Soft Inter-cell Interference Cancellation Technology In C-RAN System

3GPP has proposed Cloud-Radio Access Network in LTE Release11version as anaccess network solution in next generation communication system. It mixes centralizeprocessing, cloud-computation and distributed antenna system together, which have greatpotential to improve the conditions of power comsumption, system coverage andinterference mitigation. Meanwhile, the radio access network, including C-RAN, isinterference-limited system. They are more susceptible for the inter-cell interference.Traditional inter-cell interference mitigation scheme is diveded into two aspect. One isinter-cell interference coordination, ICIC. The other is inter-cell interference cancellation,IIC. The ICIC scheme can avoid the inter-cell interferences through the resources allactioncoordination. But it sacrifices the frequency resource efficiency. In contrast, IIC can makethe interference reduced, with the high frequency efficiency. But it has exponentialcomplexity.The thesis analyze the characteristics of C-RAN network, whose centralizedprocessing ability and virtual baseband unit grouping technology can provide hardwarecondition for IIC scheme. And in order to prevent the high complexity of idealinterference detector, we propose an iterative soft inter-cell interference cancellationscheme based on multi-user detection, who has low complexity and high estimationaccuracy. We use poster-likelihood function to calculate the MMSE estimation ofinterference signals from other cells. And through the iterative processing, we make thesoft information more certain. To avoid the appearance of error spreading, we process thesoft information resset based on the variances of soft estimation of interferences. Throughthe simulation, we find the new scheme can repress the inter-cell interference well, and agood performance in error spreading prevention.