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More Wireless Networking for Linux
I was sent word that AbsoluteValue and Intersil have announced more development of wireless support for Linux. The announcement is actually for Intersil PRISM-based WLAN cards, but what it does mean is more support for IEEE 802.11 wireless cards, access points, etc. Here at Slashdot, we've been using the ZoomAir cards, but are starting to play with the Lucent cards - what does everyone else think about Linux and wireless cards?
The Aviator cards from WebGear are very good. And fairly inexpensive as well. You can get a 2-station kit here. I use them at home and can take my laptop to a friends house and walk right into their network by bouncing dhcpcd. I get about 1.5Mbit inside my house too, which isn't bad considering my internet connection (also wireless) is only 256K.
there is a low cost wireless how-to at www.qsl.net/n9zia
I did a survey from spring 99 that was aimed at robotics use. At that time I saw it as a good possibility. It can only have improved sense then. I eventually plan to use them for linking to my robot and a wearable computer.
Having used both Proxim Rangelan II, and several versions of Lucent WaveLan (all pcmcia cards) in linux, I didn't have to many problems.
Neither has full source, you need a binary-only module (or in the case of the proxim driver, a library that you link against, I believe built from the Proxim reference source.) The Proxim driver was a bit bitchy in it's early days, but I'm told it works very well now.
Another note... most wireless LAN solutions have some kind of 'base station' or 'access point' they expect you to buy. If all you have is a few PC's, and it's for the home hacker, you generally do not need this. The cards themselves can communicate with each other just fine. The base station usually serves as the bridge (possibly router) between your wired and wireless networks, sometimes with added features like supporitng multiple transcievers on multiple channels.
Another trick with wireless LAN cards.. if you replace the omnidirectional antenna they give you with a good directional antenna, you can massively extend the range. I have seen Proxim Rangelan II cards bridge distances of about 15 Km and still be within regulations. This also works if you have a wall you need to penetrate that you can't quite manage without. (depends on the materials, though..).
Also.. most wireless LAN cards, by regulation, must use a non-standard connector. Usually, it's a standard connector with the mating parts switched around. (this is to prevent joe average from hookingn his little card up to his linear amplifier and causing WW-III).
Hmm. I could go on for a while.. perhaps I should start a Wireless LAN HAcking FAQ?
Wireless is insanely useful for the portable market. Portable devices that aren't tethered by a cable are becoming more and more prominent in the workplace. The cost however is somewhat justified (note that I said somewhat - read below).
There is a lot of processing power in those little cards to implement the IEEE 802.11 spread spectrum model. They're not cheap for that very reason. Plus you don't have as huge a cable infrastructure, which is a cost most places forget about.
There are on average about 3-4 times as many components/transistors on a wireless card as there are on a comparable network card. You also have to remember that almost all PCI/ISA wireless cards are really a PCMCIA card in a PCMCIA adapter. Compare the cost of a PCMCIA network card to a PCMCIA wireless card and the difference isn't as great as it first seemed.
Why stick with PCMCIA and use adaptors? Well for a start, developing 2 cards in completely different technologies tends to take way too much time, and leads to revision problems. Add to this that the greatest market for wireless is actually portable devices that have PCMCIA slots, and you can see the economics that cause the choice.
However, I'd still like to see a Compact Flash version of these (and using a CF to PCMCIA adaptor, you can still stick with one version), even if it sticks out of the Compact Flash slot. This would bring wireless solutions to devices that could really benefit them. e.g. Cameras - you take a pic, it stores it locally, and then sends it over the wireless link to a box nearby to store it. PDA's - allows you to access network resouces when in range. And so on.
There are also H.323 compliant phones available that use IEEE 802.11 spread spectrum. They operate across your normal wireless network to provide wireless telephony. Now if only the cost would come down, I'd be happy! *sigh*
I got the Webgear kit (2 cards) for about $150. I had a little trouble getting it to work at first, but once I got the newest version of the driver, I was flying wireless! For anyone out there who is married to a spouse that resents how much time you spend on the computer, a laptop with a wireless card is the way to go. I can sit in the living room (or anywhere else in the house) with my wife and chat while connected (wirelessly) to my Athlon and the internet. Now my wife can't complain that I'm always in the computer room.
-Steve
Democracy is a poor substitute for liberty.
The problem here is not with the radiation, but the definition of 'Microwave'.
:)
'Microwave' is a generic term used to describe basically *everything* from about 2Ghz (maybe even 1Ghz.. I forget) to about 30 Ghz (where you get into millimeter wave).
This spectrum covers a *huge* range of radio properties... it's not like you are desribing some tiny band.. like LF, HF, VHF, UHF, etc...
That said, you are correct.
Many Wireless LAN devices operate in the 2.4Ghz ISM band.
Microwave ovens typically work at 2.45Ghz.
The main difference, of course, is power.
Proxim RangeLan II, 2.4Ghz ISM, approx. 100mW.
Microwave oven, 2.45Ghz: Approx. 600 W.
So.. your microwave oven uses the same frequencies, roughly.. but at 6000 times higher power.
Also.. all that junk about microwave ovens heating water molecules by using 'specific resonant frequencies' is bunk. They do it by applying large amounts of power, period.
Now.. to address your latency issues...
My friend, the latency for wireless is no different than through copper. Radio waves through air travel *faster* than signal through copper (not that it would be measurable without sophisticated equipment, or large distances).
There is no latency associated with wireless.
People do voice over satellite.. what.. do you think that's not latency? that's 1/4 second up, 1/4 second down, and the saem in revers.. 1 second RTT simply to geostationary orbit and back. And it uses microwave.. just the same.
Hmm. Perhaps you are a troll?
Perhaps we need to play q3.. I'll use my wireless internet connection, (2.4Ghz ISM DSSS product) and you use whatever you want, and I'll still win
Microwave works
The range can be extended greatly if you use a directional antenna. (one on each end) I have done this, and it works like a charm.
THe ratings they give are for their little crap omnidirectional antennas, that have almost no gain.
A directional yagi will give you great directonal gain, and allow you to do what you want. If oyu aren't comfortable with it, explain it to a radio technician who can make the appropriate custom cables for you.
To make an example... one pair of cards, rated at 600 feet, with the appropriate antennaes turned into a 17Km link from a mountain top to a cabin. Not bad for a few hundred bucks in wireless lan cards, and some good radio antennaes.
Also.. running cat5 cable between buildings is not such a good idea, you run the risk of ground loops and burnt wiring. Better to use 10BaseFL (cheap plastic optical cable) if you want to do it this way.
Anyone who knows anything about this technology knows what Im talking about. First of all, the price. The prices are around $30 for the chipset but it is expected to drop to about $5-$10 once mass production ramps up. This means they will show up everywhere.
So whats so great about bluetooth? Well it was orginally designed to replace irda but it will now be doing so much more. Bluetooth devices have about a 30ft range. When ever one device comes in contact with another, they set up somewhat of a mini network. Eight devices in all can make up one of these networks. One is the master telling the others what frequencies to skip to ect (Bluetooth operates at 2.4ghz and utalizes spread spectrum much like digital phones). These networks can then communicate with other networks of devices. This is all done on the fly and may be reconfigured constantly when new devices move in and out of the area.
So what can be done with this. Well, first the obvious, like networking printers ect but it has so much more potential. From what I hear, the bandwidth is comaprable to dsl which is plenty for most applications and other bluetooth devices dont hog the bandwidth. Well, for one you could could dial up a connection using your phone in your pocket without even touching it. Now imagine bluetooth everywhere and commercial services. Imagine negotiating for an internet connection in an airport without ahving to talk to anyone. Imagine pulic printers, and a slew of other things.
We are only beginning to realize what wireless technology can do. The potential is gigantic. There are some things to worry about like will each device have an id; autonegotiation is scary. 2.4ghz is also the resonate frequency of a water molecule, think leaky microwave. Still, I believe this is going to be amazing, 1) because its so cheap and 2) because its so easy. Truely plug and play networking. Expect to see bluetooth devices this spring and integration into laptops and phones by next fall. For more information, check out Bluetooths home page. Lots and lots of big name backers. This is no vaporware.
here's the URL of the Apple AirPort doco that compares DSSS channel availability in different parts of the world
5 50
http://til.info.apple.com/techinfo.nsf/artnum/n58
brian whitaker
applications engineer, maxim
bwhitake@knarf.com
The only issue (besides cost of course) keeping me from currently switching over to wireless networking at my place is security concerns.
Can anyone tell me about the potential security issues that arise once one is literally broadcasting their information? Is (for example) SSH just as secure over the airwaves as through an ethernet medium?
I have a 100baseTX connection to all of my boxes throughout my apartment, and that more than sufficiently serves my purposes, but it'd be nice to take my laptop outside to relax from time to time...
--Cycon
Your Brain + EEG + LEGO Robots = Brainstorms
These zoomair cards have real possibilities. No more dongles to break. I'm up the street at a friends house on my notebook typing through an X forwarded netscape on it now.
:)
The only problem I had was the range. It only worked for about a block. So, I took the directional antennas off my X10 cams and patched them in. I had to take one of the cards apart to find out how to do it since no jack was available. Turns out a provision for a jack was on the circuit board layout, but not implimented. So, I notched the case at the end where the "Z" is on the zoomair logo, notched out some more plastic to move the "zero-ohm jumper" over from the internal antena to my new external. I epoxied the swivel mount of the miniture X10 directional antenna at the end. I wish I had my camera here to snap a shot as it looks pretty sharp. Anyhow, the range is spectacular. I was driving around town with it and only dropped a few ping packets.
Now I need to talk to my ISP and motivate them to set up a base station.
Why does it matter? Wireless networking xmitters should understand ethernet packets. They should not care what OS is producing them.
And in fact they don't. At least not as far as transmission goes. But once you've caught a packet and stripped off the header, what do you do with the contents? Send 'em out serially? Parallel? How are you marking start and stop? That's where OS (and hardware) dependence comes into the picture. And like it or not, one particular OS has most of the market among the businesses who can afford to buy new technology, so that's the OS that people build for.
Because of the OS independence of ethernet, I believe it would have been a better choice than USB as a peripheral bus.
How do you figure? You want as little management overhead on the data part of your peripheral bus as possible: that's why PCI has so many special signals (REQ#, GNT#, FRAME#, etc.) that are just for control of who's got the bus. This leaves the address/data lines free for shoving data as fast as your clock can mark it off. This is an example of the basic rule that hardware can accomplish a given task faster than software but at greater cost: the PCI bus is some 47 signals wide. But pulling 47-strand wire would be a real pain, so Ethernet makes do with 8 and accomplishes all the overhead by encoding it in the packet header, which could be considered software for the purpose of the rule above.
If packaged ethernet PCI cards can sell new for $8, then the ethernet chipset can't be all that expensive to stat building into printers, scanners, etc.
Perhaps you've never heard of a print server? Or network attached storage? These are examples of peripherals that are on the network. The time delay communicating with them is acceptable because people can deal with printing or file accesses taking a while to complete. But would you want your mouse or keyboard to have the same kind of latency? I think not: you'd be shot down each time you respawned while you waited for your mouse movement to process.
But ethernet is not Intel's baby like USB is, so it'll be build onto mboards to the detriment of all that is better. Firewire never had a chance except maybe in the Mac world.
Since when is USB Intel's baby? Last I heard it was its own standard, as in standards organization... USB is not a competitor against Ethernet, it's a competitor against the serial port (and a vastly superior competitor at that). And Firewire is a competitor against, well, something like AGP and something like the home entertainment network that doesn't presently exist. It achieves its greater throughput by eliminating some of the error checking of USB, so you wouldn't want it for file access, where every bit is critical. But it's great for streaming music or video because a bit here or there on those is no great loss. Ethernet doesn't compete against either one--it's for communication among independent systems, where a peripheral bus is for communication among subparts of one system.
Jenny