Research On Data Acquisition And Reliable Transmission In Wireless Image Sensor Networks

One of the basic functions of wireless image sensor networks is acquiring and transmitting image data through wireless ad-hoc networks. The integrated micro image sensors can be used to detect and collect environmental information. Image sensor nodes transmit image data to the sink node through wireless multi-hop ad-hoc networks. It eases users to monitor and control environment. Wireless image sensor networks have been widely used in environment monitoring, smart home, health and other fields.The paper mainly contains two parts:data acquisition and reliable transmission in wireless image sensor networks. Considering the limitation of energy consumption, processing speed, volume of image sensor nodes, this paper proposes a scheme for image sensor node system with dormancy mechanism. Through analyzing the command system and working principle of each module (the image sensor module, the embedded micro-controller module, the wireless communication module, the power supply module) in image sensor nodes, it realizes command control on image acquisition and system control on the process of image acquisition. Image sensor nodes transmit image data to the sink node via wireless channel.Compared to other short-range wireless communication technologies, this paper adopts the Zigbee wireless communication protocol as wireless communication mode. As the complexity of wireless channel, it is necessary to propose effective protection measures in order to ensure reliable image data transmission. After analyzing the existing wireless reliable communication mechanisms and the real system environment, this paper proposes an efficient retransmission and return acknowledgment mechanism based on Zigbee application layer in view of the vulnerability of retransmission mechanism of data transmission on Zigbee network layer. Firstly, this paper analyzes and tests data transmission based on retransmission mechanism on Zigbee network layer. As data transmission based on retransmission mechanism on Zigbee network layer consumes too much time which causes data transmission aliasing and data duplication reception, this paper proposes the design of data transmission on Zigbee application layer. According to the data reception of the sink node, this paper presents three communication mechanisms in the sink node to improve the processing ability, which are ACK response, data duplication reception response and Busy response. According to different response mechanisms of the sink node, the image sensor nodes make the corresponding operations of data transmission to improve data transmission reliability. This paper discusses the relationship between the different maximum number threshold of data retransmission and the consumed time or the packet loss rate in two ways, which are data transmission on the Zigbee network layer and on Zigbee application layer respectively. The experimental results show that compared to data retransmission mechanism on the Zigbee network layer, the data transmission mechanism designed on Zigbee application layer shortens the retransmission time consumed significantly and improves the reliability of data transmission.