Interference Cancellation in Two-Path Successive Relay System with Network Coding Chunbo Luo, Dr. Yu Gong & Prof. Fuchun Zheng School of Systems Engineering.

Presentation on theme: "Interference Cancellation in Two-Path Successive Relay System with Network Coding Chunbo Luo, Dr. Yu Gong & Prof. Fuchun Zheng School of Systems Engineering."— Presentation transcript:

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

c.luo@reading.ac.uk Contents Introduction and System Model Physical-layer Network Coding Interference Cancellation Simulation Results Conclusion and Future Work

c.luo@reading.ac.uk Introduction Cooperative networks Demands in wireless communications: Higher data rate Higher spectrum efficiency Reliable connections Lower energy consumption Longer battery life … Dilemma: Limited resource Unlimited requirements Solutions? Cooperative networks

c.luo@reading.ac.uk Introduction Cooperative networks WHY and HOW? Please see one of the cooperative models: two- Path cooperative model Source: S Relays: R Destination: D RELAY

c.luo@reading.ac.uk Introduction Cooperative networks Large and better coverage Lower transmission energy More reliable connection …… There are loads of benefits. But …. The Limit of half-duplex transmission

c.luo@reading.ac.uk Introduction Cooperative networks At the relay: At the destination: R 1 and R 2 alternatively relay the data from S to D. Solution?

c.luo@reading.ac.uk Introduction Cooperative networks But … INTER RELAY INTERFERENCE (IRI)

c.luo@reading.ac.uk 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

c.luo@reading.ac.uk 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.

c.luo@reading.ac.uk IRI Cancellation Why and how does PNC work to reduce IRI? IRI is totally removed!!! At destination, we do another XOR:

c.luo@reading.ac.uk IRI Cancellation Why and how does PNC work to reduce IRI? Key: How does PNC work? The actual received signal at R is:

c.luo@reading.ac.uk 1-0.5*(Magnitude of received signal): 1: A and B are different 0: A and B are the same Physical-layer Network Coding PNC Example-BPSK A: -1, 1 B: -1, 1 So relay received patterns: -2 0 2, using the following equation: If BPSK used, we have: 1 Mapping to 1 0 Mapping to -1 XOR!

c.luo@reading.ac.uk Physical-layer Network Coding XOR in Physical layer: By using certain equations, we have: Y=A B XOR in Physical layer

c.luo@reading.ac.uk 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)

c.luo@reading.ac.uk IRI Cancellation XOR in Physical layer: But …. The system model The transmissions suffer from channel fading and additive noises. How about in practical systems?

c.luo@reading.ac.uk IRI Cancellation In practical system 1) MAP Detection at relays: 2) Joint detection and PNC: 3) Relay transmission

c.luo@reading.ac.uk IRI Cancellation In practical situation: 4) MAP Detection at destination: 5) PNC decoding: where is the result we want!