DSM in practice: iterative water-filling implemented on ADSL modems

Dynamic spectrum management (DSM) is a new technique for multiuser power allocation and/or detection in digital subscriber line (DSL) networks. In DSM, transmit spectra are adapted based on the direct and crosstalk channels seen by the modems within a network. This allows binder bit rate performance maximisation. At the Alcatel Research and Innovation labs, we have recently developed a DSM testbed which allows the performance of DSM algorithms to be evaluated in practice. The paper describes the development of this DSM testbed. With this testbed we have evaluated the performance of a DSM algorithm known as iterative water-filling. It has been demonstrated that iterative water-filling can yield data-rate gains of up to 500% in the real world. Practical issues on the implementation of iterative water-filling are also discussed.