This is a Presidential Young Investigator award in the area of communication theory. Dr. Verdu's work involves the application of probability and random processes to the analysis of the performance limits of information transmission through noisy communication channels, including multiple-access channels. A common strategy for sharing a communication channel is to let each user modulate a distint assigned waveform without requiring a multiple-access protocol to coordinate transmission periods with the other transmitters. From both the practical and theroetical viewpoints, the main object of interest is the asynchronous Gaussian multiple-access channel where the users transmit simultaneously and independently without maintaining common timing. The objectives of this research are the analysis and design of multiuser demondulators and the derivation of the main performance limits of the channel, assessed in terms of the minimum bit-error-rate and the region of informaiton rates at which reliable communication is possible. Also under investigation is the analysis of random-access protocols for channels that, unlike conventional collision channels, allow the reception of several simultaneous transmissions.
