信道时延条件下的CoMP系统有限反馈比特分配

摘要

研究了非完全信道状态信息(CSI)条件下用户终端对基站的反馈比特数问题,在考虑有限反馈和信道时延的条件下,得出系统速率损失近似上界与反馈比特数的关系表达式,基于该表达式提出一种新的反馈比特分配方案.该方案通过对系统速率损失近似上界求导处理,得到使得速率损失近似上界达到最小的最佳反馈比特数.该方案可以有效地降低有限反馈对系统速率的影响,系统速率比传统的比特均分算法高,复杂度比穷举法低.%Cellular systems are known as interference-limited in nature.In order to meet this challenge,Coordinated Multi-Point (CoMP) transmission reception is proposed in LTE-Advanced.One of the key strategies to mitigate interference in CoMP is to design the precoding.With the perfect Channel State Information (CSI) in cooperative multi-cell systems,the intra-cell and inter-cell interference can be mitigated by Block Diagonalization (BD) precoding.However,the CSI in practical systems is imperfect,so bits allocation under imperfect SCI is considered.Closed-form expressions of the upper bound of system rate loss and the number of feedback bits are derived with limited feedback and channel delay.A new bits allocation strategy is developed based on this expression,which can minimize the rate loss by making the partial derivative of the upper bound of rate lass equal to zero.The proposed bits allocation algorithm yields higher sum-rates than equal-bits allocation algorithm,and it has lower complexity than exhaustive algorithm.