Recently, the ability of anti-fading measures to reduce the outage which occurs on digital microwave radio links has been the subject of considerable study. Ideal and nonideal adaptive equalization in both the time and frequency domain have been evaluated for nondiversity reception using various performance criteria. Ideal adaptive equalization and space diversity reception have been considered using a recently published model of multipath fading on space diversity radio channels. In this paper, we determine the outage of 16-QAM and 64-QAM digital radio systems using adaptive slope equalization, finite-tap decision feedback equalization, and switched space diversity reception. The outage is evaluated by computing the probability of occurrence of those channel realizations which cause the bit error rate to exceed a critical value. The dependence of the outage prediction on the equalization method and the outage defining criterion is investigated by also considering ideal adaptive equalization and a signal-to-distortion ratio, respectively.

Certain measures of information between a state process and an observation process and between a state process and an estimate of the state process are considered. The observations are assumed to have sample paths which are almost surely continuous. The calculus of martingales and probability measure transformations are used to determine representations of the observation process and the state estimate on different probability spaces obtained by a change in the sub-o-algebra and/or the probability measure. The Radon-Nikodym derivatives required to calculate the information theoretic quantities are obtained from these representations.

The receiver sensitivity of a moderate bit rate optical fiber communication link is investigated. The effect of both power conversion among the guided modes of the fiber and power loss to the radiation field from the guided modes is examined. Three different receiver filter designs are considered; a zero-forcing equalization procedure and two filters which do not compensate for the pulse dispersion introduced by the optical fiber channel. The degree of sophistication required in the detection process is a function of the mode coupling and attenuation parameters and the numerical results provide useful quantitative information for this aspect of system design. In particular, the channel parameter values for which processing techniques are required to compensate for pulse dispersion can be obtained from the results.