With the rapid development of wireless communication, more and more people can access the communication network conveniently and efficiently, but it also brings the reality and difficulty of the lack of wireless spectrum resources. The academic community has conducted in-depth research on the lack of spectrum resources, and a technique called interference alignment is expected to completely solve the bottleneck of lack of wireless resources.
When multiple users perform wireless communication, there will be interference between each other, and the interference will affect the signal reception quality and reduce the channel capacity of the receiver. Existing techniques for handling interference, such as frequency division multiplexing (FDMA), time division multiplexing (TDMA), and code division multiplexing (CDMA), primarily eliminate the effects of interfering signals on the desired signal by orthogonalizing the signals. In fact, when multiple users share spectrum resources, this processing method can only allocate spectrum resources among K users. For example, when the number of users interacting with each other is K, the spectrum resource that each user can obtain is 1/K of a single user. Therefore, when the number of users is large, the spectrum resources available to each user are still very limited.
The interference alignment technique is proposed to solve this problem. It divides the signal space into two parts: the desired signal space and the interference signal space. The precoding technique allows the interference to overlap at the receiving end, thereby compressing the signal capacity occupied by the interference and eliminating The effect of interference on the desired signal is achieved for the purpose of increasing the channel capacity.
At present, Assistant Professor Jafar of the University of California, Irvine has theoretically proved that by interference alignment, in the wireless communication channel of K users, each user can obtain up to 1/2 of the total spectrum resources when there is only one user. The spectrum resources that K users can obtain are k/2 times that of only one user. Professor Health at the University of Texas at Austin conducted experimental verification of interference alignment. The experimental results show that interference alignment can greatly improve the spectrum utilization of the system.
Of course, the interference alignment technique is still in the research stage, and many problems remain unresolved. Firstly, the global channel state information required for interference alignment is difficult to achieve in practice. Secondly, as the number of users increases, the constraint conditions of interference alignment will increase sharply and become difficult to implement. This is also a hotspot in the field of interference alignment. It is believed that as the research progresses further, these problems will eventually be solved, and the interference alignment technology will become an effective weapon to solve the problem of lack of spectrum resources.
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