Power optimization of source encoding and radio transmission in multiuser CDMA systems

We investigate the power consumed by two mobile terminals transmitting compressed source signals to a base station in a CDMA cellular system. The aim is to minimize total power consumption at the terminals by simultaneously adjusting the complexity of source compression and the transmitter power. We find that in general the complexity of source compression should increase with increasing distance between a terminal and the base station. However, the exact configuration of compression and transmitter power depends on the interaction of the two terminals. The optimum operating points of the two terminals are contained in a pair of nonlinear equations. We use the example of a transform coder processing signals from a Gauss-Markov source to explore the advantages of an adaptive system over a system with fixed compression. The analysis can be applied to a variety of source coders and be extended to a system with more than two users per cell.