Analytical Studies of Fragmented-Spectrum Multi-Level OFDM-CDMA Technique in Cognitive Radio Networks

TL;DR

This paper investigates a multi-user resource allocation method for fragmented-spectrum OFDM-CDMA in cognitive radio networks, focusing on spectrum sensing, orthogonal coding, and BER analysis to optimize secondary user performance.

Contribution

It introduces a novel framework combining spectrum sensing, multi-level orthogonal coding, and BER analysis for cognitive radio resource management in frequency-selective channels.

Findings

Closed-form BER expression derived for cognitive radio receivers.

Simulation results closely match analytical predictions.

Effective spectrum sensing improves secondary user communication quality.

Abstract

In this paper, we present a multi-user resource allocation framework using fragmented-spectrum synchronous OFDM-CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, a channel sensing and estimation method is used to obtain information of subcarrier availability. Given this information, some real-valued multi-level orthogonal codes, which are orthogonal codes with values of $\{\pm1,\pm2,\pm3,\pm4, ... \}$, are provided for emerging new users, i.e., cognitive radio users. Additionally, we have obtained a closed form expression for bit error rate of cognitive radio receivers in terms of detection probability of primary users, CR users' sensing time and CR users' signal to noise ratio. Moreover, simulation results obtained in this paper indicate the precision with which the analytical results have been obtained in modeling the aforementioned system.