Fluid antenna multiple access under Nakagami-m fading channels

Abstract

Fluid antenna systems (FASs) have recently emerged as a key enabler for the forthcoming sixth generation (6G) of wireless communication systems. The performance benefits of fluid antennas have been explored in multiuser systems in an approach known as fluid antenna multiple access (FAMA). This thesis investigates FAMA under Nakagami-m fading channels, considering different correlation models. For slow FAMA, considering the constant correlation model, exact expressions for the outage probability (OP) based on the signal-to-interference ratio (SIR) or the signal-to-interference plus noise ratio (SINR) are presented. An upper bound for the SIR-based OP and an approximate expression for the SINR-based OP are derived using the Gauss-Laguerre quadrature approach. Bounds for the multiplexing gain are also derived. Considering the new and realistic spatial block-correlation model, this thesis also investigates slow, fast, and opportunistic FAMA under the effect of Nakagami-m fading channels. For this correlation model, expressions for the OP, based on the SIR, are derived for slow FAMA. Interestingly, we provide mathematical relationships that allow the expressions of fast FAMA to be obtained from slow FAMA. Multiplexing gains are presented for an opportunistic FAMA (O-FAMA) network for both slow and fast FAMA scenarios. Additionally, the analysis is extended to networks that employ maximum ratio transmission (MRT) precoding at base stations (BSs), called MRT-FAMA networks. The analytical results are validated through Monte Carlo simulations, under various channel and system parameters. To the best of author’s knowledge, the expressions derived in this thesis are original.