Channel estimation techniques in OFDM-IDMA systems

In this paper, pilot based channel estimation techniques for orthogonal frequency division multiplexing-interleave division multiple access (OFDM-IDMA) systems are investigated. Least Squares (LS) and Minimum Mean Square Error (MMSE) algorithms which are also utilized in pure OFDM systems to estimate the channel frequency responses, are used to obtain channel coefficients. The performance of OFDM-IDMA system is evaluated on the basis of Bit Error Rate (BER) and Mean Square Error (MSE) for different estimation algorithms. It is confirmed in this paper that, OFDM-IDMA system using MMSE estimation algorithm shows much better performance than LS estimation algorithm. However, MMSE algorithm has the disadvantage of being more complex. Because of being multiuser system, the performance of OFDM-IDMA is also evaluated for different user numbers. It is shown that, the system performance decreases as long as the number of user is increased¹.