A comparison between APSK and QAM in wireless tactical scenarios for land mobile systems

Marco Baldi,Franco Chiaraluce,Sebastiano Schillaci,Rossano Marchesani,Antonio De Angelis

doi:10.1186/1687-1499-2012-317

Abstract

We evaluate the performance of APSK modulation for wireless systems and compare it with the performance of more conventional QAM systems. In previous literature, the analysis of APSK has been mainly focused on the AWGN channel. This channel model provides useful insights when APSK is used in satellite systems, while it is important to consider more complex channel models for its use in terrestrial wireless applications. In particular, we consider wireless tactical scenarios for land mobile systems, that are of interest for military applications, and provide several numerical examples. First, we explore the effects on the total degradation of the reduced PAPR, typical of APSK, also taking into account the nonlinearity of HPAs and the need to use adaptive predistortion. Then, the bit error rate performance is assessed by simulation, for some typical multipath scenarios with decision feedback equalization, also including the presence of turbo channel coding. Our analysis shows that APSK can be a valid alternative to QAM in all cases in which the nonlinear effects due to HPAs cannot be neglected.

Highlights

Mobile radio systems require highly bandwidth-efficient modulation schemes, because of the limited resources of the available radio spectrum
amplitude-phase shift keying (APSK) has been proposed in the framework of the DVB-S2 standard [13] and its performance has been widely investigated over the additive white Gaussian noise (AWGN) channel, by considering typical satellite scenarios, in the presence of high power amplifiers (HPAs)
Our analysis aims at showing that, in this context, APSK can be advantageous with respect to more conventional modulation schemes, like quadrature amplitude modulation (QAM)

Summary

Introduction

Mobile radio systems require highly bandwidth-efficient modulation schemes, because of the limited resources of the available radio spectrum. APSK has been proposed in the framework of the DVB-S2 standard [13] and its performance has been widely investigated over the AWGN channel, by considering typical satellite scenarios, in the presence of HPAs. several different adaptive techniques to compensate for nonlinear effects have been studied, and the improvements achievable by adding turbo channel codes have been estimated [11,14]. In Section ‘Performance of APSK in multipath scenarios’, simulations considering the use of turbo channel codes [28] will be presented In such case, the encoder of a binary turbo code is added at the TX, before the bit to symbol mapping (i.e., according to a “pragmatic” approach), while, at the RX, a decoder based on the BCJR algorithm is inserted after the decision device. Changing only the constellation points positions does not modify the shape of the power spectral density of the modulated signal, which is [34]: Pss(f )

Ts σa2

Conclusion