Joint channel estimation and equalization in multicarrier modulation system using cyclic prefix

Multicarrier modulation (MCM) is a promising technique for high rate data transmission. A one-tap equalizer is an essential part of the MCM system and the channel estimation is needed to get the coefficient of the equalizer, Lack of correct channel estimation may cause significant performance degradation. We propose to use the cyclic prefix to estimate the channel for the MCM system. We found that the cyclic prefix originally used solely to guarantee the optimality of modulation using discrete Fourier transform (DFT) can be viewed as a source of channel information. Based on this observation, we propose a joint channel estimation and equalization algorithm using the cyclic prefix. Our simulations show that the algorithm can adaptively track the variation of a moderately time varying channel and has about 1-2dB gain over the system using the channel estimation obtained by the conventional training schemes. up. Then, this channel estimate is used through the entire communication. If the channel changes, retraining is required to track the variation. Recently some research has been done on channel estimation and tracking in wireless communications. A minimum mean square error estimation algorithm is proposed in [SI. In this paper we propose a new channel estimation scheme that can track the change of the channel parameters without retraining. Usually a cyclic prefix or a guarding period is added between two symbols in MCM system in order to reduce the intersymbol interference (ISI). We propose to use the cyclic prefix, which is normally discarded, for channel estimation and equalization. We observed that the prefix actually provides a constantly sent training sequence if accurate transmit signal can be recovered by the conventional MCM systems. A joint channel estimation and equalization algorithm using the cyclic prefix is proposed based on this observation. Simulations were performed under the asymmetric digital subscriber line(ADSL) environment to show the effectiveness of the algorithm.