Signalling Flow PS Call Establishment

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Signalling Flow PS Call Establishment

•This slide set provides a detailed illustration of the message flow observed for an PS call
•The message flow is focused upon communication with the packet switched core and does not include communication with the circuit switched core.
•The UE starts by searching for candidate cells by correlating the RSSI with the code defining the primary SCH
•The UE then achieves radio frame synchronisation and reads the BCCH logical channel
•The BCCH provides system information including the cell selection criteria
•If the cell passes the cell selection criteria then the UE establishes an RRC connection and registers with the core network
•Having registered the UE activates the PDP context with the CN using the existing CN (assumption is that follow on request pending is set)
•In case of no activity (no data nor signalling data transmitted between the UE and CN) the dedicated channel between the UE and the RNC is released and UE is moved to Cell_FACH or Cell_PCH cell state