Linksys WRT54gs v5

[tw]

Originally Posted by mbpark

The firmware controls the transmit power of the radio via software.

You can adjust up to the max using the software.

Mitch

Which is true with cell phones. But WiFi runs 100%. With any power reduction comes a data bandwidth reduction. Why would a WiFi port ever reduce power from 100% when that automatically means a reduction of signal to noise ratio and therefore a data bandwidth reduction below 54 Mb? I don't recall seeing any mention of transmitter power reduction or power control in 802.11 standards. Either it was on or it was off.

[glatt]

Originally Posted by tw

Which is true with cell phones. But WiFi runs 100%. With any power reduction comes a data bandwidth reduction. Why would a WiFi port ever reduce power from 100% when that automatically means a reduction of signal to noise ratio and therefore a data bandwidth reduction below 54 Mb? I don't recall seeing any mention of transmitter power reduction or power control in 802.11 standards. Either it was on or it was off.

I don't know jack about 802.11 standards and how they are acheived, but is it possible that the manufacturer designed the hardware to exceeding the 802.11 power standards? And to meet the standard, they could have used firmware to cripple the hardware's power and bring it down to the level of the standard? If so, then a change of the firmware could increase output to the level allowed by the hardware.

[Griff]

That's what I was thinking glatt. Is it possible that the output will exceed FCC limits?

[MaggieL]

Originally Posted by tw

With any power reduction comes a data bandwidth reduction.

If power is sufficent for a readable copy of the signal, data bandwidth remains constant, unless you tweak the modulation scheme...I'm not aware of any provision for that in 802.11.

For example, your Wi-Fi won't run faster if you shorten the hop distance from 20 feet to ten feet at constant RF power. And there's no advantage to running extra power unless the path loss has made the signal marginally readable...when adding power can reduce the number of unreadable packets, and this increases your range and/or aggregate data rate, as does changing the antenna gain to focus available power in a specific beam direction...that's what a Pringles can antenna does.


Above: the "Sniper Yagi" demoed by the Schmoo Group at DefCon in 2004. Alleged to have 10 mile (15km) range.

Originally Posted by Wikipedia

Wi-Fi uses the spectrum near 2.4 GHz, which is standardized and unlicensed by international agreement, although the exact frequency allocations vary slightly in different parts of the world, as does maximum permitted power.

Given the above, I'd guess that controllable power allows conforming the unit to regulations in various countries by changing the software config only.

I should add that S-band--the other name for 2.4 GHz--is not actually unlicenced...only the WiFi usage under FCC regs Part 15 is. Amateur Radio has a licenced primary allocation.

[Elspode]

It should also be noted that more costly routers *do* have a higher output. I believe that the power level for home gear is some combination of "don't step on the neighbor's toes very much" and "hey, want better performance? buy this more expensive Professional Router!".

[MaggieL]

Originally Posted by Elspode

It should also be noted that more costly routers *do* have a higher output. I believe that the power level for home gear is some combination of "don't step on the neighbor's toes very much" and "hey, want better performance? buy this more expensive Professional Router!".

The Part 15 power limit (one watt) applies to all unlicened devices in this band, and there's no higher limit for "professional" devices. That said, I've read that most WiFi equipment runs between 20mw and 200mw. So check your spec sheets if looking to upgrade a device. I suspect a device using the lower end of that power range does so not out of courtesy but to use cheaper parts.

Of course, Part 15 prohibits you from using a non-type-certified antenna too.

You may find this calculator useful

[Elspode]

So, in the continuing saga of trying to get broadband wireless to my kid at minimum cost, I purchased a used Microsoft MN500 802.11b wireless base station (router). According to what I am reading online, it is configurable as a bridge. I have followed the instructions describing this process, but so far, no joy.

Can anyone tell me this...When configured as a wireless bridge, shouldn't this device pick up my Linksys' signal and send it through a network cable to the desired computer?

[MaggieL]

Originally Posted by Elspode

Can anyone tell me this...When configured as a wireless bridge, shouldn't this device pick up my Linksys' signal and send it through a network cable to the desired computer?

I beleve a "wireless bridge" doesn't use an Ethernet connection...it receieves and retransmits the packets that it hears, making it possible for a packet to travel further than a single radio hop would permit.

In ham radio we call that function "digipeating".

[tw]

Originally Posted by MaggieL

I beleve a "wireless bridge" doesn't use an Ethernet connection...it receieves and retransmits the packets that it hears, making it possible for a packet to travel further than a single radio hop would permit.

That would be mesh networking if it involved more than one wireless point. I believe mesh networking is coming in 802.11s. We are still waiting for 802.11n to be approved. I believe the 802.11s design will be based upon a Motorola technology which in turn was learned from designing military mesh networks.

Motorola equivalent on a metropolitian area network is called Canopy. Aspects of that same technology also may be implemented in WiMax or WiBro.

Meanwhile, using a wireless router as a communication repeater between two wireless computers has long been available. But I don't know if it works between 802.11b and 802.11g access points. It should.

Some routers do permit multiple wireless points to bridge to distant computers. But the routers must be from same manufacturer and I believe it is limited to only (maybe) four wireless points.