Interference Alignment Application In Wireless Telecommunication System

The strain in spectrum resources becomes increasingly prominent. To meet the increasing demand of wireless communication services, maximizing spectral efficiency is an important way to enhance a solution to the problem. The main way to improve spectrum efficiency is to reduce the reuse factor, so that reducing the distance between each cell. However, a lot of research and experimental data prove simply reduce reuse district does not bring a huge upgrade from the spectral efficiency, even leads to a decline in the efficiency of spectrum. The main reason is due to reduced cell reuse distance brought a lot of co-channel interference neighboring cells. Therefore the co-channel interference is one of the most serious problems in the next generation wireless communication systems since it leads to low spectrum efficiency. Interference alignment technology to solve these problems provides an effective way. Interference alignment (IA) method is considered as a kind of extremely potential interference management technology, which is shown to achieve the maximum degrees of freedom (DoF) in interference channel. However, due to the conditions of interference alignment algorithm relatively harsh environment of the wireless communications device is configured with the strict requirements. Therefore interference alignment technique is difficult to obtain performance gain in the current network theory, the algorithm can not be achieved even. This paper mainly studies the interference alignment technology in the application of the wireless communication system, the actual communication environment affect the performance of interference alignment algorithm and corresponding counterplot. As follows:1) It’s difficult to apply interference alignment algorithms to the communication net. On the one hand, the reason is that the harsh conditions of interference alignment algorithm itself. On the other hand, the delay and lack of the feedback is another reason. The paper summarizes the common problems of the application of interference alignment in the communication net. From the ideal channel information and non-ideal channel information two aspects, the application of alignment algorithms is presented. For the ideal channel information, a two-cell multiuser MIMO interference channels is studied. By aligning adjacent cell interference successfully, the degrees of freedom in every cell are improved. Compared with TDMA’s way to avoid interference, degrees of freedom are increased to4from3. For non-ideal channel information, this paper analyses the channel delay and lack of information on the properties of interference alignment algorithm. Based on blind interference alignment and retrospective Interference Alignment, this paper studies their algorithm and show even if there is a delay and loss of channel information, interference algorithm is still used and promotes freedom of upper limit.2) This deeply studied the interference alignment algorithm application in two-cell multi-user system model. The classical interference alignment algorithms consider the alignment condition is ideal. But that does not accord with the actual communication scenarios. This paper deduces the relation between the alignment condition and the number of users, antennas, data streams in two-cell multi-user system. It is showed that the alignment condition is not always satisfied. Once the number of users exceeds the limitation of the perfect alignment condition, the interference signal will leak into useful signal space. In this paper, we present a novel self-adapting interference alignment algorithm. In our algorithm, according to different alignment conditions, designing transmit beamforming matrices can be divided into two types. Especially, when the alignment condition is switched from perfect to imperfect, transmit beamforming matrices in the propose algorithm can not only eliminate the intra-cell inter-user interference (IUI) and the aligned inter-cell interference (ICI), but also mitigate the leaked ICI in the maximum extent. Finally, Simulations show that the proposed algorithm achieves the better performance in terms of sum rate.