OFDMA Backscatter: Boosted Capacity Low Power IoT System Renjie - PowerPoint PPT Presentation

OFDMA Backscatter: Boosted Capacity Low Power IoT System ▪ Renjie Zhao ▪ 2017 年 6 月

Internet of Things(IoT) Page. e.2

Page. Page. e.3 e.3

Wi-Fi Alliance: surpass 15 billion by end of 2016 More re Wi Wi-Fi Dev i Devic ices Page. e.4

Wi-Fi is power hungry 2 or 3 hours Page. e.5

Why is Wi-Fi Power Consuming? Power scaled No such scaling with Moore’s law O(100 mW) O(10 uW) Analog Digital (RF) (Baseband) Page. e.6

Passive Wi-Fi Idea: Use only digital baseband Singl ingle t tone ne Backs ckscat catter sign ignal Single sign ignal Plugged-in Passive Commodity Device Device receiver Singl ingle t tone ne sign ignal Power Frequency Page. e.7 NSDI '16 Passive Wi-Fi: Bringing Low Power to Wi-Fi Transmissions

802.11b Page. e.8

OFDM IS POPULAR SCHEME Page. e.9

OFDM SPECTRUM subcarrier Page. e.10 10

802.11g PHYSICAL PARAMETTERS g g Page. e.11 11

tag1 tag2 tag48 Page. e.12 12

OFDM symbol tag1 Backs ckscat catter sign ignal tag2 Singl ingle t tone ne sign ignal ··· ··· tag48 OR Page. e.13 13

OR Page. e.14 14

OFDM symbol tag1 Backs ckscat catter sign ignal tag2 Singl ingle t tone ne sign ignal ··· ··· tag48 OR Page. e.15 15

MSDU + tail and pad bits preamble header MAC header downlink data pseudo data sending clear wave ( ) = PSDU MPDU PPDU Set up link For backscatter Page. e.16 16

tag1 tag2 ··· ··· tag48 OR Page. e.17 17

tag1 tag2 ··· ··· tag48 OR Page. e.18 18

tag1 tag2 ··· ··· tag48 OR Page. e.19 19

Transmitter IoT Device Receiver T-R coordination T-R coordination Subcarrier Frequency allocation shifting Carrier generate Synchronization Synchronization Modulation Data acquisition Page. e.24 24 …

MORE CAPACITY ▪ OFDMA system ▪ CSMA/CA Page. e.25 25

CSMA/CA ▪ Packet mode method of multiple access method using in Wi-Fi. ▪ Coexistence with other ISM devices. ▪ Medium sensing is power hungry  transmitter Page. e.26 26

MORE CAPACITY ▪ OFDMA system ▪ CSMA/CA ▪ Cognitive radio Page. e.27 27

Cognitive radio Flash and antifuse technologies low power PLL Page. e.28 28

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Cognitive radio ▪ Flexible clock  PLL ▪ Also sensing medium (allocation)  transmitter Flash and antifuse technologies low power PLL 5uW Page. e.30 30

EVALUATION Page. e.31 31

EVALUATION Page. e.32 32

FUTURE WORK ▪ Joint debugging  communication performance ▪ IC design  power consumption ▪ REAL OFDM backscatter Page. e.33 33

OUR CONTRIBUTION ▪ 1.Introduce the first OFDMA backscatter system. ▪ 2.Conbine several techniques for low frequency band occupation. ▪ Frequency shifting backscatter; single side band; bi-directional communication. ▪ 3.Design a network stack frame to implement. ▪ Cognitive radio; CSMA/CA. ▪ 4.Build a prototype based on commodity devices. Page. e.34 34

COMPARISON FS- Inter- System Backscatter[4] Our system Passive Wi-Fi[1] Backscatter[2] HitchHike[3] Throughput (Kbps) 1000/11000 50 200/300 2000 100/250 Range (m) 30 3.6 54/34 27 20 Power consumption ( μ W) 14.5/59.2 45 33 28 ～ 30 Capacity (/channel) 1 1 1 1 48 Band occupation 1+1* 2 2 1+1* 1 Mirror signal Y Y N N N Commodity device N Y Y Y Y *1+1 means besides the channel frequency band occupied by the data signal the system also occupies another frequency band for the original signal. Page. e.35 35

Q&A

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