Use of MHA on UMTS

OrangeTechnical CoE Radio AccessProject 9

Use of MHA for UMTS v1_final.doc - 21/08/02 17:08:00 - 1/26 -

USE OF MHA

ON UMTS VERSION 1.0

COMPANY CONFIDENTIAL

Object, short description :

Approved by : Level :Date :N. of pages : Ref : COE_PROJECT_9History :Version Date Authors Comments

1.0 21 Aug. 2002 Benoit Graves, Henk Tubbe First Released version



Table of contents

1 Executive Summary 3

1.1 Scope & Overview 3

1.2 Conclusions & recommendations 3

2 General physical description 4

3 Noise Figure calculation 4

3.1 Friis’ formula 4

3.2 Noise Factor improvement 5

4. Effect of external noise on the link budget with MHA 7

4.1 Case without MHA 9

4.2 Case with MHA 9

4.3 Comparison between 2 cases 10

5. Practical examples of external noise 11

5.1 Spurious emission / inter-modulation 11

5.2 Adjacent interference / Dead Zone 12

5.3 External noise due to repeaters 14

5.4 Blocking 15

6. Coverage and Capacity impacts 17

6.1 Increase of UL coverage / data-rate 17

6.2 Increase of UL capacity 18

6.3 Loss of DL capacity 196.3.1 Decrease of max output power 196.3.2 Maximum Average Pathloss 196.3.3 Common Channel setting 20

6.4 Note on feeder types 22

7. Strategy of non-homogeneous MHA use 23

7.1 Introduction 23

7.2 Theoretical analysis 23

7.3 Parcell 3G simulations 24

7.4 Conclusion on non-homogeneous use 26

8. Conclusion 26

9. References 26



1 Executive Summary

1.1 Scope & Overview

The goal of this document is to describe the concepts and issues regarding the use of MHAs on aUMTS network. The content will be focused on the radio issues; the O&M aspects will not be tackledin the present document.

1.2 Conclusions & recommendations

• The main interest of designing MHAs on the network is to improve the coverage andpossibly reduce the number of sites. In this document, different scenarios have beenassessed. Typically with 3 dB of feeder loss, we can expect a 3 dB sensitivity improvement.

• MHA’s can induce a slight loss of DL capacity as well as an important gain in UL capacity.

• MHAs do not require higher protection against external noise such as spurious emissions,inter-modulation, adjacent interference or desensitisation due to repeaters. Nevertheless,its improvement would be lower if a disturbance was encountered.

• MHAs can even give better protection against blocking through its severe filteringcapabilities.

• Optimum improvement is experienced when MHAs are designed homogeneously on allsites.



2 General physical description

The MHA is an active element that increases the sensitivity of the reception chain. The way toaccomplish this is to reduce the global Noise Factor (NF) of the reception chain. On the downlinkdirection, the insertion loss of the unit is typically less than 0.4 dB.

Duplexer

Duplexer

UplinkDownlink

Antenna

Node B

Gain=12dBNF=2dB DL Insertion loss = 0.4 dB

Figure 1: Physical description of a typical MHA.

3 Noise Figure calculation

3.1 Friis’ formula

DemodulatorReception chainSin

Nin

Sout

Nout

Figure 2: Reception chain model

Any reception chain not only amplifies or attenuates the signal (depending on the elements thatform it) but also introduces noise. This yields in a difference between the S/Nin and the S/Nout.



This difference is called Noise Factor (NF) and is defined as:

( )( )

out

in

NS

NS

NF = (always ≥ 1)

Equation 1: Noise Factor definition

Knowing that any element of a reception chain can be defined by its noise factor (NF) and its gain (G),the NF of a chain of n elements can be obtained as:

∏−

−++−+= 11

21

11n

ii

nTotal

G

NFG

NFNFNF K

Equation 2: Noise Factor calculation for a chain of elements, known as Friis’ formula

3.2 Noise Factor improvementAs we have seen in the previous paragraphs, every single element of a chain contributes to the globalnoise factor of the chain. It has also been said that the introduction of an MHA can improve theperformances of the reception chain by decreasing the global Noise Factor. In this paragraph wecalculate this benefit to evaluate the convenience of the installation of an MHA on a Node B site.In Figure 3 we see the elements forming the reception chain of a Node B site without MHA. As we canobserve, every single element is defined by its NF an its G.

Node BCable *

* Includes top and bottom jumpers

Gcable

GNode B

NFcableNFNode B

Figure 3: Elements of a reception chain without MHA

Using Equation 2 and knowing that the NF of a passive element equals:

GLNF 1==

Equation 3: Noise Factor of a passive element

The NF of the chain yields:

BNodecablecable

BNodecableTotal NFL

G

NFNFNF ⋅=

−+=

1

The same calculation can be made for a reception chain with MHA (c.f. Figure 4).



TopJumper MHA Node BCable *

* Includes jumper between feeder andMHA and bottom jumper

Gt_jumpGMHA Gcable

GNode B

NFt_jump NFMHA

NFcableNFNode B

Figure 4: Elements of a reception chain with MHAMHA

The noise factor of the chain inFigure 4 equals:

−⋅+=

−

+−

+=

MHA

BNodecableMHAjumptTotal

cable

MHA

BNode

MHA

cableMHAjumptTotal

G

NFLNFLNF

LGNF

GL

NFLNF

1

11

_

_

The standard values for these variables are:

Element Lt_jump NFMHA GMHA Lcable NFNode B

Value (dB) 0,3 2 12 Depends on length 3,0

Remarks:• Losses Top Jumper = 1 m*1/2_Flex + 2 connectors = 1*18/100 + 2*0,05 = 0,28• NF_MHA: typical value 1.7 dB, guaranteed value: 2 dB (over temperature range)

The chart below shows the improvement on the Link Budget thanks to the use of MHAs.As seen, the greater the cable losses, the greater the interest of using an MHA.



Gain with MHA / cable loss

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

Cable loss (dB)

dB

m

NF with MHA

NF without MHA

Link Budget gain with MHA

4. Effect of external noise on the link budget with MHA

The goal of this part is to explain the theoretical effect on the link budget of an external disturbance,such as adjacent interference or noise generated by a repeater.

Let us first have the general understanding of the effect:

recN : Noise from the receiver system, which equals thermal noise multiplied by NF_total.

Hence recN with MHA < recN without MHA.

extN : External noise

Total received noise can be expressed as:

extrectotal NNN +=

Hence if extN >> recN , then exttotal NN ≈

We have to assess the term ‘external in-band noise’:

It is the resultant noise from all external sources other than MAI from own system users. It will emanatefrom spurious generated by UEs and BSs of other systems (GSM, TDD, other FDD operators, etc) plusthe effects of blocking from carrier energy from other systems (especially in co-located site-sharing andmicro/pico cell environments).



Two conclusions can be made:

1) As the external in-band noise increases, the internal system noise generated by the receiver,becomes neglegible compared to the external noise.

As a consequence, the higher the external spectral in-band noise, the less beneficial an MHAbecomes.

High levels of external in-band noise will be most likely in micro/pico cell environments where theMCL between BSs and UEs is much lower than in the macro-case. Here deployment of MHAswill not be needed because the link budget doesn’t require such high sensitivity.

2) totalN with MHA < totalN without MHAAn external disturbance is never worse with a MHA.

M H A

A N T E N N A

F E E D E R

N O D E B

S _ n o d e _ b

S e n s _ I n

S e n s i t i v i t y w i t h N o i s e I n c r e a s e

Values:

Sens_In = sensitivity defined between the antenna and the reception chain.Sens_Node_B = Sensitivity defined at the Input of the Node BS, N: Signal and Noise between the antenna and the reception chain. Case without MHA.S’, N’: Signal and Noise between the antenna and the reception chain. Case with MHA.



k: Boltzmann constantT: noise temperatureB: receiver bandwidth

recN : noise from the receiver

extN : external noise

When comparing sensitivities with and without MHA, we refer to the equivalent sensitivity BEFORE thereception chain (i.e. at the antenna input). That is on the drawing: Sens_In.

4.1 Case without MHAThe noise received at the antenna input is:

extBNodecableextcable

BNodecable

extsystemextrecTotal

NNFLkTBNG

NFNFkTB

NNFkTBNNN

+××=+−

+×=

+×=+=

⋅ )()1

(

)(

The sensitivity at the antenna input is:

( ) NBandwidthNrateBitENNSInSens bTotal ×××=×= )/_(/_ 0min Total

Totalb NgainSpreadingNEInSens ××= _/1)/(_ 0

With: Spreading_ gain = chip rate / user bit rate = spreading factor x coding gain

4.2 Case with MHAThe expression with the MHA is almost identical as above, except for N total.BEWARE that the Noise and Sensitivity are both expressed at the antenna input and not at the Node Binput.

extsystemextrecTotal NNFkTBNNN +×=+= )(

If we refer to the part 2.3, we have:

−⋅+=

MHA

BNodecableMHAjumptSystem G

NFLNFLNF

1_

Then:

extMHA

BNodecableMHAjumptTotal N

G

NFLNFLkTBN +

−⋅+×=

1_

The sensitivity has the same expression as without MHA, the only change is N total.



4.3 Comparison between 2 cases

The difference between sensitivities equals the difference between noises:

Sens_In(with MHA) – Sens_In(without MHA) = N(with MHA) – N(without MHA)

Referring to the same MHA figures as before and 3 dB of cable losses, here are computed valuesshowing the effect of different external noise levels on the total noise received by the system:

Noise level (dBm)Total noise with MHA (dBm)

Total noise without MHA (dBm)

Noise_with_MHA - Noise_without_MHA (dB)

-160.0 -104.58 -101.16 -3.42-155.0 -104.58 -101.16 -3.42-150.0 -104.58 -101.16 -3.42-145.0 -104.58 -101.16 -3.42-140.0 -104.58 -101.16 -3.42-135.0 -104.57 -101.15 -3.42-130.0 -104.57 -101.15 -3.42-125.0 -104.54 -101.14 -3.40-120.0 -104.46 -101.10 -3.36-115.0 -104.20 -100.98 -3.22-110.0 -103.48 -100.62 -2.86-105.0 -101.77 -99.66 -2.12-101.2 -99.56 -98.17 -1.39-100.0 -98.70 -97.53 -1.17-95.0 -94.55 -94.06 -0.49-90.0 -89.85 -89.68 -0.17-85.0 -84.95 -84.90 -0.06-80.0 -79.98 -79.97 -0.02-75.0 -75.00 -74.99 -0.01

Noise_with_MHA - Noise_without_MHA (dB)

-4.00

-3.50

-3.00

-2.50

-2.00

-1.50

-1.00

-0.50

0.00-140.0 -130.0 -120.0 -110.0 -100.0 -90.0 -80.0 -70.0 -60.0 -50.0 -40.0

Noise level (dBm)

Dif

fere

nce

(dB

)



CONCLUSION:The benefit of the MHA decreases as the external noise increases and in the worst case the sensitivity ofthe total system with MHA equals the one without MHA. Even if the MHA amplifies the noise, thesensitivity with the MHA never gets worse than the one without MHA. The reason is that the usefulWCDMA signal is also amplified with the same gain as the noise.

5. Practical examples of external noise

5.1 Spurious emission / inter-modulation

We will focus our attention on the case of spurious emissions. For inter-modulation the results aresimilar.

Defining:• { }dBmspurious : Noise level received by spurious emissions at the antenna input

• { }dBisolation : Required path loss between the spurious emitter and the receiver antenna input

• { }dBtimprovemenmha _ : Gain on the link budget with the use of MHA

Co-siting rules will state:

{ } { } { } { }dBdBmrecdBmdB inmNspuriousisolation arg+−>

With:{ } ( ) { }

dBsystemdBmrec NFBkTN += 0log10

Sensitivity for Speech with and without MHA / Noise level

-130.00

-120.00

-110.00

-100.00

-90.00

-80.00

-70.00

-60.00

-160.0 -140.0 -120.0 -100.0 -80.0 -60.0 -40.0

Noise level

Sens_In(without MHA)SpeechSens_In(without MHA)Speech



The additional margin is set for a given desensitisation. Commonly we use 10 dB of margin,corresponding to 0.4 dB of desensitisation. The relationship between the margin and the desensitisationis:

{ } { } )101log(10 10/arg dBinmdBationdesensitis −+=

A clear consequence is that as the NF with MHA is better than the NF without MHA, the isolationrequired to avoid spurious emission disturbance at the NodeB receiver is higher in the case with MHA.

There are 2 possibilities for the operator:

1) Increasing the isolation requirement:

If we compare the effect of spurious emissions with and without MHA on the receiver system:

{ } { } { }dBdBdB timprovemenmhamhawithoutisolationmhawithisolation _____ =−

In other words if the mha_improvement = 3 dB, the isolation requirement increases by 3 dB.

2) Keeping the same isolation and allowing a higher desensitisation or a smaller MHA improvementIn this case:

{ } { } )101log(10 10/_arg dBtimprovemenmhainmdBationdesensitis −−+=

In other words: if the margin is 10 dB and the mha_improvement 3 dB, the desensitisation with MHAreaches 0.8 dB instead of 0.4 dB. The MHA improvement on the link budget is reduced from 3 dB to 2.6dB.

5.2 Adjacent interference / Dead Zone

Referring to several documents on Dead Zone (FTR&D/DMR/URF/01.0326/JPD & FTR&D/DMR/IIM/01.0368/BS, Frequency block choice V0.9), we can formulate the adjacent interference in UL as:

ULA

UEuladj ACIRCL

PI

1._ =

with: BSUEUL ACSACLRACIR

111+=

Definitions:ACIR: Adjacent Carrier Interference RatioACLR: Adjacent Channel Leakage RatioACS: Adjacent Channel SelectivityCL: Coupling Loss between the interferer UE and the antenna inputPue: UE power



In the case of MHA, the adjacent interference can be expressed as:

MHA

adjMHA

BSA

UE

ULA

UEuladj G

G

ACSCLP

ACLRCLP

I __

11××+×=

or MHA

adjMHA

BSUEUL G

G

ACSACLRACIR_111

×+=

Case 1: use of a MHA with 60 MHz of bandwidth

In this case, adjacent frequencies are amplified at the same level as in-band frequency, hence:

MHAadjMHA GG =_

BSA

UE

UEA

UEuladj ACSCL

PACLRCL

PI

1.

1._ +=

the formula is strictly identical to the one without MHA.

Then the analysis is similar to the one with any external noise, which means that with the sameradio configuration (interferer UE at the same location), we will have a slightly higher desensitisation or asmaller link budget improvement with the MHA.Which means that the Dead Zone area is slightly larger with fullband 60 MHz MHAs.

By dead zone area, we mean the area where the interferer UE may disturb a NodeB at a certaindesensitisation level.

Actually if the mha_improvement on the link budget is 3 dB, the Max CL for the adjacent interferer is3 dB higher.

Case 2: use of a MHA with 15 MHz of bandwidth

Theoretically, uladjI _ is slightly lower as MHAadjMHA GG <_ (the MHA filters adjacent frequencies)

Numerical application:

For the 15 MHz MHA, we will take the Orange Group RFQ MHA specifications:

MHA

adjMHA

G

G _= -3 dB at +/- 5 MHz

Case 1: 3GPP standards give at +/- 5 MHzo UEACLR =33 dB

o BSACS = 45 dB

Then:ACIR (60 MHz MHA) = 32.73 dBACIR (15 MHz MHA) = 32.86 dB

-> The dead zone area is reduced by 0.13 dB with the 15 MHz MHA.



Case 2: if we consider more optimistic figures for the UE (ex: UEACLR =42 dB)

ACIR (60 MHz MHA) = 40.2 dBACIR (15 MHz MHA) = 41.0 dB

è The dead zone area is reduced by 0.8 dB with the 15 MHz MHA.

5.3 External noise due to repeaters

RepeaterNode B+ MHA

Path Loss (donor antenna + air interface +site antenna)

Grep

PLNFrepNFTotal

In any receiver system, with or without MHA, a repeater within the cell coverage may yield adesensitisation at the Node B level, which depends on the “external noise” received from the repeater.

Considering the same model as before, we have:

extsystemextrecTotal NNFkTBNNN +×=+= )(

Where: PLGNFkTBN reprepext /××=

The desensitisation can be expressed as:

system

ext

rec

ext

NFkTBN

NN

repwithoutNrepwithN

ationDesensitis×

+=+== 11)_(

)_(

As systemNF (with MHA) < systemNF (without MHA), then:

)_()_( MHAwithoutationDesensitisMHAwithationDesensitis >

When integrating a repeater within the coverage of cell with MHA, the desensitisation of the NodeB willbe higher than if this cell had no MHA installed. Nevertheless, cell coverage will still be better than if thecell had no MHA installed.



5.4 Blocking

The case of blocking differs from the previous external noise model, as blocking is an out-of-banddisturbance.

First of all, the MHA itself has “blocking” requirements linked to the saturation of its amplifier.The maximum possible input power at the MHA amplifier is dictated by its “1 dB output compression”value. The higher this value, the higher input power the amplifier in the MHA can handle before goinginto 1dB compression of the output signal.

Let us take an example:

Max Input Signal = -7 dBm

Gmha=12 dB

1 dB comp point = 7 dBm

Node B

Duplex Filter

Node B Blocking = 16 dBm

System Blocking level = Max InputSignal - Filter Rejection = 53 dBm

1. UMTS level Blocking at Node B = 16 dBm (by GSM900/GSM1800/UMTS) – rel. 2000 compliant

As the 1 dB output compression point defined in the Group MHA RFQ [2] is 7 dBm, the 16 dBmblocking level cannot be reached at the NodeB.

Hence the limiting element could be the LNA in the MHA unit.

• For the MHA amplifier: Max_input_signal = 1 dB compression point – Gmha = 7 – 12 = - 5 dBm.• As the duplex filter rejects the out-of-band signals, a higher maximum level can be allowed at the

MHA input.

+

LNA



Its value is given by:

System_Blocking_level(f) = Max_input_signal + Rejection(f)(f being the frequency)

Let us take the Orange Group RFQ MHA specifications:

• Rejection of GSM900 (DL): > 60 dB• Rejection of GSM1800 (DL): > 60 dB• Rejection of UMTS FDD (DL): > 70 dB

In the worst case (GSM1800), the blocking level of the MHA is:

System_Blocking_level = -5 + 60 = 55 dBm.This value is far above the Node B blocking value, hence blocking from other operators shall not bean issue. Moreover, blocking from co-locating GSM equipment should not occur since a receivedsignal of 55 dBm is extremely high compared to the the given maximum output power of theGSM/DCS BTS.

2. UMTS Node-B receiver Blocking – desensitisation issue

The in-band receiver blocking performance of the BS is –52 dBm in adjacent channel and –40 dBmfor a 10 MHz offset. At these levels the 3GPP standard allows 6 dB desensitisation. This in-bandperformance is achieved by IF filtering in the BS receiver since the RF front end is indeed wide-band(ie 1920 – 1980 MHz).The out-of-band blocking performance is increased simply because it is possible to add RF filteringthat reduces the interfering signal levels to the same value as the in-band value. Eg if the filter adds60 dB rejection at a particular out-of-band frequency then the blocking level at that frequency wouldbe 60 dB greater than the in-band blocking level (say –40 + 60 = + 20 dBm) To put it another waythe out of signal at + 20 dBm would cause the same desensitisation (= 6 dB) as an in-band signal at10 MHz offset at a level of – 40 dBm.

In either case (in-band or out-of-band), the level at which the BS is desensitised by 6 dB is –40 dBmwhich is 53 dB less than the 1 dB compression point of the LNA. This means that for UMTSinterferers the BS blocking performance is the dominant parameter (not the LNA in MHA) andthat the selectivity provided by the 15 MHz band selective MHA will have a significant impacton the in-band blocking performance of the MHA/BS combination.

MHA filters add additional rejection within the UMTS band (substantially improving in-band blocking) and will also add some extra out-of-band making the total system out-of-band blocking even better.

3. Case of TDD rejection:

As the TDD band is closer to the FDD UL band, a lower rejection can be reached. In the worst case, ifthe TDD band is adjacent to the FDD band, the rejection will only be between 0 and 3 dB…Nevertheless numerous uncertainties remain on the TDD use, its standard is not defined and it is notclear today that TDD sites will be co-located with FDD sites. Furthermore, studies concerning TDD/FDDco-siting need to be conducted in the future to confirm if the MHA specifications provide sufficientrejection to TDD.



6. Coverage and Capacity impacts

6.1 Increase of UL coverage / data-rate

• For each service, the use of MHAs results in a better link budget in UL, hence a better coveragewhen the system is limited by the Uplink.

With standard MHA figures we reach the following improvements depending on cable losses:o Cable losses = 3 dB -> mha_improvement = 3.2 dBo Cable losses = 4 dB -> mha_improvement = 4.1 dB

The improvement on link budget can be understood with different views:

o Same service, same indoor -> larger cell range.In this case we can design the network with a larger inter-site distance and reduce thenumber of sites.The impact in terms of dimensioning will be different for each operator. Coverage targets,operational constraints such as site re-use, propagation model and predictions will lead tototally different dimensioning results.However two main situations may be encountered:

1) Greenfield operator.In this case, the intersite distance can be reflecting the increase of cell range due to theimproved uplink link budget. In terms of dimensioning, reduction of the number of sites isoptimum. With MHA, from 30 to 40% fewer sites could be needed.

2) Existing GSM networkRe-using GSM sites for the UMTS network infers less flexibility than in the case of aGreenfield operator. As the existing inter-site distance would very unlikely match thecalculated one, dimensioning would be more a question of adding more or less sites to fillup coverage holes.In this case, the reduction of the number of sites may vary drastically from oneoperator to another. Dimensioning based on a simulation tool is highlyrecommended to obtain a realistic estimation.Basic figures would give 10 to 50% fewer sites with MHAs on all sites.

o Same service, same inter-site distances -> better indoor.In this case we plan the network with the same sites as without MHA and we will have adeeper indoor penetration for each service (for instance from 15 dB to 19 dB).

o Same indoor, same inter-site distances -> better data-rate.At a defined location the UE will be able to reach higher bit-rates thanks to the MHA. Typicallyif only 144 kbits/s were available, the MHA will make possible 384 kbits/s (there is around 4dB difference between 144 and 384 link budgets).

• High data rate services will probably take a greater benefit from the extension of coverage thanlow data-rate. Usual traffic distributions as function of path loss have a “bell-like” shape,(Gaussian distribution) with a larger density of traffic at average path loss. This is not true when ahot-spot is located at cell edge, however on most mature networks this case rarely occurs.In other words a smaller part of mobiles would be found at large path loss (e.g. where onlySpeech is provided) than at lower path loss (e.g. where 384 is provided). Hence a 3 dB extensionof coverage will probably mean a potential to reach more 384 users than Speech users.



• When the cell coverage is limited by the Downlink, the MHA does not improve the link budget.However it seems important to stress a few points on DL limited cells:

o A cell coverage would probably be limited in DL only during Busy Hours. At low load thecell will still be limited by the UL. Hence the MHA could be useless for 30 minutes andthen useful for 23 hours and 30 minutes…

o Except if designed as a hot-spot site, a cell limited by DL will unlikely be suitable and willrequire a capacity upgrade. Depending on vendor features, additional frequency, TX-diversity or high-power Power Amplifier can be added to cope with the increase of cellload. If so the cell will be UL limited again.

6.2 Increase of UL capacity

MHA can either increase UL coverage or increase UL capacity. To be precise MHA can improve bothsimultaneously but at lower levels. The next chart displays the dual effect of MHA:

For a given maximum path loss in the cell, more UEs can be admitted if the cell has a MHA than noMHA. In other words if the cell load limit of the cell without MHA was 50%, the maximum cell loadwith a MHA can increase up to 70-75%.

This UL capacity gain has been assumed considering no noise level increase, however there will bean increase of noise degrading the UL capacity gain. This effect needs to be investigated duringOrange Engineering Network Tests.

Impact of MHA on UL coverage and capacity

Without MHA : 690 kbps

With MHA : 1,050 kbps

110

115

120

125

130

135

140

145

- 200.00 400.00 600.00 800.00 1,000.00 1,200.00 1,400.00

Throughput (kbps)

Pat

h L

oss

(d

B)

Uplink Capacity LCD384 without MHA Uplink Capacity LCD384 With MHA

+ 52 % UL capacity

+ 3 dB UL coverage



6.3 Loss of DL capacity

6.3.1 Decrease of max output power

There is slight reduction of the station max output power (given at the antenna input) due to theinsertion of the MHA. Actually there are 2 losses:

o MHA Insertion Loss (typically 0.4 dB)o Top jumper losses (between the antenna and the MHA). With 1m of ½ flex (18 dB

loss/100m) + 2 connectors (0.05 dB loss each), the loss is: 0.28 dB

Hence the global loss in DL is around 0.7 dB. Impact on capacity loss is low:in the following example with mono-service Speech, the DL capacity loss is around 3%.

6.3.2 Maximum Average Pathloss

There is slight increase of the max average pathloss of the cell.As the UL cell range is larger than without MHA, there will be a higher probability to have high pathlosses in the cell, which infers a loss of DL capacity.

• For mobiles within the coverage area without MHA, adding a MHA does not modify the DL powerneeded for the DL (except compensation for the insertion/jumper loss).

• For mobiles located in the extra UL coverage provided by the MHA, the corresponding DL levelrequired to reach the mobile in DL is higher than the highest required when without MHA. In other

Impact of the MHA insertion loss on DL capacity

-3.17%

100

110

120

130

140

150

160

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00

Throughput (Kbps)

Pat

h L

oss

(dB

)

-16.90%

3.10%

23.10%

43.10%

63.10%

83.10%

20W_1_Carrier_No_TxDiv Downlink N Users Speech


Gain



words, the Max path loss being higher (e.g. +3 dB), the DL level required for the very edge of thecell is Max_DL_Power + 3 dB.However, the traffic part on the edge of the cell is usually low, it is therefore very unlikely that theaverage path loss is increased by 3 dB. A more realistic value could be around 1 dB. Only whena high traffic area is reached thanks to the MHA gain, the DL capacity loss could be a concern.

Following chart: example of DL capacity loss with 1 dB increase of average path loss (taken formono-service Speech). Note that results are similar with other mono-services or with a multi-service distribution.

6.3.3 Common Channel setting

Referring to [1] the required common channel power levels can be calculated as a function of:• Orthogonality factor (set to 0.4)• Interference factor (set to 2)• Max BS power (43 dBm without MHA, 42.3 dBm with MHA)• Maximum Path Loss (set to 140 dB without MHA, 143 dB with MHA)

The following tables show the requested Common Channel power with and without MHA:

120

130

140

150

160

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00

Mono-service - Speach : Throughput (Kbps)

Pat

h L

oss

(d

B)

DL Capacity loss = -3,5%

Av. Path Loss = + 1 dB



The common channel power is driven by the service with the largest UL coverage, that is to say Speech.In this example we have taken as Maximum Path Loss for Speech: 140 dB. If the cell has a MHA the ULcoverage for Speech may reach a Max Path Loss of 143 dB. To benefit from this 3 dB extension of ULcoverage the common channel power will need to be increased.Note however that there is no need to increase the power by 3 dB to match the 3 dB increase of ULcoverage.

With a calculation on all common channels, the following chart (produced by an internal tool) displays thecapacity loss for a given average path loss. In this case (mono-service speech), we would have 8.5%loss of DL capacity.

Note that the capacity loss is linked to two reasons:• Decrease of the Max output power (from 43 dB to 42.3 dB)

Common channels without MHACPICH P-CCPCH S-CCPCH SCH PICH AICH

Orth Factor 0.4 0.4 0.4 0.4 0.4 0.4I_inter/I_intra 2 2 2 2 2 2No (dBm) -100 -100 -100 -100 -100 -100C/I (dB) -15 -17 -17 -17 -20 -20P_Node_B (dBm) 43 43 43 43 43 43Max PL (dB) 140 140 140 140 140 140P_Channel (W) 1.81 1.15 1.15 1.15 0.58 0.58P_Channel (dBm) 32.57 30.59 30.59 30.59 27.61 27.61P_Channel (%) 9.06% 5.74% 5.74% 5.74% 2.89% 2.89%Activity factor 1.00 0.90 0.25 0.10 1.00 0.80Total CCH power (W) 4.28Total CCH power (dBm) 36.31CCH power share 21.44%

Common channels with MHACPICH P-CCPCH S-CCPCH SCH PICH AICH

Orth Factor 0.4 0.4 0.4 0.4 0.4 0.4I_inter/I_intra 2 2 2 2 2 2No (dBm) -100 -100 -100 -100 -100 -100C/I (dB) -15 -17 -17 -17 -20 -20P_Node_B (dBm) 42.3 42.3 42.3 42.3 42.3 42.3Max PL (dB) 143 143 143 143 143 143P_Channel (W) 1.90 1.20 1.20 1.20 0.60 0.60P_Channel (dBm) 32.78 30.80 30.80 30.80 27.82 27.82P_Channel (%) 11.16% 7.08% 7.08% 7.08% 3.56% 3.56%Activity factor 1.00 0.90 0.25 0.10 1.00 0.80Total CCH power (W) 4.49Total CCH power (dBm) 36.52CCH power share 26.42%



• Increase of the common channel power share (from 21.5% to 26.5%)

However, it is not compulsory to tune up the Common Channel power share and the operatorshave the choice between 2 scenarios:

• Scenario 1

The operator increases the power to balance the extension of coverage for all services.Then for a 3 dB improvement with MHA, the loss of DL capacity is between 5 and 10%.

• Scenario 2

The operator does not tune up the CCH power. Then there is no loss of DL capacity (except the one dueto a lower output power), however the extension of coverage will not be effective for all services;services with the highest path loss not being overlapped by CCH coverage. For instance, the CCHpower is tuned to match Speech coverage without MHA (i.e. Max PL = 140 dB). In this case, the CCHcoverage will not overlap (or with poorer quality) the extended Speech coverage in the path loss range of140 to 143 dB.To summarize:

• Speech: no overlap by common channels hence no extension of UL coverage.• LCD 64, 144, 384: still overlap by common channels hence extension of coverage.

6.4 Note on feeder typesConsidering the Uplink Budget it would be possible to increase the feeder losses without degrading theglobal noise factor, and thus the coverage, since the Noise Factor with MHA is quite steady when relatedto feeder losses. Thinner sections of feeders (e.g. 7/8’’ instead of 1’1/4’’) could be used for same feederlengths. But in this case we would decrease the DL as well, which means a loss of DL capacity.

Hence we DO NOT recommend modifying the rule on feeder type depending on feeder lengths.

DL capacity loss with CCH power share increase

-8.55%

100

110

120

130

140

150

160

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00

Throughput (Kbps)

Pat

h Lo

ss (d

B)

-26.90%

-21.90%

-16.90%

-11.90%

-6.90%

-1.90%

3.10%

8.10%

13.10%

18.10%20W_1_Carrier_No_TxDiv Downlink N Users Speech


Gain



7. Strategy of non-homogeneous MHA use

7.1 Introduction

As seen MHAs will provide an improvement on the UL coverage on all sites.Nevertheless some sites get a more significant benefit than others.Possible reasons are:

• Feeder losses are low (1 dB), then the improvement in terms of link budget is low (1.4 dB)• Coverage without MHA is strong and the extension area has a very low traffic. This can be

the case when the inter-site distances are short.

These considerations could lead to the choice of designing MHAs only for specific sites and build a non-homogeneous network, some sites being with MHA and some others without MHA.However a non-homogeneous design has a negative impact on the MHA performance for sites withMHAs, and the goal of the following study is to analyse this effect.

7.2 Theoretical analysisA basic understanding of the non-homogeneous effect can be described as follows:We will assume:

è MHA improvement with Noise Factor calculation is 3 dB.è Cell_A: single cell with a MHAè Cells_N: neighbouring cells, all without MHAs

The effects of using a MHA on cell_A are:-> Higher Sensitivity for cell_A (- 3dB)

-> Lower MS Power for all MS under cell_A coverage (-3 dB)-> Higher I_intercell / I_intracell ratio

-> Higher UL load for cell_A -> Lower sensitivityfor cell_A

The Inter/Intra interference ratio is higher since the UE on the neighbouring cells do not reduce thepower by 3 dB since these cells have no MHA.

However this logic goes the other way around:On surrounding cells_N

-> Lower MS Power on cell_A (-3 dB)-> Lower I_intercell / I_intracell ratio for all cells_N

-> Lower UL load for all cells_N -> Higher Sensitivityè for all cells_N

-> Lower MS Power for all MS under cells_N-> Lower I_intercell / I_intracell ratio for cell_A

-> Higher UL load for cell_A -> Higher sensitivity

for cell_A …

There is a loop model, the question being the final mha improvement when the balance isreached.



In order to measure the effect on the final Noise Figure, some simulations have been run with Parcell3G.

7.3 Parcell 3G simulations3 different scenarios have been studied with Parcell 3G:

• Scenario 1: Dense Urban, high load (80% Uplink), 3 cells only with MHAs (1 site)• Scenario 2 Dense Urban, average load (40% Uplink), 3 cells only with MHAs (1 site)• Scenario 3: Sub-Urban, low load (10% Uplink), 1 cell only with MHA

On all sites, 3 dB feeder losses had been set, except for cells with MHA, where feeder losses were set to0 dB in order to simulate a 3 dB Noise Figure improvement brought by the MHA.

Two simulations have been run for each scenario:• 1rst simulation: all cells without MHA• 2nd simulation: additional MHA only on the selected site or cell

Doing this, it is possible to compare the total noise received by each cell in each simulation.

The following charts show the effect in terms of noise (intra, inter and total):

Dense Urban, high UL load (80%).

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

3 cells with MHA + Neighbouring cells

I_w

ith_M

HA

- I_

with

out_

MH

A (d

B)

I_totalI_intraI_inter

Neighbouring cells



Theoretically, if no “hot-spot” effect had been encountered, we would have expected:• For the cell with MHA: I_total_with_MHA - I_total_without_MHA = -3 dB• For the neighbouring cells without MHA: I_total_with_MHA = I_total_without_MHA

Dense Urban, Average UL load (40%)

-2.5

-2

-1.5

-1

-0.5

01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

3 cells with MHA + Neighbouring cells

I_w

ith_M

HA

- I_

with

out_

MH

A (d

B)

I_totalI_intraI_inter

Neighbouring cells

Sub-Urban, low load (10%).

-3

-2.5

-2

-1.5

-1

-0.5

01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1 cell with MHA + Neighbouring cells without MHA

I_w

ith_M

HA

- I_

with

ou

t_M

HA

(dB

)

I_total

I_intraI_inter

Neighbouring cells



However it was not the case:• For the cells with MHA:

o I_total_with_MHA - I_total_without_MHA > -3 dBo The effect gets stronger with the load of the network:

§ High load: MHA improvement between 0.8 to 1.6 db (instead of 3 dB)§ Average load: MHA improvement down to 2 dB§ Low load: MHA improvement around 2.85 dB

• For the cells without MHA:o I_total_with_MHA - I_total_without_MHA > 0 dB for all cells.The integration of the MHA on a surrounding cell has a positive impact on thesensitivity of the cells without MHA, due to the fact that their intercell interferencedecreases and hence their cell load is reduced.

o The effect gets weaker with the load of the network: the improvement at high load issmaller than at low load.§ High load: improvement between 0 and 0.4 dB§ Average load: improvement between 0 and 0.6 dB§ Low load: improvement between 0 and 1 dB

7.4 Conclusion on non-homogeneous useIf MHA are designed on specific sites only, a lower gain than the one computed with Friis’ formula shouldbe expected. Resulting gain can only be estimated through 3G simulations with a planning tool.

8. Conclusion

• The main interest of designing MHAs on the network is to improve the coverage and possiblyreduce the number of sites. Typically with 3 dB of feeder loss, we can expect a 3 dBimprovement.

• MHA’s can induce a slight loss of DL capacity as well as an important gain in UL capacity.

• MHAs do not require higher protection against external noise such as spurious emissions,inter-modulation, adjacent interference or desensitisation due to repeaters. Nevertheless itsimprovement would be lower if a disturbance was encountered.

• MHAs can even give better protection against blocking through its severe filtering capabilities.

• Optimum improvement is experienced when MHAs are designed homogeneously on all sites.

9. References

[1] “UMTS Downlink Dimensioning”, version 1.0, July 2001, ref LF00432O by P.Manzano[2] “UMTS MHA Orange Corporate Specification”, September 2001

Documents

Use of MHA on UMTS