Research On Communication Technology For Underwater Acoustic Sensor Network Based On Context Awareness

Underwater acoustic communication is as the most popular and widely used underwater communication technology,however,due to the characteristics of acoustic channel which are high delay and low bandwidth, the communication scheme of classical wireless network cannot directly applied to underwater communications, thus the efficient and reliable communication technologies need to be developed for realizing data transmission between underwater nodes. The MAC layer is an important part of the communication architecture, which is responsible for allocating the channel resources, and the high-performance MAC scheme can improve channel utilization.According to the problems existing in underwater communication, the article combines the context-aware and the underwater communication to conduct many researches which are as follows:(1) for lacking of a unified context modeling scheme, this article proposes a context modelling approach based on ontology for underwater acoustic network,which adopt four interrogatives (Who/When/ Where /What) to represent and retrieve the four dimensions on context information of underwater environment. The context modeling scheme applies the hierarchical and index mechanism, to ensure the uniqueness of the context information for maintaining easily.(2) for solving the problem of data transmission between the underwater equipm-ents, the article presents CACA-UAN, including the construction of the context-aware structure and components, which exploits three handshake based on the idea of TCP to establish a reliable connection, and the context service to achieve the fast discovery.The CACA-UAN adopts the channel access mechanism based on CDMA. The simulation results have shown the CACA-UAN can achieve low collision probability and packet drop rate, as well as more stable jitter.(3) for conducting the research on the MAC layer of underwater communication architecture, the article proposes the CAMA-UAN, which is based on the CACA-UAN model where joining the competition mechanism, and presents the solution to adjust the slots of MAC frame according to the update context. The experimental results have shown the CAMA-UAN can achieve low transmission delay.