DMT MIMO IC Rate Maximization in DSL With Combined Signal and Spectrum Coordination

Theoretical research has demonstrated that the achievable gains in data rate with dynamic spectrum management, i.e., signal coordination or spectrum coordination, are substantial for digital subscriber line (DSL) networks. Work on these two fronts has progressed steadily and, more often than not, independently. In this paper, we combine the two types of coordination for a mixed DSL scenario, in which some of the infrastructure required for full two-sided signal coordination is available, but not all. This scenario, which is referred to as the discrete multitone multiple-input, multiple-output interference channel (DMT MIMO IC), consists of multiple interfering users, each operating a distinct subset of DSL lines as a MIMO system. Coordination is done both on the signal level (with per user MIMO techniques) and on the spectrum level (with multi-user power allocation). We propose two algorithms for the DMT MIMO IC weighted rate maximization problem. In the first algorithm, we profit from recent work showing the close relation between the weighted rate sum maximization problem and the weighted MMSE minimization problem. We show that with a simple extension, we can adapt the previous work to the scenario of interest. In the second algorithm, the signal and spectrum coordination parts are solved separately. For the signal coordination part, we obtain multiple independent single tone MIMO IC's, which allows us to leverage on the previous work on the topic. For the spectrum coordination part, one of the interesting results of our analysis is a generalization of the distributed spectrum balancing (DSB) power allocation formula for the DMT MIMO IC scenario. Simulation results demonstrate that both algorithms obtain significant gains when compared to pure spectrum coordination algorithms.