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Mobile messaging technologies and services sms ems end mms phần 2

Lamont (2005) "HOLSR: Cấu trúc Tiên phong thực hiện cơ chế định tuyến cho điện thoại di động Quảng cáo Networks Học," IEEE Communications,, 118-125. [5] M. Dillinger, K. Madani, và N. Alonistioti (2003) Software Defined Radio: Kiến trúc, hệ thống, và chức năng, John | 24 Mobile Messaging Technologies and Services The Wireless Data Protocol WDP is a general datagram service based on underlying low-level bearers. WDP offers a level of service equivalent to the one offered by the Internet s User Datagram Protocol UDP . At the bearer level the connection may be a circuit-switched connection as found in GSM networks or a packet-switched connection as found in GPRS and UMTS networks . Alternatively the transport of data at the bearer level may be performed over the Short Message Service e.g. for push messages or over the Cell Broadcast Service. 1.6.6 WAP HTTP Proxy with Wireless Profiled TCP and HTTP Figure 1.12 shows a configuration in which the WAP device communicates with application servers via an intermediary WAP proxy. The primary role of the proxy is to optimize the transport of content between the fixed Internet and the mobile network. It also acts as a Domain Name Server DNS for mobile devices. With this configuration Internet protocols are preferred against legacy WAP protocols. This is motivated by the need to support IP-based protocols in an end-to-end fashion from the application server back to the WAP device. The protocol stack of this configuration defined in the WAP specification suite 2.0 is shown in Figure 1.12. The Wireless Profiled HTTP WP-HTTP is an HTTP profile specifically designed for coping with the limitations of wireless environments. This profile is fully interoperable with HTTP 1.1 and supports message compression. The optional Transport Layer Security TLS ensures the secure transfer of content for WAP devices involved in the exchange of confidential information. Figure 1.12 Configuration with WAP proxy Basic Concepts 25 Figure 1.13 WAP configuration with direct access The Wireless Profiled TCP WP-TCP offers a connection-oriented service. It is adapted to the limitations of wireless environments but remains interoperable with existing Transmission Control Protocol TCP implementations. 1.6.7 HTTP with .