Research On The Feedback Bit Allocation And User Scheduling Algorithm In CoMP System

Coordinated multi-point (CoMP) technology is recognized as one of the most important key technologies in LTE-A due to its excellent ability to resist inter-cell interference. In real CoMP system, various cooperation base stations get local channel state information (CSI)through the instantaneous channel information that feedback by users in the cell. So the error produced by the limited feedback will influence the system performance seriously, which must be considered. This paper research limited feedback bit allocation and user scheduling algorithm based down link transmission model of CoMP Joint Processing (JP) system taking limited feedback and channel delay into account.In order to reduce the incomplete CSI impact to the system performance, a limited feedback bit allocation algorithm based on differential evolution is proposed in this paper. The algorithm optimizes the feedback bits allocation by using differential evolution algorithm to decrease the loss of system rate maximally that produced by the limited feedback. Simulation results show that when the total number of feedback bits remain the same, the algorithm proposed in this paper not only maximization the total transfer rate, as the same as the exhaustive bit allocation algorithm, but also has smaller complexity and easier to the realize than the exhaustive bit allocation algorithm.In the real system, the CSI is not completely known, so we must consider the effect to the real system design, which comes from limited feedback and channel delay. In order to solve this problem, this paper studies CoMP-JP feedback bit allocation problem under the condition of limited feedback and channel delay. We obtain the theoretical value of the imperfect CSI system rate loss and the best value of feedback bits needs feedback to the service station and the adjacent base station.On this basis this paper research user scheduling algorithm in CoMP-JP down link system. And contrastive analysis three user scheduling algorithms which are based on the rule of system capacity maximization, the rule of user channel correlation factor minimization and the rule of user fairness respectively.Simulation results show that in the three improved algorithm discussed in this paper, the user scheduling algorithm based on rule of system capacity maximization has the best performance, while the user scheduling algorithm based on rule of user channel correlation factor minimization has the best channel correlation between users.