Using more channels can be detrimental to the global performance in interference networks

We study distributed interference networks in which the transmitting-receiving pairs (or users) can communicate over several orthogonal channels. The network is said to be decisionwise distributed because each transmitter is assumed to choose the way it spreads its power over the available channels to maximize its individual rate. The main contribution of this paper is to prove that, depending on the network parameters, allowing every transmitter to use several channels simultaneously instead of a single one may lead to a global performance degradation in terms of the sum-rate at Nash equilibrium. In distributed networks, the Nash equilibria have the potential to be implemented with local knowledge and by low-complexity iterative or learning processes. Performance degradation is typically observed when the signal-to-noise ratio (SNR) is sufficiently high. The existence of such scenarios is proved analytically for networks composed of arbitrary number of users and channels and for large networks (of many users). Simulations confirm our analytical results in the low and high SNR regimes but also illustrate this phenomenon for intermediate SNR values.