WaveLan
This page is archived from sinister.com,
written by DrWho
WaveLan is a copyright
of Lucent, and is their name of the wireless ethernet product line that
was first an NCR product and then and AT&T product. It is also known
as the DEC RoamAbout.
The WaveLan comes in ISA, MCA, PCI, and PCMCIA versions. I believe
that the MCA version is no longer in production. They operate on two bands:
915 Mhz and 2400 Mhz, using Direct Sequence Spread Spectrum (DSSS).
Spread Spectrum is a relatively new and somewhat complex radio
technology that involves spreading the signal out of a wide portion of
bandwidth, the original signal is mixed with a larger pseudo-random sequence.
The receiving end strips away the pseudo-random sequence and "votes"
on the results, majority winning for that bit. The result is a modulation
method quite impervious to interference, either natural or man-made.
The WaveLan operates at 1.5 MBPS, half-duplex, in a carrier-sense multiple-access
environment. It is license free, operating under the FCC Part 15 rules
limiting power output and antenna height for such devices. Typically, a
small "rubber duck" antenna is attached to the back of the device.
However, with a decent antenna, such as a 10 element beam antenna, extending
its range far beyond the 800 ft. it normally has. It has been used as an
internet backbone in Latvia.
Distances over over 6 KM have been achieved, using high-gain antennas,
and with direct line-of-site orientation.
Problems with the WaveLan:
- Cost - The retail cost of these cards is high - about $400-$600.
We were fortunate enough to find a source that had used cards for $125.
Unfortunately, the source has sold out.
- Power - Though a decent antenna can extend the range quite a
bit, the WaveLan was designed for limited distances and is therefore a
low power (100 mW) device. It is theoretically possible to build an amplifier
to boost the power, but any design needs to be able to pull a signal from
the WaveLan itself to be able to switch from Transmit to Receive and back
again. Information on doing this is forthcoming.
- Security - Though Lucent touts the WaveLan as a secure device,
it is not in fact very secure. It uses Direct Sequence Spread Spectrum
as its modulation method, which could be very secure, but this security
was crippled by the use of the same spreading code on all WaveLan cards.
This means that although it is fairly difficult for a random eavesdropper
to find, let alone decode, a WaveLan signal, it is very easy for another
WaveLan user to do so. If you are thinking of that you could change the
spreading code, be aware that it is inside one of the proprietary chips
itself, and is virtually impossible to modify. This was probably done at
the insistence of the US Government, which wants to be able to listen to
all of its citizens transmissions. While Lucent does provide a selectable
Network ID, there are only 65,280 possible codes, and it would be fairly
easy to write a program that tries all codes in quick succession until
the proper Network ID is found. Hence, the radio link-layer of the WaveLan
is not very secure. Some cards come with a DES or AES implementation, of
unknown key length and robustness. Our cards did not. So we suggest implementing
some encryption and authentication on top of the WaveLan architecture,
such as IPv6.
- Legality - In the US, these devices are licensed to operate
under "Part 15" of the FCC rules, which limit the size of the
antenna and the power output. Modifying the antenna and power output would
put the device outside of the Part 15 rules. Fortunately, Licensed Ham
Radio operators are also allowed to operate in the same 915 Mhz band at
higher power and with any antenna. But Amateur Radio is restricted to non-commercial
transmissions.
Drivers are available for Linux, FreeBSD, MS-DOS,
OS/2, Windows
95, Windows NT