Distributed Soft Coding with a Soft Input Soft Output (SISO) Relay Encoder in Parallel Relay Channels

TL;DR

This paper introduces a novel distributed soft coding scheme with a SISO relay encoder for parallel relay channels, improving error resilience and coding gains over traditional methods.

Contribution

It proposes the DISC scheme with a new coding design criterion, enhancing performance by mitigating error propagation in relay channels.

Findings

Performance depends on generator sequence weight (GSW) of relay codes.

DISC outperforms conventional soft relaying in error propagation mitigation.

Proposed coding design yields significant coding gains.

Abstract

In this paper, we propose a new distributed coding structure with a soft input soft output (SISO) relay encoder for error-prone parallel relay channels. We refer to it as the distributed soft coding (DISC). In the proposed scheme, each relay first uses the received noisy signals to calculate the soft bit estimate (SBE) of the source symbols. A simple SISO encoder is developed to encode the SBEs of source symbols based on a constituent code generator matrix. The SISO encoder outputs at different relays are then forwarded to the destination and form a distributed codeword. The performance of the proposed scheme is analyzed. It is shown that its performance is determined by the generator sequence weight (GSW) of the relay constituent codes, where the GSW of a constituent code is defined as the number of ones in its generator sequence. A new coding design criterion for optimally assigning the constituent codes to all the relays is proposed based on the analysis. Results show that the proposed DISC can effectively circumvent the error propagation due to the decoding errors in the conventional detect and forward (DF) with relay re-encoding and bring considerable coding gains, compared to the conventional soft information relaying.