Performance Analysis Of The Cognitive MIMO Networks With Maximum Ratio Transmission

With the rapid development of wireless users and the rapid growth of wireless services，limited resources of wireless spectrum have made it a key solution to solve the inherent problemof low utilization of spectrum in fixed spectrum allocation strategy. Recent years, the technologyof Cognitive Radio (CR) has provided us with such a solution: Secondary users (or unauthorizedusers、cognitive users, SU) can share the primary users’(or authorized users, PU) spectrum byintelligent sense of the spectrum state. This mechanism has been confirmed by many scholarsthat it can improve spectrum utilization effectively, therefore making it a hot field in dealingwith spectrum scarcity.The technology of Multiple-Input Multiple-Output (MIMO) provides spatial diversity andmultiplexing gain by the trans-receiver’s diversity technology. Under the premise of notincreasing system bandwidth and transmit power, it can improve spectrum efficiency of wirelesscommunication system, system capacity as well as transmission reliability. These advantageshave made it the core technology of the fourth generation of mobile communication which canmeet the great needs of high rate and high capacity in the future. Meanwhile, the combination ofMIMO and CR network will bring additional spatial DOF for the cognitive radio access toauthorized spectrum besides frequency and time. Therefore, it’s quite important to study MIMOnetwork on the background of CR, namely cognitive MIMO network.Framework of this paper is mainly divided into two parts. We adopted a sharing model ofcognitive radio spectrum based on interference temperature between primary and secondaryusers. This mechanism uses coexist spectrum access (CSA) method, that is coexist of primaryand secondary users, under the premise to ensure normal communication for primary user whenrestraining secondary users. Between the transmitter and receiver of secondary users, we usedthe diversity technology of Maximum Ration Transmission and Maximum Ratio Combining inMIMO to analyze the capacity of system and outage probability. Also, with related simulationsby Matlab, we analyzed system capacity, outage probability，bit error rate and other propertieswith and without the consideration of CSI channel error. Finally, conclusion comes out thatwithout consideration of CSI channel error, system capacity will increase along with the numberof transmit antennas, interference temperature threshold and amount of secondary users while outage probability and bit error rate is reducing accordingly. When we consider CSI channelerrors, compared with non-error situations, it’s confirmed that the capacity, outage probabilityand bit error rate will deteriorate in different degrees with increasing errors. This theory providesa theoretical basis for the future communication system and has important practical significance.