Csfb vs Ecsfb

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Interworking with LTE

Source:

Mike Dolan Tony LeeChair, TSG-X.5 PDS Chair, TSG-C.2.2

Alcatel-Lucent VIA [email protected] [email protected]


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June 14, 2012 cdma2000 Technology Workshop广州 Slide 2

Interworking with LTE

Outline

• At the CORE and RAN Level – LTE eHPRD

• How eHRPD connects to the same Enhanced Packet Core (EPC)

• Handoff

–LTE cdma2000

®

1x• CSFB, eCSFB

• SMS

• At the RADIO Level – LTE eHPRD

– eHPRD LTE

– Circuit Switch Fall Back

– Registration

– SMS



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Why Interwork between

LTE and 1x/eHRPD?

Simply:

• CDMA operators need a smooth transition path

to take their subscribers to LTE technology. – Keep subscribers happy – Offer subscribers new features

– Manage competition from other operators

– Optimize the use of their spectrum

–Take greatest advantage of their installed infrastructure whileupgrading to LTE


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LTE eHPRD

How eHRPD connects to the same Enhanced Packet Core (EPC)

PDN

Gateway

Serving

GatewayMME

eNodeB

HSS/AAA

Home

Agent

Internet

HSGWPDS

N

eAN/

ePCF

AN/

PCF

PCRF

3GPP2

AAA

Signaling

Data

UE


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Non-Optimized Handoff from

LTE to eHRPD

MME

HSS/AAA Internet

PCRF

Signaling

Data

UE

PDN

Gateway

Serving

Gateway

eNodeB

HSGW

eAN/

ePCF


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HSS/AAA Internet

PCRF

Signaling

Data

U

E

S101

Optimized Handoff

from LTE to eHRPD Step 1: Establish context on eHRPD via tunneled signaling

PDN

Gateway

eNodeB

Serving

GatewayMME HSGW

eAN/

ePCF


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Optimized Handoff

from LTE to eHRPD Step 2: UE moves to eHRPD, bearers are moved

HSS/AAA Internet

PCRF

Signaling

Data

UE

S101

PDN

Gateway

Serving

Gateway

eNodeB

HSGW

eAN/

ePCF

MME


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Comparison of Optimized

vs. Non-Optimized

• Optimized handoff takes less than 300 msec.

• Non-optimized handoff can take as much as 5-7seconds.

• Optimized handoff requires in addition to whatnon-optimized needs: –

S101 tunneling – Upgrades on the UE, MME, eAN/ePCF, HSGW


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Circuit Switched Fall Back (CSFB)Core Network and RAN

• Uses tunneled signaling to the UE across

the S102 interface between the IWS and

MME. This supports: – CSFB, enhanced CSFB (eCSFB)

– SMS


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CSFB

• Page sent to IWS.

• IWS sends page to UEvia MME and eNodeBusing S102.

• UE moves to 1x.

• UE sends a normalpage response on the

1x access channel.• Call proceeds.

IWS

1x BS

Signaling

Data

UE

MSC

S102

eNodeB

MME


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eCSFB

• Page sent to IWS.

• IWS sends page to UE viaMME and eNodeB usingS102.

• UE sends a pageresponse via the eNodeBand MME using S102.

• IWS sends a handoffcommand (UHDM) to theUE via S102, and sets upthe traffic channel on 1x inpreparation for the UE.

• UE does a handoff to the1x traffic channel.

• 1x call proceeds.

IWS

1x BS

Signaling

Data

UE

MSC

S102

eNodeB

MME


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Comparison of CSFB to

eCSFB

• CSFB requires extra time on 1x due to hashing

and other procedures.

• For eCSFB, the traffic channel is prepared andwaiting for the UE to arrive.

•

Some issues at the radio level will be discussedlater, when the radio level is covered.


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SMS

•MT-SMS – SMS are sent via S102

to the UE

– UE does not leave LTE.

• MO-SMS – SMS are sent via S102

from the UE – UE does not leave LTE.

IWS

1x BS

Signaling

Data

UE

MSC

S102

Both mobile-originated and

mobile-terminated are supported.

eNodeB

MME


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Radio Level



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LTE-eHRPD Protocol

Structure

LTE-HRPD multi-mode AT LTE-eNB HRPD RNC

Connection

Layer

Protocols

LTE-PHY

LTE-MAC

LTE-RRC

LTE-PHY

LTE-MAC

LTE-RRC

HRPD-

Security

HRPD-MAC

HRPD-PHY

LTE-MME

LTE-

S1

LTE-

S1

LTE-

S101

LTE-

S101

HRPD-Stream

Protocol

HRPD-

Signaling

Network

Protocol

Radio

Link

Protocol

HRPD-

Signaling

Link Protocol

HRPD-Stream

Protocol

HRPD-

Signaling

Network

Protocol

Radio

Link

Protocol

HRPD-

Signaling

Link Protocol

Connection Layer

Protocols

HRPD-

Security

HRPD-MAC

HRPD-PHY

S1-AP S101

LTE-Uu


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Air Interface Protocol

Enhancements

•New protocols to support LTE to eHRPD handover

–

Default Signaling Adaptation Protocol –Inter-RAT Initialization, Idle State, Route Update,

Overhead Message, and Signaling Adaptation Protocols

–Support for C.S0024-B

•Some existing protocols were also affected.•Documented in C.S0087


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June 14, 2012 cdma2000 Technology Workshop广州

Slide 17

Changes to the

Application Layer

• Added alternate packet application subtype for:

–

MFPA -> Alternate MFPA –EMFPA -> Alternate EMFPA

–MLMFPA -> Alternate MLMFPA

•The alternate packet application subtype is to

identify the support of eHRPD


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Slide 18

eHRPD to LTE

Two methods available:

• OtherRATNeighborList Message

–

Broadcasted message – Contains E-UTRAN information for AT to search for E-

UTRAN system

– Threshold

•InterRATRedirect – Contains E-UTRAN redirection information


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Slide 19

3. OtherRATMeasurementRequest

4. OtherRATMeasurementReport

6. InterRATRedirect

eHRPD

ANeAT

1. AT active on eHRPD

8. UE performs Handoff/Attach to E-UTRA

E-UTRA

9. Search more E-UTRA channel or go back to eHRPD

based on MMSS rules (conditional)

5. The eAN decides

to redirect the eAT

7. The eAT retunes

to E-UTRA

2. The eAN decides

to determine E-

UTRA Availability

eHRPD E-UTRAN

inter-RAT redirection


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Slide 20

LTE to 1x tunneling

Lower Layer

(Other Access

Technology)

Lower Layer (Other

Access Technology)Lower Layer Lower Layer

Other Access TechnologyEntity(ies)

Lower Layer

(Other Access

Technology)

Lower Layer (Other

Access Technology)Lower Layer Lower Layer

MS IWS

1x

Layer 3

PDU

1x

Layer 3

PDU

GCSNA

Control

TLAC

Header

GCSNAHeader

GCSNA

Control

TLAC

Header

GCSNAHeader

S102 Tunnel


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Slide 21

1x to LTE

• OtherRATNeighborList Message

– Broadcasted message

–

Contains E-UTRAN information for AT to search for E-UTRAN system

– Threshold


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22

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Slide 23

cdma2000® is the trademark for the technical nomenclaturefor certain specifications and standards of the OrganizationalPartners (OPs) of 3GPP2. Geographically (and as of the date

of publication), cdma2000® is a registered trademark of theTelecommunications Industry Association (TIA-USA) in theUnited States.


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Slide 25

Signaling Adaptation

Protocol Context


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Slide 26

SAP functionalities

• Records the current air interface (HRPD or non-HRPD)

• Provides a virtual connection service between the access

terminal and the access network over the S101 tunnel• Provides encapsulation of HRPD packets over S101

• Triggers idle and active handoffs from LTE to eHRPD

• It has a control plane as well as a user plane functionality


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Slide 27

Changes to MAC and PHY

Layer

• Initial output power calculation

–X0 = - Mean RX Power (dBm) + OpenLoopAdjust + PilotInitialAdjust

where:PilotInitialAdjust = InitialAdjust + min(PilotStrengthCorrectionMax,

max(PilotStrengthNominal – PilotStrength, PilotStrengthCorrectionMin)),

–This is necessary due to lack of access probe power correction.


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Slide 29

Interworking with LTERadio Level

• LTE eHPRD non-optimized handoff

– S-101 interface is not used.


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LTE 1x Tunneling

on S102

• Supports:

– Circuit Switch Fall Back (CSFB) – Enhanced CSFB (eCSFB)

– SMS, mobile-originated and mobile-

terminated

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Csfb vs Ecsfb