3G Long-Term Evolution (LTE) and System Architecture Evolution (SAE)

3G Long-Term Evolution (LTE) and

System Architecture Evolution (SAE)

•

Intro

•

Architecture

•

Air Interface

•

Bearers and QoS

•

Call Handling Procedures

•

Mobility Handling

•

LTE-Advanced

Separate sessions on

•

LTE Radio

•

LTE Applications & Services

3GPP Evolution – Background

• 3G Long-Term Evolution (LTE) is the advancement of UMTS with the following

targets:

– Significant increase of the data rates: mobile broadband – Simplification of the network architecture

– Reduction of the signaling effort esp. for activation/ deactivation

• Work in 3GPP started in Dec 2004

– LTE is not backward compatible to UMTS HSPA

– LTE is a packet only network – there is no support of circuit switched services (no MSC)

– LTE started on a clean state – everything was up for discussion including the system architecture and the split of functionality between RAN and CN

• Since 2010, LTE has been further enhanced

– LTE-Advanced with increased performance targets

LTE Requirements and Performance Targets

High Peak Data Rates 100 Mbps DL (20 MHz, 2x2 MIMO)

50 Mbps UL (20 MHz, 1x2)

Improved Spectrum Efficiency 3–4x HSPA Rel.6 in DL*

2–3x HSPA Rel.6 in UL 1 bps/Hz broadcast

Improved Cell Edge Rates 2–3x HSPA Rel.6 in DL*

2–3x HSPA Rel.6 in UL Full broadband coverage Support Scalable BW

1.4, 3, 5, 10, 15, 20 MHz

Low Latency

< 5 ms user plane (UE to RAN edge) < 100 ms camped to active

< 50 ms dormant to active

Packet Domain Only High VoIP capacity

Simplified network architecture

* Assumes

2x2 in DL for LTE, but 1x2 for

Key Features of LTE to Meet Requirements

• Selection of OFDM for the air interface

– Less receiver complexity

– Robust to frequency selective fading and inter-symbol interference (ISI) – Access to both time and frequency domain allows additional flexibility in

scheduling (including interference coordination)

– Scalable OFDM makes it straightforward to extend to different transmission bandwidths

• Integration of MIMO techniques

– Pilot structure to support 1, 2, or 4 Tx antennas in the DL and MU-MIMO in the UL

• Simplified network architecture

– All IP architecture

– Reduction in number of logical nodes → flatter architecture

LTE/SAE Releases

Release 8 2008 Q4 First LTE release. All-IP Network (SAE). New OFDMA, FDE and MIMO based radio interface.

Release 9 2009 Q4 SAES Enhancements, WiMAX and LTE/UMTS Interoperability. LTE HeNB.

Release 10 2011 Q1 LTE Advanced fulfillingIMT Advanced 4G requirements. Backwards compatible with release 8 (LTE).

Release 11 2012 Q3 Advanced IP Interconnectionof Services. Service layer interconnection between national operators/carriers as well as third party application providers.

Heterogeneous networks (HetNet) improvements, Coordinated Multi-Point operation (CoMP). In-device Co-existence (IDC).

Release 12 2015 Q1 Enhanced Small Cells (higher order modulation, dual connectivity, cell discovery, self configuration), Carrier Aggregation (2 uplink carriers, 3 downlink carriers, FDD/TDD carrier aggregation), MIMO (3D channel modeling, elevation beamforming, massive MIMO), New and Enhanced Services (cost and range of MTC, D2D communication, eMBMS enhancements)

Release 13 2016 Q1 LTE in unlicensed, LTE enhancements for Machine-Type Communication. Elevation Beamforming/Full-Dimension MIMO, Indoor positioning. LTE-Advanced Pro.

Release 14 2017 Q2 Energy Efficiency, Location Services (LCS), Mission Critical Data over LTE, Mission Critical Video over LTE, Flexible Mobile Service Steering (FMSS), Multimedia

Broadcast Supplement for Public Warning System (MBSP), enhancement for TV service, massive Internet of Things, Cell Broadcast Service (CBS)

Release 15 Planned for Sept 2018

First "New Radio" (NR) release. Support for 5G Vehicle-to-x service, IP Multimedia Core Network Subsystem (IMS), Future Railway Mobile Communication System

How to navigate in 3GPP documents?

Overview on 3GPP document series:

http://www.3gpp.org/specifications/specification-numbering

• 22 series: Service aspects

• 23 series: Technical realization

– TS 23.203: Policy and Charging Control Architecture – TS 23.401: GPRS enhancements for E-UTRAN access – TS 23.501: Systems Architecture for the 5G System

• 24 series: Signaling protocols – user to network

– TS 24.301 NAS protocol for EPS (MM, SM procedures)

• 29 series: Signaling protocols - intra-fixed-network

– TS 29.171-173: Location Services

• 33 series: Security

• 36 series: LTE radio aspects

– TS 36.300: E-UTRAN – Overall description; Stage 2

– TS 36.331: Radio Resource Control (RRC); protocol specification

LTE/SAE Network Architecture

•

Evolved UTRAN (E-UTRAN)

•

Evolved Node B

•

Evolved Packet System (EPS)

•

MME, S-GW, P-GW, HSS, PCRF

Evolved UTRAN (E-UTRAN) Architecture

•

Key elements of radio network

architecture

– No more RNC

– RNC functionalities moved to evolved-NodeB (eNB)

– Termination of radio access in eNB

– X2 interface for seamless mobility (i.e. data/context forwarding) and load

management among eNBs

•

Note: Standard only defines

logical structure/nodes !

EPC = Evolved Packet Core

eNB MME / S-GW MME / S-GW eNB eNB S 1 S1 S 1 S1 X2 X2 X 2 E-UTRAN EPC

Evolved Node B

internet

eNB

RB Control Connection Mobility Cont.

eNB Measurement Configuration & Provision

Dynamic Resource Allocation (Scheduler) PDCP PHY MME S-GW S1 MAC Inter Cell RRM

Radio Admission Control

RLC

E-UTRAN EPC

RRC

Mobility Anchoring

EPS Bearer Control Idle State Mobility

Handling NAS Security P-GW UE IP address allocation Packet Filtering

eNodeB (eNB) provides all radio access functions

– Radio Resource Management (RRC, dynamic scheduling)

– Routing of User Plane data towards Serving Gateway

– Scheduling and transmission of paging and broadcast messages – IP header compression and user

plane ciphering

– Measurements and measurement reporting configuration

– Selection of a MME at UE

Evolved Packet System (EPS) Architecture

• EPS comprises EPC, E-UTRAN and UE

• E-UTRAN, i.e. eNB performs radio access functions

• EPC provides connectivity & performs mobility & user management functions

– separation between C Plane and U Plane in EPC

E-UTRAN

MME Serving GW PDN GW S1-U S1-MME S11 S5 Internet Evolved Packet Core (EPC)

SGi HSS S6a S10 PCRF Gx Gxc Control plane User plane

Mobility Management Entity (MME)

– UE Reachability in ECM-Idle/RCC-Idle state – Tracking area management

– NAS signaling/security, AS security control – Authentication & authorization

– S-GW/P-GW selection

– MME selection for HO with MME change, SGSN selection for HO to 3G/2G – Inter-EPC signaling for mobility between 3GPP access networks

– Bearer management functions including dedicated bearer establishment

E-UTRAN

MME Serving GW S1-U S1-MME S11 HSS S6a S10

Serving and PDN Gateways

Serving Gateway (S-GW)

– Serves EPC (U Plane) - E-UTRAN interface (S1-U interface)

– Local mobility anchor for inter-eNB as well as inter-3GPP handovers – Packet routing and forwarding

– Idle mode (ECM_IDLE) DL packet buffering and triggering of network-based service request procedure

– Accounting on user and QCI granularity for inter-operator charging – UL and DL charging per UE, PDN, and QCI

– Lawful Interception

PDN Gateway (P-GW)

– Serves SGi interface towards PDN – UE IP address allocation

– Mobility anchor for internetworking with non-3GPP networks

– DL packet filtering and assignment to EPS bearers (QoS) based on TFTs – QoS enforcement and flow based-charging according to rules from PCRF

(Policy and Charging Enforcement Function – PCEF) – Lawful Interception

Home Subscriber Server (HSS)

– User subscription repository for permanent user data (subscriber profiles including MSISDN, IMSI, keys, user capabilities, etc.)

– Dynamic user data esp. current location – Combines functionality of HLR and AuC

E-UTRAN

MME Serving GW PDN GW S1-U S1-MME S11 S5 Internet EPS Core SGi HSS S6a S10 PCRF Gx Gxc

PCRF – Policy Control and Charging Rules Function

Key Functionalities:

• fundamental entity to manage

flow-specific traffic differentiation and QoS provisioning

• maps QoS requirements of individual

services (SDF – beyond EPS) to an individual flow (EPS bearer – inside EPS)

• Subscriber-specific and

service-specific selection of Access Point Name (APN) and APN-specific policy control, e.g. IMS for voice

• ensures proper charging for use of

QoS enabled services (time-, volume- or event-based)

• instructs and authorizes the P-GW

(PCEF – Policy and Charging

Enforcement Function) about QoS

PCRF

• controls QoS and charging of

EPS bearers

• provides policy and charging

control (PCC) rules Serving GW PDN GW S5 Internet SGi PCRF Gx Gxc PCEF

EPS Protocol Architecture (U Plane)

Serving GW PDN GW S5/S8 GTP-U GTP-U UDP/IP UDP/IP L2 Relay L2 L1 L1 PDCP RLC MAC L1 IP Application UDP/IP L2 L1 GTP-U IP SGi S1-U LTE-Uu eNodeB RLC UDP/IP L2 PDCP GTP-U Relay MAC L1 L1 UE

LTE-Uu: radio interface (UE - eNB)

GPRS Tunneling Protocol for the user plane (GTP-U):

• tunnels user data between eNodeB and the GW as well as between the

EPS Protocol Architecture (C Plane)

SCTP L2 L1 IP L2 L1 IP SCTP S1-MME eNodeB _MME S1-AP S1-AP NAS MAC L1 RLC PDCP UE RRC MAC L1 RLC PDCP RRC LTE-Uu NAS Relay

Non-Access Stratum Signaling (NAS):

• supports mobility management functionality and user plane bearer activation,

modification and deactivation

• ciphering and integrity protection of NAS signaling

S1 Application Protocol (S1-AP): Signaling Application Layer between eNB

• S1 Interface is the reference point between eNodeB and EPC

• Two types of S1 Interface

– C Plane: S1-MME between eNodeB and MME – U Plane: S1-U between eNodeB and S-GW

Legend

– S1 Application Protocol (S1-AP): Application Layer Protocol between the eNodeB and the MME

– Streaming Control Transfer Protocol for the control plane (SCTP): guaranteed delivery of signaling messages between MME and eNodeB (S1); defined in RFC 4960 – GPRS Tunneling Protocol for the user plane (GTP-U): tunnels user data between

S1 Interface (eNB - EPC)

UDP L2 L1 IP L2 L1 IP UDP S1-U eNodeB S-GW GTP-U GTP-U SCTP L2 L1 IP L2 L1 IP SCTP S1-MME eNodeB _MME S1-AP S1-AP

X2 Interface (eNB - eNB)

• The X2 Interface is defined between two eNodeBs

– U Plane: X2-U used for data forwarding

– C Plane: X2-C used for HO support and load management

Legend:

– X2 Application Protocol (X2-AP): Application Layer Protocol between the eNodeBs

– Streaming Control Transfer Protocol for the control plane (SCTP): guarantees delivery of signaling messages between the eNodeB (X2)

– GPRS Tunneling Protocol for the user plane (GTP-U): tunnels user data

S5/S8 Interface (S-GW - P-GW)

• S5 and S8 interfaces provide user plane tunneling and tunnel management

between the S-GW and the P-GW

– S5 to connect S-GW to (non-collocated) P-GW of same operator – S8 to connect S-GW in visited PLMN to a P-GW in Home-PLMN

Legend

– GPRS Tunnelling Protocol for the control plane (GTP-C): tunnels signalling messages between S-GW and P-GW

– GPRS Tunneling Protocol for the user plane (GTP-U): tunnels user data between S-GW and P-GW

– Proxy Mobile IP (PMIP): transports signalling messages between S-GW and

S5/S8 interface via GTP UDP L2 L1 IP L2 L1 IP UDP S5 or S8 S-GW P-GW GTP-U/C GTP-U/C

S5/S8 interface via PMIP

S5 or S8 Serving GW PDN GW IPv4/IPv6 L2 L1 PMIPv6 IPv4/IPv6 L2 L1 PMIPv6

Air Interface Protocol Architecture

•

LTE Protocol Architecture

•

LTE Channels

LTE Protocol Architecture - Overview

eNB PHY UE PHY MAC RLC MAC MME RLC NAS NAS RRC RRC PDCP PDCP eNB PHY UE PHY MAC RLC MAC PDCP PDCP RLC S-Gateway C Plane U Plane

LTE Protocol Architecture – U Plane Overview

eNB PHY UE PHY MAC RLC MAC PDCP PDCP RLC

S-Gateway

RLC sub-layer performs:

Transfer of upper layer PDUs

Error correction through ARQ

Reordering of RLC data PDUs

Duplicate detection Flow control Segmentation/Concatenation of SDUs PDCP sub-layer performs: Header compression Ciphering

MAC sub-layer performs:

Mapping of logical channels to transport channels

Scheduling

Error correction through HARQ

Priority handling across UEs & logical channels

Physical sub-layer performs:

Modulation

Coding (FEC)

UL power control

Multi-stream transmission & reception (MIMO)

LTE Protocol Architecture – C Plane Overview

eNB PHY UE PHY MAC RLC MAC MME RLC NAS NAS RRC RRC PDCP PDCP UE eNodeB MME RRC sub-layer performs: Broadcasting Paging RRC Connection Management

Radio bearer control

Mobility functions

UE measurement reporting & control PDCP sub-layer performs:

Integrity protection & ciphering

NAS sub-layer performs:

Authentication

Security control

Idle mode mobility handling/ paging origination

Physical Layer Resource Scheduling and Allocation

Basic unit of allocation is called a Resource Block (RB)

12 subcarriers in frequency (= 180 kHz)

1 timeslot in time (= 0.5 ms, = 7 OFDM symbols)

Multiple resource blocks can be allocated to a user in a given subframe

The total number of RBs available depends on the operating bandwidth

12 sub-carriers (180 kHz)

Bandwidth (MHz) 1.4 3.0 5.0 10.0 15.0 20.0 Number of available

Physical Layer Services – Transport Channels

•

Shared Channel SCH (UL & DL)

– Carries majority of data and control traffic

– Adaptive modulation and coding (AMC) & Hybrid ARQ (HARQ)

– Possibility to use beamforming

– Controlled by eNodeB scheduler

•

Broadcast Channel BCH (DL)

– Broadcast of system information (MIB)

– Fixed transport format, broadcast over entire cell

•

Paging Channel PCH (DL)

– Notification of UEs

– Support of DRX, broadcast over entire cell

– Mapped to PDSCH

•

Random Access Channel RACH (UL):

– Provides indication of UE request

– Collision-based channel

Physical Layer Model: DL-SCH

CRC RB mapping Coding + RM Data modulation CRC Resource mapping Coding + RM QPSK, 16QAM, 64QAM Data modulation HARQ MAC scheduler N Transport blocks ( dynamic size S₁..., S_N) Node B Redundancyfor data detection Redundancyfor error detection Multi- antenna processing Resource/power assignment Modulation scheme version Antenna mapping HARQ info ACK/NACK Channel- state information, etc. Antenna mapping CRC RB mapping Coding + RM Data modulation CRC Resource demapping Decoding + RM Data demodulation HARQ UE HARQ info ACK/NACK Antenna demapping Error indications CRC RB mapping Coding + RM Data modulation CRC Resource mapping Coding + RM QPSK, 16QAM, 64QAM Data modulation HARQ MAC scheduler N Transport blocks ( dynamic size S₁..., S_N) Node B Redundancyfor data detection Redundancyfor error detection Multi- antenna processing Resource/power assignment Modulation scheme version Antenna mapping HARQ info ACK/NACK Channel- state information, etc. Antenna mapping CRC RB mapping Coding + RM Data modulation CRC Resource demapping Decoding + RM Data demodulation HARQ UE HARQ info ACK/NACK Antenna demapping Error indications Redundancy Redundancy

Physical Layer Model: UL-SCH

CRC RB mapping Coding + RM Data modulation Interl. CRC Resource demapping Decoding + RM Data demodulation Deinterleaving MAC scheduler Node B Resource assignment Modulation scheme Redundancy version Antenna mapping HARQ info ACK/NACK Antenna demapping CRC RB mapping Coding + RM Data modulation Interl. CRC Resource mapping Coding + RM Data modulation Interleaving HARQ UE HARQ info Antenna mapping Error indications Resource/power assignment Modulation scheme Antenna mapping HARQ

Uplink transmission control

Channel- state information, etc. CRC RB mapping Coding + RM Data modulation Interl. CRC Resource demapping Decoding + RM Data demodulation Deinterleaving MAC scheduler Node B Resource assignment Modulation scheme Redundancy version Antenna mapping HARQ info ACK/NACK Antenna demapping CRC RB mapping Coding + RM Data modulation Interl. CRC Resource mapping Coding + RM Data modulation Interleaving HARQ UE HARQ info Antenna mapping Error indications Resource/power assignment Modulation scheme Antenna mapping HARQ

Uplink transmission control

Channel- state information, etc. Redundancy version Redundancy version

Layer 2 – Structure (DL)

Segm. ARQ etc Multiplexing UE1 Segm. ARQ etc ... HARQ Multiplexing UEn HARQ BCCH PCCH Logical Channels Transport Channels MAC RLC Segm. ARQ etc Segm. ARQ etc PDCP

ROHC ROHC ROHC ROHC

Radio Bearers

Security Security Security Security

...

CCCH

MCCH MTCH

Unicast Scheduling / Priority Handling

Multiplexing MBMS Scheduling

Segm. Segm.

Layer 2 – Structure (UL)

Multiplexing ...

HARQ

Scheduling / Priority Handling

Transport Channels MAC RLC PDCP Segm. ARQ etc Segm. ARQ etc Logical Channels ROHC ROHC Radio Bearers Security Security CCCH UL structure – UE side

MAC Sublayer

• Services – Logical Channels

– Dedicated Traffic Channel DTCH (UL & DL): user data

– Dedicated Control Channel DCCH (UL & DL): control data (SRB1 & 2) – Common Control Channel CCCH: control data (SRB0)

– Broadcast Control Channel BCCH: broadcast of cell information – Paging Control Channel PCCH: notification of UEs

• Functions

– 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

Mapping between DL Channels

PCH: paging channel BCH: broadcast channel DL-SCH: DL shared channel

PDSCH: physical DL shared channel PDCCH: physical DL control channel PHICH: physical HARQ indication

channel

PCFICH: physical control format

indication channel

PBCH: Physical broadcast channel

BCCH PCCH CCCH DCCH DTCH MCCH MTCH BCH PCH DL-SCH MCH Downlink Logical channels Downlink Transport channels Downlink Physical Channels PDSCH PDCCH PBCH PHICH PCFICH PMCH

Mapping between UL Channels

CCCH DCCH DTCH RACH UL-SCH Uplink Logical channels Uplink Transport channels Uplink Physical Channels PUSCH PUCCH PRACH RACH: random access channel

UL-SCH: UL shared channel

PUSCH: physical UL shared channel PUCCH: physical UL control channel PRACH: physical random access channel

RLC Sublayer

•

Services

– TM (transparent mode) data transfer: no modification

– UM (unacknowledged mode) data transfer: error indication only

– AM (acknowledged mode) data transfer: error correction

•

Functions

– 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)

– Reordering of RLC data PDUs (only for UM and AM data transfer)

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

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

– RLC re-establishment

RLC Model for AM

Transmission buffer Segmentation & Concatenation Add RLC header Retransmission buffer RLC control Routing Reception buffer & HARQ

reordering SDU reassembly DCCH/DTCH DCCH/DTCH AM-SAP Remove RLC header RLC Acknowledged Mode Entity

PDCP Sublayer

•

Functions on U Plane

– Transfer of user data

– Ciphering and deciphering

– Robust header compression and decompression: ROHC

– In-sequence delivery of upper layer PDUs at PDCP

re-establishment procedure for RLC AM

– Duplicate detection of lower layer SDUs at PDCP

re-establishment procedure for RLC AM

– Retransmission of PDCP SDUs after handover (RLC AM only)

– Timer-based SDU discard in uplink

•

Functions on C Plane

– Transfer of control plane data

Data Flow through Layer 2

RLC header RLC PDU ... ... n n+1 n+2 n+3 RLC SDU RLC header PDCP SDU PDCP header PDCP PDU MAC Control element 1 ... R/R/E/LCID sub-header MAC header R/R/E/LCID sub-header ... R/R/E/LCID/F/L sub-header R/R/E/LCID padding sub-header MAC Control

element 2 MAC SDU MAC SDU

Padding (opt) MAC PDU PDCP SDU: IP packet (compressed/ uncompr.) PDCP header: 1 or 2 bytes

MAC control elements: • UL: MAC reports • DL: Timing advance • Control Information RLC header: • Sequence number • Segmentation/ concatenation information

RRC Layer

•

Services

– Broadcast of common control information

– Notification of UEs in RRC_IDLE, e.g. about an arriving call

– Transfer of dedicated control information, i.e. information for one

specific UE

•

Functions

– Broadcast of system information:

 Including NAS common information

 Information for UEs in RRC_IDLE state, e.g. cell (re-)selection

parameters, neighbouring cell information

 Information for UEs in RRC_CONNECTED state, e.g. common

RRC Layer (contd.)

•

Functions (contd.)

– RRC connection control:

 Paging

 Establishment, modification & release of RRC connection

 Initial security activation

 RRC connection mobility

 Establishment, modification & release of radio bearers carrying user

data (DRBs)

 Radio configuration control

 QoS control

 Recovery from radio link failure

– Inter-RAT mobility including e.g. security activation, transfer of

RRC context information

– Measurement configuration and reporting

– Generic protocol error handling

RRC States

RRC States incl. Inter-RAT mobility (3GPP only) Connection

establishment/release

Tracking Area

BCCH TAI 1 BCCH TAI 1 BCCH TAI 1 BCCH TAI 1 BCCH TAI 1 BCCH TAI 2 BCCH TAI 2 BCCH TAI 2 BCCH TAI 2 BCCH TAI 2 BCCH TAI 2 BCCH TAI 3 BCCH TAI 3 BCCH TAI 3 BCCH TAI 3 Tracking Area 1

Tracking Area 2 Tracking Area 3

• Tracking Area Identifier (TAI) sent over Broadcast Channel BCCH

• Tracking Areas can be shared by multiple MMEs

Bearers, States and Identifiers

•

EPS Bearers and Radio Bearers

•

RRC, ECM & EMM States

EPS Bearer Service Architecture – Overview

P-GW S-GW Peer Entity 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

Radio Bearer: SRB vs. DRB

•

A radio bearer is a RLC connection between UE and eNodeB

– Radio Bearers provide the data transfer over the air interface

•

Signaling Radio Bearers (SRB) are used to transfer RRC and NAS

control messages between UE and eNodeB

– SRB0: RRC messages over CCCH

– SRB1: RRC and NAS (when no security) messages over DCCH

– SRB2: NAS messages (when security established) over DCCH

•

Data Radio Bearer (DRB) transports packets of an EPS bearer

between UE and eNodeB

– One-to-one mapping between this data radio bearer and the EPS

bearer/E-RAB

– Each DRB has its own handling policy (QoS, priority, handling

during HO)

EPS Bearer: Default vs. Dedicated

•

EPS Bearer: logical association between UE and P-GW

– Aggregates one or several service data flows (SDF)

– Consists of three elements: Radio Bearer, S1 Bearer, S5/S8

Bearer

– Each bearer has its own QoS attributes (e.g. GBR/MBR)

•

Default EPS Bearer

– First connection, established during initial attach to a PDN

– Remains established during lifetime of PDN connection

– There can be multiple default bearers to different PDN (having a

unique IP address)

•

Dedicated EPS Bearers

– Additional EPS bearers established to the P-GW

– Multiple bearer connections with dedicated QoS policies

LTE RRC States

• No RRC connection, no context in

eNodeB (but EPS bearers are retained)

• UE controls mobility through cell

selection

• UE acquires system information

from broadcast channel

• UE monitors paging channel to

detect incoming calls

• UE-specific paging DRX cycle

controlled by upper layers

• RRC connection and context in

eNodeB

• Network controlled mobility

• Transfer of unicast and broadcast

data to and from UE

• UE monitors control channels

associated with the shared data channels

• UE provides channel quality and

feedback information

• Connected mode DRX can be

configured by eNodeB according to UE activity level

RRC_IDLE

RRC_Connected

Release RRC connection

EPS Connection Management States (ECM)

•

No signaling connection

between UE and core network

(no S1-U/ S1-MME)

•

No RRC connection (i.e.

RRC_IDLE)

•

UE performs cell selection and

tracking area updates (TAU)

•

Signaling connection

established between UE and

MME, consists of two

components

– RRC connection – S1-MME connection

•

UE location is known to

accuracy of Cell-ID

•

Mobility via handover

procedure

ECM_IDLE

ECM_Connected

Signaling connection released

EPS Mobility Management States (EMM)

•

EMM context does not hold

valid location or routing

information for UE

•

UE is not reachable by MME as

UE location is not known

•

UE successfully registers with

MME with Attach procedure or

Tracking Area Update (TAU)

– Setup EPS security context

•

UE location known (at least)

with accuracy of tracking area

•

MME can page UE

•

UE maintains at least one PDN

connection (default EPS

bearer)

EMM_Deregistered

Detach

Attach

Relation between EMM and ECM States

EMM-Deregistered

EMM-Registered

ECM-Idle RRC-Idle ECM-Idle RRC-Idle A B Power is turned off for a long time Power On Power On PLMN/

Cell Selection Cell SelectionPLMN/ Attach Attach ECM-Connected RRC-Connected ECM-Idle RRC-Idle C D

Handover Cell Reselection

• UE Inactivity Detection • TAU Accept • New Traffic • TAU Request UE Power Off • Detach • Attach Reject • TAU Reject • UE Power Off

EPS Bearer and Signaling Connections in EMM-registered State

RRC Connection Data Radio Bearer

S5 GTP-C S1 Bearer S5 Bearer S11 GTP-C C on tr ol Pl ane D at a Pl ane State C: • EMM-Registered • ECM-Connected • RRC-Connected S1 signaling Connection ECM Connection EPS Bearer UE eNB S-GW P-GW MME

EPS Bearer and Signaling Connections in EMM-registered State

RRC Connection

Data Radio Bearer

S5 GTP-C S1 Bearer S5 Bearer S11 GTP-C C on tr ol Pl ane D at a Pl ane S1 signaling Connection EPS Bearer MME UE eNB S-GW P-GW State D: • EMM-Registered • ECM-Idle • RRC-Idle ECM Connection

EMM, ECM and RRC States

Layer State Entity Description

EMM

EMM-Deregistered UE, MME •• UE is not attached to any LTE network MME does not know the current location of the UE, but may have

tracking area (TA) information last reported by the UE

EMM-Registered UE,MME •• UE has been attached to the LTE networkIP address has been assigned to the UE • EPS bearer has been established

• MME knows the current location of the UE with an accuracy of a

cell or, at least, a tracking area ECM ECM-Idle UE,

MME •• No NAS signalling connection (ECM connection) established yet UE has not been assigned physical resources, i.e. radio resources

(SRB/DRB) and network resources (S1 bearer/S1 signalling connection) yet

ECM-Connected UE, MME •• NAS signalling connection (ECM connection) is establishedUE has been assigned physical resources, i.e. radio resources

(SRB/CRB) and network resources (S1 bearer/S1 signalling connection)

RRC RRC-Idle UE, eNB • No RRC connection is established yet

EMM, ECM and RRC States – User View

Case State User Experiences (Examples)

A EMM-Deregistered+ ECM-Idle + RRC-Idle

• When a UE is switched on for the first time after subscription • When a UE is switched on after staying turned off for a long time • No UE context is present in the LTE network

B

EMM-Deregistered + ECM-Idle

+ RRC-Idle

• When a UE is switched on within a certain period of time after being

turned off

• When ECM connection is lost during communication due to radio link

failure

• Some UE context from the last attach can still be stored in the network

(e.g. to avoid running an AKA procedure during every Attach procedure)

C EMM-Registered+ ECM-Connected + RRC-Connected

• UE is attached to the network (an MME) and is using services (e.g.

Internet, VoIP, Live TV)

• Mobility handled by handover procedures

UE Location Information in Network Elements

Case State UE eNB S-GW P-GW MME HSS PCRF SPR

A EMM-Deregistered+ ECM-Idle + RRC-Idle - - - -B EMM-Deregistered+ ECM-Idle + RRC-Idle - - - - TAI of

last TAU MME -

-C EMM-Registered+ ECM-Connected + RRC-Connected

- Cell/

eNB Cell/eNB Cell/eNB Cell/eNB MME

-D EMM-Registered+ ECM-Idle + RRC-Idle

- - TAI of

-UE Identifiers

• IMSI: International Mobile Subscriber Identity

– Assigned by service provider, stored on SIM-card

• TMSI: Temporary Mobile Subscriber Identity

– Assigned temporarily by the control nodes

• IMEI: International Mobile Equipment Identity

– Unique identity for each mobile assigned by manufacturer

• MSISDN: Mobile Subscriber ISDN number

UE Identifiers

•

GUTI: Global Unique Temporary Identity

– UE Identity without revealing the mobile or the user

– GUTI has two parts

 Globally Unique MME Identifier (GUMMEI) identifies the MME,

assigned by service provider

 M-TMSI identifies UE within the MME, assigned by MME

•

The UE can attach to the network using either IMSI or GUTI

GUTI

GUMMEI M-TMSI

MME ID

48 bits 32 bits

UE Identifiers

•

RNTI: Radio Network Temporary Identifier

– Used by eNB to temporary address the UEs (MAC)

•

There exist a variety of different RNTIs

– Cell RNTI (C-RNTI): unique identification used for identifying RRC

connection and scheduling

– Paging RNTI (P-RNTI)

– Random Access RNTI (RA-RNTI)

– System Information RNTI (SI-RNTI)

– Transmit Power Control RNTI (TPC-RNTI)

– MBMS RNTI (M-RNTI, Rel.-9)

UE IDs maintained in Network Elements

GUTI (Globally Unique Temporary UE Identity) replaces TMSI to uniquely identify the UE and the used MME

Case State UE eNB S-GW P-GW MME HSS PCRF SPR

A EMM-Deregistered+ ECM-Idle + RRC-Idle

IMSI - - - - IMSI - IMSI

B

EMM-Deregistered + ECM-Idle

+ RRC-Idle

IMSI,

GUTI - - - IMSI, GUTI IMSI - IMSI

C EMM-Registered + ECM-Connected + RRC-Connected IMSI, GUTI, UE IP addr, C_RNTI C-RNTI, eNB/MME UE S1AP ID, Old/New eNB UE X2AP ID IMSI IMSI, UE IP addr IMSI, GUTI, UE IP addr, eNB/MME UE S1AP ID IMSI IMSI, UE IP addr IMSI D EMM-Registered+ ECM-Idle + RRC-Idle IMSI, GUTI, UE IP addr - IMSI IMSI, UE IP addr IMSI, GUTI, UE

Quality of Service

•

QoS Parameters

•

QoS Bearers

QoS Architecture (U Plane) - Overview

P-GW S-GW Peer Entity 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

Implementation of QoS

- QoS involves functions in

- C plane (connection management) and

- U plane (forwarding and policing)

- QoS requires end-to-end considerations of all involved network

entities as QoS can only be as good as its weakest element

- QoS is a cross-layer issue involves basically all layers

- Application layer: identification of service and classification,

source coding

- Transport layer: Retransmission policy – latency and reliability

- Network, data link and PHY layer: provisioning of needed

resources (transport and processing), forwarding and scheduling

over physical resources (including, modulation, channel coding,

PRB scheduling, diversity and redundancy strategy)

Options that influence QoS

QoS requirements and influencing factors

- throughput

⇒

depends on amount of resources allocated

- error rate/reliability

⇒

depends on robustness of transmission (modulation and coding,

TX power/SINR, redundancy, transmission diversity, etc.)

- latency

⇒

depends on scheduling strategy, processing delay, error

rate/retransmission rate, system load

QoS Class Identifier (QCIs)

QCI Resource Type Priority Packet Delay Budget Packet Error Loss Rate Example Services 1 2 100 ms ₁₀-2 Conversational Voice 2

GBR 4 150 ms 10-3 Conversational Video (Live Streaming)

3 3 50 ms ₁₀-3 Real Time Gaming

4 5 300 ms ₁₀-6 Non-Conversational Video (Buffered

Streaming)

5 1 100 ms ₁₀-6 IMS Signalling

6

6 300 ms ₁₀-6

Video (Buffered Streaming)

TCP-based (e.g., www, e-mail, chat, ftp, p2p file sharing, progressive video, etc.)

7 Non-GBR

7 100 ms ₁₀-3

Voice,

Video (Live Streaming) Interactive Gaming

8

8

300 ms ₁₀-6

Video (Buffered Streaming)

TCP-based (e.g., www, e-mail, chat, ftp, p2p file

Traffic Flow Template (TFT) and QoS Enforcement

Context

•

QCIs represent classes (or QoS types) of traffic

•

To provide a flow with a certain QoS, we need

– QCI, to specify handling wrt latency, error correction and data rate

– Throughput (guaranteed and maximum bit rate – GBR & MBR)

– TFT, to define rules to identify external flows and to map each flow

on specific EPS bearer (with QCI and throughput requirements)

– ARP (Admission and Retention Policy) for overload handling

Purpose of TFT

•

Identify IP packet flows (SDFs) and map to EPS bearers

•

Mapping implemented at the edges of the network, i.e. UE and P-GW

Content of TFT (for traffic identification)

•

IP source and destination

Important Terms and Ingredients for QoS

- QCI (QoS Class Identifier) – defines QoS requirements with

exception of throughput

- ARP (Admission and Retention Policy) – defines priority of EPS

bearer for admission and contention cases

- TFT (Traffic Flow Template) – defines mapping of SDFs on EPS

bearer (formerly PDP context) – unit for QoS management

- Data rate, latency, error rate/reliability

- SDF (Service Data Flow) – service-specific IP flow

- EPS bearers (IP addresses, port numbers, protocol ID)

- IP CAN (end-to-end bearer), i.e. an IP flow

- GBR: Guaranteed Bit Rate

- MBR: Maximum Bit Rate

- AMBR: Aggregated MBR

Service Data Flow (SDF):

- defines QCI, ARP, MBR and possibly GBR EPS bearer

- defines QCI, ARP, possibly GBR, MBR or UE-AMBR and APN-AMBR - may combine several SDFs to a single EPS bearer

EPS session:

- comprises one or more SDFs (i.e. services) mapped to one or more EPS

Source: www.netmanias.com

QoS Parameters for SDF and EPS Bearer

Enforcement of QoS

Main entities for QoS handling are the network edges, i.e.

- P-GW for the DL

Source: www.netmanias.com

EPS bearers

(inside EPS) (outside EPS)SDFs

QoS Policing and Scheduling for DL

SDF-EPS mapping via TFTs Policing

QoS Policing and Scheduling for UL

SDF-EPS mapping via TFTs

Call Handling Procedures

•

Basic procedures

− Paging − RRC Connection Establishment − Dedicated S1 Establishment − E-RAB Setup/Release − RRC Re-establishment

•

End-to-end procedures:

− First Attach

Call Handling: End-to-End Scenarios

End-to-end scenarios

(cf 3GPP 23.401) eNB use cases Applicable eNB procedure blocks Applicable 3GPP RRC, S1, X2 procedures

Attach MO Default E-RAB setup RRC Connection Establishment RRC: RRC Connection Establishment S1AP:

-S1 Dedicated Establishment RRC:

-S1-AP: Initial UE Message NAS Transfer RRC: NAS Direct Transfer

S1-AP: NAS Transport

Initial Context Setup RRC: RRC Connection Reconfiguration S1-AP: Initial Context Setup

Detach S1 release (EPC triggered) S1 Release (EPC triggered) RRC: RRC Connection Release S1-AP: UE Context Release Tracking Area Update Connection establishment without

E-RAB setup RRC Connection establishment RRC:S1-AP: RRC Connection Establishment -S1 Dedicated Establishment RRC:

-S1-AP: Initial UE Message NAS Transfer RRC: NAS Direct Transfer

S1-AP: NAS Transport

UE Release RRC: RRC Connection Release S1-AP: UE Context Release UE triggered Service Request MO Default E-RAB setup Same as “Attach”

Network Triggered Service

Request MT Default E-RAB setup Paging + MO Default E-RAB Setup Dedicated bearer activation (or UE

requested bearer resource activation)

Dedicated E-RAB setup E-RAB Setup RRC: RRC Connection Reconfiguration S1-AP: E-RAB Setup

Dedicated bearer de-activation (or UE Requested Bearer Resource Release)

Dedicated E-RAB release E-RAB Release RRC: RRC Connection Reconfiguration S1-AP: E-RAB Release

S1 release (EPC triggered) S1 release (EPC triggered) S1 Release (EPC triggered) RRC: RRC Connection Release S1-AP: UE Context Release S1 release (ENB triggered) S1 release (ENB triggered) S1 Release Request (ENB RRC: RRC Connection Release

Paging

• Upon receiving an S1-AP PAGING message, the eNB determines the list of

cells on which to page the UE from the “List of TAIs” provided by the S1-AP PAGING message

• For each cell on which the UE must be paged, the eNB will:

– Compute the frame number and sub-frame number of the UE's paging occasion (based on UE Identity Index Value, DRX paging cycle)

– ASN1 encode the paging record for the given UE

– Provide this data to the scheduler along with the DRX paging cycle

RRC: Paging

UE eNB MME

RRC Connection Establishment

•

RRC Connection Establishment procedure establishes SRB1 between

UE and eNB

UE eNB RRCConnectionRequest InitialUE-Identity establishmentCause RRCConnectionSetup RadioResourceConfigDedicated RRCConnectionSetupComplete SelectedPLMN-Identity, RegisteredMME NAS-DedicatedInformation CCCH SRB0 RLC TM CCCH SRB0 RLC TM DCCH SRB1 RLC AM UE RRC_co nnected UE RRC_idle Random Access

RRC Connection Establishment (cont.)

•

RRC Connection Setup uses contention-based Random Access

– RACH only used for indication of scheduling request

– First data sent on assigned UL-SCH

•

Establishment causes

– Emergency

– High Priority Access

– Mobile Terminated (MT) Access

– Mobile Originated (MO) Signaling

– Mobile Originated Data

•

In case of failure (RRC Connection Reject) UE will repeat RRC

Dedicated S1 Establishment

•

Dedicated S1 Establishment procedure establishes the S1 dedicated

connection to complement RRC connection

S1-AP: DL NAS TRANSPORT

MME S1-AP UE Identity, eNB S1-AP UE identity

UL INFORMATION TRANSFER DL INFORMATION TRANSFER

UE eNB MME

S1-AP: UL NAS TRANSPORT S1-AP: INITIAL UE MESSAGE

eNB S1-AP UE Identity

S1-AP: INITIAL CONTEXT SETUP RESPONSE S1-AP: INITIAL CONTEXT SETUP REQUEST MME S1-AP UE Identity, eNB S1-AP UE identity

(Case 1) or (Case 2)

RRC Connection Establishment

AS Security Activation E-RAB Setup

Dedicated S1 Establishment (contd.)

•

Upon reception of

RRC Connection Setup Complete

, the eNB will:

– Perform MME selection if needed

– Allocate an eNB UE identity that will be sent to the MME

– Send S1-AP INITIAL UE MESSAGE towards the selected MME

•

Case 1: UE not authenticated

– Exchange of NAS-messages for authentication

– MME S1-AP UE identity received in S1-AP DL NAS TRANSPORT

message

•

Case 2: UE authenticated (e.g. after case 1)

– Initial Context Setup procedure to establish the first E-RAB(s)

– eNB will initiate security activation over the radio interface prior

to establishment of SRB2 and/or DRBs

– eNB stores “

UE Radio Capability

” IE either from S1-AP message

or by using RRC UE capability transfer procedure

– MME S1-AP UE identity received in S1-AP INITIAL UE CONTEXT

SETUP REQUEST message

Dedicated E-RAB setup

•

Dedicated E-RAB setup procedure establishes new E-RAB(s) after

Initial Context Setup

– eNB will manage new E-RAB establishment similarly to SRB2 and

DRB(s) establishment in Initial Context Setup case.

UE eNB MME

S1AP E-RAB SETUP REQUEST eNB S1-AP UE Identity MME S1-AP UE Identity E-RAB to be Setup List

S1AP E-RAB SETUP RESPONSE MME S1-AP UE Identity

eNB S1-AP UE Identity E-RAB Setup List RRCConnectionReconfiguration

nas-DedicatedInformationList RadioResourceConfigDedicated (DRB(s))

E-RAB Release

•

E-RAB Release procedure is used to release one or several E-RABs

– Initiated by MME

– When initiated by eNB: S1-AP E-RAB RELEASE INDICATION sent

to MME

UE eNB MME

S1AP E-RAB RELEASE COMMAND eNB S1-AP UE Identity MME S1-AP UE Identity E-RAB to be Released List

S1AP E-RAB RELEASE RESPONSE MME S1-AP UE Identity

eNB S1-AP UE Identity E-RAB Release List RRCConnectionReconfiguration

nas-DedicatedInformationList RadioResourceConfigDedicated (DRB(s))

UE Context Release

•

UE Context Release procedure releases all E-RABs for an UE,

including S1-U bearers, Radio bearers and the S1-MME signaling

connection for the UE

– Initiated by MME

– When initiated by eNB: S1-AP UE CONTEXT RELEASE REQUEST

message sent before to MME

UE eNB MME

RRCConnectionRelease

S1AP UE CONTEXT RELEASE COMMAND eNB S1-AP UE Identity MME S1-AP UE Identity Cause

S1AP UE CONTEXT RELEASE COMPLETE MME S1-AP UE Identity

RRC Connection Re-establishment

• Re-establishment procedure is triggered in the following cases:

– UE detects a L1/ L2 failure

– RRC Connection Reconfiguration procedure fails – Mobility procedure fails

• eNB re-establishes the RRC connection

– Re-establishment of MAC, RLC and PDCP for SRBs and DRB – Re-establishment of SRB1

– RRC Connection Reconfiguration used afterwards to re-establish SRB2 and DRB(s)

RRCConnectionReestablishmentRequest

UE eNB

RRCConnectionReestablishment

Initial Attach Procedure

UE eNB MME SGW PGW PCRF HSS/EIR

Attach Request RRC Connection Est.

Authentication/ Security

Update Location Create Session Req.

IP-CAN Session Est. Create Session Resp.

Create Session Req.

Create Session Resp.

Attach Complete

UL Data

DL Data

Modify Bearer Initial Context Setup/ Attach Accept

Tracking Area Update with MME/S-GW Change

UE eNB New MME New S-GW Old MME P-GW HSS

TAU Request RRC Connection Est.

Authentication/ Security

Create Session Resp.

TAU Complete

Context Retrieval

Context Ack Create Session Req.

Modify Bearer

Update Location

Cancel Location Update Location Ack

TAU Accept

Old S-GW

LTE Mobility

•

Handover Principle, UE Measurements

•

LTE-Handover over X2, S1

LTE Handover

• LTE uses UE-assisted network-controlled handover

– UE reports measurements; network decides when to handover and to which cell

– Relies on UE to detect neighbor cells → no need to maintain and

broadcast neighbor lists

 Allows "plug-and-play" capability; saves BCH resources

– For search and measurement of inter-frequency neighboring cells only carrier frequencies need to be indicated

• X2 interface used for handover preparation and forwarding of user data

– Target eNB prepares handover by sending required information to UE transparently through source eNB as part of the Handover Request Acknowledge message

 New configuration information needed from system broadcast

 Accelerates handover as UE does not need to read BCCH on target cell

– Buffered and new data are transferred from source to target eNB until

path switch → prevents data loss

UE Measurements

•

In LTE the UE measurements are mainly used for HO purpose

•

Measurement quantities depend on the RAT to measure

– LTE (intra-/ inter-frequency)

 Reference Signal Received Power (RSRP)

 Reference Signal Received Quality (RSRQ)

– UMTS (FDD)

 Carrier Received Signal Strength Indicator (RSSI)

 CPiCH Received Signal Code Power (RSCP)

 CPiCH Ec/I0

– GSM

 Carrier Received Signal Strength Indicator (RSSI)

•

eNB scheduler shall provide transmission gaps to allow

UE Measurement Model

•

The measurement model consists of the following parts

•

Measurement filtering:

𝐹𝐹

_𝑛𝑛

= 1

− 𝑎𝑎 ⋅ 𝐹𝐹

_𝑛𝑛−1

+

𝑎𝑎 ⋅ 𝑀𝑀

_𝑛𝑛

Filter coefficient:

_𝑎𝑎

_{= 2}

− ⁄𝑘𝑘 4

_,

_𝑘𝑘

_{= 0 … 19}

sample rate at point B: 200msec

•

Reporting criteria

– Measurement triggers for event-based reporting: handover

– Periodical reporting: e.g. tracing

Layer 1 filtering Layer 3 filtering Evaluation of reporting criteria A B C D C' RRC configures parameters RRC configures parameters

Handover Measurement Events

•

Intra-LTE measurement events (intra- and inter-frequency)

– A1: Serving cell better than threshold

– A2: Serving cell worse than threshold

– A3: Neighbor cell with offset better than serving cell

– A4: Neighbor cell better than threshold

– A5: Serving cell worse than threshold #1, neighbor cell better

than threshold #2

•

Inter-RAT measurement events

– B1: Inter-RAT neighbor cell better than threshold

– B2: Serving cell worse than threshold #1, Inter-RAT neighbor cell

better than threshold #2

•

To reduce signaling amount, hysteresis and time-to-trigger might be

X2 Handover: Preparation Phase

UE

UE Source Source _eNBeNB Measurement Control

Target eNB Target

eNB MMEMME S-GWsGW

Packet Data Packet Data

UL allocation Measurement Reports HO decision Admission Control HO Request HO Request Ack DL allocation RRC Connection Reconfig. L1/L2 signaling L3 signaling User data

• HO decision is made by source eNB based on UE measurement report

• Target eNB prepares HO by sending relevant info to UE through source eNB as part of HO request ACK command, so that UE does not need to read target cell BCH

X2 Handover: Execution Phase

UE

UE Source Source _eNBeNB Target Target _eNBeNB MMEMME _S-GWsGW

Detach from old cell,

sync with new cell Deliver buffered packets and forward new packets to target eNB

DL data forwarding via X2

Synchronisation

UL allocation and Timing Advance

RRC Connection Reconfig. Complete

L1/L2 signaling

L3 signaling User data

Buffer packets from source eNB

Packet Data

Packet Data

• RACH is used here only so target eNB can estimate UE timing and provide timing advance for synchronization; RACH timing agreements ensure UE does not need to read target cell P-BCH to obtain SFN (radio frame timing from SCH is sufficient to know PRACH locations)

X2 Handover: Completion Phase

UE

UE Source Source _eNBeNB Target Target _eNBeNB MMEMME _S-GWsGW

DL Packet Data

Path switch req

Modify bearer req.

Switch DL path

Path switch req ACK UE Context Release

Packet Data _{Packet Data}

L1/L2 signaling L3 signaling User data DL data forwarding Flush DL buffer, continue delivering

in-transit packets

End Marker

Release resources

Packet Data

End Marker

LTE Handover: Illustration of Interruption Period

UL

U- plane active

U- plane active

UE

UE Source Source _eNBeNB Target Target _eNBeNB

UL

U- plane active

U- plane active

UEs stops Rx/Tx on the old cell

DL synchronisation + Timing advance + UL resource request/grant DL sync + RACH (no contention) + Timing Adv + UL Resource Req and Grant ACK HO Request HO Confirm Handover Latency (approx. 55 ms) Approx. 20 ms Measurement Report HO Command HO Complete Handover Interruption (approx. 35 ms) Handover Preparation

S1 Handover

•

S1 handover is performed, when there is no X2 connection between

source and target eNodeB

– Operator preference

– No logical connectivity, e.g. HeNB

•

Handover procedure is similar to X2 handover, except for

– C Plane messages forwarded via MME

– U Plane data forwarded via S-GW

S1 Handover Procedure

UE

UE Source Source _eNBeNB Target Target _eNBeNB MMEMME S-GWsGW Packet Data Packet Data

Measurement Reports HO decision Admission Control HO Required HO Command RRC Connection Reconfig. L3 signaling User data

ENB Status Transfer

HO Request HO Request Ack

MME Status Transfer

Detach from old cell, sync with new cell

Path switch procedure/ UE Context Release in source eNB

DL data forwarding via S1 RRC Connection Reconfig. Complete

Packet Data

Packet Data UL Packet Data HO Notify

References

• Literature

– Holma, Toskala: LTE for UMTS – Evolution to LTE-Advanced, Wiley 2011 – E. Dahlman, S. Parkvall, J. Sköld: 4G, LTE-Advanced Pro and the Road

to 5G, 3rd _{edition, Aademic Press, 2016}

– Sesia, Toufik, Baker: LTE - The UMTS Long Term Evolution: From Theory to Practice, Wiley 2011

– LTE EMM and ECM States: www.netmanias.com

– The LTE Network Architecture - strategic white paper –

Alcatel-Lucent, 2009

• 3GPP standards (www.3gpp.org/specifications):

– 36-series: LTE radio aspects

– 36.300: E-UTRAN – Overall description; Stage 2 – 36.213: Physical layer procedures

– 36.321: Medium Access Control (MAC) protocol specification – 36.331: Radio Resource Control (RRC); protocol specification – 36.413: S1 Application Protocol (S1AP)