3GPP workshop - LTE in unlicensed spectrum


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  • MSA
  • TPC and DFS are to satisfy regulatory requirements
  • -. 5 GHz unlicensed band : Top candidate
  • 3GPP workshop - LTE in unlicensed spectrum

    1. 1. WiFi-LTE Coexistence in Unlicensed Band 3GPP Workshop on LTE in unlicensed spectrum Nadisanka Rupasinghe Dept. of Electrical and Computer Engineering Florida International University 06/13/2014
    2. 2. Why unlicensed band? • 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. 2
    3. 3. Licensed-assisted access (LAA) 3 What is LAA? A Wireless technology that is operating in unlicensed band in order to improve performance of another (or can be the same) wireless technology operating in licensed band LTE as LAA is preferred over WiFi • Better traffic offloading • Higher user experience • Tighter interworking with licensed and unlicensed bands (Single RAT) • Better spectrum efficiency compared to WLAN
    4. 4. LAA with LTE 4
    5. 5. 5 Which Band is preferred? (1) US 1 Europe 2 Japan China Korea 5.15GHz-5.25GHz (100MHz) Indoor/Outdoor(U- NII-1) Indoor (Band A) Indoor/Satellite Indoor/DFS/TPC Indoor 5.25GHz-5.35GHz (100 MHz) DFS/TPC (U-NII-2A) ACA/DFS/TPC (Band A) Indoor/DFS/TPC Indoor/DFS/TPC DFS/TPC 5.35GHz-5.470GHz (120 MHz) (U-NII-2B) under study No under study under study 5.470GHz-5.650GHz (180 MHz) DFS/TPC(UNII-2C) ACA/DFS/TPC (Band B) DFS/TPC In consideration DFS/TPC 5.650GHz-5.725GHz (75 MHz) DFS/TPC/RADAR (UNII-2C) ACA/DFS/TPC (Band B) DFS/TPC In consideration Bcast Relay Service 5.725GHz-5.825GHz (100MHz) Yes (UNII-3) DFS/RADAR (Band C) No Licensed (3 operators) EIRP 10 mW, Center Freq 5.775GHz (allocated for WDCS) 5.825GHz - 5.850GHz (25MHz) Yes (UNII-3) DFS/RADAR (Band C) No Yes Under Study 5.850GHz - 5.875GHz (25MHz) UNII-4 RADAR (Band C) No under study under study 5.875GHz-5.925GHz (75MHz) U-NII-4 under study No under study under study 1 FCC Revision of Part 15 for Operation of Devices in 5GHz, NPRM, April 2014 2 ETSI BRAN DFS : Dynamic Frequency Selection TPC : Transmit power control
    6. 6. 6 5 GHz Unlicensed band is highly preferred Dynamic frequency selection (DFS) and Transmit power control (TPC) To overcome interference to Radar transmission and other technologies Which Band is preferred? (2) For Europe :
    7. 7. 7 Feasibility of DFS in LTE (1) Basically proposed to avoid interfering with Radar. But can use with other technologies?
    8. 8. 8 DFS detection threshold  Detection threshold is specified to detect signals from Radars that can be interfered by max EIRP of UE or eNB transmitter.  If DL only secondary CC, then only eNB needs to implement DFS Feasibility of DFS in LTE (2)
    9. 9. 9 Proposed Deployment Scenarios(1) Small Cell LAA Macro Cell  LAA as a means of Carrier Aggregation with Licensed operation & achieving Dual connectivity
    10. 10. Different types of Interference 10 Inter-RAT interference • LBT based on Energy detection approach Intra-RAT interference (Inter- & Intra- operator) • Coordination between LAAs with ICIC & CoMP • Using Adv. Receivers with assuming sync. Even Between LAAs of diff. operators
    11. 11. Information Exchange between Operators 11 Common Database Information sharing between operators using a common database This will enable intelligent channel selection/allocation for LAA LTE
    12. 12. What can we do with LAA? 12 LAA for Carrier Aggregation/Supplemental DL (SDL) Accompanied by a Licensed Primary Carrier Primary Carrier • FDD or TDD • Control signaling, Mobility, user data Same RAN for Licensed and Unlicensed access Secondary Carrier • Best effort user data in DL or both UL & DL
    13. 13. Coexistence Performance Evaluations (1) 13 WiFi 802.11n and LTE coexistence performance evaluation eNodeB Wi-Fi AP Wi-Fi Client Locations Fixed Scenario Modeled in Lab Setup Distance • Wi-Fi throughput diminishes as LTE transmission moves closer to Wi-Fi devices Due to SINR degradation WiFi ED threshold (-62dBm) Not system level simulations ??
    14. 14. 14 Coexistence with Duty Cycle LTE LTE On LTE On LTE Off Duty Cycle Period Duty Cycle: % of cycle LTE is active time Wi-Fi access gaps when LTE is off WiFi T’put vs LTE Duty cycle and periodWiFi 95th percentile delay vs LTE Duty cycle and period
    15. 15. 15 U-LTE (Operator B) U-LTE (Operator B) WiFi (Operator A) WiFi (Operator A) U-LTE (operator B) U-LTE (operator A) U-LTE (operator B) U-LTE (operator A) Coexistence Performance Evaluations (2)
    16. 16. 16 3 carriers available for U-LTE deployment from operator A (U-LTE) and operatorB (WiFi) • Baseline: no carrier selection (co-channel deployment) • Random carrier selection: each U-LTE eNB/WiFi AP selects one unlicensed carrier randomly • Channel-sensing based Carrier selection : each LTE node selects one interference-less unlicensed carrier ~x 1.5 ~x5 Coexistence Performance Evaluations (3)
    17. 17. Proposed Coexistence Mechanisms 17 Investigating the importance of using WiFi packets and methods in LAA LTE • physical RF sensing and virtual carrier sensing (802.11 NAV func.) • eNB transmitting WiFi like Beacons, so that WiFi STAs/APs can detect/avoid the eNB Investigating methods for information exchange and Management • Geo location information of WiFi access points and LTE-U eNBs • AP and eNB channel allocation statistics • Interference characteristics based on calculation and measurements
    18. 18. In-device coexistence of LAA LTE and WiFi 18 Dual Operation • UE receives video over LTE + LTE-U • UE relays the video over WiFi to TV • UE has to coordinate between LTE-U reception and WiFi transmission (same device). A TD protocol is required for WiFi Tx and LTE-U Rx co- existence
    19. 19. Hidden node problem for unmanaged WiFi 19  UE1 : Communicating with Home WiFi AP  UE2 : Communicating LTE-U eNB  Home WiFi AP signal -> Interfere To UE2 Remote sensing mechanism for optimized channel selection
    20. 20. Conclusion • 5 GHz unlicensed band is identified as the preferred band for LAA operation • DFS and TPC to coexist with other technologies in unlicensed band - LBT implementation in LTE for medium sensing • Different deployment scenarios for different requirements • LAA-LTE to achieve CA/SDL – FDD • LAA-LTE as a separate cell - TDD 20