Resource Allocation Design for Next-Generation Multiple Access: A Tutorial Overview

Multiple access is the cornerstone technology for each generation of wireless cellular networks, which fundamentally determines the method of radio resource sharing and significantly influences both the system performance and transceiver complexity. Meanwhile, resource allocation (RA) design plays a crucial role in multiple access, as it can manage both encompassing radio resources and interference, and it is critical for providing high-speed and reliable communication services to multiple users. Given that the RA design is intrinsically scenario-specific and the optimization tools for RA design are typically varied, in this article, we present a comprehensive tutorial overview for junior researchers in this field, aiming to offer a foundational guide for RA design in the context of next-generation multiple access (NGMA). Our discussion spans a broad range of fundamental topics: from typical system models, through intriguing problem formulation in RA design, to the exploration of various potential optimization solution methodologies. Initially, we identify three types of channels in future wireless cellular networks over which NGMA will be implemented, namely, natural channels, reconfigurable channels, and functional channels. Natural channels are traditional uplink and downlink communication channels; reconfigurable channels are defined as channels that can be proactively reshaped via emerging platforms or techniques, such as intelligent reflecting surface (IRS), unmanned aerial vehicle (UAV), and movable/fluid antenna (M/FA); and functional channels support not only communication but also other functionalities simultaneously, with typical examples, including integrated sensing and communication (ISAC) and joint computing and communication (JCAC) channels. Then, we introduce NGMA models applicable to these three types of channels that cover most of the practical communication scenarios of future wireless communications. Subsequently, we articulate the key optimization technical challenges inherent in the RA design for NGMA, categorizing them into rate-, power-, and reliability-oriented RA designs. The corresponding optimization approaches for solving the formulated RA design problems are then presented. Finally, the simulation results are presented and discussed to elucidate the practical implications and insights derived from RA designs in NGMA.

I. Introduction

The 6G wireless networks are envisioned to provide massive, immersive, and reliable communications, which are expected to revolutionize our daily lives. To this end, the IMT-2030 framework has highlighted three groundbreaking usage scenarios: ubiquitous connectivity, ISAC, and integrated AI and communication [1]. These scenarios lay the groundwork for a sophisticated and intelligent digital world, serving as a pivotal data foundation. Moreover, these innovative services open doors to novel business models and applications, simultaneously introducing unprecedented challenges in the evolution of 6G wireless communication technologies. In particular, massive communication is expected to accommodate an extraordinary connectivity density ranging from to [1], encompassing a variety of ubiquitous wideband and IoT devices across a broad spectrum of coverage and mobility. Beyond these capabilities, immersive communication demands stringent requirements on peak and experienced data rates, latency, and connectivity capacity, which are crucial for supporting a wide variety of applications in the entertainment, education, and manufacturing sectors.