Interference cancellation and suppression in asynchronous cooperating base station systems

We consider cooperating base station systems where the users are not aligned in time and frequency to the core network as it is actually desired for coherent joint signal processing. As it is widely known, time and frequency offsets can cause inter-symbol as well as inter-carrier interference in OFDM systems which leads to a reduced transmission performance. In this paper we investigate uplink joint detection algorithms which, in addition to multi-user interference cancellation, reduce the asynchronous interference by using iterative interference cancellation as well as mitigating the additional interference by exploiting spatial diversity. The structure of the asynchronous interference in frequency domain can be exploited to derive algorithms with scalable complexity. As will be seen, particularly the interference suppression algorithm provides very good performance results with only a moderate complexity increase.