1. mZig: Enabling Multi-Packet Reception in ZigBee Linghe Kong, Xue Liu McGill University 2015-09-08 MobiCom 2015

2. MotivationMotivation 1 PreliminaryPreliminary 2 DesignDesign 3 ImplementationImplementation 4 Performance Evaluation 5 Table of Contents

3. Motivation Motivation 1 2 3 4 5 Table of Contents

4. ZigBee Communication Standard: IEEE 802.15.4 Applications: Sensor networks; Smart homes; Internet of things; Industrial control;...... 1 2 3 4 5

5. Convergcast in ZigBee Tree topology Cluster topology 1 2 3 4 5

6. Collision Problem Collision 1 2 3 4 5

7. Related Work Collision Avoidance CSMA/CA [JSAC'04,ToN'08] RTS-CTS [AHNet'03] backoff, hidden terminallatency Collision Resolution Analog NC [SigComm'07], XORs [SigComm'06], Full Duplex [MobiCom'11] Constructive Interference [IPSN'11, NDSI'13, TPDS'15] ZigZag [SigComm'08] partial known infosame content retransmission required 1 2 3 4 5

8. 1 Preliminary Preliminary 2 3 4 5 Table of Contents

9. ZigBee Specification FrequencyCoverage Data Rate # of Channels Rx Sensitibity Modulation 2.4GHzWorld250kbps16-85dBmO-QPSK 868MHzEurope20kbps1-92dBmBPSK 915MHzUSA40kbps10-92dBmBPSK 1 2 3 4 5

10. Baseband Signal in ZigBee 1 2 3 4 5

11. Features of ZigBee Chips Oversampling: sampling rate of recent ADCs (at RX side) is much higher than 2MHz. Known shaping: half-sine. Uniform amplitude: O-QPSK, no ASK or QAM. How to leverage these features to design mZig? 1 2 3 4 5

12. 1 2 Design Design 3 4 5 Table of Contents

13. A Novel Technique: mZig 1 2 3 4 5 mZig leverages the physical layer features and decomposes a multi-packet collision directly. Example: a two-packet collision.

14. Two Categories of Collisions with chip-level time offset (w/ CTO) 1 2 3 4 5 without chip-level time offset (w/o CTO)

15. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5

16. CrossIC 1 2 3 4 5

17. CrossIC 1 2 3 4 5 Collision-free samples Step I: Extract collision-free samples

18. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5 Estimated samples Step II: Estimate samples to form a whole chip

19. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5 New collision-free samples Substract the estimated chip from the collision

20. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5 Repeat the extraction and estimation steps

21. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5 Repeat the extraction and estimation steps

22. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5 Repeat the extraction and estimation steps

23. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5 Repeat the extraction and estimation steps

24. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5 Repeat the extraction and estimation steps

25. CrossIC Cross Interference Cancellation (CrossIC) for collision w/ CTO. 1 2 3 4 5 Repeat the extraction and estimation steps

26. AmpCoD Amplitude Combination based Decomposition (AmpCoD) for collision w/o CTO. Assume α>β L1L1 α+β L2L2 α-βα-β L3L3 -α+β L4L4 -α-β-α-β 1 2 3 4 5

27. Core Design CrossICAmpCoD Design Enhancement Time Offset Detection Anti-Noise Multipath Filter Frequency Offset Compensation Scope m-Packet Collision Bluetooth & WiFi 1 2 3 4 5

28. 1 2 3 Implementation Implementation 4 5 Table of Contents

29. RX PHY: ZigBee v.s. mZig 1 2 3 4 5

30. DmZig Module 1 2 3 4 5

31. Testbed RX: USRP X310 + PC TX: USRP B210*6 + Laptop*6 + iRobots*6 1 2 3 4 5

32. 1 2 3 4 Performance Evaluation Performance Evaluation 5 Table of Contents

33. Experiment Setting Configuration Sampling rate: 32Msps TX power: 0dB (1mW) Channel selection: 26 1 2 3 4 5Field 7.5m×6.8m office Metrics Bit Error Rate (BER) Throughput Compared with ZigBee ZigZag

34. BER: Different Sampling Rates 1 2 3 4 5 Reference

35. BER: Different Techniques 1 2 3 4 5 Reference

36. Throughput: Different Techniques 1 2 3 4 5

37. 1 2 3 4 5 4.5X 1X

38. Throughput: Static v.s. Mobile 1 2 3 4 5

39. Conclusion We design mZig, a novel RX design to enable multi-packet reception in ZigBee. Theoritcally, the maximal concurrent transmissions is m=S/2C. We implement mZig on USRPs. In our testbed, the throughput of mZig achieves 4.5x of ZigBee with four or more TXs. 1 2 3 4 5

40. 40 Q & A linghe.kong@mail.mcgill.ca

41. Backup

42. PHY in ZigBee

43. Time Offset Detection

44. Anti-Noise Design For CrossIC For AmpCoD

45. Multipath Filter Channel estimation is required to estimate the impulse responses of multipath. Multipath effect is filtered chip-by-chip.

46. Frequency Offset Compensation Channel estimation is also required to estimate the frequency offset. Compensate the frequency offset chip-by-chip.

47. Scope m-Packet Collision in ZigBee Bluetooth WiFi

48. MAC for mZig The conventional MAC for ZigBee cannot be applied directly: –CSMA/CA –ACK

49. Simulation Impact of CTOImpact of SNR

50. Simulation (cont) Multipath FilterFreq. Compensation