3G in the Enterprise

7/29/2019 3G in the Enterprise

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3G in theEnterprise

The case for 3G picocells

Dr. Andy Tiller, VP Marketing, ip.access, December 2008


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1 SUMMARY

As enterprises turn to 3G for mobile voice and data services, operators will face a significantchallenge: getting enough coverage and capacity into office buildings.

In the 2G world, picocells have proven themselves to be a cost-effective solution and are being

widely deployed. But as the 3G enterprise challenge hits the radar screens of mobile operators,there is an apparent choice between using 3G picocells or alternatively adapting consumer-stylefemtocells to serve the enterprise.

This paper analyses the issues surrounding enterprise 3G including user experience, cost andoperational management and concludes that femtocells will serve the SOHO

1market well, but

that next-generation 3G picocells (sometimes called super-femtocells) are the clear choice forlarger business premises.

2 THE ENTERPRISE 3G CHALLENGE

Desktop PCs and laptop computers will undoubtedly remain the primary means of accessing dataservices in the office, but business users increasingly rely on their mobile handset during meetingsand other occasions when the computer is not conveniently accessible. Knowledge workers on themove are becoming familiar with 3G performance when using enterprise applications, downloadingemail attachments and accessing the Internet from their smartphones and HSPA-enabled laptops.As these workers get accustomed to 3G performance on their travels, they wil l expect and demandthe same performance inside their offices.

Unfortunately, thats a challenge for todays 3G networks. The walls and windows of officebuildings absorb most of the radio energy transmitted by the outdoor network. The energy thatdoes make it through to the user is typically as little as a fortieth of the outside power (and oftenmuch less). This results in customer dissatisfaction with patchy voice coverage, and especiallywith poor data performance (because high-speed data requires a very good quality signal). Mobileoperators are vulnerable to losing business customers in places where their in-building coverage ispoor for example, T-Mobile has found this is the top reason its customers switch to rivalnetworks

2.

To make matters worse, since all users in a 3G cell share the available base station transmitpower, a few indoor users consuming data services can significantly reduce the capacity of theentire cell and compromise service quality for outdoor users as well. Clearly, operators need acost-effective way to deliver 3G coverage and capacity directly to enterprise users in their offices.

1Small Office / Home Office

2Business Week, 27 June 2007


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3 THE MARKET SWEET SPOT

The enterprise 3G market is bounded at the low end by SOHO offices roughly the size of homes in fact many of them are homes where 3G coverage can be provided by a single femtocelldesigned for residential use. A 4-channel femtocell could potentially serve an office of up to 10mobile phone users

3. On the other hand, it might be sufficient for only four (or even fewer)

handsets if mobile phone usage is heavy or if the quality of service needs to be better than themacro network outdoors (e.g. to match the quality of a rival fixed line network)

4.

At the high end of the market, the largest offices are covered by traditional in-building solutionssuch as Distributed Antenna Systems and micro basestations, often complemented by picocellswhere a rapid solution is needed with minimal disruption. The pay-back from keeping theseimportant enterprise customers happy justifies the operators investment in in-building wirelesssolutions.

Between the two extremes is a large market consisting of offices housing up to 100 staff, whichaccounts for more than half of all office premises (see Figure 1). Many of these smaller officesbelong to large enterprises; mobile operators are highly motivated to provide a good quality serviceto these customers. The remainder belong to Small to Medium Enterprises (SME

5).

Mobile and fixed operators are beginning to compete more aggressively for SME customers. As

the trend to all-mobile office communications continues, mobile broadband has provided an entrypoint for mobile operators to target the SME market. But the fixed line carriers are fighting backwith their own enterprise FMC offerings based on dual mode WiFi handsets. In this environment,its especially important that mobile operators can offer a cost-effective way to guarantee 3G voicequality and data performance in smaller office buildings.

Figure 1: size distribution of office premises in the United States

34 channels deliver 0.87 Erlangs at 1% blocking, which is sufficient for 10 users at 75 mErlangs each in the busy hour.

44 channels deliver 0.70 Erlangs at 0.5% blocking, sufficient for only 4 users at 150 mErlangs each in the busy hour.

5Also called SMB Small to Medium Businesses.


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More than a third of SMEs have mobile phone coverage issues in their places of work6, but

historically, mobile operators have had no cost-effective in-building wireless solution for themajority of this market. A consumer femtocell lacks the capacity and range required to providecoverage in most of these offices, and the cost of DAS is prohibitive. Sometimes end customerstry to solve in-building coverage problems for themselves by installing repeaters, causing a varietyof problems for the outdoor network.

4 ENTERPRISE 3G OPTIONS

Operators getting to grips with the 3G SME opportunity are beginning to evaluate their alternatives.For all but the smallest and largest premises, the choice comes down to two approaches: eitherdeploy multiple consumer-style 3G femtocells in each office, or deploy 3G picocells.

In principle, both options deliver compelling benefits:

o They bring a complete base station into the office, delivering targeted coverage and

capacity exactly where its needed.o They remove in-building users from the macro network, freeing up capacity and improving

network performance for outdoor users.

o They use IP backhaul over a fixed line broadband connection to significantly cut the cost ofinstallation and operation.

o They can be integrated to a local PBX, turning the mobile phone into a fixed line extensionwhen in the office.

o In future they will be able to route data locally in the office to provide fast, secure access todocuments on the LAN from any meeting room on any device

7.

However, both solutions have traditionally had drawbacks. Early 3G picocells were large andexpensive, requiring dedicated E1/T1 lines for backhaul and on-site installation by the operator.

Meanwhile, femtocells were designed for residential use one per household with insufficientcapacity and range for offices. But recent developments are changing this picture, making bothoptions potentially a lot more attractive for the SME market.

4.1 Next generation 3G picocells

A new generation of 3G picocells builds on todays 3G femtocell technology. These picocells havehigher capacity and range than femtocells, but they are based on low-cost femtocell technologyplatforms, and take advantage of auto-configuration techniques developed for femtocells to enableself-installation by the end customer. They also share a common network architecture withfemtocells, and will use the new Iu-h standard

8for core network integration.

6Quocirca survey: UK, France, Germany, Sweden (June 2008)

7This relies on Local IP Access Services (previously referred to as local breakout), which is currently an active topic of

discussion in the standards bodies.8

Iu-h is the 3GPP standard for Home Node B (femtocell) integration with the core network.


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3G picocell (super-femtocell) Femtocell

Maximum transmit power ~ 250 mW (24 dBm) ~ 20 mW (13 dBm)

Range ~ 200 m ~ 30 m

Capacity 8-16 channels 4 channels

Access control Typically open access Typically closed / semi-open

Handover Yes Yes

Self-installation Yes Yes

PBX integration Yes Yes

Table 1: comparison of 3G picocells and femtocells

These next-generation picocells are sometimes referred to as super-femtocells (i.e. femtocellswith picocell capacities). Equally they can be thought of as picocells with femtocell attributes (seeTable 1).

4.2 The intelligent femtocell grid

Some femtocell vendors are promoting the concept of an intelligent femtocell grid, whichautomatically configures itself to optimise performance in premises which require more capacity orcoverage than can be provided by a single femtocell access point.

These femtocells hand over calls between them as people move around the building, and supportload balancing so that users are passed from one femtocell to another when one is at full capacity.

5 COMPARING 3G PICOCELLS AND THE FEMTOCELL GRID

Several factors must be considered when comparing 3G picocells with the femtocell grid approach.These include:

o Cost scaling how many femtocells does it take to equal the coverage and capacity of asingle picocell?

o The canteen effect how do femtocells and picocells handle the uneven distribution ofusers within the office at different times of day (for example in the canteen at lunchtime)?

o Interference how are capacity, coverage and user experience affected by interferencebetween access points in the office?

o Auto-configuration and management how do the two solutions support self-installation

by the end user, and management features for the operator?

o Access control how important is it for the end customer to have control over who canaccess the mobile network in the office?


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5.1 Cost scaling

It takes several femtocells to match the voice capacity of a single picocell. A 4-channel femtocellcan serve eleven users at 75 mErlangs with 1% blocking, which means that you would need a gridof four femtocells to serve an office of roughly 40 mobile phone users (ignoring other factorsdiscussed below).

A single 8-channel picocell has about the same capacity and could serve the same office. So atthe simplest level you would need four times as many femtocells as picocells in this case. A single16-channel picocell could serve as many users as 10 femtocells (see Table 2).

Number of APs required to serveN users at 75 mErlangsAccess Point Capacity at 1% blocking

N=40 N=115

4-channel femtocell 0.87 Erlangs 4 10

8-channel picocell 3.13 Erlangs 1 3

16-channel picocell 8.88 Erlangs 1

Table 2: voice capacity of femtocells and picocells

The femtocell grid potentially offers greater data capacity (typically 7.2 Mbps per access point withtodays femtocells versus 7.2 Mbps for the whole office with the picocell). However, interferencebetween femtocells diminishes this advantage (see section 5.3 below).

One final cost consideration is that the core network infrastructure for femtocells is designed formass market scale. An operator without an existing consumer femtocell offering to build on mightfind the start-up costs for picocells are lower, especially for small scale deployments.

5.2 The canteen effect

People move around. For most offices, that means an uneven distribution of demand in different

parts of the building at different times of day (for example, mobile phone use will potentially beheavy in the canteen at lunchtime).

This uneven distribution makes it difficult to spread capacity evenly between femtocells. Whenusers congregate in one area, demand for capacity can exceed supply.

Figure 2: more femtocells are required to provide sufficient capacity in usage hotspots


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A picocell serves mobile phone users wherever they are in the office, so users are covered underall circumstances. Femtocells only cover a small, local area, so you would need to put more ofthem into hotspot areas to provide enough capacity, adding extra cost (and creating moreinterference).

5.3 Interference

Femtocells interfere with each other in places where their coverage areas overlap (see Figure 3).In these interference zones, the user experience for voice calls can be very poor without diversitycombining, and HSPA data services may not work at all.

Figure 3: coverage simulation for a femtocell grid deployment: bricked areas show poor

radio performance

A potential solution is to use soft handover between the femtocells, using additional radio pathsfrom overlapping access points to combine multiple signals and protect against interference. Softhandover is a standard WCDMA feature (although it is not standardised for femtocells).

But using soft handover means that a phone in an overlap region will occupy channels on twoneighbouring femtocells at the same time (see Figure 4), thereby reducing the capacity of thefemtocell grid. More femtocells will need to be added to restore the required capacity. However,adding more femtocells makes the problem worse by creating more interference zones (morefemtocells in the same space means greater overlap of coverage areas). This in turn will increasethe number of phones in soft handover mode, which in turn reduces the capacity of the femtocellgrid even further, requiring even more femtocells to restore the required capacity.


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Figure 4: soft handover (SHO) between femtocells

An alternative solution to the interference problem is to deploy a single picocell with appropriatecapacity for the office instead of a femtocell grid. Potential interference between picocells is muchmore manageable as a single picocell will usually cover an entire floor of a building, allowing thefloors and ceilings to provide effective isolation between the cells.

5.4 Auto-configuration and management

Self-installation by the end customer is key to bringing installation costs down to a point where thebusiness case works for smaller SMEs. Low power consumer femtocells score well here, beingdesigned for plugnplay installation by the end user and automatic registration on the network

without any operator involvement.

Picocells can use the same automated provisioning techniques as femtocells to enable self-installation by the end user. However, picocells are more powerful devices, so operators may wantto fine-tune the network following a picocell installation. This network tuning can be done remotely,and may be semi-automated, but in principle there is still a higher operational cost than withfemtocells.

On the other hand, some operators prefer to take a more hands-on approach with enterprisecustomers. Consumer femtocells typically dont provide the kind of sophisticated fault monitoring,alarms and performance management that enterprise use calls for the management demandsare quite different. Operators wouldnt want an alarm to be raised every time a residentialcustomer unplugs the femtocell from the mains to vacuum the carpet. But if the picocell on the wallin a local bank branch goes offline the operator will want to be notified immediately, as this mayaffect a Service Level Agreement with an important business client.

Its clearly important that the management systems can distinguish between business andresidential customers so that alarms and performance triggers can be configured appropriately.Many consumer femtocell vendors specialise in the CPE devices (the access point itself), leavingthe management problem to someone else. An enterprise 3G solution should incorporate anintegrated management system appropriate to the business market.


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5.5 Access control

A standard feature of consumer femtocells is support for access control, giving the end customercontrol over which phones can use the network.

Most picocells will not be deployed at high power in closed access mode because this could

potentially create coverage holes on the macro network for non-authorized users in the picocellcoverage area. A low-power femtocell with a small coverage area has a potential advantage hereif access control is important.

On the other hand, its arguable whether the (sometimes non-existent) IT department in a smallbusiness would want the hassle of administering the access control list for all members of staff,contractors and visitors. It may be simpler to deploy picocells in open access mode with sufficientcapacity to give passers by basic voice and Internet services. This is the normal mode of operationfor 2G picocells today.

5.6 Practical considerations

Sprinkling consumer femtocells around a busy office may cause some practical difficulties. Accesspoints may routinely get unplugged, moved, abused and splashed with coffee, leading to outages.Each time a femtocell is unplugged the femtocell grid will need to re-optimise itself to account forthe change in the radio environment, with potential consequences for the user experience.

In practice, wall mounted access points served with connectivity and power by a single Ethernetcable would be a more stable solution. Consumer femtocells could readily be modified to supportpower over Ethernet and wall mounting, but in these circumstances picocell deployment is morepractical for the end customer, requiring far fewer installations than the femtocell grid.

6 CONCLUSIONS

A careful analysis of the options for deploying 3G in the enterprise has led us to the followingconclusions:

1. Consumer femtocells are a good solution for the SOHO market, where offices are similarsize to homes.

2. The right approach to 3G coverage in SME offices (and branch offices of largerenterprises) is to use a next-generation picocell (or super-femtocell) with range andcapacity appropriate to the size of premises. Key strengths of the picocell approach are:

o A single wall-mounted picocell can provide coverage and capacity for the entire office

o Capacity is unaffected by users moving around or clustering in one area

o Interference issues are significantly reduced

o Advanced management features give the operator control over service quality for theirimportant business customers.


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About ip.access

Based in Cambridge, UK, ip.access ltd. is a leading manufacturer of cost-effective picocell andfemtocell infrastructure solutions for GSM, GPRS, EDGE and 3G. These solutions bring IP andcellular technologies together drive down costs and increase coverage and capacity of mobilenetworks.

ip.access is the company behind the multi-award winning Oyster 3G femtocell, whichdramatically improves the 3G experience at home.

The ip.access nanoGSM is the worlds most deployed picocell solution, carrying over a billionminutes of voice traffic every year for operators all over the world, including T-Mobile, TeliaSonera,and Telefnica O2. It provides GSM, GPRS and EDGE coverage and capacity for offices, shopsand using satellite backhaul passenger aircraft, ships and in remote rural areas.

With deployments in more than 35 live networks around the world and growing, ip.access is thepartner of choice for operators competing in the new converged marketplace.

ip.access is an active member of the Femto Forum, ETSI and the Network Vendors InteroperabilityTesting Forum.

[email protected]

Copyright ip.access 2008. Oyster 3G and nanoGSM are trademarks of ip.access ltd. All other trademarks areacknowledged. This document contains advance information, subject to change without notice. No responsibility is assumedby ip.access for the use of this information, nor for infringements of patents or other rights of third parties. This document isthe property of ip.access and implies no license under patents, copyrights or trade secrets. No part of this publication maybe copied, reproduced, stored in a retrieval system, or transmitted, in any form of any means, electronic, photographic, orotherwise, or used as the basis for manufacture or sale of any items without the prior written consent of ip.access.

ip.access ltd

Building 2020Cambourne Business Park Cambourne Cambridge CB23 6DW UK

T +44(0)1954 713700 F +44(0)1954 713799 [email protected]

www.ipaccess.com

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