Research On The Technologies Of Enhanced Coordinated Multi-point Communication In Mobile Communication Systems

In a wireless communication system, a great amount of nodes that cooperatewith each other can improve the transmission rate and quality of the cell edgeusers, expand coverage and improve transmission reliability. In a single-cellsystem, affected by path fading and other factors, a user located at the cell edgereceives great amount of interference from the adjacent cells, thus the signal tointerference noise ratio of the receiver is bad. However, using coordinatedmulti-point communication system can achieve interference cancellation andsignal enhancement. In a realistic system, due to the non-ideality of the backhaul,many enhanced techniques should be further considered in the practicalapplication of the technology.In this paper, I give an overview of the research status of multi-point wirelesscommunication system, mainly focus on the multi-point collaboration systemwith limited feedback, cell clustering and interference cancellation. Throughtheoretical study and simulation, this paper gives some effective ways toimprove system performance.I study the bit allocation technique in coordinated multi-point systems withlimited feedback. In conventional single cell communication systems, a userselects a base station as a serving base station. In order for the precoding design,the users are required to feedback the channel state information. In thecoordinated multi-point system, in addition to a service base station, a user alsohas one or more cooperative base stations to eliminate the interference.Allocating a limited number of feedback bits among different channels caneffectively improve the overall throughput of the system. On the other hand, thephysical characteristics of the users in different positions should also be takeninto consideration when allocating the feedback bits so that we can minimize the total transmission rate loss of the system.In this paper, we also study an effective cell clustering scheme in coordinatedmulti-point communication system. Besides the channel state information, basestations also need to exchange a large amount of transmission data. This kind ofcooperation requires an ideal backhaul which have unlimited capacity and withlow latency. With ideal backhaul support, coordinated multi-pointcommunication systems form a cooperative network of distributed networkMIMO system. The network MIMO system can be analogous to the single cellMIMO system. We give a cell clustering scheme based on utility function. Inthis scenario, we select the cell to from clusters based on the principle ofmaximum total rate. This scheme reduces the computational complexity of thesystem, while ensuring less reduction of data rate of the system.This paper also discusses a time domain interference cancellation techniquein a multi-cell system. In response to the rapidly growing demand for dataservice, in some areas with high user density, or at the edge of the macro-cell,some pico-cells are also deployed. The transmission power of the pico-cells islower. And together with traditional macro-cells, they form the heterogeneousnetworks (HetNets). In HetNets, we usually use cell range expansion (CRE) tooffload users to pico-cells. However, the users in the extended area suffer severeinterference from macro-cell. To solve this problem, the R10version of the3GPP organization proposed the Almost Blanked Subframe technique which isalso called eICIC. Based on the research status of eICIC, we propose a basestation selection and interference cancellation scheme in the time domain.Finally, we give a summary of the research on this topic and point out thedirection of coordinated multi-point system for further study.