3GPP Telecommunication Systems Long Term Evolution (LTE) Gert-Jan van Lieshout Samsung Electronics Research Institute Deventer, The Netherlands
[email protected]
2012-06-05 Mobile and Wireless; 23-10-2014
Outline
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] Mobile and Wireless; 23-10-2014
2
I Introduction
Mobile and Wireless; 23-10-2014
3GPP structure
3rd Generation Partnership Project (3GPP)
(Europe)
(USA) (China)
(Japan)
(Korea) (Japan)
www. 3gpp.org
Mobile and Wireless; 23-10-2014
4
Why LTE ?
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) Mobile and Wireless; 23-10-2014
5
Why LTE ?
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: ! 23.402:
Mobile and Wireless; 23-10-2014
GPRS enhancements for E-UTRAN Architecture enhancements for non-3GPP accesses
6
LTE: Overall architecture
Overall network architecture (non roaming)
Source: TS23.401 Mobile and Wireless; 23-10-2014
7
LTE: Basic principle
Uu (radio) interface: Terminal to Network
UE
Uu
Mobile and Wireless; 23-10-2014
Network / “Infrastructure side”
8
LTE: Basic principle
S1 interface: Separates RAN from CN
Non-Access Stratum (NAS) functionality - no radio specific functionality
Access Stratum (AS), Radio Network functionality - all radio specific functionality - no user service specific functionality
UE
E-UTRAN
Uu
Mobile and Wireless; 23-10-2014
S1
CN
9
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 Architecture ! E-UTRAN consists of eNBs ! flat architecture (no RNC or BSC as in UTRAN and GERAN) for reduced latency and delays
S1
Mobile and Wireless; 23-10-2014
S1
X2 eNB
eNB X2
! 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
S1
! eNBs are also connected to the Evolved Packet Core (EPC)
MME / S-GW
S1
! can be a logical connection via CN elements
MME / S-GW
E-UTRAN
X2
! eNBs are interconnected with each other by means of the X2 interface
eNB
Uu
11
E-UTRAN architecture
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 of paging messages (originated from the MME); ! Scheduling and transmission of broadcast information (originated from the MME or O&M) Mobile and Wireless; 23-10-2014
eNB Inter Cell RRM RB Control Connection Mobility Cont.
MME
Radio Admission Control NAS Security eNB Measurement Configuration & Provision
Idle State Mobility Handling
Dynamic Resource Allocation (Scheduler)
EPS Bearer Control RRC PDCP
S-GW
P-GW
RLC Mobility Anchoring
MAC
UE IP address allocation
S1 PHY
Packet Filtering internet
E-UTRAN
EPC
12
E-UTRAN protocol stack: User Plane UE
User Plane protocol stack (1)
eNB PDCP
PDCP
RLC
RLC
MAC
MAC
PHY
PHY
! 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
Radio Bearers
! RLC (Radio Link Control) – 36.322 ! reliability increase through retransmissions ! segmentation and concatenation of SDUs for the same radio bearer ! in-sequence delivery
ROHC
ROHC
Security
Security
PDCP
RLC
Segm. ARQ etc
...
Segm. ARQ etc
! MAC (Media Access Control) – 36.321 ! ! ! !
multiplexing/demultiplexing of RLC PDUs scheduling information reporting error correction through HARQ logical channel prioritisation
Logical Channels Scheduling / Priority Handling
MAC
Multiplexing
HARQ Transport Channels UL-SCH
Mobile and Wireless; 23-10-2014
13
E-UTRAN protocol stack: User Plane
User Plane protocol stack (2) IP PDU#1 Radio Bearer 1 Header
IP PDU#2 Radio Bearer 1
IP Payload
Header
PDCP
H SN
PDCP SDU
SN
RLC MAC
MAC SDU
IP Payload
H PDCP SDU
SN
PDCP SDU
RLC SDU
H RLC PDU
PHY
Header
RLC SDU
H
Mobile and Wireless; 23-10-2014
IP Payload
H
RLC SDU
H
IP PDU#2 Radio Bearer 2
H RLC PDU
MAC SDU
Multiplexing Transport Block
CRC
14
E-UTRAN protocol stack: Control Plane
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 UE
eNB
MME
NAS
Mobile and Wireless; 23-10-2014
NAS
RRC
RRC
PDCP
PDCP
RLC
RLC
MAC
MAC
PHY
PHY
15
E-UTRAN protocol stack: Control Plane
Control Plane protocol stack (2) ! 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
Mobile and Wireless; 23-10-2014
16
E-UTRAN Mobility
Control Plane protocol stack (3) UE1 -> S1-Conn. Y
UE2 -> TA 403
Core Network
S1
S1-connection Y
S1 TA 403 (Tracking Area)
eNB
UE1 -> Cell X
= Data record
RRC-connection X Cells
TA 403 (Tracking Area) Uu (the “radio interface”)
UE 1, Connected mode
C
C
h
4
a
n
e
a s w
s a q s a q
h
4
a
n
s a q n
s a q
k l e
a s w a s w
d d
k l e k l e
j f r
d d d d
f l ö t
r
j f r j f r
s a q
f
l ö t
r f r
ö a i
l ö t
d u
ö a i ö a i
l a ö
o d u
l
a ö
o d u
l o
a ö
d l d
k k k k k k
k k k
e
a s w
l
k l e
a s w
d d
k l e k l e
j f r
d d d d
f
s d l
f
f r f
s d l s d l
f
.
j
c f
.
j
ö a i
l ö t
l ö t
d u
ö a i
ö a i
l
a ö
o
d u
l
a ö
o
d u
l o
j
c
l ö t
UE 2, Idle mode r
j f r j f r
r
d l d d l d
n
a s w
s a q
l
a ö
d l d
d l d
d l d
k k k
k k k
k k k
s d l
f
j
c
s d l s d l
f
.
j
c f
.
j c .
c .
Mobile and Wireless; 23-10-2014
17
E-UTRAN QOS
End-to-End QOS E-UTRAN
UE
EPC
eNB
S-GW
Internet
P-GW
Peer Entity
End-to-end Service EPS Bearer
E-RAB Radio Bearer
Radio
External Bearer
S5/S8 Bearer S1 Bearer
S1
S5/S8
Gi
! 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
Mobile and Wireless; 23-10-2014
18
E-UTRAN QOS
Radio Bearer QOS ! RB establishment based on QoS parameters from MME
Compare UMTS:
S
to A t ! QoS Class Iden-fier (QCI) per bearer: s e u scalar value which iden@fies a par@cular NAS req 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
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
! 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]
Mobile and Wireless; 23-10-2014
19
E-UTRAN QOS
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 Mobile and Wireless; 23-10-2014
20
E-UTRAN QOS
Retransmissions: comparison to GSM/ UMTS GPRS Appl IP
GTP: GPRS Tunneling Protocol SNDCP GTP-U
SNDCP LLC
LLC
RLC
RLC
MAC
MAC
GSM RF
MT
GSM RF Um
GTP-U
UDP
UDP
IP
IP
BSSGP
BSSGP
E.g. L2TP or IP tunnel IP
L2
L2
L2
L2
L2
L2
L2
L1
L1
L1
L1
L1
L1
L1
Abis
BTS
Gb
BSS
Gn
SGSN
GGSN
SNDCP: SubNetwork Dependent Convergence Protocol a.o.: header/payload compression
Gi
LLC: Logical Link Control RLC (GPRS): Radio Link Control
UMTS Appl IP PDCP
LTE
PDCP
GTP-U
RLC
RLC
UDP
MAC
MAC
MAC-hs UMTS MAC-e RF UMTS RF UE
UE
MAC-hs FP UMTS MAC-e ATM RF UMTS L1 RF Node-B
REL-5/6ATM
Uu
GTP-U
GTP-U
UDP
UDP
IP
IP
IP
IP
E.g. L2TP or IP tunnel IP
ATM
ATM
L2
L2
L2
L1
L1
L1
L1
REL-99 UDP
FP L1
Iub
GTP-U
SRNC
L1 Iu
SGSN
Gn
GGSN
PDCP: Packet Data Convergence Protocol a.o.: header compression RLC (UMTS): Radio Link Control
Gi
eNB PDCP
PDCP
RLC
RLC
MAC
MAC
PHY
PHY
Mobile and Wireless; 23-10-2014
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 21
E-UTRAN QOS
QOS: 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
Mobile and Wireless; 23-10-2014
22
E-UTRAN Mobility
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) Mobile and Wireless; 23-10-2014
23
E-UTRAN Mobility: Handover
Mobility: X2-Handover(1) ! Source eNB configures UE measurements
MME S-GW
S1-MME
Source eNB
measurements
! target frequency and triggers
! Source eNB receives UE measurement reports
S1-U
X2
Target eNB
! HO decision is made and target eNB is selected by the source eNB
UE control plane user plane user data control plane signalling
Mobile and Wireless; 23-10-2014
24
E-UTRAN Mobility: Handover
Mobility: X2-Handover(2) ! HO request sent from source eNB to target eNB
MME S-GW
S1-MME
Source eNB
! Target eNB performs admission control and accepts the HO request
S1-U
HO request HO Request Ack
Target eNB
! HO Ack sent to source eNB from target eNB
measurements
control plane user plane user data control plane signalling
Mobile and Wireless; 23-10-2014
UE
25
E-UTRAN Mobility: Handover
Mobility: X2-Handover(3) ! HO command is sent to the UE
MME
! RRCConnec'onReconfigura'on message including the mobilityControlInfo
S-GW
S1-MME
Source eNB
S1-U
X2
! Data forwarding ini@ated towards the target eNB Target eNB
HO command
control plane user plane user data control plane signalling
Mobile and Wireless; 23-10-2014
UE
26
E-UTRAN Mobility: Handover
Mobility: X2-Handover(3) ! UE accesses the target eNB and confirms the HO
MME S-GW
S1-MME
Source eNB
! RACH procedure is ini@ated ! RRCConnec'onReconfigura'onComplete is sent
S1-U
X2
Target eNB HO confirm
control plane user plane user data control plane signalling
Mobile and Wireless; 23-10-2014
UE
27
E-UTRAN Mobility: Handover
Mobility: X2-Handover(4) MME S-GW
! 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 Source eNB
control plane user plane user data control plane signalling
Mobile and Wireless; 23-10-2014
Target eNB
X2
! MME → eNB : path switch request ACK
! Target eNB no@fies the source eNB that UE resources can be released
UE
28
E-UTRAN Mobility: Handover
Mobility: X2-Handover(5) ! Path is switched
MME S-GW
! Source eNB finishes forwarding packets S1-MME
Source eNB
control plane user plane user data control plane signalling
Mobile and Wireless; 23-10-2014
! once completed UE context can be cleared and resources freed
S1-U
Target eNB
X2
! HO is completed
UE
29
E-UTRAN: Beyond Release-8
Release-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
! 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] Mobile and Wireless; 23-10-2014
30
E-UTRAN: Beyond Release-8
Release-10: Carrier Aggregation(1) ! 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 LTE-Advanced maximum bandwidth
Rel’8 BW
Rel’8 BW
Rel’8 BW
Rel’8 BW
Rel’8 BW
Carrier 1
Carrier 2
Carrier 3
Carrier 4
Carrier 5
! non-contiguous carriers can also be aggregated in DL for increased flexibility
Mobile and Wireless; 23-10-2014
31
E-UTRAN: Behond Release-8
Release-10: Carrier Aggregation(2) ! Basic Concept ! When CA is configured, the UE only has one RRC connection with the network
PCC
PCell
SCC
SCell
! At RRC connection establishment, one serving cell provides the NAS mobility information SCC (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)
SCell
! 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 Mobile and Wireless; 23-10-2014
32
E-UTRAN: Beyond Release-8
Release-10: Carrier Aggregation(3) ! Impact on L2 Architecture (nwk side) Radio Bearers ROHC
...
ROHC
RLC
ROHC
...
ROHC
Security
...
Security
Segm. ARQ etc
...
Segm. ARQ etc
...
PDCP Security
...
Security
Segm. ARQ etc
...
Segm. ARQ etc
...
There is one PDCP and RLC per Radio Bearer. Not visible from RLC on how many CCs the PHY layer transmission is conducted. Segm.
Segm.
CCCH BCCH PCCH MCCH
Logical Channels
Dynamic L2 packet scheduling MBMS Scheduling across multiple CCs supported
Unicast Scheduling / Priority Handling
MAC
Multiplexing UE1
HARQ
...
...
HARQ
Multiplexing
Multiplexing UEn
HARQ
...
MTCH
Independent HARQ per CC. HARQ retransmissions shall be sent on the same CC as the CC of the original transmission
HARQ
Transport Channels DL-SCH on CC1
Mobile and Wireless; 23-10-2014
DL-SCH on CCx
DL-SCH on CC1
BCH
PCH
MCH
Separate TrCH per CC
33
E-UTRAN: Beyond Release-8
Example features in later releases ! 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 Mobile and Wireless; 23-10-2014
34
III Enhanced Packet Core (EPC) • Core Network Architecture • Example Signalling Sequences • PS CN evolution • Interworking with non-3GPP accesses
Mobile and Wireless; 23-10-2014
CN Architecture
GSM/UMTS network architecture
BSS A
MSC CS-domain
PSTN/ ISDN
Gb
HLR Iu Uu
UTRAN Iu
GSN PS-domain
Gi
IP
CN Two CN domains: - Circuit-Switched (CS) domain - Packet-Switched (PS) domain Mobile and Wireless; 23-10-2014
36
CN Architecture
LTE EPC architecture ! 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
UE
eNB
MME
NAS
NAS
RRC
RRC
PDCP
PDCP
RLC
RLC
MAC
MAC
! GSM/UMTS: CS & PS ! LTE: Only PS ! Resulting in large simplication of procedures PHY
PHY
! UMTS UE always registered in Location Area (CS: MSC) and Routing Area (PS: SGSN) ! LTE UE only registered in Tracking Area (MME) Source: TS23.401
Mobile and Wireless; 23-10-2014
37
Signalling Sequence Example: Connection Establishment
RRC Connection establishment (AS) E-UTRAN
UE
RRC CONNECTION REQUEST RRC CONNECTION SETUP
CN
GW
MME
RRC CONNECTION SETUP COMPLETE
RRC Connection (C-plane)
E-Radio Access Bearer Service
INITIAL UE MSG
S1-connection (C-plane) E-RAB (U-plane)
E-UTRAN Radio Bearer Service
UE
E-UTRAN
E-RAB
SRB RRC CONNECTION SETUP (CCCH) RRC CONNECTION SETUP COMPLETE RRC CONNECTION (DCCH) REQUEST RB (CCCH)
UE
Mobile and Wireless; 23-10-2014
E-UTRAN Radio Access Bearer (E-RAB) Signalling Radio Bearer (SRB) Radio Bearer (RB) 38
Signalling Sequence Example: Bearer Establishment
Dedicated Bearer Activation Procedure (NAS) UE
eNodeB
MME
Serving GW
PDN GW
PCRF
1. Session Modification
(A)
2. Create Bearer Request 3. Create Bearer Request 4. Bearer Setup Request (NAS: Activate dedicated EPS bearer context request) 5. RRC Connection Reconfiguration (NAS: Activate dedicated EPS bearer context request) 6. RRC Connection Reconfiguration 7. Bearer Setup Response 8. UL Direct Transfer (NAS: Activate default EPS bearer context accept) 9. Uplink NAS transport (NAS: Activate default EPS bearer context accept) 10. Create Bearer Response 11. Create Bearer Response 12. Session Modification
(B)
RB
Mobile and Wireless; 23-10-2014
GPRS Tunnel
GPRS Tunnel
IP-packets
IP Network 39
PS evolution: IMS
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”.
Mobile and Wireless; 23-10-2014
40
PS evolution: IMS
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
Mobile and Wireless; 23-10-2014
41
PS evolution: IMS
SIP: Simple signalling example (no proxy) Irma
Erik INVITE 180 Ringing 200 OK ACK Media Session
INVITE sip:
[email protected] SIP/2.0 Via: SIP/2.0/UDP server1.kpn.nl:5060; branch=d987fsdjhff Max-Forwards: 70 To: Erik From: Irma ; tag=98774 Call-ID: 123456789”server1.kpn.nl Cseq: 1 INVITE Subject: When do we meet ? Contact:
[email protected] Content-Type: application/SDP Content-Length: 158 SDP content………
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
Mobile and Wireless; 23-10-2014
42
PS evolution: IMS
SIP: Signalling example (with proxy) Irma
SIP Proxy INVITE
- User related URI Irma (from) - User related URI Erik (to) - Device URI Irma (contact)
Erik INVITE 180 Ringing
180 Ringing
- User related URI Irma (from) - User related URI Erik (to) - Device URI Erik (contact)
200 OK
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
!
looks up the SIP URI in the request URI “sip:
[email protected]” in its DB, and determines the current IP address where Erik can be reached; Forwards INVITE to that address
Proxy server: !
!
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.
Mobile and Wireless; 23-10-2014
43
PS evolution: IMS
IMS architecture (1) S-CSCF SIP signalling C
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IP Multimedia CN Subsystem
! 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. Source: RFC 3574 Mobile and Wireless; 23-10-2014
44
PS evolution: IMS
IMS architecture (2): Routing of INVITE
Mobile and Wireless; 23-10-2014
Source: Luis Angel Galindo
45
PS evolution: IMS
IMS Outgoing call example: SIP signalling [1] Visited P-CSCF
Caller
Home S-CSCF
Home P-CSCF
Called
INVITE INVITE 100 Trying
100 Trying
INVITE
INVITE
100 Trying 183 183
INVITE: Establish session
183 183 PRACK
PRACK
PRACK
200 OK
PRACK 200 OK
200 OK 200 OK UPDATE
UPDATE
UPDATE
UPDATE 200 OK
ACK
200 OK: 1) Accept session invitation 2) General confirmation stopping retransmissions
180 200 OK
200 OK 200 OK ACK
180: Alerting is taking place
200 OK
180
180
ACK
UPDATE: Update session without changing State of dialog
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 180
PRACK: Ack for reliable transported provisional response
SIP Response messages 100 Trying: hop-by-hop progress indication
200 OK 200 OK
SIP request messages ACK: Acknowledge final responses to INVITE requests
ACK
Media Session
Mobile and Wireless; 23-10-2014
46
PS evolution: IMS
IMS Outgoing call example: Overview originating side [2] UE
E-UTRAN
MME
P-GW
P-CSCF
I-CSCF
S-CSCF
1) RRC Connection establishment 2) Attach (establish MM context) 3) Activate Default EPS bearer context - UE IP address - P-CSCF IP address 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
47
PS evolution: IMS
Signalling and Traffic paths
Source: award solutions Mobile and Wireless; 23-10-2014
48
Long Term Evolution
Logical architecture (non roaming)
Source: TS23.401 Mobile and Wireless; 23-10-2014
49
Long Term Evolution; non-3GPP accesses
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 Mobile and Wireless; 23-10-2014
50
Long Term Evolution; non-3GPP accesses
Inter-working with non-3GPP accesses
Mobile and Wireless; 23-10-2014
51
Long Term Evolution; non-3GPP accesses
Example: Handover to trusted non-3GPP access (1)
HA: MAG: AGW: ePDG:
Home Agent (MIP/PMIP) Mobility Access Gateway (PMIP) Access GateWay evolved Packet Data Gateway
Mobile and Wireless; 23-10-2014
Source: IST Mobile Wireless 52
Long Term Evolution; non-3GPP accesses
Example: Handover to trusted non-3GPP access (2)
Source: IST Mobile Wireless Mobile and Wireless; 23-10-2014
53
Long Term Evolution; non-3GPP accesses
Example: Handover to trusted non-3GPP access (3)
Mobile and Wireless; 23-10-2014
54
IV Summary
Mobile and Wireless; 23-10-2014
Summary
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) …..
Mobile and Wireless; 23-10-2014
56
V Backup Slides
Mobile and Wireless; 23-10-2014
Long Term Evolution
UMTS LTE comparison: Radio technology
Radio Technology
HSDPA/E-DCH
3GPP LTE Rel-8
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
Mobile and Wireless; 23-10-2014
58
