[HOW TO] Diagnose Wireless Issues

bryanbenji

Hi,

I've been sent here from the thread I posted at http://www.avforums.com/forums/networking-nas/1608992-losing-connection-my-wifi.html in order to try and find out why devices keep losing the connection to my WiFi network, but I'm really struggling to work out which utility is going to help me, and what I can do?? Can someone advise in simple steps what I can try and do please?

mickevh

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.

lindner

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

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...?

Triggaaar

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

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.)

niceguy235uk

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.

mickevh

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

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

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