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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 4
3rd Generation Partnership Project (3GPP)
3GPP structure
(Japan) (Japan)
(China) (Korea)
(USA) (Europe)
www.3gpp.org
Mobile and Wireless; 23-10-2014 5
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 ?
Mobile and Wireless; 23-10-2014 7
Overall network architecture (non roaming)
LTE: Overall architecture
Source: TS23.401
Mobile and Wireless; 23-10-2014 8
Uu (radio) interface: Terminal to Network
UE Network / “Infrastructure side” Uu
LTE: Basic principle
Mobile and Wireless; 23-10-2014 9
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
Mobile and Wireless; 23-10-2014
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 other by means of the X2 interface ! can be a logical connection via CN elements
! eNBs are also connected to the Evolved Packet Core (EPC) ! eNBs are connected to the Mobility
Management Entity (MME) via the S1-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
Mobile and Wireless; 23-10-2014
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)
12
internet
eNB
RB Control
Connection Mobility Cont.
eNB MeasurementConfiguration & Provision
Dynamic Resource Allocation (Scheduler)
PDCP
PHY
MME
S-GW
S1MAC
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
Mobile and Wireless; 23-10-2014
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
PDCPPDCP
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
Mobile and Wireless; 23-10-2014 14
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
PD
CP
RLC
M
AC
P
HY
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)
Mobile and Wireless; 23-10-2014
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
Mobile and Wireless; 23-10-2014
! 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
Mobile and Wireless; 23-10-2014 17
Core Network
S1
Uu (the “radio interface”) C h a n n e l
4s
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UE 1, Connected mode
eNB
Cells
C h a n n e l
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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)
Mobile and Wireless; 23-10-2014
! 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
18
P-GWS-GW PeerEntity
UE eNB
EPS Bearer
Radio Bearer S1 Bearer
End-to-end Service
External Bearer
Radio S5/S8
Internet
S1
E-UTRAN EPC
Gi
E-RAB S5/S8 Bearer
End-to-End QOS
E-UTRAN QOS
Mobile and Wireless; 23-10-2014
! 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] 19
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
Mobile and Wireless; 23-10-2014
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
20
E-UTRAN QOS
Mobile and Wireless; 23-10-2014 21
Retransmissions: comparison to GSM/ UMTS
eNB
PHY
UE
PHY
MAC
RLC
MAC
PDCPPDCP
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
or 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
or 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
22
E-UTRAN QOS
QOS: Latency
Mobile and Wireless; 23-10-2014
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)
23
E-UTRAN Mobility
Mobile and Wireless; 23-10-2014 24
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
Mobile and Wireless; 23-10-2014
! 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
Mobile and Wireless; 23-10-2014 26
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
Mobile and Wireless; 23-10-2014 27
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
Mobile and Wireless; 23-10-2014 28
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
Mobile and Wireless; 23-10-2014 29
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 ! once 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
31
LTE-Advanced maximum bandwidth
Carrier 1 Carrier 4 Carrier 5Carrier 3Carrier 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
Mobile and Wireless; 23-10-2014
! Impact on L2 Architecture (nwk side)
33
HARQ HARQ
DL-SCHon 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
PCHBCH MCH
RLC
PDCPROHC ROHC...
Segm.ARQ etc...
Transport Channels
Segm.ARQ etc
Security Security...
ROHC ROHC...
Segm.ARQ etc...
Segm. Segm.
...
...
...
DL-SCHon CCx
HARQ HARQ
DL-SCHon 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
of 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
Mobile and Wireless; 23-10-2014
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 36
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
Mobile and Wireless; 23-10-2014 37
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
Mobile and Wireless; 23-10-2014 38
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-U
TRA
N C
N
E-R
adio
Acc
ess
Bea
rer S
ervi
ce
Rad
io B
eare
r Ser
vice
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)
Mobile and Wireless; 23-10-2014
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)
39
Dedicated Bearer Activation Procedure (NAS)
RB GPRS Tunnel
GPRS Tunnel IP-packets
IP Network
Signalling Sequence Example: Bearer Establishment
Mobile and Wireless; 23-10-2014 40
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
Mobile and Wireless; 23-10-2014 41
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
Mobile and Wireless; 23-10-2014 42
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
Mobile and Wireless; 23-10-2014 43
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
Mobile and Wireless; 23-10-2014 44
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.
C h a n n e l
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lö
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Source: RFC 3574
GPRS/UMTS Access IP Multimedia CN Subsystem
P-CSCF I-CSCF
S-CSCF SIP signalling
User Traffic
PS evolution: IMS
Mobile and Wireless; 23-10-2014 45
IMS architecture (2): Routing of INVITE
Source: Luis Angel Galindo
PS evolution: IMS
Mobile and Wireless; 23-10-2014 46
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. establish 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 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 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
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