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Getting Started with community wireless networking



Newbie

You've never used wireless before, you want to exchange data between your laptops at home or work, or get your laptops online through your desktop pc at home.

Build a Client

Buy a 802.11b WiFi certified PC Card (PCMCIA) and plug it into your laptop. Install drivers as specified by your card's manufacturer. You should now be up and running. If you don't have a laptop, you'll need a ISA/PCI adapter to slide your PC Card into, and then plug into your desktop. Congrats, you have now built a wireless client, but it's not very useful without a connection to something is it?

so you'll need to...

Build another client

Build another client, and set both to IBSS Ad-Hoc Mode. When both clients are in range of each other, they should start an IBSS network. If you have enabled file sharing on each computer, or have a FTP or HTTP or any other servers running, you should be able to transfer data between clients. If one client is connected to another network or the Internet, they can share their network/internet connection with all the other wireless clients. Repeat this step for each new client, and it will create a mesh of clients all communicating together.

or...

Get an Access Point

Buy a 802.11b Access Point (AP) and plug it into your wired network. Clients should be set to Infrastructure mode. Now client traffic will first go through the AP, and then to the other clients, instead of clients directly sending traffic to each other.


Medium

You've heard about people extending the range of their wireless network for many kilometers, and want to do the same.

Hopefully the card or AP you bought has an external antenna jack, or a way of hacking one on. Look up your hardware in the HardwareDatabase, and find out if it has one, and if so, what type it is. If the data is missing, you'll have to do some research, and please share what you find out. If you're still reading we'll assume your hardware has a jack.

The first step is getting a Pigtail. A pigtail is a short, thin cable with a microwave connector on each end. The shorter the better. One end is the connector that goes into your card/AP, and the other end is most likely a N-Type male or female connector. The reason we don't just plug microwave cable into the card, is because the card jacks are very small, and microwave cable is very large, and it just won't work.

Now you need some microwave cable. The standard is LMR-400 (CNT-400 is cheaper, but has virtually identical physical and electrical specs). You can't just use any cable because the microwaves will escape and you'll be left with poor signal at the end. There are better (fatter) cables than LMR-400, but they're quite expensive. Nearly everywhere will sell you a cable to a certain length, complete with N-Type connectors on each side. You can do the connectors yourself, but depending on the type of connector, you'll need an appropriate crimper.

Now you need an Antenna. Before you choose an antenna, you need to understand what each type do, and what you need. If you want to share your wireless network with all your neighbors, you'll probably want an Omnidirectional antenna. If you want to make a long link to a guy 5km away, you'll probably want a Cantenna or a Yagi antenna, perhaps even a Parabolic antenna for longer links.

You'll see a rating next to all antenna sold for 2.4ghz operation, in the form of dBi gain. Your stock card antenna's are something like 1 or 2dBi gain. This means it's slightly more focused than an imaginary 0dBi which would be a sphere of coverage. The higher the gain, the more focused the antenna is, and the farther it will go. A 3dBi Omni coverage area is like a very fat pancake coming out of the middle of the antenna. A 15dBi Omni is a very flat disk coming out of the middle of the antenna. It is quite possible for a high gain Omni on your roof to give little to no coverage in the area below it, but it will go much farther than a 3dBi model. 24dBi Parabolics are about as focused as you can get without having a 2 meter dish on your roof. The width of coverage is only about 7 degrees, so it will have to be aimed very precisely. Most antenna come with a N-Type connector on them, so make sure your microwave cable connector matches it.

Now when you plug everything together, your network is extended much farther, and you can connect to people across the street or across the city, assuming there is a good Line of Sight between both people's antenna. Remember, many manufacturers AP's can only talk to clients. You'll need to check to see if your AP supports Client Mode. And even if it does, it's not guaranteed to connect to an AP from a different manufacturer. Most AP's can talk to each other Bridge mode. While in bridging mode, they can not talk to clients, only other bridges.


Advanced

You know this wireless stuff up and down and you want to create a full on long range wireless network.

You'll probably want to setup a dedicated box running a standard Linux distro or a wireless specific build such as the Pebble distro. You've got 2 wireless cards in your box running IBSS mode, one is connected to a 24dBi parabolic pointed at Joe 10km away, and the other is connected to a 15dBi yagi pointed at Fred 3km in the other direction. You've setup packet forwarding in Linux in order to route traffic between Joe's net and your net and Fred's net. You're running a dynamic routing protocol such as OSPF.

You're locally mirroring 100GB of popular data. You're running local HTTP/FTP/SMTP/DNS/DHCP/Quake/CounterStrike/IM servers. You've also got an AP running BSS mode connected to a 8dBi Omni Antenna to give public access to your neighbors and the coffee shop next door, and people in that park across the street. You may even have an Amplifier inline with your AP and Omni to get you up to full legal transmit power.

You have an SIP phone connected to the wireless network, and you're making free phone calls to your friends.

Links to nearly everything mentioned in this article can be found at the External linkwireless anarchy website.

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Version 3 (current) modified Tue, 03 Jul 2007 23:12:01 +1000 by graybeard
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