An Efficient Multi-Mode Channel Tracking Scheme under Different Velocities in OFDM Systems

In this paper an efficient channel estimation algorithm under different mobile velocities in orthogonal frequency division multiplexing (OFDM) systems is considered. Conventional channel estimation algorithms track adaptively time-varying channels using high performance approaches. However, the power consumption for these algorithms are usually tremendous. On the other hand, users usually move with low speeds in most cases and they do not require such a complicated channel tracker. In view of this we classify the moving speeds into three modes. We then propose a multi-mode channel tracking scheme with different complexities and tracking capabilities. A novel inverse mean-square error (IMSE) velocity metric estimator is also provided along with a mode selection procedure to detect the proper tracking mode. Simulation results show that under the OFDMA mode of the IEEE 802.16e-2005 standard, the proposed algorithm can track the velocity variation very well and perform channel estimation using the most efficient tracking mode. The power consumption is thus decreased significantly without degrading the system performance.