Multi-user coordinated multi-point transmission with different delays

To decrease the multi-user interferences caused by the different delays from cooperative base stations to certain users in the downlink of coordinated multi-point (CoMP) systems, a delay compensation method based on the maximum signal-to-leakage and noise ratio criterion is proposed. Firstly, according to the feedback of channel state information and transmission delay information, the compensation amount for each user is optimized to obtain a closed form solution based on the maximum signal-to-leakage and noise ratio criterion. Then, the delay compensation for each user is realized by phase rotation of transmitted signals at the base station side in the frequency domain. Although it is derived by approximation at high signal-to-interference and noise ratio, the proposed method can achieve almost optimal delay compensation because of taking into account both the user's signal-to-noise ratio and the interference to other users. The numerical simulation results show that this method can effectively compensate the different delays at various signal-to-noise ratios and improve the system sum data rate close to that of the ideal scenario without delay differences. Therefore, it is suitable for practical multi-user CoMP systems.