Spectrum sharing issues for small cells

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From Cambridge Wireless Small Cells SIG event:
http://cambridgewireless.co.uk/sigs/smallcell/

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Spectrum sharing issues for small cells

  1. 1. Spectrum sharing issues for small cells Michael Fitch – 29th March 20121
  2. 2. Roadmap of talkWhy small cellsWhy spectrum sharingA bit on TV WhitespaceSpectrum sharing managementChallenges and (potential) solutions to spectrum sharing2
  3. 3. Users are demanding more bandwidth Orange reported 4,125% increase in traffic last year, 100% increase in last 3 months. Cisco predict demand Nokia Slide – LTE global summit doubling every year for next 5 years.3
  4. 4. LTE Network Roll-Out Uk Subscriptions by 2G/3G/4G technology 90,000 80,000 subscriptions (thousands) 70,000 60,000 50,000 LTE 40,000 3G 30,000 GSM 20,000 10,000 0 2008 2009 2010 2011 2012 2013 2014 2015 Source: Ofcom  Likely Roll-out: – Link in with 2G refresh – installation of multi-mode radios – Start with: – major cities where most data traffic is generated – macro-cells; later small outdoor cells and indoor femtocells – high-end traffic users4
  5. 5. WiFi-LTE Scenarios Small cells limited by Relative costs of provisioning indoor coverage availability of sites Not to scale: Macro-cells limited by available spectrum Femtocells currently Cost ~$150 each, ultimately limited by interference 5GHz WiFi limited by coverage 2.4GHz WiFi limited by interference Capacity for a given indoor area5
  6. 6. WiFi-LTE Scenarios Relative costs of provisioning indoor coverage Not to scale: 2014-2015: When femto-cells hit the right price point networks will consider large-scale 2013-2014: deployment Most networks will start roll-out Cost 2013: All small cells networks will start roll out Macro-cellular networks 2011 onwards: To varying degrees MNOs will invest in WiFi offload Capacity for a given indoor area6 Time
  7. 7. LTE femtocells may be part of an overall deployment• LTE femtocell reference designs announced by vendors.• LTE femtocells are part of the overall standards. Available closed, hybrid and open access modes.• Trials in 2011, Commercial units available in 2012.• Outdoor femtocells with higher power and more complexity.• Multi radio femtocells not seen as essential at the moment.7
  8. 8. BT’s 1.5 million hotspots, one billion minutes 1.35m+ enabled Home Hubs 150k+ enabled Business Hubs 3.8k premium hotspots8
  9. 9. BT WiFi cells BT Infinity is BT Retail broadband service connected using Openreach NGA HH3 senses the channels 1 – 11 and chooses one with low congestion. Noise floor and beacons are sensed Home Hub 3 Openzone and HH access points (including Fon access) are backhauled to the same datacentres 4 datacentres provide authentication, billing, roaming policies Hot-spot 2 is work in progress, which will support 802.1x, roaming for different operators, automated sign-up, handover to / from 3G networks, operator policy controlBT business and public hotspots9
  10. 10. But WiFi is getting congested… This is what I see in my office…. and there are 3 more below the picture.. Distribution of FTTC / VDSL will add pressure, Moving to 5.4GHz has coverage issues10
  11. 11. What are the trends ? Increasing data traffic, mostly from within buildings Increasing WiFi offload Cells are getting smaller WiFi is ‘loose’ – suffering from increasing congestion and decreasing coverage LTE is ‘tight’ – suffering from single MNO per BS, lack of spectrum – planning is increasingly infeasible Is a solution something in-between unlicensed and licensed, ie smart spectrum sharing ? – on backhaul and access ?11
  12. 12. Regulators are encouraging a move from binary licensedunlicensed towards greater intelligenceand flexibility Planning is becoming infeasible12 Estimate we are here
  13. 13. Coverage of different frequency bands Area – 1sq km in London, household density 5k (a) 5GHz (b) 2.4GHz (c) 700MHz13 13
  14. 14. Coverage of different frequency bands Area – 1sq km in London, household density 5k (a) 5GHz (b) 2.4GHz (c) 700MHz Sharing the airwaves with DTV provides coverage similar to a mobile broadband network – with a 20% deployment density, from indoors….14 14
  15. 15. What is TV Whitespace spectrum ? - the UK plan... 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 • 16 channels (128MHz) of cleared spectrum for auctions (2012) • 32 channels (256MHz) interleaved spectrum retained for: • Licensed Primary Usage for Digital Broadcasting • Licensed Secondary Usage for Wireless Microphones • Unlicensed Secondary Usage – sharing- 38 • 1 channel (8MHz) dedicated to Radio Microphones 15
  16. 16. Exploring use of TV Whitespace: Licensed, unlicensed, primary and secondary Licensed and unlicensed Licensed and unlicensed in separate spectrum sharing the same spectrumThe order of access priority is Licensed Primary (eg DTV), Licensed Secondary,(eg wireless microphones), Unlicensed Secondary (everything else)Sharing is free, but must not cause harmful interferenceto systems higher up the pecking order16
  17. 17. Spectrum management using a database 1 Request list 2 Get list 3 Contact a dB with location, uncertainty and other optional information 4 Get list of available channels / powers and time to live and other optional information17
  18. 18. Need a feedback path 1 Request list 2 Get list 3 Contact a dB with location, uncertainty and other optional information 4 Get list of available channels / powers and time to live and other optional information 5 Inform database which channels have been chosen The IETF PAWS WG is defining this protocol18 - And use-cases / requirements and security aspects
  19. 19. We also need fairness etiquette between secondary systems Fairness between these guys - Brokering ? Contention ? SON ? Regulators are not interested in this critical issue ! Regulators want to certify database algorithms This, and the issue of fairness, are likely to be the critical lines19 to deployment.
  20. 20. But I think we need even more than this…. To and from repositories of TV coverage, PMSE usage, [emergency services etc] Spectrum portfolio manager 3rd party (centralised) database in two steps Spectrum portfolio for region, (QoSMOS with quality measures approach)Location of BS Resource managerLocations of end users (distributed) – to cope with many systemsConfidence levelsAntenna characteristicsSensing information Available channels and powersQuality requests Quality of channelsMobility requests Time of relevanceWhat channels and powers are chosen Others ?Others ?20
  21. 21. Regulatory position - briefly Considerable effort will be needed to establish trust with Ofcom and with primary users of the spectrum (DTV and Wireless Microphones) – through trials / standards Ofcom indicate a 2-year process so we may go live in 2013. A VNS and Interface Specification will be published this year. Vendors will self-certify against the VNS An SI is also being drafted to allow unlicensed equipment to operate in the band Ofcom have started a WI in ETSI BRAN. Position in other European countries is lumpy: German / French very cautious for a number of reasons Swiss /Dutch / Finnish / Polish more open and looking to FCC / Ofcom for lead21
  22. 22. Trials and standards  Isle of Bute and Cambridge trials in UK (rural broadband) – Proved TV WS can deliver >30Mbit/s and reach 8km with 2Mbit/s with 4W eirp, few users (10) – Database integration for channel selection and power control (using BT prototype database)  Further trials proposed – In Suffolk (rural broadband) to evaluate contention and interference, more users (30) – Indoor networking with small cells (a few houses)  Standards focus – IETF PAWS – ETSI RRS and BRAN – IEEE, especially P1900.7 – SE4322
  23. 23. Challenges and (potential) solutions to sharing  PHY and MAC layer – Without interfering with adjacent services, needs to be better than OFDM – To support enough data-rate (30Mbit/s ?), so channel bonding – Potential solution: FBMC  Protection margins to be agreed – Sets power within the cells – Potential solution: measurements from trials and working with stakeholders  Database and sensing algorithms – Etiquette needed for fairness – Scalable to large numbers of small cells – Potential solution: distributed database structure and algorithms with sensing  Eco-system development – Need to increase confidence in vendors and regulators – Potential solution: trials and standards activity23
  24. 24. Thank you for listening24

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