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 Post subject: Wireless Network Lots of CRC Errors
PostPosted: Sat Apr 24, 2010 7:05 am 
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I recently bought a new buffalo WZR-HP-G300NH 802.11n router. I also purchased a trenda 802.11n USB adapter for my laptop because the laptop card only supported up to 802.11g. I've noticed that network transfers are slower now than when I was using 802.11g. With the RaUI utility I see the signial strength is 100% and I am connecteding at 150Mbps but I see a huge number of recieve CRC errors. The utility reports 39000 successful receives and 27000 receives with CRC errors. Do you agree that the CRC errors are the culprit behind the slower network transfers? If so what can I do to reduce the errors and why are there more errors when the laptop and router and in the same exact spots as with the 802.11g network I previously had? I already have the latest router firmware and drivers for the USB adapter.

Thanks for the input


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 Post subject:
PostPosted: Sat Apr 24, 2010 4:44 pm 
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Sounds like you are having layer 2 retransmissions. Bad news there are many possible problems: Multipath, RF interference, low SNR (which are layer 1 problems that result in layer 2 retranmissions) Other problems include hidden node, near/far, mismatched power settings, and adjacent cell interference could be your problems.

What band are you using? Are you still in the 2.4 Ghz ISM or are you running in the 5Ghz UNII bands? What channel are you using?

Let's get these questions answered and then we can go from there.


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 Post subject:
PostPosted: Sat Apr 24, 2010 5:15 pm 
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I've tried all the channels 1 - 11 and the CRC errors still exist. Channel 8 seems to be the best with 8:1 ratio of good to crc packets. I'm running in 2.4ghz band. Router does not support 5hz band. Laptop and router are all in the same positions as when I was using the 802.11g router.


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 Post subject:
PostPosted: Sat Apr 24, 2010 7:16 pm 
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Ok Channel 8 would be giving you adjacent cell interference. You should only use channels 1, 6, or 11. You are getting hit by everyone using channels 6 or 11. Do a scan and see what channels your neighbors are using.

Now the bad news is a 2.4 Ghz n router isn't going to give you the speeds you want. You can try and go with with 40 MHz operation in the 2.4 GHz range but it isn't going to work (it takes up the whole 2.4 GHz ISM band).

Technically once you get your crc errors down (which I think should happen when you find a good channel). You should see an increase in speed. n draft have some really nice things about them. I'm concerned that your router doesn't do 5 GHz. If possible I would take the buffalo back and get one that also supports the 5 GHz. Much less crowded up there. If you do that try and get one that is certified dual stream n or even better certifed multi-stream n. Not sure if your usb card would support them or not but they give you some nice features.

Lets see what happens once you get on the cleaner channel (either 1, 6, or 11). You want 5 channels of seperation in the 2.4 GHz band so keep that in mind.


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 Post subject:
PostPosted: Sat Apr 24, 2010 7:25 pm 
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Think you misunderstood my previous post. I've tried ALL the channels and channel 8 gives me the least amount of crc errors. Right now my maximum throughtput is about 20Mbps at 15 feet. I have a wireless phone but that runs at 5.8ghz. There are also 4 other networks in the area and channels 1, 6, and 11 are all being used. I also have an x10 security system. Could the x10 be the problem? If so why is it now causing problems and did not cause problems with the older belkin 802.11g?


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 Post subject:
PostPosted: Sat Apr 24, 2010 7:58 pm 
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Yes the x10 will give you some major interference. Because of interference your router is having to change it's modulation and coding. Sounds like it may have dropped all the way down to qpsk 3/4. Can you turn off the x10 and see if that gets any better? What channel did you run your old router on? Can you increase your transmit power on the router? Did the old router have a larger (might have bought it seperate) antenna?


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 Post subject:
PostPosted: Sat Apr 24, 2010 9:20 pm 
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I guess I can try turning x10 off. The new router is considerably more power in transmit so it can't be power.


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 Post subject:
PostPosted: Sun Apr 25, 2010 3:44 am 
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Its not the x10. Moved it and crc continued. Also I found the specs and x10 runs in the 300 - 400mhz band range.


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 Post subject:
PostPosted: Sun Apr 25, 2010 4:05 am 
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I fired up good old wireshark and I am see significant packet errors to the ip 82.70.167.70. I'm not even sure what this is the ip address of. I started a continous ping and I'm getting about 25% packet loss. IDeas?

BTW thanks for all your help.


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PostPosted: Sun Apr 25, 2010 5:07 am 
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You could have a hidden node problem. Can you turn on RTS/CTS on your router? This would be a good test. RTS/CTS can be a temporary fix for a hidden node problem.

Since you have a n router see if you have what is called dual-cts protection. If so turn that on (instead of plain old rts/cts). Now dual cts protection will normally affect the throughput because of the extra overhead but at this time you are not getting anything great anyway. So it may actually improve it for you. Also if it doesn't appear to improve much on channel 8 with it turned on try switching to one of the cleaner 1,6, or 11 channels and see if that has an improvement.

Also does your router have the ability to change the output power? And what is it currenlty set at?


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 Post subject:
PostPosted: Sun Apr 25, 2010 8:31 am 
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don't think it can be a hidden node since the only wireless node in my network is the laptop. Don't think it's a power issue either because even at 1 foot I'm getting crc errors. I've also ruled out the nic because I tried the laptop internal nic and same issues.


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 Post subject:
PostPosted: Sun Apr 25, 2010 9:14 am 
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A hidden node doesn't mean it has to be in your network. For example if I'm your next door neighbor and my laptop sees your router I can send it messages and use the band. But since my laptop is out of signal range of your laptop, your laptop (and mine) will never hear each other reserve the media (the 2.4Ghz). So thus we transmitt at the same time and have collisions (which is which the rts/cts will fix). In fact sitting on a adjacent channel like number 8 you are not hearing CTS frames from people using channels 6 and 11.

Power could be an issue because if you are sending out to strong a signal that could be where the hidden node is on your router's signal edge. Make the signal a little smaller and the hidden node can go away. Still won't solve the problem of adjacent channel interference.

Also not sure what type of security you have turned on. But AES is the only fully support one for n draft. If you use the others security methodes it drops you down to a/g rates.


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 Post subject:
PostPosted: Sun Apr 25, 2010 1:59 pm 
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I see two strang things on wireshark that I'm not sure what they are

1) 81.172.23.96 (an ip on SA) and the packet is for fiorano-msgsvc. What i fiorano-msgsvc? I googled it but not really a description of what it actually is.

2)58.246.161.186(an IP in china) going to port 62801.

Ideas?


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 Post subject:
PostPosted: Sun Apr 25, 2010 3:59 pm 
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Assume I have a good network connection how long should it take to copy a single 350mb file from a laptop to a NAS? I don't need a specific number just a rough idea.

Thanks.


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 Post subject:
PostPosted: Sun Apr 25, 2010 4:22 pm 
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BENCHMARKMAN wrote:
Assume I have a good network connection how long should it take to copy a single 350mb file from a laptop to a NAS? I don't need a specific number just a rough idea.

Thanks.


Well you said it was showing connected at 150Mbps. Since wireless is half duplex. The best you could hope for with that connections is a throughput of 75Mbps (saying that everything is working great). Shouldn't take it to long.


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 Post subject:
PostPosted: Sun Apr 25, 2010 4:35 pm 
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So assuming my math is right around 40 seconds at best. I was seeing at best 3 minutes at 10 feet yesterday.


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 Post subject:
PostPosted: Sun Apr 25, 2010 5:09 pm 
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Retry or CRC above 5% indicate that your network is not in tune. Did you try the rts/cts?


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 Post subject:
PostPosted: Sun Apr 25, 2010 5:57 pm 
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yup and didn't do a thing for me.


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 Post subject:
PostPosted: Mon Apr 26, 2010 4:49 am 
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Did you try dual-cts protection and move your channel to say 1, 6, or 11? I would try 1 or 11 as a lot of companies default to channel 6. Or if you don't have dual-cts try rts/cts on one of the above channels.

Where you live do you have a lot of neighbors around?


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 Post subject:
PostPosted: Mon Apr 26, 2010 8:17 am 
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I don't have an option for dual-cts protection .

How many times do I have to state I've already tried ALL the channels. ALL includes Channels 1, 6, and 11. No better, only worse, on the different channels.


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