The wireless network operates very much like a typical in-home wireless network with a few modifications. In fact, because this hardware is so widely available, it’s ideal for use in our network. What follows is a slightly technical overview of how our network is constructed.
If you go to your typical electronics store, you’ll see a lot of hardware these days that let you connect your computers in your home together using small radio transceivers. These transceivers utilize a digital wireless radio communications standard called IEE 802.11. Different flavors of this format are avialble, such as 802.11a (5 GHz), 802.11b, 802.11g ( both 2.4 MHz ), and so on. Our network uses 802.11b for its access points, and 802.11a for its backbone.
In a home wireless network, there are two ends of the wireless link; the first is called a Wireless Access Point (or simply AP), which acts as the host of a wireless network to send and receive signals from one or more clients. The AP is special in a wireless infrastructure network because client radios can connect or "bind" only to it. Although a AP technically only needs one computer wired to it, many of the AP’s you find these days typically have a router built in, which allows multiple computers wired to it to communicate with each other and share a single gateway to the outside world, routing information efficiently between the connections.
Some APs also contain a firewall. A firewall is a device that connects two networks together and only allows network traffic to pass from one side to the other based on certain rules. The rules generally deny unsolicted data onto your network while allowing request/response traffic from your computer. A local area network (or LAN) on such a router consists of all of the computers connected locally; either those directly plugged into the device or those bound wirelessly through the airwaves of its AP. A wide area network ( or WAN ) constitutes groups computers that are connected together, such as the internet. The firewall examines traffic to and from the LAN and WAN networks and passes traffic between them that meet the firewall rules.
Although you can get APs, routers, and firewalls as separate devices, we recommend the use of a single device that does all three - this allows for the best interaction of the three components and makes managing the network simpler.
The second piece of equipment is called a Wireless Client, or Bridge. The Client is a radio that binds to an AP and passes traffic to/from the AP's connection to a wired connection on the bridge. It is a bridge in the sense that ties two wired connections ( on the client and the AP ) through a virtual wire - the airwaves.
Your typical in-home APs and clients have radios with rubber omni-directional antennas that have limited range, much
like walkie/talkies. The range of these devices is about 1000 feet into 360 degrees of coverage ( hence omni-directiona ).
However, if you were to narrow the beam you would increase its range. For example narrowing the beam from 360 degrees to
36 degrees results in a theoretical 10 times range of 2 miles.
This is exactly what our wireless network does. The AP in our case is an omnidirectional antenna placed in a visible area that communicates with all the narrow beam clients that bind ( or uplink ) to it. We have several APs scattered throughout the area at various vantage points to blanket the coverage area. The APs that you bind to in our network are a bit more sophisticated than a traditinal AP because they also have another radio that relays ( or downlinks ) the signal to the land based connection to the internet.
At your house, the normally low-powered client antenna is replaced with an efficient rooftop version that points directly at the access point. In most cases, a single rooftop device can be mounted on a mast that contains both the antenna and wireless client in a single weatherproof mounted case. A special device also provides power on the same cable as the data called a power over Ethernet ( or PoE ) so you only need to run a standard CAT5 cable from the roof to your computer room.
Inside the house, we highly recommend the use of a device that allows you to share your connection between other computers in your house. Most devices you can find today are under $50 and combine routing and firewall functions in a single box. If you are planning to use a wireless laptop in your home you can usually get that also in the same box, such as a LinkSys WRT54G.
This type of wireless network has an advantage over wired connections because the bandwidth and backbone can expand as the membership expands. This opens up new access points along the way further blanketing the coverage. We can typically reach members at distances of 10 miles with speeds typically in the 3-4 Mbps range. Atlhough the APs can only communicate in one direction at a time ( half duplex ), the can combine information from multiple clients in its traffic load to the backbone allowing speeds within the backbone of 20 MBps or more. By properly distributing the bandwidth to the backbone we can minimize effects of everyone sharing a single internet connection, especially when the connection is about 20 times the speed of any any client radio. This also allows two computers on our network communicating directly with each other to utilize the full speed of the backbone ( pending the limitations of the client radios ).
At the end of the network backbone is our dedicated internet connection, or gateway. All APs relay through their respective downlinks to a dedicated AP at the site of the gateway. A the gatweay and additional firewall is installed that keeps all machines in our network hidden from the outside world through a process called Network Address Translation ( or NAT ). In rare cases where you might want to have computers on the internet directly access your computer ( such as web hosting ), and we can provide a fixed IP address that maps a specific address on the internet directly to your router. In most cases, however, members will not be aware of the firewall's existence nor should they need to have a fixed IP address. One specific advantage of this firewall is that you will not be solicted by other machines on the Internet without your consent, such as port scanners a nd other programs attempting to penetrate your personal firewall.