Research Of The Clustered Multi-cell Coordination In LTE-Advanced Systems

In order to meet the IMT-A system requirements proposed by ITU-R,3GPP started the research work of the LTE-Advanced systems and introduced a number of key technologies, aiming at supporting higher peak data rates, throughput and coverage with lower latency, and achieving better user experience, on the basis of backward compatible with LTE system. In the design of mobile communication systems, interference is one of the key challenges that have to be faced. The existence of interference has seriously restricted the reuse of system resources, such as time slot, frequency and code, and limits the spectral efficiency of the entire system. The inter-cell interference in LTE-Advanced system is so serious that the conventional interference management methods can’t solve the problem of low spectral efficiency of cell edge users well. Therefore, considering the CoMP (coordinated multi-point) technology, with which all the base station antennas are jointly used to reduce the inter-cell interference and improve the signal to noise ratio at the receivers. Thereby, the system throughput and spectral efficiency of cell edge users would be improved.The coordination among the base stations in multi-cell downlink system is studied. By clustering all the cells in the network, one cell only coordinates with the cell in the same cluster. Therefore, inter-cell interference could be suppressed through the coordination across the BTSs on the one hand; on the other hand, the system complexity and signaling overhead are reduced comparing with the network coordination. The contributions are presented as follow:(1) The coordination strategy consists of intra-cluster coordination and inter-cluster coordination. The main idea of intra-cluster coordination is that by pre-coding across BTSs within the same cluster, the inter-cell interference in it could be suppressed.(2) The inter-cluster coordination is used to suppress the interference for the users at the edge of neighboring clusters. The pre-coding technology of inter-cluster coordination could be the same with that of intra-cluster coordination. The key parameter of coordination distance is discussed to get a reasonable coordinated area, which could also make a compromise between system sum-rate and fairness.(3) Different multi-cell clustering schemes are analyzed including static clustering scheme and dynamic clustering schemes, based on which an optimized dynamic clustering scheme is proposed. The optimize scheme is not only proved to have better system sum-rate gain according to the simulation results, but also more flexible to adjust to different channel conditions.