Cisco Public 1 © 2010 Cisco and/or its affiliates. All rights reserved.
4G Mobile Networks Long Term Evolution (LTE) Vladimir Settey
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 2
• The revolution is here (smartphones / tablets / netbooks)
• Broadband, anytime, anywhere
• Flat-rate data ?
• Data growth exponential; revenue growth linear.
• Scaling the network for data
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 3
Evolution of Mobile Networks
LTE Architecture Overview
EPC Mobility
Services in LTE
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 5
Voice oriented architecture
Re-define fixed wireline services (e.g. SS and IN)
SMS is a signalling transport rather than a data service
Network transport based on TDM
• There was wireless ISDN (aka GSM)
Base Station Controller
(BSC)
Mobile Switching Center + Visitor Locatio(MSC/VLR)
n Register Base Transceiver
System (BTS) Mobile Station
GSM Radio
GSM Radio
16/64 kbps
16/64 kbps
64/2048 kbps
64/2048 kbps
LAP-Dm LAP-Dm LAP-D LAP-D
Radio Resource
Mgmt RR’ BTSM BTSM
RR’ BSSAP
Mobility Mgmt
Connection Mgmt
BSSAP
DTAP
Mobility Mgt
Connection Mgmt
64 kbps
MTP
TUP
SCCP
TCAP
ISU
P
INA
P
MA
P
BS
SM
AP
MTP/MTPb SCCP
MTP/b SCCP
Home Location Register (HLR)
Service Control Point (SCP)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 6
• One burst every TDMA frame was sufficient to transport a speech frame with source rate of 13 kbit/s
• GSM Phase 2 (circa 1996) added Circuit Switched Data support offering 9.6 kbit/s service
• High Speed CSD consisted in aggregating multiple timeslot for a single user but resource intensive
BSC MSC
Modem Interworking Function (IWF)
Modified V.110
3.1 kHz audio or V110 64k UDI
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 7
BSC MSC/VLR Gateway MSC BTS
GSM Radio
GSM Radio 64 kbps 64 kbps L1bis
MAC
IP
RLC
LLC
SNDCP
Relay MAC RLC
Nw Services
BSSGP Relay
L1bis
Nw Services
BSSGP
LLC
SNDCP
L1
L2 IP
UDP
GTP Relay
L1
L2 IP
UDP
GTP
IP
Packet Control Unit (PCU) Serving GPRS
Support Node (SGSN)
Gateway GPRS Support Node
(GGSN)
IP
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 8
• First step towards an all IP network
• Designed to accommodate greater packet throughput (up to 2Mbits/s announced… In reality, can support up to 384 kbit/s)
• Core network remains largely unchanged from 2.5G
• Migration to ATM for Radio Access Transport
• More control into the RNC
3G RNC
3G MSC
3G SGSN GGSN
IP
ATM/AAL2 ATM/AAL5
Node B
PSTN
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 9
• So hopefully WCDMA got it right on packet services…
Radio Network Controller (RNC)
3G SGSN GGSN
Iu-ps Gn/Gp
WCDMA Radio
WCDMA Radio
ATM
MAC
IP
RLC PDCP
Frame Protocol AAL2
ATM
AAL2
MAC
RLC PDCP
ATM
AAL5
IP
UDP GTP-U
IP
UDP GTP-U
IP
UDP GTP-U
ATM
AAL5
L1
L2
IP
UDP GTP-U
L1
L2
IP
NodeB
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 10
• Still Voice over CS bearer on the radio access, data bearer not suitable (latency, overhead)
• Option to transport Voice over IP in the Core (see TS 23.205)
• Introduction of SS7oIP transport
Iu-cs IP
MGW MGW
MSC-s MSC-s
HLR
ATM
Iu-UP
L1/2
IP AAL2 UDP
RTP
L1/2
IP
M3UA
TCAP
INA
P
MA
P
SCTP
SCCP BIC
C o
r SIP
-T
H.2
48
Nb-UP
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 11
L1
RLC PDCP
MAC UDP
GTP-U
IP
Serving RNC 3G SGSN GGSN
Gn Iu-ps
IP
UDP GTP-U
L1
L2
IP
IP
UDP GTP-U
L1
L2
IP
UDP GTP-U
L1
AAL5/ATM AAL5/ATM
L1
Frame Protocol
AAL2/ATM
RLC PDCP
WCDMA
IP
MAC
L1
Frame Protocol
AAL2/ATM
WCDMA
Drift RNC
L1
FP
L1
FP
AAL2 AAL2
Node B
HSDPA Removes Drift RNC and adds intelligence to the Node B
Direct Tunnel allows SGSN to remove itself from data plane
HSPA+: Distribute RNC Data plane to Node B
MAC-HS MAC-HS L2
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 12
DL: 384 kps UL: 384 kbps
DL: Up to 14.4 Mbps UL: 384 kbps
2007 2008 2009 2010+
DL:Up to 14.4 Mbps UL: 5.7 Mbps
DL: 28 Mbps UL: 11 Mpbs
DL: 42 Mbps UL: 11 Mpbs
Rel-99
WCDMA
Rel-5
HSDPA
Rel-6
HSUPA
Rel-7
MIMO 2x2
Rel-8
64 QAM
HSDPA: 16 QAM DL 14.4 Mbps
HSDPA: Always on scaling
HSUPA: 5.7 Mbps
HSDPA: 64 QAM, MIMO
HSUPA: 16QAM Always on scaling
HSDPA: 64 QAM
and MIMO
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 13
• Highlighting the growing importance of IP transport
3G MSC-S
3G SGSN GGSN
Core IP
IP RAN w/ ATM PW or Native IP
Node B
PSTN
3G RNC 3G MGW
HLR/HSS
SGW
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 14
• Evolved Packet System (EPS) is the technology direction for 3GPP based networks
• Long Term Evolution (LTE) is the next generation 3GPP radio access network
Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)
• System Architecture Evolution (SAE) is the 3GPP next generation standard for mobile networks providing:
Increased Bandwidth End-to-End IP Simplified Architecture Support for multiple radio access technologies
• Evolved Packet Core (EPC) is the next generation 3GPP packet core Consists of (3) main components (MME, SGW, and PGW)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 15
• Radio Side (Evolved UTRAN - EUTRAN) Improvements in spectral efficiency, user throughput, latency Simplification of the radio network Efficient support of packet based services: Multicast, VoIP, etc.
• Network Side (Evolved Packet Core - EPC) Improvement in latency, capacity, throughput, idle to active transitions Simplification of the core network Optimization for IP traffic and services Simplified support and handover to non-3GPP access technologies
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 16
• Higher Bandwidth (>100 kbps per user on average) and improved latency
Transmission and transition delays <10 & 100ms resp. in unloaded conditions • Service independent and data-only architecture
Strict data QoS mechanism with no voice dedicated bearer identifictaion • Always-on model
All registered users have a default bearer established used for signalling • IP addressing
IPv6 by default with dual stack sessions (IPv4v6) • Support of alternative access technologies
3GPP and non-3GPP architecture, including possible wireline access • Local breakout
Part of the traffic may be routed directly in the visited network
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 18
Duplex FDD and TDD
Channel Bandwidth 1.25 – 20 MHz
Modulation Type QPSK, 16-QAM, 64-QAM
Multiple Access Technique DL: OFDMA, UL: SCFDMA
TDMA Frame Duration 10ms with 1ms subframe
Number of symbols per frame 140
Sub-carrier Spacing 15 kHz
Symbol Duration 66.7 us
Cyclic Prefix 4.69 us, 16.67 us
Multipath Mitigation OFDM / Cyclic Prefix
eNB Synchronization Frequency (FDD, TDD) Time (TDD, MBSFN)
Forward Error Correction 1/3 Convolutional and Turbo
Advanced Antenna Techniques MIMO 2x2, 4x4
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 19
Freq
uenc
y"
Time"
CDMA"(3G)"
OFDM"
TDMA"(2G)"
OFDMA"(LTE & WiMAX)"
Sub-
Cha
nnel"
(Gro
up o
f"Fr
eque
ncie
s)"
Sub-
Cha
nnel"
(Gro
up o
f"Fr
eque
ncie
s)"
user A
user B
user C
Freq
uenc
y"
FDMA"
Freq
uenc
y"
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 20
Frequency One Resource Element
Sub-carrier Spacing 15 kHz
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 21
5 MHz 10 MHz
20 MHz
3 MHz
1.4 MHz
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 22
QPSK ( 55% of cell area)
16QAM (18% of cell area)
64QAM (13% of cell area)
256QAM (14% of cell area)
Maximising the bandwidth made available to the users by selecting the optimum modulation scheme (QPSK, 16QAM, 64QAM, etc.)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 23
• Downlink Physical Broadcast Channel (PBCH) Physical Downlink Shared Channel (PDSCH) Physical Downlink Control Channel (PDCCH) Physical Control Format Indicator Channel (PCFICH) Physical Hybrid ARQ Indicator Channel (PHICH)
• Uplink Physical Random Access Channel (PRACH) Physical Uplink Shared Channel (PUSCH) Physical Uplink Control Channel (PUCCH)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 25
3GPP Access
E-UTRAN PGW SGW eNodeB
PCRF
Operator’s IP Services
(e.g. video, IMS)
HSS
S11 (GTP-C)
S1-U (GTP-U)
S2b (PMIPv6,
GRE)
MME
S5/8 (PMIPv6, GRE)
S6a (DIAMETER)
S1-MME (S1-AP)
GERAN
S4 (GTP-C, GTP-U) UTRAN
SGSN
Trusted Non-3GPP IP Access
Untrusted Non-3GPP IP Access
S3 (GTP-C)
S12 (GTP-U)
S10 (GTP-C)
S5/8 (GTP-C, GTP-U)
Gx (DIAMETER) Gxb
SWx (DIAMETER)
STa (RADIUS, DIAMETER)
ePDG
AAA
SWn
S6b (DIAMETER)
SWm (DIAMETER)
SGi
SWa
Gxa
Rx+ (DIAMETER)
S2c
UE S2a
(PMIPv6, GRE MIPv4 FACoA)
Gxc
UE UE
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 26
3GPP Access
E-UTRAN PGW SGW eNodeB
PCRF
Operator’s IP Services
(e.g. video, IMS)
HSS
S11 (GTP-C)
S1-U (GTP-U)
S2b (PMIPv6,
GRE)
MME
S5/8 (PMIPv6, GRE)
S6a (DIAMETER)
S1-MME (S1-AP)
GERAN
S4 (GTP-C, GTP-U) UTRAN
SGSN
Trusted Non-3GPP IP Access
Untrusted Non-3GPP IP Access
S3 (GTP-C)
S12 (GTP-U)
S10 (GTP-C)
S5/8 (GTP-C, GTP-U)
Gx (DIAMETER) Gxb
SWx (DIAMETER)
STa (RADIUS, DIAMETER)
ePDG
AAA
SWn
S6b (DIAMETER)
SWm (DIAMETER)
SGi
SWa
Gxa
Rx+ (DIAMETER)
S2c
UE S2a
(PMIPv6, GRE MIPv4 FACoA)
Gxc
UE UE
Mobility Management Entity E-UTRAN Control Plane with 2G/3G interworking (no user plane handling)
• Interacts with HSS for user authentication, profile download, etc.
• Interacts with eNodeB and SGW for SGW selection, tunnel control, paging, handovers, etc.
• Interacts with SGSN for 2G/3G
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 27
3GPP Access
E-UTRAN PGW SGW eNodeB
PCRF
Operator’s IP Services
(e.g. video, IMS)
HSS
S11 (GTP-C)
S1-U (GTP-U)
S2b (PMIPv6,
GRE)
MME
S5/8 (PMIPv6, GRE)
S6a (DIAMETER)
S1-MME (S1-AP)
GERAN
S4 (GTP-C, GTP-U) UTRAN
SGSN
Trusted Non-3GPP IP Access
Untrusted Non-3GPP IP Access
S3 (GTP-C)
S12 (GTP-U)
S10 (GTP-C)
S5/8 (GTP-C, GTP-U)
Gx (DIAMETER) Gxb
SWx (DIAMETER)
STa (RADIUS, DIAMETER)
ePDG
AAA
SWn
S6b (DIAMETER)
SWm (DIAMETER)
SGi
SWa
Gxa
Rx+ (DIAMETER)
S2c
UE S2a
(PMIPv6, GRE MIPv4 FACoA)
Gxc
UE UE
Home Subscriber Services (HSS) Centralised database holding user profile:
• Interacts with MME for user authentication and profile download
• Stores current location information (e.g. assigned MME, Serving SGW)
• One or more subscription profiles containing IMSI, QoS, Services, etc.
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 28
3GPP Access
E-UTRAN PGW SGW eNodeB
PCRF
Operator’s IP Services
(e.g. video, IMS)
HSS
S11 (GTP-C)
S1-U (GTP-U)
S2b (PMIPv6,
GRE)
MME
S5/8 (PMIPv6, GRE)
S6a (DIAMETER)
S1-MME (S1-AP)
GERAN
S4 (GTP-C, GTP-U) UTRAN
SGSN
Trusted Non-3GPP IP Access
Untrusted Non-3GPP IP Access
S3 (GTP-C)
S12 (GTP-U)
S10 (GTP-C)
S5/8 (GTP-C, GTP-U)
Gx (DIAMETER) Gxb
SWx (DIAMETER)
STa (RADIUS, DIAMETER)
ePDG
AAA
SWn
S6b (DIAMETER)
SWm (DIAMETER)
SGi
SWa
Gxa
Rx+ (DIAMETER)
S2c
UE S2a
(PMIPv6, GRE MIPv4 FACoA)
Gxc
UE UE
Serving Gateway Data plane anchoring for 3GPP access and 2G/3G bearer plane interworking
• Anchor point in visited network for 3GPP Access (2G/3G/LTE)
• Processes all IP packets to/from UE (QoS control, LI)
• Uses network-based mobility towards PDNGW (GTP or PMIPv6)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 29
3GPP Access
E-UTRAN PGW SGW eNodeB
PCRF
Operator’s IP Services
(e.g. video, IMS)
HSS
S11 (GTP-C)
S1-U (GTP-U)
S2b (PMIPv6,
GRE)
MME
S5/8 (PMIPv6, GRE)
S6a (DIAMETER)
S1-MME (S1-AP)
GERAN
S4 (GTP-C, GTP-U) UTRAN
SGSN
Trusted Non-3GPP IP Access
Untrusted Non-3GPP IP Access
S3 (GTP-C)
S12 (GTP-U)
S10 (GTP-C)
S5/8 (GTP-C, GTP-U)
Gx (DIAMETER) Gxb
SWx (DIAMETER)
STa (RADIUS, DIAMETER)
ePDG
AAA
SWn
S6b (DIAMETER)
SWm (DIAMETER)
SGi
SWa
Gxa
Rx+ (DIAMETER)
S2c
UE S2a
(PMIPv6, GRE MIPv4 FACoA)
Gxc
UE UE
Packet Data Network Gateway (PGW) Subscriber-aware data plane anchoring for all access networks
• Anchor point in home or visited network for all IP-based access (3GPP or not)
• Session-based user authentication and IP address allocation (IPv4/v6)
• Processes all IP packets to/from UE (QoS control, PCEF, LI)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 30
3GPP Access
E-UTRAN PGW SGW eNodeB
PCRF
Operator’s IP Services
(e.g. video, IMS)
HSS
S11 (GTP-C)
S1-U (GTP-U)
S2b (PMIPv6,
GRE)
MME
S5/8 (PMIPv6, GRE)
S6a (DIAMETER)
S1-MME (S1-AP)
GERAN
S4 (GTP-C, GTP-U) UTRAN
SGSN
Trusted Non-3GPP IP Access
Untrusted Non-3GPP IP Access
S3 (GTP-C)
S12 (GTP-U)
S10 (GTP-C)
S5/8 (GTP-C, GTP-U)
Gx (DIAMETER) Gxb
SWx (DIAMETER)
STa (RADIUS, DIAMETER)
ePDG
AAA
SWn
S6b (DIAMETER)
SWm (DIAMETER)
SGi
SWa
Gxa
Rx+ (DIAMETER)
S2c
UE S2a
(PMIPv6, GRE MIPv4 FACoA)
Gxc
UE UE
Policy&Charging Rule Function (PCRF) User and application-aware policy decision point:
• Interacts with PGW to enforce per session or per flow policies
• Gets event notification from PGW (mobilty and/or traffic related)
• Interacts with application for admission control and policy definitiion
• Supports roaming capabilities
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 31
3GPP Access
E-UTRAN PGW SGW eNodeB
PCRF
Operator’s IP Services
(e.g. video, IMS)
HSS
S11 (GTP-C)
S1-U (GTP-U)
S2b (PMIPv6,
GRE)
MME
S5/8 (PMIPv6, GRE)
S6a (DIAMETER)
S1-MME (S1-AP)
GERAN
S4 (GTP-C, GTP-U) UTRAN
SGSN
Trusted Non-3GPP IP Access
Untrusted Non-3GPP IP Access
S3 (GTP-C)
S12 (GTP-U)
S10 (GTP-C)
S5/8 (GTP-C, GTP-U)
Gx (DIAMETER) Gxb
SWx (DIAMETER)
STa (RADIUS, DIAMETER)
ePDG
AAA
SWn
S6b (DIAMETER)
SWm (DIAMETER)
SGi
SWa
Gxa
Rx+ (DIAMETER)
S2c
UE S2a
(PMIPv6, GRE MIPv4 FACoA)
Gxc
UE UE
Enhanced Packet Data Gateway (ePDG) Support for untrusted non-3GPP access
• EPC point of attachment for user accessing over other non-owned access
• Terminates IPSec tunnel from UE established with IKEv2 & EAP-AKA
• Supports network-based IP mobility towards the selected PGW (PMIPv6)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 32
E- UTRAN
MME
eNB
UE
HSS S6a
(Auth Vectors) EPS AKA via S6a
Challenge and keys exchange
Mutual Authentication
NAS Integrity/Ciphering RRC Integrity and ciphering
U-Plane Ciphering
• USIM required for LTE
• Different set of keys used for ciphering, derived from the same original K stored in the USIM/HSS
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 33
UE
MME
S-GW
Evolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)
HSS PCRF
PDN-GW
MAC RLC
PDCP
OFDMA
NAS
MAC RLC
PDCP
OFDMA
L2 IP
L1
SCTP S1-AP RRC RRC
L2 IP
L1
SCTP S1-AP NAS
S1-MME
36.413
S1-MME
eNodeB
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 34
UE
MME
S-GW
Evolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)
HSS PCRF
PDN-GW
IP
L1 L2
IP (user)
IP UDP
GTP-U
L1 L2 MAC
RLC PDCP
OFDMA
IP (user)
MAC
RLC PDCP
OFDMA
IP UDP
GTP-U
L1 L2
IP UDP
GTP-U
L1
L2
PMIP
S1-U S5/S8
S1-U 36.414 GRE GRE UDP
PMIP GTP-U S5/S8
29.274 (GTP)
- 29.275
(PMIPv6)
eNodeB
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 35
UE
MME
S-GW
Evolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)
HSS PCRF
PDN-GW
X2
L2 IP
L1
SCTP X2-AP
L2 IP
L1
SCTP X2-AP
X2-C
L2 IP
L1
UDP GTP-U
L2 IP
L1
UDP GTP-U
X2-U
36.423 36.424
eNodeB
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 36
UE
eNodeB
MME
S-GW
Evolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)
HSS PCRF
PDN-GW
Gx
L2 IP
L1
SCTP DIAMETER
Gx
L2 IP
L1
SCTP DIAMETER
L2 IP
L1
SCTP DIAMETER
S6a
L2 IP
L1
SCTP DIAMETER
29.272 29.212
S6a
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 37
Extract from 3GPP TS 23.401 V8.3.0 (2008-09)
• A UE shall perform the address allocation procedures for at least one IP address (either IPv4 or IPv6)
• PDN types IPv4, IPv6 and IPv4v6 are supported
• /64 IPv6 prefix allocation via IPv6 Stateless Address autoconfiguration according to RFC 4862, if IPv6 is supported (Mandatory)
• IPv6 parameter configuration via Stateless DHCPv6 according to RFC 3736 (Optional)
“During default bearer establishment, the PDN GW sends the IPv6 prefix and Interface Identifier to the SGW, and then the S-GW forwards the IPv6 prefix and Interface Identifier to the MME or to the SGSN. The MME or the SGSN forwards the IPv6 Interface Identifier to the UE.”
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 39
• Idle Mode Mobility procedures UE Initial Attach Periodic Location Update / Inter- and intra-RAT reselection UE Detach
• Active Mode Mobility Intra-RAT Intra- and inter-area handover Inter-RAT handover
• RRC States RRC-IDLE RRC-CONNECTED
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 40
3G UE 3G RNC 3G SGSN 3G GGSN HLR
1. Attach Request
2. Identity Request/Response
3. UE Authentication (EAP-AKA) and Ciphering Start
4. User Profile Download
5. Attach Accept/Complete
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 41
3G UE MME S-GW HSS 1. Attach Request
2. Identity Req/Rsp
3. UE Authentication (EAP-AKA) and Ciphering Start
4. User Profile Download
5. Bearer Request
10. Attach Accept/Complete
PCRF
P-GW
6. Bearer Request
Bearer Authorisation (inc. IP @, policy)
8. Bearer Accept 9. Bearer Accept
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 42
13. Update PDP Req
3G UE Old RNC Old SGSN GGSN
2. Relocation Required
5. RAB establishment at target NodeB
1. HO Preparation
Target RNC Target SGSN
3. Fwd Reloc Req
6. Relocation Request Ack
4. Relocation Request
7. Fwd Reloc Ack 8. Relocation Command 9. Reconfig Radio
10. SRNS Context Transfer
12. Relocation Detected
15. Update PDP Ack
11. Relocation Detected
Relocation Completion including Radio resource release at Old RNC and RAU procedure
14. Policy Ctrl (optional)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 43
3. Create Session Req
3G UE MME Old S-GW
2. Path Switch Req
Target S-GW P-GW Old eNB Target eNB
Fwd Data 1. HO prep and exec
Established 2-way Bearer
DL Data
4. Modify Bearer Req
6. Modify Bearer Ack 5. Policy Ctrl
7. Create Session Resp
8. Path Switch Resp
9. Release 10. Delete Session Req/Resp
Established 2-way Bearer
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 44
3G UE Old S-GW
8. HO Command
Target S-GW
3. Create Session Req/Resp
P-GW Old MME Target MME 1. HO preparation
14. Modify Bearer Req
16. Modify Bearer Resp 15. Policy Ctrl
5. Create Indirect TunnelReq/Resp 4. HO prep at Target eNB
7. Create Indirect TunnelReq/Resp
6. Fwd Reloc Resp
9. HO Command
2. Fwd Reloc Req
11. HO Notify 10. eNB context transfer
13. Update Session Req
17. Update Session Resp
Relocation Completion including radio resource release at Old eNB and Session and Fwd tunnel tear down at old MME/SGW
12. Reloc Complete Req/Resp
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 46
• The EPS architecture (3GPP Rel 8) is the first 3GPP all-IP architecture
• Voice and SMS are still the cash cows for mobile operators
Migration is critical User experience must be preserved
• CSFB is the interim solution recommended by NGMN
• IMS is the target solution for Telephony and Multimedia Services
• OneVoice IMS profile ‘simplifies’ implementation for VoLTE
• NGMN and OneVoice initiatives reduce risk of industry fragmentation
• SMS typically required before voice due to EU regulatory requirements for data roaming services
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 47
• During EPC attach, CSFB UE’s are also attached over SGs to MSC
• MME maintains mapping of TA to LA to determine appropriate MSC to establish SGs association with
• SMS can be delivered/sent without FallBack to legacy radio (SGs interface includes SMS payload capability)
S1-MME
SGs
S11
S6a
IuCS / A
S1-U CSFB UE E-UTRAN Serving/
PDN GW
MME
UTRAN / GERAN MSC
HSS
Incoming SMS 1
SMS is delivered via SGs interface 2
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• Additional complexity / upgrades required on CS core to support use-case where the MSC sending Page is different to MSC receiving Page response (i.e. TA to LA mapping is inaccurate due to cell breathing or other circumstances)
• This capability (Roaming Retry) requires upgrades on GMSC, VMSC and HLR. Introduces further termination latency.
S1-MME
SGs
S11
S6a
IuCS / A
S1-U CSFB UE E-UTRAN Serving/
PDN GW
MME
CSFB UE UTRAN / GERAN MSC
HSS
Incoming Call – delivered to VMSC which has SGs association for this subscriber
1
UE is paged via the SGs interface 2
UE retunes to 2G/3G RAT on receipt of page
3
UE Responds to paging – incoming call terminated via standard 2G/3G procedures
4
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Public 49
• To enable mid-call mobility, S-CSCF anchors call at SCC AS
• TAS provides end-user services (e.g. IR.92)
• MGCF provides breakout to PSTN or other CS networks
ISC
Mw
S1-MME
Sv
S11
Mg
SGi (Gm from UE)
S6a
IuCS / A
IuPS / Gb
S3
S1-U
Cx
IMS (HPLMN)
P-CSCF
SR-VCC UE E-UTRAN Serving/ PDN GW
MME
UTRAN / GERAN
MSC Server (SR-VCC)
SGSN (SR-VCC)
I/S-CSCF
HSS
TAS SCC AS IP-SM-GW
MGCF
Subscriber has already registered into IMS following EPC attach
UE Originates Call
1
2
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• SCC AS performs leg management – hides mobility events from other IMS application servers
• SR-VCC only works in one direction – LTE 2G/3G
• Requires upgrades on legacy MSC infrastructure
ISC
Mw
S1-MME
Sv
S11
Mg
SGi (Gm from UE)
S6a
IuCS / A
IuPS / Gb
S3
S1-U
Cx
IMS (HPLMN)
P-CSCF
SR-VCC UE E-UTRAN Serving/ PDN GW
MME
SR-VCC UE UTRAN / GERAN
MSC Server (SR-VCC)
SGSN (SR-VCC)
I/S-CSCF
HSS
TAS SCC AS IP-SM-GW
MGCF
UE retunes to 2G/3G RAT during active call
1
New call leg established
2
SCC AS performs bearer management and tears down original leg
3
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CSFB VoIMS End-User Services Re-use legacy implementation OneVoice (IR.92) provides baseline. All
operator proprietary services and extensions must be ported to IMS.
Regulatory Re-use legacy implementation National regulatory services must be implemented in IMS.
Service Differentiation Restricted to only services deliverable from legacy core.
IR.92 services can be blended with other IMS services such as presence, RCS, rich messaging.
End-user Experience Significant post-dial delay. Retuning from CS back to LTE may take some time – impact to data services.
No retuning required to access CS equivalent services. Still industry concerns regarding SR-VCC latency.
Complexity Medium – CS core requires upgrades for SGs interface and also to support Roaming Retry.
High – Significant new network infrastructure required. SR-VCC extremely complex. Intensive service porting to ensure full legacy parity.
Cost Unknown – upgrades must come from existing CS vendors. Believed that legacy vendors are using this to their advantage to seek premium.
High – large investment required for new infrastructure. However, diverse range of vendors opens door for innovative deals/solutions.