The Research On The Cooperating Nodes Selection In CoMP Of LTE-advanced System

Co MP of the LTE-Advanced system has solved the problem about the loss at high frequency, poor coverage and the bad performance of cell edge users. In the process of Co MP cooperation transmission, how to choose cooperating nodes has become a very important problem. If there are too many cooperating nodes, the interaction of channel state information will be overmuch, which will increase the system load. If there are too few cooperating nodes, it won’t bring cooperation gain. Reasonable choice of cooperating nodes can bring SINR ascension of cell edge user, and improve the cell edge spectrum utilization efficiency, increase the system throughput and improve the user experience, etc.The traditional cooperating nodes selection method includes static cooperating nodes selection method and the dynamic cooperating nodes selection method. Static cooperating nodes selection method set fixed cooperating set in the period of the network planning, and so could not adjust as the user moves. At the same time due to the change of the channel state, the original cooperating nodes may have not meet the requirements of cooperating transmission, so the static cooperating nodes selection method is lack of flexibility. And dynamic cooperating nodes selection method needs to master the channel information of nodes attached to the users all around, and interact. Because of large numbers of channel state information interaction, the load and control costs of the system will increase, and due to the rapid change of channel state, the cooperating set may update frequently, which makes high complexity.In view of the above disadvantages, according to the order statistics, this paper proposes a half static cooperating nodes selection method based on decision threshold: First of all, we preset all the adjacent nodes of user serving e Node B for the candidate set. Second, the control center of the network calculates the threshold. Again, the threshold is compared with the channel state between the user to each node. If the threshold is too large and all the nodes don’t send data, this will lower the threshold; If there are multiple nodes to transmit data, then the threshold will be improved. Finally, the optimal node will be selected.After using this algorithm, each node need not interactive channel state information frequently. Only by comparing the threshold calculated by the transmission node with the channel state information of each node, the optimal node can be chose. So we solve the problem that the original algorithm needs frequent and large amount of exchange of the channel state information, the spectrum resource is also saved.This paper uses the typical scenario defined by 3GPP, using matlab to simulate the decline and the antenna gain in wireless environment also the user distribution, etc. By comparing the three algorithms on SINR, spectral efficiency of the edge users, channel capacity, bit error rate performance, we draw the conclusion that this algorithm is better than the other two algorithms.