NTT DOCOMO's Views on LTE Unlicensed

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NTT DOCOMO's Views on LTE Unlicensed

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NTT DOCOMO's Views on LTE Unlicensed

  1. 1. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 1 NTTNTT DOCOMO'sDOCOMO's ViewsViews on LTE Unlicensedon LTE Unlicensed NTT DOCOMO, INC.NTT DOCOMO, INC.
  2. 2. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 2 Background • More spectrum is needed for cellular operators to meet the increasing traffic demand. • Although licensed spectrum is always preferable for providing better user experience, unlicensed spectrum can be considered as an effective complement. • Operators should endeavor for higher spectral efficiency and better user experience. If LTE unlicensed has such potentials, this should be studied. – The first step is to clarify the overall system performance and user experience with LTE unlicensed. – Since unlicensed spectrum has been widely used by Wi-Fi and some operators have deployed operator managed Wi-Fi systems, coexistence with Wi-Fi needs to be carefully considered.
  3. 3. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 3 Motivation Compared to Wi-Fi, e.g., IEEE 802.11ac, •Potentially higher spectral efficiency by use of advanced technologies of LTE, such as robust FEC, hybrid ARQ, channel estimation, and interference coordination/ avoidance. •Better user experience due to tighter interworking between licensed and unlicensed bands. In addition, •LTE unlicensed will provide more choices for operators to utilize unlicensed bands with technology that best fits with the deployment scenario. – Although drawbacks of market fragmentation and migration scenarios need to be carefully considered.
  4. 4. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 4 General scope of study • Investigation and evaluation to clarify whether LTE unlicensed can bring benefits over the existing Wi-Fi (802.11ac) • Investigate coexistence with existing technologies, e.g., IEEE 802.11ac, from performance perspective. • LTE enhancements and optimization for use on unlicensed bands • Study the necessity of different levels of offloading with no/minimum impact to the existing NW architecture, and their respective deployment scenarios (more details on subsequent slides).
  5. 5. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 5 Spectrum and regulatory aspects in Japan • Overview of spectrum and regulatory aspects for Wi-Fi on 5 GHz – Note that 5.725-5.825 GHz is not available. • The above regulatory aspects need to be taken into account in LTE unlicensed studies. – Note that there are additional regulatory requirements, e.g., on max transmission power/ e.i.r.p., unwanted emission. Frequency band 5.15-5.25 GHz 5.25-5.35 GHz 5.47-5.725 GHz Allowed usage scenario Limited to indoor Indoor and outdoor Carrier sense Required for co-existence DFS and TPC N/A Required to prevent harmful interference to radars and satellite systems Max Burst Length <4 ms DFS: dynamic frequency selection; TPC: transmission power control
  6. 6. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 6 Potential deployment scenarios • Various deployment scenarios can be considered. – Colocate/Non-colocate – Outdoor/Indoor Licensed macro cell Unlicensed small cell Licensed small cell Freq Tighter interworking w/ LTE licensed CA Dual connectivityDual connectivity /CA Stand-alone 800MHz 3.5GHz 5GHz Examples of potential deployment scenarios • CA scenario offers the tightest interworking with LTE licensed • However, other scenarios may be beneficial in terms of offloading effect Our prioritized target
  7. 7. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 7 Potential architecture (1) • Different benefits are achievable depending on NW-architectures Tighter interworking w/ LTE licensed Wider offloading region IP Core RAN LTE licensed LTE Unlicensed? LTE Unlicensed? LTE Unlicensed?
  8. 8. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 8 Data split point RAN Core Outside Backhaul condition Ideal Non-ideal - - Interworking w/ licensed LTE Very tight Tight Medium/Loose Loose/NA Air-IF offload Yes Yes Yes Yes RAN-offload No No Yes Yes Core-offload No No No Yes Use case Public Public Public/home Public/home Outdoor/indoor Outdoor/indoor Outdoor/indoor Outdoor/indoor • There could be different pros/cons on different NW architectures • Careful study is needed among potential use-cases/NW architectures Potential architecture (2) • Different benefits are achievable depending on NW-architectures
  9. 9. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 9 List of potential requirements and performance metrics • Capability-related – Peak data rate – C/U-plane latency • System performance – Spectrum efficiency – Typical user throughput (e.g., 95%, 50%, 5% point of CDF of user throughput) – Mobility – Coverage • Deployment-related – Deployment scenarios – Coexistence with other systems – Traffic offload scenarios • Complexity • Cost-related • Service-related – Charging
  10. 10. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 10 Required new features for LTE Unlicensed • Listen before talk – Needed for interference avoidance between LTE unlicensed + LTE unlicensed devices and/or between LTE unlicensed + Wi-Fi devices – Dynamic • DFS/TPC – Needed to satisfy regional requirements • LTE enhancements and optimization for use on unlicensed bands
  11. 11. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 11 Summary  Investigation and evaluation are necessary to clarify whether LTE unlicensed can bring benefits over the existing Wi-Fi (802.11ac)  Coexistence with existing technologies, e.g., IEEE 802.11ac, should be investigated from performance perspective  Careful study is needed among potential use-cases/NW architectures ‒ CA / dual connectivity based scenario for LTE unlicensed should be treated in the SI(s) from the standardization point of view ‒ Necessity of other scenarios, e.g., loose interworking with licensed LTE, should be also discussed  The existing Rel-12 SI/WIs should be prioritized to LTE unlicensed SI ‒ If there is a room to start new topics in RAN1, the LTE unlicensed SI could be started after June (or possibly March) 2014 ‒ If needed, LTE unlicensed SI in RAN could be started before start of RAN1 SI
  12. 12. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 12 [Annex] Spectrum and channel arrangement for wireless LAN in 5 GHz 5470 5570 5725 MHz5510 5550 5590 5630 5670 5150 52505190 5230 5270 5310 5350 MHz Meteorological radar/ Earth exploration-satellite Mobile satellite feeder link Various kinds of radar systems : For wireless LAN : 20MHz system(802.11 a/j) : 40MHz system(802.11 n) : 80MHz system(802.11ac) : 160MHz system(802.11ac) : system co-existing with wireless LAN
  13. 13. NTT DOCOMO, INC., Copyright 2014, All rights reserved. 13 [Annex] Regulatory requirements for wireless LAN in 5 GHz Frequency 5.15-5.25GHz 5.25-5.35GHz 5.47~5.725GHz Location Limited to indoor Indoor and outdoor Channel bandwidth 20/40/80/160MHz Modulation 20MHz OFDM, DS, single carrier(Note 1) 40/80/160MHz OFDM Maximum output power 20MHz 10mW/MHz for OFDM and DS 10mW for single carrier 40MHz 5mW/MHz 80MHz 2.5mW/MHz 160MHz 1.25mW/MHz Maximum antenna gain Any Maximum e.i.r.p. 20MHz 10mW/MHz 50mW/MHz 40MHz 5mW/MHz 25mW/MHz 80MHz 2.5mW/MHz 12.5mW/MHz 160MHz 1.25mW/MHz 6.25mW/MHz Carrier sense 20/40/80/160MHz Required DFS, TPC(Note 3) Not required Required (only for master control station ) Connection topology Any Any (connection between the stations not controlled by master control station is not allowed) Note 1:OFDM(Orthogonal Frequency Division Multiplex), DS( Direct Sequence) Note 3:DFS(Dynamic Frequency Selection), TPC(Transmitter Power Control) Note 2: For FH in 2.427-2.47075GHz, 3mW/MHz, for OFDM or DS without FH, 10mW/MHz and for the others, 10mW

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