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802.11 RF Amp
MikeLRoy writes "Linksys has announced a signal amp, to be available soon, for their wireless ap's/routers. While many people have been using commercial rf amps hacked onto their ap's, linksys now has a commercial solution!" I wonder when ISPs are going to stop soft-pedaling the anti-NATing provisions in their terms of service.
Some ISPs, especially the smaller guys or the co-op's, don't allow NATs for the simple reason that a un-clued user could hose the whole network.
A broadband ISP with midrange equipment (a few managed switches, a generic DSLAM and wireless gear, etc) could easily be crippled if a user were to plug his NAT in backwards. Plug the "LAN" side of a NAT box into the ISP's pipe and now it's broadcasting itself as a DHCP server. Not good. Giving each user a port on the core ISP router or a smarter switch would prevent this from happening, but would cost much much more.
That's only one reason, there are many.
What are the FCC regulations regarding the maximum legal RF Signal strength allowed in these wireless devices? Aren't they under the part 15 regulations (low power transmissions).
Or are the regulations written to put a cap on the intensity or "Field strength" of the radiations like the limits in the FM band (88-108mhz)?
Can someone comment on this?
I'd be a lot happier if the FCC got rid of some of those UHF TV channel frequency monopolies and gave the spectrum back to the public that rightfully owns it, to try to lower contention over the narrow strip of bandwidth that 802.11 uses. There's also much more use of wireless these days by non-mobile devices than there really needs to be, when those devices could perfectly well use wired ethernet, or maybe a much lower-powered shorter-range wireless scheme (like a higher-bandwidth Bluetooth) to an access point that's nearby (i.e. in the same room or close to it, not far away in the building). However, that last part is harder. Tragedy of the commons and all that.
The Wap11 Hack courtesy seattle wireless.
;)
Basically using a different firmware/snmp agent for a different ap based on the same chipset you can up the signal strength at no charge. It is risky however, so I take no responsibility blah blah blah. Maybe thats all the amp does is up the built in power..
I don't think you need to worry. What Linksys is doing is not nearly as interesting as people might assume (which is I suppose is par for the course for Slashdot :-) What I'm pretty sure is going on is that the wireless access point on the linksys doesn't have a very strong radio transmitter to begin with (I'm guessing 30-50mW), and the signal amplifer just raises the transmit power to the max legal limit for the 2.4GHz band.
The Cisco 350 Access Point (and wireless cards) has better receive sensitivity (I don't know if that's due to a better built-in antenna, or better radio circuity, or both), and a stronger transmit power than most other 802.11 cards (selectable from 5mw to 100mW). In contrast, the Lucent Wavelan Silver card has a 31 mW transmitter. I don't know what the transmit power for the Linksys access point, since it's not listed on the web site or in the user's guide, but they claim an outdoor range of 1500 feet at 1 Mbps, and 500 feet at 11 Mbps. For comparison, the Orinocco access point claims 1750 feet at 1 Mbps, and 525 feet at 11 Mbps, and the Cisco 350 access point claims an outdoor range of 2000 feet at 1 Mbps and 800 feet at 11 Mbps. If we assume that both Cisco and Linksys are exagerating to an equal extent for the best case scenario, it seems pretty clear that the Lucent transmitter is less powerful than the Cisco 350.
Of course, as radio amateurs know, transmitter power doesn't have as much effect on range as some people might think. That's why QRP operators can sometimes communicate with people halfway across the globe with only a Watt or two of power. So the Linksys signal amplifier will probably not make that much of a difference.
That being said, I would recommend the Cisco 350, not because of the higher transmit power, but because the access point has better manageability (you have much finer control over how the access point operates, with various nice features such as having the AP ask your radius server whether or not a particular MAC address should be allowed, LEAP authentication/encryption, etc.). Also the Cisco 350 PC card has a full-featured Linux driver, which allows you to control the transmit power, scan for all available 802.11 networks, and so on. Another nice feature with the Cisco 350 is that you can store the WEP keys in flash memory, so that you can lend the card to house guests, without needing to reveal the WEP key. (Right now, I haven't been able to find an open source radius server that supports LEAP, so I'm using a combination of 128-bit WEP keys plus MAC address access controls. One nice thing about the 350 Access Point, as compared to the Apple airport, is that you can change WEP keys without needing to reboot the access point. So while I haven't implemented it yet, it should be possible for me to automate changing the WEP key every 24 hours, by calculating a MD5 hash of a secret plus a timestamp. That way, a shell script on my Linux laptop would allow me to get update the WEP key at the same time, automatically.)
-Ted (N1ZSU)
That amplifiers amplify everything... including the ambient noise PLUS they also insert a certain amount of noise themselves (LNA stands for "low-noise-amplifier not no-noise-amplifier). So while the signals may be amplified, the noise level might also be amplified enough to negate the effect.
In addition, the FCC has a dba limit on the amount of signal you can have so you cannot just stick power amplifiers on all the devices in the network without incurring some exposure to fines and penalties (for interference).
It makes a lot more sense to design the wireless system to use numerous low-power devices spread around the area so that you can cover just what you need to cover and not simply saturate the area with signal.
No one ever had to evacuate a city because the solar panels broke!
The new NAT mechanism implemented in the Linux 2.4 kernels tries to use the same source port as the translated packet. I suspect other NAT implementations might be doing the same.
I wonder when ISP's are going to realize that it is futile to say "no NAT" or "no servers" or "max transfer gb per month" and realize that the only sane thing to do is to provide unrestricted access, and simply charge their customers what it actually costs to provide xx mb of bandwidth?
/don't/ have servers), and choose it over Company B because "UNLIMITED" means better to most people.
Because, if Company A has "UNLIMITED" in really big letters, but all of the restrictions (no servers, etc) are less prominent, and Company B says "We allow you to have servers, but we charge money per mbit" Joe user will go with company A almost everytime. Why?
Because "UNLIMITED" stands out, unlimited is certainly better than limited right? The average broadband internet user doesn't have a server, and chances are, they don't know how many mbps of traffic they make use of in a month. Joe user will see the part from Company A, not care about the restrictions (the fact remains that the majority of cable modem/dsl subscribers
The 'better' answer is to have multiple tiers of service, where the base plan is unlimited, but with restrictions (no servers, one computer, etc), and another plan where you can have servers, but only if you pay extra (per mbps over a certain amount, etc)... The problem is, most people who have a '*NIX box' with a web server wont want to pay extra, and will just get the cheaper plan, so 'policing' (port scanning their address space for people running servers on well known port numbers) for people running servers, would be necessary. Also, it would probably be prudent to have a 'power users' plan, where if you have over X computers (NAT'd or not) you have to pay X amount. Mind you, this would suck for a lot of people, since they'd have to pay more per month, but overall the cost of broadband for the average user should go down. It makes sense, it just depends on how you market it.