Abstract: This paper analyzes the current status of PWLAN roaming development, points out the main problems that PWLAN's "free" feature brings to business operations, and proposes three solutions to these problems, and gives the basic model of WLAN ISP roaming . Finally, suggestions are made for domestic operators to solve the problem of PWLAN roaming.
Keywords: PWLAN, roaming, WISP
Public wireless local area network (PWLAN) is a public wireless network mainly used in hot spots. Unlike traditional cellular networks, it is often deployed as a national network from the beginning, and the frequency of use is subject to policy control. WLAN uses unregulated frequency bands, and different investors often participate in the construction of PWLAN in different hotspots, including owners, independent WLAN access service providers, and traditional telecom operators. Although these "free" features greatly promote the deployment speed of PWLAN hotspots, they also bring important roaming problems to PWLAN operations.
1. Analysis of current status of PWLAN roaming development
At present, the "free" feature of PWLAN brings the following problems to business operations:
Different hotspots belong to different service providers, causing users to apply for services to multiple service providers and settle accounts separately when accessing different hotspots;
The frequency is not regulated, and the construction of hotspots is similar to the "enclosure movement". It is difficult for an operator to fully cover the hotspots where customers often stay;
Different service operators support different service attributes and access authentication methods, and different hotspots may require different client software.
It can be said that the PWLAN market is currently in a highly fragmented state. In the process of moving to a mature market, it is necessary to solve the problem of roaming between different service providers and the ability to provide users with service packages. In this process, traditional telecom operators, especially mobile operators, have their own advantages. The rich roaming experience they have accumulated in the operation of wireless networks has an important reference role in solving the roaming problem of PWLAN.
At present, the working frequency band of WLAN is unregulated. In the future, there will be various wireless Internet service providers (WISP) entering the ranks of PWLAN service providers. As mobile virtual operators (MVON), they have their own hot spots and different services In order to facilitate users to enjoy services in hotspots of different WISPs, it is necessary to establish a unified accounting and management mechanism, so that the global roaming mechanism composed of WISPs came into being. American WISP and WLAN equipment manufacturers together form the WISP alliance PAss-One, whose purpose is to promote the development of the PWLAN market and promote the establishment of a global PWLAN roaming mechanism. By establishing a roaming mechanism, PAss-One member users can use all other members' PWLAN devices to access the Internet wirelessly at the same time.
China Netcom's WLAN network, which already occupies a large number of domestic commercial office buildings, airports, convention centers, and other hot spots, is currently using the Asian Wireless Broadband LAN Alliance as a good platform to expand its wireless broadband network coverage. In March 2003, China Netcom, Korea Telecom (KT), Malaysia ’s MAxis, Singapore ’s StArHub, and Australia ’s TelstrA formed the world ’s first wireless broadband network alliance. So far, the five alliance member operators WLAN wireless broadband network has been deployed and provides services in 8,600 places including 17 international airports, and their users can access the network in these places. Currently, other large operators interested in joining the alliance are in active negotiations with them. With the rapid popularization of wireless broadband network hotspots worldwide, the alliance will expand to more countries.
2. PWLAN roaming solution
Usually the roaming problem includes two aspects: one is the roaming within the operator ’s PWLAN system, that is, users can access the network in hotspots at different locations of the same operator; the other is roaming between different operators, that is, the user can Enjoy services across hotspots of different operators.
Generally, when a user roams to the visited network, the visited network does not have the user's data. Therefore, how to authenticate and charge the visited network is usually the first roaming problem to be solved by operators. There are three specific solutions:
Solution 1: User data sharing
The feature of this solution is that the visited network and the home network share user data, thereby solving the problem that the visited network has no user data. After user data sharing is realized, the visited network treats roaming users as if they were local users. The advantage of this solution is that the principle is simple. All AAA servers that implement local authentication and accounting can implement roaming authentication and accounting through this solution. The disadvantage is that the workload of data synchronization is too large. With the increase of AAA servers, data synchronization The difficulty increases in geometric order, so this solution is not suitable for roaming situations with more AAA servers. This solution requires that AAA servers can share user data and have user data synchronization interfaces, so this solution is also not suitable for roaming between different operators. This solution is only applicable to roaming when several AAA servers are built by the same operator, and these AAA servers are provided by the same equipment vendor, and the same user data synchronization interface is supported between the equipment.
Solution 2: Fuzzy billing in the visited area
The feature of this solution is that the visiting place charges roaming users according to certain fixed rules. The disadvantage is that the home operator cannot set and adjust the charging strategy for roaming users. The charging rules are too single, and authentication methods need to be passed through other methods. Solution, so operators generally do not use this model.
Solution 3: Proxy message
The feature of this solution is that visiting the AAA server acts as a proxy and does not directly authenticate and charge the roaming user, but routes the message to the AAA server to which the roaming user belongs for authentication and charging. This solution is a common practice in the industry.
The basic model of WLAN ISP roaming is shown in Figure 1.
(1) Home network ISP
The main function of this part of the network is to provide authentication, authentication and authorization of its own WLAN users. When an operator manages its own users, there are two main ways:
Operators can adopt the common broadband user management mode, that is, management through the AAA server, and users are authenticated through "UsernAme + PassWord". This mode of operation is widely adopted by fixed-line operators;
The operator can also be managed through the mobile customer management mode. In this case, the operator needs to add an access server (AS) device to store the data stored in the home location register (HLR) and service control point (SCP). Mobile customers are open to the WLAN network, making WLAN user authentication and charging models consistent with the traditional model of the mobile network. In this mode, the user authenticates through the SIM card. This type of operation is also widely adopted by mobile operators.
In the above mode, no matter users use the home operator WLAN network or roam to other ISP networks, they will access the home network AAA and AS through the standard Radius or EAP over Radius protocol. Therefore, the external interface of the home network ISP will be standard Radius or EAP over Radius.
(2) Roaming agency organization
The main function of the International Roaming Alliance organization is to provide roaming agents between different countries, cities, and ISPs. As long as operators sign roaming agreements with the organization, they can achieve roaming and interworking with thousands of other ISPs.
Technically, this type of network mainly realizes the interconnection with ISPs through Radius and EAP over Radius protocols, and performs routing addressing of different ISPs through different domain names, and user authentication and accounting information from Radius Proxy or EAP over Radius Proxy The transmission from the roaming ISP to the home ISP can fully meet the needs of WLAN operators for roaming and interworking.
(3) Visit the Internet ISP
The main purpose of the visiting network ISP is to realize the access of WLAN users in the roaming area. In terms of the specific user access method, you can use Web, PPPoE, PPP over EAP, 802.1x and other access methods. The visiting network ISP can directly communicate with The home network ISP is connected, and can also be connected to the home network ISP through the "roaming agent organization". The interworking here also uses the Radius or EAP overRadius protocol.
In order to ensure that the visiting network and the home network can operate accounts and settle accounts, the visiting ISP network needs to have a Radius Proxy entity to store sufficient user online information for settlement between ISPs.
3. Suggestions for establishing PWLAN roaming collaboration and alliance
At present, domestic operators are still in their infancy in the roaming of PWLAN. It is technically not difficult to achieve roaming between different APs or sites of the same business service provider and connect the PWLAN outlets that have been deployed by the operator. But to completely solve the roaming problem, operators also need to achieve interoperability with other operators 'PWLAN, that is, support their own PWLAN users to roam to the Internet through other operator's networks, and support other operators' users to roam to their own networks. Specific solutions Can be achieved through the above three ways.
Since the solution of cross-operator roaming involves coordination of accounting standards and commerce, it is very difficult. Operators may need to rely on third-party mechanism guarantee or industry coordination to complete. To this end, collaboration alliances and roaming intermediaries (that is, service providers specializing in providing interconnected roaming services) specifically for PWLAN roaming have emerged. Domestic operators can use these services to implement PWLAN roaming between each other. The specific ways are as follows:
Sign a roaming agreement with other operators individually, negotiate the billing model and settlement mechanism of both parties, and the core of the negotiation is the way of sharing with other operators;
Participate in PWLAN roaming alliance or roaming collaboration activities, and use this covenant platform to realize roaming with wireless PWLAN hotspots of all members of the alliance as soon as possible;
Participate in some roaming intermediary organizations, and roaming intermediary service providers provide roaming services in a unified manner, in which technical connections, settlement, accounting and other links are handled by roaming intermediaries. Currently, more well-known roaming service providers include iPASS and GRIC.
In short, the roaming problem of PWLAN is a very necessary and imminent thing facing domestic operators. No matter what kind of roaming collaboration method is adopted, such as signing a roaming agreement with other operators individually, or providing services by a special roaming service provider, no matter how cumbersome and complicated the roaming cooperation negotiation is, such as negotiating and regulating the WLAN pricing model of each WISP and debit Mechanisms, etc., roaming services must become one of the network functions of domestic operators WLAN, and it is a matter of immediate action.
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