Wireless transmit power level

Discussion in 'Tomato Firmware' started by dkirk, Oct 19, 2010.

  1. dkirk

    dkirk Network Guru Member

    I've got a WRT54GL-TM running Victek tomato-K26-1.28.8615MIPSR1_RAF-Std and started playing with the transmit level since I'm having trouble with signal levels around the house. I placed a laptop halfway across the house running a WiFi signal strength scanner, and I left it sitting in the same location for all tests. It was showing -58 to -62 signal strength. I tried values for the transmit power from 0 (factory default) to 1, 5, 42, 100, 200 and the laptop signal strength graph never budged. I reloaded tomato-ND-1.28.8525_RAF-VPN with the 2.4 kernel just to see if anything would change, and nothing did.

    I have a spare WRT54GL-TM and installed that with no change in results. I tried moving back to non-ND plain Tomato version 123 and again, no change in signal strength. I played with other wireless settings and nothing I tried would change the signal strength here in the house.

    What really bothers me is that my neighbor's WiFi shows up in my house with 2/3 of the signal my router sends...and the neighbor is 1/2 to 3/4 of a mile down the road. Why is my signal so weak in comparison to what the neighbor is transmitting. The neighbor is running a 2Wire router, and in the farthest room in my house my signal is equal to the neighbors. I'm two rooms away and the neighbor is over a 1/2 mile away. With the WRT54GL-TM is my only option to install higher gain antennas? Or am I just not understanding something here?
  2. Toastman

    Toastman Super Moderator Staff Member Member

    I'm curious. Granted that there may be some anomalies with the later versions of wireless driver, you're using an old 1.23 - they all worked fine as I recall and finding no change is not normal. Is your wireless country set to Japan? Try setting it to US which is known to allow the higher powers. Step between 10mW and 250mW and see if there's a difference.

    If not, it may be that the wireless card you have in the laptop is overloading on your router's signal, even on the lowest setting. Or the wireless card's measurement system is just not up to the job. Remember that the signal strength indicators in wifi cards is not concerned with strong signals, mostly it is designed to give reasonably useful readings ONLY on weak signals.

    Try running InSSIDer on the laptop, make sure it is far away from your router. Because it has a graphical display of everything on the channels, you will be able to see more easily if your laptop's card overloads or limits by moving further away as you look at the display.
  3. dkirk

    dkirk Network Guru Member

    I did set the country to US a few times but forgot others, now that you mention it. I was running InSSIDer on the laptop two rooms away from the router, both of which are on the second story/level of the house. The laptop was never moved and no matter what I did I was unable to affect that level. I was careful to always set the configuration back to factory default each time. I seem to remember this working on an older WRT54GL that I had back with previous versions of Tomato.

    I have two of these -TM routers and both exhibit the same signal strength so it's not a defective router, unless both are strange. I wish I had a plain WRT54GL now to test.

    Through this all I'm really bothered why the neighbors is booming, relatively, to my signal. If I go outside I can't see WiFi 25' away from the house, even near where the router is upstairs on the second level.
  4. Toastman

    Toastman Super Moderator Staff Member Member

    I never had a TM, I'm assuming it is similar to a GL. Weird. Try the Singapore setting as well, that seems to work for me on the older 1.23 versions.
  5. dkirk

    dkirk Network Guru Member

    I just tried with transmit level doubled from 42 to 84. InSSIDer continues to show the same sawtooth pattern of -57 and -58db, no change. I'm starting to wonder if the -TM is hard-wired somehow.
  6. Toastman

    Toastman Super Moderator Staff Member Member

    57 and 58 dB is pretty damned strong anyway, anything down to -70 is generally acceptable and gives full speed. So I wouldn't worry about it. BTW - InSSIDer actually has an internal bug which limits it to -50 or -60 (I forget which it is). Nothing above that limit makes any difference to the display. Check you aren't on the limit yourself. If you take a look at the graph I've just posted in another thread, of a router which is line of sight at 40m away, no walls or obstructions, you'll see it's similar to your strengths. http://www.linksysinfo.org/forums/showpost.php?p=369064&postcount=3
  7. ringer004

    ringer004 LI Guru Member

    Hardware wise, the -TM is supposedly the same as a WRT54GS-V3 (corerev = 9, 32 M RAM, 8M flash)

    Software wise, you need to replace the CFE in order to run alternative firmware (per the dd-wrt web site). Maybe the CFE is clamping the transmit power somehow?

    But the -TM I had for a while had pa0maxpwr=251 in my nvram dump...
  8. Toastman

    Toastman Super Moderator Staff Member Member

    Yes, that must be there or you can't change the power. Another thing to check. If not - nvram set pa0maxpwr=251
  9. ringer004

    ringer004 LI Guru Member

    There was a long thread about this issue a while back.


    I don't remember the details off hand, but I seem to remember the issue was from 1.19 to 1.23, and maybe only with the new driver (ND)??

    And Toastman, you were also involved on this thread if I remember correctly... :)
  10. dkirk

    dkirk Network Guru Member

    Just did and that is the value I show after a reboot.
  11. dkirk

    dkirk Network Guru Member

    Fantastic thread which I did not find with search, thanks. I remember that issue now. I like the one statement that said the -O option was being ignored with the ND drivers, this -O being the override. It still somewhat puzzles me that the DD-WRT guys have it working.
  12. dkirk

    dkirk Network Guru Member

    I took a spare WRT54G-TM router and installed the latest DD-WRT, left the laptop scanning where it has been all day, and put the new router in place of the old ... the signal strength increased from -57/-58 sawtooth to a new -50 flat-line. Not enough difference to warrant a change from my beloved Tomato. I tried adjusting the transmit level via the GUI and nothing changed. This may be a -TM thing or maybe the replacement CFE wasn't right. May have to finally break down and grab a new router, but what a shame, these Linksys boxes have been bullet-proof for me, and I hate to shelve them due to silly close-sourced Broadcom drivers.
  13. dkirk

    dkirk Network Guru Member

    <forehead smack> ... sorry, I should have first checked the sticky forum message labeled "Common Tomato Topics", what a great resource that I have never bothered to look at. Now I'm embarrassed to have even started this new and redundant thread, sorry folks. New Asus RT-N16 on order!
  14. Toastman

    Toastman Super Moderator Staff Member Member

    I checked my InSSIDer, it limits at 50 - so your new DD-WRT install might be even stronger than you see. But still the level didn't change? So looks like a TM-specific problem, but I don't remember having seen anyone mention it before.

    Have fun with the RT !
  15. dkirk

    dkirk Network Guru Member

    New Asus RT-N16 installed with latest v1.28.8650 version from VicTek. Using the same tools as before, the laptop and the Android phone, no real change in documented signal strengths. With the laptop in the same location in the NEXT room I'm seeing -57 signal, and I can almost see the router from this location. Neighbor 1/2+ mile away still booming in. Android still shows abysmal signal strength at the end of the house on the same floor, with the router being on the second story near outside wall. Per Toastman's article I boosted the transmit level to 50mw to see if any difference could be seen.

    Go downstairs with the Android and the signal strength indicator drops to zero just as it did with the Linksys WRT54G-TM. Dang it!

    Frustrated I take the Android outside and I'll be darned, surfing is just as fast as it is inside, with no visible signal strength, where before I was unable to surf at all. I have 3 acres ... I walk 2 acres away and behind a large 40' hip-roof barn and I'm still surfing (cellular radio turned off to ensure I was on WiFi). I get on the other side of this big barn and the surfing began to get noticeably slower, but I was still able to surf. Before this I was unable to surf literally 15 feet away from the house.

    In this long journey I have come to the conclusion that the signal strength indicators are worthless. The various Android WiFi utils are worthless, when it comes to signal strength. The InSSIDer laptop utility may be telling the truth about the signal strength but there must be something else I'm missing. I've got usable bandwidth over a very large swath of property that I did not have before, even though the various tools are telling me I shouldn't. Now I'm wondering if the Linksys WRT54G-TM *was* all the time producing more signal during all of the configs I through at it, and instead of actually testing it outside I was naively relying on the InSSIDer and Android tools? I was looking for quantifiable hard-core signal strength numbers and while I was getting numbers I wonder what value they really were, if any?

    The new Asus RT-N16 is most certainly an interesting piece of hardware, and I'm somewhat sad to see the Linksys go back into it's box, it was a darn good workhorse.
  16. brookie

    brookie LI Guru Member

    I have been adjusting settings on 3 wrt54g's in a wds setup recently. I kept losing one or another wds client. After all the reading I thought a power increase on all routers would increase signal strength. Wrong! After a couple of weeks of troubleshooting, I found a thread, where a guy said to decrease power in this case. I decreased power to 28mw on all routers. Both signals to main wds host from two wds clients increased. So, I got an increase in signal strength, and a big increase in signal quality. In some cases increasing power does more harm than good.
  17. Toastman

    Toastman Super Moderator Staff Member Member

    brookie, it's very interesting to know what is going on. By definition, increasing the transmit power MUST increase the signal strength, that is a law of physics. So if this didn't happen, then we have to look elsewhere for an explanation. When we get results like these, there are other possibilities:

    1) The intended power increase never took place, although it may have been indicated by the firmware - it may even have been a decrease. We know this can happen based upon information contained in the driver's country data.

    2) The receiver that was used to measure the signal strength did not report the true state of affairs for some reason such as overload

    3) The firmware is not actually measuring true signal strength, but is giving a computed figure based on something else (strength/throughput/wifi mode/internal driver settings/country/channel/on channel interference/ whatever - we really don't know).

    With these routers and wifi systems, we are mostly working in the dark. We know little about the internal workings of the drivers, and not much about the transmitter/receiver itself. What we do know is that it doesn't measure signal strength consistently or accurately - and that everybody's wireless card may give different results. The RSSI system wasn't intended to give accurate results, the purpose of it is to find out when the path is too weak to support a data link and allow the driver to look for a new AP. So the measurements are usually meaningful only at low strengths.

    During the last tests I did on the RT-N16 ( http://www.linksysinfo.org/forums/showpost.php?p=369064&postcount=3 ) a similar situation to brookie's was observed:

    Here are a few posts that might show what we're up against.


    dkirk, it seems that the android, like most handheld wifi devices such as iPhones, is useless as a monitoring tool. The laptop doesn't seem that much better either. InSSIDer suffers from known problems around -50 indicated RSSI - and probably you were too close to the router to make any meaningful measurements with it. Conducting your tests at a level of -60 to -70dBm will give better results, but means you have to keep running outside to look at your laptop - which means you won't be able to make many repetitive readings over time. Whereas I am using several remote AP's and looking at their web GUI, which is far easier. I am, and always have been, getting results with the RT-N16 that show nothing much is changed over the previous WRTGL ND wireless drivers - yet so many people say they have far lower signal strengths. I have no explanation for this except lack of control of the test environment.

    How do you like the RT ???
  18. premudriy

    premudriy LI Guru Member

    Hello, everyone! I might have a useful info. I found that while using InSSIDer, you must *not* be associated with any wireless networks.

    I was doing the same tests. When I was associated/connected to my home network, then InSSIDer would always show the same strength level, no matter what I did with power settings in the router. When I disconnected from the network on my laptop, then changing the power on the router was also displayed in InSSIDer as well. Try it.
  19. dkirk

    dkirk Network Guru Member

    Whether it is the RT or not, I sure do enjoy the expanded WiFi access. I really need to hook the Linksys back up and retry some tests outside. I'm fairly sure that the laptop was not connected to the network but I could be wrong, need to verify the premudriy information before this post. Been thinking about placing one of the WRT54G-TMs downstairs at the other end of the house in a WDS arrangement, for the experience and enhanced signal reach.

    Unrelated to the power issue, I'm loving the RT for the USB/NAS stuff, truly!
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