Help with wireless connection

Pistachio

Member
I have been using a TP-Link TD-W8960N router connecting to plusnet ADSL since November 2011, and it has been doing a stellar job - good performance with no connectivity problems.

My wife switched it off when we were away last weekend, and for the whole of the week it has been dropping the wireless signal every couple of hours, before reestablishing itself. Plusnet think the line is fine and wired internet is working fine. I have tried multiple wireless devices and the signal stops broadcasting to all of them. I cannot think what has gone wrong as nothing has changed when it was switched off - I did notice that the router was getting very hot on the bottom of the device.

Any thought on what has gone wrong - or has my tp-link come to the end of its life. I guess if I need to I can still return it to where I purchased it (amazon) and exchange for a new router - would have preferred to got it working though.

Cheers.
 

mickevh

Distinguished Member
Check you have the latest Device Info firmware.
Ahhh - the myth that will never die: If something's broke, upgrade it.

Firmware doesn't "wear out" - if it was working last month, there's no reason why it shouldn't be working now unless something has changed. There's no reason to change your firmware unless you know that the replacement fixes your problem. Otherwise you're simply guessing.

I'd be a bit like popping into the chemists because you feel "poorly" - buying a few things at random, taking them all and presuming that somehow you will get "better." You might get lucky, you might not, you might even find that the "cure" is worse than the afliction or you introduce a new problem that's nothing to do with your original ailment.
 

Pistachio

Member
xyzbird said:
It is likely that whatever your settings were had not been saved so the router went back to previous on reboot. Enter http://192.168.1.1/, admin admin and reset whatever settings have changed. Could be that your Wireless -- Advanced settings need setting. Mine is on channel 13, 11n only, 20/40 MHz. Security WPA2-Personal etc. Perform Apply/Save and check by rebooting in Management. Then Export settings to a file to reimport whenever.

Check you have the latest Device Info firmware.
Cheers for the comments.

I have just changed my settings to mimic yours - fingers crossed that it helps make a stable connection.

I am pretty sure I already have the latest firmware already - Firmware Version: 1.4.0 Build 111108 Rel.40398n.
 

Curly99

Distinguished Member
Yes such patronising words mickevh. We should all bow down to you. I hope the original poster goes into his menu and tries one or two settings as he suggested he would like to do.

It was beneficial in my case to update because it fixed a problem in the wireless menu. Not all of us want to be stuck in the past. Anyway if the router is a few years old why not upgrade to a more up to date firmware. TP Link's site gives details of fixes and it's up to you whether you want to benefit or not. If you bought a new one it would probably be on that more up to date firmware. Trying to find out where I suggested that firmware "wears out".

Pistachio my W8960 gets fairly hot too.
Why such a rude reply to mickevh's post, I too used to upgrade to whatever was the latest firmware/drivers until one day the wireless on my netbook decided to play up and only a roll back to a previous version worked for me..sometimes the latest is not necessarily the best option..you only have to look at the virgin firmware thats forced on you for the superhub to know that ;) :)

Curly
 

Pistachio

Member
Mixed results so far. Firstly some of the wireless devices must still be using g, as when I switched it over they stopped working. That aside, the connection has definitely improved, but I am still getting sporadic disconnections, but they are less frequent than previously. Might have a try with another channel tomorrow.

Is there an app to view local wireless connections and which channels they are using?
 

mickevh

Distinguished Member
Yes. There's a few of them, InSSIDer is popular for Windows PC's as it is free.

Our "Wi-fi interference FAQ" in this forum will tell you all about how to use InSSIDer or tools like it and how to interpret the results.
 

Pistachio

Member
mickevh said:
Yes. There's a few of them, InSSIDer is popular for Windows PC's as it is free.

Our "Wi-fi interference FAQ" in this forum will tell you all about how to use InSSIDer or tools like it and how to interpret the results.
Cheers - will give the InSSIDer and the FAQ a look later.
 

Pistachio

Member
Ahhh.... I am still struggling. I have downloaded a wifi analyser - really helpful. Channels 11-13 were pretty busy, so I moved over to 6 (one other user and no overlap - though loads of BT open zone hotspots broadcasting). I can see that my connection is not dropping a bit or a lot, the connection just fails, even if you are right next to the router.

Do you think a complete drop of signal can be caused by interference?

Any other tips people could suggest?
 

mickevh

Distinguished Member
Let's step back a moment and do a bit of concepts on how wi-fi works...

Many people think wi-fi works like TV in that there's a big transmitter up on a hill continuously broadcasting something called "wi-fi signal" and all you have to do to get a reception is to sit in the shadow of said "signal," tune in to it, and tada, there's your wi-fi link. Thence, if wi-fi isn't working, something has made this "wi-fi signal" disappear or interferred with it and/or the transmitter has stopped broadcasting it or it isn't "strong" enough and needs to be "boosted."

But it isn't like that at all. Wi-fi works like walkie-talkies: The airwaves are "dead" until something has a message (data packet) to transmit. Thence the transmitting device wakes up, listens to the airwaves and if they are quiet, hits the push-to-talk button then sends it's message. If the airwaves are already busy, the would be transmitter has to wait for them to go quiet. If two things transmit at once, you get a "collision" and the data gets garbled and need to be retranmitted. Though of course, this is all happening thousands of times a second.

There's no assymetry in this, the Access Point (router) has no more "right" to transmit than anything else. What makes and AP an AP is that it is connected to the wired network - it's the point at which a wi-fi client accesses the rest of the network, hence the name Access Point. (There's an AP built in to a SOHO "router.")

One of the differences between an AP and a client is that and AP sends out a regular announcement to anyone that happens to be listening that it exists, called a beacon. It's this "beacon" that things like InSSIDer listen out for and show you (and measure the "strength" of.)

When you connect to an AP they usally do some checking to make sure that only authorised users are connecting to them, ie you need a passphrase, and they go through a handshake where client and AP negotiate encryption keys, data rates, and other parameters that they agree to use to maintain the session. This process is called Association.

So, when you loose you wi-fi connection, it's because some part of these processes is breaking down. It could be that the wi-fi transmission are getting so garbled (interferred with) that the association/session can't be maintained. It could be that a neighbouring device is commanding your devices to drop their sessions (this is a kind of "countermeasures" which unfortunately everything is compelled to obey,) it could be that either router or client is having some kind of software issue and dropping the session. The point is that it's not necessarily a "signal" issue and more specifically, not necessarily a "signal-from-the-router" issue.

Unfortunately, there's lot's of reasons it could be happening, which of course includes issues with your router.

The radio wavebands that wi-fi uses are not "the wi-fi bands" they are "the bands that wi-fi uses" - other things use them too, baby monitors, video senders, microwave ovens and (my current favourite) car alarms are oft cited. InSSIDer can't show you any of those (nor any client devices) - it can only show you the AP beacons.

One way you could rule in/out any issue with your router, is to see if you can borrow another one and see if that fares any better. Thence you can infer whether to pursue an issue with your router, or whether it's just a fundamental problem with the RF environment in your locale. I'd also methodically try all the available radio channels (a few days at a time) and see if there's any that are better than others.

Sadly, with some IT problems, there's nothing for it but to slog through systematically until you find the cause and thence resolution.
 
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limegreenzx

Banned
beerhunter said:
I could not agree more.

I often where on earth has this nonsense sprung from? Sloppy/amateur/ill-informed PD.
It stems from manufacturers who are not interested in looking at any problem unless it has the latest level of firmware etc.
 

Pistachio

Member
Thanks mickevh - that is a very useful explanation into wifi - needs to be on a sticky posting.

Unfortunately i gave my old router away some months ago, so cannot really test something another device. I will start going through each channel (only been on 1, 6 and13) to see how it impacts connecting to the AP. In the mean time I think I will look into which ADSL router I could buy to replace it (and send my old one back to amazon).
 

mickevh

Distinguished Member
Thanks mickevh - that is a very useful explanation into wifi - needs to be on a sticky posting.
Thanks - maybe I'll add it to the Wi-Fi FAQ.

...(only been on 1, 6 and13)...
In that case, you've probably already tried the most likely candidates. By all means work through and see if you get a better result, but I'm pesemistic that's you'll find nirvana and it may be you've got a router fault or a fundamental problem with the RF environement in your locale. If you do buy a new router, just don't be too disappointed if problems persist, which would indicate an inherent "RF environment" problem in your locale.
 

Pistachio

Member
xyzbird said:
It is likely that whatever your settings were had not been saved so the router went back to previous on reboot. Enter http://192.168.1.1/, admin admin and reset whatever settings have changed. Could be that your Wireless -- Advanced settings need setting. Mine is on channel 13, 11n only, 20/40 MHz. Security WPA2-Personal etc. Perform Apply/Save and check by rebooting in Management. Then Export settings to a file to reimport whenever.

Check you have the latest Device Info firmware.
So what difference does the bandwidth settings do - 20/40 MHz?

I just got off the phone with tp link, who suggested changing from 20/40 to only 20mhz, and also to also disable wifi multimedia. This seems to have helped, and for the last few hours the wireless has been back to its usual self - let's hope it stays this way.
 

Pistachio

Member
mickevh said:
Thanks - I did read this when I first looked at my problem and did not understand what this bit meant - but clearer now.
Wifi uses a "set" of 50 or so radio frequencies 0.3125 apart spaced out over 10MHz (ish) either side if the nominal centre frequency. Hence, a wifi radio "tuned" to C6 is also transmitting in the frequencies denoted as C4,C5,C6,C7,C8. Again, Wiki's 802.11 article illustrates this quite nicely. These are known as "20MHz" channels as used by 802.11 A/B/G.

802.11 N, in addition to 20MHz channels, allows "40MHz" channels, basically doubling(ish) the number of sub carriers which thence means the radio transmissions extend even further either side of the nominal centre frequency. So using 40MHz mode tuned to C6, the radio is transmitting sub carriers in the range C2 thru C10.

This is why 40MHz mode 802.11N can be a bit of a pain in the 2.4GHz waveband - 40MHz modes are taking up a lot of the available frequency spectrum and given the ever increasing number of wifi devices in the world, it's getting hard to find that much spectrum all to yourself (or at least, sufficiently free of interference to be reliable) unless you live in the middle of a large field.

For this reason, some people restrict their 2.4GHz "N" to use only "20MHz" channels to get a more reliable connection, albeit with a penalty of lower link rate.

OK, so possibly my last question - in the above post, what does it mean by " albeit with a penalty of lower link rate" in the last paragraph? Am I essentially using my "N" router as a "G", trading performance for a more reliable connection?
 
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mickevh

Distinguished Member
Wi-fi "link rates" (ever erroneously referred to as "speed") are a notional values that measure the amount of data a link can shift in some unit of time. In wi-fi links, what's reported as "speed" (link rate) is the sum of the amount of data each sub-carrier can transport.

So, to use a simplified example, if a wi-fi link was composed of 12 sub-carriers that could each transfer 8mbps each, the total aggregate capacity would be 96mbps (12 x 8) which is what your wi-fi devices would report as their "speed." If I halve the number of sub carriers, then I get 6 x 8 = 48.

Since 40MHz "wide" wi-fi links contain roughly twice as many sub-carries as 20MHz links, they have double the "speed" - or 20MHz links have half the speed of 40MHz one depending on how you like to think of it. By restricting your N router to "only" using 20MHz links, the link can't convey as much data as it could using 40MHz ones.

None of this makes any difference to A/B/G links as they all use 20MHz links. 40MHz links was something "new" introduced in the "N" wi-fi standards. If your N router is talking to a G device, it talks the G protocol and that's all. N devices can only talk N to other N capable devices.

In a mixed infrastructure with both G and 40MHz N capable N devices, the AP has to constantly flick between 20MHz and 40MHz transmissions and this can confuse some older devices, so sometimes we disable the 40MHz stuff to get a more stable link, but then that means that those N devices that are 40MHz capable have their link rates capped to what they can achieve with 20MHz links - which is about half capacity (though it's still usually faster that G.)

Wikipedia's article on 802.11N has a nice table showing the various permutations of channel width, guard interval, antenna counts and so forth and what (max.) link rates they could avail.
 
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