Multiuser DMT: a multiple access modulation scheme

We propose a multiuser DMT scheme for use in a frequency dispersive multiple access channel. We formulate the problem as an optimization problem for maximizing the rate-sum or a weighted sum of the rates. We establish the rate-sum maximizing solution which is a multiuser waterfilling scheme over the DMT tones. We propose a multiuser bit-loading algorithm which finds the rate-maximizing solution in a finite number of steps. We study coding strategies and examine some implementation issues. Finally we present some numerical results obtained by using this scheme and we draw some conclusions from these results