RT-N66U Slow WLAN Download Speed

[ViRtUaLheretic]

First off let me say Thank you to this community, I have been trolling for a year or two but just recently became stumped with an issue I am having at work.

Basically the Wireless download speed of our N66U router at work is typically ~3Mbps whereas our wired connection typically gets 12Mbps+ (this is on 2.4 and 5Ghz).

Network Layout:
Dedicated 20/20 Fiber Connection routing to office
Cisco 5510 Firewall (managed by our datacenter provider to provide secure VPN)
RT-N66U
couple of switches going to hardwired machines

seperate dedicated cable connection for VOIP phones
VOIP modem and router


After banging my head on trying out every different options I updated firmware to the latest build and still had the same problem. I then "downgraded" to 3.0.0.4.276 and tried that to no avail.
Every time I flashed a new firmware I did a full reset and reconfigured everything manually from there. Each firmware provides the same slow WLAN download speed. Maybe worth noting is that our upload speed is and has always been fantastic. Speedtest.com always shoots straight up to 20Mbps and can show speeds up to 30Mbps.

Another thing I tried doing was moving the unit from the network closet where it can get pretty hot, to the room outside of the networking closet where it is always cold.

Here is a list of my current configuration of the router:
2.4Ghz:
Wireless mode: auto
Channel 6 (channels 1 and 11 are crowded but 6 is open)
bandwidth 20/40
Extension: auto
Wpa2
Aes
Network key rotation interval: 0

Multicast: disable
Preamble: auto
RTS: 2347
DTM: 3
Beacon: 100
TX Bursting: enable
Multicast: disable
WMM APSD: disable
Enhanced interface management: enable
TX power: 80


5Ghz:
N only
control channel: auto (nobody aroudn here is using the 5Ghz band)
bandwidth: 20
Extension: auto
WPA2
AES

(professional settings are the same as 2.4)
Router is currently set as an Access Point, but have tried Wireless router mode as well with same results.

At this point in time I am thinking that maybe prolonged exposure to heat in the network closet as well as having the TX power adjustment turned up to 100 took its toll on the router and now needs to be replaced?
Ive literally tried changing EVERY single option but cannot seem to get the WLAN download speed to increase over 6Mbps, and this is confirming with 3 different laptops and 2 phones.
As was stated if I hardwire directly into the N66u I can easily pull ~12Mbps down, but only WLAN is slow.

I have searched all over this forum and others but have came up short thus far. I am open to any suggestions. Thanks!


TLDR:
WLAN Download speeds are ~4Mbps, wired download speed is 12MBps+, and have tried 3 different firmwares and every available config option.

 

[sinshiva]

hm. my single core android phone can nearly hit my full 10mbit over wifi. out of curiousity, while in AP mode is the N66's WAN port connected to the switch?

you really should have 2.4ghz width set for 20mhz, but i've no idea how crowded it is there. tried it?

i'd be disappointed if leaving the router at 100mW caused it to burn out, think you should proceed thinking that's not the case; though, what kind of temps is it reading?

'Enable WMM APSD' enabled? along with optimize ACK suppression? (believe this is the same as dd-wrt's No Ack)

All your devices on N, at least? might be worth forcing N only. also, short preamble works better with N, i hear

Try playing with Tx bursting ? (i'd play with this after all of the above is set)

i guess, see where this gets you

 

[stevech]

The ASUS RT-N12 I use, when in AP mode, can use the WAN port or the LAN ports to connect to the LAN as an AP. Odd.
Best to not use the WAN port, I say, in AP mode.

TX Power: The low level firmware in WiFi products is set to know what max TX power vs. data bit rate that it can support, AND meet the WiFi allilance specs on transmitted waveform purity (EVM). Lots of User Interface software, DD-WRT included, misleads the user by offering choices that the hardware will cap out and ignore, because of EVM. If the hardwaware/firmware was to try to get, say 100mW, in the higher bit rate OFDM modes, it would send a distorted signal and cause errors at the receiver. Most of today's WiFi is limited to about 30mW RMS (repeat, RMS, as that's what's important for OFDM). In the lowest bit rates, it can get closer to 100mW RMS (because the peak to average ratio in low bit rate is less).

 

[sinshiva]

stevech, i originally would have disagreed with you about the wan port bit, but i learned some new tricks;

bridge name	bridge id		STP enabled	interfaces
br0		8000.ac220bd48848	yes			vlan1
								eth1
								eth2

i had for whatever reason, despite on many occasions looking at the output of 'ifconfig -a', thought the wan was a separate physical nic from the rest of the LAN

playing with brctl recently made me realize that this is not the case, however. actually, it was playing with brctl on dd-wrt that made me realize it when i accidentally killed my e2000 (have two, this one in particular only functions as a 'managed switch') and i had to 30/30/30 to get it fixed lol.

i wouldn't expect whatever method bridges eth0 to the vlan1 subinterface to be a significant hindrance, but i'm also not one to let software get in the way of good performance.

so lol, i guess i'll say at best it shouldn't matter. i'm using the wan interface on my e2000 with the wan port 'assigned to switch' via dd-wrt now simply because of the pretty lights.

 

[jlake]

It's perfectly fine to use wan port when asus is in ap mode. That's based on fact and not speculation.

Set 2.4 ghz to "20 MHz "

There's no need to set 5 ghz to 20 MHz width.

If you're still having problems, take the router to a friends/coworker/relative/neighbors house and test it.

 

[ViRtUaLheretic]

When I had the N66U in the network closet and had the TX set to 100mW it would get REALLY hot, almost to the point where it was unbearable to hold in your hand. Thats when I turned down the Tx and moved a ceiling tile out to help circulate air in the closet. We have since added a fan to push air around and the router is now mvoed outside of the closet.

I had originally set the 2.4Ghz to 20MHz channel but figured it would be better to leave it set to 20/40 to be able to handle both?
Ill change it back to 20Mhz

I have 5Ghz set to N Only, should I change that to 20/40 or 40MHz?

I currently have the router plugged in using eth1 Ill test out switching it to WAN to see if that does anything.
Thanks guys, Ill test everything once the office clears out in 2 hours.

 

[connorm]

personally i recommend keeping the 5GHz on 40MHz always. unless you can see there are tonnes of 5GHz networks crowding. but even when there is no networks crowding. 40MHz never seems to work on 2.4 for me. so i recommend just keeping it at 20MHz also make sure WMM APSD is enabled. i believe when i disabled that i only got 3mbps down before aswell. weird issue, hopefully u solve it.

 

[L&LD]

I see we setup our router's a little differently. You may want to upgrade to the latest 374.38_2-em version for the RT-N66U, do a proper reset to defaults and configure your router manually as outlined below.

http://forums.smallnetbuilder.com/showpost.php?p=98452&postcount=151


I saw a great improvement in throughput and range with the .38_1-em RMerlin firmware (the .38_2-em version is cleaned up even more).

 

[ViRtUaLheretic]

Thanks for the input guys.
I had made a couple of changes as per your suggestions but didnt get much in terms of results though.
Turns out the problem was because I wasn't removing the wireless profile from our computers.
Once I went into "Manage Wireless Networks" and removed the SSID profile and then reconnected to the Access Point the speeds JUMPED right up.
My Boss's laptop went from 3MBps to 14Mbps!

I might try and upgrade the firmware on the router back to the latest version and then recreate the SSID profile again to see if I can improve things even more, but that will have to wait until I can get a good maintenance window.

Just out of curiosity does anybody know how many users a N66u can adequately handle at one time? We have ~20 users here at our office and can easily get 30-40 devices connected at one time.

We are in early talks of maybe jumping to a Cisco enterprise level wireless access point in the near future.