In this paper we extend the analysis of the performance of the APSK modulation, often limited to the AWGN channel, by considering its application in wireless tactical scenarios for land mobile systems. First, the implications of reduced PAPR on the total degradation are explored, taking into account the non-linear effects due to HPAs and the need to use adaptive pre-distortion. Then, the bit error rate performance is assessed by simulation, for some typical multipath scenarios with decision feedback equalization, also including the presence of turbo channel coding.

Residual carrier, balance, and quadrature error imperfections that are normally present in phase/quadrature modulators limit the use of direct modulation techniques in some applications. The classical precompensation techniques are revised and an adaptive solution proposed that improves performance by some order of magnitude.

This paper presents a reduced complexity Viterbi algorithm for use as sequence estimator for linear intersymbol interference channels with coarsely located coefficients. In particular, the complexity does not depend on the channel impulse response length but only on the number of nonzero coefficients. No approximations are used in the algorithm. We consider a multipath environment producing time spreads.

A multipath channel in television broadcasting can result in overlaid images (ghosts) or distorted noisy images on the display and is a major problem to be overcome. We propose a method to equalize the multipath distortion for the case of digital transmission and nonminimum phase channels. The method employs noncausal allpass recursive filters operating in reversed time followed by a decision feedback equalizer (DFE). It does not require the computation of zeros of the channel impulse response, and the channel noise level is not enhanced. The equalized impulse response is such that, in most cases, the first nonnegligible sample has the largest magnitude, as appropriate for DFE decoders. Computer simulation results verifying the proposed approach are included.>