RCTC: Rapid Concurrent Transmission Coordination in Full Duplex Wireless Networks Wenjie Zhou,...
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Transcript of RCTC: Rapid Concurrent Transmission Coordination in Full Duplex Wireless Networks Wenjie Zhou,...
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RCTC: Rapid Concurrent Transmission
Coordination in Full Duplex Wireless Networks
Wenjie Zhou, Kannan Srinivasan, Prasun SinhaDepartment of Computer Science and Engineering
The Ohio State University{zhouwe, kannan, prasun}@cse.ohio-state.edu
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Full Duplex“Hi Alice”“Hi Bob”
Half Duplex“Hi Alice”“Hi Bob”
Two Transmission slots One Transmission slot
Full duplex doubles the throughput between two nodes
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• Full duplex doubles the throughput• When both Alice and Bob have packets
• However, traffic tends to be asymmetric
Traffic Pattern and Full Duplex
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Traffic Asymmetry and Full Duplex
I’m listening“Hi Bob”
Busytone packet (fake packet) [MobiCom’11] A waste of channel resources
How to use full duplex beyond 2 nodes?
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Other opportunities exist…
Bob
EllieAlice
CharlieFloyd
Secondary transmission
Introduced in ContraFlow [WiOpt’11]
Gauss
Enabling exposed and secondary transmission achieves 3X throughput
More exposed transmissions enabled, even higher throughput
Primary transmissionExposed transmission
Hellen
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Transmission Modes
• Bi-directional Transmission Mode
• Unidirectional Mode
• Secondary Transmission Mode
BobAlice Charlie
BobAlice
BobAliceEllieFloyd
EllieFloyd
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Challenges in MAC Design
1. Rapid coordination among neighbors – Time efficient
2. Identify exposed transmission opportunities– Primary receiver should not be affected
3. Reliable reception at potential receivers– Exposed receivers and secondary receivers should experience little
interference– Avoid exposed transmission collision
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RCTC Design
1. Rapid Coordination
2. Exposed terminal identification3. History based receiver selection
4. Exposed terminal suppressing
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Node Signature• Property of node signature:
– Unique for every node– High self correlation value– Low cross correlation value
• Signature in previous work:– CSMA/CN [MobiCom’10]– E-MILI [MobiCom’11]– 802.11ec [MobiCom’12]
• Gold code:– Length: 127 bits– Number of signatures: 129– Duration: 6.5 μs (BPSK, 20MHz bandwidth)
Self correlation results
Cross correlation results
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Bi-directional Transmission Mode
Alice:
Bob:
SB SA
SA
Packet for Bob
Packet for Alice
Alice’s signatureBob’s signature
Bob
Alice
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Unidirectional Mode
Alice:
Bob:
SB SA
SH
Packet for Bob
Busytone for hidden terminal
Ellie: Packet Floyd
Half duplex signature
Bob
AliceEllie
Floyd
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Secondary Transmission Mode
Alice:
Bob:
SB SA
SH
Packet for Bob
Packet for Charlie
Bob
Alice
Charlie
Ellie
Floyd
Ellie: Packet Floyd
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RCTC Design
1. Rapid Coordination
2. Exposed terminal identification3. History based receiver selection
4. Exposed terminal suppressing
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Bob
EllieAlice
Floyd
Exposed Terminal Identification
Time
Sign
al S
tren
gth
(dB)
Received signal from Alice
SIR for data rate dAB
Received signal from Ellie
Time
Sign
al S
tren
gth
(dB)
Received signal from Ellie
SIR for data rate dEF
Received signal from Alice
Conflict constraints for exposed terminal
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TX power:
SB SA
Exposed Terminal Constraint at Bob
SB SA
Bob
Alice
Ellie
SH
Rx Power:
Rx Power:
TX power: SH
Can we obtain on the fly?
Constraint at Bob:
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TX power:
SB SA
Signal Strength Reflection
SB SA
Bob
Alice
Ellie
SH
Rx Power:
SHTX power:
Rx Power:
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RCTC Design
1. Rapid Coordination
2. Exposed terminal identification3. History based receiver selection
4. Exposed terminal suppressing
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Ellie
History Based Receiver Selection
• Set p to 1 upon a successful transmission• Halve p upon a failed transmission
SB SA
Bob
AliceExMap: {TX, RX, p}
Primary Tx Exposed Rx pAlice Matt 0.25Alice Floyd 1Alice Neil 0.125Alice Leonard 0Bob Alice 0.125
… … …
1
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RCTC Design
1. Rapid Coordination
2. Exposed terminal identification3. History based receiver selection
4. Exposed terminal suppressing
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Exposed Terminal Suppressing
Transmit!
Unidirectional Mode Bi-directional Mode
𝑃 ′𝐵𝐸≤0?
𝑃 𝐵𝐸≤0?
How to distinguish?
BobAlice
Ellie
SA
BobAlice
Ellie
SH
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Exposed Terminal Suppressing
Bob
Alice
Ellie
Bi-directional Mode
SB SASF
{RX, plost} in certain period
{Bob, 0.5} > ∆
Send SF
Full duplex signature
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Experiments
• USRP testbed– 5 USRPs
• Other schemes:– FDNative[MobiCom’11]: full duplex without exposed and
secondary transmission– CF [WiOpt’11]: full duplex with secondary transmission
enabled
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USRP Testbed
~59%
~78%
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Simulations
• Simulation Setup: – Randomly picked links in AP and Ad hoc network– Varied number of flows, APs, and clients– 200 runs each setup
• Other schemes:– FDNative: full duplex without exposed and secondary
transmission– CF: full duplex secondary transmission enabled– CMAP[NSDI’08]: exposed transmission enabled half duplex– Half-duplex: IEEE 802.11
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Throughput Breakdown
• Significant exposed transmission opportunities• Limited secondary transmission opportunities
30 APs 50 APs
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AP Network2.31X compared with FDNative Comparable fairness
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Ad hoc network54% gain over FDNative
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Summary and future work
Summary:• Fast and low overhead signaling mechanism using node
signatures• Signal strength reflection to identify exposed terminals • Throughput gain as high as 2.31X without losing fairness
Future work:• Multiple datarates• Transmission priority
THANK YOU
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THE ENDTHANK YOU
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Backup Slides
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Multiple Datarates
BobEllieSH
TX power:
Rx Power: TX power:
Rx Power:
, Let
𝑃❑′𝐵𝐸❑ =
𝑃 𝐵𝐸
𝑃 𝐴𝐵
𝐶𝑑
𝑃 𝐴𝑙𝑖𝑐𝑒
<𝐶 ,C is a known constant
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Different gain for AP and ad hoc network
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Different gain for AP and ad hoc network
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Throughput Breakdown
Average exposed throughput of 200 runs: - 30 APs : 31% - 40 APs : 39% - 50 APs : 46% (Compared with FDNative)Secondary transmission is not promising in AP network
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AP network (different flows)
35% to 111% higher throughput
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AP network (different parameter)
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AP network (download ratio)
71.2% to 90.9% higher throughput
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Ad hoc network
more opportunities for secondary txAverage gain over FDNative changes:
• (a) from 9% to 54%;• (b) from 1% to 29%.
39
Node 1->Node 2 : primary transmissionPij : the received signal strength from node i to node jΔd : a predefine threshold related with data rate
Node 2
Node 4Node 1
Node 5P45/P15 > Δd, AND P12/P42> Δd
Exposed Node Identification
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Signal Strength Reflection
TX:
RX:
SRX STX
SH
EX:
𝑃𝑇𝑅=𝑃0∨h𝑇𝑅¿2
𝑃 𝑅𝑋=𝐶𝑑
𝑃𝑇𝑅
=𝐶𝑑
𝑃0∨h𝑇𝑅¿2
𝑃 𝑅𝐸=𝑃𝑅𝑋∨h𝑅𝐸 ¿2=𝐶𝑑∨h𝑅𝐸 ¿2
𝑃0∨h𝑇𝑅¿2
𝑃𝑇𝑅
𝑃𝐸𝑅
=𝑃0∨h𝑇𝑅 ¿2
𝑃0∨h𝐸𝑅¿2=
¿h𝑇𝑅 ¿2
¿ h𝐸𝑅¿2>∆𝑑
𝑃 𝑅𝐸=𝐶𝑑∨h𝑅𝐸¿2
𝑃0∨h𝑇𝑅¿2 <
𝐶𝑑
𝑃0
∆𝑑=𝐶 ,𝑖𝑓 { 𝐶𝑑=𝐶𝑃0∆𝑑
¿ h𝐸𝑅¿2=¿h𝑅𝐸¿2
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History Based Receiver Selection
• Set p to 1 upon a successful transmission.• Halve p upon a failed transmission
TX:
RX:
SRX STX
SH
EX:
ExMap: {TX, RX, p}
TX
RX1, 0.25
RX2, 1
RX3, 0.125
RX4, 0
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Exposed Terminal Suppressing
TX:
RX:
SRX STX
SH
EX:
𝑃 𝑅𝐸=𝐶𝑑∨h𝑅𝐸¿2
𝑃0∨h𝑇𝑅¿2 <
𝐶𝑑
𝑃0
∆𝑑=𝐶
𝑃 𝑅𝐸=0? Transmit!
TX:
RX:
SRX STX
STX
Collision at TX!!!
TX:
RX:
SRX STX
STX
Suppressing exposed transmission
SF
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Related Work
• Full duplex system:– Choi et al. [MobiCom’10], three antennas– Duarte et al. [ASILOMAR’10], two antennas– Jain et al. [MobiCom’11], two antennas– Aryafar et al. [MobiCom’12], full duplex MIMO– Bharadia et al. [SIGCOMM’13], one antenna
• Full duplex MAC:– Singh et al. [WiOpt’11], fairness, secondary transmission– Jain et al. [MobiCom’11], busytone padding– Sahai et al. [Technical Report’11], full duplex triggering
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Three Antenna Design(with 2 RF chains and some additional h/w)
“Achieving Single Channel, Full Duplex Wireless Communication”, MobiCom’10
~ 30 dB
~ 25 dB
~ 15 dB
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Two Antenna Design(with ~ 3 RF chains)
“Full-Duplex Wireless Communications Using Off-The-Shelf Radios: Feasibility and First Results”, ASILOMAR’10
Antenna separation (AS)
Analog cancellation (AC)Digital cancellation (DC)
c1 = - (hab/hz)x1
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Two Antenna Design(with 2 RF chains and some additional h/w)
“Practical, real-time, full duplex wireless”, MobiCom’11
~ 30 dB
~ 43 dB
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Two Antenna Design(with 2 RF chains and some additional h/w)
“Rethinking Indoor Wireless: Low Power, Low Frequency, Full-duplex”, Microsoft Research’09
- Self-interference at the receive antenna was 55 dB - Analog Interference Cancellation (30 dB) - Nulling Antenna (25 dB)
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Two Antenna Design for MIMO-FD(with 2 RF chains and phase shifter)
“MIDU: Enabling MIMO Full Duplex”, MobiCom’12
Receive Cancellation
Transmit Cancellation
20 dB - 30 dB 22 dB - 30 dB
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Two Antenna Design for MIMO-FD (contd.)(with 2 RF chains and phase shifter)
“MIDU: Enabling MIMO Full Duplex”, MobiCom’12
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Feasibility of One Antenna Design(with 2 RF chains and addl. h/w)
“Picasso: Flexible RF and Spectrum Slicing”, SIGCOMM’12
Not a real full duplex system (TX, RX on different spectrum)
13 dB - 20 dB 30 dB
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Prior Art: MAC Layer for FD (1 of 3)“Practical, real-time, full duplex wireless”, MobiCom’11
No exposed or secondary transmission
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Prior Art: MAC Layer for FD (2 of 3)“Pushing the limits of Full-duplex: Design and Real-timeImplementation”, Technical Report’11(Constraint: A node cannot start new transmission while receiving)
AP->M1, M1->AP
AP->M1, M2->AP
No exposed transmissions
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Prior Art: MAC Layer for FD (3 of 3)“Efficient and Fair MAC for Wireless Networks with Self-interference Cancellation”, WiOpt’11
No exposed transmissions; Simulations only
54
RCTC Design
1. Rapid Coordination
2. Exposed terminal identification3. History based receiver selection
4. Exposed terminal suppressing