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Advanced Mobile Communication Networks 1
Integrated Communication Systems Group
Mobile Network Evolution – Part 2
From UMTS to LTEor
How to Further Increase Network Capacity and QoS
Andreas Mitschele-Thiel
Advanced Mobile Communication Networks 2
Integrated Communication Systems Group
Outline
• Evolution from Circuit Switching to Packet Switching– Architecture– Packet handling – Resource management and QoS– Comparison with 802.11
• LTE– Features and requirements– Architecture– Protocols– Packet handling and resource management– Mobility management and HO– Self-organization
• Conclusions• References• Abbreviations
Advanced Mobile Communication Networks 3
Integrated Communication Systems Group
Review: From GSM to UMTS
GPRS Core(PacketSwitched)
SGSN
GGSN
Internet
GSMRAN
Base stationBase stationcontroller
Base station
Base station
UTRAN
Radio networkcontroller
node Bnode B
node B
MSC
PSTN
GSM Core (Circuit switched)
HLRAuCEIR
GMSC
IMS
+HSPA
+EDGE
Advanced Mobile Communication Networks 4
Integrated Communication Systems Group
Circuit vs. Packet Switched Communication
Connection (e.g. voice, CS data) => principle for GSM & UTRAN design• clearly defined start and end times• no burstiness=> dedicated channels
minutesconnection
setupconnection
release
Packet session => supported by GPRS core, IMS, SAE, HSPA, LTE• packet arrival times are typically unknown to the system• traffic is highly bursty=> shared channels & packet scheduling
hours
seconds
Advanced Mobile Communication Networks 5
Integrated Communication Systems Group
Resource Management in UMTS (radio link)When to free resources? After short or long breaks?
hours
seconds
cell_DCH
URA_PCH
cell_FACH
idle
fast release slow release
Advanced Mobile Communication Networks 6
Integrated Communication Systems Group
resourceconsumption
latency
• radio resources• channel codes• HW resources
• setup delay
• transient resource usage
cell_DCH
URA_PCH
cell_FACH
idle
T1
T2
T3
Resource Management in UMTS (radio link)When to free resources? After short or long breaks?
Advanced Mobile Communication Networks 7
Integrated Communication Systems Group
End-to-End Resource Management in UMTS (contr. plane)A sophisticated QoS architecture
Transl. Transl.
Adm.Contr
RAB Manager
UMTS BS Manager
UMTS BS Manager
UMTS BS Manager
Subscr.Control
Adm./Cap.Control
MT GatewayCN EDGEUTRAN
Ext. Service Control
Local Service Control
Iu BS Manager
Radio BS Manager
Iu NS Manager
UTRA ph. BS M
Radio BS Manager
UTRA ph. BS M
Local BS Manager
Adm./Cap. Control
Adm./Cap.Control
Adm./Cap. Control
Iu BS Manager
Iu NS Manager
CN BS Manager
Ext. BS Manager
CN BS Manager
service primitive interface protocol interface
BB NS Manager
BB NS Manager
TE Ext. Netw.
Advanced Mobile Communication Networks 8
Integrated Communication Systems Group
End-to-End Resource Management in UMTS (user plane)
ResourceManager
Mapper
Classif
Cond.
ResourceManager
ResourceManager
Mapper
ResourceManager
Mapper
ResourceManager
ResourceManager
Cond.
Classif
Cond.
MT GatewayCN EDGEUTRAN
BB network serviceIu network serviceUTRA phys. BS
data flow with indication of direction
TE Ext.Netw.
Local BS External BS
Advanced Mobile Communication Networks 9
Integrated Communication Systems Group
Evolution from GSM to UMTS and LTE GSM: voice-dominated, dedicated channels, heavy statesGPRS: add support for packet data on shared channels; add IP-based core
networkEDGE: increased packet data capacity of GSM systemUMTS: separate voice and packet data support; focus on dedicated channels
and heavy states, complicated RAN architecture and protocols due to macro diversity and QoS requirements
HSPA: improved support for packet data; emphasis on shared channels and fast radio resource management
IMS: support for IP-based services, e.g. voice (VoIP)LTE: strong packet data support (latency, throughput, control overhead),
limited state; simplified protocols; PS only, i.e. no CS core network
Transition from circuit switching to packet switching from slow, explicit setup and release of resources to fast channel-
condition- and demand-specific resource management
Advanced Mobile Communication Networks 10
Integrated Communication Systems Group
Evolution towards LTE – Architecture
• LTE radio system is a packet-only network - there is no support for circuit-switched services (no MSC)
• LTE starts on a clean state - everything is up for discussion including the system architecture and the split of functionality between Radio Access Network (RAN) and Core Network (CN)
• 3GPP (3rd Generation Partnership Program) study items • „3G Long-term Evolution” (LTE) for new Radio Access and • “System Architecture Evolution” (SAE) for Evolved Network
Advanced Mobile Communication Networks 11
Integrated Communication Systems Group
Evolution towards LTE – Architecture
GPRS Core(PacketSwitched)
SGSN
GGSN
Internet
GSMRAN
Base stationBase stationcontroller
Base station
Base station
UTRAN
Radio networkcontroller
node Bnode B
node B
MSC
PSTN
GSM Core (Circuit switched)
HLRAuCEIR
GMSC
E-e-
e-e- S-GW
P-GW
IMS
EPC
Advanced Mobile Communication Networks 13
Integrated Communication Systems Group
LTE: Evolved Packet System (EPS) Architecture
eNB
eNB
eNB
MME/S-GW MME/S-GW
X2
EPCE
-UTR
AN
S1
S1
S1S1
S1S1
X2
X2
EPC = Evolved Packet Core
Key elements of network architecture
– No more RNC– RNC layers/functionalities
moves in eNB– X2 interface for seamless
mobility (i.e. data/context forwarding) and interference management
Note: Standard only defines logical structure!
Advanced Mobile Communication Networks 14
Integrated Communication Systems Group
LTE: Requirements and Performance Targets
Advanced Mobile Communication Networks 15
Integrated Communication Systems Group
LTE Key Features (Release 8)
• Multiple access scheme– DL: OFDMA with Cyclic Prefix (CP)– UL: Single Carrier FDMA (SC-FDMA) with CP
• Adaptive modulation and coding– DL modulations: QPSK, 16QAM, and 64QAM– UL modulations: QPSK and 16QAM (optional for UE)– Rel. 6 Turbo code: Coding rate of 1/3, two 8-state constituent encoders, and
a contention-free internal interleaver
• ARQ within RLC sublayer and Hybrid ARQ within MAC sublayer
• Advanced MIMO spatial multiplexing techniques– (2 or 4) x (2 or 4) downlink and uplink supported– Multi-layer transmission with up to four streams– Multi-user MIMO also supported
• Implicit support for interference coordination
• Support for both FDD and TDD
Advanced Mobile Communication Networks 16
Integrated Communication Systems Group
Multi-antenna Solutions
Advanced Mobile Communication Networks 17
Integrated Communication Systems Group
Scheduling and Resource Allocation (1/2)
• LTE uses a scheduled, shared channel on both the uplink (UL-SCH) and the downlink (DL-SCH)
• Normally, there is no concept of an autonomous transmission; alltransmissions in both uplink and downlink must be explicitlyscheduled
• LTE allows "semi-persistent" (periodical) allocation of resources,e.g. for VoIP
Advanced Mobile Communication Networks 18
Integrated Communication Systems Group
Scheduling and Resource Allocation (2/2)
• Basic unit of allocation is called a Resource Block (RB)– 12 subcarriers in frequency (= 180 kHz)– 1 sub-frame in time (= 1 ms, = 14 OFDM symbols)– Multiple resource blocks can be allocated to a user in a given subframe
• The total number of RBs available depends on the operating bandwidth
Advanced Mobile Communication Networks 19
Integrated Communication Systems Group
Interference Coordination
Advanced Mobile Communication Networks 20
Integrated Communication Systems Group
LTE vs. WiMax vs. 3GPP2
IMS
• Authenticator• Paging Controller• Page buffering
WiMAX
Access Point
CAP-C FA/Router
• Handover Control• Radio Resource
Management• ARQ/MAC/PHY• L2 Ciphering• Classification/
ROHC
E-Node B
MME Serv GW
HSS
IMS
• Authenticator• Paging Controller• Session setup
• Handover Control• Radio Resource
Management• ARQ/MAC/PHY• L2 Ciphering• ROHC
3GPP/LTE
PDN GW
• Local mobility• Page buffering
• Local mobility• Session setup• Bearer mapping
eBTS
SRNC Access GW
AAA
IMS
• Authenticator• Paging
Controller
• Handover Control• Radio Resource
Management• ARQ/MAC/PHY• L2 Ciphering• ROHC
3GPP2/UMB
HA
PCRF
IETF-centric architectureIETF-centric architectureIETF-friendly, but still
some flavor of UMTS/GPRS – GTP, etc
• Bearer mapping
PCRF
• Local mobility• Session setup• Bearer mapping
AAA HA
Advanced Mobile Communication Networks 21
Integrated Communication Systems Group
References
LTE/SAE• A. Toskala et al, “UTRAN Long-Term Evolution,” Chapter 16 in Holma/ Toskala: WCDMA for UMTS, Wiley
2007• E. Dahlman et al, “3G Evolution, HSPA and LTE for Mobile Broadband,” Elsevier Journal, 2007• Special Issue on LTE/ WIMAX, Nachrichtentechnische Zeitung, pp. 12–24, 1/2007• 3rd Generation Partnership Project Long Term Evolution (LTE), official website:
http://www.3gpp.org/Highlights/LTE/LTE.htm• Technical Paper, “UTRA-UTRAN Long Term Evolution (LTE) and 3GPP System Architecture Evolution (SAE)”,
last update October 2006, available at: ftp://ftp.3gpp.org/Inbox/2008_web_files/LTA_Paper.pdf
Standards• TS 36.xxx series, RAN Aspects• TS 36.300, “E-UTRAN; Overall description; Stage 2”• TR 25.912, “Feasibility study for evolved Universal Terrestrial Radio Access (UTRA) and Universal Terrestrial
Radio Access Network (UTRAN)”• TR 25.814, “Physical layer aspect for evolved UTRA”• TR 23.882, “3GPP System Architecture Evolution: Report on Technical Options and Conclusions”
Self-organizing networks and LTE• Self-organizing networks and LTE, http://www.lightreading.com/document.asp?doc_id=158441• NGMN Recommendation on SON and O&M Requirements, Dec. 5, 2008, NGMN,
http://www.ngmn.org/uploads/media/NGMN_Recommendation_on_SON_and_O_M_Requirements.pdf