Research On Coordinated Multi-Point Transmission(CoMP) Technology Based On C-RAN Framework

With the continuous development of wireless communication, we are moving forward in the era of mobile internet. How to meet the requirements of high speed, low interference, etc., has become a severe test for the next generation of wireless communication network. LTE-A introduces the Coordinated Multi-Point transmission/reception(CoMP) technology. CoMP can inhibit cell interference and improve the system capacity by employing Joint Processing and Coordinated Beamforming(CB) which can improve the quality of the received signal and spectrum effectiveness. Beamforming is a kind of downlink transmission technology. Each base station transmits a shaped beam to reduce the interference of users in the overlapping area of each base station by sharing channel information. Beamforming is simple and efficient, and it has high research value.In this paper, the beamforming technique in CoMP is studied. First, in the single cell case, that is not to take into account the inter cell interference, this paper realizes the beamforming algorithm based on zero forcing, the beamforming algorithm based on singular value decomposition of channel matrix, and the eigenvalue decomposition beamforming algorithm based on the maximum signal to noise ratio. Simulation results show that these three algorithms can reduce the interference and improve the system performance. But in different channel conditions, there are some differences between the three algorithms.Next, cooperative beamforming technique in the multi cell is studied. In the case of cooperative base station known user channel state information(CSI), the beamforming algorithm based on the maximum signal to noise ratio and the cooperative beamforming algorithm based on zero forcing are studied. The zero forcing algorithm can eliminate the interference of the adjacent cell edge users at the transmitter, but the number of transmit antennas is limited. The algorithm based on the maximum signal to noise ratio has overcome this limitation, and is easy to be solved. Simulation results show that compared with the non-cooperative transmission, the two algorithms can achieve good performance. When the number of transmit antennas in the base station is not satisfied with the constraint conditions of zero forcing algorithm, the algorithm based on the maximum signal to noise ratio is better than it.