Adaptive resource allocation in multiuser FDD-DMT systems

The performance of multiuser digital subscriber line (DSL) systems is constrained by crosstalk noise. This becomes especially noticeable in DSL systems that use high frequencies as in very high speed DSL (VDSL), since the crosstalk increases with frequency. To minimize the performance losses due to the crosstalk the users should coordinate and optimize their spectra with the aim of jointly maximizing the bit rates of all users. However, the multiuser DSL environment is modelled as a Gaussian interference channel and the rate region for this channel model is still an unsolved problem in information theory. This problem, for multiuser frequency division duplex discrete multi-tone (FDD-DMT) systems, is solved in a suboptimal way by our proposed Normalized-Rate Iterative Algorithm (NRIA). The NRIA determines optimized down- and upstream subcarrier allocations for the bundle and implicitly performs power control and power allocation for all users. In this paper we show, by simulation, that this algorithm achieves a significant performance improvement over existing standardized upstream power back-off (UPBO) and spectra plans in VDSL.