On the Bit Error Rate of Opportunistic Wireless Systems that Employ Non-Square Quadrature Amplitude Modulations

One of the phenomena that most affects the performance of wireless telecommunications systems is the fading. Thus, several techniques have been proposed to mitigate its effects. These techniques include the so-called opportunistic transmissions, which are characterized because the transmission of the information is made only when the instantaneous fading amplitude is above a threshold value. The performance of this kind of technique has been evaluated in different works employing square quadrature amplitude modulations (S-QAM). Unlike those works, the opportunistic transmission performance is evaluated considering non-square quadrature amplitude modulations (NS-QAM). In particular, 8-QAM and 32-QAM constellations are considered. The system model considers the presence of additive white Gaussian noise and flat and slow Rayleigh fading. The performance analysis is based on the mean bit error rate as a function of the signal-to-noise ratio. For this, Monte-Carlo simulations are carried out in some relevant scenarios. Additionally, comparisons between the performance of S-QAM and NS-QAM are also made.

I. Introduction

Due to the significant demand for high transmission rates in wireless communication systems, research in this area is necessary in order to guarantee an adequate quality in the services and applications offered. Many of this research is aimed at mitigating the undesirable effects of the wireless channel. Specifically, the fading is the main phenomena that affects this type of communications [1] .