PCU_Tests_RAW.ttcn: introduce TC_ta_rach_imm_ass to test initial TA

The aim of this test case is to test the correctness of Timing Advance
at the time of TBF establishment. In particular, the test case sends
several Access Bursts (RACH.ind) with increasing 'qta' value, what
causes OsmoPCU to allocate a TBF (Temporary Block Flow) for each
RACH.ind and send DATA.req with Immediate Assignment on AGCH,
containing the expected Timing Advance value.

Change-Id: I21f76ae723519c0eb54515922a05ca8045b00ade
Related: SYS#4606
1 file changed