The system has been designed to be scalable, and easily upgradeable to cover a wide area at a low cost. With this purpose we selected a multi-tier approach where all the subscribers are connected to the Internet through a main server which acts as a gateway to the Internet. RuralNet combines three different interconnected tiers (a) a wireless mesh distribution network, (b) a backbone wireless/wired network, and (c) a top level management system. This approach allows creating a scalable network which is able to cover a vast area, connecting the main server with all the clients within range of any of the APs deployed. We base our solution on Linksys WRT54G wireless routers, which operate using IEEE 802.11 technology on the 2.4 GHz frequency. The next figure shows the overall system architecture.
Arquitecture
- Ruralnet core. The top level management system is composed by a server that controls user authentication, and where all the software required supporting the system is stored. The main software components are a web server to interact with the subscribers, a database used to store system information, and a control unit that converts management decisions into traffic rules. Besides, the server has also a high-speed connection to the Internet, along with a wireless or an Ethernet connection to the backbone network.
- Backbone network. This second level is composed by a group of nodes distributed in the operative area, composing a mesh network. These nodes are connected to the main server and to other nodes through either Ethernet or IEEE 802.11 technology. Wireless connections are preferred since they can benefit of antennas to achieve increased range at little cost. The main purpose of this level is to work as a bridge, connecting subscribers to the main server.
- Distributed Mesh network.The distribution network is composed by several wireless routers representing neighboring rural areas, which are hierarchically grouped to form a mesh network. To implement the mesh network each WRT54G router at the distribution level activates the Ad hoc On-Demand Distance Vector (AODV) Routing protocol or the Optimized Link State Routing Protocol (OLSR). Both protocols are simple and efficient routing protocols designed specifically for use in multi-hop mobile wireless ad hoc networks. By using routing protocols the coverage area can be easily extended since the network is completely self-organizing and self-configuring. Moreover, since the route used to reach any destination may change over time, the resulting network topology is frequently changing.
RuralNet interacts with clients through Captive Portal technology. Therefore, when one client first connects to the system and opens a web browser, he is automatically redirected to the main page of the portal; this process is completely transparent to the user. The management server controls client access depending on whether he is a registered user or not. Depending on the client's access level, different services will be provided. The first time a client accesses the system he is asked to register himself with the Captive Portal. After a login process the user can use any of the freely available services, like Internet access. Concerning the Internet access service, the system allows to choose among multiple connection speeds.