Wireless Oom

In connected mode, the GTP-U can be established between GGSN and AN (without SGSN), which is more efficient.

PDP context
is
for PS service.
It consists of
1. RAB
2. CN bearer (bearer between SGSN and GGSN)
The PDP context is created with a defined QoS that is requested by the UE and granted by the network.

RAB (Radio Access Bearer)
is
created to provide user plane data transfer.
RAB comprises
1. RB and
2. connection from the SRNC to the SGSN (Iu bearer).
The RAB is created on reequest from the SGSN with a specific QoS request.
For a given UE, there can be multiple RABs per NAS service (speech or PS data service).