OFDM uplink for interactive broadband wireless: analysis and simulation in the presence of carrier, clock and timing errors

Abstract—This paper is concerned with the performance of OFDM when used as a modulation and access technique for the uplink of an interactive broadband wireless system or in the return link of a terrestrial television system. In such an applica-tion, the uplink performance becomes strongly dependent on the discrepancies related to carrier frequencies, sampling frequencies and time references used by different users. In addition, different uplink subcarriers will see different channels since individual subcarriers are allocated to different users. The main purpose of this paper is to provide the analytical tools necessary to quantify the performance of such an uplink by taking into consideration the error sources indicated above. The analysis is made from the uplink users ’ perspective; i.e., the results are presented with the subcarrier index as a parameter. Average uplink user performance is obtained by averaging over the tone index. Extensive computer simulations have been carried out and the results are in strong agreement with the analytical predictions. Index Terms—Broadband wireless systems, interactive broad-band, modulation, OFDM, uplink synchronization. I