Effective optimisation method for channel shortening in OFDM systems

In OFDM systems, a pre-filter can be used to shorten the channel impulse response when the order of the impulse response is longer than the length of the cyclic prefix (CP) of the system. The authors propose an effective optimisation method for determining the coefficients of the channel-shortening pre-filter (CSP). This method is designed in the time domain completely and it does not require the channel length to be subject to any constraint. It is optimum in the sense that it maximises the signal-to-interference-plus-noise ratio (SINR) of the pre-filter output. Compared with existing methods, the proposed method takes into account the effect of noise, thereby making the optimisation criterion more accurate and allowing the prefilter developed to not only mitigate intersymbol interference (ISI) but also suppress noise effectively. Computer simulation results show that the proposed method outperforms some existing methods.