[HOW TO] Diagnose Wireless Issues

Iccz

Distinguished Member
Sorry to have to say this, but:



This is a common mathematical error: the numbers quoted are all negative, so -48 is bigger than -93, not smaller. :p Think of it this way: if you start with a suitably large number, such as 200, and subtract 48, you'll end up with a larger result than if you subtract 93.

Seems to be a good post otherwise.
I don't follow, what was wrong with how I worded it? :confused:
 

swift00

Member
-43 is much closer to the positive numbers than -93 and so -43 is bigger than -93. Think of it on a horizontal number line. The lower the number is on the line the smaller the number becomes.
 

Beximus

Well-known Member
Thanks for posting that. My internet's been fading out the past couple of weeks - connecting at 54 mbps and dropping to 1 after about 10 minutes. I've used inSSIDer to discover my neighbours are on the next channel down. I've changed it and touch wood, so far so good.

Great advice.

EDIT: This seems to have worked a treat. Fingers crossed I have no more problems there.
 
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tom 2000

Well-known Member
Interesting stuff even if my understanding barely scratches the surface. Due to a switchover to cable I recently installed a new Netgear Rangemax Dual Band Router. I used it with the old Netgear dongle and looked forward to hooking up a new Dualband USB Adaptor acquired from Fleabay. However signal strength is woefull with that so back to the original adaptor and to heck with Dual Band. On looking into inSSIDDER I note the PS3 is on Channel 2 whilst the router is on Channel 1 so I will have to change that when I get a chance.
I have a history of dropping the wireless connection between PC and Router and having to manually "repair".
There are no houses within hundreds of yards so it is not interference from another WiFi network.
I was hoping the new Netgear would be stronger and more stable. It is actually weaker and the jury is out on stability.
 

mickevh

Distinguished Member
5GHz radio energy doesn't penatrate "stuff" (walls, doors, air,) as well as 2.4GHz.

The radio frequencies used by wifi are not the "wifi" radio frequencies, they are the radio frequencies wifi uses. Other things are allowed to use the same frequencies as long as they don't exceed a defined signal strength.

In the 2.4GHz band, microwave ovens, video senders and baby monitors are oft cited as interference sources. There are even car alarm systems that use these frequencies.

In the 5GHz band, there can be some issues with interference from/with radar and to play nice, AP's are supposed to shut down and/or shunt to another channel if they detect radar.

InSSIDer only sees wifi AP's, it doesn't show these "other" interference sources, and of course it doesn't show how close any other client devices are. Still, for a free tool, you can't really complain.
 
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tom 2000

Well-known Member
So can anybody tell me why the Router and PS3 insisted on using the same channel. I couldnt shift the PS3 so I selected Channel 6 on the router.
We will see if the PC holds it WiFi connection better now.

PS. The Playstation has now moved to Channel 6 automatically so it must be method not madness and I just do not understand the theory.
 
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mickevh

Distinguished Member
Client devices don't choose the radio channel, (if you're using "infrastructure" mode wifi - ie wifi that uses Access Points.)

Channel choice is in the gift of the Access Point (there's a wifi AP built into your "router.") Some AP's won't let you change channel if there is anything already associated (in session) with them, so you might need to change channel in the AP then reboot it (to cause it to drop all the sessions and start again.)
 
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tom 2000

Well-known Member
Thanks. So turn everything off and back on again?
 

tom 2000

Well-known Member
It didn't hurt at all although the PS3 trace has disappeared altogether but it is fully on line still.
 

tom 2000

Well-known Member
It didn't hurt at all although the PS3 trace has disappeared altogether but it is fully on line still.
And now the PS3 is back shown on Channel 6 same as the router. Should I just forget about this? The only reasons it bothers me is , a) i dont understand it, and b) it could be the cause of WiFi dropouts on the PC.
 

mickevh

Distinguished Member
Everything in your wifi LAN has to be "on the same channel" otherwise it won't work.

Your AP (router) advertises the channel it is using, and everything else "tunes in" to that.
 

tom 2000

Well-known Member
Thanks for that. I can rest easy now.
 

jonboy666

Active Member
hi , ive got a wireless router a belkin N1 . im connected through virgin media.im running 2 xboxs on live,laptop and 3 ipods and phones and mainly its fine but today it loses connection after about half an hour and i have to reset it.

my question is does anyone know wshat the correct set up of the router should be? by that i mean on the set up page for the router on the internet? because theres loads of options to turn this on turn that off and ive not got a clue,basiclly ive just left it as it is. should i have security on it ? does lose connection when someone else trys to connect?

ive done a speed and ping test and they are spot on,so its got to be something im not doing. sorry about all the questions.

cheers
 

Richard

Distinguished Member
Just had Sky broadband installed. I'm now having to connect my desktop pc via the wireless network.

I have a Dell Studio (D005403) pc with a Dell 1505 wireless N card.

The problem I'm having is my pc can only just connect to the wireless network with a very low signal strength. I'm getting a download speed of 0.37mbps.

Sitting at my pc now on my iPad I can see numerous neighbourhood wireless networks but not on my pc.

Any ideas what might be wrong?
 

Attachments

mickevh

Distinguished Member
I posted this elsewhere and it was suggested that it be pinned. Rather than create a new thread, it seemed apropriate to include this in the "wi-fi issues" FAQ.


Let us explore a few concepts on how wi-fi works and more importantly, how it does not...

How Wi-fi does not work:

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" that permiates the ether and all you have to do to get a link is to sit in the shadow of said "signal," tune in your receiver, and tada, there's your wi-fi link. Therefore, 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 "("dropped the connection/signal") or it isn't "strong" enough and needs to be "boosted."

But it isn't like this at all.

How Wi-fi does work:

Wi-fi works like walkie-talkies: Everthing is a receiver and transmitter. Everything - all the iSomethings, laptops, phones, "routers" and AP's transmit "signals." I can't shout it loudly enough - everything "wi-fi" transmits radio signals!

The radio 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, there is a "collision," the data gets garbled and needs to be retransmitted. Though of course, this is all happening thousands of times a second.

There's no assymetry, the Wi-Fi Access Point (AP) (or "router") has no more "right" to transmit than anything else and Access Points do not transmit any "stronger" signal than a client device. What makes and AP an AP is that it is connected to the wired network - it is the "point" at which a wi-fi client "accesses" the rest of the (wired) network, hence the name, "Access Point." There's an AP built in to a SOHO "router" (AKA SuperHub, HomeHub, etc.) - "routers" are not necessary to "do wi-fi."

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

When connecting a client to an AP they do a form of handshake to (for example) make sure that only authorised users are connecting, negotiate encryption keys, data rates, and other parameters that they agree to use to maintain their session. This process is called Association.

When one looses wi-fi connection, it's because some part of these mechanisms is breaking down. It could be that the wi-fi transmissions are getting so garbled (interferred with) that the association/session cannot be maintained. It could be that either AP or client is having some kind of software issue and dropping the session. It could be that the client cannot "hear" the AP or equally that the AP cannot "hear" the client. There's even a kind of electronic countermeasures mechanism which can be used to command devices to drop their sessions (which, sadly, everything is compelled by standards to obey.)

Unlike ethernet and IP, unicast (non-broadcast) wi-fi transmissions must be positively acknowledged. That is to say, that on receipt of a packet, the receiver must reply with an acknowledgment that the packet was received. Thus for a link to be maintained, the Access Point must be able to hear the acknowledgements from the client (and vice-versa of course.) Consider that when next "counting bars" and concluding that the "router isn't giving a strong enough signal." In could be that the router's transmissions are just fine and the problem is actually that the client isn't able to transmit a "strong" enough signal for the router the hear the acknowledgements.

The important point is that all wi-fi ills are not necessarily a "signal" issue and more specifically, not necessarily a "signal-from-the-router" (AP) issue. Battery powered client devices can be particulaly problematic because they have small antennas and (by design) try to be particularly miserly with their transmit power in order to extend battery life. iSomethings anyone...


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 car alarms (my favourite) are oft cited. InSSIDer and similar tools do not show you any such radio transmitters (nor any client devices) - it only shows the AP beacons. Still, for a free tool one cannot complain. Linux users can feel smug at this point because a (free) tool called Kismet for linux which handily does show all the wi-fi clients as well as the AP's.
 
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lindner

Standard Member
I have a Netgear N150 router and 4 devices that have been connecting to this wirelessly, running without problems for over 2 years. The main PC is hardwired.

Quite suddenly the other night we lost our wireless connection to all devices and it has not returned. The hardware connection to the main PC is still working fine.

All 5 lights on the router are green (including the wireless light), suggesting that this is working okay.

I notice that there is now another strong wireless setup nearby (Virgin), probably our neighbour. I don't recall seeing this on the wireless list before so am wondering if this could be compromising our set-up or could the problem still be with the router?

Any help would be greatly appreciated.
 

mickevh

Distinguished Member
It could be either.

Can you still see your router advertising itself? Is it tuned to the same channel as your competitors? Have you read the rest of this thread...?
 
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Triggaaar

Distinguished Member
Bump.

I was trying Ekahau HeatMapper and it couldn't see my wifi, so I searched on AVF and found this thread. I've tried the other options list in the OP, but can't seem to get any for free. HeatMapper looks like it would be really good, but I can't get it to work. I've added it to my firewall exceptions etc, but no joy.

Any recommendations for anything else that's free?

Thanks
 

mickevh

Distinguished Member
An interesting titbit for Apple users I recently found reading the "iOS Deployment Reference" which may be of interest to those with multiple Access Points - I paraphrase, but essentially it says the trigger for iOS devices to even consider "roaming" from one AP to another (with the same SSID) is Received Signal Strength Indication (RSSI) falling below -70db.

IE the "signal" strength from the AP one is currently associated with needs to get quite low before the client device will initiate a roaming attempt, otherwise it'll hang on to what it's got, even if a "stronger" signal is available.

This is probably testament to the behaviour reported anecdotally by others that iSomethings "won't roam" and it speaks to an assertion I often make that it's "Wi-Fi Myth #2" that client devices are constantly "hunting for the best signal."

(BTW - Not a facet of just Apple devices, plenty of other things behave in similar a way - lest Apple fanboys think I'm having a pop - it's just some concrete evidence from one vendor of something we've long suspected.)
 
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Just to confirm what mick said above really, although it does seem to be Apples AC implementation that is causing the issue.

I have three Ruckus ac AP's in my house, and on the N band my 5s and other older devices roamed perfectly.

Since we have mostly upgraded to iPhone 6, the AC performance is fantastic, however, they do refuse to let go of an AP until the bitter end, and in some cases will drop off completely to 4G and then back onto the strongest AP, but also, this appears to be random as sometimes they roam without issue (this also applies to my ac Macbook Pro.)

From what i have read, a few manufacturers are working on this with their firmware and are looking at implementing a method to kick devices that are 'sticky'.

Having said all that, the ac range on these Ap's is phenomenal, to the point that i have turned off the 5G network on the upstairs ap as the downstairs covers 99% of the house with near as dammit, full throughput.

Anyway, ios 9.2 might sort it when its released in November!

Before, my recent set up consisted of an Asus RT AC 68U and the coverage was also excellent, but throughput would drop off considerably as i moved further away, and as i worked from various rooms in the house, this just wasn't quite cutting it.

With that in mind, if anyone is considering upgrading their wifi network, then look at the various Asus wifi products which are very good. They are more expensive, but in this game, you do seem to get what you pay for.

And lastly, if you can, anything that can be hard wired via cat5, get a good gigabit switch and plug it in, and leave the wifi for devices that have no choice.
 
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mickevh

Distinguished Member
FYI: At time of posting, the free versions of InSSIDer seem to be no longer available from source, it's now chargeable or you'd have to find an old version from an "unofficial" repository.
 

mickevh

Distinguished Member
For those missing the "free" version of InSSIDer, I've happened across a similar (free) tool called "Acrylic Wi-Fi Home" which is very similar.

Usual caveats apply about how it only shows the AP's and none of the client devices, "synthesizes" the graphs and I wouldn't take too much notice of the "network quality" pronouncements, but one can't complain about a freebie and it certainly has it's uses if you "know what you are looking at."
 

avsnoob

Novice Member
what do you do when you have 20 + networks showing up and all channels? 1 6 9 and 11?
i have lived here forever and was an early adopter of wifi
my 1st wifi card was a linksys PCMCIA card for a dell latitude win 95 laptop

about 6 months ago i started to get a few wifi drops a day then 20, then 50 to 100 then totally unusable wifi , i noticed that i would see lots of comcast trucks in my neighborhood
around when this all started happening and this was around the time they started rolling out their new xfinity gateway(for those of you not stateside comcast is the monopoly ISP here and the"gateway" is their docsys 3.0 modem/wifi router all in one)
the old gateways only had a 2.4ghz band the new ones are dual band 2.4 and 5ghz
and also by default they leave open a 3rd channel walled off from the other 2 personal wifi SSID's for a public hotspot so that anyone who is a subscriber can log on to it anywhere there is a gateway which is everywhere now
now when i scan for networks(i use wifi analyzer for android) i see that most people around me have their own routers ,i see the same ssid twice for each band but on 2 different channels
for example joes wifi 2.4ghz channel 6 and joes wifi 2.4ghz channel 11
and then usually xfinity hotspot on the same channel as one of those with the exact same signal strength ,before when the ISP issued modem only rentals there were only 2 ssid's for each house one sometimes only 1 ,2.4 and 5ghs or just 2.4 ,now there are 5 SSID for each apartment
2 2.4ghz 2 5ghz and one xfinity hotspot ,i trned off the radios in my gateway and all 3 SSId'd from it and only have my routers 2 channels now and it still drops constantly
i complained to the FCC and they do nothing they let comcast handle it and of course they do nothing either and the FCC is a revolving door of comcast excutives
in over 20 years i never had any issues with my wifi now i can't use it at all
 

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