# Radio Resource Allocation for Multicarrier-Low Density Spreading Multiple Access

## TL;DR

This paper investigates radio resource allocation in MC-LDSMA, proposing optimal and suboptimal algorithms that enhance spectral efficiency and fairness over traditional methods like OFDMA.

## Contribution

It derives the optimal power and subcarrier partitioning schemes for MC-LDSMA and introduces practical algorithms for resource allocation.

## Key findings

- Proposed algorithms outperform static allocation methods.
- MC-LDSMA improves spectral efficiency and fairness.
- Subcarrier loading and spreading impact performance.

## Abstract

Multicarrier-low density spreading multiple access (MC-LDSMA) is a promising multiple access technique that enables near optimum multiuser detection. In MC-LDSMA, each user's symbol spread on a small set of subcarriers, and each subcarrier is shared by multiple users. The unique structure of MC-LDSMA makes the radio resource allocation more challenging comparing to some well-known multiple access techniques. In this paper, we study the radio resource allocation for single-cell MC-LDSMA system. Firstly, we consider the single-user case, and derive the optimal power allocation and subcarriers partitioning schemes. Then, by capitalizing on the optimal power allocation of the Gaussian multiple access channel, we provide an optimal solution for MC-LDSMA that maximizes the users' weighted sum-rate under relaxed constraints. Due to the prohibitive complexity of the optimal solution, suboptimal algorithms are proposed based on the guidelines inferred by the optimal solution. The performance of the proposed algorithms and the effect of subcarrier loading and spreading are evaluated through Monte Carlo simulations. Numerical results show that the proposed algorithms significantly outperform conventional static resource allocation, and MC-LDSMA can improve the system performance in terms of spectral efficiency and fairness in comparison with OFDMA.