ADAPTIVE RECEIVERS FOR DIGITAL SIGNALING OVER RANDOM OR UNKNOWN CHANNELS.
HARVARD UNIV CAMBRIDGE MASS GORDON MCKAY LAB
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The problem in digital communications treated herein can be stated as follows There is a transmitter which chooses and sends, in any signaling interval of duration T seconds, one of M possible signaling waveforms over a channel which is modeled as a linear filter and an impulse response that is unknown or randomly time-varying. The transmitted waveform is also corrupted by additive Gaussian noise. At the receiving point a receiver is to be designed which processes the received signal and decides with minimum probability of error which one of the M waveforms was transmitted in every signaling interval. Treated in detail is a channel which imparts an unknown or slowly and randomly time-varying gain and phase shift to the signal which is transmitted in each signaling interval. For this channel the receiver which minimizes the probability of error is specified and its performance is evaluated for binary orthogonal signaling and M-phase signaling. Basically, the receiver uses an estimate of the channel gain and phase shift in detecting the waveform received in each signaling interval. Furthermore, it is shown that in addition to detecting the transmitted information sequence, this receiver continuously estimates the channel gain and phase shift either from the information-bearing waveform or by means of a pilot waveform which is transmitted for the puprose of measuring the channel. The performance of the receiver is evaluated in terms of its probability of error for binary orthogonal signaling and M-phase signaling in the general context of Lth order diversity reception. For M-phase signaling we give the probabilities of a binary digit error and the probability of a character error. Author
- Radio Communications