Multi-user communication with multiple symbol rates

Multi-user communication scenarios, have almost exclusively focussed on the situation in which all users share a common symbol rate 1/T. However, future multi-media services will require that users with different (and possibly time-varying) data rates share a common transmission channel. We consider the problem of optimizing a multi-user receiver when the users transmit with different symbol rates. The problem of optimizing the transmitter pulse shaping filters for each user assuming different transmitted symbol rates is also considered. We assume the minimum mean squared error (MMSE) performance criteria