Research On Self-interference Suppression In Full-Duplex Relays

High speed, low power consumption, and high spectrum efficiency has been long-term goal in the field of wireless communications. In order to meet people's growing requirements for mobile communication business, as one of the key technologies in the next generation of mobile communication, relay communication technology arises at the historic moment for the reason that it can improve the capacity of system and expand the coverage of communication network. The traditional relay nodes work in half-duplex mode, which means receiving and sending signals needs more than one time slot, so the spectrum efficiency of communication system is low. In order to improve the spectrum efficiency, people begin to study full-duplex relay technology, which means sending and receiving signals can be completed at the same frequency and at the same time. on one hand, it has brought to promote the spectrum efficiency, on the other hand, due to the fact that sending and receiving signals at the same frequency and at the same time, relay nodes have produced serious self-interference between the receiver and the sender, which may lead to the worse performance of the full-duplex relay system than that of the half-duplex relay system. Therefore, how to eliminate the self-interference becomes a serious problem to be solved in the full-duplex relay system. This paper mainly has studied the self-interference elimination technology in full-duplex relay system, and aims at further improving the channel capacity of the full-duplex relay system at the same time. The main work includes:First of all, we introduce the basic theory of relay technology based on the classification of relay technology, relay protocol and the application of relay. In order to further study full-duplex MIMO relay technology, then we expound the MIMO communication technology adopted in relay system, which provides the theoretical support for the later research.Secondly, this paper analyzes the cause of self-interference in full-duplex relay system, then we has studied the self-interference elimination technology in time domain for full-duplex SISO relay system and the self-interference elimination technology in spatial domain for full-duplex MIMO relay system, respectively. Not only the principle of the self-interference elimination has been expounded, but also the mathematical formula is given to demonstrate the process of self-interference elimination, then the self-interference in full-duplex relay system is suppressed.Finally, aiming at improving the performance of the full-duplex relay system, this paper puts forward a kind of algorithm based on singular value decomposition which has maximized the channel capacity. Compared with the existing self-interference elimination methods, the algorithm can further improve the channel capacity of full-duplex relay system, and we has verified the correctness and effectiveness of the proposed algorithm through simulation.