Asynchronous Multiple Access in Optical Wireless Scattering Communication: Achievable Transmission Rates and Receiver Design

TL;DR

This paper explores asynchronous multi-user optical wireless scattering communication, modeling misalignment with HMM, and develops algorithms for channel estimation and joint decoding, demonstrating near-optimal performance through simulations and experiments.

Contribution

It introduces a novel HMM-based model for asynchronous optical wireless communication and proposes effective algorithms for channel estimation and multi-user decoding.

Findings

Proposed HMM model accurately characterizes user misalignment.

Channel estimation with EM algorithm performs well in experiments.

Joint decoding algorithms achieve near-optimal rates.

Abstract

We investigate the asynchronous multiple user access communication in optical wireless scattering communication, where different users transmit signals without perfect alignment in the time domain. Firstly, we characterize the received signal based on hidden markov model (HMM) such that the misalignment among different users can be characterized by the state transition. Then, we investigate the achievable rates based on that of the HMM and obtain the approximated solution using Monte Carlo method. We propose the channel estimation based on expectation-maximization (EM) algorithm. Furthermore, we adopt Viterbi and Bahl-Cocke-Jelinek-Raviv (BCJR) algorithms for joint iterative multi-user decoding. Numerical and experimental results illustrate the performance of proposed channel estimation, joint detection and decoding. It is seen from the experimental results that the proposed approaches perform close to the simulation results.