Design And Implementation Of Wireless Sensor Network Layer Protocol Applied To Spacecraft Data Acquisition

With the continuous development of aerospace electronic technology and the improvement of the intelligence of spacecraft,the traditional wired data collection methods have brought great difficulties to the design and maintenance of spacecraft.A large number of cables also occupy valuable loads and space.As a new technology in the field of spacecraft communication and measurement control systems,wireless sensor networks have opened up new ideas for the acquisition of spacecraft sensor data,which is also one of the hotspots in the field of aerospace research.In view of the spacecraft's need for network reliability,a network protocol based on uIP protocol stack and wireless data acquisition for spacecraft is designed in this thesis.In the design of this thesis,in order to ensure the coverage and real-time,a networking scheme based on the sensor type to establish a star topology and a mesh topology is established within the framework of the RPL(Routing Protocol for Low-power and Lossy Networks)routing protocol.Centering on the core of network reliability,in order to avoid routing jitter caused by uneven routing of relay routing nodes,a hybrid metric objective function based on received signal strength indicator and expected lifetime is designed;in order to ensure the reliability of the the network topology messages stored in the nodes,a redundant judgment scheme for the consistency message detection is designed based on the Trickle timer algorithm.In order to reduce the delay caused by redundant operation of relay nodes,a network layer data reassembly strategy based on bitmap and mask is designed for 6LoWPAN(IPv6 over Low-Power Wireless Personal Area Networks)slicing and reassembly technology.Based on the above key technologies,this thesis implements the network layer protocols,including the design of buffer queues and the design of neighbor table structures;the implementation of header decompression and data reorganization module,header compression and data fragmentation module;and the implementation of RPL routing control message structure design and control messages sending module,receiving module.The protocol is based on the ATmega128RFA1 hardware platform and the Contiki system.The test results show that the protocol can complete the establishment of star network and mesh network,and realize the functions of data compression and fragmentation,decompression and reorganization of the6LoWPAN;the measurement of star topology construction needs 4.912 seconds and mesh topology construction time consuption requires 6.397 seconds,and the repair time of local network repair scheme isbetween 3 seconds and 4seconds,the packet loss rate of the star network is 0.14%,and the packet loss rate of mesh network is 2.58%,the delay of the star network is 28.532 ms per hop,and the delay of the mesh network is 28.618 ms per hop.All indicators reach expectations.