Competitive spectrum sharing in symmetric fading channel with incomplete information

This paper considerers a symmetric Gaussian interference game with incomplete information where players choose between frequency division multiplexing (FDM) and full spread (FS) of their transmit power. Previously, the only known Nash equilibrium point for this game was the point where players mutually choose FS and interfere with each other. This point may lead to undesirable outcome from global network point of view and even for each user individually. It happens when mutual FDM is better to both users than mutual FS. In this paper, we show that if users agree to use different subbands in the case of FDM, then there exist a non pure-FS Nash equilibrium point, i.e. an equilibrium point where players choose FDM for some channel realizations and FS for the others. This Nash equilibrium point increases each user's throughput and therefore improves the spectrum utilization. Furthermore, to reach this point, the only instantaneous channel state information (CSI) required by each user is its interference-to-signal ratio.