Effective throughput for coded OFDM/SDMA systems with pilot-assisted channel estimation

Abstract

This paper investigates the performance of coded orthogonal frequency division multiflexing (OFDM) systems with receiving adaptive array, through which multiple users with single-element transmitting antenna are supported simultaneously by spatial division multiple access (SDMA). We characterize the performance of an OFDM/SDMA systems by effective throughput, which is essentially the average number of data bits in an OFDM symbol after considering the erroneous packet transmissions and modulation scheme by excluding the overhead from coding and pilots for channel estimation. Optimization of system operating parameters can be achieved through the maximization of effective throughput. The focus of this paper is to study the impact of pilot density and the number of users on the performance of coded OFDM/SDMA systems. Through extensive computer simulation, we how that using more pilots always improves bit error rate (BER) performance, but may reduce effective throughput. The optimal number of pilots together with the modulation scheme can he determined by maximizing the effective throughput for given operating signal-to-noise ratio (SNR). It is also shown that the system performance degrades gradually with the increase of users. For a system with a six-element adaptive array, the effective throughput with 5 users is lower than that with 4 users for a certain range of SNR. This indicates that the maximal number of users supportable by the system should consider the effective throughput. © 2003 IEEE.