FAS-Assisted NOMA Short-Packet Communication Systems

In this letter, we investigate a fluid antenna system (FAS)-assisted downlink non-orthogonal multiple access (NOMA) for short-packet communications. The base station (BS) adopts a single fixed antenna, while both the central user (CU) and the cell-edge user (CEU) are equipped with a FAS. Each FAS comprises
$N$
flexible positions (also known as ports), linked to
$N$
arbitrarily correlated Rayleigh fading channels. We derive expressions for the average block error rate (BLER) of the FAS-assisted NOMA system and provide asymptotic BLER expressions. We determine that the diversity order for CU and CEU is
$N$
, indicating that the system performance can be considerably improved by increasing
$N$
. Simulation results validate the great performance of FAS.