The same allocation procedure is used in Avid Immediate Assignment as in the normal Immediate Assignment.
RMSCS requests the block RMCC (RCS Mobile Connection Coordinator) to seize an MS individual and to link it towards the RMSCS individual. RMCC sends information about the seized MS individual to RMHAIDL and RMHAIUL (RCS Mobile Handling of A-Interface Uplink) which initiates the corresponding individual, and returns to RMSCS. RMSCS sends information about the seized MS individual to RMHBI.
RMSCS instructs RMHBI to activate the appropriate channel for signalling. If the channel is not ordered blocked according to RNLCT, RMHBI informs the BTS with the 3GPP TS 08.58 CHANNEL ACTIVATION message via RCLCCH and RHLAPD. At the same time the timer T3101 is started.
The BSC then sends the 3GPP TS 04.18 IMMEDIATE ASSIGNMENT message to the MS via RMHBI, RCLCCH, RHLAPD and the BTS without waiting for the 3GPP TS 08.58 CHANNEL ACTIVATION ACKNOWLEDGE message. The MS is instructed to switch to the allocated signalling channel.
If no fault has been received and the timer T3101 has not expired when 3GPP TS 08.58 CHANNEL ACTIVATION ACKNOWLEDGE message is received in RMSCS, the timer T3101 is stopped and a 3GPP TS 08.58 ESTABLISH INDICATION message is sent from the BTS to RMHBI via RHLAPD and RCLCCH. RMHBI checks the message and sends it on to RMSCS.
RMSCS orders RMHBI to change link from RMSCS to RMCC.