JOINT TRANSMITTER-RECEIVER OPTIMIZATION IN SYNCHRONOUS MULTIUSER COMMUNICATIONS OVER MULTIPATH CHANNELS

Transmitter optimization, in addition to receiver optimization, contri butes significantly to efficient interference suppression in multiple access and multipath channels, The system design in this paper is base d on the joint optimization of the transmitter and the receiver in a s ynchronous multiuser channel characterized by multipath propagation, J oint optimization is represented by a linear transformation of the tra nsmitted signals at the transmitter and a linear transformation of rec eived signals at each receiving site that minimize the effect of multi ple access and multipath interference, The minimum mean squared error between the true bit value and its estimate at the output of the recei ver is taken as the cost function, subject to average and peak transmi t power constraints, It is shown that joint transmitter-receiver optim ization outperforms significantly either transmitter optimization or r eceiver-based techniques, The crucial assumption, in the case of multi path channels, is that the transmitter knows the multipath characteris tics of all channels and that the channel dynamics are sufficiently sl ow so that multipath profiles remain essentially constant over a block of preceded bits, The practical applications can be found in indoor a nd cellular communications, satellite communications, or military comm unications where nonorthogonal signature waveforms are employed.