On 02/24/2011 04:34 AM, Arun Ravindran wrote:
>>> -----Original Message-----
>>> From: ofono-bounces(a)ofono.org [mailto:firstname.lastname@example.org] On
>>> Behalf Of Denis Kenzior
>>> Sent: Wednesday, February 23, 2011 5:50 PM
>>> To: ofono(a)ofono.org
>>> Cc: tomasz.gregorek(a)gmail.com
>>> Subject: Re: [PATCH] atmodem: CEREG support for LTE network status
>>> reporting in AT modem
>>>> After discussing internally with Fred Joly I would like to come back
>>> on the 4 properties :
>>>> - Suspended is applicable in LTE in case of CS Voice Call using CSFB
>>> My understanding was that CS Fallback physically switches technologies.
>>> It is not 'suspending' LTE like it does with GPRS. Am I wrong on
>> I would say yes. :)
>> In case you are obliged to fallback from 4G to 2G without support of
>> DTM, exaclty like in GPRS.
> From what I understood you physically lose the EPS network registration
> and fall back to 3G / 2G. How is this the same as the suspended
> property where your attached status does not change?
For CSFB there are two settings. First one is that the UE should be
A voice centric UE will always try to make voice service available
either using IMS or by CSFB.
And if it cannot avail voice service using the above mechanisms, then it
should leave E-UTRA and re connect to GERAN/UTRA. A data centric UE in
turn will not leave E-UTRA if it cannot make a voice service available.
(23.221, section 7.2a)
The second is that the voice call mode (domain), this can be set to CS,
CS preferred, PS or PS preferred. A UE with CS or CS preferred will
always try to make voice service through CS (CSFB or by re connecting to
GERAN/UTRA). 24.167 and also 23.221 describes these setting. I think the
AT commands for these in 27.007 are AT+CEMODE and +VCMOD
A UE indicates its CSFB capability in attach and location/routing area
updates. The network in turn also indicates whether these are supported
23.272 section 6.2 details a CSFB for MO call, where PS handover is
supported. 6.3 where PS handover is not supported and 6.5 where how to
return to E-UTRA when PS is suspended.
So everyone keeps talking of suspensions. However, I still see no CGEV
that supports this event. It still looks like a 2G holdover that is
being implemented by vendor specific extensions. Or is this just an
oversight on 3GPP's part and suspensions can happen in LTE as well?
My understanding is that the context behaves the same way as in
where it can be suspended, deactivated or handed over while doing CSFB
and the attach status will not change because when you are doing CSFB
you have done a combined attach (EPS/IMSI).
Attach status fair enough. However, does the reported technology change
as well? There are important implications here, e.g. being able to
deactivate the last context, etc.
Overall I think we need detailed traces for all such scenarios and
consider all possibilities. Currently I'm not convinced sharing LTE and
GPRS logic is the right way to go.
>>> Perhaps, but again we have no control of the attach
procedure with LTE.
>>> So the implementation has to rely on vendor specific radio settings.
>>> Same arguments about shoehorning logic apply here.
>> I'm a bit puzzled by this statement. It is not specific to LTE, but
>> related to +CFUN proprietary implementation against +COPS or +CGATT
>> usage, isn't it?
> The current GPRS logic is controlled with the equivalent of CGATT. This
> is a well-defined command by 3GPP, but it is not applicable to EPS
> domain. It is applicable only to PS domain, correct?
27.007 release 10, section 10, lists all commands applicable to EPS and
CGATT is one of them.
My fault, I mis-interpreted that section. You're of course correct that
CGATT is indeed applicable.