Capacity Analysis Of Multi-user MIMO Spectrum Sharing Systems Based On Channel State Information

The spectrum sharing system has been shown to be a very effective technique to improvespectral efficiency in wireless communication. In a spectrum sharing system, secondary users areallowed to utilize the spectrum licensed to primary users only if interference caused by thesecondary users is regulated below a predetermined level. The maximum allowable interferencelevel at the primary users’ receiver is called interference temperature and guarantees reliableoperation of the primary users regardless of secondary users’ spectrum utilization. Moreover,MIMO technology is widely used in wireless communication to enhance the reliability andincrease the total capacity of the system. This intention of this thesis is to combine the twotechnologies together.Firstly, we focus on the single user and single antenna spectrum sharing system withimperfect channel state information. Based on the obtained SNR analysis of the secondarysystem, we obtained the closed-form expressions of the system average capacity. Furthermore,some special cases are considered. In particular, ignoring the interference between thetransmitter of the primary user and the receiver of the secondary user and assuming largeinterference temperature, we present the capacity analysis for such cases. The analytical resultsare verified through Matlab simulations.Secondly, this thesis further studies the multiple users multiple antennas spectrum sharingsystem over the Rayleigh fading channels. We restrict our analysis to the system where thetransmit power of the secondary users is only limited to the interference temperature of theprimary user. With this aim, the closed-form expressions of average capacity of the system arederived. More specifically, we consider a single-antenna system and other three different MIMOschemes: selective transmission/selective combining (ST/SC), transmitter diversity/selectivecombining (TD/SC) and space–time block codes (STBC), and then derive the correspondingcapacity expressions based on the different SNRs of secondary system.Finally, numerical results show that the ST/SC scheme can obtain the highest capacity, andthe STBC method has no advantage in the spectrum sharing system. Our results have certainguiding significance for practical application.