Self-organizing Dynamic Spectrum Management: Novel Scheme for Cognitive Radio Networks.

Abstract

<p>A cognitive radio network is a multi-user system, in which different radio units compete for limited resources in an opportunistic manner, interacting with each other for access to the available resources. The fact that both users and spectrum holes (i.e., under-utilized spectrum sub-bands) can come and go in a stochastic manner, makes a cognitive radio network a highly non- stationary, dynamic and challenging wireless environment. Finding robust decentralized resource-allocation algorithms, which are capable of achieving reasonably good solutions fast enough in order to guarantee an acceptable level of performance, is crucial in such an environment. In this thesis, a novel dynamic spectrum management (DSM) scheme for cognitive radio networks, termed the self-organizing dynamic spectrum management (SO-DSM), is described and its practical validity is demonstrated using computer simulations. In this scheme, CRs try to exploit the primary networks’ unused bands and establish link with neighbouring CRs using those bands. Inspired by human brain, the CRs extract and memorize primary network’s and other CRs’ activity patterns and create temporal channel assignments on sub-bands with no recent primary user activities using self-organizing maps (SOM) technique. The proposed scheme is decentralized and employs a simple learning rule with low complexity and minimal memory requirements. A software testbed was developed to simulate and study the proposed scheme. This testbed is capable of simulating CR network alongside of a cellular legacy network. In addition to SO-DSM, two other DSM schemes, namely centralized DSM and no-learning decentralized DSM, can be used for CR networks in this software testbed. The software testbed was deployed on parallel high capacity computing clusters from Sharcnet to perform large scale simulations of CR network. The simulation results show, comparing to centralized DSM and minority game DSM (MG-DSM), the SO-DSM decreases the probability of collision with primary users and also probability of CR link interruption significantly with a moderate decrease in CR network spectrum utilization.</p>