Download - May 29, 2009
International Technology AllianceIn Network & Information Sciences
International Technology AllianceIn Network & Information Sciences
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Cooperative Wireless Networks:From Radio to Network Protocol Designs
May 29, 2009
by Zhengguo ShengSupervisor: Prof. Kin K. Leung
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Outline
IntroductionIntroduction
Current Research
Conclusion
Introduction
• Cooperative diversity is a cooperative multiple antenna techniques which exploits user diversity by decoding the combined signal of the relayed signal and the direct signal in wireless multi-hop networks.
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motivation for cooperative diversity
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• Motivation for ad-hoc networks with cooperative transmission– Wireless links are unreliable due to multi-path propagation– Spatial diversity is bandwidth efficient to combat fading– Spatial diversity is difficult to achieve due to processing
complexity, power consumption, ...• Solution: Cooperative Transmission
– Allow users to share their antennas cooperatively to assist each other for successful reception
• Advantages of cooperative transmission: Virtual antenna array– Boosted reception reliability– Achieved higher data rates– Bandwidth efficient and increased coverage
A simple example of cooperative transmission
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Normalized TX power with or without cooperative transmission (CT). The data
rate is set as R = 0.1 bit/s/Hz, and the prefixed required outage probability is
P=10%. Two sources are located at (−5, 0) and (−5, 0).
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Outline
Introduction
Current ResearchCurrent Research Quality-of-Service Routing Algorithm for Wireless Quality-of-Service Routing Algorithm for Wireless
Cooperative NetworksCooperative Networks
Distributed and Power Efficient Routing in Wireless Cooperative Networks
Interference Subtraction with Supplementary Cooperation in Wireless Cooperative Networks
Conclusion
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QoS Routing Algorithm
• Algorithm description– Select the best relay and establish a one-hop cooperative route
from source to destination and compare its ETE (End-to-end) BER with the target BER
– If this BER is larger than target BER, identify the link with the highest BER along the route and improve its BER performance by selecting a new relay
– Repeat second stage, until the ETE BER is no larger than target BER, then the cooperative route is finalized
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Source
Destination
A Simple Network Scenario
[1] Z. Sheng, Z. Ding and K. K. Leung, "On the Design of a Quality-of-Service Driven Routing Protocol for Wireless Cooperative Networks", proc. of IEEE Vehicular Technology Conference (VTC), Singapore, MAY 2008.
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Routing Comparison between Proposed Algorithm and DV Algorithm
• Compared with 9 hops and 10% ETE BER of Distance-Vector (DV) algorithm, our proposed algorithm (5 hops and 3% end-to-end BER) shows better performance
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X (meters)
Y (
met
ers)
DV route Direct tranmissionRelay transmission
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BER Performance Comparison with DV Algorithm
• Under same number of hops, proposed routing algorithm can achieve much better error performance than DV algorithm as well as the scheme without relay transmission
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10-2
10-1
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Number of nodes in the network
End
-to-
end
BE
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Proposed algorithm without relay linksDV algorithmProposed algorithm
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10-1
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Number of hops in a route (considered by the algorithm)
End
-to-
end
BE
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Proposed algorithm without relay linksDV algorithm with 9 hopsProposed algorithm
• As the number of hops increases in the route, the ETE BER of proposed algorithm is reduced correspondingly
ROUTING PERFORMANCE EVALUATION
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10-2
10-1
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Total number of hops
End
-to-
end
BE
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Proposed routing algorithmDV algorithmUpper bound performance of proposed algorithm (Inf. nodes)Upper bound performance of optimal solution (Inf. nodes)
Theorem1: For infinitely dense network where node exists at any location, the upper bound BER for the proposed routing with N hops is proportional to , where A, being perfect power of 2, is the largest integer that smaller than the total number of hops N and k is the pass loss exponent.
The cooperative links of the optimal routing are uniformly distributed along the line between the source and the destination node
The performance of the proposed algorithm closes to optimal.
[2] Z. Sheng, Z. Ding, K. K. Leung, D. L. Goeckel and D. Towsley, "Error Performance Bound for Routing Algorithms in Wireless Cooperative Networks", proc. of The Second Annual Conference of The International Technology Alliance (ACITA 2008), UK.
(2k-1)1/ A
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Outline
Introduction
Current ResearchCurrent Research Quality-of-Service Routing Algorithm for Wireless
Cooperative Networks
Distributed and Power Efficient Routing in Wireless Distributed and Power Efficient Routing in Wireless Cooperative NetworksCooperative Networks
Interference Subtraction with Supplementary Cooperation in Wireless Cooperative Networks
Conclusion
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Transmission Power Optimization of Cooperative Link
• Observations– Both source and relay are assumed so far to transmit at the same
Tx power
– One can further reduce total Tx power to achieve a given target
BER
Source Destination
Relay
Cooperative Link
Question?Can we do better to minimize Ps+Pr ?
[3] Z. Sheng, Z. Ding and K.K. Leung, "Distributed and Power Efficient Routing in Wireless Cooperative Networks", Proc. of IEEE International Conference on Communications, ICC 2009.
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Transmission Power Optimization
• Tx Power Optimization with a target ETE BER
(Outage probability
• Using the Kuhn-Tucker condition, the minimum Tx power can be shown as
where
where R=data rate, =noise spectral density and B=bandwidth)
Simulation Result Power Reduction for CL
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source destination
50 Relay candidates
Network Topology
• Relay randomly placed in the 100m *100m square• Average power reduction for all relay nodes is 82.73% and 21.22%, compared with two-hop transmission and MPCR, respectively
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Tot
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x po
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ized
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nois
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(dB
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MPSDFMPCRDirect Transmission
Routing Performance Evaluation
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the
pat
h (d
B)
CASNCP proposed algorithm DSDVCentralized algorithm
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Total transmission power normalized to noise power along the path (dB)
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-to-
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Proposed algorithm Centralized algorithm
2 hops
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2 hops
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4 hops4 hops
3 hops 3 hops
The total power consumption of our proposed routing algorithm can reduce by a couple dB compared to the existing cooperative routing algorithms.
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Outline
Introduction
Current ResearchCurrent Research Quality-of-Service Routing Algorithm for Wireless
Cooperative Networks
Distributed and Power Efficient Routing in Wireless Cooperative Networks
Interference Subtraction with Supplementary Interference Subtraction with Supplementary Cooperation in Wireless Cooperative NetworksCooperation in Wireless Cooperative Networks
Conclusion
Motivation for Supplementary Cooperation
• Observations– Broadcast nature of wireless transmission can be
further explored – Cooperation can be extended across the CLs
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S1
S2 S3 S4
R1 R2R3
Cooperation? Yes
T2T1 T3 T4 T5 T6
[4] Z. Sheng, Z. Ding and K. Leung, “Interference Subtraction with Supplementary Cooperation in Wireless Cooperative Networks”, Proc. of IEEE International Conference on Communications, ICC 2009.
Outage Probability of Supplementary Cooperation
• Channel Capacity:
• Outage Probability:
• By computing the limit, we have
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BER Improvement with Supplementary Cooperation
• SC generates routes with a smaller number of hops and satisfactory BER when compared with CC
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Total number of hops
End
-to-
end
BE
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Conventional cooperationDirect transmissionSupplementary cooperation
34.87%
Motivation for Interference Subtraction
• Observations– No interference is considered so far
– Concurrent transmissions harm BER performance
– One can further reduce interference from prior information
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S1 S2 S3
R1 R2 R3
T1 T2 T3 T4 T5 T6
S1(1) R1(1) S2(1) R2(1) S3(1) R3(1)
S1(2)
S4
T1 T2 T3 T4 T5 T6 T7
S1(1) R1(1) S2(1) R2(1) S3(1) R3(1)
S1(2) R1(2) S2(2)
S4(1)
R2(2)
S1(3)
Linear Network Analysis
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A five-node linear network
Assumption:Transmission range=1; Interference range=2; Interference free, d>2
Each node successfully receives a messageon an average in every two time slots, the average throughput for direct transmission with interference subtraction is
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Linear Network Analysis
A five-node linear network
For conventional cooperative transmission:a message on an average requires three time slots to be received, the average throughput is
For supplementary cooperative transmission:The average throughput is
24%
42%
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Interference Effects on BER Performance
• Channel resource reuse factor: spatial frequency reuse for scheduling • Link throughput can be increased without bring in significant BER• Trade-off between throughput, reuse factor and end-to-end BER
• Link throughput
is the desired transmission rate
is the reuse factor
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Channel resource reuse factors
End
-to-
end
BE
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3-hop CC without IS6-hop CC without IS9-hop CC without IS3-hop SC with IS6-hop SC with IS9-hop SC with IS
Conclusion
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What we have done1) Optimal solution: QoS routing algorithm for cooperative
networks
2) Interference effects on BER performance
3) Transmission power optimization
4) Throughput analysis
• Future works1) Delay analysis
2) Multi-QoS solution; more insights on BER, delay and throughput
3) System performance for a general network scenario (stochastic geometry)
Thank you
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