2 WCDMA RAN12 Handover Algorithm and Parameters ISSUE1.02

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Confidential Information of Huawei. No Spreading Without Permission

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Handover is a basic function of the cellular mobile network. The purpose of

handover is to ensure that a UE in CELL_DCH state is served continuously

when it moves.

With the development of WCDMA network, more and more users join in the

system. Using Handover can achieve load balance between carriers and fully

utilizes system resources.

HCS: Hierarchical Cell Structure.

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Handover types supported by UMTS:

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Active set: A set of cells simultaneously involved in a specific communication

service between the UE and the UTRAN.

Monitored set: A set of cells included in the CELL_INFO_LIST, but do not

belong to the active set.

Detected set: A set of cells detected by the UE, and do not included in the

CELL_INFO_LIST.

RL: Radio link between NodeB and UE.

RLS: All radio links from the same NodeB consist of a radio link set.

Combination way: For soft handover, the uplink signals are combined in RNC.

The RNC will select one best signal to process. We call this selective

combination. For softer handover, the uplink signals are combined in the RAKE

receiver of NodeB. It is maximum ratio combination.

Soft handover gain: Please refer to the WCDMA Coverage Planning course.

PCPICH: Primary Common Pilot Channel. UE measures the signal strength of

PCPICH for handover decision.

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Intra-frequency handover is of the following two types:

Intra-frequency soft handover: means that multiple radio links are

connected to the UE at the same time.

Intra-frequency hard handover: means that only one radio link is

connected to the UE at the same time.

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The maximum number of RL in the active set is 3 by default. And This

parameter can be changed in the RNC. But this function need the UE to support.

Normally, the active set supported by UE is fixed 3 and can not be changed.

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Intra-frequency soft handover is characterized by the function that the UE can

be connected to multiple Universal Terrestrial Radio Access Network (UTRAN)

access points at the same time. Addition and/or release of radio links are

controlled by the ACTIVE SET UPDATE procedure.

The HO_INTRA_FREQ_SOFT_HO_SWITCH parameter in the SET

CORRMALGOSWITCH command is used to determine whether to enable both

soft handover and softer handover. By default, this switch is set to ON,

indicating that both soft handover and softer handover are enabled.

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During softer handover, the uplink signaling are combined in NodeB by

maximum ratio combination, but during soft handover they are combined in

RNC by selective combination.

Compare to later one, the maximum ratio combination can get more gain. So

the performance of maximum ratio combination is better.

Since softer handover is completed in NodeB, it do not consume more transport

resource of Iub.

In telecommunications, maximal-ratio combining is a method of diversity

combining in which:

(a) the signals from each channel are added together,

(b) the gain of each channel is made proportional to the rms signal level and

inversely proportional to the mean square noise level in that channel.

(c) different proportionality constants are used for each channel. It is also known

as ratio-squared combining and combining. Maximal-ratio-combining is the

optimum combiner for independent AWGN channels.

http://en.wikipedia.org/wiki/Telecommunication

http://en.wikipedia.org/wiki/Diversity_combining

http://en.wikipedia.org/wiki/Diversity_combining

http://en.wikipedia.org/wiki/Channel_(communications)

http://en.wikipedia.org/wiki/Gain

http://en.wikipedia.org/wiki/Proportionality_(mathematics)

http://en.wikipedia.org/wiki/Signal_level

http://en.wikipedia.org/wiki/Noise_level

http://en.wikipedia.org/wiki/Additive_white_Gaussian_noise

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Compared with soft handover, intra-frequency hard handover uses fewer

resources. The scenarios of intra-frequency hard handover are as follows:

No Iur interface is present between RNCs. In this scenario, intra-

frequency hard handover instead of soft handover can be performed

between two RNCs.

The Iur interface is congested between RNCs. In this scenario, also

intra-frequency hard handover instead of soft handover can be

performed between two RNCs.

There is a high-speed Best Effort (BE) service. Compared with soft

handover, intra-frequency hard handover is used to save downlink

bandwidth for a high-speed BE service.

The intra-frequency soft handover fails and intra-frequency hard

handover is allowed. When intra-frequency soft handover fails because

of a congestion problem of the target cell, the RNC tries an intra-

frequency hard handover with a lower service bit rate.

The HO_INTRA_FREQ_HARD_HO_SWITCH parameter in the SET

CORRMALGOSWITCH command is used to determine whether to enable intra-

frequency hard handover. By default, this switch is set to ON.

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The intra-frequency handover procedure is divided into three phases: handover

measurement, handover decision, and handover execution.

After the UE transits to the CELL_DCH state in connected mode during a call,

the RNC sends a MEASUREMENT CONTROL message to instruct the UE to

take measurements and report the measurement event results. Upon the

reception of an event report from the UE, the RNC makes a handover decision

and performs the corresponding handover.

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The MEASUREMENT CONTROL message carries the following information:

Event trigger threshold

Hysteresis value

Event trigger delay time

Neighboring cell list

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MNew is the measurement value of the cell in the reporting range.

CIONew is equal to the sum of CIO and CIOOffset, which adjusts the cell

boundary in the handover algorithms. To facilitate handover in neighboring cell

configuration, the parameter is set as a positive value; otherwise, the parameter

is set as a negative value.

W represents Weighted factor, which is determined by the parameter Weight.

The total quality of the best cell and the active set is specified by W.

Mi is the measurement value of a cell in the active set.

NA is the number of cells not forbidden to affect the reporting range in the active

set. The parameter CellsForbidden1A indicates whether adding the cell to the

active set affects the relative threshold of event 1A.

MBest is the measurement value of the best cell in the active set.

R1a is the reporting range or the relative threshold of soft handover. The

threshold parameters of the CS non-VP service, VP service, and PS service are

as follows:

IntraRelThdFor1ACSVP

IntraRelThdFor1ACSNVP

IntraRelThdFor1APS

H1a represents 1A hysteresis, the hysteresis value of event 1A.

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The above figure shows the triggering of event 1A. In this procedure, the default

parameter values are used.

If the signal quality of a cell that is not in the active set is higher than Th1A for a

period of time specified by TrigTime1A (that is, Time to trigger in the figure), the

UE reports event 1A.

Th1A = (CPICH Ec/No of the best cell in the active set) - (reporting range for

event 1A)

If Weighted factor > 0, then Th1A = (general signal quality of all the cells in the

active set) - (reporting range for event 1A).

Reporting range for event 1A is equal to the value of IntraRelThdFor1ACSVP,

IntraRelThdFor1ACSNVP, or IntraRelThdFor1APS.

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CIO

Content: This parameter works with the Neighboring cell oriented CIO. It

is used for intra- or inter-frequency handover decisions. The larger the

sum, the higher the handover priority of the neighboring cell. The smaller

the sum, the lower the handover priority of the neighboring cell. Usually it

is configured to 0.

Value range: -20~20

Physical value range: -10~10; step: 0.5

Physical unit: dB

Set this parameter through ADD CELLSETUP/MOD CELLSETUP.

CIOOffset

Content: This parameter defines the neighboring cell oriented cell

individual offset. The set value functions in combination of the cell

oriented CIO. Their sum is added to the measurement quantity before

the UE evaluates whether an event has occurred. In handover

algorithms, this parameter is used for moving the border of a cell.

Value range: -20~20

Physical value range: -20~20; step: 1

Physical unit: dB

Set this parameter through ADD INTRAFREQNCELL/MOD

INTRAFREQNCELL.

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IntraRelThdFor1ACSNVP/IntraRelThdFor1ACSVP/IntraRelThdFor1APS

Content: These parameters specify the CS non-VP/VP and PS services

relative threshold of event 1A. The higher the threshold is, the more

easily the target cell joins the active set, the harder the call drops, the

larger the ratio of the UE involved in soft handover is, but the more the

use of forward resources is. The lower the threshold is, the more difficult

the target cell joins the active set. Thus the communication quality and

the smooth handover cannot be guaranteed.

Value range: 0~29

Physical value range: 0~14.5; step: 0.5

Physical unit: dB

Set these parameters through SET INTRAFREQHO/ADD

CELLINTRAFREQHO/MOD CELLINTRAFREQHO.

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Hystfor1A

Content: This parameter specifies the hysteresis value for event 1A. The value of this

parameter correlates with slow fading. The larger the value of this parameter, the less

possibility of ping-pong effect or wrong decision. But the event might not be triggered in

time.

Value range: 0~15


Physical unit: dB

TrigTime1A

Content: This parameter specifies the time delay to trigger event 1A. The value of this

parameter correlates with slow fading. The larger the value of this parameter, the lower

the incorrect decision probability, but the slower the response of the event to

measurement signal change.

Value range: D0, D10, D20, D40, D60, D80, D100, D120, D160, D200, D240, D320,

D640, D1280, D2560, D5000

Physical value range: 0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240, 320, 640, 1280,

2560, 5000

Physical unit: ms

Weight

Content: This parameter is used to define the soft handover relative threshold based on

the measured value of each cell in the active set. The greater the parameter value, the

higher the soft handover relative threshold. When this value is set to 0, the soft handover

relative threshold is determined only by the best cell in the active set.

Value range: 0~20

Physical value range: 0~2; step: 0.1

Set these parameters through SET INTRAFREQHO/ADD CELLINTRAFREQHO/MOD

CELLINTRAFREQHO.

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The report mode of 1A is event trigger report.

Generally the event 1A is reported only once. However, to avoid measurement

report loss, the event 1A reporting can be turned to periodical reporting.

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ReportIntervalfor1A

Content: This parameter specifies the reporting period of event 1A. That

is, event 1A is reported at each reporting interval. Usually, event 1A is

reported only once. Nevertheless, if the cell, where event 1A is reported,

does not join the active set in a specified period of time, the UE can

change the reporting of event 1A into periodical mode to avoid missing

of measurement reports. The event 1A of this cell is reported for

PeriodMRReportNumfor1A times with the reporting interval as the set

value.

Value range: NON_PERIODIC_REPORT, D250, D500, D1000, D2000,

D4000, D8000, D16000

Physical value range: NON_PERIODIC_REPORT, 250, 500, 1000, 2000,

4000, 8000, 16000

Physical unit: ms

PeriodMRReportNumfor1A

Content: This parameter specifies the number of reporting times of event

1A for periodical reporting. When the actual reporting times exceeds the

set value, the periodical reporting ends.

Value range: D1, D2, D4, D8, D16, D32, D64, INFINITY

Physical value range: 1, 2, 4, 8, 16, 32, 64, INFINITY



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MOld is the measurement value of the cell that becomes worse.

CIOOld is equal to the sum of CIO and CIOOffset, which is the offset between

the cell in the reporting range and the best cell in the active set.

W represents Weighted factor, used to weight the quality of the active set. The

total quality of the best cell and the active set is specified by the parameter

Weight.

Mi is the measurement value of a cell in the active set.

NB is the number of cells not forbidden to affect the reporting range in the active

set. The parameter CellsForbidden1B indicates whether adding the cell to the

active set affects the relative threshold of event 1B.


R1b is the reporting range or the relative threshold of soft handover. The

threshold parameters of the CS non-VP service, VP service, and PS services

are as follows:

IntraRelThdFor1BCSVP

IntraRelThdFor1BCSNVP

IntraRelThdFor1BPS

H1b is the hysteresis value of event 1B, which is determined by the parameter

Hystfor1B.

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The above figure shows the triggering of event 1B. In this procedure, the default


If the signal quality of a cell in the active set is lower than Th1B for a period of

time specified by TrigTime1B (Time to trigger in the figure), the UE reports

event 1B.

Th1B = (CPICH Ec/No of the best cell in the active set) - (reporting range for

event 1B)

If Weight > 0, then Th1B = (general signal quality of all the cells in the active set)

- (reporting range for event 1B).

Reporting range for event 1B is equal to the value of IntraRelThdFor1BCSVP,

IntraRelThdFor1BCSNVP, or IntraRelThdFor1BPS.

Configuration rule and restriction:

The value of IntraRelThdFor1BCSNVP has to be larger than that of

IntraRelThdFor1ACSNVP.

The value of IntraRelThdFor1BCSVP has to be larger than that of

IntraRelThdFor1ACSVP.

The value of IntraRelThdFor1BPS has to be larger than that of

IntraRelThdFor1APS.

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IntraRelThdFor1BCSNVP/IntraRelThdFor1BCSVP/IntraRelThdFor1BPS

Content: These parameters specify the CS non-VP/VP and PS services

relative threshold of event 1B. The lower the threshold is, the more

easily the event 1B is triggered. The higher the threshold is, the harder

the event 1B is triggered.

Value range: 0~29


Physical unit: dB



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Hystfor1B

Content: This parameter specifies the hysteresis value for event 1B. The

value of this parameter correlates with slow fading. The larger the value

of this parameter, the less possibility of ping-pong effect or wrong

decision. But the event might not be triggered in time.

Value range: 0~15


Physical unit: dB

TrigTime1B

Content: This parameter specifies the time delay to trigger event 1B. The


of this parameter, the lower the incorrect decision probability, but the

slower the response of the event to measurement signal change.

Value range: D0, D10, D20, D40, D60, D80, D100, D120, D160, D200,

D240, D320, D640, D1280, D2560, D5000

Physical value range: 0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240, 320,

640, 1280, 2560, 5000

Physical unit: ms



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MNew is the measurement value of the cell in the reporting range.

CIONew is the cell individual offset value of the cell in the reporting range. It is

equal to the sum of CIO and CIOOffset, which is the offset between the cell in

the reporting range and the best cell in the active set.

MInAS is the measurement value of the worst cell in the active set.

H1c is the hysteresis value of event 1C, which is determined by the parameter

Hystfor1C.

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The above figure shows the triggering of event 1C. In this procedure, the default


If the signal quality of a cell not in the active set is higher than Th1C for a period

of time specified by TrigTime1C (Time to trigger in the figure), the UE reports

event 1C, as shown in the figure.

Th1C = (CPICH Ec/No of the worst cell in the active set) + (Hystfor1C/2)

The UE reports event 1C for qualified cells after the number of cells in the active

set reaches the maximum value. The maximum number of cells in the active set

can be set by the MaxCellInActiveSet parameter.

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Hystfor1C

Content: This parameter specifies the hysteresis value for event 1C. The




Value range: 0~15


Physical unit: dB

TrigTime1C

Content: This parameter specifies the time delay to trigger event 1C. The





D240, D320, D640, D1280, D2560, D5000


640, 1280, 2560, 5000

Physical unit: ms



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The report mode of 1C is event trigger report.

Generally the event 1C is reported only once. However, to avoid measurement

report loss, the event 1C reporting can be turned to periodical reporting.

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ReportIntervalfor1C


1C for periodical reporting. That is, event 1C is reported at each

reporting interval. Usually, event 1C is reported only once. Nevertheless,

if the cell, where event 1C is reported, does not join the active set in a

specified period of time, the UE can change the reporting of event 1C

into periodical mode to avoid missing of measurement reports. The

event 1C of this cell is reported for PeriodMRReportNumfor1C times with

the reporting interval as the set value.


D4000, D8000, D16000


4000, 8000, 16000

Physical unit: ms

PeriodMRReportNumfor1C


1C for periodical reporting. When the actual reporting times exceeds the






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MNotBest is the measurement value of a cell that is not the best cell.

CIONotBest is equal to the sum of CIO and CIOOffset, which is the offset

between the cell in the reporting range and the best cell in the active set.


CIOBest is the cell individual offset value of the best cell. This parameter is not

used for event 1D.

H1d is the hysteresis value of event 1D, which is determined by the parameter

Hystfor1D.

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The above figure shows the triggering of event 1D. In this procedure, the default


If the signal quality of a cell not in the active set is higher than Th1D for a period

of time specified by TrigTime1D (Time to trigger in the figure), the UE reports

event 1D.

Th1D = (CPICH Ec/No of the best cell in the active set) + (Hystfor1D/2)

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Hystfor1D

Content: This parameter specifies the hysteresis value for event 1D. The




Value range: 0~15


Physical unit: dB

TrigTime1D

Content: This parameter specifies the time delay to trigger event 1D. The





D240, D320, D640, D1280, D2560, D5000


640, 1280, 2560, 5000

Physical unit: ms



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MNew is the measurement result of the cell not in the E-DCH active set but in

the DCH active set.

CIONew and CIOInAS refer to the offset of each cell.

MInAS is the measurement result of the cell in the E-DCH active set with the

lowest measurement result.

H1J is the hysteresis parameter for event 1J and is determined by Hystfor1J.

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The above figure shows the triggering of event 1J. In this procedure, the

hysteresis and the cell individual offsets for all cells equal 0.

If the signal quality of a cell not in the E-DCH active set is higher than Th1J for a

period of time specified by TrigTime1J (Time to trigger in the figure), the UE

reports event 1J.

Th1J = (CPICH Ec/No of the worst cell in the active set) + (Hystfor1J/2)

The first measurement report is sent when primary CPICH D becomes better than

primary CPICH B. The "cell measurement event result" of the measurement report

contains the information of primary CPICH D and CPICH B.

On the assumption that the E-DCH active set has been updated after the first

measurement report (E-DCH active set is now primary CPICH A and primary CPICH D),

the second report is sent when primary CPICH C becomes better than primary CPICH A.

The "cell measurement event result" of the second measurement report contains the

information of primary CPICH C and primary CPICH A.

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The characteristics of 1J event:

3GPP define the maximum DCH active set size is 6 and the maximum E-DCH

active set size is 4.

The DCH active set covers the E-DCH active set or they are the same.

The best cell in E-DCH active set should be the same as that in DCH active set.

Uplink channel type of UE is decided by the best cell in DCH active set:

Uplink channel is E-DCH if the best cell in DCH active set supports

HSUPA.

Uplink channel is DCH if the best cell in DCH active set can NOT

support HSUPA.

Processing procedure of 1J event:

The UE reports 1J event if it find a non-active E-DCH but active DCH cell

PCICH becomes better than an active E-DCH PCIPCH.

RNC will add the target cell into E-DCH active set if the E-DCH active set is

NOT full.

RNC will perform replace procedure if the E-DCH active set is full.

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Hystfor1J

Content: This parameter specifies the hysteresis value for event 1J. The value of this

parameter correlates with slow fading. The larger the value of this parameter, the less

possibility of ping-pong effect or wrong decision. But the event might not be triggered in

time.

Value range: 0~15


Physical unit: dB

Set this parameter through SET INTRAFREQHO/ADD CELLINTRAFREQHO/MOD

CELLINTRAFREQHO.

TrigTime1J

Content: This parameter specifies the time delay to trigger event 1J. The value of this

parameter correlates with slow fading. The larger the value of this parameter, the lower

probability of incorrect decision, but the slower the response of event to the change of

measured signals.

Value range: D0, D10, D20, D40, D60, D80, D100, D120, D160, D200, D240, D320,

D640, D1280, D2560, D5000


2560, 5000

Physical unit: ms

Set this parameter through SET INTRAFREQHO/ADD CELLINTRAFREQHO/MOD

CELLINTRAFREQHO.

MaxEdchCellInActiveSet

Content: This parameter determines the maximum number of links in the EDCH active

set. When the RNC acts as the SRNC, the number of links in the EDCH active set for all

the UEs under the RNC cannot exceed the parameter value. If the parameter value is

too large, a lot of resources on the RAN side will be occupied as the same data is

transferred over multiple EDCH links in macro diversity, thus affecting the system

performance. If this parameter value is too small, insufficient combination gain can be

achieved in macro diversity by the EDCH, which causes excessive retransmissions and

affects the UE speed.

Value range: 1~4

Physical value range: 1~4; step: 1

Set this parameter through SET HOCOMM.

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The report mode of 1J is event trigger report.

Generally the event 1J is reported only once. However, to avoid measurement report

loss, the event 1J reporting can be turned to periodical reporting.

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ReportIntervalfor1J


1J for periodical reporting. That is, event 1J is reported at each reporting

interval. Usually, event 1J is reported only once. Nevertheless, if the cell,

where event 1J is reported, does not join the EDCH active set in a

specified period of time, the UE can change the reporting of event 1J

into periodical mode to avoid missing of measurement reports. The

event 1J of this cell is reported for PeriodMRReportNumfor1J times with

the reporting period as the set value.


D4000, D8000, D16000


4000, 8000, 16000

Physical unit: ms

PeriodMRReportNumfor1J


1J for periodical reporting. When the actual reporting times exceeds the






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Event Decision and Execution

1A

When receiving an event 1A report, the RNC decides whether to add a

cell.

For event 1A, the UE can report more than one cell in the event list in

one measurement report. These cells are in the list of the

MEASUREMENT CONTROL message, and they are sequenced in

descending order of measurement quantity. For the cells in the list, the

RNC adds the radio link to the active set only if the number of cells in

the active set does not reach the maximum value. This operation is not

required if the number of cells in the active set reaches a specified value.

1B

When receiving an event 1B report, the RNC decides whether to delete

a cell. For event 1B, if there is more than one radio link in the active set,

the RNC decides whether to delete a radio link. This operation is not

required if there is only one radio link in the active set.

1C

When receiving an event 1C report, the RNC decides whether to

change the worst cell. For event 1C, the UE reports a list that contains

good cells and the cells to be replaced, and sequences the cells in

descending order by measurement quantity. After receiving the list from

the UE, the RNC replaces the bad cells in the active set with the good

cells in the list.

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MaxCellInActiveSet

Content: This parameter specifies the maximum number of cells in the

active set. This parameter can achieve the balance between the signal

quality in the SHO area and the performance of the system. The more

cells the active set contains, the larger macro diversity gain the user

obtains in the SHO area, and the smaller the intra-frequency interference

is. But in this case, the user occupies resources of several cells, which

increases the amount of data to be processed by the system and lowers

the system performance.

Value range: 1~6


SHOQualmin

Content: When the RNC receives events 1A, 1C and 1D, the target cell

can be added to the active set only when CPICH Ec/No of the target cell

is higher than this absolute threshold.

Value range: -24~0


Physical unit: dB



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After the active set is updated, the RNC updates the neighboring cell list by

using the neighboring cell combination algorithm according to the status of the

active set. This list includes the new intra-frequency, inter-frequency, and inter-

RAT neighboring cells. The combination methods of intra-frequency handover,

inter-frequency handover, and inter-RAT handover are the same.

The neighboring cell combination result is contained in the MEASUREMENT

CONTROL message and sent to the UE, which instructs the UE to perform

intra-frequency, inter-frequency, and inter-RAT measurement and handover

procedures.

The number of inter-frequency neighboring cells is configured as follows:

A maximum of 32 intra-frequency neighboring cells are configured.

A maximum of 32 single-carrier inter-frequency neighboring cells are

configured.

A maximum of 64 multi-carrier inter-frequency neighboring cells are

configured.

A maximum of 32 inter-RAT neighboring cells are configured.

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Neighboring cell combination switch:

HO_MC_NCELL_COMBINE_SWITCH is the neighboring cell combination

switch.

If the switch is set to ON, measurement objects are chosen from the

neighboring cells of all the cells in the active set.

If the switch is set to OFF, measurement objects are chosen from the

neighboring cells of the best cell.

Neighboring cell combination procedure:

After obtaining the intra-frequency neighboring cells of each cell in the active set,

the RNC calculates the union neighboring cell set of the intra-frequency cells,

which is referred as Sall, by using the following method. This method can also

be used to generate the Sall of inter-frequency or inter-RAT cells.

The intra-frequency, inter-frequency, and inter-RAT neighboring cells of

each cell in the current active set are obtained.

The RNC sequences the cells in the active set in descending order of

CPICH Ec/No according to the latest measurement report (event 1A, 1B,

1C, or 1D) from the UE. The best cell is based on event 1D, whereas

other cells are based on the latest measurement report.

The cells in the active set are added to Sall.

The neighboring cells of the best cell in the active set are added to Sall.

NprioFlag (the flag of the priority) and Nprio (the priority of the

neighboring cell), which are set for each neighboring cell, are used to

change the order of adding the neighboring cells to Sall.

The neighboring cells of other cells in the active set are added to Sall in

descending order by CPICH Ec/No values of these cells in the active set.

The neighboring cells of the same cell in the active set are added

according to Nprio and the number of repeated neighboring cell is

recorded.

If there are more than 32 intra-frequency neighboring cells in Sall, delete

the repeated neighboring cells whose number in Sall is less. The top 32

neighboring cells are grouped into the final Sall.

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HO_MC_NCELL_COMBINE_SWITCH

Content: When the switch is on, the neighboring cell combined algorithm

is used during the delivery of the objects to be measured. When the

switch is off, the best cell algorithm is used.

Value range: ON, OFF

Physical value range: 1, 0

Set this parameter through SET CORRMALGOSWITCH.

NprioFlag

Content: Priority identifier of neighboring cells. TRUE indicates that the

neighboring cell priority is valid in the algorithm of neighboring cell

combination. FALSE indicates that the neighboring cell priority is invalid,

and, in the algorithm of neighboring cell combination, the cell with invalid

priority is the last one to be considered as the measurement object.

Value range: FALSE, TRUE

Physical value range: FALSE, TRUE

Nprio

Content: Priority of neighboring cells. The lower the priority, the easier it

is for the neighboring cell to be delivered as the measurement object.

For example, it is more possible for a neighboring cell of priority 1 than a

cell of priority 2 to be delivered as the measurement object.

Value range: 0~30


Set the upper two parameters through ADD INTRAFREQNCELL/MOD

INTRAFREQNCELL / ADD INTERFREQNCELL/MOD INTERFREQNCELL /

ADD GSMNCELL/MOD GSMNCELL.

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N-52

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N-53

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N-54

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N-55

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N-56

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N-57

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N-58

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N-59

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N-60

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N-61

Coverage-based inter-frequency handover:

If a moving UE leaves the coverage of the current frequency, the RNC

needs to trigger the coverage-based inter-frequency handover to avoid

call drops.

QoS-based inter-frequency handover:

According to the Link Stability Control Algorithm, the RNC needs to

trigger the QoS-based inter-frequency handover to avoid call drops.

Load-based inter-frequency blind handover:

To balance the load between inter-frequency con-coverage cells, the

RNC chooses some UEs and performs the inter-frequency blind

handover according to user priorities and service priorities.

Speed-based inter-frequency handover:

When the Hierarchical Cell Structure (HCS) applies, the cells are divided

into different layers according to coverage. The macro cell has a larger

coverage and a lower priority, whereas the micro cell has a smaller

coverage and a higher priority.

Inter-frequency handover can be triggered by the UE speed estimation

algorithm of the HCS. To reduce frequent handovers, the UE at a higher

speed is handed over to a cell under a larger coverage, whereas the UE

at a lower speed is handed over to a cell under a smaller coverage.

The InterFreqHOSwitch parameter in the ADD CELLHOCOMM command is

used to chooses the inter-frequency measurement control parameters to

implement handover measurement based on coverage, QoS and speed.

The HO_INTER_FREQ_HARD_HO_SWITCH parameter in the SET

CORRMALGOSWITCH command is used to determine whether to allow load-

based inter-frequency handover.

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N-62

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N-63

In the triggering phase:

The RNC requests the UE to measure through an inter-frequency

measurement control message. If the CPICH Ec/No or CPICH RSCP of

the current cell is lower than the corresponding threshold, the UE reports

event 2D.

In the measurement phase:

The RNC sends an inter-frequency measurement control message to the

UE, requesting the NodeB and UE to start the compressed mode. The

RNC also requests the UE to perform the inter-frequency measurement.

In this phase, the method of either periodical measurement report or

event-triggered measurement report can be used.

In the decision phase:

After the UE reports event 2B, the RNC performs the handover.

Otherwise, the UE periodically generates measurement reports, and the

RNC makes a decision after evaluation.

In the execution phase:

The RNC executes the handover procedure.

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N-64

When the estimated quality or strength of the currently used frequency is below

a certain threshold, 2D event will be triggered. Then RNC will initiate the

compressed mode to start inter-frequency measurement.

During compressed mode, if the estimated quality of the currently used

frequency is above a certain threshold, 2F event will be triggered. Then RNC

will stop the compressed mode.

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N-65

Compressed mode control is a mechanism whereby certain idle periods are

created in radio frames during which the UE can perform measurements on

other frequencies. The UE can carry out measurements in the neighboring cell,

such as GSM cell and FDD cell on other frequency. If the UE needs to measure

the pilot signal strength of an inter-frequency WCDMA or GSM cell and has one

frequency receiver only, the UE must use the compressed mode.

Each physical frame can provide 3 to 7 timeslots for the inter-frequency or inter-

RAT cell measurement, which enhances the transmit capability of physical

channels but reduces the volume of data traffic.

In DL, during compressed mode, UE receiver can test signal from other

frequency. In order to avoid the effect cause by UE transmitter, compressed

mode is also used in UL.

The compressed mode includes two types, spreading factor reduction (SF/2)

and high layer approaches. The usage of type of compressed mode is decided

by the RNC, according to spreading factor used in uplink or downlink.

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N-66

QUsed is the measured quality of the used frequency.

TUsed2d is the absolute quality threshold of the cell that uses the current

frequency. Based on the service type and measurement quantity, this threshold

can be configured through one of the following parameters:

InterFreqCSThd2DEcN0

InterFreqR99PsThd2DEcN0

InterFreqHThd2DEcN0

InterFreqCSThd2DRSCP

InterFreqR99PsThd2DRSCP

InterFreqHThd2DRSCP

H2d is the event 2D hysteresis value set through the parameter HystFor2D.

After the conditions of event 2D are fulfilled and maintained until the

TimeToTrig2D is reached, the UE sends the event 2D measurement report

message.

Any of the Ec/No and RSCP measurement result can trigger the 2D

event.

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N-67

InterFreqCSThd2DEcN0

Content: Threshold to trigger inter-frequency measurement with

measurement quantity of Ec/No for CS domain services.

Value range: -24~0


Physical unit: dB

InterFreqR99PsThd2DEcN0 Content: Threshold to trigger inter-frequency measurement with

measurement quantity of Ec/No for PS domain non-HSPA services.

Value range: -24~0


Physical unit: dB

InterFreqHThd2DEcN0 Content: Threshold to trigger inter-frequency measurement with

measurement quantity of Ec/No for PS domain HSPA services.

Value range: -24~0

Physical value range: -24~0; step : 1

Physical unit: dB

Set these parameters through ADD CELLINTERFREQHOCOV/MOD

CELLINTERFREQHOCOV/SET INTERFREQHOCOV.

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N-68

InterFreqCSThd2DRSCP

Content: Threshold to trigger inter-frequency measurement with measurement quantity of RSCP for CS domain services.

Value range: -115~-25

Physical value range: -115~-25; step: 1

Physical unit: dBm

InterFreqR99PsThd2DRSCP

Content: Threshold to trigger inter-frequency measurement with measurement quantity of RSCP for PS domain non-HSPA services.



Physical unit: dBm

InterFreqHThd2DRSCP

Content: Threshold to trigger inter-frequency measurement with measurement quantity of RSCP for PS domain HSPA services.



Physical unit: dBm



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N-69

HystFor2D

Content: Hysteresis value for the event 2D. The value of this parameter

correlates with slow fading. The larger the value of this parameter, the

smaller probability of ping-pong effect or wrong decision, but event 2D

might not be triggered in time.

Value range: 0~29


Physical unit: dB

TimeToTrig2D Content: Time delay to trigger event 2D. The value of this parameter


lower probability of incorrect decision, but the slower the response of

event 2D to the change of measured signals.


D240, D320, D640, D1280, D2560, D5000


640, 1280, 2560, 5000

Physical unit: ms



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N-70


TUsed2f is the absolute quality threshold of the cell that uses the current


can be configured through one of the following parameters:

InterFreqCSThd2FEcN0

InterFreqR99PsThd2FEcN0

InterFreqHThd2FEcN0

InterFreqCSThd2FRSCP

InterFreqR99PsThd2FRSCP

InterFreqHThd2FRSCP

H2f is the event 2F hysteresis value set through the parameter HystFor2F.

After the conditions of event 2F are fulfilled and maintained until the parameter

TimeToTrig2F is reached, the UE reports the event 2F measurement report

message.

Any of Ec/No and RSCP measurement result can trigger the 2F event.

Conditions of event 2F are as follows: TUsed2d - H2d/2 < TUsed2f + H2f/2, for

example, (InterFreqCSThd2DEcN0–HystFor2D/2) < (InterFreqCSThd2FEcN0+

HystFor2F/2).

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N-71

InterFreqCSThd2FEcN0

Content: Threshold to stop inter-frequency measurement with

measurement quantity of Ec/No for CS domain services.

Value range: -24~0


Physical unit: dB

InterFreqR99PsThd2FEcN0 Content: Threshold to stop inter-frequency measurement with

measurement quantity of Ec/No for PS domain non-HSPA services.

Value range: -24~0


Physical unit: dB

InterFreqHThd2FEcN0 Content: Threshold to stop inter-frequency measurement with

measurement quantity of Ec/No for PS domain HSPA services.

Value range: -24~0


Physical unit: dB



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N-72

InterFreqCSThd2FRSCP

Content: Threshold to stop inter-frequency measurement with measurement quantity of RSCP for CS domain services.



Physical unit: dBm

InterFreqR99PsThd2FRSCP

Content: Threshold to stop inter-frequency measurement with measurement quantity of RSCP for PS domain non-HSPA services.



Physical unit: dBm

InterFreqHThd2FRSCP

Content: Threshold to stop inter-frequency measurement with measurement quantity of RSCP for PS domain HSPA services.



Physical unit: dBm



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N-73

HystFor2F

Content: Hysteresis value for the event 2F. The value of this parameter


smaller probability of ping-pong effect or wrong decision, but event 2F


Value range: 0~29


Physical unit: dB

TimeToTrig2F Content: Time delay to trigger the event 2F. The value of this parameter



event 2F to the change of measured signals.


D240, D320, D640, D1280, D2560, D5000


640, 1280, 2560, 5000

Physical unit: ms



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N-74

When the UE enters the compress mode, RNC will trigger the inter-frequency

handover measurement by two additional measurement control signaling, so as

to request UE test inter-frequency neighbor cell.

In this Measurement control message, RNC should inform the UE inter-

frequency measurement parameter, including neighbor list and reporting mode

as well.

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N-75

The measurement report mode of inter-frequency handover is configured

through the parameter InterFreqReportMode. By default, periodically reporting

is recommended.

The advantage of periodical measurement report is that if the handover fails, the

RNC reattempts the handover to the same cell after receiving the periodical

measurement report from the UE. This increases the probability of the success

of inter-frequency handover.

Based on the measurement control message received from the RNC, the UE

periodically reports the measurement quality of the target cell. Then, based on

the measurement report, the RNC makes the handover decision and performs

handover.

If the reporting mode is periodically reporting: UE test the Inter-frequency

neighbor RSCP and Ec/No.

If the reporting mode is event trigger reporting: UE test the Inter-frequency

neighbor RSCP and Ec/No, and current cell Ec/No or RSCP.

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N-76

InterFreqReportMode

Content: This parameter specifies the inter-frequency measurement report mode.

Value range: PERIODICAL_REPORTING(Periodical reporting), EVENT_TRIGGER(Event trigger)

Physical value range: Periodical reporting, Event trigger

PrdReportInterval

Content: This parameter specifies the interval of the inter-frequency measurement report.

Value range: NON_PERIODIC_REPORT(Non periodical reporting), D250, D500, D1000, D2000, D3000, D4000, D6000, D8000, D12000, D16000, D20000, D24000, D28000, D32000, D64000

Physical value range: NON_PERIODIC_REPORT, 250, 500, 1000, 2000, 3000, 4000, 6000, 8000, 12000, 16000, 20000, 24000, 28000, 32000, 64000

Physical unit: ms

InterFreqMeasTime

Content: Timer length for inter-frequency measurement. After inter-frequency measurement starts, if no inter-frequency handover is performed when this timer expires, the inter-frequency measurement and the compressed mode (if started) are stopped. The value 0 indicates the timer is not to be enabled.

Value range: 0~512


Physical unit: s



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N-77

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N-78

Mother_Freq is the CPICH Ec/No or CPICH RSCP measurement value of the

target cell reported by the UE. Both of the two measurement values of the inter-

frequency cell must satisfy the formula.

CIOother_Freq is the cell individual offset value of the target cell. It is equal to

the sum of CIO and CIOOffset.

Tother_Freq is the decision threshold of inter-frequency hard handover. Based

on the service type and measurement quantity, this threshold can be configured

through one of the following parameters:

TargetFreqCsThdEcN0

TargetFreqR99PsThdEcN0

TargetFreqHThdEcN0

TargetFreqCsThdRscp

TargetFreqR99PsThdRscp

TargetFreqHThdRscp

These thresholds are the same as the quality threshold of event 2B.

H is the inter-frequency hard handover hysteresis value set through the

parameter HystForPrdInterFreq.

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N-79

Each cell in the measurement report shall be evaluated as mentioned

previously. When the hard handover time-to-trigger timers of more than one cell

expire at the same time, the latest measurement report is used for selecting the

best inter-frequency neighboring cell for handover. For example, the cell with

the highest CPICH RSCP in the latest measurement report is selected, as

shown in the above figure.

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N-80

CIO

Content: This parameter works with the Neighboring cell oriented CIO. It

is used for intra- or inter-frequency handover decisions. The larger the

sum, the higher the handover priority of the neighboring cell. The smaller

the sum, the lower the handover priority of the neighboring cell. Usually it

is configured to 0.

Value range: -20~20

Physical value range: -10~10; step: 0.5

Physical unit: dB

Set this parameter through ADD CELLSETUP/MOD CELLSETUP.

CIOOffset

Content: This parameter defines the neighboring cell oriented cell

individual offset. The set value functions in combination of the cell

oriented CIO. Their sum is added to the measurement quantity before

the UE evaluates whether an event has occurred. In handover

algorithms, this parameter is used for moving the border of a cell.

Value range: -20~20


Physical unit: dB

Set this parameter through ADD INTERFREQNCELL/MOD

INTERFREQNCELL.

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N-81

HystForPrdInterFreq

Content: Hysteresis for inter-frequency hard handover in periodical

report mode. This parameter is used to estimate the inter-frequency

handover at the RNC. The larger the value of this parameter, the

stronger the capability of resisting signal fluctuation. Thus, the ping-pong

effect can be resisted, but the speed of the handover algorithm to

respond to signal change becomes lower, and therefore event 2B might

not be triggered in time.

Value range: 0~29


Physical unit: dB

TimeToTrigForPrdInterFreq

Content: Hysteresis for inter-frequency hard handover in periodical

report mode. This parameter is used to estimate the inter-frequency

handover at the RNC. The larger the value of this parameter, the





Value range: 0~64000


Physical unit: ms



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N-82

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N-83

QNoused is the measured quality of the cell that uses the other frequencies.


H2b is the event 2B hysteresis value set through the parameter HystFor2B.

TNoused2b is the absolute quality threshold of the cell that uses the other

frequencies. Based on the service type and measurement quantity, this

threshold can be configured through one of the following parameters:

TargetFreqCsThdEcN0

TargetFreqR99PsThdEcN0

TargetFreqHThdEcN0

TargetFreqCsThdRscp

TargetFreqR99PsThdRscp

TargetFreqHThdRscp

TUsed2b is the absolute quality threshold of the cell that uses the current

frequency.

After the conditions of event 2B are fulfilled and maintained until the parameter

TimeToTrig2B is reached, the UE reports the event 2B measurement report

message.

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N-84

TUsed2b is set in the following way:

Based on the service type and measurement quantity, this threshold can be

configured through one of the following parameters:

If event 2D with the CPICH RSCP value is received by the RNC:

TUsed2b of event 2B with the CPICH RSCP value can be:

UsedFreqCSThdRSCP

UsedFreqR99PsThdRSCP

UsedFreqHThdRSCP

TUsed2b of event 2B with the CPICH Ec/No value is configured

as the maximum value 0dB.

According to 3GPP specifications, TUsed2b of event 2B with the

CPICH Ec/No value should be configured as the maximum value

0dB. If the event 2F with the CPICH Ec/No value is received by

the RNC and TUsed2b of event 2B with the CPICH Ec/No value

is modified, TUsed2b is reset to 0dB.

If event 2D with the CPICH Ec/No value is received by the RNC:

TUsed2b of event 2B with the CPICH Ec/No value can be:

UsedFreqCSThdEcN0

UsedFreqR99PsThdEcN0

UsedFreqHThdEcN0

TUsed2b of event 2B with the CPICH RSCP value is configured

as the maximum value –25 dBm.

According to 3GPP specification, TUsed2b of event 2B with the

CPICH RSCP value should be configured as the maximum value

-25dBm. If event 2F with the CPICH RSCP value is received by

the RNC and TUsed2b of event 2B with the CPICH RSCP value

is modified, TUsed2b is reset to -25 dBm.

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N-85

TargetFreqCsThdEcN0

Content: Threshold of the target frequency for triggering inter-frequency

measurement with measurement quantity of Ec/No for CS domain

services. For CS domain services, if the value of inter-frequency

measure report mode is set to EVENT_TRIGGER, this parameter is

used to set the measurement control of event 2B. One of the necessary

conditions for triggering event 2B can be met only when the quality of the

target frequency is higher than this threshold. If the value of inter-

frequency measure report mode is set to PERIODICAL_REPORTING,

this parameter is used to evaluate inter-frequency handovers at the

RNC. .

Value range: -24~0


Physical unit: dB

UsedFreqCSThdEcN0

Content: Threshold of used frequency quality for triggering inter-

frequency measurement with measurement quantity of Ec/No for CS

domain services. For CS domain services, if the value of inter-frequency

measure report mode is set to EVENT_TRIGGER, this parameter is

used to set the measurement control of event 2B. One of the necessary

conditions can be met only when the quality of the used frequency is

lower than this threshold.

Value range: -24~0


Physical unit: dB



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N-86



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N-87

HystFor2B

Content: Hysteresis value for the event 2B. The value of this parameter






Value range: 0~29


Physical unit: dB

TimeToTrig2B Content: Time delay to trigger event 2B. The value of this parameter



event 2B to the change of measured signals.


D240, D320, D640, D1280, D2560, D5000


640, 1280, 2560, 5000

Physical unit: ms



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N-88

InterFreqNCovHOThdEcN0

Content: Threshold of signal quality of the target frequency for triggering inter-frequency

measurement. This parameter is used to set measurement control on the event 2C. The

event 2C is triggered when the signal quality of the target frequency is above this

threshold.

Value range: -24~0


Physical unit: dB

2C hysteresis

Content: Hysteresis value for the event 2C. The value of this parameter correlates with

slow fading. The larger the value of this parameter, the stronger the capability of resisting

signal fluctuation. Thus, the ping-pong effect can be resisted, but the speed of the

handover algorithm to respond to signal change becomes lower, and therefore event 2C


Value range: 0~29


Physical unit: dB

TrigTime2C

Content: Time delay to trigger the event 2C. The value of this parameter correlates with

slow fading. The larger the value of this parameter, the lower probability of incorrect

decision, but the slower the response of event 2C to the change of measured signals. .

Value range D0, D10, D20, D40, D60, D80, D100, D120, D160, D200, D240, D320,

D640, D1280, D2560, D5000


2560, 5000

Physical unit: ms

Set these parameters through ADD CELLINTERFREQHONCOV/MOD

CELLINTERFREQHONCOV/SET INTERFREQHONCOV.

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N-89

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N-90

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N-91

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N-92

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N-93

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N-94

Inter-RAT handover refers to the handover performed between 3G network and

2G network. Inter-RAT handover provides continuous coverage, load sharing,

and HCS services, which fully utilizes the existing 2G network resources and

thus reduces operator's cost.

In this handover, however, GSM and UMTS dual-mode UEs (MSs) are required,

and both the GSM MSC and the GSM BSS must be upgraded.

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N-95

Coverage-based 3G to 2G handover:

The coverage of the 3G network is incontinuous at the initial stage. On the border of the coverage, the poor signal quality of the 3G network triggers the 3G-to-2G measurement. If the signal quality of the 2G network is good enough and all the services of the UE are supported by the 2G network, the coverage-based 3G to 2G handover is triggered.

QoS-based 3G to 2G handover:

According to the Link Stability Control Algorithm, the RNC needs to trigger the QoS-based 3G to 2G handover to avoid call drops.

Load-based 3G to 2G handover:

If the load of the 3G network is heavy and all the RABs of the UE are supported by the 2G network, the load-based 3G to 2G handover is triggered.

Service-based 3G to 2G handover:

Based on layered services, the traffic of different classes is handed over to different systems. For example, when an Adaptive Multi Rate (AMR) speech service is requested, this service can be handed over to the 2G network.

Speed-based 3G to 2G handover:

The principles of the 3G-to-2G handover based on HCS speed estimation are similar to those of inter-frequency handover.

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N-96

2G cell capability:

2G cell capability is configured through the parameter RATCELLTYPE.

This parameter indicates whether the cell supports the GSM, GPRS, or

EDGE.

For more detailed information, please refer to the ADD GSMCELL

command.

Service capability:

The required 2G capability (Req2GCap) specifies the capability of 2G

cells required by inter-RAT handover. This indicates whether the service

is supported by the GSM, GPRS, or EDGE.

For more detailed information, please refer to the ADD TYPRABBASIC

command.

UE capability:

Upon the reception of the UE capability information message, the RNC

decides whether to start the inter-RAT measurement. The information

indicates whether the UE supports the GSM, GPRS, or EDGE.

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N-97

Service handover indicator:

The IE service handover indicator indicates the CN policy for the service

handover to the 2G network. This IE is indicated in the Radio Access Bearer

(RAB) assignment signaling assigned by the CN, or in the following table

configured in the RNC by default.

The algorithm switch HoSwitch:

HO_INTER_RAT_RNC_SERVICE_HO_SWITCH decides whether the service

attribute of inter-RAT handover is based on the RNC or the CN.

If the switch is set to on, the service attribute of inter-RAT handover is

based on the parameter configured on the RNC side.

If the switch is set to off, the service attribute of inter-RAT handover is

first based on the CN when the indicator is contained in the RAB

assignment signaling assigned by the CN. If the CN does not allocate a

service indicator, the service attribute of inter-RAT handover is based on

the RNC side.

For more detailed information, please refer to the SET

CORRMALGOSWITCH command.

Through the SHIND parameter, the service handover indicators are set as

follows:

HO_TO_GSM_SHOULD_BE_PERFORM: means that the handover to

the 2G network is performed when 2G signals are available.

HO_TO_GSM_SHOULD_NOT_BE_PERFORM: means that the

handover to the 2G network is performed when 3G signals are weak but

2G signals are strong.

HO_TO_GSM_SHALL_NOT_BE_PERFORM: means that the handover

to the 2G network is not performed even when 3G signals are weak but

2G signals are strong.

For more detailed information, please refer to the ADD TYPRABBASIC

command.

CN

DomainTraffic Class Max Rate

Service Handover

Indicator

Required 2G

Capability

CS CONVERSATIONAL 12.2kHO_TO_GSM_SHOULD_

NOT_BE_PERFORMGSM

CS CONVERSATIONAL 64kHO_TO_GSM_SHALL_N

OT_BE_PERFORMGSM

PS INTERACTIVE 64kHO_TO_GSM_SHOULD_

NOT_BE_PERFORMGPRS

PS INTERACTIVE 384kHO_TO_GSM_SHOULD_

NOT_BE_PERFORMEDGE

PS BACKGROUND 64kHO_TO_GSM_SHOULD_

NOT_BE_PERFORMGPRS

PS BACKGROUND 384kHO_TO_GSM_SHOULD_

NOT_BE_PERFORMEDGE

PS BACKGROUND >384kHO_TO_GSM_SHALL_N

OT_BE_PERFORMEDGE

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N-98

Cell

Capability

UE Capability Service Capability (Required by 2G)

EDGE GPRS GSM

EDGE EDGE Allowed Allowed Allowed

GPRS Allowed Allowed Allowed

GSM Not allowed Not allowed Allowed

Not supported

by 2G

Not allowed Not allowed Not allowed

GPRS EDGE Allowed Allowed Allowed

GPRS Allowed Allowed Allowed


Not supported

by 2G


GSM EDGE Not allowed Not allowed Allowed

GPRS Not allowed Not allowed Allowed


Not supported

by 2G


Course Name


N-99

Cell

Capability

UE Capability Service Capability (Required by 2G)

EDGE GPRS GSM

EDGE EDGE Allowed Allowed Allowed

GPRS Not allowed Allowed Allowed


Not supported by 2G Not allowed Not allowed Not

allowed

GPRS EDGE Not allowed Allowed Allowed

GPRS Not allowed Allowed Allowed



allowed

GSM EDGE Not allowed Not allowed Allowed

GPRS Not allowed Not allowed Allowed



allowed

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N-100

To perform the service-based 3G to 2G handover, the RNC must turn on the

related switches for services in the CS and PS domains.

When a single CS service is initially set up by the UE, the RNC allows

the 3G to 2G service-based handover if CSServiceHOSwitch is set to on.

When a single PS service is initially set up by the UE, the RNC allows

the service-based 3G-to-2G handover if PSServiceHOSwitch is set to on.

For the CS and PS combined services, no service-based handover is

triggered.

For more detailed information, please refer to the ADD CELLHOCOMM

command.

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N-101

Course Name


N-102

In the triggering phase:

The RNC requests the UE to measure through an inter-RAT

measurement control message. If the CPICH Ec/No or CPICH RSCP of

the current cell is lower than the corresponding threshold, the UE reports

event 2D.

In the measurement phase:

The RNC sends an inter-RAT measurement control message to the UE,

requesting the NodeB and UE to start the compressed mode. The RNC

also requests the UE to perform the inter-RAT measurement.

In this phase, the method of either periodical measurement report or

event-triggered measurement report can be used.

In the decision phase:

After the UE reports event 3A, the RNC performs the handover.

Otherwise, the UE periodically generates measurement reports, and the

RNC makes a decision after evaluation.

In the execution phase:

The RNC executes the handover procedure.

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N-103

When the estimated quality or strength of the currently used frequency is below

a certain threshold,2D event will be triggered. Then RNC will initiate the

compressed mode to start inter-RAT handover measurement.

During compressed mode, if the estimated quality or strength of the currently

used frequency is above a certain threshold, 2F event will be triggered. Then

RNC will stop the compressed mode.

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N-104

QUsed is the measurement value of the cell at the currently used frequency.

TUsed2d is the absolute quality threshold of the cell at the currently used


can be configured through the following parameters:

InterRATCSThd2DEcN0

InterRATR99PsThd2DEcN0

InterRATHThd2DEcN0

InterRATCSThd2DRSCP

InterRATR99PsThd2DRSCP

InterRATHThd2DRSCP

H2d is the event 2D hysteresis value set through the parameter HystFor2D.

When the conditions for event 2D are met and maintained in time-to-trigger

specified by the parameter TimeToTrig2D, the UE sends the measurement

report of event 2D.

Any of the Ec/No and RSCP measurement result can trigger the 2D

event.

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N-105

The parameters for inter-RAT handover 2D are similar with inter-frequency

handover.

Set above parameters through ADD CELLINTERRATHOCOV/MOD

CELLINTERRATHOCOV/SET INTERRATHOCOV.

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N-106


TUsed2f is the absolute quality threshold of the cell at the currently used


can be configured through the following parameters:

InterRATCSThd2FEcN0

InterRATR99PsThd2FEcN0

InterRATHThd2FEcN0

InterRATCSThd2FRSCP

InterRATR99PsThd2FRSCP

InterRATHThd2FRSCP

H2f is the event 2F hysteresis value set through the parameter HystFor2F.

When the conditions for event 2F are met and maintained in time-to-trigger

specified by TrigTime2F, the UE sends the measurement report of event 2F.

Any of Ec/No and RSCP measurement result can trigger the 2F event.

Conditions of event 2F are as follows: TUsed2d - H2d/2 < TUsed2f + H2f/2, for

example, (InterRATCSThd2DEcN0–HystFor2D/2) < (InterRATCSThd2FEcN0+

HystFor2F/2).

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N-107

The parameters for inter-RAT handover 2F are similar with inter-frequency

handover.

Set above parameters through ADD CELLINTERRATHOCOV/MOD


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N-108

During the coverage-based and QoS-based 3G to 2G handover, the

measurements on both inter-frequency and inter-RAT neighboring cells can be

made, which enables the cells to provide continuous coverage and high quality.

The preconditions for the measurements are as follows:

Both inter-frequency and inter-RAT neighboring cells are available.

InterFreqRATSwitch is set to SIMINTERFREQRAT.

If InterFreqRATSwitch is set to:

Inter-frequency measurement (INTERFREQ), the RNC allows the UE to

perform only this type of measurement.

Inter-RAT measurement (INTERRAT), the RNC allows the UE to

perform only this type of measurement.

Concurrent inter-frequency and inter-RAT measurement

(SIMINTERFREQRAT), the RNC allows the UE to perform both types of

measurement at the same time.

During the concurrent inter-frequency and inter-RAT measurement, the values

of the parameter CoexistMeasThdChoice for event 2D are chosen as follows:

When the value COEXIST_MEAS_THD_CHOICE_INTERFREQ is

chosen, the inter-frequency measurement threshold for event 2D is used.

When the value COEXIST_MEAS_THD_CHOICE_INTERRAT is chosen,

the inter-RAT measurement threshold for event 2D is used.

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N-109

InterFreqRATSwitch

Content: Cell-level switch for inter-frequency and inter-RAT handover.

INTERFREQ: only measuring inter-frequency cells and performing inter-

frequency handover.

INTERRAT: only measuring GSM cells and performing inter-RAT handover .

SIMINTERFREQRAT: measuring both inter-frequency and inter-RAT cells,

performing inter-frequency or inter-RAT handover according to the type of the

cell that first meets the handover decision condition.

Value range: INTERFREQ, INTERRAT, SIMINTERFREQRAT

Physical value range: Inter-frequency handover only, Inter-RAT handover only,

Inter-frequency and Inter-RAT handover

CoexistMeasThdChoice

Content: Type of event 2D/2F measurement thresholds when inter-frequency

and inter-RAT measurements coexist.

COEXIST_MEAS_THD_CHOICE_INTERFREQ: choosing the inter-frequency

oriented parameters as event 2D/2F measurement thresholds for inter-

frequency measurement.

COEXIST_MEAS_THD_CHOICE_INTERRAT: choosing the inter-RAT oriented

parameters as event 2D/2F measurement thresholds for inter-RAT

measurement.

Value range: COEXIST_MEAS_THD_CHOICE_INTERFREQ,

COEXIST_MEAS_THD_CHOICE_INTERRAT

Physical value range: Choosing the inter-frequency oriented parameters,

Choosing the inter-RAT oriented parameters

Set these parameters through SET HOCOMM/ADD CELLHOCOMM/MOD

CELLHOCOMM.

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N-110

When the UE enters the compressed mode, RNC will trigger the inter-RAT

handover measurement by one measurement control signaling, so as to request

UE test inter-RAT neighbor cell.

In this Measurement control message, RNC should inform the UE inter-RAT

measurement parameters, including neighbor list and reporting mode as well.

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N-111

The measurement report mode of inter-RAT handover is configured through the

parameter InterRatReportMode. By default, periodically reporting is

recommended.

Based on the measurement control message received from the RNC, the UE

periodically reports the measurement quality of the target cell. Then, based on

the measurement report, the RNC makes the handover decision and performs

handover.

If the reporting mode is periodically reporting: UE only test the Inter-RAT

neighbor RSSI only.

If the reporting mode is event trigger reporting: UE test the Inter-RAT neighbor

RSSI and current cell Ec/No or RSCP:

In coverage-based 3G to 2G handover, the event 3A measurement

quantity is set through the parameter MeasQuantityOf3A.

In QoS-based 3G to 2G handover, the event 3A measurement quantity is

set through the parameter UsedFreqMeasQuantityForQos3A.

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N-112

InterRatReportMode

Content: Inter-RAT measurement report mode.

When PERIODICAL_REPORTING is selected, you can infer that

periodical inter-RAT measurement report is adopted; when

EVENT_TRIGGER is selected, you can infer that event-triggered inter-

RAT measurement report is adopted.

Value range: PERIODICAL_REPORTING, EVENT_TRIGGER

Physical value range: Periodical reporting, Event trigger

InterRATPeriodReportInterval

Content: Interval that the UE reports inter-RAT measurement results to

the RNC. In periodical report mode, the interval between two reports is

the configured value. That is, the UE submits reports at intervals of the

configured time.


D3000, D4000, D6000, D8000, D12000, D16000, D20000, D24000,

D28000, D32000, D64000

Physical value range: Non periodical reporting, 250, 500, 1000, 2000,

3000, 4000, 6000, 8000, 12000, 16000, 20000, 24000, 28000, 32000,

64000

Physical unit: ms

Set these parameters through ADD CELLINTERRATHOCOV/MOD


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N-113

InterRATMeasTime

Content: Timer length for inter-RAT measurement. After inter-RAT

measurement starts, if no inter-RAT handover is performed when this timer

times out, the inter-RAT measurement is stopped. In addition, the compressed

mode is deactivated, if any; If the value is 0, you can infer that the inter-RAT

measurement timer is not started.

Value range: 0~512


Physical unit: s

MeasQuantityOf3A

Content: Measurement quantity used in coverage-based inter-RAT

measurement in event 3A-triggered reporting mode.

CPICH_Ec/No indicates that the Ec/No measurement quantity is used for event

3A measurement. The physical unit is dB.

CPICH_RSCP indicates that the RSCP measurement quantity is used for event

3A measurement. The physical unit is dBm.

AUTO indicates that the Ec/N0 measurement quantity is used for event 3A

measurement if RNC receives the Ec/No 2D firstly; the RSCP measurement

quantity is used for event 3A measurement if RNC receives the RSCP 2D firstly.

This parameter can be configured only when InterRatReportMode is set to

EVENT_TRIGGER.

Value range: CPICH_EC/NO, CPICH_RSCP, AUTO

Physical value range: CPICH_EC/NO, CPICH_RSCP, AUTO



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N-114

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N-115

Mother_RAT is the measurement result of inter-RAT handover (RSSI) received

by the RNC.

CIOother_RAT is the cell individual offset value of the target cell. It is equal to

the sum of CIO and CIOOffset.

Tother_RAT is the decision threshold of inter-RAT hard handover.Based on the

service type and measurement quantity, this threshold can be configured

through the following parameters:

TargetRatCsThd

TargetRatR99PsThd

TargetRatHThd

These thresholds are the same as the quality threshold of event 3A.

H is the inter-RAT handover hysteresis value set through HystforInterRAT.

The length of the time-to-trigger timer is configured through the parameter

TimeToTrigForVerify (with BSIC acknowledged, and it is the default setting) or

the parameter TimeToTrigForNonVerify (with BSIC unacknowledged).

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N-116

CIO

Content: This parameter is used for the inter-RAT handover decision in

combination with the neighboring cell oriented CIO. The larger the sum,

the higher the handover priority of the GSM cell. The smaller the sum,

the lower the handover priority of the GSM cell. The parameter is

generally set to 0.

Value range: -50~50


Physical unit: dB

Set this parameter through ADD GSMCELL/MOD GSMCELL.

CIOOffset

Content: This parameter is used for decision making for the inter-RAT

handover. The larger the value of the parameter, the higher the

handover priority of the GSM cell. The smaller the value of the parameter,

the lower the handover priority of the GSM cell.

Value range: -50~50


Physical unit: dB

Set this parameter through ADD GSMNCELL/MOD GSMNCELL.

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N-117

HystforInterRAT

Content: Hysteresis value for inter-RAT measurement periodical reports. This parameter

aims to prevent the mis-decision caused by unexpected jitters of signals during inter-

RAT handover decisions. The HystforInterRAT and the inter-RAT handover decision

threshold determine whether to trigger inter-RAT handovers.

Value range: 0~15

Physical value range: 0~15; step: 0.5

Physical unit: dB

TimeToTrigForVerify

Content: Time delay for triggering handovers to GSM cells with verified BSIC. During the

period of time specified by this parameter, if the signal quality in a neighboring GSM cell

satisfies inter-RAT handover conditions and the neighboring GSM cell is verified, an

inter-RAT handover is triggered.

Value range: 0~64000


Physical unit: ms

TimeToTrigForNonVerify

Content: Time delay for triggering handovers to GSM cells with non-verified BSIC.

During the period of time specified by this parameter, if the signal quality in a neighboring

GSM cell satisfies inter-RAT handover conditions and the neighboring GSM cell is not

verified, an inter-RAT handover is triggered. When the value of this parameter is 65535,

the RNC does not perform inter-RAT handovers to non-verified GSM cells.

Value range: 0~64000, 65535

Physical value range: 0~64000, 65535; step: 1

Physical unit: ms

Set this parameter through ADD CELLINTERRATHOCOV/MOD CELLINTERRATHOCOV/SET

INTERRATHOCOV.

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N-118

Course Name


N-119


TUsed is the absolute quality threshold of the cell that uses the current

frequency.

MOtherRAT is the measurement value of the cell (in another RAT) in the

reporting range.

CIOOtherRAT is the cell individual offset value of the cell (in another RAT) in

the reporting range which is equal to the sum of CIO and CIOOffset.

TOtherRAT is the absolute inter-RAT handover threshold. Based on different

service types (CS , PS domain R99 service, or PS domain HSPA service), this

threshold can be configured through the following parameters:

TargetRatCsThd

TargetRatR99PsThd

TargetRatHThd

H3a is 3A hysteresis, the hysteresis value of event 3A.

When the conditions for event 3A are met and maintained in time-to-trigger

specified by TrigTime3A the UE sends the measurement report of event 3A.

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N-120

UsedFreqCSThdEcN0

Content: Threshold of used frequency quality for triggering inter-RAT measurement with measurement quantity of Ec/No for CS domain services. For CS domain services, when Ec/No is used as the measurement quantity for inter-RAT measurement, this parameter is used to set measurement control on the event 3A. The event 3A is triggered, when the quality of the currently used UTRAN frequency is below this threshold and the TargetRatCsThd is reached.

Value range: -24~0


Physical unit: dB

TargetRatCsThd

Content: Quality requirement for the inter-RAT cell during an inter-RAT handover with CS domain services. For CS domain services, if the value of InterRatReportMode is set to EVENT_TRIGGER, this parameter is used to set the measurement control of event 3A. One of the necessary conditions for triggering event 3A can be met only when the quality of the target frequency is higher than this threshold; if the value of InterRatReportMode is set to PERIODICAL_REPORTING, this parameter is used to evaluate inter-RAT coverage handovers at the RNC. Note that the value 0 means the physical value is smaller than -110 dBm.

Value range: 0~63

Physical value range: Lower than -110, -110~-48 (1: -110; 2: -109; ...; 63: -48 )

Physical unit: dBm



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N-121



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N-122

Hystfor3A

Content: Hysteresis value for the event 3A. The value of this parameter

correlates with slow fading. The larger the value of this parameter, the stronger

the capability of resisting signal fluctuation. Thus, the ping-pong effect can be

avoided, but the speed of the handover algorithm to respond to signal change

becomes lower. If the inter-RAT handover hysteresis is set to an excessively

high value, the GSM cell to which the UE is handed over must be of good quality.

Therefore, the conditions for triggering the inter-RAT handover decision are hard

to be satisfied, and the call drop rate increases.

Value range: 0~15


Physical unit: dB

TrigTime3A

Content: Time delay to trigger the event 3A. The value of this parameter

correlates with slow fading. The larger the value of this parameter, the lower the

incorrect decision probability, but the slower the response of the event 3A to

measurement signal change.

Value range: D0, D10, D20, D40, D60, D80, D100, D120, D160, D200, D240,

D320, D640, D1280, D2560, D5000

Physical value range: 0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240, 320, 640,

1280, 2560, 5000

Physical unit: s



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N-123

PeriodFor3A

Content: Retry period for the event 3A. This parameter defines the length

of the event 3A retry period. The smaller the value of this parameter, the

more frequent the handover retry due to inter-RAT handover failure, and

the faster the UE to be successfully handed over to the target cell whose

load is restored, thus lowering the probability of call drops. In this case,

however, frequent handover retry brings more load to the RNC system.

Value range: 1~64


Physical unit: ms

AmntOfRpt3A

Content: Maximum retry times of the event 3A. This parameter defines

the number of times for event 3A retry when the measurement control is

valid. The larger the value of this parameter, the larger the number of

times for inter-RAT handover retry, and the higher probability the UE is

successfully handed over to the target cell whose load is restored. When

the retry times reaches the maximum value, the RNC stops the retry

process. Or if the measurement control message is released, the retry

will be immediately stopped.

Value range: 0~63

Physical value range: 0~62, 63: Infinity; step: 1

Set these parameters through ADD CELLINTERRATHOCOV / MOD

CELLINTERRATHOCOV / SET INTERRATHOCOV.

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N-124

PeriodFor3C

Content: Retry period for the event 3C. This parameter defines the

length of the event 3C retry period. The smaller the value of this

parameter, the more frequent the handover retry due to inter-RAT

handover failure, and the faster the UE to be successfully handed over

to the target cell whose load is restored, thus lowering the probability of

call drops. In this case, however, frequent handover retry brings more

load to the RNC system.

Value range: 1~64


Physical unit: ms

AmntOfRpt3C

Content: Maximum retry times of the event 3C. This parameter defines

the number of times for event 3C retry when the measurement control is

valid. The larger the value of this parameter, the larger the number of

times for inter-RAT handover retry, and the higher probability the UE is

successfully handed over to the target cell whose load is restored. When

the retry times reaches the maximum value, the RNC stops the retry

process. Or if the measurement control message is released, the retry

will be immediately stopped.

Value range: 0~63

Physical value range: 0~62, 63: Infinity; step: 1

Set these parameters through ADD CELLINTERRATHOCOV / MOD

CELLINTERRATHOCOV / SET INTERRATHOCOV.

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N-125

Course Name


N-126

The above figure shows the signaling procedures for the 3G-to-2G handover in

the CS domain. The 2G messages shown in the figure are for your reference

only.

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N-127

Signaling procedures for CS inter-RAT handover:

1. The SRNC sends the 3G MSC a RANAP message RELOCATION

REQUIRED if the condition of Inter-RAT outgoing handover is met.

2. As indicated in the received message, the 3G MSC forwards this request to

the 2G MSC on the MAP/E interface through a MAP message PREPARE

HANDOVER.

3. The 2G MSC forwards the request to the BSC. The message shown in the

figure is for reference only and is subject to the actual condition of the GSM.

4. The BSC responds to this request. The message shown in the figure is for

reference only and is subject to the actual condition of the GSM.

5. Once the initial procedures are completed in the 2G MSC/BSS, the 2G MSC

returns a MAP/E message PREPARE HANDOVER RESPONSE.

6. The 3G MSC sends the SRNC a RANAP message RELOCATION

COMMAND.

7. The SRNC sends the UE an RRC message HANDOVER FROM UTRAN

through the existing RRC connection. This message may include information

from one or several other systems.

8. The BSC performs handover detection. The figure does not show such

procedures as GSM BSS synchronization. The message shown in the figure is

for reference only and is subject to the actual condition of the GSM.

9. The UE sends the BSC a HANDOVER COMPLETE message.

10. The BSC sends the MSC a HANDOVER COMPLETE message. The

message shown in the figure is for reference only and is subject to the actual

condition of the GSM.

11. After detecting the UE in the coverage area of the GSM, the MSC sends the

CN a MAP/E message SEND END SIGNAL REQUEST.

12. The CN sends the former SRNC an IU RELEASE COMMAND message,

requesting the former SRNC to release the allocated resource.

13. After the bearer resource is released in the UMTS, the former SRNC sends

the CN an IU RELEASE COMPLETE message.

14. After the call ends, the CN sends the MSC a MAP/E message SEND END

SIGNAL RESPONSE.

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N-128

For a UE in idle mode or connected mode, if the SGSN changes with the shift of

the system that the UE accesses from 3G network to 2G network, the inter-

SGSN handover will be performed.

The handover procedures are different in the following two cases:

When the UE is in CELL_DCH state:

The 3G to 2G handover in the PS domain is triggered after the UTRAN

sends a CELL CHANGE ORDER FROM UTRAN message.

When the UE is in CELL_FACH, CELL_PCH, or URA_PCH state:

The 3G to 2G handover in the PS domain is triggered through the cell

reselection.

The above figure shows an example of handover for the UE in CELL_FACH,

CELL_PCH, or URA_PCH state. When the UE is in idle mode, the cell

reselection procedure does not include the elementary procedures marked "UE

CONNECTED" in figure.

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N-129

Signaling procedures for PS inter-RAT handover:

1. The UE in CELL_DCH state or the UTRAN (when the UE is in CELL_FACH

state) decides to initiate an Inter-RAT handover in the PS domain to hand over

the UE to a new GSM cell and stop the data transmission between the UE and

the network.

2. The UE sends a ROUTING AREA UPDATE REQUEST message to the 2G

SGSN. The Update Type in the message indicates RA update, combined

RA/LA update, or combined RA/LA update with IMSI attach. The BSS adds the

CGI including the RAC and LAC of the cell to the received message before

forwarding the message to a new 2G SGSN.

3. The new 2G SGSN sends an SGSN CONTEXT REQUEST message to the

old 3G SGSN to obtain the MM and PDP contexts. The old 3G SGSN validates

the old P-TMSI Signature. If the old P-TMSI Signature is valid, the old 3G

SGSN starts a timer. Otherwise, the old 3G SGSN responds with an error

cause.

4. If the UE stays in connected mode before handover, the old 3G SGSN sends

an SRNS CONTEXT REQUEST message. After receiving this message, the

SRNS buffers the DPUs, stops sending the PDUs to the UE, and sends an

SRNS CONTEXT RESPONSE message to the old 3G SGSN.

5. The old 3G SGSN sends an SGSN CONTEXT RESPONSE message to the

2G SGSN, including the MM and PDP contexts.

6. The security functions can be executed.

7. The new 2G SGSN sends an SGSN CONTEXT ACKNOWLEDGE message

to the old 3G SGSN. This informs the old 3G SGSN that the new 2G SGSN is

ready to receive the PDUs belonging to the activated PDP contexts.

8. The old 3G SGSN sends a DATA FORWARD COMMAND message to the

SRNS. The SRNS starts a data-forwarding timer and sends the buffered PDUs

to the old 3G SGSN.

9. The old 3G SGSN tunnels the GTP PDUs to the new 2G SGSN. In the PDUs,

the sequence numbers in the GTP header remain unchanged.

10. The new 2G SGSN sends an UPDATE PDP CONTEXT REQUEST

message to each related GGSN. Each GGSN sends an UPDATE PDP

CONTEXT RESPONSE message after updating its PDP context fields.

11. The new 2G SGSN sends an UPDATE GPRS LOCATION message,

requesting the HLR to modify the SGSN number.

12. The HLR sends a CANCEL LOCATION message to the old 3G SGSN. The

old 3G SGSN responds with a CANCEL LOCATION ACK message. After the

timer expires, the old 3G SGSN removes the MM and PDP contexts.

13. The old 3G SGSN sends an IU RELEASE COMMAND message to the

SRNS. After the data-forwarding timer expires, the SRNS responds with an IU

RELEASE COMPLETE message.

14. The HLR sends an INSERT SUBSCRIBER DATA message to the new 2G

SGSN. The 2G SGSN constructs an MM context and PDP contexts for the UE

and returns an INSERT SUBSCRIBER DATA ACK message to the HLR.

15. The HLR sends an UPDATE GPRS LOCATION ACK message to the new

2G SGSN.

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N-130

16. If the association has to be established, the new 2G SGSN sends a

LOCATION UPDATE REQUEST message to the VLR. The VLR stores the

SGSN number for creating or updating the association.

17. If the subscriber data in the VLR is marked as not confirmed by the HLR,

the new VLR informs the HLR. The HLR cancels the old VLR and inserts

subscriber data in the new VLR.

1. The new VLR sends an UPDATE LOCATION message to the HLR.

2. The HLR cancels the data in the old VLR by sending a CANCEL

LOCATION message to the old VLR.

3. The old VLR acknowledges the message by responding with a

CANCEL LOCATION ACK message.

4. The HLR sends an INSERT SUBSCRIBER DATA message to the

new VLR.

5. The new VLR acknowledges the message by responding with an

INSERT SUBSCRIBER DATA ACK message.

6. The HLR responds with a UPDATE LOCATION ACK message to the

new VLR.

17. The new VLR allocates a new TMSI and responds with a LOCATION

UPDATE ACCEPT message to the 2G SGSN.

18. The new 2G SGSN checks the presence of the MS in the new RA. If all

checks are successful, the new 2G SGSN constructs the MM and PDP contexts

for the MS. A logical link is established between the new 2G SGSN and the UE.

The 2G SGSN responds to the UE with a ROUTING AREA UPDATE ACCEPT

message.

19. The UE acknowledges the new P-TMSI by returning a ROUTING AREA

UPDATE COMPLETE message, including all PDUs successfully sent to the UE

before the routing area update procedure.

20. The new 2G SGSN sends a TMSI REALLOCATION COMPLETE message

to the new VLR if the UE confirms the VLR TMSI.

21. The 2G SGSN and the BSS perform the BSS PACKET FLOW CONTEXT

procedure.

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N-131

2 WCDMA RAN12 Handover Algorithm and Parameters ISSUE1.02

Documents

handover types

softer handover

set of cells

radio link set

handover decision

purpose of handover

detected set

intrafrequency handover