Study On Channel Estimation Based On Pilot-Assisted In OFDM Systems

As the growing demand of broadband wireless communications, its theory and technology have become the highest research in the field of communications. Orthogonal frequency division multiplexing (OFDM) as the representative of the multi-carrier modulation is a promising technique which has become one key technology in the new filed of wireless mobile communications. Since the radio channel of OFDM systems is frequency selective and time-varying, a dynamic estimation of channel must be achieved before the demodulation of the transmitted OFDM signals. Considered the complexity of algorithm, the pilot-assisted channel estimation technique has received considerable attention as an effective approach for solving the channel estimation problems in recent years.In this paper, the existed pilot-assisted channel estimation algorithms in OFDM systems are investigated in detail. OFDM technology is widely studied and currently adopted in several wireless standards, and IEEE802.11a is undoubtedly a very special standard among these wireless LAN standards. Based on IEEE802.11a standard, the conventional channel estimation algorithms in OFDM systems are introduced. A new effective channel estimation algorithm is proposed as well and improves the performance of the systems greatly. In addition, OFDM systems are very sensitive to the effect of timing error, to obtain a better channel estimation performance, the choice of synchronization algorithm is important. The synchronization approach adopted based on IEEE802.11a standard is studied and the performance of symbol timing, frequency offset and channel estimation simultaneously is analysis. The computer simulation shows that the veracity of symbol timing has a great effect on the performance of synchronization and channel estimation simultaneously and the performance is close to ideal synchronization when the timing error in the two sample points.