Channel estimation based on diagonal pilot in OFDM systems

In PSAM (pilot symbol assisted modulation) of OFDM systems, channel is often estimated by training sequences or aid of pilots. The performance of channel estimation varies with different pilot patterns (i.e. the number and allocation of pilots). According to the Nyquist's Theory, the number of pilot is obtained by the channel parameters. Based on the rule of cross-correlation, the number of multipath and the maximal time delay can be deduced. However, with the same number of pilots, different pilot allocation can impact the estimated result greatly. This paper aims at exploiting an optimal pilot allocation pattern for OFDM system. Different from the existing pilot patterns, this paper proposes a diagonal pilot allocation pattern, which is optimal in the frequency selective channel. Simulation results demonstrate that the proposed scheme is superior to the equal-space pilot allocation pattern, and it can improve the spectral efficiency more than the 802.11 protocol does by a bit loss of performance.