Research On Extensibility Of DDS System For Internet Of Things

Data Distribution Service(DDS)is a distributed real-time middleware standard established by Object Management Group(OMG).Its publish/subscribe model provides a flexible decoupling capability for applications,and its P2P-based design brings efficient and real-time transmission performance to applications.Combining with rich QoS,DDS can well satisfy the performance and functionality needs of IoT systems.However,some limitations of protocol design make DDS difficult to apply directly to all application scenarios of IoT systems.To solve this problem,this thesis studies the extensibility of DDS for IoT.By way of extension,this thesis attempts to hold the performance advantages of DDS in core networks of IoT systems while enabling DDS to support more application scenarios.With analysis,this thesis concludes three problems when DDS was applied to IoT systems,and three corresponding extensions were designed:1.Cross-LAN integration extension:the extension implements cross-LAN data sharing by using a structure that combines public and LAN proxies.It can be compatible with DDS implementations of various vendors,and applications can use it without any modification.2.PPDP protocol extension:the extension proposes a Proxy-based Participant Discovery Protocol(PPDP)and offers a new QoS to express real-time requirements.By utilizing the extension,applications on energy-constrained devices can effectively reduce the amount of heartbeats to process in networks with high real-time applications.3.CSDDS extension:the extension introduces a server-side proxy to support client-server pattern.By transferring all client-side DDS interface calls to server-side through RPC,the extension can completely retain all DDS standard interfaces and reduces the costs of application development.This thesis designs and implements a prototype system based on proposed extensions,and evaluates the effectiveness of extensions through prototype system and PPDP protocol experiments.The results show that,in keeping compatible with the standard DDS,three extensions can achieve their objectives.In conclusion,extensions proposed by this thesis can make DDS applicable to the construction of IoT systems.