ZigFi: Harnessing Channel State Information for Cross-Technology - - PowerPoint PPT Presentation
ZigFi: Harnessing Channel State Information for Cross-Technology Communication Xiuzhen Guo 1 , Yuan He 1 , Xiaolong Zheng 1 , Liangcheng Yu 2 , Omprakash Gnawali 3 1 Tsinghua University 2 KTH Royal Institute of Technology 3 University of Houston
Xiuzhen Guo1, Yuan He1, Xiaolong Zheng1, Liangcheng Yu2, Omprakash Gnawali3
1Tsinghua University 2KTH Royal Institute of Technology 3University of Houston
1
1.
Smart Hospital Smart Factory Smart Home
2
1.
WEBee BlueBee FreeBee Esense GapSense B2W2 HoWiEs WiZig FreeBee FreeBee
3
1.
Packet Energy: WiZig [Infocom’17]
WiFi ZigBee T CTC symbol window 1 1 1
WiFi packet
1 CTC symbol 1 0 CTC symbol 0
Time Time
T
CTC symbol window 1 1 1 1 1
Time Time
WiFi ZigBee
Packet Size: Esense [MobiCom ’09], HoWiEs [Infocom ’13]
100 Bytes 200 Bytes 100 Bytes WiFi Time ZigBee
E
010
Time Time RSSI value WiFi Packet CTC messsage
4
1.
Packet Transmission Timing: FreeBee [MobiCom ’15], Gap Sense [Infocom ’13]
t (reference position) Modulation via shifting ( / 2 ) t T 2 t t t 2 t / 2 t T Time
Physical Signal Emulation: WEBee [MobiCom ’17], BlueBee [SenSys ’17]
Ignore Ignore Demodulation WiFi ZigBee Emulated ZigBee Signals WiFi Packet ZigBee Packet
5
1.
Using RSSI is inefficient T x：0dBm T x：20dBm Bandwidth: 20M Rate: 54Mbps Bandwidth: 2M Rate: 250Kbps Physical emulation is infeasible Modulation: OQPSK, DSSS Modulation: QAM, OFDM Directly decoding is difficult
6
1.
2462
WiFi
... ...
f (MHz)
... ... ... ... ... ...
ZigBee
2465
f (MHz)
#11 #21 #22 #23 #24
WiFi channel ZigBee channel DC Subcarrier (1) Pilot Subcarrier (4) Data Subcarrier (48) Null Subcarrier (11) (Without ZigBee) (With ZigBee)
The transmission of ZigBee packets affects the CSI significantly
7
1.
#Subchannel #Packet Length # Transmission Power
Select a proper subchannel
ZigBee length satisfies a threshold
Choose an appropriate ZigBee power
8
1.
WiFi
Packets Modulation Encoding Message
ZigBee
CSI Sequence Demodulation SVM Decoding Decoding WiFi Packets Message Existing WiFi Link
PHY Layer PHY Layer ZigFi
ZigBee packets piggy-backed to the existing WiFi link WiFi receiver collects two sets of information SVM classification
9
1.
TDZ TIZ
ZigBee TX WiFi TX WiFi RX Preamble ZigBee packet WiFi packet CSI sample not interfered by ZigBee CSI sample interfered by ZigBee
Encoding: Presence or absence of ZigBee packets Decoding: SVM identifies the interfered CSI sequence
10
1.
𝑇𝐽𝑂𝑆 = 10𝑚 𝑇𝑎 𝐽𝑋 + 𝑂 SINR in range [-0.25,1.25], decoding accuracy > 0.9
11 1
1.
Establish a WiFi link Obtain an appropriate SINR
12 2
1.
WiFi Sender WiFi Receiver Noise
d1 d4
ZigBee Sender
d5 d3 d2
WiFi RX WiFi TX ZigBee TX USRP
WiFi: Commercial WiFi device + CSITool, channel 11 ZigBee: TelosB mote, channel 23 Noise: USRP generator Metrics: Throughput and SER
13 3
1.
ZigFi shows significant enhancement over FreeBee in terms of throughput and SER.
14 4
1.
The ZigBee Tx and the WiFi Rx
Adaptive is better than default. ZigFi performs well under the adaptive mode.
15 5
1.
WiFi Tx and the WiFi Rx
Adaptive is better than default. ZigFi in the adaptive mode performs well.
16 6
1.
Throughput of ZigFi degrades with noise intensity increases. ZigFi in the adaptive mode is more resilient to noise.
17 7
1.
ZigFi in the adaptive mode is robust under NLoS scenario
18 8
1.
ZigFi has limited impact on the WiFi communication
(Without ZigFi) (With ZigFi)
19 9
1.
We harness CSI as a side channel to achieve CTC from ZigBee to WiFi and translate the decoding problem into a CSI classification problem. We design a receiver-initiated protocol for practical application of ZigFi. Experimental results show that ZigFi achieves efficient and robust CTC.
20
guoxz16@mails.Tsinghua.edu.cn
21