  This paper focuses on the issue of energy efficiency in wireless data
networks through a game theoretic approach. The case considered is that in
which each user is allowed to vary its transmit power, spreading code, and
uplink receiver in order to maximize its own utility, which is here defined as
the ratio of data throughput to transmit power. In particular, the case in
which linear multiuser detectors are employed at the receiver is treated first,
and, then, the more challenging case in which non-linear decision feedback
multiuser receivers are adopted is addressed. It is shown that, for both
receivers, the problem at hand of utility maximization can be regarded as a
non-cooperative game, and it is proved that a unique Nash equilibrium point
exists. Simulation results show that significant performance gains can be
obtained through both non-linear processing and spreading code optimization; in
particular, for systems with a number of users not larger than the processing
gain, remarkable gains come from spreading code optimization, while, for
overloaded systems, the largest gainscome from the use of non-linear
processing. In every case, however, the non-cooperative games proposed here are
shown to outperform competing alternatives.
