The present document studies the core network and NAS impacts in UE of extending DRX cycle for both idle mode and connected mode, solutions in the core network to support it, and interactions between GERAN/RAN and Core Network. Also, basic assumptions may be done for each solution on GERAN/RAN aspects of extending DRX cycle. The main goal is to identify which open issues remained from the Rel 12 study for extended Idle and Connected mode DRX as described in TR 23.887 (as documented in clause 7.1.3.1 and 7.1.3.6 of TR 23.887), document potential solutions and conclude on which feasible solutions would be adopted in core network (pending work in RAN regarding extension of DRX cycle). No connected mode mobility enhancements for extended C-DRX are considered in this work, i.e., if a UE using extended C-DRX moves to a different cell, current connected mode mobility procedures apply.

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