User Association and Resource Allocation in Unified NOMA Enabled Heterogeneous Ultra Dense Networks

TL;DR

This paper proposes a flexible unified NOMA framework for HUDNs in 5G, focusing on user association and resource allocation to enhance connectivity and spectrum efficiency.

Contribution

It introduces a novel unified NOMA framework combining power-domain and code-domain NOMA, tailored for HUDNs, with case studies demonstrating its effectiveness.

Findings

Unified NOMA framework improves spectrum efficiency.

Effective user association and resource allocation strategies.

Case studies validate the proposed approach.

Abstract

Heterogeneous ultra dense networks (HUDNs) and non-orthogonal multiple access (NOMA) have been identified as two proposing techniques for the fifth generation (5G) mobile communication systems due to their great capabilities to enhance spectrum efficiency. This article investigates the application of NOMA techniques in HUDNs to support massive connectivity in 5G systems. Particularly, a unified NOMA framework is proposed, including power-domain NOMA and code-domain NOMA, which can be configured flexibly to serve different applications scenarios. As a further advance, the unified NOMA framework enabled HUDNs is further investigated, with particular focuses on the user association and resource allocation. Two case studies are provided for demonstrating the effectiveness of the unified NOMA enabled HUDNs. Finally, some main challenges and promising research directions in NOMA enabled HUDNs are identified. Index Terms Heterogeneous ultra dense networks, non-orthogonal multiple access, massive connectivity, user association, and resource allocation