Design Of Wireless Sensor Network Nodes And Networking Research

Wireless sensor network is a comprehensive system of data acquisition,transmission and processing.The technology has been widely used in environment monitoring,urban transport and military defense etc.For real-time monitoring of the environment information in short distance such as temperature, illumination and humidity, design and implementation of a reliable and low power consumption wireless sensor network is very instructive.In this case, a reliable and low power consumption network is required instead of high data-rate and remote data transmission.In this paper, the design of wireless sensor network is divided into two parts:the software design and hardware design.The software design includes the design of network layer protocols, code programming and PC interface.The network topology and routing are obtained through the method of combining BFS algorithm with Dijkstra algorithm. Accordingly, the adjacent and weight matrices are obtained,then,the information of matrices is substituted in the Dijkstra algorithm to calculate optimal pathes.The routing table is sent to other nodes by the coordinator one and stored in a memory matrix.Routing generation process includes broadcast addressing, neighbor nodes detection, generating and forwarding the routing table.The coordinator node uses broadcasting mode to search other nodes in order to get their address.When using the broadcasting mode to get their address of sub-nodes,time division multiple access method is employed to prevent the sub-node address missing.To make sure that the communication is reliable, packet loss retransmitting mode is introduced in the data forwarding.The hardware design includes wireless transceiver circuit design and sensor circuit design. The wireless transceiver circuit is based on2.4GHz RF chip nRF241E1.The impedance bandwidth, radiation pattern and efficiency of the folded monopole antenna are simulated.The theory value of transmission distance in free space under the Odbm transmitting power is calculated.The sensor circuit is based on the temperature humidity sensor DHT11and photo sensor On9658.The data acquisition timing pulse referring to the requirements of DHT11is designed.The node circuit boards are drawn by Altium Designer software.A field network is used to test the performance of the design, including the maximum transmission distance,routing and communication reliability. The results show that the designed sensor network can meet the requirements for real-time monitoring and low power consumption.