Converged Wireless Access: The New Normal

Transcription

1 Converged Wireless Access: The New Normal Karthik Sundaresan WNPE, Univ of Washington, June

2 5G Services Services drive network requirements for 5G Source: Ericcson 2

3 5G Services Services drive network requirements for 5G Wireless technology and access plays a critical role in this vision Source: Ericcson 3

4 Wireless Technology Evolution b SISO MIMO MU-MIMO a g n ac WiFi GPP 4

5 Wireless Technology Evolution WiFi a/b OFDM g MIMO n MU-MIMO ac Massive MIMO, mmwave 3GPP 5G 5

6 Access: Two Isolated Worlds WiFi - Asynchronous, distributed access - Asynchronous transmit/ receive - De-coupled downlink and uplink Cellular (LTE) - Synchronous, coordinated access - Synchronous transmit/ receive - Coupled downlink and uplink (BS schedules) 6

7 Convergence in Access? Licensed spectrum crunch - Supplement licensed with unlicensed channels Co-existence challenges - Co-existence with WiFi and other LTE operators - Asynchronous access in traditional synchronous network Source: Qualcomm LTE (1) Boundaries of access getting blurred Is this a one-off problem? Wi-Fi LTE (2) 7

8 A Paradigm Shift in Access Wi-Fi (1) Wi-Fi (2) Wi-Fi (3) LTE (1) LTE (2) New paradigm: Asynchronous Access with Opportunistic Synchronous Transmissions - Norm rather than exception in 5G Wi-Fi - Unlicensed LTE: one simple manifestation WiFi: synchronous transmissions (network MIMO) for capacity LTE: asynchronous access for co-existence, scalability, IoT NEMOx: Scalable Network MIMO for Wireless Networks, ACM MobiCom MIDAS: Empowering ac Networks with Multiple-Input Distributed Antenna Systems, ACM CoNEXT LTE 8

9 LTE-WiFi Co-existence Two modes of operation LTE-U - Duty cycling at time scales of 100 ms - Can be realized today: switch on/off unlicensed carriers Source: Cable labs 9

10 LTE-WiFi Co-existence LTE-U - Duty cycling at time scales of 100 ms - Can be realized today: switch on/off unlicensed carriers - Short-term unfairness to WiFi, higher latency Wi-Fi LTE CDF On 50 Off 10 On 10 Off 2 On 2 Off Inter-Packet Delay (ms) 10

11 LTE-WiFi Co-existence LTE-U - Duty cycling at time scales of 100 ms - Short-term unfairness to WiFi, higher latency LAA-LTE: License assisted access - Energy sensing CCA; Operation at 1-10 ms granularity - Modification to LTE specification for Listen-before-Talk Source: Cable labs 11

12 LTE-WiFi Co-existence LTE-U - Duty cycling at time scales of 100 ms - Short-term unfairness to WiFi, higher latency LAA-LTE: License assisted access - Energy sensing CCA; Operation at 1-10 ms granularity - Reduced throughput efficiency of smaller TxOP CDF On 50 Off 10 On 10 Off 2 On 2 Off Inter-Packet Delay (ms) WiFi Bitrate (Mbps) on-2-off 4-on-4-off 10-on-10-off 50-on-50-off SIR (db) 12

13 Challenge Im-balanced channel access - WiFi detects/notifies other WiFi through WiFi carrier sensing/notification (-84 dbm sensitivity) - WiFi-LTE detect each other through energy sensing alone (-62 dbm sensitivity) WiFi Bitrate (Mbps) dB 19dB 27dB LTE Power at STA (dbm) LTE Wi-Fi -62 dbm Wi-Fi LTE -84 dbm 13

14 Challenge Im-balanced channel access - WiFi detects/notifies other WiFi through WiFi carrier sensing/notification (-84 dbm sensitivity) - WiFi-LTE detect each other through energy sensing alone (-62 dbm sensitivity) Can we homogenize channel access policies to deliver better latencies, throughput efficiency? -62 dbm Wi-Fi LTE LTE Wi-Fi -84 dbm 14

15 Ideal Solution enodeb CC 1 MAC CC 2 MAC CC 5 MAC PHY PHY PHY WiFi sensing / notification WiFi sensing / notification WiFi sensing / notification WiFi sensing and preamble notification on every component carrier - Changes to the PHY; technology (WiFi) specific Scalable realization without PHY modifications? 15

16 ULTRON: Unlicensed LTE Radio Node Homogenized channel access WiFi Embedding - Embeds Tx notification (CTSto-Self) in LTE transmissions WiFi Sensing - Detects WiFi signals to realize -84 dbm sensitivity - Single WiFi sensing module spans multiple CCs; LTE scheduler balances traffic 1 Subframe LAA-LTE Subframes CTS LTE LTE LTE Energy or Carrier Sensing Time Total ON duration 16

17 ULTRON: Unlicensed LTE Radio Node Homogenized channel access - Detects WiFi signals to realize -84 dbm sensitivity - Embeds Tx notification to WiFi in LTE transmissions Efficient and fair LTE-WiFi co-existence (2x-3x gain) WiFi Throughput (Mbps) Ultron No Ultron SINR at STA (db) 3x LTE Throughput (Mbps) x Ultron LAA-LTE SINR at UE (db) 17

18 Summary Boundaries between synchronous and asynchronous access models will get blurred in 5G Need a deeper understanding of how to realize converged access - Several interesting and important problems - Critical for innovation in unlicensed spectrum: new operators and business models LTE-WiFi co-existence barely scratches the surface - Both technical and policy challenges Right time to get involved! 18

19 Thanks! Questions/Comments? 19

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