A comparison study of the uplink performance of W-CDMA and OFDM for mobile multimedia communications via LEO satellites

This article presents a comparison study of the uplink performance of two well-known transmission schemes, W-CDMA and OFDM, for mobile multimedia communications via LEO satellites. In order to provide a framework for a fair comparison we have considered for both schemes common parameters. including identical channel bandwidth, coding/decoding algorithms and similar net data rate. The values of these parameters have been appropriately selected in accordance with the corresponding UMTS system specifications. For W-CDMA, we propose a receiver structure that eliminates ISI for both channel estimation and equalization at the LEO satellite. For OFDM, we propose a system the design of which is based upon the parameters of W-CDMA for UMTS. For both schemes appropriate transceiver structures are proposed and analyzed and their performance is evaluated in terms of computer simulation. The design of these transceiver structures effectively takes into account the statistical characteristics of the LEO satellite channel, so that the overall system performance is improved. The simulation results evaluating the uplink BER performance for a single user indicate that, although the BER performance of W-CDMA is slightly better than that of OFDM, the performance differences are rather small. Furthermore, these differences in performance become even smaller when channel coding is applied and when LOS conditions between the mobile terminal and the LEO satellite exist. Since these results have not shown a clear-cut winner, further comparative studies are required in order to identify the most appropriate transmission scheme for applications supporting global mobile multimedia communication via LEO satellite networks. Such studies should include determination of the downlink EER performance as well as spectrum efficiency and capacity performance evaluations fur both up and down satellite communication links.