Abstract:

Consider the spectrum management problem for a multiuser communication system in a frequency selective environment whereby users share a common spectrum and can interfere with each other. Assuming Gaussian signaling and no interference cancellation, we study optimal spectrum sharing strategies for the maximization of sum rates under separate power constraints of individual users. Since the sum rate function is non-concave in terms of the users' power allocations, there can be multiple local maxima for the sum rate maximization problem in general. In this work, we show that, if the pairwise product of the crosstalk coefficients are sufficiently large, then the optimal spectrum sharing strategy is frequency division multiplexing (FDM). For scenarios with moderate interference, FDM is still locally optimal when each user has sufficiently large power budget. Furthermore, we establish the NP-hardness for the problem of finding the optimal FDM spectrum sharing strategy, and propose greedy spectrum allocation algorithms that can approximately maximize sum rates. Numerical results indicate that these algorithms are efficient and can achieve substantially larger sum rates than the existing Iterative Waterfilling solutions, either in an interference- rich environment or when the users' power budgets are sufficiently high.

This is a joint work with Shunsuke Hayashi.