Smart Antennas in Wireless Networks : Systems Issues and Performance Limits

Abstract: This work deals with performance limits when using smartantennas in future wireless systems. The current evolution inthe field of wireless communication implicates a substantiallyincreased demand on transport capacity. Smart antennas is onevery powerful means to fulfill these demands. In this work theuse of smart antennas, deployed at either the access point orboth the access point and the mobile terminal isinvestigated.In order to find out how the evolution within wirelesscommunication will continue during the ten years to come, ascenario analysis is performed where driving forces areidentified and scenarios are created.The system aspects of uplink and downlink communicationsutilizing smart antenna algorithms are investigated. For theuplink case, the impact of different smart antenna algorithmson a packet switched radio interface is investigated. In thedownlink case, the use of joint optimal beamforming and powercontrol is examined and compared to suboptimal downlinkalgorithms. Further, an algorithm for admission control isintroduced and evaluated and the issue of optimal access pointassignment is assessed.The extension to use smart antennas with both multipletransmitters and multiple receivers, i.e. dual arrays, canprovide high link capacity in future wireless systems. Ananalysis of indoor environment channel measurements in the 5.8GHz band is performed and the possible increase in linkcapacity is examined. It is found that in the measured indoorenvironment, the scattering is sufficiently rich to providesubstantial link capacity increase and that moderateintra-antenna-element distances is enough to give this capacityincrease.It is concluded that smart antennas promise substantialcapacity increase and remains a strong enabling technology forfuture systems for wireless communication