Knowledge of the probability density function (pdf) of intersymbol interference (ISI) can be used in the computation of system error probabilities and to help identify the cause of the errors. Exact computation of the probability density is only practicable in a few special cases. Several algorithms exist for computing approximate pdfs of ISI but these only work with certain signal constellations and transmitted symbols that are mutually independent or coded by partial response. This paper considers an algorithm for the computation of ISI pdfs for trellis-coded modulation with general 1D and 2D constellations. The results suggest that symbol dependencies introduced into the transmitted signal by symmetric trellis-codes have negligible effect on the pdf of the ISI. Although the ideas presented are general in nature, examples are given for ISI pdfs on a line-of-sight radio channel.>

The performance of trellis-coded modulation (TCM) on additive white Gaussian noise channels is well understood, and tight analytical bounds exist on the probability of the Viterbi decoder making a decision error. When a channel is also time-dispersive, the performance of TCM systems has been studied mainly by simulation. However, simulation is limited to symbol error probabilities greater than 10/sup -6/ and is not a particularly useful tool for designing codes. Tight analytical bounds on the error probability of TCM on time-dispersive channels are required for a more thorough study of performance. Moreover, the design of good codes and optimum metrics for time-dispersive channels requires tight analytical bounds. In this paper we derive analytical upper bounds, which, although requiring numerical techniques for tractable evaluation, are tight for a wide range of time-dispersive channel conditions. The bounds are based on a union bound of error events that leads to a summation of pairwise error probabilities, which are themselves upper bounded.>

The paper analyzes and quantifies the performance of a space diversity combining receiver operating in a digital cellular radio environment with quaternary phase shift keying (QPSK), frequency-selective Rayleigh multipath fading, and co-channel interference (CCI). The receiver has an infinite length filter in each branch of the diversity combiner, and the filters are jointly optimized according to the minimum mean-square error (MMSE) criterion. The link bit-error-rate (BER) is accurately estimated using Metzger's algorithm (Metzger, 1987) which approximates the probability density function of the combined intersymbol interference (ISI) and CCI. The authors present numerical performance results showing the influence of the diversity order, the number of dominant co-channel interferers, the multipath channel's delay spectrum, and the root-mean square delay spread. The results show that, under certain conditions, the optimum linear receiver can almost completely eliminate all ISI and dominant CCI while providing near-optimum noise filtering.>

A study of minimum mean-square error (MMSE) diversity combining for wide-band digital cellular radio, designed to combat intersymbol interference (ISI) caused by frequency selective fading is outlined. The systems analyzed use binary phase-shift keying (BPSK), quarternary phase-shift keying (QPSK) or 16-level quadrature amplitude modulation (16-QAM) with cosine rolloff spectral shaping, and space diversity with selection, maximal ratio or MMSE combining. A set of performance curves is presented for selected combining schemes showing the influence of the following system parameters: the diversity order (1 to 4); the cosine rolloff factor; the power delay spectrum (with its associated delay spread); the signal-to-interference ratio; and the number of modulation levels (2, 4 and 16).>

The application of trellis-coded modulation to reducing the effects of residual interference levels encountered on multipath fading channels after adaptive equalization in high capacity digital microwave radio systems is investigated. Simulations used to derive error performance curves and outage probabilities are discussed. The results indicate that trellis-coded modulation offers performance improvements in addition to those offered by adaptive equalization.>