LTE - end-to-end UE initial attach [Under LTE]
» E-UTRA and E-UTRAN overall description - 36.300, Rel 8 «
» E-UTRAN access - 23.401, Rel 8 «
» EMM and ESM - 24.301, Rel 8 «
» GTPv2-C - 29.274, Rel 8 «
» S1AP - 36.413, Rel 8 «
» NAS overall - 24.007/8, Rel 8 «
» RRC - 36.331, Rel 8 «
» Numbering - 23.003, Rel 8 «
» SAE Security architecture - 33.401, Rel 8 «
» 3G Security - 33.102, Rel 8 «
» USIM Application - 31.102, Rel 8 «
In SAE/EPS article, we looked at LTE network architecture; in this article, we will look at end-to-end initial UE attach signaling.
What is different with LTE UE initial attach ? In LTE, initial attach is combined with (default) PDN (IP) connectivity. You can call this default PDN (IP) connectivity as default (or basic or initial) PDP context activation. This default connectivity is always of non-guaranted bit rate type (basically something which handles mostly bursty internet traffic). This default connectivity is called "default bearer". LTE no more use NAS terminology of "PDP Context" for "Sessions". By the way, LTE NAS consists only of Mobility Management (EMM) and Session Management (ESM). Additional PDP Contexts or Sessions (with different QoSs than default bearers) are called "dedicated bearers". Yes, it is misleading to call it "dedicated" !
Just like "Secondary PDP Context" in GPRS/UMTS, dedicated bearer has same PDN (IP) address as default bearer and specific QoS. Yes, TFT (Traffic Flow Template) is utilised here (UE and PGW) too ! QoS is defined differently in LTE (check out 3GPP TS 36.300 section 13 and 23.401, section 4.7.3).
Below is a end-to-end signaling diagram for UE initial attach. I have included lot of specification references to dig in further.
In next article, we will look at end-to-end signaling for dedicated bearer setup.
References: 3G Evolution: HSPA and LTE by Dahlman, Parkvall, Sköld, and Beming, LTE - From Theory to Practice, Edited by Sesia, Toufik, and Baker, and SAE and the Evolved Packet Core: Driving the Mobile Broadband Revolution by Olsson, Sultana, Rommer, Frid, and Mulligan.
|Copyright © Samir Amberkar 2010-11||§|
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