Interworking with LTE Source: Mike Dolan Tony Lee Consulting Member of Technical StaffPrincipal Engineer Alcatel-LucentVIA Telecom

Interworking with LTE

Source: Mike Dolan Tony LeeConsulting Member of Technical Staff Principal EngineerAlcatel-Lucent VIA [email protected] [email protected]

June 14, 2012 cdma2000 Technology Workshop 广州 Slide 2

Interworking with LTE

• 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



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 while

upgrading to LTE


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

PDN Gateway

Serving GatewayMME

eNodeB

HSS/AAA

Home Agent

Internet

HSGW PDSN

eAN/ePCF

AN/PCF

PCRF

3GPP2 AAA

Signaling

Data

UE


Non-Optimized Handoff from LTE to eHRPD

MME

HSS/AAA Internet

PCRF

Signaling

Data

UE

PDN Gateway

Serving Gateway

eNodeB

HSGW

eAN/ePCF


HSS/AAA Internet

PCRF

Signaling

Data

UE

S101

Optimized Handofffrom LTE to eHRPD

Step 1: Establish context on eHRPD via tunneled signaling

PDN Gateway

eNodeB

Serving GatewayMME HSGW

eAN/ePCF


Optimized Handofffrom 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


Comparison of Optimized vs. Non-Optimized

• Optimized handoff takes less than 300 msec.• Non-optimized handoff can take as much as 5-7

seconds.

• Optimized handoff requires in addition to what non-optimized needs:– S101 tunneling– Upgrades on the UE, MME, eAN/ePCF, HSGW


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


CSFB

• Page sent to IWS.• IWS sends page to UE

via MME and eNodeB using S102.

• UE moves to 1x.• UE sends a normal

page response on the 1x access channel.

• Call proceeds.

IWS

1x BS

Signaling

Data

UE

MSC

S102

eNodeB

MME


eCSFB

• Page sent to IWS.• IWS sends page to UE via

MME and eNodeB using S102.

• UE sends a page response via the eNodeB and MME using S102.

• IWS sends a handoff command (UHDM) to the UE via S102, and sets up the traffic channel on 1x in preparation for the UE.

• UE does a handoff to the 1x traffic channel.

• 1x call proceeds.

IWS

1x BS

Signaling

Data

UE

MSC

S102

eNodeB

MME


Comparison of CSFB to eCSFB

• CSFB requires extra time on 1x due to hashing and other procedures.

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

• Some issues at the radio level will be discussed later, when the radio level is covered.


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

Radio Level



LTE-eHRPD Protocol Structure

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

ConnectionLayer

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-StreamProtocol

HRPD-SignalingNetworkProtocol

Radio Link

Protocol

HRPD-Signaling

Link Protocol

HRPD-StreamProtocol

HRPD-SignalingNetworkProtocol

Radio Link

Protocol

HRPD-Signaling

Link Protocol

Connection Layer Protocols

HRPD-Security

HRPD-MAC

HRPD-PHY

S1-AP S101

LTE-Uu

June 14, 2012 cdma2000 Technology Workshop 广州

Slide 16

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


Changes to theApplication 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


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


3. OtherRATMeasurementRequest

4. OtherRATMeasurementReport

6. InterRATRedirect

eHRPDANeAT

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


LTE to 1x tunneling

Lower Layer (Other Access Technology)

Lower Layer (Other Access Technology) Lower Layer Lower Layer

Other Access Technology Entity(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 HeaderGCSNA Header

GCSNA Control

TLAC HeaderGCSNA Header

S102 Tunnel


1x to LTE

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

UTRAN system– Threshold


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

of publication), cdma2000® is a registered trademark of the Telecommunications Industry Association (TIA-USA) in the

United States.

Backup


Signaling Adaptation Protocol Context


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


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.


Interworking with LTERadio Level

• LTE eHPRD non-optimized handoff– S-101 interface is not used.– Idle handoff from LTE to eHRPD– LTE SIB8 provides information on nearby

eHRPD cells


Interworking with LTERadio Level

• LTE eHPRD non-optimized handoff– S-101 interface is not used.


LTE 1x Tunnelingon S102

• Supports:– Circuit Switch Fall Back (CSFB)– Enhanced CSFB (eCSFB)– SMS, mobile-originated and mobile-

terminated

Interworking with LTE Source: Mike Dolan Tony Lee Consulting Member of Technical StaffPrincipal Engineer Alcatel-LucentVIA Telecom

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