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Examining small cell backhaul requirements


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In this presentation we look at the design requirements needed to backhaul small cell networks (covering capacity, coverage and cost) and how different backhaul options meet these needs.

We look at:
- How small cells will be deployed and what the implications are for backhaul
- The key design considerations for small cell backhaul: Capacity, Coverage and Cost
- How different backhaul solutions compare against small cell requirements.

This presentation is taken from the webinar 'Examining small cell backhaul requirements' - you can watch a recording of the webinar now at -

You can also download our white paper 'Easy small cell backhaul' -

Published in: Technology, Business

Examining small cell backhaul requirements

  1. 1. www.cbnl.comNext generation thinkingExamining small cell backhaul requirements15 February 2012
  2. 2. Examining small cell backhaul requirementsAgenda5 mins Are small cells really the next big thing? Lance Hiley, VP Marketing, Cambridge Broadband Networks Ltd15 mins The challenges How will operators deploy small cells? Key design considerations for small cell backhaul Julius Robson, Wireless Technology Consultant and Leader, NGMN Small Cell Backhaul Requirements Group10 mins The solutions How do different solutions compare against the requirements? Lance Hiley10 mins Your questions Q&A open for 10 2
  3. 3. Who we are • Formed in 2000 • Global marketshare leader in line of sight multipoint microwave technology • Suitable for LTE network backhaul • Selling to 7 of the top 10 mobile operator 3
  4. 4. Are small cells really the next big thing?Lance HileyVP MarketingCambridge Broadband Networks 4
  5. 5. Are small cells really the next big thing? • 1% smartphone users consume 50% of mobile data (what happens when others catch on?) • More recent and realistic version of Cisco VNI still shows growth • New devices and apps will use whatever capacity is available • Industry is organising itself to speed small cells to 5
  6. 6. Small cells could be the answer • Mobile cellular networks were initially designed for voice • The popularity of mobile broadband multimedia services has redefined the RAN and backhaul“Best Signal Quality in Cellular Networks: Asymptotic requirements of mobile networks: data isProperties and Applications to Mobility Management inSmall Cell Networks”, Alcatel-Lucent, 2010 dominant • Mobile networks have to evolve to transport packet data traffic efficiently: data is different • Reducing cell size is one of the most effective ways to improve the spatial reuse of radio resources and increases network capacity • Bringing bandwidth closer users improves customer quality of experience 6
  7. 7. Small cells could be the answerSmall cells can ease congestionin busy areas by serving hotspots and indoor users, leavingmacro-layer to deal with wide-areahigh-mobility outdoor users In this webinar we consider the implications of this trend on the backhaul… 7
  8. 8. The challenges: How will operators deploy small cells? Resulting requirements for small cell backhaulJulius RobsonWireless Technology ConsultantLeader, NGMN Small Cell Backhaul Requirements 8
  9. 9. Why deploy small cells? …for Hot spots and Not spots macroEasing congestion New coverage inwithin macro coverage addition to macro A small cell will improve both coverage and capacity, but the primary motive is important when considering backhaul 9
  10. 10. Where will they be? Congestion on fully upgraded macro sites Need to densify Small No rooftop space left cells smaller units needed to fit available locations Smaller unit = less power = shorter range Small, low power cells •Small cell sites typically 4-6 m above street close to users level, on sides of buildings or street furniture Near street 10
  11. 11. Case study: what density of small cells is needed? •Case study of how demand density will be supplied with a mix of HSPA, LTE and small cells •Gives site densities and spacing 5 sites/km2 dense macro rooftop network Small cells exceed this in ~2013, requiring below rooftop Spacing will be lower than average in pockets of high demand ~100-200m Variation due to non uniform deployment •Assumptions Demand growth from PA consulting1 Spectral efficiency evolution Ofcom2 Macro site density 5/km2 (Holma3) Dense macro1 “Predicting areas of spectrum shortage”, PA Consulting, April 20092 "4G Capacity Gains", Real Wireless for Ofcom, Dec 20103 “LTE for UMTS: Evolution to LTE Advanced”, Harri Holma, Wiley 2010 11
  12. 12. The ‘what’ and ‘how’ of backhaul requirements Coverage1) Fundamentals Capacity Architecture Small Cell What Backhaul Cost Solution • Size & weight • Spectrum bands • Integration • Implementation 2) Practicalities Installation How • Backhaul features (QoS, Sync etc) • Availability/latency 12
  13. 13. The backhaul coverage challenge… PoP Small 13
  14. 14. Backhaul coverage requirementsCoverage from: Points of Presence− PoP locations: e.g. rooftop macrosites− PoPs density ~5 sites /km2 PoPCoverage to: Small cell sites PoP− Locations:4-6m above street level− Densities: increasing over time…− Estimate 30 sites per km2− ~100-200m spacing in areas of high demand Coverage = Connectivity between PoP and small cell sites …with sufficient 14
  15. 15. Quality of Service over Backhaul•Operators want consumer QoE to be independent of the access topology•Backhaul QoS should be driven by services offered•Some aspects of backhaul QoS may change according to deployment scenario: Small cell deployed primarily for… Aspect of backhaul QoS New coverage Easing congestion @Not Spot @Hot Spot Where easing congestion, RAN capacityAvailability same as macro relaxed should not be limited by the backhaulDelay (Latency, jitter) same as macro same as macro Where coverage overlaps, macro layerCapacity provisioning relaxed greater than small cell acts as fall back for small cells“Macrocells might be „quality not quantity‟ ….but the reverse is not true for small cells” 15
  16. 16. ?Backhaul capacity provisioning Assumptions HSDPA 2x2 64 QAM 6 42 Loaded Peak • Modified version of NGMN‟s macrocell backhaul capacity provisioning [1,2] DC HSDPA 2x2 64 QAM 12 84 • Includes user plane traffic plus overheads for transport, X2 and IPsec • Loaded macrocell throughputs scaled by LTE 10MHz 2x2 18 75 125% according to 3GPP simulations • [1] "Guidelines for LTE Backhaul Traffic LTE 20MHz 2x2 34 150 Estimation", NGMN Alliance, July 2011, • [2] “NGMN Alliance – Optimised backhaul solutions 0 50 100 150 200 for LTE, challenges of Small Cell deployment and Co- ordinated QoS”, NGMN Alliance, Layer 123 LTE/EPC DL Capacity Provisioning per small cell, Mbps & Converged Mobile Backhaul, December 2011 • [3] "Further advancements for E-UTRA physical layer aspects", 3GPP TR 36.814 V9.0.0 (2010-03)•Loaded figure represents busy times.•Peak represents maximum capability of the RAN during quiet times•Small cell sites will initially be single carrier, single cell and single generation, hence need less backhaul capacity than multi-sector, carrier and operator macros•This reduces on site aggregation gains so backhaul traffic will be 16
  17. 17. Backhaul cost requirements RAN Equipment backhaul Capex Installation $ TCO per site Site rental Opex Power leased line Last mile backhaul spectrum Maintenance etc…Cost per bit is likely to be similar to that of macro sites, but many small cells will be needed to supply same capacity as a macro …so cost per small cell site will need to be much 17
  18. 18. Physical design requirementsThe small cell and backhaul unit combined should be…•Small enough to fit in available street level locations − Planning/zoning may impose volume/dimension restrictions•Lightweight to facilitate installation Environmental − A one man lift & mount can reduce costs Size•Innocuous rather than sexy Appearance − Should not draw attention to itself Power Planning•Touch safe and tamper proof − Some sites may be within reach of the public Reliability ? Permission Installation & Connectivity Weight Commissioning Backhaul/RAN 18
  19. 19. How do different solutions compare?Lance HileyVP MarketingCambridge Broadband Networks 19
  20. 20. Small cell backhaul options Conventional PtP • For: High capacity • Against: Coverage awkward, spectrum opex, high installation costs E-band • For: High capacity • Against: High capex and opex Fibre (leased or built) • For: High capacity (if you pay enough) • Against: Recurring charges, availability and time to deploy Non-line of sight multipoint microwave • For: Good coverage, low cost of ownership • Against: Low capacity, spectrum can be 20
  21. 21. How does it all connect up - wirelesslyTree (point-to-point) Ring Mesh MultipointKey Links small cell low capacity pop high capacity with redundancy 21
  22. 22. Point-to-Point (PtP) microwavePtP Microwave• Lots of bandwidth microwave frequencies available at 10-60GHz − but oversubscribed in many urban centres• PtP spectrum is link-licensed; high recurring opex − Area licensing can address this when available• PtP links use two radios: each requiring space, installation, energy: high recurring opexPtP E-band• 10GHz of spectrum available at 71-76 and 81 GHz − a window between peaks of high atmospheric absorption• Light licensing conditions reduces spectrum opex in PtP The most common microwave topology many markets − For N links, 2N radios − Dedicated RF channel for each node B served − Well-suited to constant bit rate traffic − Well-suited to long links• Installation of equipment is trickier than conventional − Conventional and E-Band frequencies PtP Multiple radios, antenna’s per site to support ring/mesh topologies makes PtP difficult to deploy at street 22
  23. 23. FibreFibre•Great where already available, otherwise slow and costly to install•High-capacity, low-latency connection•High recurring cost – even in competitive markets UK published fibre pricing 34 mbps 140 mbps 280 mbps 500 mbps Installation $ 2,000 $2,000 $2,000 $2,000 Yearly rental fees $10,000 $14,000 $20,000 $30, 23
  24. 24. Non-line of sight (NLoS) microwave•Good for coverage, capacity limited by available spectrum•NLoS propagation requires low carrier frequencies prized for mobile access itself•Free spectrum worth every penny...but Wi-Fi uses the entire unlicensed low • Unpaired TDD spectrum could be used for NLoS frequency spectrum backhaul, but quantity of is small compared to the LTE and HSPA bands it has to backhaul•Spectral efficiency advances unlikely to compensate: access and •The 3.5 GHz band is large and backhaul operating in underused, however 3GPP is planning UMTS same (NLoS) environment (HSPA) and LTE 24
  25. 25. Line of sight (LoS) multipoint microwaveMultipoint microwave designed for street-level deployment High-capacity multipoint microwave operating at ETSI PMP frequencies: 10.5, 26 and 28GHz. Other bands in consideration Backhaul 8 remote terminals per access Multipoint microwave: fastest point with up to 300Mbps backhaul capacity growing microwave topology today − For N links, N+1 radios − Shared RF channel amongst all sites Integrated antenna for maximum − Well-suited to variable bit rate (bursty) traffic deployment flexibility/lowest operational − Well-suited to dense environments − Spectrum under-subscribed in most cost markets Point-to-Multipoint (PMP) aggregates packet traffic from multiple RT‟s Uses 40% less spectrum Only one radio per small cell site 25
  26. 26. Small cell backhaul revolution PMP hubs beam high-capacity multipoint bandwidth down urban canyons Large numbers of links for small cells, with high peak to average data traffic favour PMP aggregation 26
  27. 27. PMP best fit across small cell backhaul requirements•LoS PTP and eBand requirement of two radios per link impacts equipment/installation costs•NLoS wireless capacity is limited•Leased line connections have high repetitive costs•Wi-Fi range compromises backhaul 27
  28. 28. Architecture contributes to lowering cost of transport Small Cell TCO (Capex & Opex) •As traffic builds on a small cell £9,000 network, cost of transport £8,000 drops with all solutions £7,000 (blip seen for fibre caused by transitioning to higher-capacity Cost per Mb/s traffic carried £6,000 service) £5,000 •Multipoint architecture delivers £4,000 lower cost of transport sooner - £3,000 from the moment of installation £2,000 £1,000 £0 32 Mb/s 80 Mb/s 120 Mb/s 150 Mb/s Fiber, leased Eband PTP PMP Expon. (PMP) 28
  29. 29. Summary•Operators need high-capacity, low-opex backhaul for small cell network densification•Small cells needed to supply Hot Spots and densify network, offloading macro for high-mobility users•Multipoint LoS microwave is a mature technology option for backhaul: − High-capacity − Short deployment time − Low cost of ownership − Spectrum readily available•Cambridge Broadband Networks VectaStar Metro meets the small cell backhaul challenge• Read our whitepaper: 29
  30. 30. www.cbnl.comYour questionsLance Hiley: lhiley@cbnl.comJulius Robson: jrobson@cbnl.comDownload the white paper: © Cambridge Broadband Networks Limited. All rights reserved.