Adaptive coding and modulation in an OFDM-TDMA communication system

The capacity of a wireless communication system based on the OFDM transmission technique is analysed. The considered system, which includes a TDMA approach, is designed for mobile access to different multimedia services, such as speech, video, e-mail and file transfer. In order to support a variety of services on the one hand and to take into account the behaviour of the frequency-selective radio channel on the other hand, an adaptive allocation of modulation and coding scheme is supplied. For this purpose, an optimal combination of modulation scheme and code rate is determined in a first step. Using these results, the capacity of such a system is analysed by calculating the number of supported users within a cell and comparing these numbers to a system with fixed modulation/coding.