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Cheap Long Distance Wireless Networking 130

Posted by CmdrTaco from the now-there's-a-hobby dept.
enkidu writes: "Over at this article on macintouch there are some people who show how to extend Apple's airport range to 7km using legal signal boosting antennae. Connections at 50km+ are also mentioned. With enough base stations, you could even build your own private ricochet network in your neighborhood. " This should work with any WaveLAN cards ... looks like a fun hack.
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Cheap Long Distance Wireless Networking More

Cheap Long Distance Wireless Networking

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  • Up to 1 W of output power according to the FCC regs

    ERP is the "effective radiated power" output of a transmitter. Transmitting 1W of power into a 1/4 wave dipole antenna puts out 1W ERP in all lateral directions. Transmitting 1W into a 20 dB gain yagi antenna puts out 100W ERP in a single direction.

  • Re:Bandwidth congestion (Score:1)

    by Anonymous Coward
    First, there is a great deal of useful info about wireless networking here:

    http://www.hpl.hp.com/persona l/Jean_Tourrilhes/Linux/ [hp.com]

    Second, having many wireless nodes in a small region is fine. IEEE 802.11 works similar to Ethernet, all nodes must contend for access to the medium before they can transmit. That's how it's possible to handle hundreds of wireless nodes, like you mention above. Of course, bandwidth to each node is reduced, but transmission still works. Base stations help a great deal, because they act as arbiters; i.e. they can poll stations in range in a round-robin order, and thus avoid collisions between two nodes who try to send at the same time.

    There is a point against the "over-clocked" 802.11 nodes: they may interfere with ad-hoc nodes on adjacent channels. Although most documentation talks about 11 separate DS channels, in practice nodes which are less than five channels apart can still interfere if they are physically very close. However, most of the range-extender antennas seem to be directional, so it may not be a big problem.

    --ac

  • FCC - Expalin this (if you can...): (Score:1)

    by Anonymous Coward
    Since antena gain as specified by manufacturers is power output measured at 'half power beam' (-3dB) 15dBi antenna and WaveLAN combination will go over legal limit of 1W: 64x30 = 1720mW.

    So, it seems that only 12dBi antenna could get certified by FCC if combined with WaveLAN, yet Lucent offers package with 14dBi yagi???

    How about it?
  • Well, is that a limit on RF power into the antenna or ERP (Effective Radiated Power). ERP = antenna gain * RF power in.

    Hams have a power limit of 1.5 kW RF (i.e. what's going into the transmit antenna) but no limit whatsoever on ERP. I don't know if the FCC regulates anything based on ERP instead of plain old RF power. If that limit is 1W RF, than you can use an antenna as large as you want. I'll have to check the FCC regs someone else linked to.
  • Checked the regs. If your antenna has a gain of over 6 dBi (6 dB over an isotropic antenna), you must reduce the power from 1W by (Antenna gain - 6dB).

    6 dB translates to a gain of 4. So essentially, your ERP with 1 watt into a 6 dBi antenna is 4 watts. Still, the guy in NZ is within legal limits.
  • Posssibly not (although The Mac crowd has its fair share of hackers, both hardware and software based). What you need to remember, though, is that AirPort technology is 802.11-based [ieee.org]. This means that the technology should work for other wireless cards, including Lucent's WaveLan [wavelan.com] cards.

    As an answer to a previous post, the original article menations that the author found that the hack was legal in New Zealand (where he is based), and believes that the same requirements go in the States, as well.

    Leave it to the FCC, though, to find a way to make it illegal.

    What I would really like to see is affordable WaveLan/Airport-like Internet access sold like cell phone access. ("For $19.95/month - unlimited dial-up. For $29.95/month, unlimited wireless access. For $29.95/month - unlimited cell phone access.")

    I suppose that will happen the day that xDSL-like technologies are actually affordable.
  • Remember, there are no linear amps in the equation - they're not going to be bleeding all over adjacent channels & that sort of thing. Burners got a bad name because most were made with no respect for quality.

    They're getting more range by concentrating the power into a beam - as opposed to the normal omnidirectional spread. The antennas they use have great gain in one direction, and sod all in others - you won't even hear them 5 degrees off-line.

    There's nothing illegal about this - lots of other (read: more expensive) 802.11 units have been around for years sold with a pair of yagis for the express purpose of linking two distant sites.

    I'm probably completely wrong, but from memory the maximum gain allowable for the entire link (both ends) was 24dB. Full kits with directional antennae (don't forget the lightning surge arrestor if you're mounting antenna where they might get touched by the hand of zeus) are available, but they usually cost.

    Problem is, the normal "budget" 802.11 cards were crippled by just having an internal antenna and no place to connect a "real" one. Nice to see apple have done the right thing :)

    Hugo
    (just running out to buy a couple of airports to link the empeg mk2 in my car to the office ;) )
  • It wasn't actually ethernet, but it was the first multiple-access network. ISTR that it didn't actually use CSMA/CD (carrier sense multiple access - ie, you don't transmit if you can hear someone else) / (collision detect - if someone else collides with me I know about it).

    I think it used time slots to regulate access, and outstations couldn't talk to each other, only to the central station (which controlled the sequencing, and would perform routing).

    Hugo
  • But it isn't modified. They're using easilly available antennas designed to be used with these cards.
  • Open up an Air Port base station. What's inside? A Lucent card..
  • The stock lucent products let you set up to 4 "passwords" which need to sync with your base stations. You can also do "wire" encryption using them as the key, IIRC. There's also a way to hook it all into a directory, e.g. LDAP.
  • The beauty of the multiple names for individual concepts approach is that it leads to the same name being given to different concepts, thus furthering the obfustication factor, and keeping the rabble at bay. What's the point of being a high priest if everybody understands the mumbo jumbo? :-)
  • I'm pretty sure frequency hopping and spread spectrum are the same thing.

    Hey, if we didn't have multiple names for all this tech stuff, ordinary people might be able to figure some of it out, and we can't have that, now can we?

  • Did you read the article? This isn't some wannabe saying "wouldn't be cool if...", it's descriptions of what these people actually did and the results they got.

    Yes, they used Apple hardware.

  • This is a quite cool hack.

    I love the meter-long directional antenna bit. I'm going to mount one on the roof of my car.

    I wonder what the foul weather performance is. How does it handle rain?

  • Does anyone know if there is some wireless LAN stuff for, say, a PCI bus?

    My theory being that I could slam a wireless PCI NIC into my firewall box, and then a PCMCIA wavelan into my laptop/playstation2/whatever.

    --

  • EIRP is the sum of dBm and dBi, and of course is measured in dB. To the recieving antenna they really are pretty much equivalent. The maximum dBm is 30 and the FCC extended the regulations for ISM band equipment to allow for an extra 6dBi of gain on top of the 30dBm. Plus, they allow you to add 6 dB of antenna gain (isotropic radiation -- dBi) for each time you subtract one dB of power (dBm from your setup before it reaches the antenna -- you can reduce the power output of the radio or add more cable, etc).

    I have all the relevant calculations, but they don't make much sense in ASCII and since there really isn't a very good implementation of math rendering in a popular browser yet, I'll forgo that junk and just say that you can radiate a signal that would be comprable to a 4W signal legally in the ISM band.

    ~GoRK
  • That is because a lucent wavelan card doesn't put out 30dBm of power. It puts out something like 17 or 18. I don't know the specifics on this hardware because I use different brands.

    ~GoRK
  • Well, yeah if you can line it up like a laser pointer! And if you're in a vacuum!
  • Well, look at it like this. Let's say you have a metal mesh antenna and you need to shield the back of it because you want to put another antenna behind it. If you put the lead foil or whatever you're using directly on the back of the antenna, you are modifying the antenna (even though lead foil would only be destructive modification) and it would be illegal. In this case, you are modifying a certified piece of equipment.

    So in the ISM band where the antenna and the radio and all other equipment are certified TOGETHER, if you unscrew one antenna and attach another one, you may be operating with a modified unit and thus would be illegal.

    But you are backwards. It is not illegal to sell an uncertified device. Usually you see these for sale as "for use only in europe or canada" or whereever.. Syncronized frequency hopping radios are an example of hardware that is often sold to US people and used in the US even though it's technically illegal (as you can clog bands with them)

    I should say again that I still don't necessarily agree with this and I do not mind seeing people venture into uncertified territory responsiblly. In certain cases, there are actually better uncertified antennas for 802.11 than the ones that are certified. Phased-gate-array antennas come to mind, and I have never seen a 802.11 radio with a certified PGA antenna.

    Get off your asses and certifiy this stuff if you're going to make ridiculous laws, FCC!

    ~GoRK
  • You will most likely still need a way to configure the Airport without a PC. Once I have my 3Com Airconnect cards working, I'll be able to tell if I configured mine right. You can get an SNMP configurer that will talk and change the Airport at http://www.karlnet.com/download/configsetup.exe

    It can also import config files from the Apple Utility. Now if I could just get someone to send me a config set to bridged only mode.

  • So I was right, and you swapped dBm and dBi in your post... All I was checking.

    Though if for each dBm of transmitter power, you can gain 6dbi of antenna gain, you could use a 1 milliwatt signal (0 dBm) and a 186dBi antenna, and get (for a really narrow beamwidth) an EIRP of 186 dBm which would be the equivalent of a 4 terawatt isotropic signal. 'course the existance of noise might make this imptactical :)

  • Ummm... I'm not a professional, but last time I checked, dBm was decibels relative to milliwatt, and dBi was decibels relative to isotropic antenna, so don't you mean:
    This EIRP number is calculated as a maximum of 30dBm with up to 6dBi of gain at this power. The nice catch is that for every dBm of power you subtract, you can add 6dBi of gain!! This power output can actually be equivalent to about 4W of legal power depending on your antenna gain... as long as your dBm output is less than 30dBm.

    Which makes lots more sense to me, as 30dBm is 1 watt (3 powers of ten relative to a milliwatt) which strikes me as a pretty reasonable limit for a low-power antenna....

  • How nice! The mayor finally did something good for internet access. Let's hope it actually happens [boston.com].
  • Sounds like he's just adding the antena that the card was designed to accept. He just had to get around the AirPort's housing.
  • i currently get my network connections using freewave
    data tranceivers. they are NOT cheap, and are only 115kBps, but they will go up to 30+ miles line of
    site with external high-gain antennas. these are the same tranceivers used in various remote data acquisition applications. the advantage being they act as modems, and can emulate a hayes modem making them
    usable in many applications. my current link is runnin 100mW to 10dB yagis.

    the problem with external antennas on wireless ethernet devices is the FCC requires you to purchase the antenna from the same vendor as the actual tranceiver in order to maintain compliance with part 15 rules. purchasing a seperate antenna is totally doable, but if you cause _any_ interference and the system is deemed to not be in compliance with part 15 rules, you face fines and confiscation of equipment.

    just my .02.
  • Could someone please explain to me why this is off topic? This is an excellent idea (if it could be made secure).
  • I bought a pair of webgear cards about a week ago to get a wireless connection to my work (which has a T-1) which is about a block away.
    I got the things working next to each other ~5 feet (a 10MB FTP transfer took 70 seconds). But when I took one to the office, I can't get them to connect. I paced it off at about 380 feet between buildings, and then through 2 walls on each end. It's clear line of sight between the two buildings. They advertise 300 feet indoors and up to 1000 feet clear line of sight, so I thought I'd be in the ball park, but no luck.

    Has anyone taken these webgear cards apart to put an external antanna on them? Any other thoughts?
  • The IEEE 802.11 standard is effectively a medium access control (MAC) standard. The airwaves are only in use when a card is transmitting. So even though only 3 or 4 devices can transmit at once, many of them can exist in the same area, since they arbitrate for control of the airwaves. Sort of like ethernet -- you can have a bunch of devices, and they fight over who gets to speak.
  • As this well-spoken person says, trees are bad. We have a 9 link that has been established for 18 months. Mirrors, steel sheets, coated glass and many other materials will also reflect or block 2.4 signals.

    High-speed wireless systems require some amount of LOS (Line of sight) to work. Period. End of topic. While you can push through with power, in the US the 2.4Ghz radios are restricted to no more than a 1/2 watt at the radio, and/or a maximum EIRP of 4 watts. In some cases, where the systems are located near each other, you can penetrate many substances, include a tree or bush, but these are distances of less than 300-500 feet.

    In our field tests, we have established 18-mile links, as well as an astounding 32-mile connection.

    Our ISP operates a wireless system with 8 wireless locations. Our system is point to multipoint using FHSS 2.4, and a 1 Meg radio connection sells at $50 a month, with no setup fee, but you gutz ta buy your radio/antenna.

    There are a great many resources EASILY available on the net to learn about wireless.

    Unlicensed 2.4/5.8 ISM systems in the States will be most usable in rural areas where the potential for RF interference in minimal. These systems allow ISPs to deploy high speed Internet access to areas that might otherwise never get any high-speed services. An ISP can be broadcasting for less than $1700.

    Licensed systems will be (and are) appearing, and will likely dominate heavily populated areas. The millions its takes to buy the licenses and the costs for the hardware will mean that only the big boys will be able to play in the licensed high-speed wireless data markets. There will be some amount of unlicensed stuff in the cities, but RF interference issues will likely prevent large-scale use. The costs will restrict the use of licensed systems in rural areas.

    The real news here should be about the revolution in Internet access this technology is going to allow.... and for once RURAL areas are getting these services now, and the big city is still waiting.... Out here in the sticks we wait for all of it.

    It has been said that we are at the beginning of the new E-Conomy, that the world will run on the web. High-speed system in rural areas will enable these areas to be included in the revolution of economy, rather than being by nature excluded. As we make technological advances as a society, it is always the population centers that receive the benefit, and sometimes it never gets outside this zone. Businesses had to be there to partake.

    So, again, I maintain that there is a revolution in progress. :^) Rural Rules!
  • while we're on the topic...

    does anybody know if the psion 5mx will work with the wavelan/webgear cards??

    walking around with *fast* access... that has some serious cool value!!
  • The rails in out area ARENT welded together. They have copper or steel wiring connecting them, i bet its a failsafe system. no power = no rail
  • maybe you should actually know what you're talking about before you make such sweeping assumptions.

    Tesla was looked at as a "crazy man" in later life because of his genius. Just like many of the other genius minds of the world, he wasn't appreciated. When his money holders found out that he wanted to make a free energy source for the world, they withdrew the money. When his money ran out, he had to pursuade his workers to stay and work in spite of not getting paid. This, of course, didn't last long.

    Personally, if I was working on an invention with such far reaching capabilities, and my money ran out short of being able to demonstrate it's use... I think I'd go a bit "crazy" too. How about you?

    The point is, he wasn't actually "crazy", he was simply stretched to breaking point. It can happen to anyone, and it's a tragedy that it happens most to strong minds.

  • Don't let the AC get to you about Tesla. You're exactly right, IMHO.

    The 'electricity pump' worked off of some wierd chain reaction that it set up in the earth. I required an enormous amount of current, but it did work. He was even able to control the points around the globe that this energy got most concentrated. Basically, to get power, you need to tune your system to work on the same frequency of the geo-power system. Seems a lot like networking to me. :)

    I don't know.. maybe not, but it would really be an interesting experiment.

  • ISTR that the US Navy was doing something using ELF to communicate with submarines -- they were planning or building a large antenna in the Upper Peninsula of Michigan for this purpose.

    It was fairly controversial at the time (mid-late 80s) -- there was even a 60 Minutes piece on it.
  • You really don't think that a wireless LAN standard that would support 3-4 nodes would be ratified by the IEEE, do you?

    IEEE 802.11 comes in two flavors: DSSS, and FHSS; which stand for direct sequence and frequency hopping spread spectrum, respectively. Both are very efficient methods of utilizing narrow bandwidth, and the bandwidth is divided into channels which are controlled by the protocol and the MAC in these cards. The WaveLAN (Orinoco) cards use DSSS, and my favorite cheap IEEE 802.11 card, Webgear Aviator 2.4 [webgear.com] uses FHSS.

    You can precisely calculate the number of simultaneous nodes with help from a grad level telecommunications textbook, but you can be sure that it's much higher than 3 or 4; or 50 for that matter, which I know the Aviator supports.

    On a seperate note, few people know that spread spectrum, the technology that enables the IEEE 802.11 wireless LAN, was invented by the Hollywood actress Hedy Lamarr, one of the most beautiful women of her time.
    --

    BluetoothCentral.com [bluetoothcentral.com]
    A site for everything Bluetooth. Coming soon.
  • Its also interesting to see that the concept of Ethernet has gone full circle.
    Ethernet was born at the University of Hawaii and was called Alona Net. It was a way for remote locations (like islands and ships) to communicate data back to a central resource.
    So it looks like ethernet was born in the airwaves, then it went to the ground (through copper and fiber) and now it is going back to the air again.
    Just some mindless knowledge for the average slashdotter :)
    --------------------------------------------
  • Tampering with the antenna or transmitter of FCC class C equipment is quite explicitly illegal!!!

    That fact has not stopped an acquaitence of mine from running a 2 Mbps link using older cards, a broadband signal amplifier, and a directional antenna over a 12 mile range for the past three years...

  • IANAL etc...

    Up to 1 W of output power according to the FCC regs for this frequency band FCC (47 CFR) Part 15C, Section 15.247 [gpo.gov] The relavent code according to the Lucent website [wavelan.com] for the WaveLAN(Orinoco) cards.

    Note the hack described used 1500mW directional to get a 14km range(or 1.5W in case you can't convert this is over the limit stated by the FCC for this frequency band and use).

    Interesting that use of this frequency requires frequency hopping, anyone who knows more than me about what this means for interferrence between units?

  • Boy, you realy don't understand what is being talked about do you?
  • And what hard ware do you use? Pleas don't tell me that your intel chip is more advanced than that of the IBM/Moterola. Cuz it aint. Read some benchmarks. and while your at it talk to some people at computor repair shops about reliability.
  • I was makeing no attampt to prove anything, he did not so why shuld I, no don't anser that I am grumpy and taking it out on whom ever is at the other end of my keybord. But hay why not.
  • Sorry, but that is not true.

    Frequency hopping is a technique by which you
    move the entire information stream from one
    frequency to another, whilst spread-spectrum
    techniques spread (smear out) your signal over
    multiple frequencies.

    And yes, I'm sure of this, 'cause I'm workin' on
    a very high precision GPS-chip. And as you all
    know GPS uses frequency spreading...

    J.

    P.S. both techniques are used for the same purpose
    dough:

    - to prevent jamming
    - and eavesdropping
    - as a MAC(Medium Acces Control)-technique
  • They were able to communicate 14 km with two 17db gain yagi antennas. If you wanted to cover a neighboorhood, the base antenna would have to be an omni-directional antenna. The omni-directional antenna from lucent is a 9 db gain antenna. A 8 db difference is about 1/6 the radiated power (db = 10 log10(p1/p2)). So you should be able to cover about a 2km radius (provided that your laptop is still using the yagi) I think.
  • yes.
    look in /usr/src/linux/drivers/net/wavelan.c
  • Spread-spectrum wireless ought to take care of the congestion problem.

    802.11 is already using spread sprecrum though!
  • Yes. It gets congested even now, even with ETSI power limits, which are much tougher than FCC's, especially in cities in countries where public-band microwave equipment is used a lot. Here (Czech Republic) ISPs use point-to-mutipoint 2.4 GHz microwave to connect leased-line customers without goint through expensive telco, and the air is slowly getting congested. The next step is to obtain private frequencies and not use public band except for "clear" areas..
  • I'd add the wireless Linux resources page at http://www.hpl.hp.com/persona l/Jean_Torrilhes/Linux/ [hp.com].
  • Interesting that use of this frequency requires frequency hopping, anyone who knows more than me about what this means for interferrence between units?

    Well, it does not *require* frequency hopping. In 2.4 GHz, there are both DSSS and FHSS radios.

    DSSS (Direct Sequence Spread Spectrum): You basically you statically chose one channel (out of a dozen or so) and then all the communication goes through the chanell, "modulated" by the data, so on chanell #1, 0xff always gets sent on 2.43285938 GHz, and if there's some interference on that frequency (e.g. somebody else is using it), you just cannot transmit 0xff.

    FHSS (Frequency Hopping Spread Spectrum): You typically broadcast in whole band (it is allowed by FCC/ETSI regulations), but only few ms at a given frequency. Then you move to another frequency, given by a special sequence. There are lots of these sequences, made up so they interfere very little with each other (e.g. 1 3 4 6 and 1 2 5 3, see that they meet only at 1, in real life there's IIRC 80 frequencies not four as in my example). Kind of like the joke about 1 second late watch never being right. Besides, even if you chose the same sequence as somebody else, if you don't turn your equipment on in exactly the same time, you never cross and both can use full bandwidth the equipment can do.

    It's clear that FHSS is much resistant to interference, especially from DSSS pieces of equipment. If you have a DSSS and FHSS equipment sharing same space, DSSS usually dies but FHSS just gets a bit slower.

    Again, I am trying to simplify, please don't take this literally. (Yes, 2.43285938 GHz for 0xff in channel #1 is probably wrong.)

  • Whether one transmits at 1500 mW or 4000 mW is not really relevant. My point is that when there are enough people trying to do this long-range stuff (even at 1500 mW), the bandwidth will eventually get clogged enough to cause chaos.

    Remember what happened to analog 900MHz cordless phones? Ever try to use one in a crowded apartment complex or dorm? There are only ten "channels" (bandwidth slices), and it can sometimes get frustratingly difficult to find a free channel.
  • might a company use these techniques to offer a commercial airport serivice? by that I mean a company could offer access to a city/state/whatever-wide area airport network which it runs for some sort of monthly fee... though airport, as it stands from apple, only supports a small number of users per node, I'd imagine the nubmer of users/node could be increased fairly cheaply either by buying more nodes (they're cheap.. around $200, i think) or doing some sort of hack...
    anyway, just my 2...
  • So if I get an Airport and some Wavelan cards I can network my PC's, no Mac required?

    The base station is only $299, right? Comparable stuff for PC's is like a grand IIRC.

  • Impulse Radio a whole new wireless medium.

    'Impulse radio' is a lot more than just an "interesting wireless link," it is a technology that will revolutionize our use of the radio spectrum. Rather than transmitting information as modulations in an analogue radio wave's frequency or amplitude (FM or AM), Time Modulated Ultra Wideband transmits information in RF pulses (called monocylces), positioned with an accuracy of trillionths of a second. It operates with just miliwatts of power, yet signals can be received for over a mile.

    I first read about TimeDomain several years ago. The technology sounded pretty much ready to go, but they were being stymied by the vast regulatory bueracracy that is the FCC (selling radio spectrum is a cash cow, and if you were the FCC, would you eagerly antiquate a profitable revenue stream?). TimeDomain was also duking it out with an Alphabet Soup Government agency (one of the national laboratories?) over who had patent rights, those issues have recently been resolved.

    There have been some comments about bandwidth congestion - ultrawideband technology will virtually eliminate all such concerns. Sending out around a milliwatt of power, spread over several GHz of bandwidth, makes it difficult to tell the difference between signal and background noise.

    Some usefull links:

    TimeDomain's homepage - http://www.time-domain.com/ [time-domain.com]
    The Ultra Wideband Working Group site - http://www.uwb.org/ [uwb.org]
    NY Times Article (1998) - http://www.n ytimes.com/library/tech/98/12/biztech/articles/21t ime.html [nytimes.com]
    Time Domain's Coverage in national media - http://www.time-domain.com/news/newss ect.html [time-domain.com]

  • Look into some of Tesla's patents. A search on google will return a bevy of information.

    One of his patent's was for an "electricity pump" that would pump power into the ground, and to access it, stick a wire into the ground.

    Some of his stuff is pretty far out (for me maybe), I suppose, but he was a genious.

    If he could send electricity through the earth, why not some data. It would be the "next step"...
    Be thankful you are not my student. You would not get a high grade for such a design :-)

  • As channel 38 is suddenly drowned out over a hundred to thousand mile area with: " Rorogerger ththatat goodgood bubuddyddy. I'm'I'm runruninging aa fourfourkikilolowattwatt linlinearear onon mymy rigrig heherere onon thethe highhighwayway inin Tuctucsonson withwith thethe ecechoho mimicrocrophophonene. Howhow amam Ii cocomin'min' downdown ththereere in 'bamabama?"

    Transmitter power limits were created for a reason.

  • Hmmm... that link is forbidden for me.

    Its because The Man doesn't want you to know about technology that can reduce stock values in his favorite portfolio. Apologies to the author, I made a little mirror [208.164.142.154] on my slow link if you want to try it.

  • Whether one transmits at 1500 mW or 4000 mW is not really relevant. My point is that when there are enough people trying to do this
    long-range stuff (even at 1500 mW), the bandwidth will eventually get clogged enough to cause chaos.

    It turns out that this isn't a big deal. Most wireless cards today use direct sequencing similar to the CDMA telephones. So if you have interferrence, it will be ignored if you have network ids and different pseudo random number sequences.

    Also, the high gain antenna needed to shoot a long distance are highly directional. The 24dBi antenna that I have on my roof has a spread of about 5degrees of useful power. Since it is so small, the area that I'm "polluting" is somewhat small. Also, since they are so highly directional your antenna would have to be both in the line of site between the two sites as well as looking at one end or the other. Since these conditions are so hard to hit, even in crowded areas the chances of interferrence is low. And when you are interferring, you just pick a different network ID and the radios automatically discard the extra traffic. 2mbps is a lot of bandwidth and there's likele plenty for everyone.
  • Umm, Richochet uses CELLs.. this setup would basically create massive problems for anyone else wanting to use the airport. 'tis better to get a larger frequency spectrum and break it up into a honey-comb like arrangement with land-lines and/or relay-frequencies. Read up on cell phone technology.. it's effectively what you'd need to do for a wireless MAN.
  • In answer to your first question the 2.4 gig stuff is actually ISM band stuff. The ISM band is a 22MHz band centered around 2.4GHz. And yes, 802.11 radios talk all throughout this band.

    That original reg was written a long time ago primarily so that "microwave" devices (like your microwave oven) and similar medical equipment (scary thought) would have a free high-frequency range to interfere with legally. Put your wavelan on top of an operating microwave on high and you will see about a 50% reduction in bandwidth.

    The redone spec allows this sort of use, or obviously there wouldn't be a bazillion companys selling ISM-band equipment today including cordless telephones and wireless lan equipment. See my other post (it's long and +5) for a layman's rundown of the law as it applies to wlan's and ISM stuff in general.

    ~GoRK
  • Well, read my other post where I clarified this It's here [slashdot.org].

    Anyway, you can't tramsmit 30dBm+45dBi on this setup legally. To use 45dBi EIRP you'd have to have only 22.5dBm power maximum. Plus, you'd probably never make the link since that much gain would affect the shape of your radiation pattern. It would extend directly from the directional antenna in the shape of what amounts to a very long thin, pencil.

    Think silly putty. Both antennas have to be inside the blob to make the link. The amount of silly putty is the dBm and the dBi is how much you stretch it out. You should check out some propigation patterns at even 24dBi. They are pretty skinny necked little buggers. I can't even imagine aiming a 45dBi antenna. Sure if someone else put their radio in that line it would be useless but then again, that propigation path is very small.

    Hope this helps but it's probably clear as mud

    ~GoRK
  • Actually, FHSS (Spread spectrum frequency hopping) hops to a different frequency after a set amount of time. In 802.11 frequency hopping occurs on 76 distince frequencies in the 22Mhz ISM band centered at 2.4GHz. The hops are psuedo random and the radios are very expensive to jam. Even when you turn on your microwave, you only interfere with one or two hopping frequencies, so you notice maybe a 5% reduction in bandwidth and a couple retransmits but nothing too bad.

    And as for the government's being concerned nonsense they are very concerned and I've seen quite a number of people get busted on 2.4GHz stuff. I dont know where you get off saying that sharing this band with microwave ovens is difficult. Remember that this is a 22MHz band and your microwave oven transmits about 50 feet or so. It's radiation curve is also very steep so it only interferes with maybe 1/50th of the band. Plus, microwaves have a 50% duty cycle on high so even when it's on full-blast it only interferes half the time!

    ~GoRK
  • Direct line of site is going to reduce your signal only based on the equasions for free-space loss. And it's not just LOS, but 60% of your fresnel zone has to be free too otherwise you're going to take a hit.

    Indoors, you have problems shooting through walls (drywall gives about 3dB loss... so does glass). Insulated walls and coated glass give about 6-8dB loss, etc. A row of trees outdoors gives about 3dBi of loss.

    The major problem indoors is multipath propigation (where the signal bounces off of walls and stuff. I had to WLAN a room that had angled mirrors around lightbulbs on the ENTIRE ceiling. It took *FOUR* access points (one in each corner) to get rid of multipath problems (the didnt really want to change their mirrored ceiling!

    ~GoRK
  • The radios you have described at 2Mbps are Frequency-Hopping spread spectrum not direct sequence.

    Frequency hoppping spread spectrum (FHSS) radios deal with interference very well but the 11Mb radios are not frequency hopping they are Direct sequence (DSSS) and if you get two conflicting DSSS systems on the same channel (of which there are only 3 non-overlapping you have total interference! The radios will share bandwidth if they're supposed to be on the same WLAN (Same ESSID) and the same brand but if they are different ESSID's, and especially if they're different brands, they are most likely going to cause each other TOTAL INTERFERENCE. I deal with this problem every day attempting to co-locate 11Mb DSSS equipment. It's a real headache. I'm just glad some IDIOT hasn't gone and started soldering on his airport in between some of my DSSS beams.

    ~GoRK
  • There are a few solutions for this. I can't find one right now, but most are PCI cards that have a PCMCIA slot for X Brands wireless PCMCIA card. Some are removable and usable in a laptop as well, some aren't. Just check the sites dropped in the comments here by others. From the pictures at 3Com's Airconnect page, it looks like 3Com will have one, but it's not out now.
  • The 1.1 update did more than just fix bugs. For example, I no longer have to type in my password every time I come home, since the AirPort 1.1 software interfaces with MacOS 9's keychain feature and automatically connects to an available network if it has the password for it.
  • Anyone know if this absolutely requires direct line of site? Or can this be used within buildings and such as well?
  • The card has a port that allows you to plug an external antenna to it, all they did was take the AirPort housing off, it's just a PCMCIA card inside a pretty package. There's some cards that will sell you a dipole to plug into their card to increase the range. Stop making yourself look like a jackass.
  • It's not as simple as power output. The radiation pattern is equally important.

    I know that a 100mW card can do links of over 10km, given the right antennae (NO additional amplifiers, just good yagis)

    Antennae don't boost power output, they just focus that power.

    As for interference, it means the units are supposed to use a non-deterministic hopping pattern, such that they don't overly interfere with each other. If frequencies are found to be bad, they are skipped. The idea is, the hopping sequence of various radios adjusts so they all get their fair share.
  • I'm positive you know what you are talking about.. but from my experience, it is not necessary nor illegal to switch out antennae so long as you stay within spec. Granted, joe average may not know how to do this, and he shouldn't, but you are perfectly within your rights to 'modify' gear so long as you stay within spec.

    It is illegal to sell a device that is not certified. It is not completely illegal to use a device that is not certified.
  • And though I'm not sure it really is illegal, it is also true that the port you are referring to is a non-standard connector. Gender-reversed, or reverse thread, or some such thing, as required by FCC.
  • Rombuu wrote "..if you were a) motivated and b) technically inclined enough to do this, would you be using Apple hardware in the first place?"

    Well, conceivably, sure!

    No one will deny that Apple has made some stinkers, but they also have a pretty good record (compared to most computer companies) at making well-crafted products.

    And as the article emmett posted the other day pointed out, the Airport is really just some COTS parts stuck together handily [slashdot.org], and at not a bad price for the convenience.

    It's not my primary computer any more, but I do have a happily functioning SE/30 on my island of desks, and have always thought of it as one the coolest machines I've ever seen. What it does, it does very nicely.

    And I've seen few PC cases as easy to work with as the G3 case, or the swing-out-side PowerMac case of a few years ago (I forget the model name). Not my aesthetics quite, but installing a new drive in a G3 is much nicer than taking apart / cutting fingers on most cases.

    So ... errr, yeah.

    timothy
  • Uhmmmm hate to bust your bubble, but this is really old news. Our ISp has been doing long haul wireless form a couple of years. Of course wehn *I post something to Slash it gets declined... sheesh..

    It you want to learn about 802.11 wireless systems in use for networks and Internet access, please do read out FAQ

    Wireless FAQ [midcoast.net]

  • d. can't find webgear cards anywhere online!

    See http://shopper.cnet.com/shopping/search/results/1, 102 14,0-1257,00.html?tag=st%2Esh%2E1257%2Esbsr&qt=web gear&cn=&ca=1257 [cnet.com]. At least a few online stores--including a few such as TechStore, Inc. [techstore.com] that claim realtime inventory--seem to have WebGear equipment in stock. Good luck.

  • we seem to have a lot of wireless networking posts here and it finally got to me; I have an athlon 850 sitting around (finally got to tell somebody!!) here in the midwest (stl) and ran into all these different problems:

    a. it is not cheap
    let me repeat, it is not cheap

    there are two basic options for a hobby lan the WaveLan [wavelan.com] cards or the WebGear [webgear.com] Airport cards. The base stations for the wavelan are $600+ and those for the webgear are $500+

    b. HUGE tradeoffs all over the place.
    wavelan is fast at 11Mbps, webgear only 2
    wavelan cards are $180/ea, webgear gives you 2 for $199
    you can use an airport instead of the wavelan access point, but that has configuration problems. You need a mac to configure stuff etc. I don't think I know anybody who uses a mac.

    c. no local electronic stores carry them
    even good ol' compusa stopped carrying the webgear cards. (i called)
    If I am going to spend this kind of money, it will *have* to be an impulse buy at a store!!

    d. can't find webgear cards anywhere online!

    the only thing you really want to get is not in stock anywhere on the web!! Everybody posts about bargain buys (2/$99 etc) but where are they????

    we could do all kinds of fun things with cheaper wireless lans, I live in a univ-student area and we could have all kinds of cool hacks if these things were cheaper...

    this is when I wish most that we had a mercata style group for slashdotters...if apple can sell $99 wireless cards, why can't anybody else???

    (posts with links get moderated up...
    hmmm... lets throw in some links@!!)

    get this! [sunsite.auc.dk]
  • I remember reading an article in 2600 [2600.com] about using the earth itself as a means of propagating radio signals. It supposedly could transmit information across thousands of miles. Of course it was merely a 2600 article, so it may be pure bunk.

    I'd appreiciate a response by anyone who knows more about the topic, as if definitely would be a neat means of communication.

  • The Apple Airport web page includes an interisting Orwellian usage of "user experance."

    "AirPort 1.1 Update

    If you purchased an AirPort product, you will want to upgrade your base station and card to AirPort version 1.1, which features improved user experience, new functionality such as active roaming, and a preview version of the software base station .

  • Clarification: Only 3 or 4 devices may transmit at once. That's what I should have said. Obviously, more devices are allowed to exist, as long as they're not all transmitting at the same time. 50 users on one base station browsing the web is probably fine. 50 users on one base station all trying to upload or download massive files is not okay.
    --

  • The members of a small co-op called cwx.net have established very similar service in northern Colorado. Basically, trying to get DSL out of US-Worst is hopeless if you happen to live in a building younger than 10 years, and AT&T is in no hurry to get cable modem service out here.

    We are using Aironet (now Cisco) 4800 series packet radios to serve 256Kb/s and 512Kbps service to Fort Collins and surrounding areas. The 4800 series radios are marketed as `indoor' wireless equipment, but they work very well over long distances when used with 36"x24" grid antennas. My own station is 4 miles from it's access point. There are points in service as much as 10 miles out.

    We are fortunate to have a line of mountains a few miles to the West for mounting access points. The toughest requirement is the line-of-site path. Obstructions are mostly impassable.

  • Well, I work for an ISP which does wireless Internet access over BreezeNet. I wonder what's so special about enlarging gain and thus reach by adding a high-gain antenna to the equipment. It's possible to do do 40-50 km links with 24-30 dB antennas. Even a bit more with an input amplifier. I don't know the prices of WaveLan cards, or this Apple stuff that apparently has WaveLan in them, because we don't use them as they are very prone to interference (especially somewhere with FHSS traffic), but prices of a pair of BreezeNets and two 24 dB antennas might be something like $1700. And there are even cheaper devices than BreezeNet.

    So, "Cheap Long Distance Wireless Networking" already exists. Damned, I am using it as I write this. :-)

    There's one caveat though. The FCC/ETSI regulations. From what I know, in the US there's some power limit on the transmitter, and then you basically can use whatever high-gain antenna you like. In Europe, ETSI regulations regulate the total output of the system (the device + antenna gain), so you cannot do very long distance links with this technology, because the larger (=higher-gain) you have, the less power you are allowed to transmit through it..

    If you live in ETSI countries, there's a possibility to have fairly cheap high-bandwidth (8 Mbps full-duplex) point to point links over big distances using devices in public 10.3 GHz band (as opposed to 2.4 GHz typically used by BreezeNet, WaveLan et al). This is a bit more expensive (say, $10000 for both points). Here the main manufacturers are CoproSys, Miracle or Alcoma.

    I have tried to simplify things, experts please forgive me.

    PS It's plain silly to use 2.4 GHz equipment through trees, as the author of the article mentions - leafs block the signal in this band a lot.


  • When the range of the network is so great, what is to stop anyone with an iBook from just walking by and hopping on to your network? I don't know much about the airport's wireless networking. Would anyone like to go into it with a bit more technicality?
  • Although you can obtain the equipment legaly is it legal to actually use it in this manner?
  • Ummm! Good comment. Just some messed-up units.

    FCC allows 36dBm EIRP. That could be 30dBm (1 Watts) power + 6dBi antenna gain (or 20+16 etc.).

    If you are using an antenna with 45dBi gain, the output power should be less than -9dBm. Otherwise it is very possible to F*CK other's communication.

    More importantly. This could become a health threat, especially for people who are near the transmitting antenna. Theoriotically, 30dBm + 45 dBm gives you more than 30K Watts EIRP!! Even allow for some spreading, it could do some damage to some senstive organs. Please be advised the 2.45 GHz ISM band is EXACTLY the microwave OVEN frequency. I don't know about you, but I'd rather not been aimed at by this kind of energy.

    It is surely NOT legal and potentially UNSAFE. To be blunt, if you cannot derive these two conclusions by reading those instructions for building the "wireless networks", you probably don't know what you are doing. Think twice, no, three times, before you set out to enjoy your "cheap wireless" network. There are things even reboots or re-formats can't fixed.
  • Hey ! So many people complaining about bandwidth congestion and the poor users who didn't get their stuff upgraded.

    Have you not been seeing those "FCC approved" stickers for decades ?? Ever wondered what they are for ? Hello !!

    I know that many people around here are against any law that limit what people can do/say, but the FCC regulations are usefull here. They limit what you can emit so that you do not disturb other nearby equipment. So, if the limit is too low, go complain to the FCC.

    Arguing that Apple made the Tx/Rx use a lower power to solve the issue is simply not enough. The thing should have been designed so that many people in the same area can use it, considering that other people around are using the maximum permitted by the FCC.

  • Not only is it not very fat, it's astonishingly narrow. IEEE 802.11 devices have a tiny little chunk of the radio spectrum - IIRC, only enough for 3 or 4 802.11 devices to be operating in the same area at the same time. This would be next-to-useless for setting up a neighborhood network, and it would probably bug the hell out of anyone else trying to use an 802.11 device nearby, as you would be effectively jamming them.

    So I know next to nothing about the technicalities of spectrum usage (as my previous post to this thread apparently demonstrated :-). But, I do work in a large building that has several dozen base stations and many hundreds of wireless machines operating all the time. There are at least 5 basestations that I know of, operating within 20 yards of my office right now. There doesn't seem to be any significant congestion problems. Perhaps the hardware or software is doing some arbitration?

    As I said, I'm not up on the technicailites involved, but in practice this seems to be much less of a problem than your post would suggest.

  • Re:Cheap Fast Broadband?? (Score:3)

    by dattaway ( 3088 ) on Thursday April 06, 2000 @10:35AM (#1147301) Homepage Journal
    Here is a Wireless HOWTO [gbonline.com] that covers just about everything including what and where to get wireless cards, antennas, cables, design, construction, amplifiers, etc. Look on the links page for all kinds of goodies wireless.

  • Uhh, lemme get this right . . . (Score:3)

    by alhaz ( 11039 ) on Thursday April 06, 2000 @01:09PM (#1147302) Homepage
    So, the "hack" here is that they drilled a hole in the side of their AirPort to enable them to plug the vendor-approved signal amp into the stock wireless card inside?

    Yes, this will work with any WaveLan card. Of course it will, it's a Lucent product that's marketed for this purpose.

    Call me back when you're homebrewing your own signal amps out of arrays of power transistors.

  • Re:There's an easier way to do this, folks! (Score:3)

    by .@. ( 21735 ) on Thursday April 06, 2000 @11:30AM (#1147303) Homepage
    Actually, the Apple AirPort ***BASE STATION*** is a repackaged Lucent WaveLAN Silver. The $99 AirPort CARDS are so cheap because they're actually missing hardware. The reason those $99 cards require an iBook or certain models of Powerbook is because those models contain the rest of the hardware necessary for the AirPort card to be functional.

    Let me be clear: The AirPort CARD that Apple sells at an MSRP of $99 IS NOT A FUNCTIONING Lucent WaveLAN card!

  • Re:Yeah, but... (Score:3)

    by Mister Attack ( 95347 ) on Thursday April 06, 2000 @10:22AM (#1147304) Journal
    ...if you were a) motivated and b) technically inclined enough to do this, would you be using Apple hardware in the first place?

    Short answer: Yes.

    Longer answer: I don't see why everyone assumes that simply because someone's using Apple hardware, they're not technically capable. Lord knows there are lots of clueless people on both sides of the fence, but there are also lots of intelligent hacker types who just like the way Apple's stuff works. The cases are great for the upgrede-inclined, everything works the first time, every time, and we can run Linux or Virtual PC if there's something we absolutely have to do in another operating system. And that's just the Mac users. Just because you're using an AirPort base doesn't necessarily mean that you use a Mac - AirPort is the cheapest 11 Mbps wireless networking doohickey out there. And it works with all the wireless cards that conform to the spec (which is most of them).

    Slashdotters in general don't seem to get the idea that sometimes, once in a while, the best solution to a problem might come from somewhere other than Linus, AMD, or John Carmack. Sometimes Apple hardware is just the best and cheapest way to get a job done.

    Or did I just get trolled?
    --

  • Re:Bandwidth congestion (Score:3)

    by Mister Attack ( 95347 ) on Thursday April 06, 2000 @10:26AM (#1147305) Journal
    I imagine that the chunk of bandwidth reserved for the AirPort can't be very fat.

    Not only is it not very fat, it's astonishingly narrow. IEEE 802.11 devices have a tiny little chunk of the radio spectrum - IIRC, only enough for 3 or 4 802.11 devices to be operating in the same area at the same time. This would be next-to-useless for setting up a neighborhood network, and it would probably bug the hell out of anyone else trying to use an 802.11 device nearby, as you would be effectively jamming them.
    --

  • Bandwidth congestion (Score:3)

    by Spire ( 101081 ) on Thursday April 06, 2000 @10:03AM (#1147306)
    I admit I don't know much about the inner workings about the AirPort, but I do know that it uses radio, and I know that there's a finite amount of radio bandwidth out there. I'm guessing here, but I imagine that the chunk of bandwidth reserved for the AirPort can't be very fat.

    If everyone started extending the AirPort's range beyond what is allowed (the article quotes 4000 mW), then wouldn't the available bandwidth get congested really fast, causing collisions, and thus breaking connectivity?

    Getting the AirPort to work at great ranges would be great at the very beginning, but everything would soon come crashing down. Those regulations and limits are there for a reason, you know.

  • Re:Cheap Fast Broadband?? (Score:3)

    by sredding ( 107116 ) on Thursday April 06, 2000 @10:21AM (#1147307) Homepage

    The AirPort and Apple arent the only systems that go wireless. There are others that support IEEE 802.11 DSSS standard.

    Check out:
    ZoomAir [zoom.com]
    BreezeNet [breezecom.com]
    SkyLine [farallon.com]
    MaxTech [maxtech.com]

    ...among others.

  • Re:Bandwidth congestion (Score:3)

    by n9fzx ( 128488 ) on Thursday April 06, 2000 @11:28AM (#1147308) Homepage Journal
    I wrote a paper on this topic for the 7th ARRL Networking Conference (available from TAPR [tapr.org]). Briefly, at frequencies above 1 GHz, it begins to make a great deal of sense to take advantage of gain antennas and spatial diversity. With omnidirectional antennas, you're spewing RF everywhere, causing your network to extend over a larger than necessary area. Directional antennas reduce the spatial occupancy. If you're worried about interfering with omnidirectional networks, take advantage of the polar diversity and separation available to you at these wavelengths: omnis vertical, directionals horizontal.
    -=paulf, N9FZX

  • Really Old-School World-Wide Network (Score:3)

    by albamuth ( 166801 ) on Thursday April 06, 2000 @10:46AM (#1147309) Homepage
    Perhaps that could be done. I'd just like to point out that before people came along, whales communicated through relayed songs thousands and thousands of miles all over the Earth--and I'm sure they weren't just saying, "hi! hello! age check?" Of course, engine noise and hunting has completely destroyed any remnents of the original world-wide relay chat system.

  • Distributed wireless IP (Score:4)

    by Anonymous Coward on Thursday April 06, 2000 @10:28AM (#1147310)

    This is one step toward a fully distributed wireless IP but not the last.

    Spread-spectrum wireless ought to take care of the congestion problem. If the power is low enough then the FCC has no business regulating it or requiring licenses--all they should do is certify that the equipment does not have too much noise.

    Then each node ought to communicate with its closest neighbors, instead of to a central cell. This way each computer dedicates a bit of its bandwidth and disk to the network, similar to the way Freenet ought to operate, and analogous to the way homeowners are required in many areas to dedicate part of their land for a public sidewalk.

    Internet traffic can then hop from node to node, routing around congestion and taking advantage of least-cost routes. Any landlines or satellites used ought to belong to the public and be free to use by all.

    I don't know if this is communism or anarchy or libertarianism or just free market capitalism in the extreme, but it sounds to me like the future, and a very interesting one!

    For more info on such a project, please see: http://wireless.oldcolo.com/biology/dave-bio.htm [oldcolo.com], and consult Dave Hughes, one of the real pioneers of computer-based communication.

    I'm not opposed to the Macintosh experiments. But we ought to spend some time thinking about how we can take advantage of some of the new technologies such as what Hughes is using, in order to expand our Freedom and use the Internet in a way that maximizes democracy and personal power, at a time when media giants are trying to take it over and make it safe for e-commerce.

  • Here's the law, for what good it does (Score:4)

    by orpheus ( 14534 ) on Thursday April 06, 2000 @12:37PM (#1147311)
    Apple says the Airport uses the 2.4 GHz band as an unlicensed ISM user (source: Apple Airport Wireless Technical Manual v1.1)

    Without actual access to the modified equipment, we cannot be sure that it meets the general requirements of 18 CFR 18.305 (or section 3 [gpo.gov] generally)

    For 2.4GHz ISM transmitters, used by consumers, under 500W, the transmitter field strength can be no greater that 25 mV/m at 300 m. Replacing a 9tested) nondirectional antenna with directional could cause this limit to be exceeded in some directions

    but how can they (or other LANs) use the ISM band? It was my understanding that ISM was intended for quite different use, and that telecommunications was specifically excluded. Isn't a network 'telecommunications"?

    I've heard the 2450 MHz mentioned as a LAN freq. before. Is it possible Apple was just being lazy in referring to it as by the general name ISM, when there's a specific authorization for this use elsewhere in the law. Or is everyone just relying on the fact that ISM is relatively unregulated?


    Authority: 47 U.S.C. 4, 301, 302, 303, 304, 307.
    Source: 50 FR 36067, Sept. 5, 1985, unless otherwise noted.

    Sec. 18.107
    (a) Radio frequency (RF) energy...
    (b) Harmful interference...
    (c) Industrial, scientific, and medical (ISM) equipment. Equipment or appliances designed to generate and use locally RF energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunication. Typical ISM applications are the production of physical, biological, or chemical effects such as heating, ionization of gases, mechanical vibrations, hair removal and acceleration of charged particles.
    (d) Industrial heating equipment...
    (e) Medical diathermy equipment...
    (f) Ultrasonic equipment... for industrial,
    scientific, medical or other noncommunication purposes.
    (g) Consumer ISM equipment... Examples are domestic microwave ovens, jewelry cleaners for home use, ultrasonic humidifiers.
    (h) ISM frequency....
    (i) Marketing...     covers leasing, sale, etc
    (j) Magnetic resonance equipment...


    Does someone know the law on this? Because if it's a matter of squatter's rights, the FCC states that even if they certify the equipment, they can yank the equipment off an ISM band, if they decide it isn't a ISM use.

    Sec. 18.111 General operating conditions.

    (a) Persons operating ISM equipment shall not be deemed to have any vested or recognizable right to the continued use of any given frequency, by virtue of any prior equipment authorization and/or
    compliance with the applicable rules.


    __________

  • Wireless links (Score:4)

    by AeiwiMaster ( 20560 ) on Thursday April 06, 2000 @10:12AM (#1147312)
    Here is a list of other interesting wireless links
    found at FreakTech [sunsite.auc.dk]

    Plasma antennas [anu.edu.au] are radiofrequency antennas that employ plasma as the guiding medium for electromagnetic radiation.
    DIRC [dirc.net] is a self learning, intelligent, and self organising network of small transmitting and receiving stations.
    Impulse Radio [time-domain.com] a whole new wireless medium.
    AIRNET [inficom.com] Adaptive Interferometric Radio Network Enhancement Technology.

  • Re:*cheap* wireless networking (Score:4)

    by hey! ( 33014 ) on Thursday April 06, 2000 @10:25AM (#1147313) Homepage Journal
    Webgear card pair can be had from outpost.com for $169.

    Don't use the Linux drivers on the webgear site, just upgrade pcmcia-cs to 3.0.14-22.

    Set up a private subnet on the Linux box and don't bother with the access point -- use peer to peer. There's no advantage to using the access point.

  • There's an easier way to do this, folks! (Score:4)

    by Some Id10t ( 140816 ) on Thursday April 06, 2000 @10:35AM (#1147314)
    The Apple "Airport" card is actually a repackaged Lucent Technologies WaveLan (now renamed Orinoco) card. The Lucent cards can be found here [wavelan.com].

    What's more, the Lucent cards have an external antenna jack on the side of the card. Saves you a little work.

    Before ripping a product apart with a dremel tool, check to see that you aren't re-inventing the wheel.

    - Some Id10t

  • Re:Legal equipment, legal with FCC? (Score:5)

    by imp ( 7585 ) on Thursday April 06, 2000 @10:15AM (#1147315) Homepage

    is it legal to actually use it in this manner?

    Yes. It is legal to use it in this manner. We in the village have one wireless link that uses old WaveLAN cards to shoot 5 miles (that's 8km). These frequencies are very picky. If you have trees in the way, you have to either use a higher gain antenna or cut the trees down. Snow can cause problems. However, despite the problems, it sure is a lot faster than a phone line, and cheaper on a monthly basis.

    We're using 24dB dish mesh antennas on each end due to the tree problem. W/o the trees in the way, we could easily shoot the 5 miles with a simple yagi 15dB antenna on both ends.

    Once we get out tower permit, we'll be putting up the anetenna to about 50' above the ground and, hopefully, switching back to the yagi and trying to bring on someone who is 8 miles away. Right now the antenna is only about 20' above ground level. We figured we'd need about 20-30 more to get above the trees. 10' above the roof is easy. 30-40' is much harder.

  • Re:Legal equipment, legal with FCC? (Score:5)

    by GoRK ( 10018 ) on Thursday April 06, 2000 @12:12PM (#1147316) Homepage Journal
    Ahem. Actually it is *NOT* FCC legal. It seems that there really are very few professional wireless networking people commenting on here, and to those of you who are reading this and feeling as pained as I, this reply is for you!

    I will explain the regulations here and hopefully clear up a lot of other misconceptions as well.

    The fines for this stuff, BTW, are very very large especially if you muss up and they get you for spurious emissions or accidentally putting out 10W of power or the like. And when you're blasting this thing over a radius of 3 miles, it's not like you're being quiet about it!

    2.4 gHz Telephones, 802.11 Wireless Networking, various medical devices, and microwave ovens transmit in the public domain ISM band. This band is a 22Mhz frequency range centered at 2.4gHz. ISM-band equipment may have a total EIRP (Effective Isotropic Radiated Power) of 36dB.

    This EIRP number is calculated as a maximum of 30dBi with up to 6dBm of gain at this power. The nice catch is that for every dBi of power you subtract, you can add 6dBm of gain!! This power output can actually be equivalent to about 4W of legal power depending on your antenna gain... as long as your dBi output is less than 30dBi.

    So, regulation-wise, yes. It is possible to use 2.4gHz 802.11 radios to go up to 30 miles legally, but why cant you modify your WaveLan/AirPort to go 30 miles? The reason is this:

    Because the ISM band is a public-use band, The radio, the antenna, the cable, and the amplification equipment MUST ALL BE CERTIFIED BY THE FCC AS A SINGLE UNIT!!! This means, that if a particular high-gain antenna and/or amplifier is certified to be attached to the Apple AirPort (of which there are none except its internal antenna) then you may legally use it.

    The WaveLan range extender is certified for use with the WaveLan equipment, but the apple airport is not a lucent WaveLan Silver in the eyes of the FCC. Thus the wavelan range extender is not certified for use on the airport -- which is what the first modification describes.

    The second modification describes attaching 'standard' antennas to the AirPort by manufacturing a special cable that will let you attach to the special connector on the WaveLan card. I should note here that the reason there is a special connector on this card is so that only certified antennas may be connected to it without voiding its warranty and lucent/apple's responsibility for its performance! Am I beginning to make sense here?

    The point is simple. When you open the AirPort or your WaveLan card and attach antennas or amplification that is not certified for use with the radio, you are breaking the law. Now, I personally don't really believe in the "certified as a unit" crap the FCC dishes out on public frequency equipment, but it is still the law.

    Now, to raise another point.

    11Mb radios are currently all DSSS. There aren't any frequency hopping 11Mb radios yet, although the 802.11 standard provides for them. The DSSS radios may use channels that are 2mHz apart, giving them a total of 11 usable channels in the 22MHz ISM band. The problem with this is that there are only 3 non-overlapping channels So to all of you out there who just think that you can extend your range all to hell and back, don't be suprised when four other people in your zip code do the same thing and find that none of you can even use your DSSS WLAN's!

    Frequency hopping is another story altogether. FHSS 802.11 radios operate at up to 2Mb and you can co-locate 17 of these radios in one room and you won't interfere! If you want to be very cool to other WLAN users in your area, do check out FHSS radios, as they are much more practical for most WLAN applications. Honestly, if speed wasn't such a big deal to everyone and their dog then we might not even have 11Mb wireless until the Frequency hopping hardware catches up.

    Please be responsible with your 802.11! If you don't, you're going to turn the wireless networking industry back to licensed microwave transmitters, and you'll probably just piss yourself off because all the public spectrum is gone.

    ~GoRK

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