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OFDMA Backscatter: Boosted Capacity Low Power IoT System
▪ Renjie Zhao ▪ 2017年6月
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Internet of Things(IoT)
OFDMA Backscatter: Boosted Capacity Low Power IoT System Renjie - - PowerPoint PPT Presentation
OFDMA Backscatter: Boosted Capacity Low Power IoT System Renjie - - PowerPoint PPT Presentation
OFDMA Backscatter: Boosted Capacity Low Power IoT System Renjie Zhao 2017 6 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
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Wi-Fi Alliance: surpass 15 billion by end of 2016
More re Wi Wi-Fi Dev i Devic ices
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Wi-Fi is power hungry
2 or 3 hours
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Why is Wi-Fi Power Consuming?
Digital (Baseband) Analog (RF) Power scaled with Moore’s law O(10 uW) No such scaling O(100 mW)
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Passive Wi-Fi
Idea: Use only digital baseband
Single Plugged-in Device Passive Device
NSDI '16 Passive Wi-Fi: Bringing Low Power to Wi-Fi Transmissions
Commodity receiver
Singl ingle t tone ne sign ignal Backs ckscat catter sign ignal Singl ingle t tone ne sign ignal
Power Frequency
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802.11b
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OFDM IS POPULAR SCHEME
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OFDM SPECTRUM
subcarrier
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g g
802.11g PHYSICAL PARAMETTERS
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tag1 tag2 tag48
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··· ···
tag1 tag2 tag48 OR
Singl ingle t tone ne sign ignal Backs ckscat catter sign ignal
OFDM symbol
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OR
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··· ···
tag1 tag2 tag48 OR
Singl ingle t tone ne sign ignal Backs ckscat catter sign ignal
OFDM symbol
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preamble header + MAC header downlink data MSDU PSDU MPDU = PPDU ( ) pseudo data sending clear wave tail and pad bits
Set up link For backscatter
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··· ···
tag1 tag2 tag48 OR
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··· ···
tag1 tag2 tag48 OR
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··· ···
tag1 tag2 tag48 OR
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Page. e.24 24 T-R coordination Subcarrier allocation Carrier generate Synchronization Frequency shifting Synchronization T-R coordination Modulation Data acquisition Transmitter IoT Device Receiver
…
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MORE CAPACITY
▪ OFDMA system ▪ CSMA/CA
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CSMA/CA
▪ Packet mode method of multiple access method using in Wi-Fi. ▪ Coexistence with other ISM devices. ▪ Medium sensing is power hungry transmitter
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MORE CAPACITY
▪ OFDMA system ▪ CSMA/CA ▪ Cognitive radio
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Cognitive radio
Flash and antifuse technologies low power PLL
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Cognitive radio
▪ Flexible clock PLL ▪ Also sensing medium (allocation) transmitter
Flash and antifuse technologies low power PLL 5uW
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EVALUATION
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EVALUATION
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FUTURE WORK
▪ Joint debugging communication performance ▪ IC design power consumption ▪ REAL OFDM backscatter
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OUR CONTRIBUTION
▪ 1.Introduce the first OFDMA backscatter system. ▪ 2.Conbine several techniques for low frequency band
- ccupation.
▪ 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.
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COMPARISON
System
Passive Wi-Fi[1] FS- Backscatter[2] HitchHike[3] Inter- Backscatter[4] Our system
Throughput (Kbps) 1000/11000 50 200/300 2000 100/250 Range (m) 30 3.6 54/34 27 20 Power consumption (μW) 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.
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Q&A
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