Towards Instantaneous Collision and Interference Detection using In-Band Full Duplex

Transcription

1 Towards Instantaneous Collision and Interference Detection using In-Band Full Duplex Tom Vermeulen, Mihir Laghate, Ghaith Hattab, Danijela Cabric, and Sofie Pollin Department of Electrical Engineering, KU Leuven, Heverlee B-3001 Belgium Department of Electrical Engineering, UCLA, Los Angeles CA 90024, USA

2 Outline In-band full duplex Problem formulation: Collision detection at transmitter Motivation: Energy and throughput gains Feasibility: Sensitivity requirements Evaluated detection techniques Experiment design and evaluation Conclusion 2

3 In-band full duplex Simultaneous transmit and receive Same time and frequency slot 3

4 In-band full duplex Simultaneous transmit and receive Same time and frequency slot Problem: Self Interference (SI) saturates receiver Solution: Self Interference cancellation in two forms Analog cancellation achieves 50 to 70 db Digital cancellation up to 30dB further 4

5 In-band full duplex Simultaneous transmit and receive Same time and frequency slot Problem: Self Interference (SI) saturates receiver Solution: Self Interference cancellation in two forms Analog cancellation achieves 50 to 70 db Digital cancellation up to 30dB further replaced by our collision detector 5

6 Problem formulation Data 6

7 Problem formulation Data Collision 7

8 Problem formulation X n Data Y n h tt h it Collision h Y n = ቊ tt X n + W n H 0 h tt X n + h it Z n + W n H 1 Z n 8

9 Problem formulation X n Data Y n h tt h it Collision h Y n = ቊ tt X n + W n H 0 h tt X n + h it Z n + W n H 1 Z n Challenge: Detect weak interferers in the presence of stronger self-interference 9

10 Motivation: Energy and Throughput Gains Wasted Energy Half duplex Tx Interferer Collision detecting Tx Interferer Time Time 10

11 Motivation: Energy and Throughput Gains Wasted Energy Half duplex Tx Interferer Collision detecting Tx Interferer Time Time 11

12 Feasibility: Sensitivity Requirement d ir Tx d tr Rx 12

13 Feasibility: Sensitivity Requirement d ir d it Tx d tr Rx 13

14 Feasibility: Sensitivity Requirement d ir d it Tx d tr Rx Detection at both Rx and Tx 14

15 Feasibility: Sensitivity Requirement Misdetection d ir d it Tx d tr Rx Detection at both Rx and Tx 15

16 Feasibility: Sensitivity Requirement False detection at Tx Misdetection d ir d it Tx d tr Rx Detection at both Rx and Tx 16

17 Feasibility: Sensitivity Requirement Constraint 5% False detection at Tx Misdetection d ir d it Tx d tr Rx Detection at both Rx and Tx Target > 95% 17

18 Feasibility: Sensitivity Requirement Constraint 5% False detection at Tx Misdetection d ir d it Tx d tr Rx Detection at both Rx and Tx Target > 95% βδ Detection sensitivity w.r.t self interference power 18

19 Feasibility: Sensitivity Requirement Constraint 5% False detection at Tx Misdetection d it Tx d tr Collision d ir detection at Tx is feasible and useful for indoor environments Rx Detection at both Rx and Tx Target > 95% βδ Detection sensitivity w.r.t self interference power 19

20 Evaluated Detection Techniques h Y n = ቊ tt X n + W n H 0 h tt X n + h it Z n + W n H 1 Energy detection test statistic: Two-sample Goodness-of-Fit Test Statistics: Learnt through training Kolmogorov-Smirnov: Kuiper: Anderson-Darling: ˆD KS = max{ d +,d - } ˆD KP = d + + d - Estimated from Y n 2-norm difference between combined CDF and z 1 Weight = i(n i) Weights tails 20

21 Our measurement setup Node with collision detection: Interfering node: RX USRP RX RF Kintex7 FFT USRP N210 Tx ATT Z ANT EB duplexer (RF SIC) Z BAL Spartan3 PAR 2 SER Micro Blaze USRP X310 IEEE signals TX power: 0dBm Noise floor: -90dBm EBD cancellation: 50-70dB TX Receiver oversamples by 8 Results averaged over 2000 measurements per interfering power Threshold trained for each test statistic such that P FA = 5% TX RF CW 21

22 Results Target: P D > 95%, P FA < 5% 22

23 Results Target: P D > 95%, P FA < 5% 2000 samples = 250 μs, i.e., 4 bytes in an 8 times oversampling receiver 23

24 Results Target: P D > 95%, P FA < 5% Observation duration: 250 μs 24

25 Conclusions Collision detection at TX is practical for indoor environments Kuiper test + analog SI cancellation can detect interferers up to -75 dbm Almost instantaneous: only 250 μs 0 dbm -50 dbm -75 dbm -90 dbm Tx power Remaining SI Minimum interferer Noise power 25

26 Thank you! 26

27 References B. van Liempd et al., A +70-dBm IIP3 Electrical-Balance Duplexer for Highly Integrated Tunable Front-Ends, IEEE Transactions on Microwave Theory and Techniques, vol. 64, no. 12, pp , Dec T. Vermeulen, B. van Liempd, B. Hershberg, and S. Pollin, Real-time RF self-interference cancellation for in-band full duplex, in 2015 IEEE International Symposium on Dynamic Spectrum Access Networks (DySPAN), 2015, pp