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Author Topic: Lost 40mHz band  (Read 25194 times)

Lycan

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Re: Lost 40mHz band
« Reply #15 on: September 17, 2008, 01:17:12 PM »

Hopefully PM will give me a copy I can post by tomorrow. I'll let you guys know.
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EddieZ

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Re: Lost 40mHz band
« Reply #16 on: September 19, 2008, 02:54:43 AM »

You're the greatest
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PeterF

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Re: Lost 40mHz band
« Reply #17 on: November 12, 2008, 05:17:34 AM »

It has been a while since the last post, and I wanted to know if the new firmware is in beta test.

I have a DIR-655 with a DWA-140 USB adaper, and despite trying every praticially every channel, I have been unable to get at 40mHz connection.

Netstumber doesn't report an interference on several of the channels I have tried, but still no luck.

Will the router send out a 20mHz for my "g" clients and a 40 mHz for my "n"?  or is it one or the other. 

BTW.  I am running AES and WPA2 on my "n" clients.  Thanks in advance.

Peter
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Lycan

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Re: Lost 40mHz band
« Reply #18 on: November 12, 2008, 09:26:06 AM »

The WiFi alliance has made it so that anytime our router sees a 802.11b/g broadcast (client or ap) it will lower the connection speed to 20Mhz. Although tragic it is currently unavoidable. We hope to find a happy meduim in the near future.
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PeterF

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Re: Lost 40mHz band
« Reply #19 on: December 08, 2008, 04:43:10 AM »

So here I was resigned to the fact that I would never go faster than 130mbs, when I rebooted my router after enabling uPnP.  Much to my amazement, the computer re-established its connection to the DIR-655 and reported 270 mbs!  A few seconds later the speed jumped to 300 mbs.   I logged back into the routed and confirmed it was using channel 7 as primary and 3 as secondary.  I've got neighbors on 1, 6, 8 and 11, so I guess I could squeeze the secondary channel in there.  After a little more playing around and configuring n-only,  WPA2 only and AES, I was able to get all the network devices in my house to see the 40 mhz channel.    Now the bad news.  The 40 mhz channel only stays active for a couple of hours.  After that I need to reboot, or change a setting and reboot to re-establish the secondary channel.  Is this the "good neighbor" kicking in after a couple of hours, or is there something I can do to improve the stability of the 40mHz band.  Thank you very much.
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EddieZ

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Re: Lost 40mHz band
« Reply #20 on: December 08, 2008, 12:32:49 PM »

You could look through the WiFi alliance implementation docs to see how this feature is required to work on a router. Might also be that a neighbouring AP kicks in just a little bit more or changes channel, enabling the feature in the DIR. Any logs?
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PeterF

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Re: Lost 40mHz band
« Reply #21 on: December 08, 2008, 06:50:42 PM »

OK...  Here are the rules on channel sharing from the Wi-Fi Alliance

Channel Select: A channel is deemed accessible at a node if the aggregate
interference power at the intended receiver is less than Ith (-62 dBm/MHz). The rules recognize
that a connection needs to be established between nodes before this rule can come
into operation. The channel width chosen is at the discretion of the node. A node
should be able to access any available channel in the allocation in question.


The key is that the channel width is chosen by the router based on a level of interference.  It doesn't say anything about "good neighbor" or abandoning a channel if anyone else is using it. 

Also, I checked my logs and there is not record of access point channel activity.

Maybe someone at D-Link can interpret the rule and discuss how the engineers plan to implement channel sharing.
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EddieZ

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Re: Lost 40mHz band
« Reply #22 on: December 09, 2008, 08:47:51 AM »

OK...  Here are the rules on channel sharing from the Wi-Fi Alliance

Channel Select: A channel is deemed accessible at a node if the aggregate
interference power at the intended receiver is less than Ith (-62 dBm/MHz). The rules recognize
that a connection needs to be established between nodes before this rule can come
into operation. The channel width chosen is at the discretion of the node. A node
should be able to access any available channel in the allocation in question.


The key is that the channel width is chosen by the router based on a level of interference.  It doesn't say anything about "good neighbor" or abandoning a channel if anyone else is using it. 

Also, I checked my logs and there is not record of access point channel activity.

Maybe someone at D-Link can interpret the rule and discuss how the engineers plan to implement channel sharing.

Use Wireshark to see/log how strong the neighbouring signal is. This might lead you to the cause of this disappearing channel.
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Lycan

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Re: Lost 40mHz band
« Reply #23 on: December 09, 2008, 11:37:06 AM »

Again, this is WiFi alliance. How they word things and what they make public is not controlled by us. As it stands this is our official PM response.

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EddieZ

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Re: Lost 40mHz band
« Reply #24 on: December 09, 2008, 11:46:27 AM »

I seem to remember that the WA also has some detailled/strict tech specs published somewhere.
Dlink  just has to comply to avoid a fierce whipping.  ;D
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Lycan

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Re: Lost 40mHz band
« Reply #25 on: December 09, 2008, 11:48:53 AM »

Yea, we were killing G routers. We've done it in the past with Static Turbo in the G series.
WiFi hates that.

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PeterF

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Re: Lost 40mHz band
« Reply #26 on: December 10, 2008, 04:34:17 AM »

Use Wireshark to see/log how strong the neighbouring signal is. This might lead you to the cause of this disappearing channel.

OK..  I downloaded Wireshark, and is certainly a very powerful packet capture tool.  However, I don't see how it does a better job than Netstumbler of identifying my neighbor's channel and signal strength information.  Perhaps the poster could identify which test to run in order to collect the necessary data on channel interference.

Just so I am clear.  What forces a downgrade to 20mhz.  Is it a competing signal on the secondary channel, or is it a competing signal on ANY channel?  I can see about 10 neighboring access points, however the strongest is approx 30db signal less than mine.  They are also all clustered on channels 6 and 11.  None are on my primary channel (7), or occasional secondary channel (3). 

What I am looking for is an explanation of the circumstances which lead to a 20mhz downgrade (not just, "you've got neighbors").  Also how is the secondary channel determined?  In my case, it is four channels below the primary.  Ultimately, I want to understand how to improve the 40Mhz channel.  For example, move my DIR-655 to the center of the house (away from exterior windows and walls), or change the primary channel.  I can't get rid of my neighbor's access points, but I am sure there are things I can do to improve the performance of mine.  Thank you.

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EddieZ

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Re: Lost 40mHz band
« Reply #27 on: December 10, 2008, 05:03:22 AM »

Wireshark is more or less the same as Netstumbler.
You can let it be active for a day or two and save the log. Pinpoint the times 40Mhz suddenly dissapears and look in the logs what the neighbouring signals looked like at that time.

You might want to email the Wifi Alliance with these questions, they made up the specs so they will be able (but willing?) to andwer you correctly. Possibly they will refer back to Dlink for the implementation, but looking at the specs there is not much Dlink can add to that.

 
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Lycan

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Re: Lost 40mHz band
« Reply #28 on: December 10, 2008, 09:11:21 AM »

Any 802.11b/g beacon. Be it a client or AP side.
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EddieZ

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Re: Lost 40mHz band
« Reply #29 on: December 11, 2008, 08:33:30 AM »

For example, move my DIR-655 to the center of the house (away from exterior windows and walls), or change the primary channel.  I can't get rid of my neighbor's access points, but I am sure there are things I can do to improve the performance of mine.  Thank you.

Just change the channel option to manual, pick a channel and you will see that the secondary channel will set itself in the next none overlapping channel range (1,6 and 11 are the only non overlapping channels).
So stay out of the way of neighbouring AP's. Choosing one of three channels mentioned above should give a good indication what part of the spectrum works best.

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