Interference Diversity Gain and its Application in Multi-Channel Systems: Capacity Maximization and QoS Guarantee Strategies

As the spectral efficiency of wireless communications systems increases, and the frequency reuse pattern shifts towards universal frequency reuse, the capacity of future wireless and mobile systems will becomes interference limited. We explore the interference pattern of a shared channel in order to establish optimal distributed resource allocation techniques in that channel considering the mutual interference of coexisting links on each other. It is shown that the optimal usage of resources in such a shared channel can only be achieved via a multi-dimensional resource allocation strategy, taking into account not only the link´s own channel quality, but also its channel states towards coexisting links. The improvement of capacity as a result of this approach can be attributed to the interference diversity of the channel. The interference diversity gain can be harnessed in time, frequency and space domains. To this end we study two approaches, namely maximizing the capacity of the primary and secondary links under received interference constraint and minimizing the transmitted power of primary and secondary links under minimum QoS guarantee constraint. We study the Ergodic capacity to verify the significant performance improvement which can be achieved by exploiting interference diversity in multi-channel systems such as UMTS Long Term Evolution (LTE). Further we will show that utilizing this diversity gain in QoS-guaranteed scenarios results in a considerable transmission power saving. The case of Outage capacity, which is an instantaneous measure of channel throughput, is shown to be different whereby using an instantaneous received interference threshold outperforms the usage of average received interference limit.