Medium access control protocols for cognitive radio based multi-hop wireless networks.

摘要

Traditional wireless communication networks use a static allocation of the frequency spectrum: individual applications are assigned fixed bands within the spectrum. It has been observed that this static allocation results in inefficient utilization of the spectrum bandwidth. The scarcity of the spectrum for new applications coupled with the under-utilization of a significant portion of the spectrum is driving the shift from a static to a dynamic allotment of the spectrum. Cognitive Radio (CR) technology provides a way to efficiently utilize the frequency spectrum by enabling wireless devices to adapt dynamically to the locally available spectrum and to each others' capabilities. Cognitive radios are capable of switching between wide range of frequency bands. The CR-enabled devices can either form a stand-alone multi-hop wireless network or form a multi-hop wireless backbone network that can connect different types of devices together.; In this work, we address the Medium Access Control (MAC) sub-layer issues in CR-based multi-hop wireless networks. The number of channels available and the channel identities vary from one node to another within the CR network. This is in contrast to the existing use of multiple channels where all the nodes have the same set of channels available (for example in IEEE 802.11 networks). In this work, we classify the CR-based networks into eight categories based on the following three characteristics: (i) Number of transceivers at nodes, (ii) Presence/absence of a global common control channel, and (iii) Presence/lack of synchronization. We present MAC sub-layer solutions for three of eight system models and derive solutions for the four other system models. The solutions presented in this work are evaluated by conducting extensive simulation experiments.