Quantized Compute and Forward: A Low-Complexity Architecture for Distributed Antenna Systems

TL;DR

This paper introduces a low-complexity distributed antenna system architecture using quantized compute and forward, employing simple relay operations and LDPC codes for efficient uplink communication.

Contribution

It proposes a novel low-complexity scheme with scalar quantization and decentralized decoding, suitable for distributed antenna systems with simple relays.

Findings

Linear complexity in coding block length

Polynomial complexity in number of relays

Effective message retrieval via Gaussian elimination

Abstract

We consider a low-complexity version of the Compute and Forward scheme that involves only scaling, offset (dithering removal) and scalar quantization at the relays. The proposed scheme is suited for the uplink of a distributed antenna system where the antenna elements must be very simple and are connected to a oint processor via orthogonal perfect links of given rate R0. We consider the design of non-binary LDPC codes naturally matched to the proposed scheme. Each antenna element performs individual (decentralized) Belief Propagation decoding of its own quantized signal, and sends a linear combination of the users' information messages via the noiseless link to the joint processor, which retrieves the users' messages by Gaussian elimination. The complexity of this scheme is linear in the coding block length and polynomial in the system size (number of relays).