| Recently, Wireless Sensor Network (WSN) as an emergingtechnology develops rapidly. It is not only a single new network technology,but also a combination of sensor technology, distributed processingtechnology and embedded technology. Wireless sensor network devicesgenerally include management nodes, sink nodes and sensor nodes. A largenumber of sensor nodes deployed randomly within the monitor region, build anetwork transmission system by wireless self-organizing approach, the sensorson the sensor nodes collect environmental data collaboratively, and then sendthe information to sink node by wireless and multi-hop transition. Finally, thedata will be transmitted to management node through satellite, Internet, etc. Inthis way, users can easily collect monitoring data, manage and configure thenetwork running state.As the continuous development of wireless sensor network technology,there are also some network transmission problems standing out recently. Datadelay, information loss and other phenomena has a great impact of the using effect ofthe network in the process of transmission, so how to improve the Quality ofService (QoS) of wireless sensor networks has become an urgent problem tobe solved. A growing number of scholars have studied about the method whichcan satisfy the QoS of the network from the perspective of modifying therouting protocols, optimizing network scheduling and etc.This thesis introduces the history and the domestic and overseasdevelopment situation of wireless sensor network, and analyses the QoSproblem. Data handling capacity, storage capacity and energy supply ofwireless sensor network node is very limited, and the network topologychanges frequently, its QoS is very different from traditional network QoS.Based on careful analysis of the difference of the both, the thesis summarizesthe special mechanism characteristics and the evaluation criteria of thewireless sensor network QoS, and further divides QoS into two basic level,task level and application level, and analyses the relation between the twolevels. This thesis analyses some problems and challenges caused by thedistinguished features of wireless sensor network QoS. In order to do further research and verification on wireless sensornetwork and related QoS technology, author designed a wireless sensornetwork experiment platform which can be divided into two parts, hardwareand software. In node’s hardware design, using PIC series microcontroller anda2.4GHz RF transceiver MRF24J40as control and communication devices,communication between nodes following IEEE802.15.4/Zigbee protocol.Upper computer software can show the real-time running state and thecollecting data of each node clearly, and control or adjustment the nodes andnetwork easily. The experiment platform is a necessary material guarantee forwireless sensor network research and experiments.Based on previous studies about QoS, in order to improve the standard ofwireless sensor network QoS and reduce the negative impact of inherentnetwork time-varying transmission delay, packet loss and other phenomena onperformance of the network, a kind of multi-objective optimization controlmethod based on QoS management is proposed from the perspective ofimproving the overall system performance. The optimization control methodtakes deadline miss ratio as the QoS evaluation criteria. In the process of thedata transmission between sensor nodes and sink node, use the PID controllerto calculate the network bandwidth requirements of all sensor nodes. On thisbasis, by solving the multiple objectives optimization problem, the dynamicadjustment on the packet sending period of all sensor nodes can be achieved.It makes the network bandwidth allocation adapt to the QoS changes, andguarantees the network has a good communication quality. Finally, authorvalidated the optimization control method by experiment on the wirelesssensor network experimental platform, the experimental results indicate thatthe optimization control method is reasonable and effective. |
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