Medium access control( MAC) protocol of underwater acoustic communication network is a key technology for underwater acoustic networks( UANs). Most of the MAC protocols for wireless terrestrial communication networks ...Medium access control( MAC) protocol of underwater acoustic communication network is a key technology for underwater acoustic networks( UANs). Most of the MAC protocols for wireless terrestrial communication networks have been designed with negligible propagation delay. If it is deployed directly in an underwater environment,the UANs will perform inefficiently. In this paper,the characteristics of underwater acoustic channel are modeled and simulated by using the OPNET simulation tool,which are the speed of sound, propagation loss, and four sources for ambient noise: the turbulence,shipping,wind driven waves and thermal noise. The performance of pure Aloha( P-Aloha),carrier sense multiple access with collision avoidance( CSMA / CA) and multiple access collision avoidance for wireless local area network( MACAW) protocols in underwater acoustic channel environment are evaluated. The different performance of protocols in underwater environment is compared in the simulation.展开更多
Many coal enterprises have built the videoconference systems on their LAN （Local Area Network）. As the development of these enterprises, their organizations are distributed over our country and even over the world. ...Many coal enterprises have built the videoconference systems on their LAN （Local Area Network）. As the development of these enterprises, their organizations are distributed over our country and even over the world. Therefore, the videoconference systems have to run over WAN （Wide Area Network）. Normally, the structure of a videoconference system is center_division including MCU （multi control unit）and participants. No QoS and security assurance are available now because all videoconference system is based on TCP/IP. Therefore, the system stability is absolutely depended on the Network. This paper discussed how to anti ARP attacking. The method discussed in this paper is based on TCP/IP.展开更多
基金National Natural Science Foundations of China(Nos.60872073,6097501,and 51075068)the Doctoral Fund of Ministry of Education of China(No.20110092130004)the Research Foundation and Education Bureau of Anhui Province of China(No.KJ2009B137)
文摘Medium access control( MAC) protocol of underwater acoustic communication network is a key technology for underwater acoustic networks( UANs). Most of the MAC protocols for wireless terrestrial communication networks have been designed with negligible propagation delay. If it is deployed directly in an underwater environment,the UANs will perform inefficiently. In this paper,the characteristics of underwater acoustic channel are modeled and simulated by using the OPNET simulation tool,which are the speed of sound, propagation loss, and four sources for ambient noise: the turbulence,shipping,wind driven waves and thermal noise. The performance of pure Aloha( P-Aloha),carrier sense multiple access with collision avoidance( CSMA / CA) and multiple access collision avoidance for wireless local area network( MACAW) protocols in underwater acoustic channel environment are evaluated. The different performance of protocols in underwater environment is compared in the simulation.
文摘Many coal enterprises have built the videoconference systems on their LAN （Local Area Network）. As the development of these enterprises, their organizations are distributed over our country and even over the world. Therefore, the videoconference systems have to run over WAN （Wide Area Network）. Normally, the structure of a videoconference system is center_division including MCU （multi control unit）and participants. No QoS and security assurance are available now because all videoconference system is based on TCP/IP. Therefore, the system stability is absolutely depended on the Network. This paper discussed how to anti ARP attacking. The method discussed in this paper is based on TCP/IP.
