Coded Fluid Antenna Multiple Access Over Fast Fading Channels

Abstract

Enabled by the emerging fluid antenna system (FAS) technology, fast fluid antenna multiple access (FAMA) provides a massive connectivity scheme which is able to serve on the same physical channel hundreds of users, without the need of precoding nor interference cancellation at each user. This is, however, only possible if we know the antenna position (i.e., port) in which the ratio of the instantaneous signal energy to the sum-interference plus noise signal energy is maximized on a per-symbol basis. In this letter, we address how fast FAMA can be approached using practical channel codes. This technique is referred to as coded FAMA. An iterative decoding receiver with a novel soft-decision port detector and the correlated demapper is proposed. Also, the average mutual information (AMI) for the coded FAMA system is derived to indicate the system’s achievable transmission rate. Our results reveal that the spectral efficiency of the coded FAMA system can well approach the AMI with the proposed iterative decoding receiver. Moreover, it is illustrated that under rich scattering fast fading channels, the proposed coded FAMA system can support 120 users on the same channel to achieve a network spectral efficiency of 75 bps/Hz, without precoding.