Telecom Tutorials by Samir Amberkar

LTE - UE States (Attach) [Under LTE]
» E-UTRA and E-UTRAN overall description - 36.300, Rel 8 «
» E-UTRAN access - 23.401, Rel 8 «
» NAS - 24.301, Rel 8 «
» RRC - 36.331, Rel 8 «

In next few articles, we will look at UE state at various stages from NAS/AS point of view. We will consider initial attach, tracking area update, service request, and detach scenarios.

Overall NAS/AS states reference: 23.401:4.6, 24.301:5.1.3, 36.300:A.2, 36.331:4.2.1

Radio Access steps	Bearer contexts inactive EMM_NULL RRC_NULL	RF scanning, Cell search
	EMM_DEREGISTERED (PLMN SEARCH) RRC_IDLE
Radio Access steps	+COPS=0;+CGATT=1	PLMN, Cell selected, DL synch UL synch/Random access RRC Connection request →
	EMM_REGISTERED_INITIATED RRC_IDLE
		RRC Connection Setup ← RRC Connection Setup complete → [Attach Request/PDN Connectivity request]
	EMM_REGISTERED_INITIATED RRC_CONNECTED
		Authentication request ← Authentication response → NAS Security mode command ← NAS Security mode complete →
	EMM_REGISTERED_INITIATED RRC_CONNECTED
		AS Security mode command ← RRC Connection Reconfiguration ← [Attach Accept/Activate Default Bearer request] AS Security mode complete → RRC Connection Reconfiguration complete →
	EMM_REGISTERED_INITIATED RRC_CONNECTED (DRBs established)
	Bearer contexts active EMM_REGISTERED (NORMAL SERVICE) RRC_CONNECTED	Attach Complete/Activate Default Bearer Accept →

Specifications use couple of more variables, EMM mode and ECM state, both of these are same as RRC state (in case of UE). That is EMM_IDLE/ECM_IDLE ⇒ RRC_IDLE and EMM_CONNECTED/ECM_CONNECTED ⇒ RRC_CONNECTED.

Copyright © Samir Amberkar 2010-12

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