Mobile Network Evolution – Part 2 · Mobile Network Evolution – Part 2 From UMTS to LTE or How to Further Increase Network Capacity and QoS ... LTE vs. WiMax vs. 3GPP2 IMS •

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



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



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



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



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



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?



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.



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



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



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



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



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!



LTE: Requirements and Performance Targets



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



Multi-antenna Solutions



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



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



Interference Coordination



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


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


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



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

Documents

Mobile Network Evolution – Part 2 · Mobile Network Evolution – Part 2 From UMTS to LTE or How to Further Increase Network Capacity and QoS ... LTE vs. WiMax vs. 3GPP2 IMS •