A Plotkin-Alamouti Superposition Coding Scheme for Cooperative Broadcasting in Wireless Networks

TL;DR

This paper introduces a novel superposition coding scheme combining Plotkin's linear codes with Alamouti's transmit diversity for cooperative broadcasting in wireless networks, enhancing robustness and diversity over fading channels.

Contribution

It proposes a new Plotkin-Alamouti superposition coding scheme that improves cooperative broadcasting performance in wireless networks with diverse node distances.

Findings

Enhanced diversity order in Rayleigh fading channels

Improved robustness to channel estimation errors

Effective superposition coding with over-the-air mixing

Abstract

This paper deals with superposition coding for cooperative broadcasting in the case of two coordinated source nodes, as introduced in the seminal work of Bergmans and Cover in 1974. A scheme is introduced for two classes of destination (or relay) nodes: Close nodes and far nodes, as ranked by their spatial distances to the pair of transmitting nodes. Two linear codes are combined using the (u,u+v)-construction devised by Plotkin to construct two-level linear unequal error protection (LUEP) codes. However, instead of binary addition of subcode codewords in the source encoder, here modulated subcode sequences are combined at the destination (or relay) nodes antennae. Bergmans and Cover referred to this as over-the-air mixing. In the case of Rayleigh fading, additional diversity order as well as robustness to channel estimation errors are obtained when source nodes transmit pairs of coded sequences in accordance to Alamouti's transmit diversity scheme. We refer to this combination as a Plotkin-Alamouti scheme and study its performance over AWGN and Rayleigh fading channels with a properly partitioned QPSK constellation.