Study on Downlink Spectral Efficiency in Orthogonal Frequency Division Multiple Access Systems

TL;DR

This paper investigates the statistical properties of co-channel interference in downlink OFDMA systems, revealing that interference does not follow a Gaussian distribution and analyzing its impact on spectral efficiency.

Contribution

It provides the first detailed statistical model of CCI in downlink OFDMA, showing its heavy-tailed nature and deriving spectral efficiency based on this model.

Findings

CCI PDFs have heavy tails, deviating from Gaussian assumptions.

Derived closed-form expressions for CCI PDFs in special cases.

Numerical and simulation results validate the statistical model and spectral efficiency analysis.

Abstract

In previous studies on the capacity of orthogonal frequency division multiple access (OFDMA) systems, it is usually assumed that co-channel interference (CCI) from adjacent cells is a Gaussian-distributed random variable. However, very-little work shows that the Gaussian assumption does not hold true in OFDMA systems. In this paper, the statistical property of CCI in downlink OFDMA systems is studied, and spectral efficiency of downlink OFDMA system is analyzed based on the derived statistical model. First, the probability density function (PDF) of CCI in downlink OFDMA cellular systems is studied with the considerations of path loss, multipath fading and Gaussian-like transmit signals. Moreover, some closed-form expressions of the PDF are obtained for special cases. The derived results show that the PDFs of CCI are with a heavy tail, and significantly deviate from the Gaussian distribution. Then, based on the derived statistical properties of CCI, the downlink spectral efficiency is derived. Numerical and simulation results justify the derived statistical CCI model and spectral efficiency.