Comba Telecom White Paper: Meeting the Data Demand Tidal Wave

1 ©2015 Comba Telecom. All Rights Reserved

MEETING THE

DATA DEMAND TIDAL WAVE:

UPGRADE OF INDOOR DAS FOR LTE

May 2015

A Comba Telecom White Paper


TABLE OF CONTENTS EXECUTIVE SUMMARY .................................................................................................... 3

EVOLVING MARKET DEMAND TOWARDS LTE ..................................................................... 4

CONSIDERATIONS FOR INDOOR LTE DEPLOYMENT ............................................................... 4

CASE STUDY ................................................................................................................. 5

Phase I .......................................................................................................................................... 6

Phase II ......................................................................................................................................... 7

Phase III ........................................................................................................................................ 8

Summary of Results ..................................................................................................................... 9

CONCLUSION .............................................................................................................. 10

ABOUT COMBA TELECOM ............................................................................................. 11


EXECUTIVE SUMMARY

Consumers have become heavily dependent on their mobile devices and

expect uninterrupted ubiquitous coverage and fast data performance.

Network operators are encountering an overwhelming amount of data traffic

that is forcing them to embrace efficient data-centric technologies like LTE.

A large volume of mobile data is being consumed indoors; such as residential

buildings, offices and commercial spaces. In-building systems (IBS) were

typically deployed in sites with high voice traffic or serving important

customers/corporate accounts, due to the additional CAPEX investments.

Indoor coverage in most other buildings is incidental, served by macro outdoor

base stations nearby. Coverage tended to be limited, due to the building

penetration losses.

With rapid urbanization and building densification, outdoor cell sites are

increasingly inadequate to meet indoor consumption demands and

expectations. Existing distributed antenna system (DAS) built for voice services

on GSM and even 3G is not capable of delivering the customer’s expected data

performance with a direct upgrade of base station equipment.

To retain and attract customers, operators need to channel investments into

indoor systems beyond outdoor rollout for 3G/4G. However, with limited

CAPEX, the low hanging fruit is to upgrade important buildings with existing

DAS systems to ensure they meet the required data quality of service (QoS).

In the case study, we see that re-using DAS infrastructure designed for voice

cannot meet the data requirements for LTE or even HSPA. The antenna must

be densified by approximately 1.5 times to achieve the desired LTE high data

rates.

This paper discusses the growing market demand for data centric technologies

and concerns regarding its efficient indoor deployment. It also presents a case

study to quantify the CAPEX investment versus performance improvement for

evolving from voice centric IBS to support LTE/HSPA.


EVOLVING MARKET DEMAND TOWARDS LTE

Global Mobile-Suppliers Association (GSA) published a map depicting

worldwide LTE deployments by 2014 as shown in Figure 1. According to this

report, 533 operators globally have committed to LTE networks out of which

331 have already deployed commercial LTE networks in 112 countries.

Furthermore, LTE subscriptions worldwide have reached an overwhelming

280.4 million by Q2 2014.

Figure 1: Global LTE Deployments by 2014 (Global Mobile-Suppliers

Association)

Ericson’s mobility report for 2014 had estimated total mobile subscriptions to

be in the order of 6.8 billion by Q1 of 2014. These are expected to further grow

to 9.2 billion by the end of 2019. LTE subscriptions alone are expected to grow

to 2.6 billion by 2019, thereby representing almost 30% of total mobile

subscriptions.

Based on a Cisco report, at least 80% of all mobile traffic is now generated

indoors. This is mainly due to the shift in mobile usage from voice to data-

centric services such as social networking, online gaming and media streaming

applications. Therefore, it is vital that network operators focus on indoor LTE

deployment to meet rising consumer data requirements.

CONSIDERATIONS FOR INDOOR LTE DEPLOYMENT 1) Deployment techniques

Multiple deployment options are available to operators for providing indoor

coverage:

Outdoor Macro Network: Traditionally outdoor networks have been used

to provide coverage to indoor customers. Such networks need to consider

distance from cell tower, obstruction from environment clutter, wall

penetration losses and service requirements. Efficient outdoor


deployment methods include optimizing antenna tilt, minimizing

interference to increase capacity and re-farming lower frequency

spectrums to enhance coverage.

Small Cells: Small cells with its small footprint and ease of installation is

suitable for small to medium enterprises and residential deployment.

Typically it is targeted for small coverage area with medium traffic due to

its low output power and dedicated capacity,

Wi-Fi Offload: Wi-Fi is used to offload data traffic from mobile networks

in hot spots and increasingly as an additional layer to both indoor and

outdoor networks.

In-Building DAS: A distributed antenna system is a reliable way of covering

medium/large buildings to ensure good indoor performance. Operators

can appropriately deploy an active or passive DAS network. Its ability to

host multiple operators, services and technologies compensates for the

relatively high deployment costs.

2) Spectrum considerations

Network operators also need to come up with a spectrum strategy to make

efficient use of an expensive resource. Based on spectrum availability, capacity

requirements and budget constraints, operators can re-farm their existing

spectrum or purchase additional spectrum for 4G rollout.

Lower spectrum bands provide better signal strength but higher spectrum

bands can accommodate enormous data volumes due to larger available

bandwidth. Operators also need to decide on whether to deploy a dedicated

frequency band and bandwidth for indoor deployment e.g. 1800MHz for

outdoor and 2600MHz for indoor or use a common underlay coverage layer

for both indoor/outdoor and a separate band for capacity overlay layer.

CASE STUDY This case study looks at the capital investment versus performance for a typical

building passive DAS upgrade from voice centric 2G to support data centric LTE

network.

The chosen site is a mid- sized, high traffic commercial building – a 9 storey

shopping center of 700,000 square feet, with 9 floors of retail space.

The in-building DAS is upgraded in 3 phases from GSM DAS to provide LTE 2x2

MIMO.

1) Phase 1: The DAS is upgraded to provide 3G by reusing 2G DAS design.

However, the 3G performance is poor.

2) Phase 2: The DAS is retro-fitted to meet HSPA/LTE network KPI for data

services.

3) Phase 3: The DAS is upgraded to support LTE 2x2 MIMO.

Tables 1-3 are the operator defined 2G, 3G and LTE system information and

key performance targets for indoor coverage.


Table 1: KPI for 2G

Technical Specification Criteria

Frequency 900MHz, 1800MHz

Signal Transmit Power at BTS output 39 dBm

RxLev >= -80 dBm @ 99% coverage area

Table 2: KPI for 3G


Frequency band 2100MHz

CPICH Transmit Power at Node B output 30 dBm

CPICH RSCP >= -90 dBm @ 99% coverage area

CPICH Ec/No >= -10 dB @ 99% coverage area

Average DL FTP Throughput (HSDPA) Average up to 4 Mbps walktest

Table 3: KPI for LTE


Frequency Band/Bandwidth 1800MHz (10MHz)

LTE Pilot Transmit Power at eNodeB output

15 dBm

LTE RSRP >= -92 dBm @ 99% coverage area

LTE RSRQ >= -12 dB @99% coverage area

Average Downlink Throughput > 24 Mbps (2x2 MIMO)

PHASE I

In this phase, 2G DAS is reused for 3G upgrade. The 2G IBS network is

supplemented by a 3G base station while re-using the existing DAS as shown

in Figure 2. Antenna count and cable length remain unchanged.

Figure 2: 3G DAS Reusing Existing 2G Infrastructure

The 3G RSCP and Ec/No walk test plots for a typical floor are shown in Figures

3-4 respectively.


Figure 3: RSCP Walk test Plot for 3G IBS

Figure 4: Ec/No Walk test Plot for 3G IBS

The RSCP plot shows the 3G signal strength greater than -90dBm for only

72.7%. Similarly, Ec/No plot indicates that 3G signal quality was better than -

10dB for 38.6% of the same floor.

From these plots, we observe that a direct re-use of 2G DAS is incapable of

meeting the required 3G KPI targets. The DAS design needs to be enhanced.

PHASE II

In phase II, the DAS design is improved by re-working the required cell radius

to meet coverage KPI and data throughput requirements for both HSPA and

LTE. Data centric networks require high signal to noise ratio (SINR) to achieve

high throughput rates by operating in higher order modulation schemes and

MIMO signal strength requirements. This translates into a smaller antenna

radius but a higher density of antennas. Hence, the number of antennas and

feeder cable required per floor rises.

Figures 5-6 captures the post upgrade RSCP and Ec/No walk test results for the

same floor. Additional antennas are marked in blue versus the existing

antennas are in green.

Figure 5: RSCP Walk test Plot for 3G Network Enhancement


Figure 6: Ec/No Walk test Plot for 3G Network Enhancement

The plots indicates RSCP greater than -90dBm and Ec/No better than -10dB for

more than 99% of the coverage area. Also, the average HSDPA downlink

throughput measured on site was found to be 9.2Mbps.

From these results we can see that the 3G KPI is fulfilled after the re-design

and antenna densification.

PHASE III

In the last phase, DAS network is doubled to support LTE 2x2 MIMO as shown

in Figure 7. The LTE eNodeB is added to the network with the main output path

feeding the existing DAS. The 2nd path is fed into a duplicate DAS where

separate omni antennas are used for MIMO.

Figure 7: DAS Infrastructure for LTE 2x2 MIMO

Figures 8-10 show the LTE average serving cell RSRP, RSRQ and downlink

throughput walk test results for LTE 1800 MHz system respectively.

Figure 8: RSRP Walk test Plot for LTE1800 2x2 MIMO System


Figure 9: RSRQ Walk test Plot for LTE1800 2x2 MIMO System

Figure 10: Cell Downlink Throughput Walk test Plot for LTE1800 2x2 MIMO System

The RSRP plot shows signal strength more than -92dBm and RSRQ better than

-12dB for more than 99% of coverage area. The cell downlink throughput

achieved an average of 33.9Mbps for 10MHz of bandwidth.

The LTE KPIs are satisfied after upgrading the DAS to be MIMO 2x2 ready.

SUMMARY OF RESULTS

Table 4 summarizes the improvement in measured KPI per phase of the DAS

upgrade.

Table 4: IBS Performance at each phase of DAS upgrade

Phase I Phase II Phase III

3G KPI

RSCP Target RSCP >= -90 dBm @ 99% coverage area

Achieved @ 72.7% >@ 99% >@ 99%

EcNo Target Ec/No >= -10 dB @ 99% coverage area

Achieved @ 38.6% >@ 99% >@ 99%

Throughput Target Avg. DL FTP throughput (HSPA) >= 4 Mbps

Achieved 9.2 Mbps* 9.2 Mbps*

LTE KPI

RSRP Target

RSRP >= -92 dBm @ 99%

Achieved >@99%

RSRQ Target RSRQ >= -12 dB @ 99%

Achieved > @99%

Throughput Target Avg. DL FTP Throughput

>= 24 Mbps

Achieved 33.9 Mbps*

* Achieved throughput rate varies with network traffic


Table 5 shows the passive equipment count and increase factor from the

original 2G DAS design.

Table 5: Passive Component Quantity

Component Phase I Phase II Phase III

Antenna Count 137 200 400

Antenna Count Increase Factor 1.46 2.92

Cable Length (in m) 3878 6028 11515

Cable Length Increase Factor 1.55 2.97

Average passive CAPEX Increase Factor 1.5 3

Overall, the average rise in CAPEX between Phase I and Phase II was found to

be about 1.5x. It further increased by 2x between Phase II and Phase III for LTE

MIMO support. Therefore, an approximate 3x CAPEX increase was involved

with upgrading the existing IBS site to LTE 2x2 MIMO.

CONCLUSION With large amounts of mobile data being consumed indoors, network

operators need to focus more at enhancing indoor coverage to ensure

customer satisfaction and reduce churn.

LTE IBS solutions provide an efficient means to meet these high capacity

demands. Operators need to consider the different infrastructure options,

service requirements and spectrum considerations in order to deploy effective

LTE IBS networks. These decisions severely impact investment budgets and the

overall system design.

Key findings of this paper are:

Operators should not purely re-use old voice centric IBS DAS as the

design is not capable of meeting the data performance of HSPA or

LTE networks.

An average of 1.5x antenna densification is needed to achieve the

base throughput requirements.

To reap the maximum benefits of MIMO, an additional 2x of passive

equipment is required.

Since operators are already investing CAPEX into base station equipment, the

DAS system must also be correspondingly re-designed and retrofitted to

deliver an effective HSPA/LTE network with throughput performances that

meet end customer QoS expectations.


ABOUT COMBA TELECOM Comba Telecom is a leading supplier of infrastructure and wireless

enhancement solutions to mobile operators and enterprises to enhance and

extend their wireless communications networks. With over 50,000 system

deployments around the world including turnkey in-building systems,

urban/rural wireless systems, and transport wireless networks, Comba

Telecom’s end-to-end network solutions include consultation, network design,

optimization and commissioning.

Comba Telecom’s product portfolio includes DAS, small cells, tower mounted

systems, antennas, subsystems, passive accessories, Wi-Fi systems and digital

microwave links.

Listed on the Hong Kong Stock Exchange, Comba Telecom is headquartered in

Hong Kong and has operations throughout the Americas, Europe, Middle East,

Africa and Asia Pacific. To learn more, visit www.comba-telecom.com and

follow Comba Telecom on LinkedIn for regular updates.

www.comba-telecom.com [email protected]

© 2015 Comba Telecom. All rights reserved. Comba Telecom reserves the right to change, modify, transfer, or otherwise revise this

publication and the product specifications without notice. While Comba Telecom uses commercially reasonable efforts to ensure the

accuracy of the specifications contained in this document, Comba Telecom and its affiliated companies will assume no responsibility for any

errors or omissions. Nothing in this publication forms any part of any contract.

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Comba Telecom White Paper: Meeting the Data Demand Tidal Wave