On Asymptotic Efficiency for Asynchronous CDMA

We consider asynchronous CDMA systems and analyze their performances in terms of asymptotic efficiency when linear receivers are employed and the system becomes overloaded. We show that in such systems, differently from synchronous systems, linear detectors can be asymptotically efficient and, specifically, that the MMSE detector is asymptotically efficient with probabilty. Simulations confirm that it is better to be asynchronous than synchronous and even under heavy overloading the MMSE receiver is still asymptotically efficient.