary of results

Our detailed analysis of the effect of varying the LTE base station EIRP at individual sites is a more realistic simulation of actual LTE network deployments compared to our initial analysis which used the maximum licensed EIRP at all sites (59dBm, or 56dBm in Channel 60 areas). The results of this more detailed analysis suggest that ACI could affect more households than receiver overload when taking into account the effects of lowering EIRP at individual base station sites, but the numbers affected by both blocking and ACI are substantially lower than in our initial analysis (with the exception of the analysis of ACI to the selected Channel 60 area, which, as described, we believe highlights a particular issue associated with low DTT wanted field strength in that area, which is affecting the potential for ACI).

In particular, we found that the effect of reducing EIRP at individual sites means that the percentage of households predicted to be affected by receiver overload in urban areas of the country could be substantially reduced (and since our initial model suggested the highest proportion of ACI occurs in urban areas, the EIRP reduction per site in urban areas leads to a substantially lower overall number of households affected by overload). The majority of households affected by receiver overload and ACI in our more detailed analysis are now located in suburban and rural areas, and not urban areas, with a much lower overall number of households affected.

From the results obtained for the sample areas modelled, the following key points should be noted:

The results we have presented are for sample areas to the north of Copenhagen and around Ringsted-Sorø. We have assumed that three networks are deployed, each using 2x10 MHz of spectrum from the 800MHz band. The site density per network, site locations and heights are based upon existing GSM900 network deployments. EIRP levels have

38 This area corresponds to 4 824 base stations with a near field area of radii 20 metres.



been theoretically derived using an EIRP-to-site-separation relationship, developed based upon the LTE link budget derived by Analysys Mason for this study, and contained in Annex D.

Using these assumptions regarding the LTE network design, we have found that there is a substantial reduction in the number of households affected by receiver overload, compared to the initial analysis assuming all sites radiate at their maximum licensed limit. We have also found that the number of households predicted to be affected by ACI in the North of Copenhagen area (where DTT Channel 59 is used) is substantially lower from our more detailed analysis in view of reduction in EIRP levels applied at individual sites. For the Ringsted-Sorø area, where DTT Channel 60 is used, we found a reduction in ACI from our more detailed analysis for one of the networks modelled (Network A). This network is the most similar to the characteristics of the LTE800 network we assumed in our initial analysis. In our more detailed analysis, we also considered two other network configurations – referred to as Networks B and C – which have a higher density of base station sites than Network A. Although in some cases this higher density of sites leads to a corresponding reduction in EIRP (and therefore lower ACI), we found for the Ringsted-Sorø area that we had to use the highest level of EIRP (56 dBm) at a number of sites in order to provide coverage across the predominantly rural area. We believe that this, along with the specific characteristics of the DTT coverage in that area, has led to our model predicting higher levels of ACI for Networks B and C in that area compared to Network A, which has a lower overall coverage due to less base station sites.

Within the North of Copenhagen sample area, we found that our more detailed model predicts that the three LTE800 networks will result in around 160 DTT viewing households being subject to receiver overload (summing the individual effects of each of the networks). This suggests approximately 0.6% of the DTT households in the area might be affected. Extrapolating this result nationally suggests between 2 500 and 3 000 DTT households might be affected by blocking from at least one of the three LTE networks, assuming those networks use varying EIRP levels per site consistent with the geo-type of the area and the proximity of sites. This compares to up to 150 000 DTT households estimated to be affected by overload from our initial analysis, if all sites in three national LTE networks operate at maximum licensed power. The use of more realistic EIRP levels per site therefore results in a 98% reduction in the number of households subject to receiver overload.

We believe that the use of lower EIRP levels at individual LTE sites is a better representation of how LTE networks will be deployed in practice, because in practice operators face various practical constraints that limit the power level from individual sites and will therefore tend to use lower EIRP levels at some sites, particularly in urban areas. Such constraints might include restrictions on antenna heights, restrictions due to mast sharing, and use of combiners and other RF equipment (e.g. to integrate 800MHz and 900MHz networks), which will cause losses that will reduce the radiated power in practice.

For ACI, we have found that the number of households affected in a given area depends on the LTE network deployment, as well as the



characteristics of DTT coverage in the area. We have evaluated the difference between three LTE network deployments, each modelled based upon existing GSM900 site locations, but using realistic EIRP levels for LTE deployment. For the three networks modelled, we found the ACI caused by each individual network using LTE blocks FDD1/FDD2 affects between 290 and 485 DTT households within the north of Copenhagen area depending on the LTE network deployment (this represents ACI to DTT services using Channel 59, since Channel 60 is not used within this area). Extrapolating these numbers nationally (within areas of Denmark using Channel 59), it is estimated that around 2 000 DTT households might be subject to ACI from an LTE network using channels FDD1/FDD2. These numbers can be compared to our original estimate of 4 800 DTT households affected by ACI within Channel 59 areas, suggesting that the modelling of realistic LTE EIRP levels results in nearly 60% reduction in ACI from LTE blocks FDD1/FDD2 into DTT Channel 59.

For the three networks modelled in the Ringsted-Sorø area, we found that ACI could affect between 370 and 590 households in the area in total. Extrapolating these results national suggests between 4 500 and 5 000 DTT households located within Channel 60 areas nationally could be subject to ACI from an LTE800 network based upon the Network A in our detailed analysis. This can be compared to the 5 600 DTT viewing households potentially affected, based upon our initial analysis, confirming that optimising the EIRP level at individual sites has a positive impact in terms of reducing the number of households potentially affected by ACI. However, we found by extrapolating our results for Networks B and C that additional households could be affected, up to between 7 000 and 7 500. We believe this is due to the higher site density (and therefore increased coverage) of those networks compared to Network A, particularly around the Ringsted city area, where both networks have more sites leading to a higher percentage of population coverage. However, we believe that the primary cause of the higher number of households affected in this area is due to the particular characteristics of DTT coverage, as described previously.

The potential for individual households to receive interference is influenced by the location of households with respect to LTE base stations (for receiver overload) and also by the DTT field strength received by the household (for ACI). Our analysis also suggests that the characteristics of the LTE network in terms of the number of base stations and the EIRP per base station is relevant. We have demonstrated that networks with more base stations typically require less power per base station (if EIRP is determined for individual sites relative to the nearest neighbouring site). Lowering the EIRP in turn leads to a reduction in households suffering DTT receiver overload.

It is noted that there will be a very small number of households located within the near field of LTE antennas that may suffer more interference than predicted from our modelling, since our propagation model is applicable for modelling of far field effects. Using the existing 900MHz base station locations as a basis, and taking account of the fact that a few households are located very close to base stations of more than one



mobile network, we estimate around 500 DTT households lie within the near field of an LTE800 antenna.

We have noted the following areas of uncertainty within our modelling:

There are various different approaches to deploying LTE, and mobile operators will typically adopt a particular approach to reflect their particular coverage and capacity objectives, and existing site grids. We expect operators with existing GSM900 networks will, over time, deploy LTE800 equipment at all – or the majority of – existing GSM900 sites, for coverage reasons. Additional LTE capacity might be provided using other frequency bands (e.g. 1800MHz, 2100MHz, 2600MHz), which might share the same sites, or use different sites, but will not interfere with DTT.

Although the ideal solution for operators is to optimise the EIRP per site to manage interference levels within the network, in reality operators may have a standard EIRP design at selected sites during the initial rollout of LTE800. It is expected that this might be optimised over time such that operators will deploy a range of base station powers over time taking account of various factors. Therefore, the EIRP level at individual LTE sites, as well as the number of sites employed, will change as networks evolve. It is also noted that power control within LTE networks will be used to optimise the radiated power depending on local conditions and location of users within a cell. In addition, LTE is expected to use MIMO (Multiple In, Multiple Out) antennas that will also influence instantaneous radiated power.

Susceptibility to interference will be affected by the type of DTT installation being used, as well as the quality of DTT coverage being received. In particular the use of different antenna systems and amplifiers may impact whether a household receives receiver overload and/or ACI. This has not been accounted for in our modelling and would require further detailed investigation by NITA. Our modelling does account for

variability in DTT coverage, since we have used field strength maps obtained from DTT broadcasters in Denmark as the basis of determining DTT field strengths for our analysis. Our results highlight that households in areas receiving a weaker DTT field strength are more susceptible to ACI.

Our extrapolation of results for the Ringsted-Sorø area should be treated with caution, in view of the particular characteristics of DTT coverage in that area (and potential low wanted DTT field strengths around Ringsted), which we believe has contributed to a higher concentration of households affected by ACI within that area. This applies to both indoor and outdoor DTT coverage. Extrapolating those results nationally is therefore likely to lead to an over estimation of the actual number of households likely to be affected by ACI in Channel 60 areas.

Evaluation of possible mitigation measures 79


5 Evaluation of possible mitigation measures

There are a number of mitigation measures that can be used to restore DTT services and/or mitigate the risk of receiver overload and ACI occurring. In this section, we describe a range of possible mitigation techniques that can be envisaged, and consider the effect of each technique individually.

It is noted that the analysis presented in Section 4 suggests that if realistic EIRP levels are assumed per base station (rather than all base stations radiating at their maximum licensed level), the number of households potentially subject to receiver overload and/or ACI reduces substantially. The mitigation techniques considered in this section can therefore be considered to be options to mitigate interference over and above the optimisation of LTE base station EIRP as described in the previous section.

5.1 Use of DTT receiver filters

The technical feasibility of DTT receiver filtering has been addressed in various

published studies39. Low-pass filters (sometimes referred to as band rejection filters) can be used as a means of restoring DTT services by filtering out the LTE

interference at the DTT receiver, without otherwise affecting DTT reception40. These filters work by attenuating the power received in the DTT channel from the LTE base station(s), thereby increasing the DTT carrier-to-interference (C/I)

ratio41, which prevents the receiver being affected by ACI or receiver overload (depending on the level of attenuation that the filter provides into the affected DTT channel).

Low-pass UHF filters are available within the European market today, and information we have obtained from one filter manufacturer suggests the unit cost is around EUR10–15. A consultation document published by the UK Office of

Communications also suggests a cost of GBP1042. Different models are available to attenuate interference to DTT services using Channels 58, 59 and 60 (i.e.

type 58, type 59 and type 60 filters).43

39 For example, a study by Cobham Technical Services for the UK Office of Communications, submitted to the ECC, see http://stakeholders.ofcom.org.uk/binaries/consultations/ddr/statement/ERA2.pdf

40 It is noted that insertion loss of up to a few dBs might occur based upon typical filter specifications. This is not expected to affect reception of DTT services other than to a small proportion of households who might be receiving a weak DTT field strength.

41 C/I ratio is described in ECC Report 148 as being “The ratio, generally expressed in dB, of the power of the wanted signal to the total power of interfering signals and noise, evaluated at the receiver input”.

42 See page 29 of http://stakeholders.ofcom.org.uk/binaries/consultations/dtt/summary/dttcondoc.pdf

43 Braun Telecom indicates that filter model LPF-774-LONG is available for protection of channel 58, LPF-782-LONG for protection of channel 59 and LPF-790-LONG for protection of Channel 60.



The interference attenuation that each filter provides depends upon the frequency separation between the LTE interference and the DTT reception, meaning that attenuation is lower for interference into Channel 60 compared to Channels 59 and 58, since Channels 59 and 58 have a greater frequency separation from the 800MHz band. An example of typical attenuation and

insertion loss44 is shown in Figure 42 below, provided by Braun Telecom.

Figure 42 Characteristics of UHF filter [Source: Braun Telecom]

Based on the figure above, which represents the „LPF-790-LONG‟ filter model for DTT Channel 60, we have estimated the following attenuation from LTE emissions can be achieved:

from FDD1, around 5dB



from FDD4 and above, more than 20dB.

The typical insertion loss is 3dB or less, thus the typical C/I improvement for Channel 60 is around 2dB for FDD1, 5dB from FDD2, 12dB from FDD3 and greater than 17dB for FDD4 and above. For Channel 59, the typical C/I improvement is expected to be better than 5dB for FDD1.

To illustrate the effectiveness of filters being added to the DTT receive path, we have assessed the impact of an extra 5dB and 10 dB attenuation being added to our modelling of the calculated probability of receiver overload. The results are summarised in the table below, relative to the number of households we predicted might be affected by receiver overload from our detailed network

44 Insertion loss refers to the loss of DTT signal power resulting from insertion of a filter in the receive path.



analysis for the North of Copenhagen area, described in the previous section. Applying 5 dB and 10 dB of attenuation to that analysis, respectively, we have calculated the percentage reduction in the number of households and area affected by receiver overload and ACI, as shown below.

Filter attenuation

(dB)

Affected area

(km2)

Affected area

(% of total in

sample area)

Affected DTT

households

(number)

Affected

households (% of

total in sample

area)

No filters 0.97 0.2% 111 0.4

5 0.32 0.1% 30 0.1

10 0.1 0.0% 6 0.0

Table 39 Estimated reduction in the potential for blocking from use of DTT receiver filters using realistic EIRP analysis for selected Channel 59 area [Source: Analysys Mason]

Filter attenuation

(dB)

Affected area

(km2)

Affected area (%

of total in sample

area)

Affected DTT

households

(number)

Affected

households (% of

total in sample

area)

No filters 3.63 0.6 485 1.6

5 1.07 0.2 167 0.5

10 0.37 0.1 36 0.1

Table 40 Estimated reduction in the potential for ACI from use of DTT receiver filters using realistic EIRP analysis for selected Channel 59 area [Source: Analysys Mason]

These results suggest a 73% reduction in the number of households subject to receiver blocking for a filter providing 5dB of attenuation, and 95% for a filter providing 10dB of attenuation. For ACI, the percentage reduction is 65% for a filter providing 5dB of attenuation and 93% for 10dB of attenuation.

We have also considered the impact of filters providing 5dB of attenuation on the potential for ACI to households in the Ringsted-Sorø area. Results from this analysis are presented below.



Filter attenuation

(dB)

Affected area

(km2)

Affected area (%

of total in sample

area)

Affected DTT

households

(number)

Affected

households (% of

total in sample

area)

No filters 3 2.9 370 6.7

5 1 1 193 3.5

Table 41 Estimated reduction in the potential for ACI from use of DTT receiver filters using realistic EIRP analysis for selected Ringsted-Sorø area [Source: Analysys Mason]

These results therefore suggest a 47% reduction in the number of households subject to ACI in the selected Channel 60 area, if a filter provides 5 dB of attenuation.

In practice, it should be noted that different levels of attenuation will be required for different households, depending on the DTT channel(s) being used and the source of LTE interference. We have not evaluated the precise level of attenuation required at each household within the sample areas of our modelling as part of this study.

As noted from the filter characteristics provided by Braun Telecom, it is possible that filters will not fully mitigate interference from the lowermost LTE block (FDD1) into DTT Channel 60 because the filter does not provide sufficient attenuation (i.e. limited to 2dB or less). Our modelling results described above suggests that filters can be expected to substantially mitigate interference between all other frequency combinations of LTE and DTT where attenuation of 10dB or greater is achieved and provide some mitigation where 5dB of attenuation is achieved. However, specifically for Channel 60 ACI from FDD1, filtering is only able to provide limited mitigation (approximately 2dB) due to the very limited frequency separation (of 1 MHz).

5.2 Mitigation via additional filtering on LTE base stations

We note that the use of additional filtering on LTE base stations (possibly in combination with rejection filters on DTT receivers) could further reduce the potential for ACI and receiver overload interference in some cases.

The use of additional LTE base station filters was previously studied within the CEPT Spectrum Engineering (SE) 42 committee, suggesting limited impact with respect to reducing ACI. However, it is possible that LTE base station filters can have some benefit by reducing the out-of-band component of base station interference (often referred to as „spectral leakage‟). We estimate this could provide around 5dB of additional reduction in the out-of-band component of ACI. Combined with filtering at DTT receivers, this could result in an additional C/I improvement compared to that achieved using the low pass filters described in the previous section alone.

As illustration of this, a consultation document published by the UK Office of Communications also suggests that “additional base station transmitter filtering … is particularly effective when used in combination with DTT filtering in areas



which use either Channel 59 or 60 for DTT “45. The consultation document found that “the incremental cost of higher quality filters (over and above those needed to comply with the out-of-block emission limits set by the Decision) is around GBP40-GBP70 per antenna, or GBP240-GBP420 per base station” and concluded that mitigation via LTE base station filters was an effective and cost-efficient mitigation technique.

The EC‟s 800 MHz Decision specifies Block Edge Masks (BEM) that LTE800 base stations must comply with, as described earlier in this report. It is expected that some base station filtering will be required to comply with these masks.46 Additional filtering could result in reduced interference into DTT services, as described above. The main downside of this for mobile operators is an increase in the cost of deployment per base station as a result of the increased filtering cost (as illustrated by the UK Office of Communications estimates above). Additional filtering also requires extra space to be available at base station sites, although more recent approaches to filter technology aim to reduce their size, weight and power consumption, as well as to achieve a very small insertion loss (i.e. the small loss of signal power that results from insertion of the filter at the base station, leading to reduction in transmitted power).

5.3 Use of cross-polarisation between LTE and DTT

Improving the field strength of the DTT service is a possible form of ACI mitigation that has been considered in various studies. One way of achieving this is to use cross-polarisation of antennas between LTE and DTT (i.e. using the opposite of DTT polarisation at LTE base stations).

DTT transmissions in Denmark use a mixture of horizontal and vertical polarisation – horizontal polarisation is generally used at main transmitters, and vertical polarisation at relay sites.47 Mobile networks use a range of antenna types and polarisation. Vertical polarisation used to be common, but slant polarisation at ±45 degrees to the horizontal is now often used. Frequently, these slant systems are configured so that base stations transmit on one of the polarisation paths whilst receiving on both, thereby providing a higher diversity gain for the received signal.

From the point-of-view of interference to DTT services, slant polarisation is estimated to provide 3dB discrimination between the LTE and the DTT signal (as indicated in Section 4.2.2.4 of the ITU-R JTG 5/6 methodology for sharing studies

45 See page 31 of http://stakeholders.ofcom.org.uk/binaries/consultations/dtt/summary/dttcondoc.pdf

46 For example, as noted in ECC Report 148, “… additional band pass RF filtering with sufficient attenuation is required to reduce the emissions from the levels set by the 3GPP LTE spectrum emission mask down to the appropriate regulatory BEM baseline limit…”

47 One main DTT site in the Danish network, Thisted, uses vertical polarisation.



between the mobile service and DTT)48. In the analysis presented in Sections 2 and 4 of this report, we have assumed that LTE networks use slant polarisation and so have assumed 3dB discrimination exists.

Studies published by CEPT and the ITU-R have shown that use of vertical antennas would provide increased discrimination to the main DTT stations, and 16dB is usually assumed as the discrimination loss between vertical and horizontal polarisations. This additional discrimination could therefore provide additional mitigation against receiver overload and ACI, by increasing the difference between unwanted LTE and wanted DTT signal levels at affected DTT households.

Our estimate is that the addition of 16 dB discrimination into our modelled interference scenarios could result in up to 90% reduction in the number of households affected by ACI and blocking.

It is noted that use of cross-polarisation discrimination as a means of ACI or receiver overload interference mitigation requires LTE antennas to be vertically polarised if DTT networks use horizontal polarisation, which could limit the capabilities of LTE networks, affecting coverage and capacity. In addition, in Denmark most main DTT transmitters are horizontally polarised though a few main transmitters, and most on-channel repeaters (DTT gap fillers), are vertically polarised.

This means that cross-polarisation is not a mitigation technique that can be applied throughout networks in Denmark, but can possibly be applied in selected areas only receiving a DTT service from a horizontally polarised main transmitter.

5.4 Improving the DTT signal level via on-channel repeaters

An alternative means of improving DTT field strength is to co-site additional in-fill DTT transmitters with LTE base stations. These „gap fillers‟ are termed on-channel repeaters (OCRs), and have the effect of increasing the power of the DTT signal, which means that more households receive a better quality DTT signal. This also reduces the difference between the wanted and the interfering signal levels, and is therefore particularly associated with reducing the impact of interference caused by ACI.

OCRs are an alternative to frequency-shifting repeaters (which receive the DTT signal from a parent site and transpose it to a different frequency). Although such repeaters are a way to enhance DTT coverage, their use has spectrum implications for the DTT network, since there is a requirement for sufficient frequencies to be available in order to transpose the signal to a different channel. In contrast, OCRs re-broadcast the DTT signal using the same channel as the „parent‟ site, thereby avoiding the need for extra channels to be available. An OCR operates by receiving the DTT signal off-the-air, amplifying it and then re-radiating it. This reduces the degradation in signal-to-interference plus noise ratio

48 See ITU-R R07-JTF5-6 – Annex 6 to Joint Task Group 5-6 Chairman‟s Report: Methodologies (including interference objectives) for sharing studies between the mobile service, on the one hand, and the terrestrial broadcasting, on the other hand, in the band 790-862 MHz.



(SINR) by increasing the level of the DTT signal at the victim DTT receiver. Co-siting an OCR on the LTE base station may therefore mitigate the ACI caused by that base station.

However, addition of OCRs can lead to additional interference within the DTT network (either co-channel or adjacent channel) and so careful positioning of OCRs is required to achieve sufficient isolation between the OCR and the main DTT site. For this reason, use of OCRs is not practical in all areas within the DTT network, but they can be used in areas where LTE sites are located near to the edge of the coverage area of a DTT site, which will benefit from increasing the power of the DTT signal to overcome the LTE ACI.

It is noted that the use of OCRs may require DTT viewing households to re-orient antennas to the new OCR site. This would normally require a visit from a trained antenna installer to complete the re-orientation, and so there would be a cost incurred by each household requiring this.

Our estimate is that that the addition of OCRs will be successful in reducing ACI in up to 90% of cases, but does not eliminate it.

It is also noted that the feasibility in practice of deploying additional repeaters within the DTT networks in Denmark would require further practical investigation using field trials – in particular, whether sufficient space and facilities exist at LTE base station sites to enable OCRs to be co-sited, and whether sufficient isolation between the repeater receiving antenna and the LTE transmitting antenna can be ensured by appropriate site mounting.

Additional capital costs are also incurred within the DTT network to deploy OCRs. Our estimate is that the cost of a single OCR is around EUR10 000, plus associated site and installation costs of around EUR5000. There will also be a cost of re-orientating antennas at affected households. Further study would be required in order to identify the number of units that might be required across the DTT network in Denmark – noting, as described previously, that the addition of OCRs is practical only in selected areas of the DTT network. Accordingly, other means of interference mitigation described earlier in this report, such as filtering, are expected to be more widely deployed and will therefore have a greater impact on reducing interference.

5.5 Mitigation via improving DTT receiver design

As described earlier in this report, ECC Report 148 gives protection ratios (PR) and overload thresholds (Oth) for various DTT receiver types (can, silicon and USB tuner). The measurements conducted to determine the protection ratios illustrate performance differences between different DTT types.

As noted in this report, the potential for receiver blocking to occur to DTT receivers depends in particular upon the Oth of the receiver, as well as the distance between the LTE base station and the DTT receiver, and the LTE field strength.



Throughout the analysis in this report, we have assumed an Oth value of -15 dBm, which can be considered as a conservative assumption, since ECC Report 148 describes measured values of between -15dBm and -5dBm. 49,50

In practice, the measurements conducted by the ECC demonstrate that there is currently a significant variation between the Oth of different DTT receivers on the market. For example:

10% of the worst performing receivers on the market have an Oth of -15dBm

50% of the best performing receivers have an Oth of -5dBm

10% of the best performing receivers have an Oth of 0dBm.

A similar variation in performance levels is also illustrated by ECC Report 148 in relation to protection ratio (PR) values relating to ACI. Again, measurements suggest a 10dB variation between measured PR values for the worst performing receivers compared to the best performing receivers.

The measurements in ECC Report 148 therefore demonstrate that it is possible, through current DTT receiver design, for DTT receivers to achieve better performance that the assumptions made in this report.

A possible means of mitigation against receiver overload could therefore be to improve the immunity of DTT receivers, by designing them with a higher Oth. It is feasible that a higher Oth limit could be specified within receiver standards for DTT services, to ensure that future receivers are designed with a higher threshold in mind. Similarly, receiver standards could also be specified to include minimum PR levels determined with LTE interference in mind (noting that DTT to DTT PR values are already provided e.g. in the ITU-R GE-06 agreement).

It is noted that improvements to receiver performance would not reduce the risk of ACI and/or receiver overload in the short term (since the majority of households will already possess one or more digital receivers designed to today‟s standards). It would, however, reduce the risk of interference over the medium term, once households upgrade their receivers in future.

To illustrate the potential effect of this, we have considered the effect of increasing the Oth assumed within our analysis from -15dBm to -5dBm for all DTT households. The results of the analysis are presented below, relative to our initial analysis (based on a single LTE network deployed nationally in which all LTE base stations radiate at their maximum licensed power). The difference between the two thresholds in our analysis is 10 dB, and this improvement produces an 87% reduction overall in the number of households

subject to receiver overload51.

49

-15dBm is the threshold at which 90% of the best performing equipment measured in ECC Report 148 remained unaffected by blocking from LTE.

50 This is the typical range – the full range of measurements described in ECC Report 148 range from 03dBm to -26dBm.

51 These results compare the effect of increasing the Oth relative to our initial analysis described in Section 3, but it is expected that a similar reduction will apply relative to the results using realistic LTE EIRP levels, presented in Section 4.



Overload

threshold (dBm)

Affected area

(km2)

Affected area

(% of total in

Denmark)

Affected DTT

households

Affected

households (% of

total in Denmark)

-15 1529 3.6% 54 045 2.3%

-5 156 0.4% 6 913 0.3%

Table 42 Impact of improving the blocking threshold – modelled for one LTE network interfering with DTT, operating at maximum licensed EIRP [Source: Analysys Mason]

It is noted that Denmark is unlikely to be able to implement such a change by itself. DTT receiver manufacturers design and manufacture products with markets much larger than Denmark in mind – typically for markets the size of the EU. Therefore, in order to implement such a higher Oth limit, Denmark would need to coordinate the proposed changes with other countries, or indeed with the European Commission. It might also be possible to require manufacturers to make a clear declaration concerning the blocking performance of the receiver at the point of sale (e.g. by incorporating a blocking requirement alongside the other requirements that are already necessary to obtain the “Boxer ready” or other similar logos for sale of TV receivers in Denmark.)

5.6 Platform change

It is also noted that in the absence of other suitable means of overcoming interference to DTT, affected households could opt to receive digital TV services via an alternative platform such as cable, satellite or IPTV. It is estimated that around 20% of the Danish population currently receive digital TV services via DTT compared to alternative platforms – around 80% currently already use other means of receiving digital television, mainly using cable networks.

We expect that very few households will need to migrate to another platform as a result of interference from LTE, since very few households will be affected by blocking and ACI if realistic LTE EIRP levels are used and other possible mitigation measures such as those considered in this report are considered over and above optimising the base station EIRP. It is expected that the few households for which no suitable mitigation measure exists will predominantly be those receiving TV services using Channel 60 and/or those located very close to

an LTE base station52.

It is noted that provision of targeted information to DTT households from LTE operators timed with the launch of new LTE800 base stations could also be helpful to alert viewers to potential issues, thus enabling consideration of suitable mitigation measures, such as filters or other techniques, where required.

52 Within this report, we describe potential near-field effects, being localised effects of interference where DTT receivers are located within a 20 metre radius of an LTE base station.



5.7 Other forms of mitigation

We also note that a sufficiently large guard band between the last DTT channel and the first LTE channel would help to reduce ACI. However, this is spectrally inefficient and therefore only a small guard band of 1MHz (between 790 and 791MHz) has been incorporated in the recommended European band plan. This has been the assumption in our analysis.

Interference from LTE uplink emissions 89


6 Interference from LTE uplink emissions

In terms of the potential for interference from LTE mobiles to DTT, it is noted that the European band plan for the 790–862MHz band uses a „reverse duplex‟ arrangement, i.e. the mobile transmit frequencies are in the upper part of the

band, rather than the usual convention of having the mobile transmit frequencies in the lower part of the band. The reason this has been done is primarily because of concerns associated with ACI and blocking from LTE devices to DTT receivers, which could interfere at short distances when both are used within the home. The 800MHz channel plan therefore provides some mitigation against ACI from the LTE uplink through the frequency separation between the uplink channels and the band edge with DTT.

However, with the frequency offset that the channel plan provides, there is still the potential that LTE devices operating close to DTT receivers could cause receiver overload. This is thought to be particularly the case for portable indoor reception, since with fixed outdoor reception there is sufficient spatial separation between the DTT receiver and the LTE transmitting device to mitigate

interference. Papers published by European Broadcast Union (EBU)53 suggest that the potential for blocking to DTT receivers using fixed reception is very small, and only a small percentage (1%) of receivers are affected. For portable reception, however, the number affected is slightly higher. A paper published in

the UK54 suggests that for a typical handset EIRP of 25dBm and a received DTT signal of -72dBm at the coverage edge, the maximum permitted level of handset signal for the onset of failure would be -41dBm, suggesting a required isolation of 66dB between DTT antenna and LTE handset. This corresponds to a minimum separation of 50 metres between handset and DTT antenna.

This is in contrast to other work conducted in the UK by Cobham Technical Services and presented by the UK regulator to the ECC Task Group 4 during

2010.55 This paper presents a series of measurements undertaken in the UK to assess the behaviour of a range of UHF DVB-T receivers when subjected to interference from LTE. Measurements were conducted to assess the effect of LTE terminals on DTT reception both from fixed outdoor antennas and from portable indoor antennas. The radiated measurement results reported by Cobham found that no interference was observed for the fixed outdoor antenna scenario. For the portable indoor scenario, if no filter was used, one DTT receiver type (super-heterodyne) was found to be problematic. In that case, interference was found to occur with the LTE device transmitting at 11dBm at separation distances of 2.5 metres between the LTE terminal and the portable antenna. Other receiver types, which were shown to have better PR performance with respect to LTE, were not interfered with by an LTE terminal at this separation

53 http://tech.ebu.ch/docs/events/ecs10/presentations/ebu_ecs10_workshop_sami.pdf

54 http://docbox.etsi.org/Etsi_Cenelec/PUBLIC%20FOLDER%20on%20DD/UK%20DKTN%20DD/DCKTN%20Digital%20Dividend%20Technologies%20Spectrum%2011Jun10%20v11%20(SR).pdf

55 ECC TG4(10)317, UK measurements of LTE into DTT, presented to the 15th meeting of ECC TG4

90 Interference from LTE uplink emissions


distance, unless the terminal was transmitting at close to its maximum value of 23dBm.

All of the measured interference effects were resolved by the introduction of a low-pass filter in the TV receiving antenna set-up. The filter provided on average 20 to 25dB of improvement in interference margin.

With regards to mitigating blocking caused by LTE terminals, it is noted that power control within LTE terminals ensures that the devices are usually operating below their maximum power level, which provides mitigation in terms of the potential for blocking of DTT portable indoor receivers. This point was made in a contribution by the GSM Association to CENELEC in 2010,56 which suggested that whilst the maximum power of an LTE terminal is 23dBm, for most of the time the terminal will transmit at significantly less than its maximum output power.

Accordingly, it is not considered likely that interference from LTE devices to DTT receivers will cause significant problems in practice, and as agreed with NITA, we have not therefore explicitly modelled LTE uplink interference within this study.

56 GSM Association: Characteristics of mobile networks expected to be deployed in the 790–862

MHz band, contribution to CENELEC TC 210 WG 10 Meeting #3, 17-18 May 2010.

Conclusions and recommendations 91


7 Conclusions and recommendations

7.1 Summary of the main interference issues

Our initial analysis as described in Section 3 assumed that all LTE base stations transmit at their maximum licensed EIRP level. The purpose of this initial analysis was to establish whether interference from LTE to DTT could potentially be a problem.

Our conclusion from this initial analysis was that there is considerable potential for interference between LTE and DTT. Of the two interference modes considered (receiver overload, or blocking, and adjacent channel interference, or ACI), overload was found to be the dominant mechanism. With one LTE network

providing nationwide coverage, and with base stations operating at their maximum licensed power limit, we found that overload could potentially affect around 54 000 DTT households, approximately 2.3% of the total DTT households in Denmark. The deployment of three LTE networks (each using 2x10 MHz of

spectrum in the 800 MHz band) using maximum licensed EIRP at all sites has the potential to increase this number by a factor of around 2.8. For a scenario where three LTE networks operate nationally, with base station locations for each modelled on existing GSM900 network designs, and with all transmitting at maximum licensed power levels, the number of households suffering from DTT receiver overload could therefore be up to 150 000 of DTT households in Denmark.

Turning to ACI, our initial analysis using maximum EIRP at all base station sites suggested that around 5 600 DTT households within areas of the country receiving DTT services on Channel 60 could be affected by ACI from one LTE

network using the lowermost channels in the 800MHz band (i.e. FDD1). The cumulative effect of ACI from two LTE networks, one using blocks FDD1/FDD2

and one using blocks FDD3/FDD4, increases the number of DTT households affected from 5 600 to 7 600, located within areas of the country receiving DTT services on Channel 60. The cumulative ACI is dominated by the network using blocks FDD1/FDD2, since the increased frequency separation that exists from blocks FDD3/FDD4 will mitigate the ACI effect.

Our more detailed analysis in Section 4 considered interference effects in more detail and in particular took account of the effects of deploying more realistic EIRP levels at individual LTE base station sites. This analysis focussed on two areas of Denmark, one to the north of Copenhagen and the second around Ringsted-Sorø. By extrapolating those results nationally, our results show that use of realistic EIRP levels at LTE base station sites can reduce the number of households affected by interference significantly.

From our more detailed analysis, we found that ACI could affect more DTT households than receiver overload, which contrasts with our initial analysis where overload was thought to be the dominant issue.

Results from the more detailed analysis suggest that overload might affect between 2 500 and 3 000 DTT households nationally (from three LTE networks).



We also found that up to 2 000 DTT households might be affected by ACI within areas of the country receiving DTT services using Channel 59 (from one network

using blocks FDD1/FDD2)57.

For areas of the country using DTT Channel 60, we found that between 4 500 and 5 000 DTT households could receive ACI from an LTE network based upon the Network A configuration in our modelling.

It should be noted that Networks B and C resulted in a higher number of affected households (between 7 000 and 7 500) as a result of the increased coverage and additional base stations in those networks. However, it is noted that our nationwide extrapolation of results from the Ringsted-Sorø area should be viewed with caution, due to the specific characteristics of DTT coverage in that area, which we believe could be responsible for a greater proportion of households being predicted to be affected by ACI.

7.2 Conclusions on the suitability of different mitigation techniques

Overall, and assuming realistic EIRP levels are deployed at LTE base station sites, our results suggest that between 9 000 and 10 000 households might be at risk of interference from LTE to DTT::

Between 2 500 and 3 000 households nationally might be at risk of interference from receiver overload

Between 4 500 and 5 000 households might be at risk of interference from ACI in areas of Denmark receiving DTT services using Channel 60, and up to 2 000 households in areas using Channel 59

However, our study has also identified a number of practical means of mitigating interference effects for these potentially affected households.

Our analysis suggests the most practical, cost-effective means of mitigation appears to be installation of low-pass DTT receiver filters. Our estimates of the attenuation that can be achieved by a low-pass filter for Channel 60 (based upon information received from Braun Telecom for this study) are as follows:

from LTE FDD1 emissions, around 2dB C/I improvement

from LTE FDD2 emissions, around 5dB

from LTE FDD3 emissions, around 12dB

from FDD4 and above, more than 17dB.

Inclusion of an additional 5dB of attenuation within our modelling (relative to the realistic model where different base stations have different EIRP levels) causes a 73% reduction in the households affected by receiver overload, and the addition of 10dB attenuation causes an 95% reduction. For ACI, the percentage reduction is 65% for a filter providing 5dB of attenuation and 93% for 10dB of attenuation, for ACI within Channel 59 areas. For Channel 60 areas, we estimate that filtering

57 This is ACI to areas of the country receiving DTT using channel 59, since the area chosen for our more detailed analysis was to the north of Copenhagen, where DTT Channel 60 is not used.



providing 5dB of attenuation will only provide limited (less than 47%) reduction in households affected by ACI from FDD1, due to the limited frequency separation. We also note that LTE base station filters could also be used in combination with DTT receiver filters to reduce the out-of-band component of base station interference and therefore further reduce the number of households affected by ACI.

Other mitigation techniques can also be applied, to improve the DTT signal strength with respect to the LTE signal strength, thereby reducing the impact of interference. Examples include cross-polarisation and the use of on-channel repeaters. These techniques can be considered on a case-by-case basis since they cannot be applied throughout Denmark for various reasons, as described in this report.

We also note that improvement to current DTT receiver design could substantially reduce the potential for receiver overload and ACI. In particular, the measured results of overload threshold published in ECC Report 48 suggest that it is possible through current DTT receiver design to achieve an Oth of at least -5dBm, which will significantly improve the immunity of TV receivers to blocking from LTE signals. Measured PR values also show a 10 dB difference between the worst performing and the best performing receivers. Our estimate is that if all DTT receivers had an Oth of -5dBm for example, the number of Danish households at risk of receiver overload would reduce by 87% compared to an Oth of -15dBm).

It is feasible that a higher Oth limit could be specified within the standards for DTT receivers, to ensure that future models are designed with a higher threshold. This would not reduce the risk of receiver overload in the short term since the majority of households will already possess one or more digital receivers designed to today‟s standards. It would, however, reduce the risk of interference over the medium term, once households upgrade their receivers.

Denmark is unlikely to be able to implement such a change by itself since manufacturers design their products with markets much larger than Denmark in mind – typically for markets the size of the EU. Therefore, in order to implement such a higher Oth limit, Denmark would need to coordinate the proposed changes with other countries, or indeed with the European Commission. However, within Denmark it might also be possible to require manufacturers to make a clear declaration at the point of sale concerning the blocking performance of the receiver.

It is also noted that a few households within close proximity to LTE base stations could suffer higher levels of interference than predicted in our analysis, as a result of near-field radiation. Taking account of the households located within the near field of antennas from more than one network (based on existing 900 MHz base station locations), we estimate that the number of households within an LTE antenna near field is around 500 DTT households, which is therefore an extremely small proportion of DTT households nationally.

For the few remaining households for which no suitable means of interference mitigation can be found, it is possible that the only solution for blocking would be to change from DTT to an alternative platform (e.g. cable, IPTV or satellite).

Provision of targeted information to affected DTT households from LTE operators timed with the launch of new LTE800 base stations could also be helpful in alerting viewers to potential issues.



7.3 Recommendations

The following are the main recommendations from our study in relation to licensing of the 800MHz band:

Our analysis suggests that the number of households affected by receiver overload and ACI into DTT is substantially reduced if lower levels of EIRP (e.g. between 45 and 50 dBm) are used at individual base stations, rather than assuming that the maximum licensed level allowed is used at all sites. We expect that for a number of practical reasons operators will voluntarily deploy lower EIRP levels than the maximum licensed level at some base station sites – for example as a result of limits on the feasible size of base station antennas at urban sites, the effects sharing of antennas with 900MHz and associated feeder losses, use of transmit power control, etc. These various factors mean that mobile operators will optimise their networks individually taking account of base station locations and local traffic load. Accordingly, we do not believe that it is necessary to stipulate a lower licensed EIRP level within all 800MHz licences, since operators are expected to make use of lower powers voluntarily, and imposing a lower licensed limit could reduce operators‟ flexibility with regard to network deployment. However, it is noted that some additional EIRP limitations may need to be considered on use of the lowermost LTE block within areas of the country where DTT Channel 60 is used, given the higher proportion of potentially affected households in those areas. It is noted that the maximum licensed EIRP limit assumed in this report is 59dBm at most sites, or 56dBm at sites within areas using Channel 60. There is no specified maximum in-band EIRP limit in the EC‟s 800MHz decision, but the Decision suggests Member States may set limits and, unless otherwise justified, these limits would normally lie within the range 56–64dBm (for a 5MHz channel).

Considering possible mitigation techniques to restore DTT services in the presence of interference, filtering is the most obvious solution, although improvements to DTT receiver specifications over time could also provide an equally effective means of mitigating interference. Receiver filters could be used in affected areas in Denmark without affecting either the LTE or DTT network deployments. However, it is noted that the attenuation provided by filters is frequency-specific, and therefore there are likely to be few households within areas using Channel 60 for which filtering is not a practical solution. Additionally, LTE base station filters can be used in combination with DTT receiver filters to further improve mitigation against interference.

We have found that the effects of interference from receiver overload and ACI can also be mitigated by the use of vertically polarised LTE antennas (in contrast to the horizontal polarisation typically employed in DTT). However, the practicality of this solution is limited since, although most main DTT transmitters in Denmark use horizontal polarisation, the majority of DTT OCRs use vertical polarisation, meaning that the cross-polarisation gain of using vertically polarised LTE antennas cannot be realised. The use of vertically polarised antennas might also limit the flexibility of mobile operators to deploy LTE (given that slant antennas are in common use already, and use of MIMO techniques is expected to become more prevalent). Therefore, we recommend that operators are only encouraged to use vertically polarised antennas in areas where these are feasible and are demonstrated to provide a benefit in terms of reduced interference.



A further mitigation technique to improve DTT reception conditions is the installation of DTT OCRs. In some other European countries it is normal practice to operate OCRs on different channels to those of the main transmitters, as a means of avoiding interference within the DTT network. However, in Denmark OCRs typically re-broadcast using the same channel as the main repeater, but with vertical rather than horizontal polarisation. (This is the case because of the scarcity of broadcast channels in Denmark as a result of cross-border coordination agreements with neighbouring countries, which means that use of additional channels is generally not feasible.) Therefore OCRs need to be carefully planned to avoid interference within the DTT network. We recommend that further analysis and practical trials be undertaken into the feasibility of using additional OCR in selected areas in Denmark, particularly where households are located some distance from the nearest DTT transmitter, and therefore susceptible to ACI in particular.

In summary, we anticipate that following (voluntary) EIRP optimisation by LTE operators and the implementation of DTT receiver filters, the number of households still affected by blocking and/or ACI is likely to be small: up to a few thousand households. To fully assess this number would require further statistical (Monte Carlo-based) analysis. This would take account of the location of households within LTE cell areas, and consider the reduction in interference to households in the vicinity of the base station where the interfering signal level is highest for blocking. For these households there appears to be no further practical mitigation options for blocking, and therefore the best solution appears to be to provide an alternative TV platform (e.g. cable, satellite or IPTV).

96 Annex A: Blocking results


Annex A Blocking results by geo-type within Danish broadcast regions (initial analysis)

Table A.1 Households and area affected by blocking by broadcast region and geotype with 10dB filters [Source: Analysys Mason]


Broadcast region Affected

area (%

of total

area)

Affected

households

(% of total

area)

Affected

area (%

of total

area)

Affected

households

(% of total

area)

Affected

area (%

of total

area)

Affected

households

(% of total

area)

Anholt 0.0 0.0 0.0 0.0 0.5 0.0

Laeso 0.0 0.0 0.0 0.0 0.7 0.7

Tolne-Nibe 1.0 1.4 0.5 1.1 0.3 1.3

Viborg 1.2 0.8 0.0 0.0 0.3 1.3

Thisted 0.0 0.0 0.0 0.0 0.2 1.9

Videbaek 1.5 1.2 0.6 1.8 0.2 1.1

Hadsten +

Aarhus 2.1 2.1 0.6 2.5 0.4 1.7

Hedensted 1.2 1.2 0.5 1.8 0.3 1.4

Varde 0.8 0.3 0.6 0.5 0.2 1.2

Aabenraa 0.0 0.0 0.9 1.7 0.2 1.4

Tommerup +

Svendborg 1.1 0.7 0.6 0.5 0.4 2.1

Koebenhavn 1.5 1.6 0.7 1.8 0.4 1.5

Vordingborg +

Nakskov 1.5 0.7 0.7 1.5 0.3 1.6

Roe 0.0 0.0 0.0 0.0 0.7 2.6

Jyderup 0.0 0.0 0.6 1.6 0.4 1.3

Annex A : Blocking results 97


Table A.2 Households and area affected by blocking by broadcast region and geotype with 20dB filters [Source: Analysys Mason]


Broadcast region Affected

area (%

of total

area)

Affected

households

(% of total

area)

Affected

area (%

of total

area)

Affected

households

(% of total

area)

Affected

area (%

of total

area)

Affected

households

(% of total

area)

Anholt 0.0 0.0 0.0 0.0 0.0 0.0

Laeso 0.0 0.0 0.0 0.0 0.1 0.1

Tolne-Nibe 0.1 0.2 0.1 0.1 0.0 0.1

Viborg 0.1 0.1 0.0 0.0 0.0 0.2

Thisted 0.0 0.0 0.0 0.0 0.0 0.2

Videbaek 0.1 0.1 0.1 0.1 0.0 0.1

Hadsten +

Aarhus 0.2 0.2 0.1 0.3 0.0 0.2

Hedensted 0.1 0.1 0.0 0.1 0.0 0.2

Varde 0.1 0.1 0.1 0.0 0.0 0.1

Aabenraa 0.0 0.0 0.1 0.2 0.0 0.2

Tommerup +

Svendborg 0.1 0.1 0.1 0.1 0.0 0.2

Koebenhavn 0.2 0.2 0.1 0.2 0.0 0.2

Vordingborg +

Nakskov 0.1 0.1 0.1 0.1 0.0 0.2

Roe 0.0 0.0 0.0 0.0 0.1 0.4

Jyderup 0.0 0.0 0.1 0.1 0.0 0.1

98 Annex B : DTT site characteristics


Annex B : DTT site characteristics for Channels 60, 59 and 58 in Denmark

Table A.1 Site data for DTT Channels 60, 59 and 58 [Source: NITA]

Site Name Channel Longitude Latitude Antenna

height (m)

ERP

(dBW)

Polarisation

JYDERUP 60 11.46 55.69 311 43 H

KALUNDBORG 60 11.07 55.68 74 20 V

SKAMLEBAEK 60 11.42 55.83 78 14.8 V

NAKSKOV 60 11.20 54.87 159 40 H

VORDINGBORG 60 11.99 55.05 311 47 H

GLADSAXE 59 12.50 55.73 210 40 H

HELSINGOER 59 12.59 56.05 88 23 V

KOEBENHAVNVEST 59 12.24 55.72 311 47 H

SKODSB/LANDSKRONA 59 12.82 55.87 63 29 H

LYNETTEN 59 12.61 55.70 95 33 V

GUDHJEM 59 14.97 55.20 51 17 V

HAMMEREN 59 14.76 55.29 31 20 V

NEKSOE 59 15.13 55.08 52 26 H

PARADIS 59 15.11 55.09 40 17 H

ROE 59 14.89 55.16 309 36.5 H

SKIVE 59 9.05 56.57 100 17 V

VIBORGBY 59 9.45 56.47 97 17 V

VIBORG 59 9.24 56.46 309 47 H

LEMVIG 59 8.31 56.55 45 17 V

STRUER 59 8.60 56.49 62 17 V

VIDEBAEK 59 8.71 56.14 311 47 H

JYDERUP 58 11.46 55.69 311 47 H

KALUNDBORG 58 11.07 55.68 74 20 V

SKAMLEBAEK 58 11.42 55.83 78 14.8 V

NAKSKOV 58 11.20 54.87 159 40 H

VORDINGBORG 58 11.99 55.05 311 47 H

Annex C : Areas of interference 99


Annex C : Maps showing areas of interference (initial analysis)

Figure C.1 Areas of interference from blocking and ACI – initial analysis [Source: Analysys Mason]

100 Annex C : Areas of interference


Figure C.2 ACI from FDD1 to Channel 60 – initial analysis [Source: Analysys Mason]




102 Annex C : Areas of interference





Figure C.5 Blocking from LTE to DTT – initial analysis [Source: Analysys Mason]

104 Annex D : LTE link budget


Annex D : LTE link budget

The parameters used for the LTE link budget for 800MHz and a spectrum allocation of 10MHz are shown in the tables below:

Table D.1 LTE link budget for downlink [Source: Analysys Mason]

Downlink

BS Transmit Power dBm 44.0

Number of transmit antenna elements # 1.0

Number of receive antenna elements # 1.0

BS Antenna gain dBi 15.0

BS Diversity Gain / MIMO Gain dB 0.0

BS Feeder and Connector Losses dB 4.50

BS EIRP dBm 54.5

Data rate Mbit/s 8.00

Nearest performance step Mbit/s 8.13

Required SNR dB 4.01

Thermal Noise PSD dBm/Hz -173.98

Number of resource blocks # 50

Bandwidth per resource block MHz 0.18

Bandwidth for the number of resource blocks MHz 9.00

Thermal Noise for required bandwidth dBm -104.43

UE Noise Figure dB 7.0

UE Receiver Noise Floor dB -97.4

UE Interference margin dB 4.0

UE Sensitivity dB -89.4

Control channel overhead dB 0.4

UE Antenna Gain dBi 0.0

UE Diversity Gain / MIMO Gain 0.0

UE Body Loss dB 0.0

UE Required Signal Power dBm -89.0

Downlink Path Loss dB 143.5

Annex D : LTE link budget 105


Table D.2 LTE link budget for uplink [Source: Analysys Mason]

Uplink

UE Transmit Power dBm 23.0

Number of transmit antenna elements # 1.0

Number of receive antenna elements # 1.0

UE Antenna Gain dBi 0.0

UE Diversity Gain / MIMO Gain 0.0

UE Body Loss dB 0.0

UE EIRP dBm 23.0

Data rate Mbit/s 2.05

Nearest performance step Mbit/s 5.28

Required SNR dB 1.00

Thermal Noise PSD dBm/Hz -173.98

Number of resource blocks # 25

Bandwidth per resource block MHz 0.18

Bandwidth for the number of resource blocks MHz 4.50

Thermal Noise for required bandwidth dBm -107.44

BS Noise Figure dB 5.0

BS Receiver Noise Floor dBm -102.4

BS Interference margin dB 1.0

BS Sensitivity dBm -100.4

Soft handover gain dB 0.0

Fast fade margin dB 0.0

BS Antenna gain dBi 15.0

BS Diversity Gain / MIMO Gain dB 0.0

BS Feeder and Connector Losses dB 4.5

BS Required Signal Power dBm -110.9

Uplink Path Loss dB 133.9

106 Annex E : Modelling steps


Annex E : Summary of modelling steps

The first step was to imported site data for the DTT network in Denmark from the ITU-R GE-06 agreement, as provided by NITA, into our radio planning tool.

IRT-2D

Figure E.1 Sites from ITU-R GE-06 data being imported into the radio planning tool [Source: Analysys Mason]

We then identified sites using DTT Channels 58, 59 and 60, which is of interest for the ACI analysis. All DTT sites are used for the blocking analysis.

Annex E : Modelling steps 107


Figure E.2 DTT sites, with those using Channels 58, 59 and 60 highlighted [Source: NITA, Analysys Mason]

The next step was to import the DTT wanted field strength maps provided by the two Danish broadcasters into our radio planning tool. The coverage map for MUX1 is shown in Figure below.



Figure E.3 Coverage maps from broadcasters imported into the radio planning tool [Source: Analysys Mason]

A network of LTE sites was then added to the model, in line with the description provided in the main report, using 30-metre high base stations with an assumed Kathrein antenna pattern, from which we have identified sites falling within each of the DTT broadcast areas of interest.



RuralSuburban

Urban

Figure E.4 Illustration of theoretical LTE network [Source: Analysys Mason]

To ensure that appropriate antenna discrimination was included in our analysis, we have performed a „best server‟ prediction within our planning tool to identify which DTT site best serves each household. In doing so we also identified the households within areas covered by DTT Channels 58, 59 and 60 of interest in the ACI analysis.



Figure E.5 Configuring receivers to the best server [Source: Analysys Mason]

The final stage in the modelling is to calculate the number of households covered by the DTT network, firstly without and then with LTE ACI or blocking added. This makes use of the KMS household data set for Denmark, using Map Info to calculate the households located within selected areas. This household dataset also includes summerhouses within Denmark as well as „permanent‟ residences.



Figure E.6 Summation of households within coverage area with interference [Source: Analysys Mason]

For our analysis of realistic EIRP levels at individual sites, we additionally performed a number of coverage optimisation steps to assign a unique EIRP level at each site consistent with the calculated site separation between the site and its nearest neighbour.

Figure E.7 Best server coverage – Network A [Source: Analysys Mason]



Figure E.8 Best server coverage – Network B [Source: Analysys Mason]

Figure E.9 Best server coverage – Network C [Source: Analysys Mason]

Documents

800MHz auction: Co-existence of LTE systems in 790-862 · PDF file800MHz auction: Co-existence of LTE systems in 790-862 MHz with Digital Terrestrial Television - August 2011 Contents