Downlink Channel Estimation Model for 802.16e OFDMA System

In 802.16e OFDMA systems, noise and co-channel interference on pilots degrade the accuracy of channel state information (CSI) obtained from channel estimation (CE) and system performance is deteriorated. To evaluate the system performance loss due to imperfect CSI, CE model should be used to incorporate noise and interference's impact on CSI into system level simulator (SLS). In this paper, a CE model, which considers 802.16e OFDMA system's pilot pattern and subcarrier randomization, are proposed. The signal model of 802.16e OFDMA system's CE under noise and interference is presented first. Then the error of CSI estimation by LMMSE channel estimator is derived. The proposed CE model covers the main parts of CSI error. Simulation results show it is suitable for SLS by providing a good approximation to estimated CSI instead of performing true LMMSE CE.