3GPP Telecommunication Systems Long Term Evolution (LTE) Gert-Jan - - PowerPoint PPT Presentation

Mobile and Wireless; 23-10-2014 2012-06-05

3GPP Telecommunication Systems Long Term Evolution (LTE)

Gert-Jan van Lieshout

Samsung Electronics Research Institute Deventer, The Netherlands gert.vanlieshout@samsung.com

Mobile and Wireless; 23-10-2014 2

Outline

• Introduction [4]-[9]
• 3rd Generation Partnership Project (3GPP)
• Start of LTE
• Overall LTE architecture
• LTE RAN: “E-UTRAN” [11]-[34]
• E-UTRAN Release-8

E-UTRAN architecture User Plane protocol Stack Control Plane protocol Stack Specific Features:

• Quality of Service
• Mobility
• E-UTRAN after Release-8
• LTE Core Network: “EPC” [36]-[54]
• Core Network Architecture
• Signalling Sequence Examples
• PS CN evolution
• Interworking with non-3GPP accesses
• Summary [56]

Outline

Mobile and Wireless; 23-10-2014

I Introduction

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3rd Generation Partnership Project (3GPP)

3GPP structure

(Japan) (Japan) (China) (Korea) (USA) (Europe)

www. 3gpp.org

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Competition situation around 2006:

GSM did not have any serious competition a decade

Even today, still the unchallenged nr. 1 in number of mobile phones

UMTS had competition from the beginning but won

CDMA-2000 (3GPP2 evolution “UMB” on side-track)

More data centric solutions are standardised by IEEE:

802.16

Mainly backhaul broadband wireless (OFDM, nomadic)

802.16e (“WiMax”)

Broadband wireless access to end-users (OFDM, with mobility support) Large group of supporters (Samsung, Intel, ….) Flatter architecture (2 nodes) => Cheaper

802.20

Also based on OFDM with mobility support

Can HSDPA/EDCH meet the WiMax competition ? (=> Yes) 3GPP answer: “Long Term Evolution” (LTE)

Why LTE ?

Mobile and Wireless; 23-10-2014 6

LTE & EPC

Around 2006, 3GPP RAN groups start to work on LTE “Long Term Evolution”. In parallel SA2 started to work on the EPS ‘Evolved Packet System’ started. Main objectives:

Ensure competitiveness in the next 10 years and behond Enhanced capability of 3GPP system to cope with rapid growth of IP data traffic Support for (seamless) mobility between heterogeneous access networks

Important parts of such a long-term evolution included:

Reduced latency, higher user data rates, improved system capacity and coverage, and reduced overall cost for the operator “flat IP Architecture” LTE/SAE system was to be packet only system

Migration aspects were to be taken into account for the above, i.e. how to migrate from the existing architecture Resulted in 2 new main architecture documents:

23.401: GPRS enhancements for E-UTRAN 23.402: Architecture enhancements for non-3GPP accesses

Why LTE ?

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Overall network architecture (non roaming)

LTE: Overall architecture Source: TS23.401

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Uu (radio) interface: Terminal to Network

UE Network / “Infrastructure side”

Uu

LTE: Basic principle

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S1 interface: Separates RAN from CN

UE CN

Uu S1

E-UTRAN

Non-Access Stratum (NAS) functionality

• no radio specific functionality

Access Stratum (AS), Radio Network functionality

• all radio specific functionality
• no user service specific functionality

LTE: Basic principle

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II

E-UTRAN

E-UTRAN Release-8

• E-UTRAN architecture
• User Plane protocol Stack
• Control Plane protocol Stack
• Specific Features:
• Quality of Service
• Mobility

E-UTRAN beyond Release-8

• Release-10: Carrier Aggregation
• Release-11
• Release-12…

Mobile and Wireless; 23-10-2014

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

• ther 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-C (control) interface eNBs are connected to the to the Serving Gateway (S-GW) by means of the S1-U (user data) interface

11 eNB MME / S-GW MME / S-GW eNB eNB S1 S1 S1 S 1 X2 X2 X2 E-UTRAN

E-UTRAN architecture

Uu

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E-UTRAN Functions

Main functions hosted by eNB include

Functions for Radio Resource Management:

Connection Mobility Control, Radio Bearer Control, Radio Admission 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

• f paging messages

(originated from the MME); Scheduling and transmission of broadcast information (originated from the MME or O&M)

12

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

E-UTRAN architecture

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User Plane protocol stack (1)

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

• reliability increase through retransmissions
• 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

13

eNB PHY UE PHY MAC RLC MAC PDCP PDCP RLC

E-UTRAN protocol stack: User Plane

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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PDCP SDU IP Payload Header H IP PDU#1 Radio Bearer 1 MAC SDU CRC Transport Block H H H RLC SDU H RLC PDU RLC PDU

Multiplexing

MAC SDU

PDCP RLC MAC PHY

SN PDCP SDU IP Payload Header H IP PDU#2 Radio Bearer 1 RLC SDU SN RLC SDU PDCP SDU IP Payload Header H IP PDU#2 Radio Bearer 2 SN

E-UTRAN protocol stack: User Plane

User Plane protocol stack (2)

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Control Plane protocol stack (1)

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

15

eNB PHY UE PHY MAC RLC MAC MME RLC NAS NAS RRC RRC PDCP PDCP

E-UTRAN protocol stack: Control Plane

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Only two RRC states

IDLE and CONNECTED

(Compare to IDLE, CELL_PCH, CELL_FACH, CELL_DCH in UMTS)

Idle mode

UE known in EPC, not in EUTRAN UE 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

Unicast data communication possible 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

16

Control Plane protocol stack (2)

E-UTRAN protocol stack: Control Plane

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Core Network

S1 Uu (the “radio interface”)

• d

UE 1, Connected mode

eNB Cells

• d

UE 2, Idle mode

TA 403 (Tracking Area) UE1 -> S1-Conn. Y UE1 -> Cell X RRC-connection S1-connection Y = Data record X UE2 -> TA 403 S1 TA 403 (Tracking Area) E-UTRAN Mobility

Control Plane protocol stack (3)

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E-UTRAN is responsible for Radio Bearer management and therefore ensuring QoS over the radio

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

18 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

End-to-End QOS

E-UTRAN QOS

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RB ¡establishment ¡based ¡on ¡QoS ¡parameters ¡from ¡MME ¡

QoS ¡Class ¡Iden-fier ¡(QCI) ¡per ¡bearer: ¡ ¡ ¡scalar ¡value ¡which ¡iden@fies ¡a ¡par@cular ¡ ¡service ¡in ¡terms ¡of ¡resource ¡type, ¡priority, ¡ ¡ ¡packet ¡delay ¡budget ¡and ¡packet ¡error ¡rate ¡[23.203] ¡ Guaranteed ¡Bit ¡Rate ¡(GBR) ¡per ¡bearer ¡ Maximum ¡Bit ¡Rate ¡(MBR) ¡per ¡bearer ¡ Aggregate ¡Maximum ¡Bit ¡Rate ¡(AMBR) ¡per ¡group ¡of ¡bearers ¡

RB ¡Scheduling ¡based ¡on ¡QoS ¡parameters ¡from ¡MME ¡and ¡scheduling ¡ ¡ informa@on ¡from ¡UE ¡

Channel ¡Quality ¡Indica@on ¡ Buffer ¡Status ¡Report ¡ Power ¡Headroom ¡Report ¡

Scheduling ¡for ¡downlink ¡is ¡eNB ¡implementa@on ¡specific ¡ Scheduling ¡for ¡uplink ¡is ¡only ¡par@ally ¡specified ¡

Logical ¡channel ¡priori@za@on ¡and ¡avoid ¡starva@on ¡[36.321] ¡

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Radio Bearer QOS

E-UTRAN QOS

Traffic class Maximum bitrate Delivery order Maximum SDU size SDU format information SDU error ratio Residual bit error ratio Delivery of erroneous SDUs Transfer delay Guaranteed bit rate Traffic handling priority Allocation/ Retention priority Source statistics descriptor

Compare UMTS:

NAS request to AS

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QOS: Reliability

L1 ¡applies ¡24 ¡bit ¡CRC ¡protec@on ¡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 ¡so\-­‑combined ¡with ¡previous ¡a]empt ¡(efficient) ¡

ARQ ¡status ¡report ¡sent ¡as ¡MAC ¡data ¡

RLC ¡Status ¡is ¡sent ¡on ¡demand ¡(poll, ¡@mer, ¡gap ¡detec@on) ¡ 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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E-UTRAN QOS

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Retransmissions: comparison to GSM/ UMTS

eNB PHY UE PHY MAC RLC MAC PDCP PDCP RLC

GPRS

GTP: GPRS Tunneling Protocol SNDCP: SubNetwork Dependent Convergence Protocol a.o.: header/payload compression LLC: Logical Link Control RLC (GPRS): Radio Link Control

SNDCP GSM RF Um Gb Gn Gi

MT BSS GGSN

IP

BTS

MAC RLC LLC GSM RF L1 L2 L1 L1 L2 Abis L2 MAC RLC BSSGP L1 L1 L2 L2 BSSGP LLC SNDCP IP UDP GTP-U L1 L1 L2 L2 IP UDP IP GTP-U E.g. L2TP

• r

IP tunnel

SGSN

Appl

PDCP: Packet Data Convergence Protocol a.o.: header compression RLC (UMTS): Radio Link Control

PDCP Uu Iu Gn Gi

UE SRNC GGSN Node-B

MAC RLC IP L1 ATM L1 L1 ATM Iub ATM FP MAC IP L1 L1 L2 L2 IP UDP IP GTP-U E.g. L2TP

• r

IP tunnel

SGSN

Appl UMTS RF UMTS RF FP RLC PDCP GTP-U UDP L1 L1 L2 ATM IP UDP IP GTP-U GTP-U UDP

UMTS REL-99

UMTS RF MAC-hs MAC-e UMTS RF MAC-hs MAC-e REL-5/6

LTE

LTE:

• MAC: performs retransmissions to obtain loss rate of around E-2
• RLC: retransmissions up to loss rate of around E-6 or lower
• PDCP:

retransmissions at intra-LTE handover

E-UTRAN QOS

Mobile and Wireless; 23-10-2014

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

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E-UTRAN QOS

QOS: Latency

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Mobility

IDLE: Cell Reselection

UE controlled cell reselection

UE decides when to change cell, influenced by network steering parameters

CONNECTED: Handover

UE-assisted :

Measurements are made and reported by the UE to the network

Network-controlled :

Target cell is selected by the network, not by the UE and Handover control in E-UTRAN (not in packet core)

Lossless:

Packets are forwarded from the source to the target

Late path switch:

Only once the handover is successful, the packet core is involved

Two handover approaches:

S1-handover (“normal handover“ conform GSM/UMTS; no inter-eNB connection required) X2-handover (see next slides)

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E-UTRAN Mobility

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Source eNB Target eNB UE X2 S-GW MME control plane user plane user data S1-U S1-MME control plane signalling measurements

Source ¡eNB ¡configures ¡UE ¡ measurements ¡

target ¡frequency ¡and ¡triggers ¡

Source ¡eNB ¡receives ¡UE ¡ ¡ measurement ¡reports ¡ HO ¡decision ¡is ¡made ¡and ¡ ¡ target ¡eNB ¡is ¡selected ¡by ¡the ¡ source ¡eNB ¡

Mobility: X2-Handover(1)

E-UTRAN Mobility: Handover

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HO ¡request ¡sent ¡from ¡source ¡ eNB ¡to ¡target ¡eNB ¡ Target ¡eNB ¡performs ¡ ¡ admission ¡control ¡and ¡accepts ¡ the ¡HO ¡request ¡ HO ¡Ack ¡sent ¡to ¡source ¡eNB ¡ ¡ from ¡target ¡eNB ¡

25

Source eNB Target eNB UE S-GW MME control plane user plane user data S1-U S1-MME control plane signalling measurements HO request HO Request Ack

Mobility: X2-Handover(2)

E-UTRAN Mobility: Handover

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Source eNB Target eNB UE X2 S-GW MME control plane user plane user data S1-U S1-MME control plane signalling HO command

HO ¡command ¡is ¡sent ¡to ¡the ¡UE ¡

RRCConnec'onReconfigura'on ¡ message ¡including ¡the ¡ ¡ mobilityControlInfo ¡

Data ¡forwarding ¡ini@ated ¡ towards ¡the ¡target ¡eNB ¡ ¡

Mobility: X2-Handover(3)

E-UTRAN Mobility: Handover

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Source eNB Target eNB UE X2 S-GW MME control plane user plane user data S1-U S1-MME control plane signalling HO confirm

UE ¡accesses ¡the ¡target ¡eNB ¡ and ¡confirms ¡the ¡HO ¡

RACH ¡procedure ¡is ¡ini@ated ¡ RRCConnec'onReconfigura'onComplete ¡ is ¡sent ¡

Mobility: X2-Handover(3)

E-UTRAN Mobility: Handover

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Source eNB Target eNB UE X2 S-GW MME control plane user plane user data control plane signalling

Target ¡eNB ¡requests ¡EPC ¡to ¡switch ¡ the ¡data ¡path ¡

eNB ¡→ ¡MME ¡: ¡path ¡switch ¡request ¡ ¡ MME ¡→ ¡S-­‑GW ¡: ¡modify ¡bearer ¡request ¡ S-­‑GW ¡→ ¡MME ¡: ¡modify ¡bearer ¡response ¡ MME ¡→ ¡eNB ¡: ¡path ¡switch ¡request ¡ACK ¡

Target ¡eNB ¡no@fies ¡the ¡source ¡eNB ¡ that ¡UE ¡resources ¡can ¡be ¡released ¡

Mobility: X2-Handover(4)

E-UTRAN Mobility: Handover

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Source eNB Target eNB X2 S-GW MME control plane user plane user data S1-U S1-MME control plane signalling

Path ¡is ¡switched ¡ Source ¡eNB ¡finishes ¡forwarding ¡ packets ¡

• nce ¡completed ¡UE ¡context ¡can ¡be ¡

cleared ¡and ¡resources ¡freed ¡

HO ¡is ¡completed ¡

UE

Mobility: X2-Handover(5)

E-UTRAN Mobility: Handover

Mobile and Wireless; 23-10-2014

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

Release-10 Features:

Carrier Aggregation: increase the bit rate and reach IMT-A requirements [WID] eICIC: to efficiently support highly increasingly complex network deployment scena rios with 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]

30

Release-10

E-UTRAN: Beyond Release-8

Mobile and Wireless; 23-10-2014

Goal of Carrier aggregation is to aggregate Rel-8 compatible carriers to increase 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

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LTE-Advanced maximum bandwidth Carrier 1 Carrier 4 Carrier 5 Carrier 3 Carrier 2 Rel’8 BW Rel’8 BW Rel’8 BW Rel’8 BW Rel’8 BW

Release-10: Carrier Aggregation(1)

E-UTRAN: Beyond Release-8

Mobile and Wireless; 23-10-2014

Basic Concept

When CA is configured, the UE only has one RRC connection with the network At RRC connection establishment, one serving cell provides the NAS mobility information (e.g. TAI) / security input: 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 (“helper cells/resources”) 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

32

Release-10: Carrier Aggregation(2)

E-UTRAN: Behond Release-8

PCell ¡ SCell ¡ SCell ¡ PCC SCC SCC

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Impact on L2 Architecture (nwk side)

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HARQ HARQ DL-SCH

• n 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

• n CCx

HARQ HARQ DL-SCH

• n 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. HARQ retransmissions shall be sent on the same CC as the CC

• f the original transmission

Separate TrCH per CC

Release-10: Carrier Aggregation(3)

E-UTRAN: Beyond Release-8

Mobile and Wireless; 23-10-2014

Release 11 (specifications completed March 2013)

Coordinate MultiPoint Transmission (COMP)

Release-12 (specifications to be completed March 2015)

LTE Device to Device Proximity Services

UEs can “discover” each other directly, when in network coverage UEs can “communicate” directly, when in and out of coverage (Public Safety) Also heavy CN impact

Dual Connectivity for LTE

One UE served by a “Main eNB” and “Secondary eNB”

Release-13 (work started)

Licensed-Assisted Access using LTE

CA with LTE in licensed + unlicensed spectrum

Physical layer enhancements for Low cost Machine Type Communication

Internet Of Things

Full dimension MIMO

34

E-UTRAN: Beyond Release-8

Example features in later releases

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III Enhanced Packet Core (EPC)

• Core Network Architecture
• Example Signalling Sequences
• PS CN evolution
• Interworking with non-3GPP accesses

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BSS

A Iu

HLR IP UTRAN PSTN/ ISDN GSN PS-domain MSC CS-domain

Iu Gb

CN Two CN domains:

• Circuit-Switched (CS) domain
• Packet-Switched (PS) domain

Uu Gi

GSM/UMTS network architecture

CN Architecture

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LTE EPC architecture

Source: TS23.401

Two User Plane Gateways (which can be merged):

Serving SAE GW

Local mobility Anchor for inter-eNB handover / inter-3GPP mobility

PDN SAE GW

Policy enforcement, per user packet filtering, charging Mobility anchor for non-3GPP mobility

One Control Plane Node

Mobility Management Entity (MME)

NAS control protocol between UE and MME (24.301)

• Mobility in IDLE mode
• EPS bearer management

Only 1 CN domain

GSM/UMTS: CS & PS LTE: Only PS Resulting in large simplication of procedures

UMTS UE always registered in Location Area (CS: MSC) and Routing Area (PS: SGSN) LTE UE only registered in Tracking Area (MME) CN Architecture

eNB PHY UE PHY MAC RLC MAC MME RLC NAS NAS RRC RRC PDCP PDCP

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RRC CONNECTION SETUP (CCCH)

UE E-UTRAN RRC CONNECTION REQUEST RRC CONNECTION SETUP RRC CONNECTION SETUP COMPLETE

E-UTRAN UE

RRC CONNECTION SETUP COMPLETE (DCCH) RRC CONNECTION REQUEST (CCCH) RRC Connection (C-plane)

UE E-UTRAN CN E-Radio Access Bearer Service Radio Bearer Service

E-RAB (U-plane) RB SRB

E-RAB

E-UTRAN Radio Access Bearer (E-RAB) Signalling Radio Bearer (SRB) Radio Bearer (RB)

RRC Connection establishment (AS)

Signalling Sequence Example: Connection Establishment

MME GW

INITIAL UE MSG S1-connection (C-plane)

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• 3. Create Bearer Request

MME Serving GW PDN GW PCRF

• 4. Bearer Setup Request

(NAS: Activate dedicated EPS bearer context request)

• 5. RRC Connection Reconfiguration

(NAS: Activate dedicated EPS bearer context request)

• 2. Create Bearer Request
• 6. RRC Connection Reconfiguration
• 7. Bearer Setup Response
• 10. Create Bearer Response

eNodeB UE (A) (B)

• 1. Session Modification

¡

• 12. Session Modification

¡

• 11. Create Bearer Response
• 8. UL Direct Transfer

(NAS: Activate default EPS bearer context accept)

• 9. Uplink NAS transport

(NAS: Activate default EPS bearer context accept)

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Dedicated Bearer Activation Procedure (NAS)

RB GPRS Tunnel GPRS Tunnel

IP-packets

IP Network

Signalling Sequence Example: Bearer Establishment

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PS-CN evolution

Normally uses dynamic IP addresses, only allocated to the UE when the UE establishes a PDP context;

Results in “pull-based” approach (dial-up approach); Very limited support for “push-based” services;

No standardised way for establishing sessions with other users

How to establish a video session, audio session with somebody on the Internet ? E.g. user wants to start chess game with peer user ? What signalling to use ?

Network convergence (removal of CS CN) Operator could leave choice to user:

Multitude of different solutions Less control Charging might be complicated

Need a protocol that is suitable for session establishment, modification and release, and that addresses the “pull limitation”.

PS evolution: IMS

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IP Multimedia Core Network Subsystem (IMS)

IP Multimedia Core Network Subsystem (IMS) is part of 3GPP Rel-5 Uses SIP (Session Initiation Protocol) as the protocol for session management SIP is standardised by IETF (RFC-3261) Main SIP functionality:

Setup, Modify and Tear down of multi-media Sessions Request and deliver presence information Instant messaging Works with URI’s “Uniform Resource Indicators”, which might be location independent

User related URI, also called AOR “Address of Record”

This you store in your address book

Device URI

Associated to a user for a shorter period of time

PS evolution: IMS

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SIP: Simple signalling example (no proxy)

Irma Erik

INVITE 180 Ringing 200 OK ACK Media Session BYE 200 OK

• Peer-to-Peer
• Text based
• Transport can use UDP, TCP or SCTP
• Without Proxy, IP address of peer user needs to be known

INVITE sip:erik@idols.nl SIP/2.0 Via: SIP/2.0/UDP server1.kpn.nl:5060; branch=d987fsdjhff Max-Forwards: 70 To: Erik <sip: Erik@idols.nl> From: Irma <sip: irma@kpn.nl>; tag=98774 Call-ID: 123456789”server1.kpn.nl Cseq: 1 INVITE Subject: When do we meet ? Contact: irma@knp.nl Content-Type: application/SDP Content-Length: 158 SDP content………

PS evolution: IMS

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SIP: Signalling example (with proxy)

Irma Erik

INVITE 180 Ringing 200 OK ACK Media Session BYE 200 OK

• Irma does not know where Erik is:
• DNS lookup on Erik’s URI domain name (idols.nl)
• DNS lookup returns IP address of the proxy server
• INVITE is sent to this address
• Proxy server:
• looks up the SIP URI in the request URI “sip: erik@idols.nl” in its DB, and determines the current IP address

where Erik can be reached;

• Forwards INVITE to that address
• If Erik is temporarily reachable via another node, he could sent a REGISTER message

to a REGISTRAR server, to inform it about the new node. This information can then be used by a SIP Proxy.

SIP Proxy

180 Ringing 200 OK

PS evolution: IMS

• User related URI Irma (from)
• User related URI Erik (to)
• Device URI Irma (contact)
• User related URI Irma (from)
• User related URI Erik (to)
• Device URI Erik (contact)

INVITE

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IMS architecture (1)

• P-CSCF (Proxy-Call Session Control Function)
• is the first contact point within the IMS for the subscriber.
• interfaces to PCRF for RAN/EPC resource control
• I-CSCF (Interrogating-CSCF)
• is the contact point within an operator's network for all connections destined to a

subscriber of that network operator, or a roaming subscriber currently located within that network operator's service area.

• S-CSCF (Serving-CSCF)
• performs the session control services for the subscriber. It also acts as a SIP Registrar.

• d

Source: RFC 3574

GPRS/UMTS Access IP Multimedia CN Subsystem P-CSCF I-CSCF S-CSCF SIP signalling User Traffic

PS evolution: IMS

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IMS architecture (2): Routing of INVITE

Source: Luis Angel Galindo PS evolution: IMS

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IMS Outgoing call example: SIP signalling [1]

PS evolution: IMS

Caller Called Visited P-CSCF Home S-CSCF Home P-CSCF INVITE INVITE INVITE INVITE 100 Trying 100 Trying 100 Trying 183 183 183 183

SIP request messages ACK: Acknowledge final responses to INVITE requests INVITE: Establish session PRACK: Ack for reliable transported provisional response UPDATE: Update session without changing State of dialog SIP Response messages 100 Trying: hop-by-hop progress indication 180: Alerting is taking place 183: End-to-end progess (e.g. establi sh one-way media for ring tone, busy tone or announcement “you call is being diverted”)) 200 OK: 1) Accept session invitation 2) General confirmation stopping retransmissions

PRACK PRACK PRACK PRACK 200 OK 200 OK 200 OK 200 OK UPDATE UPDATE UPDATE UPDATE 200 OK 200 OK 200 OK 200 OK 200 OK 200 OK 200 OK 200 OK 180 180 180 180 ACK ACK ACK ACK Media Session

Mobile and Wireless; 23-10-2014 47

IMS Outgoing call example: Overview originating side [2]

PS evolution: IMS

P-GW MME E-UTRAN UE

1) RRC Connection establishment 2) Attach (establish MM context) 3) Activate Default EPS bearer context

• UE IP address
• P-CSCF IP address

P-CSCF I-CSCF S-CSCF

4) Service Registration (SIP Register) 5) INVITE 6) SDP negotiation 7) Activated Dedicated EPS bearer context 8) Session Confirmation (200OK & ACK) 9) Session in Progress

Mobile and Wireless; 23-10-2014 48

Signalling and Traffic paths

PS evolution: IMS Source: award solutions

Mobile and Wireless; 23-10-2014 49

Logical architecture (non roaming)

Long Term Evolution Source: TS23.401

Mobile and Wireless; 23-10-2014 50

Inter-working with non-3GPP accesses

• SAE supports both host-based and network-based mobility management solutions
• Dual-Stack MIPv6 (host-based)
• Proxy MIPv6 and MIPv4 in Foreign Agent mode (network-based)
• PDN GW works as MIP/PMIP Home Agent
• When connected to a 3GPP access the UE can be assumed to be at home in MIP sense
• Mobility within 3GPP accesses (E-UTRAN, UTRAN and GERAN) is managed in a

network-based fashion using 3GPP-specific protocols

• SAE distinguishes between “trusted” and “untrusted” non 3GPP accesses
• It is up to the operator to decide if a non 3GPP access is trusted or untrusted
• The decision is not based just on the access network technology but may depend

also on business considerations

• Interworking with an untrusted access is performed via an evolved PDG (ePDG)

the ePDG is similar to a VPN concentrator the UE has to establish an IPsec tunnel with the ePDG to access operator’s services the ePDG may implement IP mobility protocols (e.g. PMIPv6)

• Interworking with a trusted access is performed using a more lightweight procedure
• The UE does not need to establish an IPsec tunnel with the ePDG in advance
• MIP or PMIP protocols can be used directly between the non 3GPP access network and

the EPC Long Term Evolution; non-3GPP accesses

Mobile and Wireless; 23-10-2014 51

Inter-working with non-3GPP accesses

Long Term Evolution; non-3GPP accesses

Mobile and Wireless; 23-10-2014 52

Example: Handover to trusted non-3GPP access (1)

Source: IST Mobile Wireless Long Term Evolution; non-3GPP accesses

HA: Home Agent (MIP/PMIP) MAG: Mobility Access Gateway (PMIP) AGW: Access GateWay ePDG: evolved Packet Data Gateway

Mobile and Wireless; 23-10-2014 53

Source: IST Mobile Wireless Long Term Evolution; non-3GPP accesses

Example: Handover to trusted non-3GPP access (2)

Mobile and Wireless; 23-10-2014 54

Long Term Evolution; non-3GPP accesses

Example: Handover to trusted non-3GPP access (3)

Mobile and Wireless; 23-10-2014

IV Summary

Mobile and Wireless; 23-10-2014 56

Summary

3rd Generation Partnership Project (3GPP)

• Long History of Successful standardisation
• GSM, UMTS, UMTS-HSDPA/HSUPA, LTE, LTE-A (CA),…..

Access Stratum <-> Non Access Stratum (AS ó NAS)

• Required to introduce LTE in RAN/CN network architecture

E-UTRAN

• LTE RAN brings a new flat RAN architecture with high throughput/capacity

PS CN evolution

• Enhanced Packet Core (EPC) / IP Multimedia Core Network System (IMS)

Interesting new topics

• Dual-Connectivity (Rel-12)
• Direct Discovery/Direct Communication (Rel-12)
• Licensed-Assisted Access (Rel-13)
• Internet of Things IoT (Rel-12/13)
• …..

Summary

Mobile and Wireless; 23-10-2014

V Backup Slides

Mobile and Wireless; 23-10-2014 58

UMTS<-> LTE comparison: Radio technology

HSDPA/E-DCH 3GPP LTE Rel-8 Radio Technology W-CDMA OFDM

(better suited for higher BW)

Peak Data Rates (DL/UL) Lower Spectrum efficiency 100Mbps/50Mbps in 20Mhz Flexible Bandwidth 5Mhz / N * 5Mhz 1.25 , …, 20Mhz / N * (1.25 , …, 20Mhz) User plane latency ± 50ms ± 10ms

Long Term Evolution