interference cancellation in two-path successive relay system with network coding chunbo luo, dr. yu...
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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
c.luo@reading.ac.uk
Contents
Introduction and System Model Physical-layer Network Coding Interference Cancellation Simulation Results Conclusion and Future Work
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Introduction
Cooperative networks
•Demands in wireless communications:
Higher data rateHigher spectrum efficiencyReliable connectionsLower energy consumptionLonger battery life…
•Dilemma: Limited resource <-> Unlimited requirements
•Solutions? Cooperative networks
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Introduction
Cooperative networks
WHY and HOW?
Please see one of the cooperative models: two- Path cooperative model
Source: S Relays: R Destination: D
RELA
Y
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Introduction
Cooperative networks
Large and better coverageLower transmission energyMore reliable connection……
There are loads of benefits. But….
The Limit of half-duplex transmission
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Introduction
Cooperative networks
At the relay:
At the destination:
R1 and R2 alternatively relay the data from S to D.
Solution?
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Introduction
Cooperative networks
But… INTER RELAY INTERFERENCE (IRI)
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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
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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.
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IRI Cancellation
Why and how does PNC work to reduce IRI?
IRI is totally removed!!!
At destination, we do another XOR:
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IRI Cancellation
Why and how does PNC work to reduce IRI?
Key:
How does PNC work?
The actual received signal at R is:
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1-0.5*(Magnitude of received signal): 1: A and B are different0: A and B are the same
Physical-layer Network Coding
PNC 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!
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Physical-layer Network Coding
XOR in Physical layer:
By using certain equations, we have:
Y=A B
XOR in Physical layer
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Physical-layer Network Coding
XOR in Physical layer: But….
How about other modulation schemes? e.g. QPSK
See the table below (It can be found in the paper)
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IRI Cancellation
XOR in Physical layer: But….
The system model
The transmissions suffer from channel fading and additive noises.
How about in practical systems?
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IRI Cancellation
In practical system
1) MAP Detection at relays:
2) Joint detection and PNC:
3) Relay transmission
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IRI Cancellation
In practical situation:
4) MAP Detection at destination:
5) PNC decoding:
where is the result we want!
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Simulation results
Gaussian model:
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Simulation results
Rayleigh model:
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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
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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
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Thank you!
Interference Cancellation in Two-Path Successive Relay System with Network Coding
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