Channel coding and decoding in a relay system operated with physical-layer network coding

  • Authors:

  • Shengli Zhang;Soung-Chang Liew

  • Affiliations:

  • Information Engineering Department, the Chinese University of Hong Kong;Communication Engineering Department, Shenzhen University, China

  • Venue:
  • IEEE Journal on Selected Areas in Communications - Special issue on network coding for wireless communication networks
  • Year:
  • 2009

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Abstract

This paper investigates link-by-link channel-coded PNC (Physical layer Network Coding), in which a critical process at the relay is to transform the superimposed channel-coded packets received from the two end nodes (plus noise), Y3 = X1+ X2+W3, to the network-coded combination of the source packets, S1 ⊕ S2. This is in contrast to the traditional multiple-access problem, in which the goal is to obtain both S1 and S2 explicitly at the relay node. Trying to obtain S1 and S2 explicitly is an overkill if we are only interested in S1 ⊕ S2. In this paper, we refer to the transformation Y3 → S1 ⊕ S2 as the Channel-decoding-Network-Coding process (CNC) in that it involves both channel decoding and network coding operations. This paper shows that if we adopt the Repeat Accumulate (RA) channel code at the two end nodes, then there is a compatible decoder at the relay that can perform the transformation Y3 → S1 ⊕ S2 efficiently. Specifically, we redesign the belief propagation decoding algorithm of the RA code for traditional point-to-point channel to suit the need of the PNC multiple-access channel. Simulation results show that our new scheme outperforms the previously proposed schemes significantly in terms of BER without added complexity.