High Throughput Random Access via Codes on Graphs: Coded Slotted ALOHA

TL;DR

This paper introduces coded slotted ALOHA (CSA), a novel random access scheme that enhances throughput and power efficiency by combining coding and iterative interference cancellation, outperforming previous methods like IRSA.

Contribution

The paper presents CSA, a new scheme generalizing IRSA, with a graph-based decoding interpretation and optimized performance analysis for high throughput in random access networks.

Findings

Achieves throughput up to 0.8 in simulations

Generalizes IRSA with coding for better performance

Demonstrates power efficiency advantages

Abstract

In this paper, coded slotted ALOHA (CSA) is introduced as a powerful random access scheme to the MAC frame. In CSA, the burst a generic user wishes to transmit in the MAC frame is first split into segments, and these segments are then encoded through a local a packet-oriented code prior to transmission. On the receiver side, iterative interference cancellation combined with decoding of the local code is performed to recover from collisions. The new scheme generalizes the previously proposed irregular repetition slotted ALOHA (IRSA) technique, based on a simple repetition of the users' bursts. An interpretation of the CSA interference cancellation process as an iterative erasure decoding process over a sparse bipartite graph is identified, and the corresponding density evolution equations derived. Based on these equations, asymptotically optimal CSA schemes are designed for several rates and their performance for a finite number of users investigated through simulation and compared to IRSA competitors. Throughputs as high as 0.8 are demonstrated. The new scheme turns out to be a good candidate in contexts where power efficiency is required.