Modeling and Analysis of SCMA Enhanced D2D and Cellular Hybrid Network

TL;DR

This paper models and analyzes the use of SCMA in hybrid D2D and cellular networks, demonstrating significant spectral efficiency gains and providing optimal resource allocation strategies.

Contribution

It introduces a stochastic geometry framework for SCMA in hybrid networks, compares it with OFDMA, and derives optimal activation and resource allocation policies.

Findings

SCMA significantly improves area spectral efficiency over OFDMA.

The ASE gain scales linearly with SCMA codeword dimension.

Optimal resource allocation rules are derived for both underlaid and overlaid modes.

Abstract

Sparse code multiple access (SCMA) has been recently proposed for the future wireless networks, which allows non-orthogonal spectrum resource sharing and enables system overloading. In this paper, we apply SCMA into device-to-device (D2D) communication and cellular hybrid network, targeting at using the overload feature of SCMA to support massive device connectivity and expand network capacity. Particularly, we develop a stochastic geometry based framework to model and analyze SCMA, considering underlaid and overlaid mode. Based on the results, we analytically compare SCMA with orthogonal frequency-division multiple access (OFDMA) using area spectral efficiency (ASE) and quantify closed-form ASE gain of SCMA over OFDMA. Notably, it is shown that system ASE can be significantly improved using SCMA and the ASE gain scales linearly with the SCMA codeword dimension. Besides, we endow D2D users with an activated probability to balance cross-tier interference in the underlaid mode and derive the optimal activated probability. Meanwhile, we study resource allocation in the overlaid mode and obtain the optimal codebook allocation rule. It is interestingly found that the optimal SCMA codebook allocation rule is independent of cellular network parameters when cellular users are densely deployed. The results are helpful in the implementation of SCMA in the hybrid system.