LTE - Signaling stacks UE[Under LTE]
» E-UTRA and E-UTRAN overall description - 36.300, Rel 8 «
» E-UTRAN access - 23.401, Rel 8 «
In following articles, we would look at end-to-end protocols
involved in control and user paths. We will start with signaling
stacks at UE. Below digram show the signaling stacks at various
nodes.
|
AT interface
|
|
Adaptor
|
|
ESM
|
|
EMM
|
|
RRC
|
|
PDCP
|
|
RLC
|
|
MAC
|
|
PHY
|
|
|
|
RRM/Relay
|
|
RRC
|
S1AP
|
|
PDCP
|
SCTP
|
|
RLC
|
IP
|
|
MAC
|
L2
|
|
PHY
|
L1
|
|
|
|
MME AL
|
|
ESM
|
GTP-C
|
|
EMM
|
|
S1AP
|
|
SCTP
|
UDP
|
|
IP
|
IP
|
|
L2
|
L2
|
|
L1
|
L1
|
|
|
|
SGW AL
|
|
GTP-C
|
|
UDP
|
|
IP
|
|
L2
|
|
L1
|
|
Towards PGW
|
| UE |
SRBs
(RRC SRB0/1/2,
MAC LCID 0/1/2)
|
eNB |
S1
(S1AP ID)
|
MME |
GTP-C
(IMSI,
EPS bearer ID)
|
SGW |
LTE does not support circuit switched connections; it supports
only packet switched connections or "bearers". Bearer capabilities
are expressed in terms of QoS. Bearer management
(setup/modify/release) functions are handled by ESM layer (located
in UE and MME). We will cover more details on end-to-end data
path/bearers, QoS etc. in later articles.
Below diagram shows the signaling entities at UE, one possible
view of their internals, and their important functions.
|
.. |
27.007, Few related commands
| +CFUN |
Activate (limited or full) |
| +COPS |
PLMN selection |
| +CGATT |
PS attach |
| +CGDCONT |
Define PDN connection |
| +CGDSCONT |
Define bearer resource |
| +CGACT |
Deactivate/Activate bearer resource |
|
Adaptor
|
ESM
|
|
EMM
|
|
Access stratum
|
|
Data plane management
|
|
|
|
|
.. |
Implementation specific, usually functionality wise modules (e.g. EMM-Adaptor module to talk to NAS EMM module for EMM specific commands & indications), framework for data plane management, adopter may also be in charge of talking to MMI, additional drivers like bluetooth, COM port, USB etc. |
|
ESM
|
Bearer context1
|
|
.. |
Bearer context2
|
|
. . . |
Bearer context11
|
|
|
|
|
|
.. |
24.301, EPS bearer context management |
|
.. |
24.301, mobility management like attach/detach, tracking area update, authentication, providing NAS signaling connection, NAS ciphering and integrity protection |
RRC
|
RRC state machine
|
|
|
|
SRB0
|
SRB1
|
SRB2
|
|
|
|
|
|
.. |
36.331, signaling connection management/configuration, data radio bearer configuration, measurement reporting, configuring AS ciphering and integrity protection, handling broadcast system info, paging, handover |
PDCP
|
Control
|
|
|
SRB1
|
|
|
SRB2
|
|
|
DRB1
|
|
. . |
DRB11*
|
|
|
|
|
|
|
.. |
36.323, integrity protection, ciphering |
RLC
|
Control
|
|
|
SRB0
|
|
|
SRB1
|
|
|
SRB2
|
|
|
DRB1
|
|
. . |
DRB11*
|
|
|
|
|
|
.. |
36.322, buffering, segmentation, concatenation, reassembly, ARQ |
|
.. |
36.321, channel mapping, multiplexing, channel prioritisation, HARQ |
|
.. |
36.201 modulation, coding, power control, cell search, measurements, CRC insertion and other phy specific procedures |
* as per RRC TS 36.331, sec 6.4, maxDRB is 11; but as per MAC TS 36.321, section 6.2.1, 11 LCIDs are possible, three of which goes for SRB 0-2, leaving maximum 8 for DRBs !
In next article, we will look at eNB from same angle.
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 | § |
