Research On Precoding Design In Mimo Cognitive Radio System

Recently years, as so called the information age, the demand for ubiquitous communications become important. So the wireless communication network is highly required. The rapid growth of wireless communications requires faster transfer rates, higher transmission quality, but radio spectrum resource is limited, which constrains the development of wireless communication. Therefore, efficiently and reasonably use spectrum resources has become a priority. In the study of next generation wireless communication network, due to significantly improve network throughput and spectrum efficiency, Cognitive Radio and MIMO technology is in depth research and extensive discussion.Cognitive Radio, due to the advantages in automatic detection work environment, self-configuring system resources, transmission parameter adjustment and changes in work patterns, etc., can make primary users and secondary users share the same spectrum, greatly enhance the spectral efficiency. MIMO, as the core technology of3G and LTE standard, has got widelv attention both in academia and industry in recent years.In this paper, author mainly studies the design of precoding in MIMO Cognitive Radio systems. Research is divided into two parts, one is precoding design in the cognitive radio environment based on the principle of minimum transmit power. Another is precoding design with interference alignment in cognitive radio environment. In the precoding design based on the principle of minimum transmit power, with different scenario of perfect channel state information (CSI), and imperfect CSI, consider the secondary users transmission rate requirements and the primary user’s interference tolerance, author establishes optimization mathematical model and uses semidefinite programming (SDP) method to solve it. In the precoding design with interference alignment, with cooperation between primary and secondary users and interference alignment, author use the extra spatial dimensions MIMO multi antenna provides the signal transmitted by secondary users aligned to the spatial dimension in which primary user is missing. So we can eliminate secondary user interference caused to the primary user. The transmitted signal is aligned to the primary user’s not being used spatial dimension, to eliminate the interference from primary user to the second user, which can greatly improve the throughput and spectral efficiency of the system. Finally, the simulation results verifies the theoretical analysis...