Lattice implementation of adaptive channel shortening in multicarrier transmission over IIR channels

Abstract

Time-domain equalization is crucial in reducing channel dispersion and canceling interference in multicarrier systems. The equalizer is a finite impulse response (FIR) filter with the purpose that the delay spread of the combined channel-plus-equalizer IR is not longer than the cyclic prefix length. In this paper, a specific framework of long FIR channel-shortening problem is studied. In fact, approximated by a stable pole-zero model, we show that the channel transfer function poles introduce interference. Hence, to cancel bad poles, we propose the use of lattice structure to implement the channel shortener which places their zeros very close to critical channel poles and cancels them out. For low complexity implementation, we adopt adaptive algorithms to design the lattice channel shorteners. This paper analyzes the lattice structure performances of two blind adaptive channel shorteners: sum-squared autocorrelation minimization and multicarrier equalization by restoration of redundancy algorithms. The proposed implementation performances are given in terms of bit rate, and the simulation results are studied in the context of asymmetric digital subscriber line system.