August 2012

C2 – Company Confidential

SOURCE: Alcatel-Lucent: Jialin Zou, Satish Kanugovi, Orlett Pearson

jialin.zou@, satish.k (@alcatel-lucent.com)

Qualcomm, Inc.: Jun Wang, Wentao Zhang, George Cherian, Jen Chen jwang, wentaoz (@qti.qualcomm.com)

ABSTRACT: UE class and randomization based scheme is proposed for idle traffic redistribution from eHRPD to LTE.

TITLE:

TSG-C

RECOMMENDATION: Discuss and adopt.

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UE Class and Randomization Based Idle Reselection

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Load Balancing between eHRPD and E-UTRAN

Background Requirement from China Telecom at Nanjing meeting, refer to [C22-

20120206-020 CT-Requirement for loading balance between eHRPD and E-UTRAN].

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High Level Design

Load Balance Control Between eHRPD and LTE Controlled by UEClass

The operator can control which UE class(es) should transition from eHRPD to LTE Controlled by randomization procedures

When UE Class based load balance doesn’t fully solve load balance need

Interaction with existing idle-mode reselection mechanism defined in C.S0087 If the UE is set to go to LTE, the UE will set the serving frequency priority to

be the lowest If the UE is set to stay in eHRPD, the UE will set the serving frequency

priority to be the highest The rest follows the existing idle-mode reselection procedures

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UEClass Definition and Provision

A new attribute UEClass is proposed UEClass is created from subscription data or operator/vendor-based policy,

could be specified by the network during initial call setup

When network detects its loading problem: eAN broadcasts inter-RAT reselection rules using UEClass bitmap to the UEs

through overhead signaling

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UEClass Bitmap Concept

UEs can be divided in 8 classes per operator policy UEClass_k indicator (k=1, 2,..,8), 1 bit for each UE class

UEClass_k=0 means eAN indicates UEs of class k stay in eHRPD UEClass_k=1 means eAN indicates UEs of class k go to EUTRAN

UEClass_8 indicator

1 Bit

… … UEClass_2 indicator

UEClass_1 indicator

1 Bit 1 Bit 1 Bit

UEClass reselection indicator

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Example: UE’s Behavior without Randomization

UE1UE2

UE3UE4UE5

UE6UE7UE8UE9

UEClass 1

UEClass 2

UEClass 3

indicates UEClass 1,2 stay in eHRPD, indicates UEClass 3 go to EUTRAN

LTE eNodeBeHRPD AN

UE1UE2

UEClass 1

UEClass 2

LTE eNodeBeHRPD AN

UE3UE4UE5

UE6UE7UE8UE9

UEClass 3

time

In addition to UEClass reselection indicator, 1 bit randomization indicator is introduced to control if multi-carriers randomization is enabled UEClass bitmap(s) indicate(s) whether some UE classes go to EUTRAN or stay in eHRPD. If

redirected to EUTRAN, multi-carriers randomization may be enabled.

It is desirable to consider multi-carrier randomization with the impacts of legacy UEs Therefore, a new set of LTE frequency probability parameter is introduced (with the probability of stay

with serving derived) for new UEs to allow the operator to better control load balance

If UE is indicated not using randomization procedures: If UE is indicated go to EUTRAN, the UE shall set eHRPD serving priority to lowest and follow existing

reselection procedure.

If UE is indicated to stay in eHRPD, it will ignore randomization bit value, set eHRPD serving priority as highest and follow existing reselection procedure.

If UE is indicated using randomization procedures: If UE is indicated go to EUTRAN and randomization bit is set to 1, the UE shall follow multi frequency

reselection procedure.

If UE is indicated to stay in eHRPD, it will ignore randomization bit value, set eHRPD serving priority as highest and follow existing reselection procedure.

No matter whether UEClass bitmap is broadcasted or not, all legacy UEs will follow existing reselection procedure.

Randomization Procedures

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UEClass_k indicator (YELLOW), 1 bit for each UE class UEClass_k=0 means eAN indicates UEs of class k stay in eHRPD UEClass_k=1 means eAN indicates UEs of class k go to EUTRAN

Randomization Indicator (RED): 1 bit for all UE Classes Randomization _indicator=0 means UEs of all class shall not be randomized Randomization _indicator=1 means UEs of all class shall be randomized

LTE Multicarrier Randomization probability (BLUE): 3 bits for each LTE carrier Notifies new UEs the probability of each LTE carrier for randomization and load balance

and a UE reselects to the carrier at that probability A UE will stay with CDMA at a probability = 1 – Sum of LTE carrier probabilities

Only present when Randomization _indicator=1

Message Format

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UEClass_8 indicator

3 Bits 1 Bit

… … UEClass_2 indicator

Randomization

_indicator

UEClass_1 indicator

1 Bit 1 Bit 1 Bit

UEClass reselection indicator randomization indicator

LTE F1 probability

LTE F2 probability … … LTE FK

probability

LTE Multicarrier probabilities

3 Bits 3 Bits

If UEClass k UEs are redirected to EUTRAN(UEClass_k=1) randomization indicator set to 1, the UE performs the following procedures: UE derive the Serving Probability = 1 – sum of all the LTE carrier probabilities The UE randomly generates a UEReselectionProbability (URP) over the range of

(0~1) showing in the following diagram as an example If URP value falls into interval Tk of the following figure, then UE selects the

carrier k with associated probability Probk

If serving probability = 0, then all UEs select one of the available LTE carriers If serving probability is NOT ZERO, then UEs in interval T1 stay back in serving HRPD system

If the selected carrier signal is weak, then UE sets the selected carrier priority to lowest and follows existing idles reselection procedure

Probability Based Multi-Carrier Randomization

Here Probserving+Prob1+Prob+ …+ProbN=1Probability value

0 Probserving Probserving+Prob1 Probserving +Prob2 +Prob1

… ….

1

Interval T1 Interval T2 Interval T3 Interval TN

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Assume eAN broadcasts three LTE carriers with probabilities 0.2(F1), 0.3(F2) and 0.5(F3), eHRPD probability=0 .

Assume eAN broadcast three LTE carriers with priorities 3 (F1), 6 (F2) and 4 (F3) in OtherRATNeighbor message.

Example 1: Assume UE generated URP value is 0.1 , then If F1 signal is good, UE goes to F1 If F1 signal is weak, UE performs existing idle reselection procedure w/

F2(priority=6) first, then F3(priority=4)

Example 2: Assume UE generated URP value is 0.4, then If F2 signal is good, UE goes to F2 If F2 signal is weak, UE performs existing idle reselection procedure w/

F3(priority=4) first, then F1(priority=3)

Examples

10Probability value0 0.2 0.2+0.3 1

F1 Interval T1 F2 Interval T2 F3 Interval T3

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Recommendation

Adopt eHRPD-LTE load balance mechanism controlled by UEClass as specified in this document

Consider multiple LTE carrier randomization with impacts of legacy UEs proposed in this document

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Thanks