Multi-BS MIMO cooperation: Challenges and practical solutions in 4G systems

Various multiple-input multiple-output techniques have been introduced to improve performance of next-generation systems. In single-cell environments, closed-loop MIMO schemes increase the system capacity as well as cell coverage. In cellular networks where interference coming from other cells is usually a dominant factor, several multiple-base-station cooperation schemes have been introduced to mitigate the intercell interference. In this article, we first provide an overview of scenarios and technology categories for multi-BS MIMO cooperation schemes. Next we introduce closed-loop multicell MIMO techniques adopted in IEEE 802.16m, which do not require data forwarding among different base stations. In particular, this article explains the overall operations which minimize overhead. We also present simulation results that confirm the efficiency of the presented interference mitigation method.