I create this ticket to document process of adding some sample test validating EGPRS against osmo-pcu.
Probably the easiest would be to start and create a TC_mo_mt_ping_egprs().
When the mobile station has received the PACKET UPLINK ASSIGNMENT message it shall respond with a PACKET RESOURCE REQUEST message in the first allocated radio block.
A mobile station supporting EGPRS shall indicate the EGPRS capability in the MS Radio Access Capability 2 IE of the PACKET RESOURCE REQUEST message.
https://issuu.com/leliwa/docs/signalling_in_gprs_egprs_chapter_03/30 page 44-45/68.
That's two-phase access to get EGPRS TBF:
* MS sends RACH on CCCH asking for UL TBF
* Network sends IMM ASS on AGCH/PCH providing PDCH + TLLI + TFI
* MS sends PACKET RESOURCE REQUEST on PDCH assigned with "MS Radio Access Capability 2" IE stating it supports EGPRS
* The network should send an PACKET UPLINK ASSIGNMENT with updated CS
* MS answers with PACKET CONTROL ACK
* MS can now send whatever data.
TS 44.06 sec Table 22.214.171.124: PACKET RESOURCE REQUEST information elements