Short message business design and implementation in mobile softswitch
Dongning Susen Beijing University of Posts and Telecommunications, 100876 1 Introduction UMTS (Universal Mobile Tele Communications System) system is a third-generation mobile communication system using WCDMA, and its standardization is organized by 3GPP (3rd Generation Partnership Project). Four versions have been launched so far, that is, the UMTS system specified by R99, R4, R5 and R6.3GPP. Starting from the R4 version, the biggest change in the core network is to introduce softswitch in the circuit domain, will control And carrying separate, the original MSC changes to the MSC server and media gateway MGW (Media Gateway), and the voice is transmitted by the MGW by the packet domain. Soft exchange is the core technology of the next-generation network (NGN, NEXT Generation Network), providing call control and connection control functions for services with real-time requirements for the next generation network, and is the core of the next generation network call and control. Mobile softswitch is a new direction for the development of softswitch technology. Mobile Softswate is the application of softswitch in mobile communication network, which is also a new trend of soft exchange technology. As a short message service as one of the main business of the mobile, in view of its huge economic interests brought by operators and developers, it has become necessary to support the implementation of mobile soft exchange. A business. Hereinafter, the mobile softswitch support for mobile networks will be specifically described as an example of a short message service. 2 Short Message Realization Principles 2.1 Business Definitions Short Wave Saute Two Categories: Community Broadcast Short Message (CBS) and Click to Point Short Message (SMS). Generally mentioned short message services are mainly guidance to point short messages, such as non-special declarations in this article, all specifically directions to a short message. Short messages are not required to establish an end-end business path in GSM / UMTS. Short message transmission can be made even if the mobile station is already in full circuit communication. Usually short message communication is limited to one message, in other words, the transmission of a message constitutes a communication. Therefore, the business is asymmetric, generally believed that the mobile start short message transmission (SM-MO) and mobile termination short message (SM-MT) transmission is two things. This does not hinder real-time conversation, but the system believes that different messages are independent, and the transmission of messages is always relayed by the business center (SC) outside GSM / UMTS. The message is destined or the origin, but only is related to the user and SC, but has nothing to do with other GSM / UMTS infrastructure. The SMS provides a means of transferring short messages between GSM / UMTS MS and SM. The SC is responsible for the interoperability and relay functionality between MS and SME. 2.2 Network Architecture Short Message Service In the mobile communication network implementation, it mainly involves a protocol between the wireless access section, the internal and core network entity between the MSC. Link 1 includes a wireless air interface and an IU interface (A interface in GSM), where the Iu interface uses the RANAP protocol; links 2 and 3 belong to the mobile core network, which uses the MAP protocol. Link 4 is the interface between the mobile network and the short message center SC, which protocol is specifically used by the operator. 2.3 Protocol System (1) The RANAP Short message is transmitted from the RNC through the RANAP protocol to the MSC Server (Softswitch Entity). Ranap is the IU signaling protocol, which includes all control information specified for the wireless network layer. The function of Ranap is implemented through a variety of RANAP basic processes (EPs).
Each RANAP function may require a plurality of EPs, each EP, or a request response message pair (1 class EP), or only the request message (2 class EP), or contain a request message and one to multiple answers Message (3 class EP). Short message PDU (Protocol Data Unit) transfers from RNC to MSC from the RNC through the Ranap's UE-CN signal. (2) The MAP Mobile Application section (MAP) protocol is a protocol designed for mobile communication requirements. Map above TCAP corresponds to the seventh floor of the OSI reference model, is the application layer protocol of Seventh Signaling. MAP only uses SCCP no connection. This protocol is used in communication between MSC, HLR, VLR, and EIR: position registration; location deletion; cancel registration; user service processing, management, and retrieval; user parameters (ie HLR and VLR updates); switch ; Transmission of confidential authentication data, etc. MAP is a user of TCAP, using exchange protocol data and session, processing MSC, HLR, and VLR to communicate with the same layer between different entities such as MSC, HLR, and VLR. A series of functional blocks included in MAP are called application context cells for communication between two nodes equivalent. Sometimes a system simultaneously with several systems, switching is an example. With the MAP protocol, one entity can communicate with several entities. For the support of the short message service, also one of the functions of MAP. Through the MAP message, the short message can be transmitted between the servo MSC and IWMSC / GMSC. (3) The protocol structure inside the MSC Server Since the MSC Server is implemented by softswitch technology, the protocol system in the MSC is implemented by the softswitch technology, that is, the protocol system in the softswitch entity. Compared with the 3GPP 24011 specification, the soft exchange internal short message protocol system is divided into three layers: SM-TP, SM-RP and SM-CP. The SM-TP layer message is used as the user data encapsulated in the SM-RP layer message, and the SM-RP layer message is used as the user data of the RPDU and is encapsulated in the user data of the SM-CP layer message. The last SM-CP layer message is used as a CPDU. Bear bearing signaling such as RANAP signaling is transmitted between different entities. On the core network, since the message of the SM-RP layer and the SM-CP layer has been processed by the MSC, only the message left in the SM-TP layer is transmitted as a bearer signaling on the core network. SM-TP is a short message transport layer protocol. This layer message parameter includes a valid period, a business center timestamp, a protocol identifier, a destination mobile phone user address, and the like, which requires MS and SMC to process. Therefore, for MSC Server is transparent, it is not necessary to care. It can be said that the MSC Server task is to correct the TPDU to SMC or MS SM-RP is a short message relay protocol. The most important thing for this layer message parameter is the user data and the purpose SMS center address. According to the message parameters of this layer, the corresponding MAP message can be generated, and the routing of the short message on the core is performed. Related messages are as follows: SM-CP is a short message control layer protocol. The main function of this layer message is to control the short message flow on the wireless interface to ensure that the short message is transmitted correctly on the wireless interface. 3 Short message implementation scheme 3.1 Soft switching system Softswitch system block diagram, including protocol processing, call control subsystem (Call Control), Call Service , VLR subsystem, service adaptation, and OAM subsystem.
The protocol handling the ML3 in the subsystem represents the processing module that moves the third layer signaling, including 2G BSSAP and 3G Ranap protocol fit section. The protocol handling subsystem communicates with the remote communication entity (including signaling interaction and media interaction) by protocol stack (including signaling interaction and media interaction), and the upper layer module such as call control, the call service shield protocol is different and the online user is maintained. There are corresponding sub-modules for different user access types, such as mobile, ISUP, multimedia, etc., respectively. Call control is communicating with each protocol in the system, completes signaling control tasks, and communicates with call services, obtains number analysis results, routing information, etc. The call service is handled by each protocol in the system, completes the task such as resource management, location management, user information management, and provides services such as number analysis, routing information. The VLR is a user database associated with a mobile, and provides the control function of the RP layer for the short message transmission. Business adaptation is a soft exchange-out business interface, providing business access functions for application servers and intelligent networks. 3.2 Short message The module involved in soft exchange is divided into two hierarchicals for SM-CP and SM-RP due to the short message protocol processing, so we combine our softswitch design. Divided into two parts: SM-CP layer messages in ML3, and the SM-RP layer message is processed in the VLR. The role of this VLR is very different from the VLR in the conventional mobile communication network. In a conventional mobile communication network, the VLR is just the MSC to deal with the incoming call call call in the jurisdiction, the database, stores some of the data related to call processing. In the softswitch implementation, the VLR is outside the above functions, in addition to the user's data, to avoid excessive internal communication flow, we will call the authentication, location update, paging, and short messages in mobile communication. Control of unrelated business processes gives VLR. So this time the VLR has become a control entity for a call-independent business process. SM is the short message protocol processing module in ML3 to implement the function of short message control entity (SMC). When the MO business mode is responsible for processing the SM-CP layer message and decodes the SM-RP layer parameters, forming the SM-RP layer message to the VLR. At the MT service, it is responsible for encoding the SM-RP layer message received from the VLR into RPDU to form an SM-CP layer message to send to the underlying protocol stack. After the short message service process, it also notifies MM (Mobility Management) Release the connection of the wireless interface. The status map of the Alert process is the same as MO. VLR completes the function of short message relay entity (SMR): SM-RP message interacts with the MAP message. According to the received SM-RP layer message, construct the corresponding intermediate message of the MAP state machine, perform the MAP process, the reverse direction, construct the corresponding SM-RP layer message according to the received MAP intermediate message, and perform short message relay . In fact, VLR acts as a short message service process in the wireless access section protocol (RANAP or BSSAP) and the core network protocol (MAP), so that the SM is coordinated with the MAP state machine to cooperate to complete the short message transmission. The MAP submodule completes the transmission and acceptance of the short message service in the core network through the MAP protocol message. When the MO method, the MAP sub-module starts the application context named ShortMsgmo-relayContext, sends a short message to IWMSC; when the ALERT process starts the application context named MWDMNGTCONTEXT, send users to HLR to prepare the message; When the MT method, the MAP sub-module accepts the MAP conversation named shortmsgmt-relayContext called ShortMSGMT-RelayContext, and receives short messages from GMSC. The above process is the standard process defined in the 3GPP 29002 specification. This article will not be described again.
