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from here, you're allowed 30dBm of transmit power with a 6 dBi antennae (isotropic) for 802.11b. If they're broadcasting more power than that into the stadium, they're breaking the rules. Given the normal range of 802.11, I doubt they can broadcast into the stadium legally, even if they use a directional antennae to improve efficiency.

Everytime there's a story about 802.11b I wind up posting this link which provides a lucid explanation of the FCC rules in order to correct wrong information.

Please don't spread FUD, you make it sound like pretty much any antenna is illegal. 802.11 (Part 15) Devices and the Rules and Regulations interprets the FCC rules pretty clearly. You get 1 watt without an antenna. With an antenna the rules are crafted to encourage the use of directionals.

As for WiFi's radio range (due to power and antenna limits), you can easily get >10 miles in a point-to-point link by using a directional antenna at one or both ends.

This is not STRICTLY legal, because the directional antenna concentrates the power in a tight beam, which is thus more intense, and one of the limits is on the intensity (rather than the overall power).


You should take a look at 802.11 (Part 15) Devices and the Rules and Regulations. It interprets the FCC rules in an easier to read presentation. Directional antennas are allowed and even encouraged by the rules.

http://www.lns.com/papers/part15/

for a paper on this issue.

Tim

802.11 isn't a service or a communications protocol, it's a network layer. This is like complaining that 100 base-T doesn't have a MOTD

Brand new MOTD for cat5e!

As used by radio amateurs to satisfy the identification requirements of their license. (Amateurs using 802.11b kit can still use part 15 [or local equivalent in other countries] but in many cases they can also transmit at higher power if they comply with various conditions, including broadcasting their callsign).

See my paper at:
http://www.lns.com/papers/part15
for details on FCC Part 15.247.

http://www.lns.com/papers/part15/Regulations_Affec ting_802_11.pdf

It covers everything from co-users (interference)to Radio Frequency Radiation to human tissue, to antenna height and equipment certification.

By Tim Pozar - pozar@lns.com
for the Bay Area Wireless User Group

1. Background
   1. Introduction

      With the unlicensed use of 802.11b radio Ethernet devices in the Industrial, Scientific and Medical band that has been set aside for such use, there is confusion of what is allowed or limited by the Federal Communication Commissions Rules and Regulations. This paper is meant to help guide folks through the cryptic nature of these rules.

      This paper does not cover other legal issues of using these devices such as FCC type-acceptance, Radio Frequency Radiation issues (ie. ANSI RFR levels) or Appropiate Use Policies (AUPs) of ISPs you may connect to.

   2. What is the FCC's involvement in this mess?

      The FCC is a regulation body whose purpose was defined in the Communications Act of 1934 as:

      "For the purpose of regulating interstate and foreign commerce in communication by wire and radio so as to make available, so far as possible, to all the people of the United States a rapid, efficient, Nation-wide, and world-wide wire and radio communication service with adequate facilities at reasonable charges, for the purpose of the national defense, for the purpose of promoting safety of life and property through the use of wire and radio communications, and for the purpose of securing a more effective execution of this policy by centralizing authority heretofore granted by law to several agencies and by granting additional authority with respect to interstate and foreign commerce in wire and radio communication, there is created a commission to be known as the "Federal Communications Commission", which shall be constituted as hereinafter provided, and which shall execute and enforce the provisions of this chapter."

      The FCC, with the Act of 1934, was empowered to regulate wire and wireless communications. Wired communications regulation was needed to monitor and regulate monopolies. Wireless regulation is needed as the spectrum is finite. The FCC is the "traffic cop" to ensure that communications is not interfered with.

2. Part 15 of the Rules and Regulations

   Almost every bit of spectrum is regulated by the FCC with the exception of extreamly high or low frequency spectrum and bands managed by the Intergovernmental Radio Advisory Committee (IRAC) for the military and other goverment orginizations, by licensing operators of radio equipment. The part of the FCC's rules that cover the operation of equipment that does not need a license is (3) Except as shown in paragraphs (b)(3) (i), (ii) and (iii) of this section, if transmitting antennas of directional gain greater than 6 dBi are used the peak output power from the intentional radiator shall be reduced below the stated values in paragraphs (b)(1) or (b)(2) of this section, as appropriate, by the amount in dB that the directional gain of the antenna exceeds 6 dBi.

   • (i) Systems operating in the 2400-2483.5 MHz band that are used exclusively for fixed, point-to-point operations may employ transmitting antennas with directional gain greater than 6 dBi provided the maximum peak output power of the intentional radiator is reduced by 1 dB for every 3 dB that the directional gain of the antenna exceeds 6 dBi."

3. Lets dissect this section...
   • Part 15.247(b)(1) defines the maximum power that an intentional radiator can put out as 1 watt.

   • Part 15.247(b)(2) doesn't apply as it is covering devices in the 902-928 MHz band and 802.11b devices are in the 2400-2483.5 MHz band.

   • Part 15.247(b)(3) covers the need for limiting the amount of radiation the "intentional radiator" can emit with "directional gain" antennas. It says that in general (with an exception coming up) that if the gain of the antenna system is more than 6 dBi, the intentional radiator needs to be turned down to keep the emission at the 1 watt maximum plus 6 dBi (36 dBm or 4 watts EIRP). The FCC encorages the use of directional antennas. With that they give you 6 dBi more power for not poluting the rest of your space with radiation that is not needed to do what you need to do.

   • Part 15.247(b)(3)(i) covers the need for limiting the amount of radiation the "intentional radiator" can emit running "fixed, point-to-point" with "directional gain" antennas. This means that the transmitter is mounted not on a moblie device and is talking to one other transmitter.

Do we need to turn down the transmitter?

1. Omni-directional or Point to Multi-point paths...

   15.247(b)(3) makes the assumption that you are running a point to multi-point network much like an Apple Airport or Cisco/Aironet AP box with a number of computers connecting to the network. They may be randomly surrounding the access point so you are not using a directional antenna.

   But what does the FCC mean when they limit the "intentional radiator" to one watt?

   This is a critical sticking point in understanding what the FCC is talking about. There is some question of what an "intentional radiator" consists of and what and where exactly is 1 watt measured. Unfortunatly if you just look at these poorly written rules you will not understand what the FCC means here. One has to look a bit deeper to the "Report and Order" and Notice of Proposed Rulemaking" that generated this section of the rules.

   Things get a little clearer when we read this sentence in paragraph 4 of the Report and Order...

   • "The current regulations limit spread spectrum systems to a maximum peak transmitter output power of one watt. When operating at that power level, the maximum directional gain of the associated antenna may not exceed 6 dBi, resulting in a maximum equivalent isotropically radiated power (EIRP) of four watts, i.e., 6 dBW."
   With the old rules they are refering to the "intentional radiator" as a whole with a directional antenna can't exceed 6 dBw or 36 dBm and the antenna gain can't be more than 6 dBI. The transmitter can be up to one watt.

   In order to know if we are legal or if we need to turn down the transmitter we need to know the gain of your "intentional radiator". Let's say your access point actually puts out 1 watt of power and you want to put an omni-directiona antenna on it that has a gain of 5 dBi such as the ORiNOCO Range Extender Antenna".

   We know the gain of the antenna, the transmitter but we also need to know the loss of the transmission line going to the antenna as this attenuats the transmitter output power going into the antenna. Looking up the attenuation of a common coax cable such as RG-8 on an coax attenuation table we find that at 2.4 GHz we have 16 dB of loss with 100 feet of cable. With a 10 foot cable your loss is about 1.6 dB. So your new "intentional radiator" will be radiating transmitter power output plus antenna gain minus coax loss or (30dBm + 5 dBi - 1.6 db) or 33.4 dBm or 2.2 watts EIRP.

   Since this is a non-directional antenna you are limited to 1 watt EIRP or 30 dBm. The transmitter will need to be turned down 3.4 dB to 26.6 dBm or about 0.45 watts (450 mW) to get you back to 30 dBm or 1 watt EIRP.

   If you think about this you may ask, "why add an omni-directional gain antenna it if I already was at 30 dBm?" You would be correct that it would be a waste of time. But if you had something like an Apple Airport that will only put out 15 dBm or 30 mW then you can add an omni-directional gain antenna and it will extend your "roaming" area. In fact you can add up to 15 dB of gain with an omni-directional antenna before you need to attenuate the output of the Wavelan card in the Airport.

2. Use a directional antenna and get more power - or - this is where the Rules get even more hard to follow...

   Part 15.247(b)(3) actually gives you a free 6 dBi if you use a directional antenna your "intentional radiator". How do the do this? Only if the gain of the antenna is over 6 dBi will the Feds want you to roll back the EIRP of your "intentional radiator". You don't have to do it right at 1 watt EIRP. When would you do this? Say if you have an access point in the corner of a building and it needs to aim back into the work area. You don't want an omni-directional antenna as about 75% of the power would be going out the windows. Why not use a directional to keep the signal in the building and penetrate through the walls better? If we have antenna gain of about 12 dBi and in this case the antenna is a directional antenna. With the transmitter putting out 30 dBm and the coax has 1.6 dB of loss we have an "intentional radiator" that is putting out (30 dBm + 12 dBi - 1.6 dB) or 40.4 dBm or just over 10 watts EIRP. Since the antenna gain is 12 dBi and we have to reduce the power of this "intentional radiator" 1 db for every db we go over 6 dBi of the antenna we would have to roll the power back to 34.4 dBm or 2.2 watts EIRP (40.4 dBm - (12 dBi - 6 dBi)). Well, it is slightly better than 30 dBm or 1 watt EIRP.

3. Fixed, point-to-point paths and get even more power...

   There is another exception to this section of the FCC rules. Part 15.247(b)(3)(i) covers systems that are "fixed, point-to-point". That means this path only has two transmitters involved and they are bolted down by never moving their locations. Automobiles may not apply. An example would be if you have an access point and a user that is a couple blocks or even tens of miles away that you want to connect to.

   This exception is more lenient as you only need to turn down the "intentional radiator" 1 dB for every 3 dB of signal over the 6 dBi of the antenna system. The FCC does this as it knows that these paths will not likely not be omni directional on each end and will have less of a chance to interfere with others as well as the need to span some long distances.

   Lets look at an example using the same antenna, transmission line and transmitter as above. Without turning anything down we had an "intentional radiator" that was producing 40 dBm or 10 watts EIRP. Since the antenna gain is 12 dBi and we have to reduce the power of this "intentional radiator" 1 db for every 3 db we go over 6 dBi of antenna gain we would have to roll the power back to 38.4 dBm or 7 watts EIRP (40.4 - (12 dBi - 6 dBi) / 3).

Real world examples...

1. Omnidirectional Point-to-Multi-point...

2. Directional Point-to-Multi-point...

3. Directional Fixed, Point-to-Point...

   Recently I put up a short path between myself and a neighbor about 2 blocks away (.2 miles). I have an Apple Airport that uses the Lucent Wavelan Silver card that puts out 30 mW or about 15 dBm. The antennas have a gain of 24 dBi with a transmission line loss of about 6 db. This gives me an "intentional radiator" power of 48 dBi. Since the antenna gain is 18 dBi over the 6 dBi that the FCC gives you and since it is a fixed, point-to-point link I would have to limit my

   [...]

   Since the little Wavelan card only puts out 15 dBm, I am legal as far as part 15.247 goes.

Quicky Definitions...

1. deciBels - dB

   dB, or one tenth of a Bel, is a unit of mesurment that looks at the ratio of one value to another. Gain or loss can be measured in dB. The dB scale is an exponential scale using the formula log(ratio)*10. This means that 3 dB is about twice the power, 10 dB is 10 times the power, 13 dB is about 20 times the power and 20 dB is 100 times the power.

2. dBm

   dBm is deciBels referenced to a value of 1 miliWatt of power. Power over or under 1mW would be plus or minus dBm respectively.

   If you have a transmitter that produces 1 watt of power that would be 1000 times more than 1 mW so that converts to 30 dBm.

3. dBW

   dBW is deciBels referenced to a value of 1 Watt of power. Power over or under 1 Watt would be plus or minus dBW respectively.

4. Effective Isotropic Radiated Power - EIRP

   Effective Isotropic Radiated Power defines the gain of an antenna over an "isotropic antenna" that would radiate equally in all directions.

   An example would be a light bulb. A lightbulb is designed to radiate light equally well in all directions, except the direction that the base is in.

   If you have an antenna that radiates better in one direction than another, it would likely have gain in this direction. The amount of gain would be shown as "dBi" or dB gain (or loss) over an "isotropic antenna".

   To further our example above, if we have a light bulb and put it in front of a mirror, we would be taking the light radiation that would be heading in the direction of the mirror and reflecting it back in the same direction of the light not directed towards the mirror. Hence you would have twice the amount of light going in the direction of the refelction. As we are doubling the amount of light, we have a "gain" of 3dB or 3dBi.

• "One of my main "themes" in life is to give tools to the world that help them express their ideas. I have this rather utopian idea that if everyone has the tools to exchange ideas then the world will be a better place."

Unfortunately that is how the popular press works. They trying to gather "eyeballs" for advertisers. Where are the most eyeballs for their advertisers? It ain't Kabul. Keep in mind that CNN also is influenced and fed by the US government for some of their programming.

This article makes an indirect argument for helping alternative media outlets that do provide news with more context and is less United States centric. Keep that in mind in choosing your news outlet as you may be helping to reduce world intolerance.

This topic was covered in the Cringley Bank Shot discussion.

In short: EIRP (effective isotropic radiated power) is regulated, directivity ("focusing") is significant, and the rules are different for directive and point-to-point systems. See here for an overview:

The FCC's Part15 Rules and Regulation and 802.11b emissions in the ISM 2.4GHz Band

If you really want to know, here is a good explanation: http://www.lns.com/papers/FCCPart15_and_the_ISM_2. 4G_Band.index

I myself live in a bandwidth black hole which I just happen to be in the center of. So, I actually started researching and buying gear to hook into work's T1, which is about 4.8 miles away. The gear I decided on was two Orinoco (or WaveLAN as they used to be called) cards with Linux boxes to match to keep costs down (besides, Linux makes for a great wireless router). My antennas are 24dBi gain Hyperlink parabolic grid antennas. I already have the cards working in my Linux installations and am ready to hook up the antennas soon. The only tricky part is that my path to work is slightly obscured so I'm hoping I have enough power and gain to be able to punch though. Hopefully the bandwidth gods will look favorably upon me. I've never had a high speed connect at home (and probably never will if this doesn't work :/)

One of the coolest projects I found while researching this was the HPWREN project at UCSD. Check out their pictures, it's hella cool. In a nutshell they are running a 45Mbps (802.11a) wireless backbone across the Santa Margarita Ecological Reserve using mostly off-the-shelf equipment, for the purpose of hooking together the facilities strewn across it. They even have remote cameras hooked in that can be remotely controlled through the network, and other testing stations that send data back to them in realtime.
I dropped an email to the project lead and I asked him what kind of gear they used. He said they used a Western Multiplex Tsunami for their backend, Hyperlink for their antennas and WaveLAN and Cisco Aironet for their PCMCIA cards (you can now see how I constructed my parts list :)) I also asked how he got around mountains and such.
Well, in certain places they have powered relay stations. Naturally I wondered how they were powered, and he said some of them they could get electricity to, but others they actually have solar panels powering the relays. Damn. For you real hackers he mentioned there was a parts list for the solar power array somewhere on the website, but I never bothered to try and find it.

I've noticed some arguments regarding amplifying 802.11, and thought I'd help clear it up. FCC Part 15.247 governs the unlicensed ISM (Industrial, Scientific, Medical) band, and dictates that you can amplify the signal up to 1 watt (1000mw) This gets tricky when you start using directional antennas >6dBi gain though. You may find more detailed info here..

Actually when using a directional antenna, the FCC says you can go over 1 watt EIRP. If the antenna is over 6dBi you have to lower the "maximum peak output power of the intentional radiator" by 1dB for every dB your antenna is over 6dBi. Further, for a fixed point to point link, this is reduced to 1dB for every 3dB your antenna is over 6dBi.

You do need to know the cable loss between your radio and your antenna. With your 24 dBi example and 2dB of loss through the cable, and 1 watt EIRP == 30 dBm:

directional antenna over 6dBi (have to reduce output power by (24-6) or 18 dB):
30dBm + 24dBi - 2dB - (24dBi - 6dBi) = 34dBm (== 2.5W EIRP)

same scenario for a fixed point-to-point link (have to reduce power by (24-6)/3 or 6 dBm):
30dBm + 24dBi - 2dB - (24dBi - 6dBi)/3 = 46dBm ( == 40W EIRP!)

A good summary of this info is found here:
The FCC's Part15 Rules and Regulation and 802.11b emissions in the ISM 2.4GHz Band

check it out and double check my math!

802.11 is not regulated by the FCC.

A friend of mine has an Apple Airport set-up, which is 802.11b, in a three story house, and there are dead zones inside the house, on the same floor!

Your buddy in the other building might get some usage, with a high-gain directional antenna on your base station, depending on how well the signal can be reflected.

Or, you could put antennaes on the roof on the south side of both buildings... There are rules to worry about though.

Proxim amd others have complete set-ups for you to try.

Good Luck!

here's someone who /might/ be able to do consultation and engineering who seems to know his stuff.

As long as the setup adheres to the 1W limit and the gain specifications for the antennas there is no issue. The FCC permits this.

The 'limiting' factor that would keep people from exceeding those limits is the PC card itself. If you step up the power at the access point but the cards themselves can't be hyped up, it's just a waste. iow if the access point can 'hit' the card at 5 miles but the card has a short range...

I wonder how hard building a 2.4Ghz brick for the car would be ;-).

FCC 802.11b restrictions
More information

For you goat-phobes:
http://www.lns.com/papers/FCCPart15_and_the_ISM_2. 4G_Band.index

Tim Pozar's page The FCC's Part15 Rules and Regulation and 802.11b emissions in the ISM 2.4GHz Band discusses this and has links to the regulations and other useful references. Look for the section titled "Fixed, point-to-point paths and get even more power."

Tim Pozar's page The FCC's Part15 Rules and Regulation and 802.11b emissions in the ISM 2.4GHz Band discusses this and has links to the regulations and other useful references. Look for the section titled "Fixed, point-to-point paths and get even more power."

You get 1 watt. If you use an antenna you have to turn the power down on the card to compensate for the gain.

FCC regs and explanation:

http://www.lns.com/papers/FCCPart15_and_the_ISM_2. 4G_Band.index