Research On The Medium Access Control Protocol Of Cognitive Radio Sensor Networks

A huge amount of researches have been done and much attention has gained on wireless sensor network(WSN) due to its widespread application. While the crowded spectrum where WSN works restrained it's furthermore development. The cognitive radio technique provides WSN an efficient way to extend the spectrum resource for working, and then more attention and further research were carried out on cognitive radio sensor network(CRSN). Medium access control(MAC) protocol has a deep influence on energy efficiency and working orderly of WSN, thus it becomes a study focus in the research domain of WSN and CRSN gradually.Firstly, nodes sleep-awake scheduling mechanism of WSN is researched in this thesis. It is essential for sensor nodes to lower their energy consumption thus wireless sensor network can prolong it's lifecycle by the nodes sleep mechanism. The only consideration of existing nodes sleep scheduling algorithm is the energy consumption. However, the scheduling mechanism which is proposed to save nodes' energy would easily cause the sensor networks' incompletely coverage of the monitoring area, leading to serious consequences. Based on the shortage of the existing scheduling algorithms, an energy-efficient scheduling mechanism is proposed in this thesis which takes into account the deployment density and sense coverage. Thus nodes are centralized scheduling which will depress the redundant data sensing, processing and transmitting. This mechanism can not only lower the network energy consumption but also balance the monitor coverage. Simulation results show that the proposed mechanism can improve the network lifecycle effectively at the premise of ensuring high network coverage.Secondly, a new type network named heterogeneous node CRSN(HT-CRSN) is proposed in the thesis based on the background of extra energy consumption and process requirement brought by cognitive function and its high-cost in CRSN. The cognitive function was separated as another kind of node called cognitive node(CN) in the HT-CRSN, in the meantime the capabilities of stronger process and energy harvesting are given to CN. Then deploy the cognitive node with the ordinary sensor node according to a certain proportion. Most of the process tasks are given to the stronger functional cognitive node which will not only improve the network performance extremely but also make the deployment convenient and lower the deploy cost. Furthermore the work sequence and feasible MAC protocol suited for the HT-CRSN are put forward. The energy consumption of proposed MAC protocol is analyzed and the simulation results showed that the energy consumption of two kind of heterogeneous nodes can be balanced by adjusting their deployment ratio and energy harvesting rate, thus the network lifetime will be improved.Deep studies on MAC protocol and relative key techniques of CRSN are carried out in this thesis, and a number of results are obtained, which have some theoretical value for future research of CRSN.