3G Microcell and Circuit Switch Fallback dilema

Tutor

3G Microcell and Circuit Switch Fallback dilema

While we still have a couple of non-LTE phones in our family, I have been thinking that those using LTE capable phones in a house with a 3G Microcell are basically never going to connect to the Microcell unless they turn off LTE on their phones....correct?

 

With Circuit Switch Fallback (CSFB), an LTE phone will stay camped on the LTE network until a voice call is attempted (non-VoLTE of course).  When the call is attempted, the LTE will hand the UE back to the underlying 3G W-CDMA network to handle the CS call. (once the call is ended, the 3G network is provisioned to hand the UE back up to the LTE network for data use.)

 

Since there are no hand-overs from the Macro network to the Microcell (instead there are only hand-outs from Microcell to Macro), I presume the CSFB feature would only hand down to the 3G Macro network,  and the UE would then never establish the call on the Microcell.

 

Reason this concerns me is that while the LTE coverage at my home is strong, the W-CDMA macrocell coverage is still subpar. (thus the Microcell)  But with this behavior of CSFB, the LTE phone users will only have the option to either hope their call is good enough on the 3G Macro network, or get in the habit of turning off LTE on their phones when home so they camp on the Microcell before making a voice call.

 

Seems like a real gap in the Microcell value proposition unless there is some capbility that I am not aware of for CSFB to work between LTE and Microcells.  Any ideas?

Message 1 of 4 (986 Views)
ACE - Master

Re: 3G Microcell and Circuit Switch Fallback dilema

No, that is not true. It depends on the phone and how it handles the signal to and from the MicroCell. I have an iPhone 5 that I leave on 4G/LTE all of the time. When I walk into my house, the phone hands over to the MicroCell from whatever protocol it's on (macrocell 4G/LTE) without any issues. The same is true when I leave my house. My phone is able to hand over to whichever macrocell protocol (4G/LTE) is strongest and connect once the phone is out of the MicroCell's range.

 

The MicroCell is a 3G device only. It cannot connect at 4G/LTE. If your 4G/LTE (macrocell) signal is stronger in-home than the MicroCell, your phone should stay connected to the 4G/LTE network but there may be an issue with your phone with competeing signal strengths. Some phones just handle that better than others. When you first activate the MicroCell, it will search for tower (macrocell) signals and adjust its ouput accordingly (see my Guide for Initial Acitvation, link in my sig).

___________________________________________________________

MicroCell Technical Guide by Otto Pylot


I am not an AT&T employee. For additional help, please send a PM to ATTCustomerCare

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
Message 2 of 4 (970 Views)
Tutor

Re: 3G Microcell and Circuit Switch Fallback dilema

The situation I was referring to is as you mentioned: " If your 4G/LTE (macrocell) signal is stronger in-home than the MicroCell, your phone should stay connected to the 4G/LTE network".   The phones do stay on the LTE network while in some more remote parts of the house, and I would expect that since the signal is quite strong.  As it turns out, that is not as much of an issue as I initially thought as the phones in idle mode do tend to attach to the Microcell readily in the majority of the house...at least they do now since I reset the Microcell.

 

The sequence I am questioning is if the phones do stay on a strong LTE signal and then when the user tries to make a voice (CS) call with the phone camping on the LTE network.  CSFB then kicks in to move the user to the 3G network to handle the CS call.  If in my house, camping on a strong LTE signal (with weak underlying 3G macro signal) I believe CSFB will still try to force the UE to the nearest/strongest Macrocell.  At least that is what I experienced initially.

 

It could be that the phone in the process of stepping down to initiate the CS call will not rely on known neighbors and will naturally be served by the Microcell (assuming it is in a good state at the time, and is stronger than any of the nearby Macros)

 

Even so, I dont' believe CSFB would work with the Microcell after the CS call is terminated, as the way CSFB should normally work with a 3G macrocell is that the user is moved back to the LTE network when the UE goes back to idle mode.  This requires a parameter (SIB 19) to be set on the 3G cells, and I doubt that is in place on the Microcells.  But I have no issue/concerns with the phones staying on the Microcell at that point as I would expect to be connected to home Wi-Fi as well.

 

So, in the end I don't think this is much of an issue after all.  Thanks for helping me think thru it.

 

I'll probably come back with a question on how the AT&T Wireless Home Phone works with the Microcell once my number is ported. Smiley Happy

 

One clarification question...when you say "When I walk into my house, the phone hands over to the MicroCell from whatever protocol it's on (macrocell 4G/LTE) without any issues."  You are referring to being in idle mode...correct?  It will not hand over Macro>Micro until any existing voice call is terminated as there are no neighbors in that direction...correct?  At least that was my understanding that active calls only hand-off in the outgoing Micro to Macro direction.

 

Thanks

 

 

Message 3 of 4 (955 Views)
ACE - Master

Re: 3G Microcell and Circuit Switch Fallback dilema

Typically, if you start a call on the MicroCell (in-home), it should stay connected and handover to the macrocell once in range. At least in theory. It depends on which type of handover takes place, hard or soft. The reverse may be a bit more difficult, again depending on the type of handover is present. See my Guide for more details on handing over calls. I've been using my iPhone in both situations and not lost a call. I'm not sure what you mean by neighbors unless you are referring to the MicroCell's neighbor (macrocell) list that it builds during the Activation Process.

 

AT&T Wireless Home Phone has had issues with the MicroCell in the past and there isn't a lot of help here but we'll do what we can. It's been quite awhile since we had any questions and it isn't an issue that is supported by MicroCell support. At least it wasn't in the past.

 

Connecting to home WiFi doesn't have any impact on the MicroCell unless you are downloading data on your phone. In that case, the phone will use your WiFi connection for the data (thus saving you from impacting your data plan) and leave the MicroCell 3G connection just for voice.

___________________________________________________________

MicroCell Technical Guide by Otto Pylot


I am not an AT&T employee. For additional help, please send a PM to ATTCustomerCare

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
Message 4 of 4 (950 Views)
Share this topic
Announcements

Welcome to the AT&T Community Forums!!! Stop by the Community How-To section for tips on how to get started.