| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 96 === Wireless sensor networks (WSN) is constituted by a large number of sensor nodes. In order to satisfy the application requirement, most sensor nodes use battery as its main energy source. Furthermore, energy consumption has been very important research topic in wireless sensor networks. With higher traffic load, the collision probability will be higher. Thus, the power consumption of sensor node will be increased, and the life time of wireless sensor networks will be decreased.
In IEEE 802.15.4 standard, superframe structure is used for data transmission. However, the duty cycle of the superframe structure cannot be dynamically adjusted according to the situation of entire network. Thus, when the number of devices and traffic load increase, the insufficient of active periods will decrease the transmission opportunities of devices and increase the collision probability. Thus, the above problems will cause the performance of entire network deteriorated.
In order to solve the above mentioned problems, we proposed the adaptive superframe adjustment scheme (ASFAS), it can dynamically adjust the duty cycle of the superframe according to the certain features observed by the coordinator, like the occupied proportion of superframe and collision proportion of devices. Thus, it can increase transmission opportunities of devices and improve the performance of entire network. We will compare our proposed scheme with some previous schemes and IEEE 802.15.4 standard through simulations. The simulation results of goodput, delay and power consumption shows the improvement of our scheme.
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