DD WRT on WRT54G

Discussion in 'Windows 7 Networking' started by kevin from Chi-town, Jun 22, 2009.

  1. kevin from Chi-town

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    I flashed my Linksys wrt54g to use dd-wrt firmware. The advanced routing functions of DD WRT are amazing. However, I'm not so sure about the transmission rate. The default tx rate is 70. I've read in the past that excessive tx rates will cook the router. But I need to turn up this rate to overcome some of the natural impediments such as double row brick walls, plaster, and several floors. Has anybody used this and if you have , whats your experience with moving off of the default tx rate?

    thx in advance
     
  2. cyclingroo

    cyclingroo New Member

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    If you are looking to boost your signal, you're interested in Tx Power (not rate). The default power setting varies from version to version. However, it is generally 19mW-21mW. When HyperWRT hit the scene, most custom modders bumped this to 28mW. Most systems will handle boosting the signal even further. But as you boost the signal, you will be increasing the error rate as signal-to-noise is decreasing. The dd-wrt team selects 70mW as their default. And many others think it is higher. "The Ultimate Hacking Guide" states that 89mW is about as high as you want to go. But anything beyond the h/w default invalidates your warranty. Of course, using any custom firmware can do the same thing.

    As for me, I use 28mW as a starting point. I have found that I experience little overheating and limited noise if I remain below 50mW.
     
    #2 cyclingroo, Jun 22, 2009
    Last edited: Jun 22, 2009
  3. kevin from Chi-town

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    perfect...thanks for your help. Warranty was never an issue, the house I own is. I'm even now thinking about getting another to use as an access point. But I do appreciate the info...
     
  4. cyclingroo

    cyclingroo New Member

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    Try at both a higher and lower value. Sometimes, the higher values (above 89mW) will cause horrible noise and packet retransmissions. I found that if I used a value lower than DD-WRT default of 70mW, I actually got better throughput due to a more stable connection.
     
  5. kevin from Chi-town

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    what do you suggest?...I've seen where some Linksys models use 35 mW. So the default on DD wrt is already raising that signal 3dB. And is there anyway to monitor the signal, a sort of crude way of knowing which direction works best for me? I'm thinking either download testing or maybe online video stream monitoring. What would you suggest?
     
  6. cyclingroo

    cyclingroo New Member

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    There is no single, right answer. Here's the path I'd suggest. Use DD-WRT. Start with 28mW. See whether you can get a stable signal. At that power, the signal will be clean and clear, but a little weak. Then try 70 mW. Finally compare this to 89mW. I WOULD NOT suggest going higher than that. Too much noise and too much heat.

    While you test at these levels, do a real test. Start with a site survey tool (like the one provided by DD-WRT). You should get a good sense for whether power changes are actually helping. Also, you problem may not be your AP. Sometimes, it's the client. Do you use PCMCIA, a USB adapter or a PCI adapter? If PCMCIA, does your card support an external antenna. Oftentimes, you can fix connection/quality issues with an antenna on the client.

    Finally, you noted obstructions like double-thick brick, etc. Sometimes, augmenting the antennas on the WRT54G can be replace with better omni-directional antennas or by switching to a directional antenna (if the floor layout between the AP and the client permits it.

    As a side note, please ensure that you have a secure router configuration. By increasing the signal drastically, you make your systems even more visible to prying eyes. So ensure that you have a strong encryption and authentication system. In my case, I switch from default channels and I use WPA2. But I layer MAC address filtering and I do not broadcast my SSID. Is it foolproof? Of course not. But you just need to be more secure than the other AP's within range! ;-)
     
  7. cyclingroo

    cyclingroo New Member

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    There are lots of network benchmark tools (TCP/IP Network Performance - Benchmarks and Tools). And there are a bunch of wireless testing tools (Best Wireless Testing Tools - Spiceworks Community). When I am doing AP testing, I set up a laptop as the data collector/control. I use something simple like NetStumbler. I collect at least fifteen minutes worth of data at each power setting.
     
  8. kevin from Chi-town

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    I did try inSSIDer which is at inSSIDer | MetaGeek . Free utility that monitors signal as you walk around on laptop. The question I have is this. The tx power was set at 35 mW and my signal strength was floating around -75 dBm. When I set the tx power back to 70mW, my signal went to -55dBm. Don't I want to keep the 70 mW to bring me closer to the theoretical 0 dBm which is true signal?
     
  9. cyclingroo

    cyclingroo New Member

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    I am wholly unfamiliar with inSSIDer. So I can't speak to the numbers you've quoted. As a general rule of thumb, the received signal power range for 802.11 devices varies from -60 to -80 dBm with a theoretical maximum signal of -10 dBm (dBm - Wikipedia, the free encyclopedia). [Note: my ability to convert to dBm is not as good as it used to be.] If you don't see a lot of lost packets at 70mW, then use it. My point was that some systems actually transmit less real data if the power is substantially boosted because there is so much noise and data retransmission. Again, most second-hand anecdotes indicate that you SHOULD NOT boost the signal beyond 89mW.

    Have you found that by boosting to 70mW, you are getting better data transmission throughput (as measured by tools like BroadBand Reports (Lost in a forest.. - dslreports.com If so, continue to use 70 mW. Just ensure that you have adequate ventilation where you place the AP.

    BTW, were you able to use an external antenna for the computer that is having trouble?
     
  10. Mike

    Mike Windows Forum Admin
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    I also use DD-WRT on my WRT54G. There was some discussion awhile a go that increasing the mW after a certain point doesn't actually do anything - it is just a false indicator in the software since it is hard limited on the device. Someone on a forum actually tested this extensively, but don't take my word for it.
     
  11. kevin from Chi-town

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    I appreciate the input gentlemen... In my setting ( Double row brick house with plaster walls, 3 floors with router on 3rd floor(only place possible)) the laptops in question seem to receive the signal regardless of what Tx power I'm using. The strength seems better at 70mW however it seems to hang every now in again on both settings (35 mW and 70 mW). This is more of a nuisance than a deal breaker. You have to know however, that this house is built like a tank so the houses natural impediments are more than likely the cause, or so I'm starting to think!

    PS. I did try 89mW for kicks and it was about the same as 70mW @ -55 to -60dBm. And I'm actually going to buy another router off newegg to daisychain as an AP downstairs rather than an external antenna. That should keep me busy for a day!
     

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