Queueing Theoretic Models for Multiuser MISO Content-Centric Networks With SDMA, NOMA, OMA and Rate-Splitting Downlink

Multiuser, Multiple Input, Single Output (MU-MISO) systems are indispensable in next-generation wireless networks such as 5G and 6G. The spatial diversity of MISO has been leveraged in these wireless networks to improve the capacity. Furthermore, several recent studies have utilised redundancies in the content request along with this spatial diversity for further capacity improvements. In such systems, the MISO Max-Min Fair (MMF) Beamforming schemes based on SDMA, NOMA, OMA and Rate-Splitting are shown to improve the delivery rates. However, in these studies the key aspects such as the queueing delays in the downlink and the user dynamics have generally been ignored. In this work, we study how queueing, beamforming and user dynamics affect the Quality-of-Service (user delay) of downlink in MU-MISO content centric networks (CCNs). We also show that a Simple Multicast Queue (SMQ) developed for SISO, when adapted to MU-MISO provides good performance due to its inherent stability. However, we observe that MMF Beamforming coupled with SMQ can be unfair to users with good channels. Thus, we propose an alternative scheme, called Dual-SMQ to address this problem. We also provide theoretical approximations for the mean delay experienced by the users in such systems.