Realization Of Constrained Application Protocol Based On M2M Gateway

Internet of Things（IoT）describes an intelligent network blueprint that enablesautomated information exchange and processing between man and things or thingsand things. As an implementation technique of Internet of things, M2M has beenextensively studied, the related technicals and standards are becoming more and moremature. When the M2M underlying sensor network communicates with the uppertransmission network, M2M gateway should be needed. Present IP gateways arepowerful and stable, but do not apply to the resource-constrained environment, so it isnecessary to design a new M2M gateway which is full-featured as well as low powerconsumption, small size and good compatibility. In addition, because of M2Mterminal resource’s constraints, traditional web Transfer Protocol HTTP is not welladapted to M2M applications. Therefore, it is significant to do research on CoAP,which is used for restricted environment.Against this backgroundt, the paper does the research on the following aspects:(1) Analyzes the IoT and M2M technologies, introduces the research status ofM2M as well as system architecture, application examples, then puts forward theexisting problems in development and provides the corresponding strategy;(2) Introduces the development of Digi gateway development kit, based on thelearning of the gateway product features and principles, coming up with a concept ofthe gateway function design including the related modules;(3) Studies Contiki system, mainly focus on the Contiki’s event driven andlightweight thread mechanism, file system, application program and protocol stack asmuch as the simulation tool Cooja;(4) Investigate closely analyzes and researches the CoAP, including the messagesemantics, request/response mode, proxy and caching, resource identification andpositioning, security, etc., and makes a comparative study with the HTTP;(5) Consideres the CoAP’s implementation based on the Contiki system, anduses the Cooja simulation to verify whether the implementation could satisfy the basiccommunication functions. The main significance of the paper reflectes in the following aspects: Proposes aworkable M2M gateway hardware design and software system architecture forcommunication between transmission network and M2M underlying sensor network,and accomplishes the basic functions of low-overhead CoAP which is applicable tothe resource-constrained environment.