LTE Protocols & Specifications

8/22/2019 LTE Protocols & Specifications

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LTE Protocols&

Specifications


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Introduction In LTE architecture, core network includes Mobility Management Entity (MME), Serving

Gateway (SGW), Packet Data Network Gateway (PDN GW) where as E-UTRAN has E-

UTRAN NodeB (eNB). With increased data rates, improved spectrum efficiency and

packet-optimized system, LTE technology is set to drive machine to machine technology

and data intensive applications.

The figures shown below provide mapping of protocols to

corresponding specifications. To find 3GPP LTE specification, click at the correspondingprotocol in the images below.

Protocol structure of control plane in between UE & MME is shown below.

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This figure below shows protocol structure in between UE & P-GW user plane. GPRS

Tunnelling Protocol for the user plane (GTP-U) tunnels user data between eNodeB and

the S-GW as well as between the S-GW and the P-GW in the backbone network.

The X2 interface is defined between two

neighbour eNBs.

This figure shows the control & user

plane protocol stack of the X2 interface.

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Non-Access-Stratum (NAS) Protocol

The non-access stratum (NAS) is highest stratum of the control plane between UE and

MME at the radio interface. Main functions of the protocols that are part of the NAS arethe support of mobility of the user equipment (UE) and the support of session

management procedures to establish and maintain IP connectivity between the UE and

a packet data network gateway (PDN GW).

NAS control protocol performs followings:

EPS bearer management;

Authentication;

ECM-IDLE mobility handling;

Paging origination in ECM-IDLE;

Security control.

Protocol specification

3GPP TS 24.301 - Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS);

Stage 3

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Radio Resource Control (RRC)

protocol layer exists in UE & eNodeb, It is part of LTE air interface control plane. The

main services and functions of the RRC sublayer include: Broadcast of System Information related to the non-access stratum (NAS);

Broadcast of System Information related to the access stratum (AS);

Paging;

Establishment, maintenance and release of an RRC connection between the UE and E-

UTRAN Security functions including key management;

Establishment, configuration, maintenance and release of point to point Radio Bearers;

Mobility functions

QoS management functions;

UE measurement reporting and control of the reporting;

NAS direct message transfer to/from NAS from/to UE.


3GPP TS 36.331 - Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource

Control (RRC)

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Packet Data Convergence Protocol (PDCP)

PDCP protocol layer exists in UE & eNodeb, It is part of LTE air interface control and userplanes.

The main services and functions of the PDCP sublayer for the user plane include:

Header compression and decompression: ROHC only;

Transfer of user data;

In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLCAM;

Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM; Retransmission of PDCP SDUs at handover for RLC AM;

Ciphering and deciphering;

Timer-based SDU discard in uplink.

The main services and functions of the PDCP for the control plane include:

Ciphering and Integrity Protection; Transfer of control plane data.


3GPP TS 36.323 - Evolved Universal Terrestrial Radio Access (E-UTRA); Packet DataConvergence Protocol (PDCP) specification

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Radio Link Control (RLC)

RLC protocol layer exists in UE & eNodeb, It is part of LTE air interface control and user

planes. The main services and functions of the RLC sublayer include:

Transfer of upper layer PDUs;

Error Correction through ARQ (only for AM data transfer);

Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data

transfer); Re-segmentation of RLC data PDUs (only for AM data transfer);

In sequence delivery of upper layer PDUs (only for UM and AM data transfer);

Duplicate detection (only for UM and AM data transfer);

Protocol error detection and recovery;

RLC SDU discard (only for UM and AM data transfer);

RLC re-establishment.


3GPP TS 36.322 - Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Link Control

(RLC) protocol specification

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Medium Access Control (MAC)

MAC protocol layer exists in UE & eNodeb, It is part of LTE air interface control and user

planes.The main services and functions of the MAC sublayer include:

Mapping between logical channels and transport channels;

Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels

into/from transport blocks (TB) delivered to/from the physical layer on transport

channels;

scheduling information reporting;

Error correction through HARQ;

Priority handling between logical channels of one UE;

Priority handling between UEs by means of dynamic scheduling;

Transport format selection; Padding.


3GPP TS 36.321 - Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access

Control (MAC) protocol specification

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Air Interface Physical LayerThe LTE air interface physical layer offers data transport services to higher layers. The access to these services is

through the use of a transport channel via the MAC sub-layer. The physical layer is expected to perform thefollowing functions in order to provide the data transport service:

Error detection on the transport channel and indication to higher layers FEC encoding/decoding of the transport channel

Hybrid ARQ soft-combining

Rate matching of the coded transport channel to physical channels

Mapping of the coded transport channel onto physical channels

Power weighting of physical channels

Modulation and demodulation of physical channels Frequency and time synchronisation

Radio characteristics measurements and indication to higher layers

Multiple Input Multiple Output (MIMO) antenna processing

Transmit Diversity (TX diversity)

Beam forming

RF processing


3GPP TS 36.201 - Evolved Universal Terrestrial Radio Access (E-UTRA); LTE physical layer; General description

3GPP TS 36.211 - Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation

3GPP TS 36.212 - Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing and channel coding

3GPP TS 36.213 - Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures

3GPP TS 36.214 - Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer; Measurements

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http://www.3gpp.org/ftp/Specs/html-info/36201.htmhttp://www.3gpp.org/ftp/Specs/html-info/36211.htmhttp://www.3gpp.org/ftp/Specs/html-info/36212.htmhttp://www.3gpp.org/ftp/Specs/html-info/36213.htmhttp://www.3gpp.org/ftp/Specs/html-info/36214.htmhttp://www.3gpp.org/ftp/Specs/html-info/36214.htmhttp://www.3gpp.org/ftp/Specs/html-info/36213.htmhttp://www.3gpp.org/ftp/Specs/html-info/36212.htmhttp://www.3gpp.org/ftp/Specs/html-info/36211.htmhttp://www.3gpp.org/ftp/Specs/html-info/36201.htm


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S1 Signalling Transport

S1 signalling bearer provides the following functions:

Provision of reliable transfer of S1-AP message over S1-MME interface.

Provision of networking and routeing function

Provision of redundancy in the signalling network

Support for flow control and congestion control

L2 - Data link layer

Support of any suitable data link layer protocol, e.g. PPP, Ethernet

IP layer

The eNB and MME support IPv6 and/or IPv4

The IP layer of S1-MME only supports point-to-point transmission for delivering S1-AP message.

The eNB and MME support the Diffserv Code Point marking

Transport layer

SCTP is supported as the transport layer of S1-MME signalling bearer.

SCTP refers to the Stream Control Transmission Protocol developed by the Sigtran working group of

the IETF for the purpose of transporting various signalling protocols over IP network.

There is only one SCTP association established between one MME and eNB pair.

The eNB establishes the SCTP association. The SCTP Destination Port number value assigned by IANA

to be used for S1AP is 36412.

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S1 Signalling Transport


3GPP TS 36.410 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1 general

aspects and principles

3GPP TS 36.411 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1

3GPP TS 36.412 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 signalling

transport

IETF RFC 2460: "Internet Protocol, Version 6 (IPv6) Specification"

IETF RFC 791 (September,1981): "Internet Protocol"

IETF RFC 2474 (December 1998): "Definition of the Differentiated Services Field (DS Field) in the IPv4and IPv6 Headers

S1 layer 1

The main functions of S1 interface layer 1 are as following:

Interface to physical medium;

Frame delineation;

Line clock extraction capability;

Layer 1 alarms extraction and generation;

Transmission quality control.


3GPP TS 36.411 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1 11Telcomz
http://www.3gpp.org/ftp/Specs/html-info/36410.htmhttp://www.3gpp.org/ftp/Specs/html-info/36411.htmhttp://www.3gpp.org/ftp/Specs/html-info/36412.htmhttp://www.ietf.org/rfc/rfc2460.txthttp://www.ietf.org/rfc/rfc791.txthttp://www.ietf.org/rfc/rfc2474.txthttp://www.3gpp.org/ftp/Specs/html-info/36411.htmhttp://www.3gpp.org/ftp/Specs/html-info/36411.htmhttp://www.ietf.org/rfc/rfc2474.txthttp://www.ietf.org/rfc/rfc791.txthttp://www.ietf.org/rfc/rfc2460.txthttp://www.3gpp.org/ftp/Specs/html-info/36412.htmhttp://www.3gpp.org/ftp/Specs/html-info/36411.htmhttp://www.3gpp.org/ftp/Specs/html-info/36410.htm


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S1 Application Protocol (S1AP)

S1AP provides the signalling service between E-UTRAN and the evolved packet core (EPC)and has following functions:

E-RAB management function

Initial Context Transfer function

UE Capability Info Indication function

Mobility Functions

S1 interface management functions

NAS Signalling transport function

S1 UE context Release function

UE Context Modification function

Status Transfer

Trace function

Location Reporting

S1 CDMA2000 Tunneling function

Warning message transmission function

RAN Information Management (RIM) function

Configuration Transfer function


3GPP TS 36.413 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1

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GTP-U Transport

The transport layer for data streams over S1, X2, S4, S5 and S8 is an IP based Transport. TheGTP-U protocol over UDP over IP is supported as the transport for data streams on the userdata interfaces.

Any data link protocol that fulfils the requirements toward the upper layer may be used.

UDP/IP The UDP port number for GTP-U is as defined in 3GPP TS 29.281.

The eNB and the EPC support fragmentation and assembly of GTP packets at the IP layer.

The eNB and the EPC support IPv6 and/or IPv4.


3GPP TS 36.410 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1

general aspects and principles 3GPP TS 36.411 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 layer 1

3GPP TS 36.414 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 datatransport

3GPP TS 36.420 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 generalaspects and principles

3GPP TS 36.421 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 layer 1

3GPP TS 36.424 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 datatransport

IETF RFC 2460: "Internet Protocol, Version 6 (IPv6) Specification"

IETF RFC 791 (September,1981): "Internet Protocol"

IETF RFC 2474 (December 1998): "Definition of the Differentiated Services Field (DS Field) in the

IPv4 and IPv6 Headers 13Telcomz
http://www.3gpp.org/ftp/Specs/html-info/36410.htmhttp://www.3gpp.org/ftp/Specs/html-info/36411.htmhttp://www.3gpp.org/ftp/Specs/html-info/36414.htmhttp://www.3gpp.org/ftp/Specs/html-info/36420.htmhttp://www.3gpp.org/ftp/Specs/html-info/36421.htmhttp://www.3gpp.org/ftp/Specs/html-info/36424.htmhttp://www.ietf.org/rfc/rfc2460.txthttp://www.ietf.org/rfc/rfc791.txthttp://www.ietf.org/rfc/rfc2474.txthttp://www.ietf.org/rfc/rfc2474.txthttp://www.ietf.org/rfc/rfc791.txthttp://www.ietf.org/rfc/rfc2460.txthttp://www.3gpp.org/ftp/Specs/html-info/36424.htmhttp://www.3gpp.org/ftp/Specs/html-info/36421.htmhttp://www.3gpp.org/ftp/Specs/html-info/36420.htmhttp://www.3gpp.org/ftp/Specs/html-info/36414.htmhttp://www.3gpp.org/ftp/Specs/html-info/36411.htmhttp://www.3gpp.org/ftp/Specs/html-info/36410.htm


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GPRS Tunnelling Protocol User Plane (GTP-U)

GTP-U protocol is used over S1-U, X2, S4, S5 and S8 interfaces of the Evolved Packet

System (EPS). GTP-U Tunnels are used to carry encapsulated T-PDUs and signalling

messages between a given pair of GTP-U Tunnel Endpoints. The Tunnel Endpoint ID (TEID)which is present in the GTP header indicates which tunnel a particular T-PDU belongs to.

The transport bearer is identified by the GTP-U TEID and the IP address (source TEID,

destination TEID, source IP address, destination IP address).


3GPP TS 29.281 - General Packet Radio System (GPRS) Tunnelling Protocol User Plane

(GTPv1-U)

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X2 Application Protocol (X2AP)

The X2AP protocol is used to handle the UE mobility within E-UTRAN and provides the

following functions:

Mobility Management Load Management

Reporting of General Error Situations

Resetting the X2

Setting up the X2

eNB Configuration UpdateProtocol specification

3GPP TS 36.423 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2

Application Protocol (X2AP)

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--Thank You--

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