A distributed algorithm for dynamic sub-channel assignment in a multi user OFDM communication system

In this paper we propose and study a Sub-Channel Selective OFDM spread spectrum system and a distributed algorithm for sub-channel allocation. The proposed system is a combination of OFDMA and OFDM-CDMA systems. For each user the maximal ratio combining weights of the sub-channels are used as channel information. The algorithm implements a simple but sub-optimal version of the water filling power allocation, thus increasing the transmitter power efficiency and decreasing the interference generated for other users. This algorithm also provides the ability to offer different Quality of Service (QoS) levels for different users. The convergence of the algorithm and its performance have been studied through simulation. The proposed system has significant advantage in BER performance, over the conventional OFDM-SS system.