Study On Interference Rejection Combining Technique For Massive MIMO Systems

Multiple-input multiple-output (MIMO) technology has been widely used in the fourth generation mobile communication standard LTE with its advantage to improve the system capacity and link reliability. With the popularity of smart terminals, wireless transmission rate demand is exponential growth, and the proportion of the system ener-gy consumption is increasing, and reducing energy consumption has become an im-portant aspect of the development of mobile communication. To this end, massive MIMO technology is proposed, which is mainly through the base station equipped with very large antenna arrays to solve the above problems. However, with the spectrum re-sources more and more scarce, the adjacent cells use the same frequency to form a cel-lular network, causing inter-cell interference, which is especially evident in the LTE network, and the inter-cell interference caused by the pilot contamination becomes more and more serious in the massive MIMO. Therefore, this paper focuses on the interfer-ence rejection combining (IRC) in traditional MIMO system and massive MIMO sys-tem.First, the thesis analyzes the performance of IRC based on the Minimum Mean Square error Estimation criterion on the uplink of the traditional multi cell multi user MIMO system in LTE and simulates the system performance of maximum ratio com-bining (MRC) and IRC. The results show that MRC has better performance than IRC when there is no interference. When there is interference, the interference will be seen as noise for MRC, so it can not good to suppress the interference and IRC separately considers the noise and the interference, can suppress the interference. Next, we study IRC which maximizes the received signal-to-interference-plus-noise on the uplink of Multi cell multi-user massive MIMO systems, the method exploits the correlation be-tween the channel estimates and interference. Then separately analyze the system per-formance of MRC, MMSE and IRC in the regimes of different antenna number of base station, transmit power of user, power scaling factor and interference factor for perfect and imperfect channel state information (CSI). The simulation results show that:(1) the bit error rate performance of IRC is lower than MRC and MMSE with low signal to noise ratio; (2) When the transmission power is increased, for imperfect CSI, the IRC performance is better than MMSE and MRC, and can not greatly improve the system performance, for perfect CSI, can effectively improve the IRC and MMSE receiver sys-tem performance and MMSE and IRC performance is similar; (3) Increasing the number of BS antennas, can effectively improve the system performance and the performance of IRC outperforms MRC and MMSE; (4) While maintaining a desired Qos, the transmit power of user can be inversely proportional to the square-root of the number of BS an-tennas for imperfect CSI and the number of BS antennas for perfect CSI. However, in the case of imperfect CSI, to achieve a certain spectral efficiency, the transmit power of user can be inversely proportional to the 3/4 power of the number of BS antennas, but also to save power.