You can use the location update timestamp in the HLR. The MS will RACH periodically based on the value of the T3212 timer. This is configurable to multiples of 6 minutes with 6 being the minimum. If a phone hasn't updates it's location after that interval has passed you can assume it's not connected

-------- Original Message --------
From: robert <robert.steve07@gmail.com>
Date: Wed, Jun 21, 2017, 12:32 PM
To: Neels Hofmeyr <nhofmeyr@sysmocom.de>
CC: OpenBSC Mailing List <openbsc@lists.osmocom.org>
Subject: Re: knowing connected subscribers


On Jun 21, 2017, at 1:44 AM, Neels Hofmeyr <nhofmeyr@sysmocom.de> wrote:

> On Tue, Jun 20, 2017 at 02:11:25PM +0300, robert wrote:
>> Hello,
>>
>> Is there a way in openBSC to know if a certain phone that previously connected to my BTS is still connected at a given time ?
>
> In OpenBSC not really, the subscription status is typically in the MSC and/or
> HLR; so if you're using OsmoNITB you can query the subscriber's LAC on the VTY,
> or use the CTRL command 'subscriber-list-active-v1’.

I am using OsmoNITB. Does the command ’subscriber-list-active-v1’ list the phones that are currently connected or should they be active (for example during a call) ?
>
> If you're using OpenBSC alone, there's no way AFAIK. It only sees a subscriber
> when it is actually actively sending/receiving right at this moment.
>
> ~N
>