Channel Estimation Using Data and Pilots for a Coordinated DSL System

Coordination between users in the downstream direction has been recently proposed in order to combat the effects of crosstalk in DSL transmissions. A high level of coordination involves a fine knowledge of the crosstalk coupling between lines and an imperfect channel estimation has an influence on the performance of the system. Classical estimation techniques that use training symbols have good performance with a low computational cost, but induce a loss in terms of bandwidth efficiency. In addition, the management of DSL lines should consider the insertion of a new user in a coordinated transmission. In this paper, we propose a crosstalk estimation method for including a new user without disrupting the transmission of the already coordinated users. The resulting channel estimation error is then analyzed as well as the impact on the expected data throughputs.