When a downlink IMMEDIATE ASSIGNMENT message is sent through the PCH,
an IMSI is always required in order to be able to calculate the paging
group. However, when the downlink IMMEDIATE ASSIGNMENT has to be sent
before the MS has completed the GMM ATTACH REQUEST, the IMSI is still
unknown. In this case we may assume that the MS is still in non-DRX
mode, which means it listens on all CCCH blocks (PCH and AGCH).
This means we may send the IMMEDIATE ASSIGNMENT through the AGCH in this
situation. This will also have the advantage that the scheduling through
the AGCH will have less latency than the paging queue.
Unfortunately the SAPI PCU_IF_SAPI_AGCH only supports sending whole MAC
blocks, so it won't be possible to attach a TLLI that can be used for
confirmation. To fix this, let's add a new SAPI_PCUI_IF_AGCH_2, that
works similar as SAPI PCU_IF_SAPI_PCH_2 and use it to send the
IMMEDIATE ASSIGNMENT through the AGCH.
CAUTION: This patch breaks compatibility with current master osmo-bts
and osmo-bsc (see "Depends")
Related: OS#5927
Depends: osmo-bts.git I29858fa20ad8bd0aefe81a5c40ad77a2559a8c10
Change-Id: I9effdcec1da91a6e2e7a7c41f95d3300ad1bb292
Philipp Maier
06b50c57a1