Joint Design of Channel and Network Coding for Star Networks

TL;DR

This paper compares the efficiency of network coding and traditional scheduling in star networks, showing that TDMA outperforms RLNC for small message sizes and finite block lengths.

Contribution

It provides a finite-length analysis of throughput for RLNC and TDMA in star networks, identifying conditions where TDMA is more efficient.

Findings

TDMA outperforms RLNC for small message lengths K.

Optimal channel coding rate and block number are derived for maximum throughput.

Finite-length analysis reveals the regimes where each scheme is preferable.

Abstract

Channel coding alone is not sufficient to reliably transmit a message of finite length $K$ from a source to one or more destinations as in, e.g., file transfer. To ensure that no data is lost, it must be combined with rateless erasure correcting schemes on a higher layer, such as a time-division multiple access (TDMA) system paired with automatic repeat request (ARQ) or random linear network coding (RLNC). We consider binary channel coding on a binary symmetric channel (BSC) and q-ary RLNC for erasure correction in a star network, where Y sources send messages to each other with the help of a central relay. In this scenario RLNC has been shown to have a throughput advantage over TDMA schemes as K and q tend to infinity. In this paper we focus on finite block lengths and compare the expected throughputs of RLNC and TDMA. For a total message length of K bits, which can be subdivided into blocks of smaller size prior to channel coding, we obtain the channel coding rate and the number of blocks that maximize the expected throughput of both RLNC and TDMA, and we find that TDMA is more throughput-efficient for small message lengths K and small q.