Remote Update For Node Using Contiki OS In WSN

With the expansion of scale of wireless sensor networks’(WSN) applications, the continuous improvement of network function requirements,and upgrading of the network system wireless, update of WSN node’s software will become an important part of the development of WSN. According to the development trend of IOT,the paper uses Contiki built-IP protocol as operating system of update node. By the analysis for Contiki OS and network protocol stack,combined with replacement of system image with loading of dynamical modules, the paper designs a method for remote update including programming of BOOT to update system after receiving update instructions, and programming of dynamic loader including relocation and loading processes related to STM32 analysis of principle of dynamic loading in Contiki.The paper designs a kind of file transfer protocol under transport layer in 6lowpan network protocol stack, introducing negative response(NACK) mechanism to transmit updated data reliably,adapting multicast to update specified nodes, deciding the time of retransmissions according to packet loss rate to reduce the number of retransmissions.In order to reduce the size of modules,the paper designs a method to compress attribute field of module related to STM32 and Contiki,then reorganizes modules’ structure, gives the method of modules restoration. Finally,the paper ports system kernel, clock and file system and serial Shell to STM32f103 microcontroller(MCU), in addition, translates development environment of Contiki from Linux to IAR.The test result of update of system and module shows that new system and module runs successfully.The test result of compression ratio of Module compression method shows that the proposed method can effectively compression module.The performance of File transfer protocol tests in Cooja simulator tests.The comparison of transmission time of files of different sizes shows that the time due to the waste of retransmission time can be reduced by controlling the timing of the retransmission.