The Effect of Subcarrier-Based Channel Estimation on the BER Bound of Turbo Coded OFDM/SDMA System

In this paper, we study the performance of the channel estimation in a Turbo coded, orthogonal frequency division multiplexing (OFDM) with multiple antennas at the receiver. We survey the accuracy of the channel estimation for different number of users and different number of pilot subcarriers. Moreover, since there is not a closed form solution to the BER of the Turbo coded system for different number of constellation size. We develop an equation to obtain the BER bound of the Turbo coded OFDM/SDMA system with M-ary quadrature amplitude modulation (MQAM) in the Rayleigh flat fading channel as a function of the signal constellation and characteristic of the Turbo code with a curve fitting and then propose a method for selecting switching threshold in adaptive modulation case.