Source Separation of Asynchronous OFDM Signals using Superimposed Training

In multi-user orthogonal frequency division multiplexing (OFDM) systems, an asynchronous interferer is defined as a signal whose cyclic prefix (CP) does not align with the desired user CP. Such ad-hoc multi-user OFDM systems are considered and an algorithm to perform blind space-time source separation is presented. In this paper we consider a scheme where a periodic sequence is added to the transmitted OFDM signal to be able to identify it. The periodic sequence has a cyclostationary property and can be used to estimate the channel and to separate the interfering users from the desired user signals.