(The) study on multiuser diversity gain in conitive radio systems

Abstract

In point-to-multipoint communication system, the channel aware opportunistic scheduling provides a significant improvement in throughput performance by exploiting the fluctuation of fading channel. The scheduling gain in terms of capacity grows as the number of candidates increases, and it so called multiuser diversity gain. In this thesis, we investigate the multiuser diversity gain and the scaling law of the average achievable capacity in CR system where the secondary transmitters opportunistically utilize the vacant spectrum licensed to primary user. It is shown that the sensing performance at the secondary network and the traffic dynamics of the primary user directly affect the capacity of secondary capacity. Furthermore, the scaling law of the secondary capacity can be classified into two types according to whether the maximum transmit power of secondary transmitter is finite or not, and these are different from that of non-CR system due to the interference regulation. Interestingly, it is also shown that the characteristics of scaling law, according to the maximum transmit power of secondary transmitter, are very similar to that of underlaid CR system.