A Framework for the Transmission of Multimedia Traffic using HM and RS Coding over Nakagami-M Channels

Abstract

Hierarchical modulation (HM) provides different levels of error performance for the high and low priority bits modulated. This differentiation can be aligned to various classes of multimedia traffic demanding different levels of error rate performance. In a previous cross-layer design scheme, which combined conventional modulation at physical layer with RS coding at the application layer, an unequal error protection mechanism was used at the application layer for guaranteeing quality of service for various classes of multimedia traffic. Instead of using only a single layer, in this paper we present a more flexible two layer cross-layer design framework for unequal error protection, combining RS coding at the application layer with HM at the physical layer. Furthermore, in order to improve error performance of the system, a signal space diversity (SSD) scheme is also incorporated into the physical layer of the framework. Without consuming additional transmit power and bandwidth, the use of the SSD HM in the cross-layer design system resulted in significant gains when compared to the non-SSD, standard HM system. It is shown that the cross-layer design system with SSD HM has a 10dB gain over the non-SSD HM system in a Nakagami m=1 channel with a frame error rate target of 10−4.