What is WLAN: fusion of WLAN and GPRS

"Digest" WLAN is a rapid development of a wireless access technology in recent years, GPRS is a high-speed packet data exchange technology, WLAN and GPRS technology can be integrated to achieve complementary advantages. This paper introduces the solution to the integration of WLAN and GPRS network, and probes into its authentication, billing and roaming mode.

1 Benefits of WLAN and GPRS fusion

Wireless LAN WLAN refers to a computer LAN with wireless media, which consists of a wireless network card, a wireless access point AP, a computer, and related equipment. WLAN has the advantages of no physical wiring, flexible network, fast mobility, high transmission rate, stable signal, etc., through deploying enough AP to cover a part of the area, users can achieve seamless roaming between these AP. However, a WLAN AP coverage of only dozens of to 100 meters, if the formation of wide-area network has no advantage, it is best for the airport, hotels, cafes and other hot spots to provide wireless access services.

GPRS, as a 2.5G technology, is a necessary phase from GSM to 3G, which makes the existing GSM mobile communication system provide data rate from 9.6kbps to 115kbps, which greatly improves mobile user's mobile data communication ability. For GPRS network, its coverage range is much higher than WLAN, can reach tens meter, but its data transmission rate is low. Therefore, for mobile operators, if GPRS and WLAN can be combined organically, fully utilize the wide coverage ability of GPRS network, can make up for the lack of WLAN coverage while ensuring the uninterrupted connection between users and network. In the hotspot area, the high data transmission rate of WLAN is used to make up the disadvantage of low data transmission rate of GPRS network. At the same time, because WLAN is the development of LAN technology, and there is no complete authentication billing mechanism, for mobile operators, to use WLAN to provide a wide range of access services, can make full use of mobile communication network authentication billing system, protect existing investment, truly achieve complementary advantages. (Computer science)

WLAN and GPRS fusion schemes have two kinds: loose coupling and tight coupling, they have different advantages and disadvantages, the following are described. Because currently in the domestic application of WLAN products are most of the following IEEE802. 11 Standard products, therefore, the following discussion of WLAN standards in IEEE802.11 as an example.

2 Loose coupling fusion scheme

Loosely coupled WLAN does not connect with the GPRS core network CN, but directly through the GI interface access to the outside part of the data network, the schematic diagram shown in Figure 1. Figure 1, SGSN for the service GPRS support node, mainly for mobile platform to complete the mobility management, security features, access control and routing functions. GGSN is the Gateway GPRS Support node, is responsible for providing GPRS PLMN and external packet data network interface, mainly complete routing, address assignment, Gateway, protocol conversion, security and other functions. CG for the Billing gateway, the main completion of collection, storage, transfer billing information and other functions. BG for the Border gateway, the main completion of PLMN between different GPRS network functions.

GB is the interface between SGSN and base station subsystem, GS is the interface between SGSN and MSC/VLR, SGSN sends mobile user's position information through GS to MSC, and receives the paging request of MSC; GR is the interface between SGSN and HLR, SGSN obtains the user information in HLR through GR, the GC is the interface between GGSN and HLR, GP and GN are the interfaces between two GSN, but GN is connected with two identical plmn,gp connected by two different plmn. GI is the interface between the GGSN and the external packet data network. Um is the air wireless interface.

In the loosely coupled scheme, WLAN is the supplement of GPRS access network, and the connection controller is completely independent. WLAN can use the same user database with GPRS, but there is no data interface with GPRS, that is to say, WLAN bypass GPRS network, directly to the outside part of the group data network. The degree of coupling between the two networks is very low, mutual non-interference, the construction and development of a network generally will not affect another network. In the loosely coupled scheme, the WLAN upper layer protocol uses a variety of standard Internet protocols that do not need to be modified for the protocol stack.

3 Tight Coupling Fusion scheme

In the tight-coupling scheme, WLAN and GPRS wireless access network, through the GB interface direct access to the GPRS core network Cn,wlan data to the outside part of the group data network before going through the CN.

The WLAN's access controller in the tight coupling scheme is connected with the SGSN through the GB interface, which provides a standard interface for WLAN connecting into the GPRS core network, and SGSN the WLAN features, which makes the WLAN a separate base station subsystem. Or you can merge the access controller into the SGSN. In the tight coupling scheme, WLAN and GPRS use the same fixed network resources as far as possible and are independent of each other in the wireless access part. In other words, the WLAN is a wireless access network in this scheme, the use of GPRS network authentication, billing and certification, the upper layer of the protocol operation is GPRS-related protocol, it is necessary to upgrade the WLAN protocol stack, and increase the interface between the GPRS protocol stack. In the tight-coupling scheme, users can realize seamless switching between WLAN and GPRS network by using two-mode terminals, and for GPRS core network, the user switch between two networks is equivalent to two separate cells.

Comparison of 42 kinds of schemes

The advantages of the loosely coupled scheme are:

WLAN and GPRS network are independent and do not affect each other.

The technology requirement of realizing two network fusion is low, and there is no need to upgrade and transform the existing network equipment greatly.

No special requirements for mobile terminals, ordinary WLAN terminals can also be connected.

Wide application, not only suitable for WLAN operators owned by the situation, but also applicable to WLAN for third-party operators have the situation.

The disadvantages of the loose coupling scheme are:

When the user adopts the dual-mode terminal, the mobile IP must be adopted in order to realize the handoff between the two networks, and the continuity of the conversation is not guaranteed, which is not suitable for the service with higher QoS requirements.

Only one authentication server is shared between the two networks, with a low degree of integration.

The different business zones cannot share the load with each other.

Network management is very difficult.

The advantages of tight coupling are:

GPRS network can be shared with a variety of resources (such as core network resources, certification and billing system, etc.), to protect the investment of GPRS operators.

A unified access server can be used to provide access services for two networks, which can be easily extended to both networks.

When using the dual-mode terminal, the user can realize the seamless switching between the two networks, ensure the continuity of the conversation before and after switching, and support the QoS better.