BC Incoming Calls LTE

[cgartly]

Hi,

I ported over from Rogers a week or two ago, everything has been fantastic.  Today at some point I stopped being able to receive calls while my phone is on LTE, the calling party receives a fast busy.  If I power the phone off it goes straight to voicemail. 

If I disable LTE I am once again able to recieve calls.

This is happening on two Public lines.

I have confirmed this is not happening on Koodo prepaid LTE.

Anyone else?

[sheytoon]

Sounds like it was an issue with the Telus TAC configuration in the core network.

For incoming calls when you're camped on LTE, your phone will be paged by the LTE core network (MME), and asked to drop down to UMTS/HSPA to answer the call. This procedure is known as CS-fallback or CSFB.

How does the MME know which towers to page? This is known as the Tracking Area in an LTE network A group of LTE cells that are physically close to each other will share the same Tracking Area Code (TAC). This way, when the core network is looking to reach a particular phone, it doesn't page the entire network, which would waste a lot of resources.

To recap, here is the overall procedure: 3G core receives incoming call request and knows that user is on LTE. 3G core asks LTE core to page the phone and begin CSFB procedure. MME pages all towers in the TAC to look for the phone. When the phone receives the page, it connects to the LTE network and is informed by MME that an incoming call is waiting. LTE network further instructs the phone to perform CSFB procedure and switch to 3G network to receive the call.

As you can see, this is a very long procedure and involves a lot of signaling between a lot of network elements. This is why incoming CSFB seems to take a very long time (~5 seconds) compared to VoLTE (<1 second). Any step that is missed could result in a call failure. In this case, missing the page could be the cause (just a guess).

[tangy07]

Make sure the network is set to automatic switch. If you set it to LTE only then it won't work.

[cgartly]

Must have been a network issue of some sort, it is thankfully resolved now.  Phone has always automatically switched from LTE to HSPA/3G when it rings or when a call is originated.

I'm using an iPhone 6+ - I did try powercycling the phone but it didn't make any difference, my wife's iPhone 6S was doing the exact same thing.

[vinions]

I'm in Vancouver and have had no LTE phone calling problems.  

[makkahn28]

PM currently doesn't Support VoLTE at the moment

[beerdude111]

Well I don't know the exact reason but Telus (and as a result, PM) don't have VoLTE in most of Canada yet, save for a few areas in Southern BC, that's where they're rolling it out from. Here, in Toronto, my phone automatically switches from LTE to H+ when I'm making a call. Maybe it has something to do with that? Maybe the VoLTE system in BC is having some issues. Might not be your fault.

Edit: VoLTE is available also in Alberta, apparently. Didn't know that.

[cgartly]

No I have good LTE coverage where I am, it started happening about 4-5 hrs ago I think.  Obviously my outgoing calls go out on 3G fine and when I have a call up call waiting works as the phone is not idle on LTE.  As soon as I'm idle on LTE I am no longer able to receive calls, data works though and I believe SMS works also.

I am in Kelowna.

[vento1]

Hi @cgartly

I too ported from Rogers about 6 weeks ago.

I just tried phone calls incoming/outgoing with LTE and LTE off and my phone is working.

I am located in Burnaby, BC.

Maybe you are in a bad zone area?