Mobile switching center is also called mobile telephone switching office（ MTSO )。 The mobile switching center is CDMA The heart of cellular mobile communication system, which controls the lifeline of the system, is connected to other systems (such as fixed telephone network, GSM network, etc.) through CDMA system. At the same time, it also controls base station And the working state of the mobile station to realize the interconnection of mobile users, Mobile station All kinds of soft switching, hard switching, etc. All BTSs have lines connected to the MSC, including service lines and control lines. The MSC sends signals from one or more base stations to the selector and the corresponding Vocoder 。 The selector compares the quality and quantity of signals transmitted from two or more base stations, selects the best quality signal frame by frame and sends it to the vocoder, which completes the selective combination. The vocoder converts the digital signal into 64kb Ⅳ s PCM telephone signal or analog signal and sends it to other users of other networks or local networks. In the opposite direction, when a user's voice signal is sent to a mobile station, first access the vocoder of the MSC, and then connect several base stations. If the mobile station is undergoing soft handover, the switching center sends the signal to the appropriate base station, and then the base station sends it to the mobile station. The MSC controller is connected to the controller of each base station to monitor and control the base station and mobile station. Therefore, the MSC is dedicated Digital SPC exchange 。 [2] In different contexts, MSCs have different names, which also reflects their complex roles in the network. Although all these terms can refer to the same MSC, their respective functions are different at different times.
Gateway Mobile Switching Center (GMSC)
GMSC (Gateway Mobile Switching Center). It can query the current location information of the called MS from the HLR, and select the route according to this information. GMSC can be any MSC or set separately. When set separately, MS calls are not processed. Therefore, it is unnecessary to set VLR , not connected to BSC. [1] Visit Mobile Switching Center (VMSC)
Visited MSC (VMSC for short) is the MSC where the customer is currently located. The VLR associated with the MSC will have the data of the subscriber.
Anchor attached mobile switching center
The anchor MSC is initiated switch MSC. Target mobile switching center
The target MSC is the MSC to be switched to.
Mobile switching center server (MSCS)
Mobile switching center server (Mobile Switching Center Server, or MSCS for short) 3GPP Release 4 At the beginning, it is part of the redesign of the MSC concept. MSCS is a soft switch variant of MSC roam The mobile phone to the area it serves provides circuit switched calling Mobility Management And GSM services. The MSCS function enables the separation of the control (signaling) and user planes (the collective channel in the network element is called the media gateway/MG), thus ensuring a better layout of the network elements in the network. Generally speaking, the advanced functions of MSC include the following aspects:
The MSC can track all wireless users in the system through the automatic wireless registration process, and can continuously monitor the operation of all connected cellular base stations. If a device in the cell has a problem, the MSC will send a notification through the alarm process, and then transmit the alarm information directly to the Network Operation Center (NOC). This is usually done through the operator's own wAN (Wide Area Network). [3] The MSC can handle all wireless system calls, including mobile phone main calls. In this case, the MSC will coordinate with the PSTN for relay capture. At the same time, it also includes the mobile phone making the called call. At this time, the MSC will coordinate and activate the paging function to the local mobile phone. For a mobile phone to be called, the MSC must start the paging function in an area where the mobile station signals have been recorded in the database through the mobile registration process. [3]
The paging function is used by the MSC to locate mobile phone users, so as to connect local calls and mobile phone calls, as well as mobile phone and mobile phone calls. For example, the MSC attempts to locate a mobile phone user by activating call signals in the last 10 cellular sites recorded by the wireless user signal. If no user is located in 10 cells, the MSC will start local paging to locate the mobile phone (that is, in 50 cell sites). If the user is still not located, the MSC will start global paging. At this time, the MSC will send paging signals to all base stations (200~300 cellular sites) in the system. These processes are closely related to operators. This process takes only a few milliseconds. [3]
Call handover is the process in which an MSC switches an ongoing call from one cellular site to another. The call handover function is strictly controlled by the MSC. [3]
User accounting is controlled by MSC. Through automatic message accounting (AMA), MSC can record call data in detail on disk or tape. [3]
Through the MSC's local location registration (HLR) and visitor location registration (VLR) databases, the MSC can track the details of users roaming from one system to another. Once the MSC determines that there is a roaming user in the system, it will instruct to store the accounting information in a dedicated data storage file, and the final roaming list will correctly indicate the fees that the user should pay to other operators. [3]
Traffic and call handling statistics
MSC can collect data of all call processing functions, including traffic statistics such as cellular radio relay group, relay group connecting wireless system and PSTN; And call handover statistics, call failure and maintenance statistics (cellular and MsC alarms). [3]
