One of the techniques that has been recently identified for dealing with multi-user interference in future communications systems is base station cooperation or joint processing. However, perfect multi-user interference cancellation with this technique demands severe synchronization requirements, perfect and global channel state information, and an increased backhaul and signaling overhead. In this paper, we consider a more realistic layout with the aim of mitigating the multi-user interference, where only local channel state information is available at the base stations. Due to synchronization inaccuracies and errors in the channel estimation, the system becomes partially asynchronous. In the downlink of WCDMA based systems, this asynchronism stands for the loss of the orthogonality of the spreading codes allocated to users and thus, for an increase in the multi-user interference level of the system. In this contribution, we propose a framework for mitigating the multi-user interference which builds in three main steps: definition of a cooperation area based on the channel characteristics, statistical modeling of the average multi-user interference power experienced by each user and a specific spreading code allocation scheme for users served with joint processing. This code allocation assigns spreading codes to users in such a way that minimum average cross-correlation between active users can be achieved. Interestingly, these steps can be