Abstract: 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.

Key words: communication technology, coordinated multi-point, limited feedback, channel delay, bits allocation, block diagonalization precoding