The devices, the drivers - pre/early 802.11

Jean Tourrilhes

29 October 03

The who's who of Wireless LANs under Linux.

I will make a short description of each product and will mainly focus on the drivers. For each driver, I will list its status (stable, buggy...), the maintainer, the version, how to get it and the main features. If you hear about something new or if you have developed yourself a driver, please notify me.

Because of the large number of drivers, it has been divided in four sections, the first cover really old devices, the second 802.11b devices, the third one devices faster than 802.11b and the fourth one other stuff.

This section list devices predating the IEEE 802.11 standard or based on the early IEEE 802.11 standards (see section 8), either Frequency Hopping or Direct Sequence. Those devices are mostly obsolete and discontinued, so most of you want to skip directly to the next section (see section 3).

2.1 Lucent Wavelan & DEC RoamAbout DS

2.1.1 The device

The Wavelan appears to the PC as a standard network card and interfaces naturally with the networking stack. The configuration includes setting the frequency (10 different channels), Network ID (16 bits). Hardware encryption is optional (DES or AES - 64 bits key).

This product is built around a standard Ethernet controller (that may be found in some 3Com and Intel Ethernet cards), and the Ethernet physical layer is replaced by a radio modem. The ISA and Pcmcia cards share the same basic architecture, have the same modem, but have different Ethernet Controllers and bus interfaces (the pcmcia has only one transmit buffer). Because the Wavelan doesn't use a specific radio MAC (no MAC level retransmissions for example), it uses very efficiently the bandwidth, but is more sensitive to packet loss and collisions.

There is two versions of the modem, a 900 MHz and a 2.4 GHz version. Revision 2 of the 2.4 GHz modem allows the user to set the frequency (from a set of predefined channels - the availability of each channel depend on the regulation). The Wavelan is Direct Sequence Spread Spectrum (11 chips encoding), using a 2 Mb/s signalling rate (using effectively 22 MHz of bandwidth) and diversity antennas.

2.1.2 The driver

The Pcmcia driver has caught up with the ISA one to offer the same level of functionality and reliability. The only difference are the pcmcia specific functions (auto loading, auto unloading, crude power saving).

The latest releases of both drivers (v23) adds SMP support.

The drivers use the card EEprom to save the configuration changes for subsequent reboots. Wireless Extensions let you configure the NWID, the frequency, the sensitivity and the encryption key (optional). Statistics include the signal quality, signal level, noise level and the count of packet received with an invalid NWID (see Wavelan documentation). Private Wireless Extensions include the setting of the quality threshold.

2.2 Netwave AirSurfer & Xircom Netwave

2.2.1 The device

The Netwave use a specific MAC protocol designed for radio (a pre 802.11 protocol, with fancy stuff such as RTS/CTS, virtual carrier sense and fragmentation). It uses a 9 bits domain (Network ID), the highest bit of it used for the type of network (set for access point operation and unset for ad-hoc operation). The Netwave uses also a 16 bits scrambling key (encryption). The Modem offers a 1 Mb/s signalling rate and frequency hopping (100 ms hop period). On the bad side, the Netwave has no antenna diversity and a high overhead.

Note that the Netwave AirSurfer plus is a very different beast (see below).

2.2.2 The driver

It seems that the Netwave is quite picky with some pcmcia sockets and you might need to choose carefully the interrupt (try different ones) and set the memory speed correctly. In some cases, under high load (big ftp), the transmission sometime get stuck (I guess that some interrupt are lost) and the driver has to reset the card (you won't notice it, it just decreases the performance).

2.3 Netwave AirSurfer plus

2.3.1 The device

The AirSurfer plus has two modes of operation, compatible with the old generation of Netwave, or 802.11 compliant. The hardware is based on an AMD core, and a 1 Mb/s frequency hopping modem.

2.3.2 The driver

The current driver support the AirSurfer plus only in Netwave compatible mode, and doesn't support the AirSurfer plus with the 802.11 firmware.

2.4 Harris Prism based cards : BayStack 660, ZoomAir, YDI and other...

2.4.1 The device

The AMD core integrates a generic microcontroller and the hardware baseband (ASIC) to do the time critical functions of 802.11. AMD has developed the 802.11 firmware with all the usual 802.11 features (MAC level ACK, RTS/CTS, Fragmentation...). The Prism chipset is a 2.4 GHz Direct Sequence modem offering 1 and 2 Mb/s. The Prism chipset can also be extended to supports the new 802.11 HR standard, with 5.5 and 11 Mb/s bit-rate (either MBOK or CCK modulation).

The Pcmcia cards are mostly similar from vendor to vendor. Some vendors offer ISA cards, and the Access Points are where vendors are making their difference (ZoomTelephonics uses a software AP on a PC, others have hardware AP). Each vendor also has to provide the high level 802.11 in their drivers (authentication, WEP, Roaming...), so those might be different (not that it does matter much under Linux).

The BayStack 650 and Netwave AirSurfer plus use the same AMD controller, but a different physical layer (Frequency Hopping), so are not compatible with this driver.

Harris has just become Intersil and released the Prism II chipset, successor of the PrismI chipset, this time including the MAC controller (so they won't use any more the AMD part in their reference design). I'll detail it in the next section (see section 3.6).

2.4.2 The driver

There is currently two branches maintained by Mark, 0.2.X which is stable and 0.3.X which is experimental.

Peter (with help from YDI) has created a alternative version of Mark's package to add ISA support, fix a few bugs and with explicit support of cards from YDI. In the long run, those changes should find their way in Mark's package...

Jason has created a version of the 0.3.1 beta driver with support for the BayStack 660, by porting bits from 0.2.6 (this allow support for both the BayStack 660 and infrastructure).

Danny has a patch to make the driver compile and work with kernel 2.4.X.

I believe that this driver doesn't support the BayStack 650 and Netwave AirSurfer plus cards (which don't use the Prism chipset but Frequency Hopping), but the changes for that might not be that hard to implement.

2.5 Z-Com LANEscape, ELSA MC2, Siemens I-Gate

2.5.1 The device

Z-Com claims that the WL2400 is firmware upgradable to 802.11, but I've been told that some old cards have an hardware bug preventing it. Anyway, the card has all the usual 802.11 features, and the modem is classsical Direct Sequence at 2.4 GHz, supporting 1 and 2 Mb/s. Those cards are based on the classical Prism design (AMD controller + Prism chipset - see section 2.4), but use a firmware written by Z-Com which is very different from the regular AMD firmware. This firmware has more features, is more performant, but has more bugs.

Z-Com also offers the XI family, which support 5.5. and 11 Mb/s (probably using a Prism II chipset). Those are not supported by this driver.

Elsa is a German company selling various hardware component and started to sell Z-Com cards as Elsa AirLancer MC2. Those cards were quite popular in Germany.

Elsa also sell a new AirLancer MC11 which has nothing to do with Z-Com and is the Wavelan-IEEE (see section 3.1).

2.5.2 The driver

Matthias seems to now have access to the driver source code and is investigating compatibility with 2.2.X and new firmware revisions.

Then, Elsa has released the full source code of this driver for their card, including configuration utility. Elsa has made the setup easier and seem to have also fixed a few bugs, because it is now working with kernel 2.2.X... This version works with 802.11 compliant firmware (2.0).

More recently, Heiko ported the version of the driver from Elsa to 2.4.X. This version works with the Pcmcia package (in the Pcmcia contrib directory) and with firmware 2.0. And then, Tobias has released a full source code version of this driver for kernel 2.4.X, likely based on the latest version on Matthias web page. This version is a patch to the kernel (on his web page) and works with firmware 1.2/1.3.

Jörg took over the maintenance of Elsa driver (for firmware 2.0) and did a partial rewrite of it. He fixed many bugs preventing interoperability with more modern 802.11b hardware, improved compatibility with kernel 2.2.X and 2.4.X, implemented Wireless Extensions and many other fixes and polishing.

Arnaldo and Gustavo took over the maintenance of the driver from Matthias (for firmware 1.2/1.3) and did a partial rewrite of it. They updated the driver to kernel 2.6.X, added full support for Wireless Extensions, and this driver is now included in Kernel 2.6.0-test2. This driver requires Wireless Extension v16 and will be soon ported to 2.4.23.

2.6 Proxim RangeLan2, Proxim Symphony, DEC RoamAbout FH, AMP Wireless, Intel AnyPoint and Compaq Symphony

2.6.1 The device

The RangeLan2 implements a specific MAC protocol designed for radio (OpenAir, another pre 802.11) implemented on a generic microcontroller. It uses a 4 bits domain, 4 bits channel and 4 bits subchannel, and also a station type (primary master, secondary, slave - this is used for network synchronisation). There is no encryption, instead it uses a technique called Security ID (which is a simple password used to derive the network ID). The OpenAir protocol is heavily based on RTS/CTS, offer a good robustness but some overhead. It offers as well a modulable contention window size, contention free access for the master, packet fragmentation and power saving.

The Modem uses frequency hopping, and 2 levels of modulations (2FSK/4FSK) : it runs a 1.6 Mb/s signalling rate for good channel condition (short to medium distances) and falls back to 0.8 Mb/s otherwise.

The Symphony line of product (home networking) offered by Proxim use the MAC protocol of the RangeLan2 (OpenAir) with a lower cost radio, and the main difference is the software bundle and the price. On the other hand, the Proxim RangeLan802 line is very different from OpenAir products, using the 802.11-FH protocol and a different interface, so the Linux driver won't work with it.

Recently, Proxim has released its first Symphony products compatible with the HomeRF SWAP standard. These are also sold as Intel AnyPoint and Compaq Symphony-HRF. The ISA, PCI and Pcmcia versions are still offered, and a USB version has been added. Those products use the same physical layer as the original Symphony, but the MAC protocol can either operate in OpenAir mode or SWAP mode. The main advantage of SWAP is the support for cordless telephony.

Proxim has also various 802.11-b products, named Harmony, Skyline or RangeLan-DS which are PrismII cards (see section 3.6). Proxim has also released some 802.11-a products which are Atheros cards (see section 4.2).

2.6.2 The driver

Starting with version 1.7.0, the driver also support the SWAP protocol and SWAP compliant devices from Proxim, Intel and Compaq (in both OpenAir and SWAP mode). Both the driver and the configuration tools have been extended for this support. Also, some primitive support for USB hardware has been added.

What I like about this driver is that after all those years, Dave is still strongly supporting the driver, fixing bugs, adding new features and adding support for the newer cards. It's impressive to see such consistency and dedication...

2.7 Symbol Spectrum24 (FH)

2.7.1 The device

The Spectrum24 products were designed from the start to be compliant with the 802.11 standard, way before the standard was eventually adopted. The first generation (1 Mb/s only) was compatible and interoperable with other 802.11 products (but not compliant), and the second generation of Spectrum24 (1 and 2 Mb/s) is officially 802.11 compliant.

Symbol is also very active in developing Voice over IP solutions for their wireless LANs, and that's why they are also selling some Spectrum24 phones. They are using the H.323 codec, compression and call setup (raw 64 kb/s, compressed 10 times) and a 30 ms packet rate (but I fail to see what they have done to overcome overhead and latency issues at the MAC level).

The MAC has all the usual features of the 802.11 standard, like MAC level retransmission, RTS/CTS, fragmentation, auto bit-rate selection, power saving and roaming. A nice feature of the MAC is the support of the micro-AP functionality, which allows to turn a PC into an Access Point (I would like more vendors to start doing that). However, their products don't seem to support ad-hoc mode.

The physical layer is Frequency Hopping supporting 1 and 2 Mb/s, with 100 mW or 500 mW output power and 100 ms dwell size.

2.7.2 The driver

The driver is designed for the Pcmcia card (LA2400 and micro-AP version), and the new 2 Mb/s version of the card. It is possible to use older cards (1 Mb/s) by updating the firmware for 802.11 compliance, and to use ISA card by configuring properly the Pcmcia package (those cards use a regular ISA to Pcmcia bridge).

Despite being beta, the driver is stable, well written and supports most features of the card (like micro-AP, shared memory access...).

2.8 Aironet ARLAN

2.8.1 The device

The configuration include setting the frequency and Network ID (24 bits ?). The MAC protocol is implemented on a generic microcontroler. There is two versions of the modem, a 900 MHz and a 2.4 GHz version. Both use Direct Sequence Spread Spectrum. The 900 MHz modem allow signalling rate up to 860 kb/s (fall back to 215 kb/s) and 12 channels. The 2.4 GHz version allow signalling rate up to 2 Mb/s (fall back to 1 Mb/s) and 5 channels.

2.8.2 The driver

The driver support only the ISA version of the card (655 or IC 2200). The driver have been fully tested and optimised by Elmer Joandi, includes a complete /proc interface and should be soon included in the kernel.

2.9 Raytheon Raylink, WebGear Aviator2.4 & Aviator Pro and BUSlink wireless LAN

2.9.1 The device

You are more likely to buy the Raylink as a WebGear product, either as Aviator2.4 or Aviator2.4 pro (which have nothing in common with their old Aviator 900 MHz line). The Aviator2.4 and Aviator2.4 pro are in fact the same product as the Raylink, the Aviator2.4 driver comes pre-configured in ad-hoc mode and offer only the Pcmcia card, whereas the Aviator2.4 pro driver comes preconfigured in managed mode and offer both the Pcmcia card and the Access Point (translation seems also to be different in each driver). Of course, it is possible to change the mode in the driver and all these products are fully interoperable. WebGear also offers a ISA to Pcmcia bridge to install the Pcmcia card in desktops.

Lately, WebGear has stop selling those cards, but recently BUSlink has started selling them again (same card, different sticker).

The Raylink delivers all the features expected from a 802.11 compliant device, with ad-hoc networking, access point operation, authentication and roaming. The MAC protocol is as defined in 802.11 : CSMA/CA with MAC level retransmissions. Configuration includes mostly the ESSID (network name).

The modem is 2.4 GHz Frequency Hopping, with 1 Mb/s and 2 Mb/s bit rate, and includes antenna diversity.

2.9.2 The driver

The new version of the driver adds Alpha support, authentication, and compatibility with the Windows driver. SMP is slowly being tested. I've added to the driver quite complete support for Wireless Extension (changing parameters still doesn't work right - therefore wireless.opts do not work).

The driver has been developed for the Raytheon Raylink and has also been successfully tested with the WebGear Aviator2.4 and the BUSlink.

I recently improved the support for Wireless Extensions. It is now possible to configure the card before the card is brought up (for example in the various configuration files). However, it is still not possible to change most parameters at run time (but they can always be read).

2.10 Diamond Multimedia HomeFree

2.10.1 The device

To reduce the cost, Alation has used the same solution as IrDA : to implement the MAC protocol in the driver instead of on the card. In fact, they are using a IrDA chip as the baseband, and instead of connecting it to an Ir transceiver, they use a classical 1 Mb/s Frequency Hopping modem at 2.4 GHz.

This solution save the cost of an embedded microcontroller on the card and allow to build a cheaper product (and to develop it faster). The downside is that building the MAC protocol in the driver tend to increase the protocol overhead (the MAC need more time to react to events - this reduce throughput and increase latency) and use more resources on the host (processor cycles and memory). In fact, this is an effect similar to win-modems and win-printers. Also, because there is a lot more code (which is more tightly integrated in the OS and performance critical), the driver is more difficult to port to other OSes (and that's why the driver below doesn't implement the HomeFree MAC protocol).

Personally, I'm not a fan of this design, but it seems to do the job cheaply.

2.10.2 The driver

This driver is both very different from a standard network driver (as the other driver I present on this page) and very different from the HomeFree Windows driver. This driver is a straight tty interface to the hardware (like a serial port), and doesn't implement any MAC protocol. Therefore, it can't be interfaced directly to the standard Linux networking stack, and is not compatible with the Windows driver.

Therefore, to use this driver, a MAC protocol of some sort is needed (to arbitrate access to the medium, multiplex connection and ensure reliability). Pavel recommend to use either some Ham protocols such as Scarab, or to use the Linux-IrDA stack. You can also develop you own application directly on top of this half duplex interface (most serial applications will assume full duplex).

The advantage of that is that those protocols are very lightweight, so usually perform much better (in term of raw throughput) than the original HomeFree protocol, and even better than some other WLAN products. However, those protocol (Scarab, IrDA) are not designed for the specifics of the 2.4 GHz band and don't include all the goodies found in 802.11. For example, IrDA allow only two nodes to be exchanging data at one time (only one IrLAP connection active) and deal poorly with multi nodes network. I also don't know how they deal with co-located networks and radio interferences.

However, the most critical missing feature is regulations compliance. The 802.11 protocol include some feature to insure compliance with all the various regulations in the 802.11 band (such as Frequency Hopping - usage of Radio Frequency tend to be highly regulated). As the driver of Pavel doesn't include all these features, this driver may not be legal in your country (note : this doesn't apply to the Windows driver, the Windows driver is legal because Diamond has certified it with the FCC and ETSI), and usage of this driver may bring you big troubles (same as setting up a illegal transmitter in the FM band). So, if you care about legislation, I advise you to check with Pavel about your specific case, otherwise use at your own risks...

2.11 BreezeCom BreezeNet PRO Pcmcia

2.11.1 The device

In term of protocol and modem, the Pcmcia cards are very similar to the other BreezeCom products (see section 2.11). The first two Pcmcia cards were limited in term of bit-rate (only 1 Mb/s), and have lower transmit power.

2.11.2 The driver

BreezeCom has also release a Linux driver for their latest pro.11 card. I've been informed of the existence of this driver since October 99, and many people have been using it since by getting it directly from BreezeCom, but BreezeCom did release this driver to the wide public only 6 months later. Let's not complain, because the driver contains the full source and is now GPL, so it was worth the wait !

The driver was written by Christian Olrog, an employee of Ericsson, based on the original Windows driver source, and it seems that the maintenance has been taken over by Alfred Cohen of BreezeCom. The source code looks very nice and complete, with only a few features missing. One interesting feature is that the driver can show the signal strength for Access Points in the area. However, the initial configuration could be simpler...

The driver has been in use by many Linux users since its original development and there doesn't seem to have been much complains about it, which is good ;-)

The original version of the driver, 1.0, is only for Linux kernel 2.2.X. There is a beta version of the driver for Linux kernel 2.4.X.

2.12 BreezeCom BreezeNet (not Pcmcia)

2.12.1 The device

There is three versions of the BreezeNet, the old one, somewhat Netwave compatible, then the first pro.11 version (flash upgradable to 802.11) and the new pro.11 version, which is 802.11 compliant, so with all the usual MAC features expected from 802.11 devices. In all cases the modem includes Frequency Hopping Spread Spectrum (20 ms hop period), a 3 Mb/s signalling rate (fall back to 2 and 1 Mb/s) and antenna diversity. Note that the 3 Mb/s bit rate is not 802.11 compliant.

BreezeCom now offers a DS.11 series of adapters which is 802.11-b compliant, with usual 802.11-b features (and up to 11 Mb/s) and still using the Ethernet interface.

In 2001, BreezeCom and Floware Wireless Systems merged together to form Alvarion. The new combined company seems to put less emphasis on wireless LANs and more on point-to-point links and wireless distributions systems, even though the old BreezeNet product lines are still available.

2.12.2 The driver

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Linux Wireless LAN Howto - jt@hpl.hp.com Converted to html from Frame Maker - 16 september 97 Updated 29 october 03 Copyright © 1996-2004 Jean Tourrilhes

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