Interconnection between 3G networks and wireless LAN Based on Softswitch Technology

After analyzing the structure of the softswitch network, this article describes the hierarchical structure of the UMTS Release5 network, which reflects the application of the softswitch concept in 3G. Combined with the wireless LAN mode, 3G and WLAN Integration solutions are discussed.

In recent years, the Softswitch technology has become the focus of public attention and will become the core technology of next-generation networks. The information industry has made great efforts to propose the next-generation IP convergence network, at present, we are actively conducting research on the 3G core network technology, and its ultimate goal is to provide a full IP network capable of integrating multimedia services. In this regard, 3GPP has played a major role in proposing the structure of the IP Multimedia Subsystem (IMS) based on the Softswitch technology. In addition, the rapid development of the wireless LAN technology and the sharp reduction in prices, from the original Supplementary cabling methods of enterprises and homes to the increasingly important public wireless interconnection mode. The interconnection between 3G and wireless LAN fully reflects the advantages of softswitch in the next generation networking technology. This article will discuss this point of view.

1. Softswitch Network Structure

Figure 1 shows the general hierarchical structure of the softswitch network. The access layer supports various types of terminals, which are equivalent to the user-network interface function of the softswitch network. The transport layer is responsible for the end-to-end transmission of communication media information, corresponding to the next layer of the network. The control layer is responsible for call control and corresponds to the Session Layer function of the network. The main device of this layer is the softswitch system.
(SSW) is equivalent to a switch in a traditional communication network as the core device of the network. The service layer provides value-added services based on the capabilities of the lower-layer network and corresponds to the application layer functions of the network.

2G Network Structure

3G networks are the future direction of wireless communication. An important goal of 3G networks is to provide voice services and diversified multimedia services in the form of VoIP, and to achieve the convergence and unification of 3G core bearer networks and IP networks. The convergence of 3G networks and IP networks not only improves the utilization of network resources, but also allows mobile terminals to conveniently access and enjoy information and services on the Internet through a Unified IP network.

As a part of NGN, the evolution of its architecture is also affected by the Softswitch technology. Because its core network uses the full IP Mode for carrying, this ensures that the full IP address core network of 3G can be effectively integrated and interconnected with the NGN core network. According to the hierarchical model of the softswitch network function, the 3G network can be divided into four layers, that is, the access layer, transfer layer, control layer, and service layer. The following uses the mobile network structure UMTS Release5 developed by 3GPP as an example to analyze the location of the main functional entities in the core network's electrical path domain and IP Multimedia subdomain in the layered model 2. Because the group domains in the UMTS Release5 reference model are not constructed according to the softswitch concept, the main functional entities in the group domains are not listed in the layered model in Figure 2. From the layered model, we can see that MGCF (Media Gateway Control Function), CSCF (call status control function), and MSC server (mobile exchange center Server) are logical function entities at the control layer, the call control function is used to establish and release call connections and implement different networks (such as GSM, CDMA, PSTN, UMTS networks of other carriers, and IP multimedia networks). The MGW (Media Gateway and CDMA network) bearer channel is transformed into a function suitable for IP network transmission. It should be noted that both the IP Multimedia subdomain and the circuit domain have MGW functional entities. In terms of function implementation, the MGW in the IP Multimedia subdomain and the mgw in the electrical domain are the same device. For the sake of clear network structure, MGW in the circuit domain can be expressed as CS-MGW, MGW in the IP Multimedia subdomain can be expressed as IM-MGW, SGW is mainly responsible for translation and conversion of the signaling protocol on the IP network side and the signaling protocol on the circuit exchange network side (signaling 7. MRFP (Multimedia Resource processor) and MRFC (Multimedia Resource Controller) are logical functional entities that implement multi-party call and multimedia service provision and control in the 3G core network. In the core network layered model, MRFP is a logical functional entity in the access layer, which provides and carries multimedia resources. MRFC is a logical functional entity in the control layer, which controls multimedia resources in MRFP.

From the layered model of the core network, we can see that the 3G core network achieves the separation of control, bearer, and business. Therefore, we can say that the UMTS Release5 network is actually a next-generation mobile network constructed based on the Softswitch technology.

3 wireless LAN

In the current WLAN market, 802.11b is dominant in terms of its mature technology, compatibility between devices of different manufacturers, and compatibility with 802.11g, the basic extension structures of 802.11b standard public WLAN networks include peering interconnection, AP structure, and wireless bridge structure. The following describes the structure of an access point. 1 and 2.

A typical WLAN topology has an access point structure and is suitable for wireless access services. In this structure, access points are used to perform synchronization and coordination, forward data packets, and connect to upper-Layer Networks. The number of users that the access point can serve depends on the products provided by the vendor. Although theoretically supports many users, in practice, only 15-50 users are supported. This is because an AP can only access one end user at the same time. When the channel is idle, it will compete with other terminals. If an AP supports too many users, the network access rate will decrease.

4 3G and WLAN Integration Solution

In terms of WLAN system equipment and network, it is combined with mobile technology with high-speed mobile performance and a larger coverage, in the public access zone, WLAN provides users with a cheap and higher bandwidth, the so-called "nomadic" wireless data service, in other locations, the real "Roaming" wireless data services provided by the 2-and 3-generation mobile communication technologies are booming. Currently, various mobile communication device manufacturers provide different degree of integration solutions.

Based on the closeness of integration with mobile communication, such solutions can be divided into two categories: loose coupling and loose coupling. The following describes the tightly coupled solution. 3.

In the tightly coupled solution, standard interfaces in mobile communication are used to emphasize the full integration of mobility, business, and application layers, it fully embodies the ultimate goal of 3G and WLAN Integration-integration of services and applications. In the current 2.5G/3G and WLAN loose coupling solutions, users can only obtain two modes, they are unified billing and user management, and WLAN Access Control and billing based on the 3GPP system. Of course, the convenience and consistency of user experience is the most important prerequisite for successful integration. Therefore, the 3G and WLAN tightly coupled solution supports seamless integration of group domain service switching, and is currently in the leading position in the industry.

The solution in Figure 3 uses centralized signaling and billing management. The distributed traffic forwarding method builds a distributed SGSN function for the WLAN Access Network, the network element is connected to the Location Register (HLR) through the standard Gr interface to support the above authentication process and user management. There are no special requirements for 2G, 3G, and HLR. On the user side, the SIM card can be built into a WLAN card that supports SIM or read from a standard USB card reader.

Billing is another important part of the user experience and a concern of operators. Billing by traffic and content is what carriers and users want. The preceding solution not only combines bills, but also incorporates WLAN billing into the 2.5G/3G Billing System to directly provide CDRS that comply with the 3GPP standard, the two billing systems are truly unified on one platform.

In addition to the duration and traffic fees that comply with the CDRs standard, the above scheme also supports rate switching. It also constructs a distributed SGSN function, and connects GGSN with the standard Gn interface to obtain 2.5G/3G standard mobile data services, such as wireless VPN applications, security and value-added billing.

5. Summary

The Softswitch technology has become the core technology of 3G. It enables 3G to develop towards a full IP group network with integrated multimedia service capabilities, making it possible to tightly couple WLAN with 3G, it not only enables the WLAN to conveniently use Internet resources through the 3G network, but also allows the WLAN to communicate with other terminals on the 3G network. The WLAN serves as a supplement to the 3G network in the enterprise, promote the development of mobile commerce users, and attract WLAN enterprise users to 3G networks through better mobility and security.