Entry-level information for Microwave-based Amateur Wireless Computer Networking

Be aware that 'amateur' computer wireless networking is not capable of replacing someone's everyday access to the Internet. For one, third-party traffic (i.e. Internet access) is illegal over unlicenced transmitters in Australia. It is not secure. There are legal and practical limitations on its availablilty, effectiveness, and reliability. (Think of it as AM CB radio for computers-- and anyone with experience with that scene will know of the problems they're up for.) And don't even think about it unless you possess a thorough knowledge of computer and radio networking-- don't expect competency with off-the-supermarket-shelf software products to be enough; for starters, you'll need to operate a Unix system like Linux, NetBSD, or FreeBSD (Windows/NT can't cut it, and dedicated wireless equipment is very, very, expensive and pointless) has a network router.

The greatest annoyance, however, is the number of people who expect to be provided with 'very cool turn-key wireless solutions' so they can browse the web at faster-than-cable speeds. Sorry, but you'll soon discover than I become quite surly if you contact me and show no interest in self-education. Ideally, you will investigate all this by yourself and then approach me so we can try to get a point-to-point connection happening.

The following information will be invaluable for those starting out:

My Equipment

The foremost bit of gear is of course the two Lucent 'Bronze' WaveLAN PCMCIA cards (photo). Purchased years ago from Xnet for ~$110 each. In practice on a point-to-point 2Mbps link, the transfer rates are up to ~170 kB/sec, and the round-trip ping time is 5-9 milliseconds (I can live with that..) I currently operate the cards in 'ad hoc' mode, in which they behave much like Good Old Ethernet, however I believe this mode is incompatible with other vendor's products.

Using the internal aerial, I've found the cards have a range of up to ~100 metres. I've yet to properly measure the range of the "Heckler Helicals" I've built (photo), but during a quick test, with both aerials resting on the ground they did okay at 900 metres. (For best results, they of course should be on a mast at least 10 metres above the ground, where they'd expected to give a range of up to 10 kilometres with good line-of-sight.)

One card is currently used by a 486 laptop, "stoat.air", that runs NetBSD-1.5.2. The other is set into a PCMCIA to ISA adaptor (cost $150) inside the NetBSD-current pentium system "weasel.air", that I put together specifically for wireless work. Unlike with Linux, the "wi0" driver in NetBSD is a formal part of the kernel and so avoids the hassle of patching whenever a new Linux kernel arrives (and is the OS I use on my other systems, anyway). "Weasel" provides name service, firewalling (bind and ssh are the only connection types allowed-- everything else has to be tunneled through ssh), routing to the house LAN, a news-server, and a mail smarthost-- it was a system I prepared as a 'wireless member access system' when I was living in Armidale, before the other people lost interest because the WaveLAN drivers wouldn't work with Windows2000...

Necessary for any long-distance connection are adaptor connectiors ("pigtails') to wire the cards to a decent aerial. Due to limitations placed on the American manufacturer of most wireless cards by their FCC, the aerial connectors must be proprietary and difficult to acquire, to discourage any J. Random Nerd from bolting a random aerial to their cards and causing interference to legitimate users. In Australia, about the best sources of MMCX to N-plug adaptors sell theirs for ~$70 each. I have two. (Note: as of 2003, they can be bought for $40.)

The final bit of gear, which I've yet to acquire, is a suitable length of 2.4GHz low-loss coax, like C2FP or LMR400 (the WaveLANs have an impedence of 50 ohms-- another deliberately non-standard design decision). That stuff costs about $10 a metre, so I'm leaving that until I have a proper aerial mount in place.

Wireless Networking Intentions

Of course, the goal is not to provide Internet access. Having 20 or more people all trying to use a shared 2 or 11 Mbps link to download warez at the same time ain't gonna work. However, not 'doing Internet' allows the opportunity for experimentation with ideas that are difficult to use effectively on the Plain Old Internet, like native IPv6, inherently secure networking, efficient channel utilization, and playing with other developments that have been pushed aside because of the IPv4/WWW bandwagon.

However, while being a 'Wireless ISP' is out of the question, it is permissible for wireless to 'bridge' networks within an organisation-- i.e., an APANA member is allowed to use it to connect to the APANA/Hunter LAN. (At least, that's what the language in the ACA class licence for low-powered 2.4GHz wireless networks is understood to mean.)

It's also cool to once again have a computer-related project that involves hardware, just like in the good old days when all computer enthusiasts owned soldering irons. :)

Photo Gallery

Here, let me show off a little bit. (With what I've been able to accomplish by myself, anyway..)