mZig: Enabling Multi-Packet Reception in ZigBee

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mZig Enabling Multi-Packet Reception in ZigBee
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Table of Contents
Motivation
Preliminary
Design
Implementation
Performance Evaluation
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Table of Contents
Motivation
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ZigBee Communication
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• Standard IEEE 802.15.4
• Focus low-power, low-cost, low-bitrate
• Applications Sensor networks Smart homes
  Internet of things Industrial control ......

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Concurrent Transmissions in ZigBee
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Cluster topology

• Tree topology

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Collision Problem
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Related Work
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Collision Avoidance Collision Avoidance
CSMA/CAJSAC'04,ToN'08 RTS-CTSAHNet'03
hidden terminal delay
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Collision Resolution Collision Resolution Collision Resolution
Analog NCSigComm'07, XORsSigComm'06, Full DuplexMobiCom'11 Constructive Interference IPSN'11, NDSI'13, TPDS'15 ZigZagSigComm'08
partial known info synchronized same content retransmission required
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Our Goal
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• No pre-known info
• No retransmission requirement
• Multiple TXs are allowed to send different
  packets

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Decompose multiple packets from one collision
directly!
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Table of Contents
Preliminary
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ZigBee Specification
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Frequency Coverage Data Rate of Channels Rx Sensitibity Modulation
2.4GHz World 250kbps 16 -85dBm O-QPSK
868MHz Europe 20kbps 1 -92dBm BPSK
915MHz USA 40kbps 10 -92dBm BPSK
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PHY in ZigBee
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Baseband Signal at TX side
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Features of Chips at RX side
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• Oversampling sampling rate of recent ADCs is
  much higher than 2MHz.
• Known shaping half-sine.
• Uniform amplitude O-QPSK, no ASK or QAM.

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How to use these features to resolve
multi-packet collisions?
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Table of Contents
Design
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Core Design of mZig
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• Example a two-packet collision.
• Alice 11000 Bob 10100.
• Every chip has 5 samples.

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Two Categories of Collisions
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• without chip-level time offset (w/o CTO)

• with chip-level time offset (w/ CTO)

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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Step I Extract collision-free samples
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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Step II Estimate samples to form a whole chip
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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Substract the estimated chip from the collision
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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Repeat the extraction and estimation steps
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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Repeat the extraction and estimation steps
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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Repeat the extraction and estimation steps
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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Repeat the extraction and estimation steps
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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Repeat the extraction and estimation steps
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CrossIC
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• Cross Interference Cancellation (CrossIC) for
  collision w/ CTO.

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Repeat the extraction and estimation steps
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AmpCoD
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• Amplitude Combination based Decomposition
  (AmpCoD) for collision w/o CTO.

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AmpCoD
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• Amplitude Combination based Decomposition
  (AmpCoD) for collision w/o CTO.

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Assume agtß Assume agtß
L1 aß
L2 a-ß
L3 -aß
L4 -a-ß
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1
Core Design Core Design
CrossIC AmpCoD
Design Enhancement Design Enhancement
Time Offset Detection Anti-Noise
Multipath Filter Frequency Offset Compensation
Scope Scope
m-Packet Collision (mgt2) Bluetooth WiFi
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Table of Contents
Implementation
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RX PHY ZigBee v.s. mZig
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DmZig Module
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Testbed
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• RX USRP X310 PC
• TX USRP B2106 Laptop6 iRobots6

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Table of Contents
Performance Evaluation
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Experiment Setting
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Configuration
Sampling rate 32Msps
TX power 0dB
Channel selection 26
Metrics
Bit Error Rate (BER)
Throughput
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Compared with
ZigBee
ZigZag
Field
7.5m6.8m office
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BER Different Sampling Rates
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BER Different Techniques
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Throughput Different Techniques
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Throughput Different Techniques
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Throughput Different Techniques
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Throughput Static v.s. Mobile
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Conclusion
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• We design mZig, a novel RX design to enable
  multi-packet reception in ZigBee. Theoritcally,
  the maximal concurrent transmissions is mS/2C.
• We implement mZig on USRPs. In our testbed, the
  throughput of mZig achieves 4.5x of ZigBee with
  four or more TXs.

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Q A
linghe.kong_at_mail.mcgill.ca
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Backup
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Time Offset Detection
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Anti-Noise Design

• For CrossIC
• For AmpCoD

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Multipath Filter

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

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Frequency Offset Compensation

• Channel estimation is also required to estimate
  the frequency offset.
• Compensate the frequency offset chip-by-chip.

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Scope
m-Packet Collision in ZigBee
Bluetooth
WiFi
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MAC for mZig

• The conventional MAC for ZigBee cannot be applied
  directly
• CSMA/CA
• ACK

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Simulation

• Impact of CTO

Impact of SNR
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Simulation (cont)

• Multipath Filter

Freq. Compensation