Symbol Time Synchronization Based on SINR Maximization for OFDM

Abstract

This work presents a symbol time (ST) synchroniza- tion algorithm for orthogonal frequency-division multiplexing systems based on a metric of signal-to-interference-and-noise ratio (SINR) which drops drastically with the increasing ST error. The ST is intuitively estimated by maximizing the SINR metric that exploits the correlation results of the separated-by-N samples. Unlike most existing techniques considering only AWGN or time-invariant multipath channels, the proposed maximum-SINR (MSINR) technique considers the time-variant multipath chan- nels. Compared with conventional techniques, the proposed MSINR technique is less sensitive to the carrier frequency offset and doubly-selective channel effects. knowledge of the Doppler frequency shift which is hard to accurately obtain in practice. Unlike previous works that mainly consider only AWGN or static channel conditions, this letter deals with the ST syn- chronization by maximizing a SINR metric under time-variant multipath channels. The SINR metric exploits the correlation results of the separated-by-N samples. Besides, the knowledge of the Doppler frequency shift is not required for the proposed maximum-SINR (MSINR) technique. In contrast to conven- tional CP-based algorithms which are sensitive to multipath channels, the proposed MSINR technique can effectively re- duce the ST synchronization error even in time-variant multi- path channels. However, the MSINR technique relies on the information of the channel delay spread; therefore, it is further modified to a more practical algorithm which is independent of the channel delay spread. In addition, the modified MSINR algorithm can identify the complete range of ISI-free region available in an OFDM symbol which is another advantage of the modified MSINR algorithm. This capability can be used to improve the BER performance of the system by adjusting the frequency-domain interpolation filter bandwidth. Moreover, the proposed MSINR technique is shown to be insensitive to the carrier frequency offset (CFO).