lte/sae market & technology overview - · pdf file2.5g cdma hscsd gprs imode is-95b cdma...
TRANSCRIPT
1
Zach Lovell
Agilent Technologies
LTE/SAE Technology Overview &
Challenges
Agenda
LTE Market Overview
LTE & EPC Technology Overview
LTE & EPC Challenges
Short Intro to Agilent in LTE
2
Not just slides! LTE UE from MWC Feb 2009
Wireless evolution: Five competing 3.9G systems
Incre
asi
ng
eff
icie
ncy,
ban
dw
idth
an
d d
ata
rate
s
2GIS-136TDMA
PDCGSMIS-95ACDMA
IS-95Bcdma
HSCSD iMode2.5G GPRSIS-95BCDMA
3GE-GPRSEDGE
IS-95CCDMA2000
W-CDMAFDD
W-CDMATDD
TD-SCDMALCR-TDD
3.5GHSUPA
FDD & TDD1xEV-DO
Release B1xEV-DO
Release A1xEV-DORelease 0
HSDPAFDD & TDD
3.9G3.9GLTE
E-UTRAEDGE
EvolutionHSPA+
802.16eMobile
WiMAXTM
UMBcf 802.20
802.11g
802.11b
802.11a
802.16dFixed
WiMAX TM
802.11n
802.11h
WiBRO
New OFDM Systems! New OFDM System!
3
LTE Activity 2008 2009 2010 2011 2012
UE Device AvailabilityLTE won’t work without devices
Proof of ConceptWill LTE work & deliver the expected performance
IOTAre the standards interpreted in the same way by all
Trials & FOA’sVendor Selection & Testing in near commercial conditions
Early Adopter DeploymentsFirst to market but limited number of deployment sites
Full Commercial DeploymentsBuilding into full coverage network coverage
LTE Market Development Timelines
Prototypes Trial Handsets Commercial Handsets
RF/eNB Focused
Data only
Whole end to end network incl. IMS
Multi-Vendor eUTRAN/EPC
VoiceData
LTE Adoption is Gaining Momentum
14 LTE networks in service by end 2010
31 LTE networks in service by end 2012
4
Agenda
LTE Market Overview
LTE & EPC Technology Overview
LTE & EPC Challenges
Short Intro to Agilent in LTE
LTE/SAE Overview – Introduced in 3GPP Release 8
• Uses Orthogonal Frequency Division Multiple Access (OFDMA) in the Downlink
• Single Carrier Frequency Division Multiple Access (SC-FDMA) in the Uplink
• The LTE radio migration may occur via software upgrades (e.g. soft radios)
The LTE protocol & network architecture is characterized by three requirements:
• Support for the PS domain only. There will be no circuit switched (CS) domain nodes.
• Traditional Voice services are delivered using VoIP served by the IMS
• Tight delay targets for small roundtrip delays
• 5 ms for bandwidths of 5 MHz and greater ; 10 ms for the bandwidths below 5 MHz
• Reduced cost of the system
• Achieved with all IP infrastructure and flattened network architecture
LTE challenges carriers to review deployment & operational procedures
Network Overview - 3GPP R8 – LTE/SAE
Evolved Packet Core Evolved UTRAN
S1-MME
MMEeNB
eNB
Uu
MME
S1-U
PDN-GW
X2
S5SGi
HSS
S6a
PCRFS7
S-GWS10
S11
MRF CSCF ASS1-MME
IMS & other
Operator IP
Services
5
OFDM / OFDMA• Transmission variable up to system bandwidth
• Symbol period is long - defined by subcarrier spacing and independent of system bandwidth
• Users separated by FDMA & TDMA on the subcarriers
• Equalization is easy due to signal on freq domain, and free of multipath up to the CP length
• Ideal for MIMO
• Vulnerable to narrowband distortion and interference
• OFDMA’s dynamic allocation enables better use of the channel for multiple low-rate users and for the avoidance of narrowband fading & interference.
CDMA/W-CDMA• All transmissions at full system bandwidth
• Symbol period is short – inverse of system BW
• Users separated by orthogonal spreading codes
• Equalization and multipath resistance is difficult above 5 MHz
• Needs significant computing power to support MIMO
• Spreading protects from narrowband distortion and interference
LTE Fundamentals - Physical Layer
OFDMA
LTE Fundamentals – Air Interface – UL SC-FDMA
SC-FDMA
Data symbols occupy N*15 kHz for
1/N SC-FDMA symbol periods
60 kHz Frequency
fc
V
CP
15 kHzFrequency
fc
V
CP
OFDMA
Data symbols occupy 15 kHz for
one OFDMA symbol period
• SC-FDMA combines single carrier methods with the frequency allocation flexibility & long symbol time of OFDMA
• While OFDMA transmits 1 symbol per subcarrier in parallel, SC-FDMA transmits symbols in series at N times the
rate and occupies the same bandwidth
• Supports larger bandwidths than OFDMA without the high Gaussian PAR
• Resistant to multi-path due to the constant nature of each subcarrier
6
MIMO creates multiple parallel channels between transmitter and receiver. MIMO is using time
and space to transmit data (space time coding).
MIMO is a family of techniques:
• Use multiple channels to send the same information stream to achieve diversity (transmit
diversity)
• Improve coverage
• Use multiple channels to send multiple information streams (spatial multiplexing)
• Increase throughput
The LTE Air Interface - LTE MIMO
Evolved 3GPP Network Architecture
Evolved Packet Core (EPC)
Serving NetworkGSM/GPRS/EDGE Radio Access Network (GERAN)
UMTS Terrestrial Radio Access Network (UTRAN)
Core & Services Network
CS Core (Voice)
SGSN
MGWMSC
VLR HLRSMS
PCRF
NodeB
RNC
BTS
BSC
PCU
Evolved UTRAN (E-UTRAN)
UE
MS
Uu
Abis
Iub
RNC
Iur
UE
X2
Uu eNB
eNB
PS Core (Data)
GSM-ACS
PS
GPRS-Gb
PS
CS
Iu-CS
Iu-PS
S11
SAE-GW
MME
S5
S4S3
S1-UEvolved Node B
Radio Network Subsystem
Base Station Subsystem
S6a
Gx
SGW
SS7/SIGTRAN
RX
SGi
WCDMA HSPA/HSPA+
GSMEDGEEvolved EDGE
Um
S1-C
S12
Gn InternetOperator’s IP
Services(E.g. IMS, PSS…)
P-GW
GGSN
HSS CSCFMRF /MGW
S10
7
Network Overview - LTE Functional Nodes
eNBeNodeB
Radio Resource Management
• Bearer & Admission control
• RF Measurement Reporting
Scheduling
• Dynamic resource allocation to UE’s
• Transmission of Pages & broadcast information
Network Access Security (PDCP)
• IP header compression
• Ciphering of user data stream
EPC Network Selection
• MME Selection at UE attachment
• User Plane routing to SAE-GW
Combines the functionality of the UMTS NodeB & RNC
Network Overview – EPC Functional Nodes
MMEMobility
Management Entity
EPC Access
• Attachment & Service Request
• Security & Authentication
Mobility
• MME Selection for Intra-LTE handovers
• SGSN Selection for 3GPP I-RAT Handover
UE Tracking and Reach-ability
• Tracking Area List Management (idle or active)
Bearer management
• Dedicated bearer establishment
• PDN GW & SAE-GW selection
Equivalent to the SGSN for the Control Plane
8
Network Overview – EPC Functional Nodes
S-GWSAE Gateway
Packet routing & forwarding
between EPC & eUTRAN
Local Mobility Anchor for Inter eNB handover
I-RAT Mobility Anchor Function
• 3GPP 2G/3G Handover
• Optimized Handover Procedures (e.g. in LTE-CDMA)
Lawful Interception
Equivalent to the SGSN for the User Plane
Network Overview – EPC Functional Nodes
P-GWPDN Gateway
UE IP address allocation
Policy enforcement
(QoS)
Charging support
Lawful Interception
Mobility Anchor between 3GPP & non-3GPP
access systems
Equivalent to the GGSN
9
Network Overview – Control Plane Protocols
UU S1-C S6a
Network Access Security – NAS Ciphering Network Access Security – PDCP Ciphering Network Domain Security – IPsec Encryption
** Both IPv4 & IPv6 supported
Network Overview – User Plane Protocols
UU S1-U SGi /Gm
Application Domain Security – IPSec AKA Network Access Security – PDCP Ciphering Network Domain Security – IPsec Encryption
* SCTP Recommended Transport in TS 29.229 ** Both IPv4 & IPv6 supported
S5/8 Cx
10
EPC Fundamentals – QoS Model
Today’s 3G Services use best effort QoS Class for all PS services
• An LTE user can have up to 24 bearers, each with its own QoS Class
• In the EPC, the QoS parameters are a function of guaranteed & non-guaranteed bit rates defined by 9 QCI labels.
QoS Class
Identifier
L2 Packet
Delay
Budget
L2 Packet
Loss RateExample Services
QCI=1 (GBR) 100 ms 10-2 Conversational Voice
QCI=2 (GBR) 150 ms 10-3 Conversational Video (Live Streaming)
QCI=3 (GBR) 50 ms 10-3 Real Time Gaming
QCI=4 (GBR) 300 ms 10-6 Non-Conversational Video (Buffered Streaming)
QCI=5 (non-GBR) 100 ms 10-6 IMS Signalling
QCI=6 (non-GBR) 300 ms 10-6
Video (Buffered Streaming)
TCP-based (e.g., www, e-mail, chat, ftp, p2p file
sharing, progressive video, etc.)
QCI=7 (non-GBR) 100 ms 10-3 Voice, Video (Live Streaming) Interactive Gaming
QCI=8 (non-GBR) 300 ms 10-6Video (Buffered Streaming)
TCP-based (e.g., www, e-mail, chat, ftp, etc.)QCI=9 (non-GBR) 300 ms 10-6
PDN -GWSGWeNBUE
EPC Fundamentals – QoS Model
RB-ID S1-TEIDUL-TFT RB-ID S1-TEID S5/S8-TEID S5/S8-TEI DL-TFT
UL Service Data Flows DL Service Data Flows
Application / Service Layer
GBR – Service BlockingReal Time
Non GBR – Service Dropping Non Real-Time
Page 20
TFT = Traffic Flow Template
Radio Bearer S1 Bearer S5 Bearer
11
21
• 2x2 MIMO
• HARQ; Round Robin
• Best effort user: fixed SNR (23 dB aprox), UDP transfer
• GBR user: GBR = 10 Mbps, variable SNR, HD video streaming
With decreasing SNR, GBR user maintains desired rate by taking resources from best effort user, until SNR too low to support GBR.
eNB Scheduler and QoS – An LSTI Illustration
Agenda
LTE Market Overview
LTE & EPC Technology Overview
LTE & EPC Challenges
Short Intro to Agilent in LTE
12
Downlink peak data rates (64QAM)
Antenna config SISO 2x2 MIMO 4x4 MIMO
Peak data rate Mbps 100 172.8 326.4
Uplink peak data rates (Single antenna)
Modulation QPSK 16 QAM 64 QAM
Peak data rate Mbps 50 57.6 86.4
eNB
UE1
UE2
UE3
UE4
UE5
Challenges – Adaptive Modulation and Coding
64 QAM
16 QAM
QPSK
Who will have What coverage Where?
64 QAM requires 10dB Carrier to Interference ratio (C/I)
How do you achieve that much isolation without adding more sites?
Evolved Packet Core
Challenges – Collapsed Architecture
eNB
Inter Cell RRM
RB Control
Connection Mobility Control
Radio Admission Control
eNB Measurement
Configuration & Provisioning
Dynamic Resource
Allocation (Scheduler)
RRC
PDCP
RLC
MAC
PHY
Serving Gateway
Mobility
Anchoring
MME
NAS Security
Idle State Mobility Handling
SAE Bearer Control
Internet
S1
E-UTRAN
PDN Gateway
UE IP Address
allocation
Packet Filtering
How do you do RF Performance
Engineering & Optimization, when
all these functions are closed within
the eNB?
What is the
Cost?
13
Challenges – Monitoring Points & Data Sources
Different Data Sources yield different information
and
different levels of cost effectiveness.
Data Sources
Evolved Packet Core (EPC)
PCRF
PDNEvolved UTRAN (E-UTRAN)
UE
Uu
eNB
S11
S-GW
MME
P-GW
S5
S1-U
Evolved Node B
HSS
S6a
Gx
Internet
RXSGi
CSCF MRF
S1-C
UE Device
E.g. Drive Test
Passive Air
Interface Probe
Network Element
Internal Debug
eNB, MME etc.
Network Element
Internal Monitor
CPRI/OBSAI
Interface
Monitoring
Sx, X2, S5/S8 …
P-GW(PCEF)X2
Challenges – How will Voice be Delivered??
Two Leading Proposals for CS Services Delivery over EPS Access in R8
• CS Fallback
• Voice over LTE Generic Access (VoLGA)
CS Fallback
• Currently selected by 3GPP as a Part of Release 8
• Connected to E-UTRAN uses GERAN or UTRAN to Establish CS & SMS Services
• Co-Exist with IMS-based Services in Same Operator’s Network
• CS Service over IMS takes precedence over CS Fallback
VoLGA – Voice over LTE via Generic Access
• Connected and Uses EPS to Establish One or More CS Services, via Legacy CN Infrastructure
• Does Not Require E-UTRAN Coverage Overlap with GERAN or UTRAN Coverage
• Co-Exist with IMS-based Services and CS Fallback in Same Operator’s Network
• Simultaneous Use of VoLGA & IMS Services Possible, while Not So with CS Fallback
Conclusions of Feasibility Studies
• Overlapping Coverage between LTE/EPS and Legacy CS Systems:
• CS Fallback Approach Preferred – but significant issues exist
• Non-Overlapping Coverage between LTE/EPS and Legacy CS Systems:
• VoLGA Approach Preferred
14
Challenges – CS Fallback Architecture
UE E-UTRAN MMELTE-Uu S1-MME
GERAN
UTRAN
Um
Uu
SGSN
MSC
Server
SGs
Gs
A
Iu-cs
Gb
Iu-ps
S3
• Part of Release 8 – TS 23.272
• Forces user off LTE to make a call
• MSC server & SGSN upgrades – New SGs interface
Challenges – CS Fallback E-UTRAN Page, No PS HO
9a. Connection Reject
1a. CS Paging 1a. CS Paging
If the MSC is changed
SGSN
10. CS Call Establishment procedure
6. Location Area Update or Combined RA/LA Update
5. S1 UE Context Release
BSS/RNS
4. S1-AP: S1 UE Context Release Request
UE/MS MME MSC
3a. NACC, 3b. Signalling connection release
eNodeB
2. Optional Measurement Report
9. Paging Response
9b. Location Area Update or Combined RA/LA Update
9a. Signalling Connection Release
S-GW
1b. Extended Service Request
1d. S1-AP message with CS Fallback indicator
1c. CS Paging Reject
7a. Suspend (see TS 23.060)
8. Update bearer(s)
7b. Suspend Request / Response
Potential impact on call setup times (1.5 sec)
User may not be able to maintain LTE data session while in call
Extra
delay
before
starting
the call
setup
procedure
15
• Z1: Reference Point between UE and IWF (VANC)
– Similar to GAN Up Interface between MS and GANC
• Z2: Reference Point between MME and IWF (VANC)
– Similar to Sv interface for Single Radio Voice Call Continuity (SRVCC)
– per TS 23.216
Challenges – VoLGA 3GPP Reference Architecture
UE
BTS/
BSC
NodeB
/RNC
eNodeBS-GW/
PDN-GWS1-UP
IWF
(VANC)SGi
MSC/
VLRA
Iu/A
HSSD
Z1
PCRFRx
Gx
Iu
MMEZ2
S1-MME
The PS challenge still exists between the UE & the IWF
Challenges - KPIs are more than just technical data
Determines Network Optimization Target, Priorities and KPI Definitions
Best Mixed Voice & Data for
everybody
Best High Speed Data for selected
users
Best Coverage What about
Real World Conditions
Handset
profiles
Application
mix
Cell
Geometry
How will CS
services be
delivered?
Expected
Cell
Interference
Usage
Patterns
Business Objectives There are other considerations
16
Monitoring and KPIs – 3GPP Definitions
3GPP defines 5 basic KPI types
Accessibility: Can a connection to the network be obtained
• Provides no QoS information
Retainability: Can a connection to the network be maintained
• Often generalized as the drop call ratio
Integrity: What is the quality of the connection
• Since LTE supports only the PS domain, these measurements revolve around IP throughput and latency.
Mobility: Impact of mobility on the end user
• Measures the success of hand over procedures
Availability: Is the network available to be accessed
• Measured at the cell level
Challenges - KPI Definition
The Accessibility KPI as an example.
• Can be measured on the S1 interface by analyzing the ERAB establishment procedures.
• This is not enough by itself!!!
• In many cases, a service will require multiple radio bearers.
– E.g. Default bearer for signaling & dedicated bearer for media streaming
• The actual service accessibility needs to combine the success rates for both the default and the dedicated radio bearers
• The LTE accessibility KPI focuses on the E-UTRAN itself;
• This is insufficient to measure the accessibility of a specific service end-to-end
– Take a voice call establishment as an example, once a UE has obtained a connection to the access network it must now be able to reach the specific application server (AS) within the IMS.
• The Voice AS (or CSCF) can generally be calculated as:
KPI Definition is not always straight forward !!!
What KPI’s can be computed depends on particular interface(s) being monitored.
17
Agenda
LTE Market Overview
LTE & EPC Technology Overview
LTE & EPC Challenges
Short Intro to Agilent in LTE
Assurance SolutionsSS7, VoIP, IMS, 3G
Infrastructure Vendors
Service Providers
N2X Router Test
Signalling AnalyzerNetwork Analyzer
Triple Play Analyzer
Drive Test, Scanner, Portable Spectrum Analyzer
RF Analysis &Wireless Conformance Test
LTE Solutions across Lifecycle
Network
Plan &
Design
Install &
Commission
Optimize &
Maintain
Monitor &
Manage
Business
Applications
Network
Element
R&D,
Design,
Production
Functional Test
Load Test
IOT
18
Signaling Analyzer Real-Time for LTE/SAE
Increase Test Efficiency & Quality
• Expert Analysis
– Focus on the test not the tool
• Full Visibility
– LTE/SAE protocols & procedures
– Intertechnology Testing, 2G, 3G, VoIP/IMS, ...
• Remove the guess work
– Real –Time Performance Analysis & Benchmarking
– KPI’s & Measurements aligned to standards:
• 3GPP, LSTI & NGMN Requirements
• Decrease Cycle Times
• Parallel / Concurrent Testing
– Multi-User Simultaneous Analysis
• Test automation for centralized regression
LTE Real-Time Troubleshooting & Analysis
• Functional Test, I&V test
• Load and Stress
• Trial, Deployment & Optimization
E6474A DT
Data S/W
Mobile Phone Trace Data
• Active, Neighbor Sets
• Protocol Messaging
RF Receiver Data
•Ec/Io
•Pilots Sets
• Agg Ec/Io, Delay Spread
•Internal GPS timing
•Serial Port Protocol capture
Signaling
AnalyzerTrace Port
E6474A Data Tests
• HTTP, FTP, EMAIL
• WAP, SMS
• DIALUP, VOICE AVAIL
• Audio/Video Streaming
• Video Telephony
Receiver
TCP/IP Performance
• TCP Re-Tx, resets
• IP Throughput
• Duplicate packets
Session Evaluation
• Graphical display of call trace
parameters
• Correlation of IP & Mobile protocols
• Supports IP, PPP, SIP, RTP
The LTE Air Interface - Agilent’s Test Methodology
19
Agilent in Standards
Agilent has been closely involved with ETSI and 3GPP since 1991
• Current delegates
• RAN WG4 (LTE air interface) – Moray Rumney
• RAN WG5 (UE conformance test) – Andrea Leonardi & Muthu Kurmaran
• Agilent has hosted many 3GPP meetings,
• Main focus has been on RF requirements and testing of the Node B and UE
• Currently leading discussions in WG4 on HSPA+ & LTE higher order modulation
Agilent in LSTI (Member since Feb-2008)
• Agilent is active in all Working Groups (POC, IODT, IOT and Trial).
• Providing expertise in Test methodology, Test concepts and specific Test cases.
• Test tools are aligned to demonstrate the capabilities according to the different proof points of LSTI.
• Agilent provides tools for both Network infrastructure and Handset testing
Agilent is a contributor in datacom standards forums:
• ATM forum
• MPLS forum (MFA Forum)
• Metro Ethernet Forum etc.
Agilent LTE Book – Available Now
• LTE and the Evolution to 4G Wireless
• Agilents new LTE book delves into the new 3GPP LTE cellular technology, from both the technical and practical point of view, before its projected deployment in 2010.
• Written by Agilent s measurement experts, this LTE book offers valuable insight into LTE technology and its design and test challenges.
• In this 450-page book you will find chapters covering the following:
– An introduction to LTE
– Air interface concepts & Physical layer
– Upper layer signaling,
– System architecture evolution,
– RF design and verification challenges
– UE Conformance testing
– A look to 4G: LTE-advanced.
SART LTE/SAE Solution
Overview
20
Thank You
Agilent Technologies-- the supplier of choice for your
design and test needs during LTE development
• The leader in design and test tools
– Design and test tools ready when you need them
• First products shipping today
• New measurement products will follow throughout the
technology development cycle
– Committed to new measurement technologies and
active involvement in standards setting
Agilent Technologies
You drive the path to LTE, Agilent clears the way.
3GPP LTE Standards References
3GPP TS Title Interface(s)
24.301 Non-Access-Stratum (NAS) Protocol for Evolved Packet System (EPS); Stage 3 S1-C, S101
24.312 Access Network Discovery and Selection Function (ANDSF) Management Object (MO) S14
29.061 Interworking between PLMN supporting packet based services and PDN SGi
29.118 Mobility Management Entity (MME) - Visitor Location Register (VLR) SGs Interface Specs. SGs
29.168 Cell Broadcast Centre Interfaces with the Evolved Packet Core; Stage 3 SBc
29.212 Policy and Charging Control over Gx Reference Point Gx, Gxa, Gxc
29.214 Policy and Charging Control (PCC) over Rx Reference Point Rx
29.215 Policy and Charging Control (PCC) over S9 Reference Point S9
29.272 MME Related Interfaces Based on Diameter Protocol S6a, S6d, S13, S13’
29.273 EPS; 3GPP AAA Interfaces SWa/d/m/x, STa, S6b, H2, Pi*
29.274 Evolved General Packet Radio Service (GPRS); Tunneling Protocol for Control plane (GTPv2-C) S3-C, S4-C, S5/8-C, S10, S11
29.275 Proxy Mobile IPv6 (PMIPv6) based Mobility and Tunneling Protocols; Stage 3 S2a-C, S2b-C, S5/8-C (PMIP)
29.276 Optimized Handover Procedures and Protocols between EUTRAN Access and cdma2000 HRPD S101
29.277 Optimized Handover Procedures and Protocols between EUTRAN Access and 1xRTT Access S102
29.279 Mobile IPv4 (MIPv4) based Mobility Protocols; Stage 3 S2a-C
29.280 3GPP EPS Sv Interface (MME to MSC) for SRVCC Sv
29.281 GPRS Tunneling Protocol User Plane (GTPv1-U) S1-U, X2-U, S4-U, S5/8-U, S12-U
36.321 E-UTRA; Medium Access Control (MAC) Protocol Specification Uu
36.322 E-UTRA; Radio Link Control (RLC) Protocol Specification Uu
36.323 E-UTRA; Packet Data Convergence Protocol (PDCP) Specification Uu
36.331 E-UTRA; Radio Resource Control (RRC) Protocol Specification Uu, S1, X2, S3
36.413 E-UTRAN: S1 Application Protocol (S1AP) S1-C
36.423 E-UTRAN: X2 Application Protocol (X2AP) X2-C
21
3GPP TR 23.401 / 25.813
Network Overview – LTE – SAE Network Identifiers
• PLMN – Public Land Mobile
Network
• EPS – Evolved Packet
System
• MME – Mobility
Management Entity
• eNB – E-UTRAN Node B
• TAI - Tracking Area ID
• E-UTRAN – Evolved
Universal Radio Access
Network
• C-RNTI – Cell Radio
Network Temporary Identifier
• RA-RNTI – Random Access
RNTI
• UE – User Equipment
• IMEI – International Mobile
Equipment Identity
• IMSI (MSISDN) –
International Mobile
Subscriber Identity
• S-TMSI – SAE Temporary
Mobile Subscriber Identity
Network Overview – LTE Interfaces
• S1-MME: The S1-MME interface provides the control plane protocol between the Evolved UTRAN and MME.
• S1-U: The S1-U interface provides a per bearer user plane tunneling between the Evolved UTRAN and Serving GW.
– It contains support for path switching during handover between eNodeBs.
– S1-U is based on the GTP-U protocol that is also used for Iu user plane in the Rel-7 architecture.
• S3: The S3 interface enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state.
– It is based on the GTP protocol and the Gn interface as defined between SGSNs.
• S4: The S4 interface provides the user plane with related control and mobility support between GPRS Core and the 3GPP Anchor function of Serving GW and is based on the GTP protocol and the Gn reference point as defined between SGSN and GGSN.
• S5: The S5 interface provides user plane tunneling and tunnel management between Serving GW and PDN GW.
– It is used for Serving GW relocation due to UE mobility, and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity.
– There are two variants of the S5 interface, one based on the GTP protocol and one IETF variant based on Proxy Mobile IPv6 (PMIP).
22
Network Overview – LTE Interfaces, continued…
• S6a: Enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME and HSS.
• S7: Provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW. The interface is based on the Gx interface.
• S8a: Is the roaming interface in case of roaming with home routed traffic. It provides user plane with related control between the Serving GW in the VPLMN and the PDN GW in the HPLMN.
– It is based on the GTP protocol and the Gp interface as defined between SGSN and GGSN.
– S8a is a variant of S5 for the roaming (inter-PLMN) case. There is also an IETF variant of called S8b that is based on Proxy Mobile IPv6 (PMIP).
• S10: Is between MMEs and provides MME relocation and MME to MME information transfer
• S11: Is the interface between MME and Serving GW.
• SGi: Is the interface between the PDN GW and the packet data network.
– This interface corresponds to Gi and Wi interfaces and support any 3GPP or non-3GPP access.
• Rx+: Is the interface between the AF and the PCRF.