August 2012 1
Contents Executive summary... 3 1 Introduction - different ways to deploy small cells... 4 1.1 Capacity or Coverage - what s the difference?... 5 2 Consumer/Enterprise self-deployed (femtocells)... 6 3 Operator deployed small cells... 7 3.1 Targeted capacity hot-spot... 7 3.2 Non-targeted ( peppered ) QoE enhancement... 8 3.3 Outdoor and indoor coverage not-spots... 10 4 Summary... 11 5 Glossary... 12 6 About Cambridge Broadband Networks Limited... 12 Author Julius Robson is a Wireless Technology Specialist at Cambridge Broadband Networks Limited. Julius leads the NGMN Small Cell Backhaul Group and is Vice Chair of the Small Cell Forum s Backhaul special interest group. Front cover image courtesy of Keima Wireless Ltd August 2012 2
Executive summary Virtually all operators now include small cells in their strategy to provide ubiquitous mobile broadband, and this paper considers the different approaches that might be adopted to deploy them, and the implications for backhaul. The decision tree below summarises factors which differentiate between deployment styles: whether they are consumer or operator deployed and whether they are predominantly needed to enhance the capacity of an existing service, or whether the small cell will bring new coverage to an area. The combinations of these factors lead to five deployment styles, each with differing implications for the best backhaul solution. Whilst consumer deployed femtocells are likely to be the most numerous, they will mostly use leased backhaul from a service provider. Consumers will not be too concerned on the backhaul technology choice provided the service level is acceptable. Operators will also deploy small cells and backhaul, and will use different approaches depending on the particular problem they wish to address: Persistent demand hot spots can be targeted providing a site within range can be acquired and suitable backhaul connectivity provided. This approach is demanding from both backhaul coverage and capacity perspectives. Non-line of sight solutions may be needed in the places where high capacity fibre and line of sight (LOS) wireless cannot reach. Consumer Quality of Experience can also be enhanced by peppering small cells in general areas of high demand, making the most of available sites that can be easily backhauled with high capacity LoS wireless or fibre. Operators will also use small cells to address not-spots in both outdoor and indoor locations. Where coverage is the primary motivation, lower capacity backhaul solutions can be considered. Uncovered outdoor areas are likely to be in remote locations, requiring long rage solutions such as satellite or point-to-point microwave. Indoor small cells might connect into the building s LAN or use a Distributed Antenna System. In summary, our examination of different small cell deployment styles helps to understand when to select a particular tool in the backhaul solution toolbox. August 2012 3
1 Introduction - different ways to deploy small cells The small cell banner incorporates micro, pico, femto and metrocells which are collectively expected to constitute almost 90% of all basestations by 2016 1. They have been heralded as the answer to a range of issues faced by operators in their bid to keep up with the ever-growing appetite for broadband mobile access. However, significant challenges remain in deploying small cells, connecting them up and switching them on. A recent survey found 56% of operators citing backhaul as one of the greatest challenges, second only to fundamental issues of site acquisition, power etc 2. In our previous white paper, Easy Small Cell Backhaul 3 we took a detailed look at the requirements for backhaul and considered how the different types of solutions matched up against these. Six months on and with many small cell trials underway, we now examine the different approaches that operators are considering in rolling out small cells. We have grouped these deployment styles into broad use case categories defining the primary motivation and style of deployment as follows: Consumer/Enterprise self-deployed (femtocells) Operator deployed small cells: o Targeted capacity hot-spot o Non targeted ( peppered ) Quality of Experience (QoE) enhancement o Outdoor and indoor coverage not-spots This paper considers in which situations each strategy might be used and gives example scenarios. The implications for backhaul are also considered, and the types of solutions that are most appropriate. 56% of operators cite backhaul as one of the greatest challenges, second only to fundamental issues of site acquisition 2 In this consideration of backhaul solutions, it is the operator deployed scenarios that are of most interest, as operators represent the main market for these technologies. Consumers and enterprises deploying small cells will likely leased lines from service providers (DSL, Cable, Fibre), and are less likely to be interested in deploying backhaul solutions themselves. 1 Small cells to make up almost 90% of all base stations by 2016, Small Cell Forum, Feb 2012, http://goo.gl/4w9pv 2 Small Cells Market Status, Informa Telecoms and Media Small Cell Survey, June 2012, http://goo.gl/zq8f4 3 Easy small cell backhaul, Cambridge Broadband, Feb 2012, http://cbnl.com/resources/easy-small-cellbackhaul August 2012 4
1.1 Capacity or Coverage - what s the difference? The use cases differentiate between small cells providing capacity and those providing coverage. However, de facto adding a small cell to the network provides a degree of both, so what s the difference? Our definition, which was adopted by the NGMN 4, considers whether the small cell is deployed in addition to existing macro coverage, or whether it brings a new service to an area where is was previously unavailable. In the days of voice, the service is either there or not. However in the age of mobile data the service can range from GSM EDGE with a few kbps, to multi-megabit HSPA or LTE. A general definition is that coverage enhancement brings a new service (or level of service) to an area where it could not previously be experienced, even during quiet times with only one user accessing the network. Capacity enhancement can be considered as a way of increasing the number of people that can have a given level of broadband experience in an area during the busy times. Although a small cell will likely improve both coverage and capacity, the definitions consider the operators primary motivation for deployment. The following sections consider each use category in turn. 4 Small Cell Backhaul Requirements, NGMN Alliance, June 2012, http://goo.gl/ehhtx August 2012 5
2 Consumer/Enterprise self-deployed (femtocells) Description The vast majority of small cells will be self-deployed by consumers or enterprises in order to provide coverage or enhance the QoS of cellular connectivity in their home or office. Femtocells or home basestations have required the development of true plug and play technologies, as well as those for Self Organising Networks (SONs). End users deploy the small cell where they believe it is most needed and where they can provide power and network connectivity. Self-deployed residential and enterprise femtocells typically use leased internet connections for backhaul. Image courtesy of Ubiquisys A key limitation of self-deployed femtocells is that most consumers would prefer to restrict access to themselves and a limited white list of users. These closed access small cells therefore do not improve coverage for all of an operator s subscribers. As such, operators are looking to leverage the benefits of femtocell technologies for low-cost deployment, but in an open access mode available to all subscribers. Backhaul implications Femtocells typically use the consumers existing leased line internet connection for backhaul which may be via DSL, Fibre, Cable or Satellite. Femtocell owners themselves are not concerned with the type of technology used for backhaul this is the domain of their Internet Service Provider (ISP). Applicable backhaul solutions Leased DSL Fibre Cable August 2012 6
3 Operator deployed small cells 3.1 Targeted capacity hot-spot Description The small cell is deployed at the centre of an area of high-demand density. Macro coverage is already present at the location, but hot-spot demand causes congestion and poor Quality of Service (QoS) during busy times. The hotspot small cell provides both better propagation and less sharing of the mobile spectrum, improving QoS for the users it serves. Offloading this traffic also improves QoS for users who continue to be served by the macro layer. Hot-spot deployment requires identification of the high-demand locations, and for them not to move during the lifetime of the small cell. Data mining techniques based on social media (e.g. geo-tags from Flickr photos or tweets) can indicate concentration of smartphone usage and potential capacity hot-spots. Targeted hot-spot deployment further requires that a site can be acquired close enough to the optimal location for the small cell s coverage to match with the area of high demand. Because the coverage area of a small cell is, by definition, small, this may be very difficult to achieve in practice. Demand hot-spots can potentially be located from geo-tagged social media data. Source: Keima 5 Examples Dense urban hot-spot Transport hub (train/bus station, airport), metro station exit Point of interest generating significant mobile traffic (e.g. photo uploads at landmarks) Special events stadiums, festivals, pop concerts Disaster scene needing additional capacity for emergency services 5 Image courtesy of Keima Wireless Ltd: http://keima.co.uk August 2012 7
Backhaul implications The ideal backhaul solution would have very flexible coverage to be able to reach the ideal hotspot location. As identified by the NGMN, backhaul for hot-spots must also have high capacity so as not to limit in any way the amount of traffic demand that the small cell can soak up. Flexible coverage points towards the non-line of sight backhaul solutions, yet these are recognised to have low capacity due to the limited amount of <6GHz spectrum economically available. Where line of sight to a backhaul hub is available, a high-capacity microwave or mm-wave link can be deployed. Otherwise, multi-hop or non-line of sight can be considered. Since an underlay macro service is already available, the customer QoE is less sensitive to the availability of the small cell backhaul connection. Costs can be reduced for example, by not using redundancy. Applicable backhaul solutions Fibre Line of sight: point-to-multipoint (PMP) microwave, millimetre wave Non-line of sight where fibre or line of sight microwave not available 3.2 Non-targeted ( peppered ) QoE enhancement Description The peppered approach deploys many small cells in areas of high demand for general enhancement of consumer QoE over an existing underlay macro coverage. Site selection is less focussed on pinpointing the perfect locations, and instead makes use of available sites which can easily be acquired and backhauled. The intrinsic non-line of sight propagation provided by the small cells themselves mitigates the suboptimal placement of the small cell units. This blanket approach has a reduced RF planning effort compared to the targeted approach. It is also more suited to areas of high-demand significantly larger than the coverage area of a single small cell. Although in theory peppered is likely to be marginally less efficient than a targeted approach, in practice the difficulties in pinpointing long-term hotspots and acquiring optimal site locations with backhaul will erode the benefits. The overall Total Cost of Ownership (TCO) for the peppered approach may well be lower for a given level of user QoE. Examples Urban areas with a set of municipality owned sites (street furniture, public buildings etc.) Suburban capacity infill Local authority managed service deployed over set of owned locations. August 2012 8
Peppering of small cell sites in an area of general high demand, where high capacity line of sight or fibre backhaul is available Backhaul implications The peppered approach makes use of sites which can be more easily acquired and backhauled, so to some extent the backhaul topology can influence site locations. Existing fibre can be leveraged, or sites with line of sight to a nearby hub or repeater in a multi-hop topology. As with the targeted approach, the presence of the underlay macro coverage means small cell backhaul availability can be relaxed without impacting consumer QoE. Applicable backhaul solutions Line of sight point-to-multipoint (PMP) microwave Millimetre wave Fibre August 2012 9
3.3 Outdoor and indoor coverage not-spots Description Small cells can be deployed in areas with no existing macro coverage often called not-spots. These may be isolated locales where it is not cost-effective to deploy a macro-site, but a lower cost small cell would suffice. They might also be large indoor areas in public buildings such as shopping malls or airports. As regulators are mandating ever higher coverage obligations 6 7, not-spot small cells may help operators extend coverage to the last few per-cent of the population, both outdoors and indoors. Potential outdoor and indoor not-spots Examples Outdoor o Underserved villages and town locations Indoor o Rural areas with marginal outdoor coverage o Shopping malls, airports, museums o On board a ferry, train or aeroplane Privately owned homes and businesses needing coverage might be better suited to a self-deployed femtocell approach Backhaul implications Traditionally, long range microwave point-to-point links have been used to reach remote locations. However, the cost of setting up the link may prove too much compared to the revenue that can be generated from the small number of people served. The combination of a low-cost small cell with low-capacity satellite backhaul is becoming a viable option for remote locations 8. NGMN requirements show that for not-spot small cells, lower backhaul capacities are acceptable. However, since there is no existing coverage to act as a safety net, backhaul availability must be as high as a normal macrocell. Many indoor locations are likely to have existing fibre or copper connectivity providing fixed telephone or data services. In some of the more remote cases, site connectivity might be provided via rooftop microwave links. 6 Ofcom unveils plans for 4G auction of the airwaves, Ofcom, July 24 2012, http://goo.gl/83ggj 7 Mobile Broadband Coverage Balancing Costs And Obligations, Analysys Mason, 28 June 11, http://goo.gl/moyge 8 Informa Study Shows How Satellite Backhaul And Small Cells Can Help Mobile Operators Affordably Reach Untapped Markets,iDirect, 2 May 2012, http://goo.gl/iblxv August 2012 10
Applicable backhaul solutions Outdoor not-spot o Satellite o Line of sight point-to-point (PTP) microwave o DSL Indoor not-spot o Fibre o DSL o Cable where available or microwave 4 Summary We have considered a number of use cases for small cells to improve the coverage and capacity of an operator s network, and identified different styles of deployment which might be used. These are summarised in the table below. Summary of deployment styles, backhaul requirements and applicable solution Deployment Style Primary Motivation Deployed by Backhaul requirements Capacity Coverage Applicable backhaul solutions Comment on backhaul Femtocell Coverage or capacity Consumer Consumer choice whether to relax Leased DSL, fibre, cable Consumer leased internet connection Targeted hot-spot Capacity Operator High Extensive Fibre and LoS microwave where Extensive coverage and high capacity difficult to available, non-line achieve with single of sight microwave solution otherwise Peppered Capacity Operator High Flexible PMP microwave, millimetre wave Flexible coverage requirement allows for high-capacity line of sight solutions Outdoor not-spot Outdoor coverage Operator Relaxed Long range to remote locations Satellite, PTP microwave, DSL Low-cost connection to remote locations a struggle Indoor not-spot Indoor coverage Operator Relaxed To building Fibre, DSL, cable where available or microwave Backhaul can use existing site connectivity and LAN The table shows that operators are likely to use a range of deployment styles for different small cell use cases. In each case differing requirements suggest different types of backhaul solution are most applicable. In general we see that where possible, Fibre or line of sight wireless techniques should be used to provide high capacity connectivity. Non-line of sight solutions can then be used to extend coverage to specific hot-spots or not-spots that could not otherwise be reached. August 2012 11
5 Glossary Quality of Service (QoS): the data rates, latency availability offered by a connection. Quality of Experience (QoE): the perceived quality of a service or application by the user. Impacted by both the offered QoS and the type of application e.g. QoE of streaming video is not impacted by latency, but voice is. Total Cost of Ownership (TCO): Capital Expenditure plus Operational Expenditure Not-spot: Area with no coverage of a service (or given level of service) Hot-spot: An area with high-demand density. In this paper we consider the hot-spot areas have an acceptable coverage of the required service during quiet times, but that congestion during busy times degrades the service below acceptable levels. Additional capacity is required. About Cambridge Broadband Networks Limited Pioneering the development and global deployment of next generation microwave transmission equipment since 2000, Cambridge Broadband Networks VectaStar platform is deployed by more operators, in more markets, than any other point-to-multipoint (PMP) microwave solution and operates at the heart of the world s busiest mobile data network. VectaStar is proven to deliver results in the most demanding network environments whilst also being deployable in 3G, 4G, small cell and LTE backhaul networks. With a network of offices around the globe, CBNL s solutions provide operators with both capital and operational savings and manage spectrum, an increasingly scarce resource, dynamically and efficiently. For more information on Cambridge Broadband Networks small cell backhaul solutions and planning tools, please contact: Cambridge Broadband Networks Limited Selwyn House Cambridge Business Park Cowley Road Cambridge CB4 0WZ United Kingdom. T +44 1223 703000 F +44 1223 703001 E info@cbnl.com www.cbnl.com 2012 Cambridge Broadband Networks Limited. All rights reserved. August 2012 12