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Monday, 15 February 2016

Reduce wireless collision for dd-wrt and openwrt

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I’ve been experiencing high latency caused by wireless collision, low throughput and some others wireless problem on my linksys wireless. The wireless was set as an access point for multi client (hotspot) with wds support and all of them are flashed with DD-Wrt and OpenWRT. I made this post just to remind me about tiny tweaks to linksys wireless so i know where to go if next time i setup a new dd-wrt or openwrt wireless box.
I believe many of you know already the common wireless setting for reducing wireless collision on basic wireless setting. That is setting channel on free or less crowded channel. There’s a free wireless tool to monitor wireless channel information from your computer. The tool called inSSIDer. Although some wireless has a tool usually called site survey to monitor wireless access point on their range. But since interference mostly happened on both wireless access point and wireless client, so it is necessary to check wireless activity around the client too (for pc and android client). So you can decide which channel is less crowded in order to minimize collision.
inssider
By setting up the following tweaks also helped me to reduce wireless collisions, but somehow this tweaks reducing my max throughput  transfer too. It that doesn’t matter for me since the throughput is still higher than our internet speed.
  1. Set Fragmentation Threshold value between 800 – 1500
  2. set RTS Threshold value between 1800 – 2300
  3. set Preamble = short
  4. Set Shortslot Override = short
  5. Set Frame Burst and Afterburner = Disable
  6. Set Bluetooth Coexistence Mode (dd-wrt) = enable
DD-Wrt
  1. Open dd-wrt WebGUI control panel
  2. Go to Wireless -> Advanced Settings
  3. Sett every related option values as above
  4. Apply and reboot.
dd-wrt
OpenWRT
  1. SSH to OpenWRT box as root.
  2. Paste the following commands:
    nvram set wl0_frag=1200 #Fragmentation Threshold
    nvram set wl0_rts=2200 #TS Threshold
    nvram set wl0_plcphdr=short #Preamble
    nvram set wl0_shortslot=short # Shortslot Override
    nvram set wl0_frameburst=off #Frame Burst
    nvram set wl0_afterburner=off #Afterburner
    nvram commit
  3. Reboot wireless.
Note that above setting are based on my wireless setting. Please read dd-wrt Advanced Wireless Settings if you need further information regarding wireless collision.

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