Application of Raptor Coding With Power Adaptation to DVB Multiple Access Channels

Abstract

In this paper we propose a scheme to increase the channel capacity of Digital Video Broadcasting (DVB) systems which is also extendable to Return Channel via Satellite (DVB-RCS) scenarios. This increase is made possible by introduction of a new interfering channel to an exiting DVB channel. The interfering channel uses Raptor code. Through successive decoding in the destination, the data of main and interfering sources is decoded. We examine the case of sources with equal transmit power levels, however, as in all Multiple Access Channel (MAC) detection methods, there should be a power difference between the two sources to achieve higher rates. We demonstrate that when the power difference exists, there is a tradeoff between achieved rate and power efficiency and we will find the optimum power allocation scenario for this tradeoff. A power adaptation scheme is proposed that allocates the optimal power to the interfering channel based on an estimate of the main channel's condition. This estimate is obtained from the amount of overhead required by the destination for the successful decoding of the message. Therefore, the interfering source is able to adapt itself to the system without having any access to Channel State Information (CSI) of the main channel.