1.1 Overview
With the rapid progress of the computer technologies, owning wireless devices and broadband Internet access is not an expensive enjoyment any more, but a basic requirement.
Wireless devices, such as access points (AP) and notebooks, are so inexpensive that they become more and more popular. Broadband Internet access, such as ADSL or cable modem, is usually charged in “flat rate”, i.e., no matter how much data we send/receive, the ISP (Internet Service Provider) charges us a fixed price periodically.
Since sending/receiving more data incurs no extra cost, we suggest sharing this ability of Internet access through WLAN (Wireless Local area Network), also widely known as WiFi.
Wireless access makes mobility possible and let sharing come true. This is an idea about a sharing group. If we share our wireless Internet access through AP at home, we can enjoy WiFi wherever we find another AP which joins this group in return. Unlike an open WiFi system, anyone can access the Internet without any limit or responsibility. In our platform, the APs must support 802.1X authentication. Fortunately, 802.1X authentication is the most general authentication method built in modern APs. Users should register their accounts in the AAA (Authentication Authorization Accounting) server on the Internet first. When someone wants to access the Internet, the serving AP authenticates the user by querying the AAA server.
We can share the ability of Internet access not only directly through APs, but also through an ad-hoc WLAN. The latter situation requires a notebook PC equipped with two network interface cards (NIC), one for the Internet access and the other for ad-hoc mode connection. Two NICs are already common kits (wired and wireless NICs) for a notebook PC.
When someone connects with our laptop in ad-hoc mode, we use iptables to support the
ad-hoc access control. Unauthorized users will be redirected to the AAA server for user authentication. After authentication, users can access the Internet through laptop.
1.2 Related work
There exist two familiar business models for wireless Internet access everywhere. The first one is Taipei WIFLY city program. The second one is FON WiFi community. Their goals are similar to our system, but we adopt different policies to deploy the service.
WIFLY
WIFLY is an outdoor wireless Internet access service. To construct WIFLY wireless networks, APs serve as transceivers. For instance, mobile devices (notebooks, PDA, smart-phones) equipped with WiFi certified wireless card, or integrated wireless chip (such as Intel Centrino processors) can be properly configured enable users to obtain a wireless link to the Internet through transmission. Taipei city government and Q-Ware Corporation deployed the whole environment and charged for the service. There are two main kind of pricing, one is charged by minutes, 360 minutes cost 300NT, and the other is unlimited usage within 24 hours for 100NT. WIFLY also provide some personalized and integrated value-added service, WiService. Until January 2007, there are more than 4000 WLAN hotspots in Taipei. More than 110000 persons use WIFLY, and 35000 of them are persistent users. Besides general users, Q-Ware actively provides services for enterprise customers, too. [1]
FON
FON is the largest WiFi community in the world now. You just need to buy a FON Social Router, which enables you to securely and fairly share your home broadband connection with other FON members. Then when you’re away from home and you need Internet access, just log on a FON Access Point and you can use the Internet. FON members can be classified into
three types, Linuses, Aliens, and Bills.
FON hopes most of members are Linuses. That means that we share our WiFi at home and in return get free WiFi wherever we find a FON Access Point.
Aliens are people who don’t share their WiFi yet. FON charges them 3USD for a Day Pass to access the FON Community.
Bills are in business and so want to make some money form their WiFi. Instead of free roaming, they get a 50% share of the money that Aliens pay to access the Community through their FON Access Point. They can also advertise their business on their personalized FON Access Point homepage.
FON Social Router equips with access point, NAT (Network Address Translation), DHCP (Dynamic Host Configuration Protocol) and authentication functions. What special is that FON Social Router provides two segmented networks. One is your personal and private network and the other is called visitor or public network. In private network, the ESSID can be any string and the traffic is encrypted by WPA key which is static marked below the router.
We can configure the environment parameters, such as the ESSID of private and public network, of the router only through private network. In public network, the ESSID is restricted to use “FON_” as a prefix, for example “FON_AP”, and this makes visitors easily verify if any FON public network nearby when scanning the WLAN. Then visitors associate with a FON public network and get an IP. When users open the Browsers, unauthorized ones will be redirected to FON web portal. Until login as a FON member, we can enjoy WiFi.
FON Social Router also grants you the ability of bandwidth control and to restrict access only for FON users and specific people you trust. It is called Social Router because you can personalize the page that other FON members see when they log on to your FON Access Point and locate the AP in FON Maps. [2]
Evaluation
The hotspots of WIFLY are all deployed by Q-Ware Corporation. The benefit of WIFLY is that Q-Ware can optimize the coverage area and channel selection of these hotspots easily.
Wireless QoS can be guaranteed possibly. But the deployment cost is relative high.
FON takes another approach, the power of users, to make WiFi everywhere. The cost of bandwidth and APs is divided into users, and it is cheap enough for everyone to maintain it.
Unfortunately, FON leaves users no choice, and only FON Social Router is accepted in FON community.
However, both WIFLY and FON have strict constraints on APs. Only specific APs can be used on WIFLY or FON. The cost of deploying WIFLY is high and FON supports only FON Routers. There is still another general approach to share Internet access.
1.3 Objectives
More and more devices are becoming WiFi enabled. We can connect our notebook PC or PDA to the Internet without any wires; wireless access makes mobility possible. When we move away from the coverage of our home wireless network, we could not access the Internet any more. Internet access sharing is a good idea, and wireless is the right medium because you don’t need to search the network socket. To relax the strict constrains of WIFLY and FON on APs, we consider whether any APs can join the sharing group or not. If we have no AP, we can also share our broadband Internet access through an ad-hoc WLAN. We construct a platform providing Internet access sharing and accounting service for WLAN, including infrastructure and ad-hoc mode access. The more users join the sharing group; the coverage of WiFi will be more completed.
1.4 Summary
The remaining of this thesis is organized as follows. In Chapter 2, we briefly introduce some essential knowledge background about our system. In Chapter 3, we present the details of our system design. In Chapter 4, we show the implementation issues. In Chapter 5, we summarize and conclude our work.