Multi-User Ranging Code Detection in OFDMA System Using MMLD Algorithm for Improving Detection Performance

Successive user detection algorithm is used to observe the multi user ranging signals and calculate there corresponding parameters. Using IEEE 802.16 specification in Orthogonal Frequency Division Multiple Access (OFDMA), initial ranging method designed an algorithm called Moment Maximum Likelihood Detection (MMLD) to detect the codes assigned and predicting offset timing. The objective function which is derived from the Expectation Maximization (EM) algorithm is used in the MMLD to cancel the channel estimation errors and Multiple Access Interference (MAI). To reduce the MAI over the iteration, the Maximum Likelihood Estimation (MLE) algorithm is designed in the MMLD. The experimental results indicate that the system is highly accurate. Keywords— IEEE 802.16e, OFDMA System, Initial Ranging, MMLD, Timing Offset. __________________________________________________*****_________________________________________________