Interference Cancellation Technology Based On LTE Multi-cell System

To maximize the capacity of the network and improve the efficiency of the limited spectrum, LTE standard involves the full-frequency re-use strategy. The biggest drawback of this strategy is the interference problem, owing to the good interference-free feature of Orthogonal Frequency Division Multiplexing (OFDM) technology, the intra-cell interference in LTE system can basically be ignored. However, the inter-cell interference grows significantly and becomes a critical problem to be addressed. As a novel interference management technique, Interference Alignment (IA) is able to effectively suppress the influences of unexpected signals at the receiver, mitigate and even eliminate the effects of interference on signal transmission and demodulation. Interference Alignment has received widely attention and investigation since its birth, and has obtained some research achievements. Based on above statement, this paper proposes a novel Interference Alignment algorithm to work out the severe interference problem caused by LTE multi-cell co-frequency networking. The new algorithm selects different Interference Alignment criterions adaptively according to current transmission condition. It inherits the excellent interference suppression characteristic of the Interference Alignment algorithm and meanwhile, always keeps the optimizing system sum-rate. First of all, this paper conducts a deep analysis on current distributed Interference Alignment algorithms, and mainly focus on minimum interference leakage (MIL), maximum Signal-to-Interference-Noise-Ratio (Max-SINR) and Minimum Mean Square Error (MMSE) criterion respectively. The simulation results show that, compared to the traditional "cake-cutting" resource allocation strategy, Interference Alignment can effectively eliminate the influences of interference signals. Furthermore, this paper makes a comparative analysis of those three algorithms’sum-rate curves and concludes that under different SNR conditions, there has one and only one optimum algorithm. Secondly, based on the existed analysis results, this paper proposes a novel Interference Alignment algorithm for the multi-cell co-frequency networking system under the LTE standard. In this algorithm, the receiver can select the Interference Alignment algorithm adaptively according to the real-time SNR. In the meanwhile, this paper proposes to make the direct connection between the algorithm selecting period and channel coherent time, to keep the algorithm being updated in time and reduce the system overhead. The simulation results show that the newly proposed algorithm can always achieve the optimum system performance under different SNR conditions.At last, considering the impact of imperfect Channel State Information (CSI) at the receiver, we replace the channel estimations at the receiver with the actual channel matrix with estimating-error. Also, the correlation between the estimated channel and the ideal channel is described by a correlation coefficient, named p, then, we choose from different values of p to estimate the influence of channel estimation errors. The simulation results show that the less the correlation between the estimated channel and the ideal channel, the more the system performance falls. In the end, to increase the robustness of this new algorithm to imperfect channel estimation, this paper proposes to involve the consideration of channel estimation errors when calculating the Interference Alignment matrix.