The Quality Packet Radio Service enhances the slow General Packet Radio Service
medium access procedure to include fast in-session access capability. In order
to maximize spectral efficiency, all services in Quality Packet Radio Service are
assigned uplink radio channel resources only when they have active data to send.
A new set of common control channels is designed to provide these in-session network
access capabilities. These channels support similar access and control functions
as the General Packet Radio Service common control channels (such as Packet Random
Access Channel, Packet Access Grant Channel) except they are used solely in Quality
Packet Radio Service to implement in-session access. These common control channels
are structured to meet the stringent low delay requirements for in-session access
and are termed fast packet common control channels. Since initial radio channel
access to the mobile subscriber station has already been established, a smaller
amount of overhead information is required for implementing in-session access,
thereby allowing these stringent low delay requirements to be met. Specifically,
for those services allowed to use in-session access, the assigned uplink channel
resources are released during an in-session inactive data period by releasing its
assigned Uplink State Flag(s) and Packet Data Traffic Channel(s).
