osmo-msc: repeatpaging?

Neels Hofmeyr nhofmeyr at sysmocom.de
Sun Nov 3 23:03:22 UTC 2019


I noticed the MSC test that wants osmo-msc to repeat a Paging to the BSC and
hNodeB.

After fixing the Iu tests, I wanted to get this last ttcn3-msc-test working, so
I was about to implement repeated Paging from osmo-msc, but the more I think
about it, the less it makes sense to me.

The commit log in osmo-ttcn3-hacks says:

  Repeating will improve the reachability of MS when a Paging is lost
  or not received because the MS is moving between states.

This reasoning seems flawed to me, because the BSC / hNodeB is between the MSC
and the MS, and the BSC *does* repeat Paging. That should cover MS moving
between states.

The link between MSC and {BSC,hNodeB} is considered reliable, and AFAICT
nothing really gets better when repeating a Paging request to the BSS.

It could make sense to maybe repeat Paging with a larger/more general Cell
Identifier List? But why not send the full list in the first place?

Also 3GPP TS 48.008 3.1.10 Paging says:

  A single PAGING message across the MSC to BSS interface contains information
  on the cells in which the page shall be broadcast.

I interpret the "A single" as: there is no repetition of Paging requests toward
the BSS, and that's also what makes most sense to me infrastructurally.
Is there any spec indicating repeated Paging from the MSC?

I would actually remove the test TC_lu_and_mt_sms_paging_repeated.
If that's the wrong call, we should specify how osmo-msc should repeat Paging.
Before that, having the test makes little sense...

What do you guys think?

~N
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