BEST Paper MobiCom 2017 Zhijun Li and Tian He

Transcription

1 BEST Paper MobiCom 2017 Zhijun Li and Tian He Computer Science and Engineering University of Minnesota

2 Wireless is Everywhere <wigle.net> 2

3 and Increases Rapidly 1.8B ~4B 130M Source: ABI Research Source: Navigant Research Gartner predicts 20 billion IOT devices by year

4 also Diversifies Quickly 4

5 Coexist and Collaborate Network of Things Thermostat Smoke detector Humidity detector Many more PAN LAN WAN Smart Hospital

6 Objective: Ubiquitous Connectivity Q: How to Interconnect/bridge them? WAN LAN PAN PAN 6

7 Bridging Wireless Tech: Gateway MutiRadio Gateway Extra HW/deployment cost Traffic overhead into/out of the gateway Pre-deployment, unsuitable for ad hoc/mobile 7

8 The New Paradigm: CTC Cross-Technology Communication (CTC) enabling heterogeneous devices talks directly! 8

9 What CTC can Achieve: Low Cost A WiFi AP controls all smart home ZigBeeenabled devices in one hop without gateway 9

10 What CTC can Achieve: Mobility VANET Battle Field Inventory Tracking Wearables Direct Communication among mobile IOT devices without pre-deployed gateways 10

11 What CTC can Achieve: Coordination Support Explicit channel coordination No traffic next 20ms I need next 200ms Time Wifi ZigBee Wifi Extends local mechanisms globally across wireless tech Global RTS/CTS Reservation. Global Time Division Multiple Access (TDMA) 11

12 WEBee Physical-Layer Cross-Technology Communication WEBee: WiFi Emulated ZigBee 12

13 Outline The State of the Art The Design Implementation & Evaluation Extensions 13

14 The State of the Art 14 14

15 A Brief History of CTC Research Packet-level CTC Using packet length, gap, or offset A packet can only express a few bits Energy (RSSI) ESENSE Packet Length K. Chebrolu 1 0 GSense Gap Length X. Zhang 1 time HoWiES Comb. Packet Length Y. Zhang WE ARE HERE FreeBee Beacon Interval S. Kim 16,000X Faster!!! PHY CTC 100s Kbps bps bps bps Mobicom 2009 INFOCOM 2013 MobiCom 2015 MobiCom

16 A Brief History of CTC Research Physical-Level CTC By emulating receiver s RF waveform, A packet achieves Rx s maximum rate I/Q RSSI In-phase Quadrature time WE ARE HERE 16,000X Faster!!! PHY CTC 100s Kbps bps bps bps Mobicom 2009 INFOCOM 2013 MobiCom 2015 MobiCom

17 The Design 17 17

18 The Key Idea of WEBee WiFi Sender WiFi Frame with selected Payload Emulated ZigBee Signals ZigBee Receiver ZigBee Frame Ignore Ignore ZigBee Compatible Signal 18

19 Challenges of Physical-Layer CTC Modulation: QAM, OFDM Rate: ~54Mbps (802.11g) Distance:300m Tx:26dBm Sensitivity:-80dBm Key Innovation Signal Wi-Fi Sender Without translator Modulation : OQPSK, DSSS Rate: ~250Kbps Distance:100m Tx:0dBm Sensitivity:-97dBm 19

20 How Wi-Fi Transmits Channel Coding Wi-Fi Frame payload Scrambler Convolutional Encoder Modulation (QAM) Coded Bits Interleaver Pilot Insertion IFFT Cyclic Prefixing Post-QAM Processing Wi-Fi Signal 20

21 Emulation via a Reverse Path Channel Coding Emulation Wi-Fi Frame payload Scrambler Convolutional Encoder Coded Bits Interleaver QAM Emulation Modulation (QAM) Transmission Emulation Pilot Insertion IFFT Cyclic Prefixing Post-QAM Emulation ZigBee Signals To be Emulated 21

22 QAM Emulation RF Signal Spectrogram in the Air Mimic OQPSK signals 22 QAM/OFDM signals

23 Minimizing Emulation Distortion Minimizing emulation distortion in the time-domain is equivalent to minimizing the total deviation of frequency components (based on Parseval s theorem) FFT QAM Emulation Desired Time-domain ZigBee Signals Corresponding Frequency-domain Components 23 The Closest Wi- Fi QAM Points

24 Other Technical Challenges Reverse channel coding Parallel CTC For details, refer to the paper Pilot/Null avoidance Link-level reliability 24

25 Innovative Features of WEBee 25 25

26 Dual-Standard Compliance A part of WiFi frame is a Zigbee frame 26 26

27 No change in Sender s Hardware/Firmware Send a normal WiFi Frame 27 27

28 No change in receiver s Hardware/firmware Receive a normal ZigBee Frame 28 28

29 Combine the advantages of two technologies. Tx:26dbm Sensitivity:-65dbm Big Mouth Rx:0dbm Sensitivity:-97dbm Good Ear WEBee has a longer range than Wi-Fi! 29 29

30 Support parallel CTC in one WIFI Packet 2MHZ 20MHZ 2MHZ Simultaneous Unicast 30 30

31 Support high mobility and duty cycled operations Longer Range, better mobility Low Power Listening 31 31

32 An 16,000x faster CTC with 99.9% reliability For details referring to our mobicom 2017 paper 32 32

33 Implementation & Evaluation 33

34 System Implementation Sender AR2425 Receiver WiFi(Commodity) AR9485 RX Wi-Fi Frame Smartphone LG Nexus 5 ZigBee(Commodity) CC2420 RX ZigBee Frame USRP N210 ZigBee(USRP) N210 RX ZigBee Frame 34

35 Experimental Setting Lab Hallway Outdoor Experiment setting 10,000 runs each trial Varying distances Varying Tx Power Varying packet length Varying content Varying duty-cycle Varying Mobility 35

36 Symbol Error Ratio vs Data Rate FreeBee [Mobicom 15] 99% WEBee [Mobicom 17] 99% 36 ~8,000x Speed up *250kbps theoretically

37 Frame Reception Ratio A frame fails with one symbol error WEBee(Commodity) AR2425 WEBee(USRP) N210 ZigBee CC2420 Recept. Ratio (%) ~50% 0 WEBee(USRP) è ZigBee WEBee(WiFi) è ZigBee 37

38 Reliability after Retransmission 99% after 6 retransmissions Less re-tx with Repeated preamble and coding 38

39 Parallel CTC With two channels, WEBee vs. FreeBee = ~16,000x 39 Channel I Channel II

40 WEBee in Action 40 40

41 WEBee Demo 41

42 Application: Smart Light Control You can control ZigBee Smart Bulb with WEBee Vs. GE Gateway Solution WeBee Solution 42

43 Release: WEBee Payload Generator V1.o You can conduct cross-technology research using WEBee Generator! Available at: Possible New Topics: Channel Access Control Coordination Neighbor Discovery Multi-Technology Routing CTC Time Synch. CTC Localization.. 43

44 Extension 44 44

45 Question: Whether Signal Emulation is a generic technology? 45

46 BlueBee: BlueTooth to ZigBee [SenSys 17] 46

47 LTEBee: LTE (band 7) to ZigBee LTE smartphone controls a CC2530 ZigBee Blub directly after 7-layers channel coding and 6-step modulation. 47

48 Conclusion WEBee is the first physical-layer CTC design, a paradigm shift with a significantly higher throughput, while requiring no change of HW. Our work indicates Signal Emulation is a generic technology to build light-weight SDR, striking a delicate balance between flexibility and cost. Our work brings a surge of opportunities to expand many local wireless mechanisms globally (e.g., coordination, discovery, etc.) across technologies. 48

49 CTC Technical Support is available at 49

50 Can support two-way Long Range Wake Master Node Always On Mode Slave nodes Duty-Cycle Mode 50 50

51 Opportunity for Cross-Tech.-Comm. Wireless technologies share unlicensed ISM bands, offering opportunity for cross-tech. communication <ni.com> Channel Center Frequency (MHz) <digikey.com> 51

52 Channel Mapping OFDM Has 64 subcarrier, 48 data, 12 null and 4 pilot 52

53 Four-to-one emulation Four Wi-Fi symbols are used to emulate one ZigBee symbol 53

54 Link Layer Reliability Repeated preamble and hamming coding 54