外文翻譯----在sms蜂窩網(wǎng)絡(luò)上進(jìn)行開(kāi)放式功能的開(kāi)發(fā)(文件)
【正文】 外文翻譯 6 Exploiting Open Functionality in SMSCapable Cellular Networks 1． SMS/CELLULAR NETWORK OVERVIEW This section offers a simpli?ed view of an SMS message traversing a GSMbased system from submission to delivery. These procedures are similar in other cellular works including CDMA. Submitting a Message There are two methods of sending a text message to a mobile device via another mobile device or through a variety of External Short Messaging Entities (ESMEs). ESMEs include a large number of diverse devices and interfaces ranging from and webbased messaging portals at service provider websites to voic services, paging systems and software applications. Whether these systems connect to the mobile phone work via the Inter or speci?c dedicated channels, messages are ?rst delivered to a server that handles SMS traf?c known as the Short Messaging Service Center (SMSC). A service provider supporting text messaging must have at least one SMSC in their work. Due to the rising popularity of this service, however, it is being increasingly mon for service providers to support multiple SMSCs in order to increase capacity. Upon receiving a message, the contents of ining packets are examined and, if necessary, converted and copied into SMS message format. At this point in the system, messages from the Inter bee indistinguishable from those that originated from mobile phones. Messages are then placed into an SMSC queue for forwarding. Routing a Message The SMSC needs to determine how to route messages to their targeted mobile devices. The SMSC queries a Home Location Register (HLR) database, which serves as the permanent repository of user data and includes subscriber information (. call waiting and text messaging), billing data, availability of the targeted user and their current location. Through interaction with other work elements, the HLR determines the routing information for the destination device. If the SMSC receives a reply stating that the current user is unavailable, it stores the text message for later delivery. Otherwise, the response will contain the address of the Mobile Switching Center (MSC) currently providing service. In addition to call routing, MSCs are responsible for facilitating mobile device authentication, location management for attached base stations (BS), performing handoffs and acting as gateways to the Public Switched Telephone Network (PSTN). 畢業(yè)設(shè)計(jì)（論文） 外文翻譯 7 When a text message arrives from the SMSC, the MSC fetches information speci?c to the target device. The MSC queries a database known as the Visitor Location Register, which returns a local copy of the targeted device’s information when it is away from its MSC then forwards the text message on to the appropriate base station for transmission over the air interface. A diagram of a mobile phone work is depicted in Figure , followed by a simpli?ed SMS message ?ow in Figure . Figure SMS Network Figure Simplified examples of an SMS Network and message flow Wireless Delivery The air interface is divided into two parts the Control Channels (CCH) and Traf?c Channels (TCH). The CCH is further divided into two types of channels the Common CCH and Dedicated CCHs. The Common CCH, which consists of logical channels including the Paging Channel (PCH) and Random Access Channel(RACH), is the 畢業(yè)設(shè)計(jì)（論文） 外文翻譯 8 mechanism used by the base station to initiate the delivery of voice and SMS data. Accordingly, all connected mobile devices are constantly listening to the Common CCH for voice and SMS signaling. The base station sends a message on the PCH containing the Temporary Mobile Subscriber ID (TMSI) associated with the end destination. The work uses the TMSI instead of the targeted device’s phone number in order to thwart eavesdroppers attempting to determine the identity of the receiving phone. When a device hea
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