Transmitter optimization, widely-linear detection, and power control for energy-efficient networks: A game-theoretic approach

The issue of cross-layer spreading code optimization, widely-linear receiver choice and transmit power control for non-cooperative energy-efficiency maximization in CDMA-based wireless data networks is considered in this paper. While previous work in this area has focused on a simple real signal model, in this paper a baseband complex representation of the data is used, so as to properly take into account the I and Q components of the received signal. For the case in which the received signal is improper, a widely-linear reception structure, processing separately the data and their complex conjugates, is considered. Several non-cooperative games are considered, all of which are shown to admit Nash equilibria. Interestingly, it is found that spreading code optimization coupled with widely-linear filtering permits supporting, with no multiuser interference, a number of users that is twice the processing gain. Numerical results corroborate the validity of the theoretical analysis, and show that widely-linear filtering in the presence of improper data brings remarkable performance improvements with respect to conventional linear receivers.