LTE Technical L2 1105 3GPP

8/4/2019 LTE Technical L2 1105 3GPP

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THE Mobile Broadband Standard

3GPP 2011 3GPP Workshop, Bangalore, 30 May 2011 1

Radio Access Network

Architecture and Protocols

Benoist SbireNokia Siemens Networks

3GPP TSG-RAN WG2


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3GPP 2011 3GPP Workshop, Bangalore, 30 May 2011

Contents

E-UTRAN Overview

Architecture, Functions

Protocol Architecture

User Plane, Control Plane

Some Highlights

QoS, Reliability, Mobility, Latency

Rel-10

Overview, Carrier Aggregation, Minimisation of Drive Tests

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E-UTRAN Architecture and Functions

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E-UTRAN Architecture

E-UTRAN consists of eNBs

flat architecture (no RNC or BSC as in UTRAN and

GERAN) for reduced latency and delays

eNBs are interconnected with each other by

means of the X2 interface can be a logical connection via CN elements

eNBs are also connected to the Evolved

Packet Core (EPC)

eNBs are connected to the Mobility Management

Entity (MME) via the S1-MME interface eNBs are connected to the to the Serving Gateway

(S-GW) by means of the S1-U interface

4

eNB

MME / S-GW MME / S-GW

eNB

eNB

S1

S1

S

1 S1

X2

X2

X2

E-UTRAN


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E-UTRAN Functions

Main functions hosted by eNB include functions for Radio Resource Management: Radio Bearer

Control, Radio Admission Control, Connection Mobility

Control, Dynamic allocation of resources to UEs in both

uplink and downlink (scheduling)

IP header compression and encryption of user data

stream

Routing of User Plane data towards

Serving Gateway

Scheduling and transmission of paging

messages (originated from the MME);

Scheduling and transmission of

broadcast information (originatedfrom the MME or O&M)

5

internet

eNB

RB Control

Connection Mobility Cont.

eNB MeasurementConfiguration & Provision

Dynamic ResourceAllocation (Scheduler)

PDCP

PHY

MME

S-GW

S1

MAC

Inter Cell RRM

Radio Admission Control

RLC

E-UTRAN EPC

RRC

MobilityAnchoring

EPS Bearer Control

Idle State MobilityHandling

NAS Security

P-GW

UE IP addressallocation

Packet Filtering


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Protocol Architecture

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User Plane

PDCP (Packet Data Convergence Protocol) 36.323 ciphering

timer-based discard and header compression using the RoHC protocol

in-sequence delivery, retransmission and duplicate detection of PDCP SDUs at handover

RLC (Radio Link Control) 36.322

error correction through ARQ segmentation and concatenation of SDUs for the same radio bearer

in-sequence delivery

MAC (Media Access Control) 36.321

multiplexing/demultiplexing of RLC PDUs

scheduling information reporting error correction through HARQ

logical channel prioritisation

7

eNB

PHY

UE

PHY

MAC

RLC

MAC

PDCPPDCP

RLC
http://www.3gpp.org/ftp/Specs/html-info/36323.htmhttp://www.3gpp.org/ftp/Specs/html-info/36322.htmhttp://www.3gpp.org/ftp/Specs/html-info/36321.htmhttp://www.3gpp.org/ftp/Specs/html-info/36321.htmhttp://www.3gpp.org/ftp/Specs/html-info/36322.htmhttp://www.3gpp.org/ftp/Specs/html-info/36323.htm


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User Plane

8

Multiplexing

...

HARQ

Scheduling / Priority Handling

Transport Channels

MAC

RLC

PDCP

Segm.

ARQ etc

Segm.

ARQ etc

Logical Channels

ROHC ROHC

Radio Bearers

Security Security

UL-SCH


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User Plane

9

PDCP SDU

IP PayloadHeader

H

IP PDU#1

Radio Bearer 1

MAC SDU

CRCTransport Block

H

H H

RLC SDU

H

RLC PDU RLC PDU

Multiplexing

MAC SDU

PDCP

RLC

MAC

PHY

SN PDCP SDU

IP PayloadHeader

H

IP PDU#2

Radio Bearer 1

RLC SDU

SN

RLC SDU

PDCP SDU

IP PayloadHeader

H

IP PDU#2

Radio Bearer 2

SN


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Control Plane

RRC (Radio Resource Control) 36.331 Broadcast of system information, paging, RRC connection management, RB control,

mobility functions, UE measurement reporting and control

PDCP (Packet Data Convergence Protocol) 36.323

Ciphering and integrity protection

RLC (Radio Link Control) 36.322 Error Correction through ARQ, (re)-Segmentation according to the size of the TB,

concatenation of SDUs for the same radio bearer, in-sequence delivery

MAC (Media Access Control) 36.321

Multiplexing/demultiplexing of RLC PDUs,

error correction through HARQ,

Logical Channel Prioritisation

10

eNB

PHY

UE

PHY

MAC

RLC

MAC

MME

RLC

NAS NAS

RRC RRC

PDCP PDCP
http://www.3gpp.org/ftp/Specs/html-info/36331.htmhttp://www.3gpp.org/ftp/Specs/html-info/36323.htmhttp://www.3gpp.org/ftp/Specs/html-info/36322.htmhttp://www.3gpp.org/ftp/Specs/html-info/36321.htmhttp://www.3gpp.org/ftp/Specs/html-info/36321.htmhttp://www.3gpp.org/ftp/Specs/html-info/36322.htmhttp://www.3gpp.org/ftp/Specs/html-info/36323.htmhttp://www.3gpp.org/ftp/Specs/html-info/36331.htm


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Control Plane

Only two RRC states

idle and connected

Idle mode

UE known in EPC, has an IP address and its location known on Tracking Area level

UE-based cell-selection and tracking area update to EPC

MME initiates paging in the whole tracking areas indicated by the UE

Connected mode

UE known in E-UTRAN and its location known on Cell level

Mobility is UE-assisted, network-controlled

Discontinuous Data Reception (DRX) supported for power saving

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E-UTRAN Highlights

QoS

Reliability

MobilityLatency

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QoS

E-UTRAN is responsible for Radio Bearer management and therefore

ensuring QoS over the radio

one-to-one mapping between EPS bearer, E-RAB and Radio Bearer

13

P-GWS-GW PeerEntity

UE eNB

EPS Bearer

Radio Bearer S1 Bearer

End-to-end Service

External Bearer

Radio S5/S8

Internet

S1

E-UTRAN EPC

Gi

E-RAB S5/S8 Bearer


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QoS

RB establishment based on QoS parameters from MME QoS Class Identifier (QCI) per bearer : scalar value which identifies a particular

service in terms of resource type, priority, packet delay budget and packet errorrate [23.203]

Guaranteed Bit Rate (GBR) and Maximum Bit Rate (MBR) per bearer

Aggregate Maximum Bit Rate (AMBR) per group of bearers

RB Scheduling based on QoS parameters from MME and schedulinginformation from UE Channel Quality Indication

Buffer Status Report

Power Headroom Report

Scheduling for downlink is eNB implementation specific

Scheduling for uplink is only partially specified Logical channel prioritization and avoid starvation [36.321]

14
http://www.3gpp.org/ftp/Specs/html-info/23203.htmhttp://www.3gpp.org/ftp/Specs/html-info/36321.htmhttp://www.3gpp.org/ftp/Specs/html-info/36321.htmhttp://www.3gpp.org/ftp/Specs/html-info/23203.htm


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Reliability

L1 applies 24 bit CRC protection to transport blocks (MAC PDUs) erroneous transport blocks are discarded on L1

Hybrid ARQ (HARQ) protocol in MAC + ARQ protocol in RLC high reliability and radio efficiency

HARQ feedback sent on L1/L2 control channel

Single, un-coded bit (low overhead) Sent for each scheduled subframe (fast)

Retransmissions are soft-combined with previous attempt (efficient)

ARQ status report sent as MAC data RLC Status is sent on demand (poll, timer, gap detection)

protected by CRC and HARQ retransmissions

Both HARQ and ARQ protocols operate between the eNB and UE fast handling of residual HARQ errors

Ensures low latency and high reliability

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Mobility

Handover Principles

Lossless: packets are forwarded from the source to the target

Network-controlled : target cell is selected by the network, not by the UE and Handover

control in E-UTRAN (not in packet core)

UE-assisted : measurements are made and reported by the UE to the network Late path switch: only once the handover is successful, the packet core is involved

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Handover

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Source

eNBTarget

eNB

UE

X2

S-GW

MME

control plane

user plane

user data

S1-US1-MME

control plane signalling

measurements

Source eNB configures UEmeasurements target frequency and triggers

Source eNB receives UE

measurement reports

HO decision is made andtarget eNB is selected by thesource eNB


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HO request sent from sourceeNB to target eNB

Target eNB performsadmission control and accepts

the HO request

HO Ack sent to source eNBfrom target eNB

Handover

18

Source

eNBTarget

eNB

UE

S-GW

MME

control plane

user plane

user data

S1-US1-MME


measurements

HO request

HO Request Ack


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Handover

19

Source

eNBTarget

eNB

UE

X2

S-GW

MME

control plane

user plane

user data

S1-US1-MME


HO command

HO command is sent to the UE RRCConnectionReconfiguration

including the mobilityControlInfo

Data forwarding initiatedtowards the target eNB


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Handover

20

Source

eNBTarget

eNB

UE

X2

S-GW

MME

control plane

user plane

user data

S1-US1-MME


HO confirm

UE accesses the target eNBand confirms the HO RACH procedure is initiated

RRCConnectionReconfigurationComplete is sent


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Handover

21

Source

eNBTarget

eNB

UE

X2

S-GW

MME

control plane

user plane

user data


Target eNB requests EPC toswitch the data path eNB MME : path switch

request

MME S-GW : modify bearerrequest

S-GW MME : modify bearerresponse

MME eNB : path switchrequest ACK

Target eNB notifies the sourceeNB that UE resources can be

released


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Handover

22

Source

eNBTarget

eNBX2

S-GW

MME

control plane

user plane

user data

S1-US1-MME


Path is switched

Source eNB finishesforwarding packets once completed UE context can

be cleared and resources freed

HO is completed

UE


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Latency

User Plane Latency < 10ms [36.912]

one way latency

between 5ms and 10ms depending on HARQ operating point and TDD configuration

Control Plane Latency : 50ms

Transition time from Idle to Connected mode

Handover: 12ms interruption time

For intra - E-UTRAN handover

23
http://www.3gpp.org/ftp/Specs/html-info/36912.htmhttp://www.3gpp.org/ftp/Specs/html-info/36912.htm


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Rel-10

Overview

Carrier Aggregation

Minimisation of Drive Tests

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Rel-10

Main goal of Rel-10 was to fulfil the IMT-Advanced requirements up to 1Gbps in downlink and 500Mbps in uplink [36.913]

took 2 years of efforts in 3GPP

Main Rel-10 Features

Carrier Aggregation: to increase the bit rate and reach IMT-A requirements [WID]

eICIC: to efficiently support highly increasingly complex network deployment scenarioswith unbalanced transmit power nodes sharing the same frequency [WID]

Relay Nodes: to improve the coverage of high data rates, cell-edge throughput and ease

temporary network deployments [WID]

Minimisation of Drive Tests / SON Enhancements: enhanced and combined effort to

optimize the performance of the network aiming to automate the collection of UE

measurements and thus minimize the need for operators to rely on manual drive-tests[WID] [WID]

MBMS enhancements: to enable the network to know the reception status of UEs

receiving a given MBMS service in connected mode [WID]

Machine Type Communication: protect the core network from signalling congestion &

overload [WID]

25
http://www.3gpp.org/ftp/Specs/html-info/36913.htmhttp://www.3gpp.org/ftp/tsg_ran/tsg_ran/TSGR_48/Docs/RP-100661.ziphttp://www.3gpp.org/ftp/tsg_ran/tsg_ran/TSGR_47/Docs/RP-100383.ziphttp://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_50/Docs/RP-101417.ziphttp://www.3gpp.org/ftp/tsg_ran/tsg_ran/TSGR_47/Docs/RP-100360.ziphttp://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_49/docs/RP-101004.ziphttp://ftp.3gpp.org/tsg_ran/TSG_RAN/TSGR_50/Docs/RP-101244.ziphttp://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_49/docs/RP-101026.ziphttp://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_49/docs/RP-101026.ziphttp://ftp.3gpp.org/tsg_ran/TSG_RAN/TSGR_50/Docs/RP-101244.ziphttp://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_49/docs/RP-101004.ziphttp://www.3gpp.org/ftp/tsg_ran/tsg_ran/TSGR_47/Docs/RP-100360.ziphttp://www.3gpp.org/ftp/tsg_ran/TSG_RAN/TSGR_50/Docs/RP-101417.ziphttp://www.3gpp.org/ftp/tsg_ran/tsg_ran/TSGR_47/Docs/RP-100383.ziphttp://www.3gpp.org/ftp/tsg_ran/tsg_ran/TSGR_48/Docs/RP-100661.ziphttp://www.3gpp.org/ftp/Specs/html-info/36913.htm


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Carrier Aggregation

Goal of Carrier aggregation is to aggregate Rel-8 compatible carriers toincrease peak data rate

up to 5 carriers can be aggregated in DL for a maximum BW of 100 MHz

non-contiguous carriers can also be aggregated in DL for increased flexibility

26

LTE-Advanced maximum bandwidth

Carrier 1 Carrier 4 Carrier 5Carrier 3Carrier 2

Rel8 BW Rel8 BW Rel8 BW Rel8 BW Rel8 BW


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Carrier Aggregation

Impact on L2 Architecture

27

HARQ HARQ

DL-SCH

on CC1

...

Segm.

ARQ etc

Multiplexing UE1 Multiplexing UEn

BCCH PCCH

Unicast Scheduling / Priority Handling

Logical Channels

MAC

Radio Bearers

Security Security...

CCCH

MCCH

Multiplexing

MTCH

MBMS Scheduling

PCH BCH MCH

RLC

PDCP

ROHC ROHC...

Segm.

ARQ etc...

Transport Channels

Segm.

ARQ etc

Security Security...

ROHC ROHC...

Segm.

ARQ etc...

Segm. Segm.

...

...

...

DL-SCH

on CCx

HARQ HARQ

DL-SCH

on CC1

...

There is one PDCP and RLC per

Radio Bearer. Not visible from RLC

on how many CCs the PHY layer

transmission is conducted.

Dynamic L2 packet scheduling

across multiple CCs supported

Independent HARQ per CC. HARQretransmissions shall be sent on the

same CC as the CC of the original

transmission

Separate TrCH per CC


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Carrier Aggregation

Basic Concept when CA is configured, the UE only has one RRC connection with the network

at RRC connection establishment/re-establishment/handover, one serving cell provides

the NAS mobility information (e.g. TAI), and at RRC connection re-

establishment/handover, one serving cell provides the security input

this cell is referred to as the Primary Cell (PCell)

in the downlink, the carrier corresponding to the PCell is the Downlink Primary

Component Carrier (DL PCC) while in the uplink it is the Uplink Primary Component Carrier

(UL PCC)

depending on UE capabilities, Secondary Cells (SCells) can be configured to form together

with the PCell a set of serving cells

in the downlink, the carrier corresponding to an SCell is a Downlink Secondary Component

Carrier (DL SCC) while in the uplink it is an Uplink Secondary Component Carrier (UL SCC)

the configured set of serving cells for a UE therefore always consists of one PCell and one

or more SCells

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Carrier Aggregation

Example

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PCell

SCell

SCell

serving cells

intra-frequency neighbour

inter-frequency neighbour

PCC

SCC

SCC


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Goal of Minimisation of Drive Tests

replace manual drive testing that the operators have to perform currently

automatic UE measurements and data logging in drive-tests scenarios

provide a basis for finding coverage problems in the HSPA & LTE network

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Measurement Configuration [32.422, 37.320]

measurements are configured to the UE by E-UTRAN/UTRAN by RRC signalling, based on

Network Management systems measurement definitions configured to (E-)UTRAN

31
http://www.3gpp.org/ftp/Specs/html-info/32422.htmhttp://www.3gpp.org/ftp/Specs/html-info/37320.htmhttp://www.3gpp.org/ftp/Specs/html-info/37320.htmhttp://www.3gpp.org/ftp/Specs/html-info/32422.htm


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Measurements

Real time (Immediate MDT) and non-real time (Logged MDT) measurements

Measurements are configured to the UE by (E-)UTRAN by dedicated RRC signalling

The measurements should be tagged with UE position on best effort basis

in the best case GNSS information can be included,

otherwise cell ID or RF fingerprints

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RLF Reporting

To identify origin of radio link failures

Content

Cell measurement results at the time of the failure

Available accurate location information

Cell IDs for following cells

E-CGI or PCI where the failure happened

E-CGI of the cell to which UE attempted establish

the connection after the failure

Time between last successful HO and the failure

Reporting

At RRC Connection Setup, Re-establishment or Reconfiguration

UE Information procedure is used

upon retrieval report is removed, otherwise should be maintained

in the UE for 48hours

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Conclusions

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3GPP 2011 3GPP Workshop, Bangalore, 30 May 2011 35

Conclusions

E-UTRAN presents a flat architecture for low latency and delays

E-UTRAN Rel-10 introduces

carrier aggregation for higher bit rates and flexible spectrum usage

eICIC for improved support of HetNet

RN to increase coverage and deployment flexibility

MDT/SON to ease deployments and network optimisations


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3GPP 2011 3GPP Workshop Bangalore 30 May 2011

Thank You

36

www.3gpp.org

More

Information

about 3GPP:

[email protected]

Benoist SbireNokia Siemens Networks

[email protected]
mailto:[email protected]:[email protected]

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