# Poor wifi speed, dropped connections and low signal to noise margin.



## be4con (Mar 20, 2006)

I'm having problems with my new network setup.

I've recently changed ISPs from a 2Mb Pipex line to a 16Mb Sky line but have been forced as part of my T&C to change routers at the same time. I was previously using a BT voyager 2110 router. The new Sky router is a modified Netgear DG834GT. I have been told that it is possble to get the UN/PW from the router (so I could theoretically go back to the BT one) but it is hidden. I have also been informed that the router has been locked down by Sky to prevent firmware updates.

I am having problems maintaining ADSL connections with this new router and am wondering if this is due to the low noise margin I have. The noise margin is generally less than 7.2dB and often as low as 6.2bB, falling below 6.0dB on a few occasions. I have also had problems getting good wireless speeds and can't understand why.

Connected by ethernet I get download speeds of c14000kbps and uploads of c675kbps but on wireless I am struggling to maintain speeds of c2500/350 respectively.

I have tried changing channels, I have moved the router next to the wireless antenna (separated by <1cm). This has not helped and my speeds still don't get close to the ethernet speeds. My partners laptop (Broadcom 802.11g WLAN card) gets very respectable speeds (c13500/600kbps) in some areas of the house and poor in others. With the BT router she had good connections speeds throughout the house.

I recently fitted a new wireless card when my old internal USB card started playing up. The new card is a Linksys WMP54G. The wireless connection is reported to be excellent. 

I am running XP Home SP2. I have run TCPOptimizer, Spybot S&D, Adaware SE, AVG Antispyware scans and AVG antivirus and haven't found any problems. I have Windows Defender, AVG Antispyware, Prevx1, PreEmpt, SpywareBlaster, AVG Free and Look'n'Stop personal firewall running at all times. I have assigned static IPs to both my desktop and the laptop. 

So... Could my ADSL disconnections and poor wireless speed be due to my low noise margin? I have heard some routers are better able to deal with low SNR than others, maybe the Netgear is not one of these. What can I do to improve my SNR? Is it worth investing in a high gain omnidirectional antenna for my Linksys card or even the Netgear router or is that unlikely to improve things? Or, are the poor wifi speeds possibly just down to Netgear and Linksys not playing well together?

Thanks in advance for any advice.


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## O111111O (Aug 27, 2005)

Yes, low SNR means the signal you're receiving isn't that high above the noise floor. The noise floor being white noise, EMI from high voltage transmission, every hair dryer in the country running, etc, etc.


A high gain antenna would improve your receive sensitivity.


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## be4con (Mar 20, 2006)

O111111O said:


> Yes, low SNR means the signal you're receiving isn't that high above the noise floor. The noise floor being white noise, EMI from high voltage transmission, every hair dryer in the country running, etc, etc.
> 
> A high gain antenna would improve your receive sensitivity.


Thanks for the response.

Why might there be such poor speeds with the router and PCI card antennae right next to eah other? If i get a high gain antenna should it be attached to the router or the PCI card? Is there anything I can do to improve my SNR?


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## O111111O (Aug 27, 2005)

Well, there are a myriad of explanations. The easy answer is noise source, bad transceiver, crappy antenna, or simply compatibility.

BTW, too close can be just as bad as too far away.

What channels have you moved this to?

Did you check your area with something like Netstumbler to see what other channels are in use?

Are all of the wireless adapters on your network 802.11G? Do you have any 802.11B adapters? 

If you have 802.11B, what happens when you turn those off?

After re-reading your first post, the SNR margin that you're speaking of - this is wireless? You're not speaking of SNR on your DSL connection, are you??

To reiterate the previous question, if you're wired directly to router are download speeds acceptable?

What type of PCI wireless adapter is this? 

Did you compare items such as burst frame, CTS to self, etc against the Broadcom adapter that worked well?


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## be4con (Mar 20, 2006)

O111111O said:


> What channels have you moved this to?


Tried all of them (1-11), settled on 3 or 4 as best speeds. They seem pretty similar.



O111111O said:


> Did you check your area with something like Netstumbler to see what other channels are in use?


No didn't do that yet. Will do today and report back.

EDIT: I have run netstumbler. I'm not 100% certain I understand what I am looking at. On channel 3 and 4 I have 1 SSID listed. My card appears not to support noise recording, just signal strength. It averages a signal strength of about -37dB, and this deteriorates when I reposition the antenna on the PCI card.

If I change to another channel (say 6) I get a 2nd SSID. The 2nd reports signal strength of about -72dB.

I assume that this 2nd SSID is from another network. How do I interpret these figures? Is that a good signal strength with the 1st SSID?



O111111O said:


> Are all of the wireless adapters on your network 802.11G? Do you have any 802.11B adapters?


All 802.11G

EDIT: Actually just checked - my Roku Soundbridge music server is B but turning it off doesn't improve the wireless connection with my PC.



O111111O said:


> After re-reading your first post, the SNR margin that you're speaking of - this is wireless? You're not speaking of SNR on your DSL connection, are you??


No that's the DSL noise margin as recorded by the router whilst connected to the pc by ethernet.



O111111O said:


> To reiterate the previous question, if you're wired directly to router are download speeds acceptable?


Directly connected by ethernet I get speeds around 13.5Mbps. I have to reset the router at least once daily to re-establish dropped connections though. Ideally I need the PC to be wirelessly connected to the router because I have a network music server that I get rebuffering problems on if it isn't cabled to the router. When the wireless hop is between the PC and the router (as opposed to between the network music server and the router) then no rebuffering problems but my internet speeds are (relatively) rubbish.



O111111O said:


> What type of PCI wireless adapter is this?


Brand new Linksys WMP54G



O111111O said:


> Did you compare items such as burst frame, CTS to self, etc against the Broadcom adapter that worked well?


The who to the what? 
If you can tell me how I can and will


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## O111111O (Aug 27, 2005)

Ok, it sounds like we possibly have a couple of different issues here.

Let's tackle #1 - ADSL.

What EXACTLY does your ADSL interface say about SNR?

When you're connected with a wire, you say you're being disconnected/have to reset once a day. What do you mean by that?

#2 - Wireless

Can you check to see if 802.1x authentication turned on? You may try turning that off.


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## be4con (Mar 20, 2006)

O111111O said:


> Ok, it sounds like we possibly have a couple of different issues here.
> 
> Let's tackle #1 - ADSL.
> 
> What EXACTLY does your ADSL interface say about SNR?


Sorry, I'm not sure I understand this question, can you explain what you want and where I might find it?



O111111O said:


> When you're connected with a wire, you say you're being disconnected/have to reset once a day. What do you mean by that?


Oddly the last 48 hours things have been running better, but I'm not full of confidence this will continue. Essentially I find that suddenly I am unable to surf the net. This appears to coincide with periods when my noise margin is very low. Rebooting the router re-establishes internet connection.



O111111O said:


> #2 - Wireless
> 
> Can you check to see if 802.1x authentication turned on? You may try turning that off.


It's already turned off.


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## O111111O (Aug 27, 2005)

I'm trying to understand if you become disconnected from Internet due to ADSL issues, or simply wireless.

If you remain wired, do you become disconnected? If you do, let's stop there because I'm going to blame your router/ISP. 

If it's wireless only, I'm thinking that maybe the TNC (antenna jack) connector on the back of your wireless card may have issues. If your SNR is that low, and you're literally feet away from the router - no settings on earth can help that.

I asked you to disable 802.1x, because that's pretty common for wireless disconnects.

So, back to my 2nd paragraph. Do you become disconnected when attached with CAT5?


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## be4con (Mar 20, 2006)

Thanks again for your patient responses. 

I become disconnected when connected wired and wireless. As I mentioned in my last reply the problem appears to have improved spontaneously over the last 2-3days. Again today I find that I've not had any disconnections in the last 24hrs, so that's 3days now. This has coincided with my noise margin being a much more healthy (though not fantastic) 8.5-8.7dB every time I have checked over this period.

As I mentioned in my first post I didn't ever have any disconnections with my old router, always connected wirelessly. I never had any call to look at my stats though so couldn't tell you what my noise margin was then. So perhaps you are right, this is a router issue?


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## O111111O (Aug 27, 2005)

Yes, this is a router issue.

Since your ISP owns/provides the router, you have some SNR stats, and you become disconnected when wires - this is your ISP's issue.

xDSL encapsulation methods aren't always 100% compatible. If they have you connected to the same NPA on the DSLAM you could be seeing issues because of that. There's also the possibility that you're seeing this issue because your line rate has increased.

If it's become better, it could simply be because the DSL side of your router has retrained and is connected at a "slower" symbol rate.

Call your ISP, start complaining.

Please let me know what they say, I'm curious.


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## be4con (Mar 20, 2006)

O111111O said:


> If it's become better, it could simply be because the DSL side of your router has retrained and is connected at a "slower" symbol rate.


It's an ADSL2 line, I understand that they don't do that retraining thing that you see on some BT lines.

I'm going to try to set up my old router with the new ISP p/w and u/n and then collect some stats. Then I think I'll do as you say and start phoning and complaining. Unfortunately I have heard some horror stories about their tier 1 and 2 tech support and it may be some time before I get any tier 3 attention. I will post again when I've got any further info.

Thanks again.


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