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Interference Cancellation in Two-Path Successive Relay System with Network Coding. Chunbo Luo, Dr. Yu Gong & Prof. Fuchun Zheng School of Systems Engineering University of Reading United Kingdom 28/09/2010. Introduction and System Model Physical-layer Network Coding - PowerPoint PPT Presentation
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Interference Cancellation in Two-Path Successive Relay System with Network Coding
Chunbo Luo, Dr. Yu Gong & Prof. Fuchun Zheng
School of Systems EngineeringUniversity of Reading
United Kingdom
28/09/2010
Contents
Introduction and System Model Physical-layer Network Coding Interference Cancellation Simulation Results Conclusion and Future Work
IntroductionCooperative networks
•Demands in wireless communications:
Higher data rateHigher spectrum efficiencyReliable connectionsLower energy consumptionLonger battery life…
•Dilemma: Limited resource <-> Unlimited requirements
•Solutions? Cooperative networks
IntroductionCooperative networks
WHY and HOW?
Please see one of the cooperative models: two- Path cooperative model
Source: S Relays: R Destination: D
RELAY
IntroductionCooperative networks
Large and better coverageLower transmission energyMore reliable connection……
There are loads of benefits. But….
The Limit of half-duplex transmission
IntroductionCooperative networks
At the relay:
At the destination:
R1 and R2 alternatively relay the data from S to D.
Solution?
IRI Cancellation Inter relay interference (IRI)
• Interference cancellation schemes• Our scheme: Physical Network Coding (PNC)
What is PNC?Why can PNC solve the problem?How does it work?
Solution
IRI Cancellation
To clearly show the basic mechanism: we use the following ideal model: Ideal environment: no noise, channels are stable (no fading)
Why and how does PNC work to reduce IRI?
R receives:
At n+1 time slot, R transmits the PNC result.
D receives:
Then R performs PNC.
IRI CancellationWhy and how does PNC work to reduce IRI?
IRI is totally removed!!!
At destination, we do another XOR:
IRI CancellationWhy and how does PNC work to reduce IRI?
Key:
How does PNC work?
The actual received signal at R is:
1-0.5*(Magnitude of received signal): 1: A and B are different0: A and B are the same
Physical-layer Network CodingPNC Example-BPSK
A: -1, 1B: -1, 1
So relay received patterns: -2 0 2, using the following equation:
If BPSK used, we have:
1 Mapping to 10 Mapping to -1
XOR!
Physical-layer Network CodingXOR in Physical layer:
By using certain equations, we have:
Y=A B
XOR in Physical layer
Physical-layer Network CodingXOR in Physical layer: But….
How about other modulation schemes? e.g. QPSK
See the table below (It can be found in the paper)
IRI CancellationXOR in Physical layer: But….
The system model
The transmissions suffer from channel fading and additive noises.
How about in practical systems?
IRI CancellationIn practical system
1) MAP Detection at relays:
2) Joint detection and PNC:
3) Relay transmission
IRI CancellationIn practical situation:
4) MAP Detection at destination:
5) PNC decoding:
where is the result we want!
Conclusion and future work
The proposed PNC interference cancellation scheme can effectively reduce IRI
Its performance depends on the accuracy of channel estimation (MAP detection)
PNC can be used in signal processing areas to deal with interference problems
Conclusion and future work
The scenario with direct link available The joint coding and detection Multi-source multi relay scenario The complexity of MAP detection
Thank you!
Interference Cancellation in Two-Path Successive Relay System with Network Coding
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