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WCDMA Training Module Confidential

KomKonsult Training Module Confidential Page 1 of 21

WCDMA Power Control Algorithm

Analysis and Parameter Configuration

Guidance/ Handover Control


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1 Overview

In WCDMA, power control strategies that combine open-loop power control and closed-

loop power control fast power control and slow power control are adopted, which can well

overcome the influences of unfavorable factors such as fast fading on radio channels to guarantee

the transmission quality of radio channels.

This document contains two parts. The first part (Section 2) describes the power control

process principle and the relevant protocols, and the second part (Section 3) summarizes the

configuration methods and configuration values of parameters involved in power control and

briefly describes the meaning of each parameter and algorithms.

This document is suitable for network planning engineers to study, and can be used as field

operation guidance after the parts about algorithms and parameter configuration are properly

deleted.

2 Analysis on Power Control Management Principle and Protocol

*Note: The content of this section is described in detail in [4].

2.1 Basic Principle of Power Control

2.1.1 Power Control Methods for Various Physical Channels

See the following table:

Table 1 Power control methods adopted for various physical channels

Physical

channel

Open loop

power control

Inner loop

power

control

Outer loop

power

control

Slow power

control

No power controlprocess, power isspecified byupper layers.

DPDCH X X

DPCCH X X X

PCCPCH X

SCCPCH X

PRACH X


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PDSCH X X

PCPCH X X

AICH X

PICH X

AP-AICH X

CSICH X

CD/CA-ICH X

2.1.2 Open Loop Power Control

For an uplink channel, the UE estimates the power loss of signals on the propagation path by

measuring the downlink channel signals, and then identifies the transmission power of the uplinkchannel. This power control method is rather inaccurate, because under the FDD mode, fast

fading of the uplink channel has nothing to do with fast fading of the downlink channel, but in

the range of a cell, signal fading caused by fast fading is usually more serious than that caused by

propagation loss. Therefore, open loop power control is applied only at the beginning of

connection setup, generally in setting the initial power value.

For a downlink channel, the network side sets the initial value of the transmission power of

the downlink channel according to the UE measurement report.

2.1.3 Fast Power Control

Fast power control is a kind of closed-loop power control, which is described below

through the example of fast power control of uplink channel.

After NodeB receives a signal from the UE, it estimates the signal-to-interference

ratio (SIR) of this signal at the receiver end. Then, NodeB compares the signal-to-

interference ratio with the preset target signal-to-interference ratio (SIR target). If the

received signal-to-interference ratio is smaller than target signal-to-interference ratio,

NodeB will inform the UE through the downlink dedicated control channel to increase the

transmitting power; on the contrary, if the received signal-to-noise ratio is greater than

target signal-to-interference ratio, NodeB will inform the UE through downlink dedicated

control channel to decrease transmitting power. The whole control process is equivalent

to a negative feedback process, which can make the signal-to-interference ratio of the

received signal fluctuate near the target signal-to-interference ratio.


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The fast power control process of the downlink channel is the same with that of the

uplink channel, but the start points are different. Power control of the uplink channel is

mainly to overcome the near-far effect. A downlink channel does not have the problem

of near-far effect, and downlink channel power control is to overcome Rayleigh fadingand the interferences of adjacent cells.

In the dedicated control channel (DPCCH), each timeslot has its power control part

(TPC). In WCDMA, the frame duration of a physical frame is 10ms, and each physical

frame has 15 timeslots, so the maximum rate of power control is 1.5 KHz (the frame

format of the downlink dedicated channel is shown is Figure 1.). For a UE moving at a

medium or slow speed, this rate is greater than the Rayleigh fading rate, so the

transmission power can be well adjusted.

Figure 1 Frame Format of Downlink Dedicated Channel

The above-mentioned power control is inner loop power control, which is directly

implemented at the physical layer. From the hardware point of view, it is implemented by

NodeB and UE together, and RNC is not involved.

2.1.4 Outer Loop Power Control

The purpose of inner loop power control of the WCDMA system is to maintain a

certain signal-to-interference ratio of transmission signal power when the signals reach

the receiving end. However, in different multi-path environments, even if the mean

signal-to-interference ratio is kept above a certain threshold, it is likely that the

communication quality requirement (BER or FER or BLER) is not satisfied. So a kind of

outer loop power control mechanism is required to adjust the threshold of inner loop

power control dynamically in order to meet the communication quality requirement.


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Through the estimation of signal bit error rate (BER) or block error rate (BLER), the

upper layer of RNC or UE adjusts the target signal-to-interference ratio (SIR target) in fast

power control to accomplish the goal of power control. Since this kind of power control is

accomplished through upper layer, it is called outer loop power control. When the quality

of the received signals becomes bad (that is, bit error rate or block error rate increase),

the upper layer will increase the target signal-to-interference ratio (SIRtarget) to improve

the quality of received signals.

Figure 2 Fast power control

Figure 2 is a schematic diagram of downlink power control. Inner loop power control

is accomplished between BS and UE. The RNC implements outer loop power control by

setting BS target signal-to-interference ratio. The reason to use outer loop power control

is that signal quality will be different in different environments when the signal-to-

interference ratio is the same. For instance, under the same signal-to-interference ratio,

the faster the UE moves, the worse the signal quality will be. As shown in Figure 3,

generally, when mobile stands are still, the target signal-to-interference ratio is the

lowest.

D P C H

D P C C H


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Figure 3 Setting of target SIR

Note that in soft handover, the signal quality used by RNC as the basis is the signal

quality after the signal combination of each path in macro diversity. Because of the

existence of macro diversity, the final signal quality can be seen only in RNC. Therefore,

it is necessary for RNC to participate in outer loop power control. The following figure is

the schematic diagram of uplink power control, where the principle of outer loop power

control can be seen. The frequency of outer loop control is 10 to100HZ, and the specific

value depends on the data block adopted in the channel quality estimation.

D P D C H

F a s t p o w e r c o n t r o l

1 . 5 k H z )


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Figure 4 Outer loop power control process of uplink dedicated channel

Currently, the outer loop power control algorithm adopted in our system is based on BLER

when it is not DXT. The control method is:

Suppose that the mean value of BLER is BLERmean(n+1) over the (n+1)th

adjustment

period of outer loop power control, the target SIR value obtained in the (n+1)th

cycle will be:

factorstepdownBLER

nBLERnSIRnSIR

tar

meantar

)1

)1(()()1(

Where, BLERtar is the target BLER value; stepdown is the adjustment step of outer loop

power control (the decrease step of the target signal-to-interference ratio when the error block is

0); factor is the adjustment factor of the outer loop power control. Those parameters can beadjusted on the field, and they are configurable algorithm parameters.

In an SIR adjustment conversation, the adjustment amplitude should not be too big. The

increase amplitude should be smaller than or equal to the maximum stepup (MaxSirStepUp) and

the decrease amplitude should be smaller than or equal to maximum stepdown

(MaxSirStepDown). In connection admission, the maximum and minimum target SIR values will

be given, and the actual target SIR value should be within the maximum and minimum ranges.

When the actual SIR is higher than the target SIR value without convergence, do

not further decrease the target SIR value; when the actual SIR is lower than the target

SIR value without convergence, do not further increase the target SIR value.

Returning

2.1.5 Slow Power Control

Slow power control is the content in R4, which will not be described in this

document. The following is just an overview.

The typical application of slow power control is network browsing. At this time,

downlink sends large quantity of data packets, while uplink has only a few data such asACK. When slow power control is adopted, commands are sent from the network side at

first and are verified at the UE side. When UE is not in the soft handover state, usually,

fast closed loop power control will stop, and the slow power control system will start.

Under this mode, UE sends PCR (Power Control Ratio) on DPCCH at the interval of

TRINT. When UE has not any information, the uplink transportation will be stopped, and it


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will be resumed when UE sends PCR. NodeB identifies the downlink DPCCH/DPDCH

transmission power according to PCR reported by UE.

After the uplink transportation is paused, TPC commands of downlink DPCCH are all in dummystate, and filled with 1. UE sends dummytimeslot composed of only DPCCH before radio framescomposed of DPDCH and DPCCH. The dummy timeslot is NDS, and the TPC command in dummytimeslot contains only 1s.

3 Call Admission Control

WCDMA is an interference limited system, after a new call is admitted, the system load will beincreased

If a cell is high loaded, a new call will cause ongoing user dropped We must keep the coverage planned by the Radio Network Planning

CAC is needed under such scenarios:

1. New call2. New RAB(s) for ongoing call3. Handover4. Bandwidth increasing reconfiguration (AMRC, DCCC)

The admission decision is based on:

Cell available code resource: managed in RNC Cell available power resource: DL/UL load measured in Node B NodeB resource state, that is, NodeB credits : Reported by Node B Available Iub transport layer resource, that is, Iub transmission bandwidth: managed in RNC HSDPA user number (only for HSDPA service) HSUPA user number (only for HSUPA service)


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For handover services, the code resource admission is successful if the current remaining code resource is

enough for the service.For other R99 services, RNC shall ensure the remaining code does not exceed the configurable OM thresholds

after admission of the new service.

For HSDPA services, the reserved codes are shared by all HSDPA services; so the code resource admission isnot needed. The RNC adjusts the reserved HS-PDSCH codes according to the real-time usage status of the

codes.


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3.1 CAC Tuning

Set this parameter through ADD CELLCAC, query it through LST CELLCAC, and modify it through MOD

CELLCAC.DLHOCECODERESVSF (Dl HandOver Credit and Code Reserved SF):

This parameter is the Downlink Credit and Code Reserved by Spread Factor for Handover service. SFOFFmeans that none of them are reserved for Handover.

If the DL spare resource can not satisfy the reserved resource after the access of a new service, the service will

be rejected.

The parameter of [Dl HandOver Credit and Code Reserved SF] must be not less than the either of[Dl LDR

Credit SF reserved threshold] and [Cell LDR SF reserved threshold].The parameters of [Dl LDR Credit SF reserved threshold] and [Cell LDR SF reserved threshold] are set in

ADD CELLLDR and MOD CELLLDR, and they can be listed by LST CELLLDR.

Algorithm 1: based on UL/DL load measurement and load prediction (RTWP and TCP) The algorithm is easy to implement, but it is affected by the result of RTWP and TCP

measurement

Algorithm 2: based on Equivalent Number of User (ENU) The algorithm is no need to measure RTWP and TCP, but the calculation is more complex

Algorithm 3: loose call admission control algorithm Similar to algorithm 1, but the prediction of needed power of a new call will be set to zero

Pn is uplink receive background noise.

The procedure for uplink power resource decision is as follows:1. The RNC obtains the uplink RTWP of the cell, and calculate the current uplink load factor.2. The RNC calculates the uplink load increment UL based on the service request.3. The RNC uses the formula UL,predicted=UL + UL to forecast the uplink load factor.4. By comparing the forecasted uplink load factor UL,predicted with the corresponding threshold (UL

threshold of Conv AMR service, UL threshold of Conv non_AMR service, UL threshold of other

services, UL Handover access threshold), the RNC decides whether to accept the access request or

not.

The procedure for downlink power resource decision is as follows:

1. The RNC obtains the cell downlink TCP, and calculates the downlink load factor by multiplying themaximum downlink transmit power by this TCP.

2. The RNC calculates the downlink load increment P based on the service request and the currentload.3. The RNC forecasts the downlink load factor.4. By comparing the downlink load factor with the corresponding threshold (DL threshold of Conv AMR

service, DL threshold of Conv non_AMR service, DL threshold of other services, DL Handover

access threshold), the RNC decides whether to accept the access request or not.

The ENUmax of DL is very different from the ENUmax of UL.

The UL ENUmax is calculated by the system automatically.The DL ENUmax can be configured through parameter:


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DL total Non-HSDPA equivalent user number

The procedure for ENU resource decision is as follows:1. The RNC obtains the total ENU of all exist users ENUtotal.2. The RNC get the ENU of the new incoming user ENUnew.3. The RNC forecast the ENU load.4. By comparing the forecasted ENU load with the corresponding threshold (the same threshold as

power resource), the RNC decides whether to accept the access request or not.

Set CAC Algorithm Switch through ADD CELLALGOSWITCH, query it through LST

CELLALGOSWITCH, and modify it through MOD CELLALGOSWITCH .The algorithms the above values represent are as follow:

ALGORITHM_OFF: Disable uplink (or downlink) call admission control algorithm.

ALGORITHM_FIRST: The load factor prediction algorithm will be used in uplink (or downlink) CAC.ALGORITHM_SECOND: The equivalent user number algorithm will be used in uplink (or downlink) CAC.

ALGORITHM_THIRD: The loose call admission control algorithm will be used in uplink (or downlink) CAC.


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4 UMTS Handover Control


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4.1 Function Introduction

The cell handover strategy is required in UMTS to implement the mobility management of RRC connection

due to the mobility of UE. It is also required to balance traffic among cells to lower traffic in heavily-loaded

cell. The service connection must not be interrupted and QoS must be met during handover.

In the process of handover:

The handover in which a UE retains radio connection with the original cell while

establishing radio connection in a new cell is referred to as soft handover.

During soft handover, if the new and original cells are located under the same NodeB,

this type of handover is referred to as softer handover.

If UE needs to disconnect link with the original cell before setting up a link

(synchronization) with the new cell (that is, new and original links do not co-exist in

UE), this type of handover is referred to as hard handover.

A interruption will occur to UE transmitting and receiving at the time of hard handover. Therefore, the hard

handover may affect the QoS.

The handover may also be further classified into intra-frequency handover, inter-frequency handover and Inter-RAT handover based on different cell frequency features/access technologies before and after handover. A UE

in a connection mode can only receive the service data of single frequency, but the soft handover/softerhandover requires the UE to retain radio link with several cells concurrently, so soft/softer handover must be

intra-frequency handover. But the handover between cells in the same frequency may not necessarily be

soft/softer handover, and it may be hard handover. The inter-frequency/Inter-RAT handover is hard handoverwithout fail because of the change of carrier frequency/frequency band. Generally a UE has only one set of

receiver/transmitter, so the compressed mode is necessary for inter-frequency/Inter-RAT measurement. Thefollowing table lists the correspondence between handover and compressed modes.

Table 4.1-1 Correspondence between handover and compressed modes

Softer

handoverSoft handover

Hard

handover

Require compression or not

Intra-frequency Y Y Y N

Inter-frequency N N Y Y

Inter-RAT N N Y Y

The handover generally involves three steps: measurement, handover decision and handover implementation.The measurement is the prerequisite for handover, the handover decision is the core of handover and the

handover implementation is the process of implementing the handover decision.


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4.2 Soft/Softer Handover

In a soft handover, a UE maintains several radio links with different NodeBs, while in a softer handover, a UE

concurrently maintains radio link with several cells in a NodeB, and these several cells are also known as

macro diversity.

The soft/softer handover can only occur in intra-frequency cells. Compared with the hard handover, thesoft/softer handover features are as follows:

The soft and softer handovers are seamless handovers and no service will be

interrupted during handover.

Macro diversity gain: When a UE maintains radio links with several cells, the

receiver may enhance the accuracy of data receiving and link receiving quality and

lower the transmit power of all links by combining the signal receiving results of

several links.

The best cell where UE is registered may establish a radio connection with the UE in

time so as to lower the transmit power of UE.

In view of the above features, the soft and softer handovers will be taken in intra-frequency handover in

general.

4.3 Inter-Frequency Hard Handover

Inter-frequency hard handover means a UE in connecting state hands over from a cell on a frequency ofUTRAN to another cell on another frequency.

The factors triggering inter-frequency hard handover include radio quality, load, and moving speed of UE.

Inter-frequency hard handover triggered by radio quality: Initiate inter-frequency measurement when the

quality of frequency where UE is currently located worsens, and handover UE to the frequency with betterquality based on inter-frequency measurement results.For non-double-receiver terminals in UMTS, the compressed mode must be initiated for inter-frequency

measurement. The initiation of compressed mode has some impact on the performance of both system and

UE,.Therefore, compressed mode must be initiated only when necessary (for example, when the quality ofcurrent serving carrier frequency worsens).

4.4 Inter-RAT Mobility

Inter-RAT mobility refers to the mobility management conducted when a UE switches from one UMTS to

another one. Here it only applies to the mobility management for UE to switch from UTRAN to GERAN (the

mobility management from GERAN to UTRAN belongs to the strategy of GERAN).

This function requires UE to support both UMTS and GSM, Moreover, the GSM also needs to offer relatedfunctions to support Inter-RAT handover. The functions required by UMTS are described below.

UMTS-to-GSM handover supports the following services:

Conversational services

Videophone service fallback to ordinary voice service. (3GPP R6)

PS transferred to GPRS/GERAN


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For UMTS-to-GSM handover involving CS and PS RAB combination, the system first switches CS service to

GERAN first, and then RNC releases the PS on lu interface upon receiving the context request message from

CN.The UE activates the PS service on GERAN upon the release of CS service.In UMTS:

UTRAN-to-GERAN mobility of CS service in connected mode is implemented

through CS service handover procedure

UTRAN-to-GERAN mobility of PS service in CELL_DCH state is implemented

through cell reselection procedure (PS service handover) triggered on the network

side

UTRAN-to-GERAN mobility of PS service in CELL_FACH /URA_PCH state is

implemented through cell reselection procedure triggered by UE

Load-based UTRAN-to-GERAN handover of PS service in CELL_FACH state is

implemented through cell reselection procedure triggered on the network side

Inter-system mobility in connected mode must be accompanied by inter-system

relocation

For non-double-receiver terminals in UMTS, the compressed mode must be initiated for Inter-RAT

measurement. Initiation of compressed mode has some impact on the performance of both system and

UE.Therefore, compressed mode must be initiated only when necessary (for example, when the quality of

current serving carrier frequency worsens).

4.5Inter-RNC Handover with Iur Support

The feature supports maintaining communication continuity in the case of a UE in CELL_DCH state moving

among inter-RNC cells. Iur interface is configured between different RNCs to support that a UE maintains the

original connection with the CN when handing over in the coverage areas of different RNCs. There is no need

to trigger the SRNS relocation, so as to reduce the effects of SRNS relocation on service quality.

4.6 Coverage Based Handover

The feature supports utilizing the measurement report to judge the quality of radio link and thus to performhandover to guarantee the service quality of the user in the case of changing network coverage condition.

RNC supports controlling the UE to perform the intra-frequency, the inter-frequency and the inter-RAT

measurement and judges the radio link quality according to the measurement resultof event triggerred report to

trigger various handovers: soft/softer handover, intra-frquency hard handover, inter-frequency hard handoverand inter-RAT handover. RNC also supports configuating different handover parameters for different services.

4.7 Compressed Mode

For non-double-receiver terminals in UMTS, the compressed mode must be initiated for Inter-RAT/inter-

frequency measurement. The use of compressed mode means some timeslots are specially used for inter-

frequency/Inter-RAT measurement instead of data transmission during transmitting and receiving.


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4.8 Neighboring Cells Priorities

The feature supports configuring different priorities for different cells in adjacent cell list. It makes a UE hand

over to an adjacent cell of high priority at a higher success rate to improve the handover performance of the

system.

4.9 SRNS Relocation

This feature supports that a UE in the CELL_DCH state transfers service to a new RNC when moving among

adjacent RNC cells. When there is not Iur interface between RNCs, SRNS relocation can maintain continuous

service. When there is Iur interface between RNCs, SRNS relocation triggered timely can reduce the

transmission resource consumption at the Iur interface


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5 Compressed Mode Strategy

For non-double-receiver terminals in UMTS, the compressed mode must be initiated for Inter-RAT/inter-

frequency measurement. The use of compressed mode means some timeslots are specially used for inter-

frequency/Inter-RAT measurement instead of data transmission during transmitting and receiving. There arethe following two ways to generate compressed mode frames:

1. Halving of Spreading Factor (SF)

By halving the SF, the bandwidth can be increased so that some timeslots in one radio frame can be speciallyassigned for inter-frequency/Inter-RAT measurement and some can be specially assigned for data

transmission. This transmission strategy is generally used in services which raise high requirements for delay

and assurance of minimum data rate, for example, CS- and S-type PS data services.

2. Higher Layer Scheduling

The higher layer scheduling is in nature a strategy in which the higher layer adjusts and controls the data

transmission rate. Some timeslots in a radio frame can be specially assigned for inter-frequency/Inter-RAT

measurement and some can be specially assigned for data transmission while the bandwidth remainsunchanged. This strategy is generally used for non-realtime services with low requirements for delay, for

example, I/B-type PS data services.


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6 Intra-Frequency Handover Strategy

Intra-frequency handover refers to the handover performed between cells under the same frequency of

UTRAN. The intra-frequency handover can be triggered based on Ec/N0 or RSCP measurement through the

parameterIntraMeasQuan.Intra-frequency handover is measurement-based handover. Intra-frequencymeasurement contains active set measurement, monitored set measurement and detected set measurement.

The active set refers to the collection of cells retaining radio connection with UE.The monitored set refers to the collection of cells retaining no radio connection with UE but requiring

measurement by sending the intra-frequency measurement control message to UE.

The detected set refers to the collection of intra-frequency cells except cells in the active set and monitored set.

6.1 Intra-Frequency Measurement

When conducting intra-frequency measurement, the UE needs to implement layer 3 filter for the measurement

results to avoid measurement fluctuation and then make event decision and report by using filtered values. The

layer 3 filter formula is as follows:

nnn MaFaF 1)1(

Where,

Fn-1refers to the result of last filter.

Fnrefers to the result of current measurement filter.

Mnrefers to current measurement result.

a = 1/2(k/2)

refers to the filter coefficient calculated based on the filter factor K (FilterCoeff (Intra)).

6.1.1 Introduction to Intra-Frequency Measurement

Intra-frquency measurement means to perform measurement on intra-frequency cells. Only event-basedmethod of reporting measurement result is supported, and parameter SofthoMthd is invalid. The event-based

report method means the UE judges whether intra-frequency events are met based on the quality measurement

result of cell PCPICH.If so, it reports intra-frequency events (including such information as event ID, andtarget cell) to the RNC.

A series of intra-frequency measurement events are defined in 3GPP as the judgment and trigger criteria for

intra-frequency handover.Event 1A: A Primary CPICH enters the Reporting Range. It can be used for adding cell to the active set.

Event 1B: A Primary CPICH leaves the Reporting Range. It can be used for deleting cell from the active set.Event 1C: A Non-active Primary CPICH becomes better than an active Primary CPICH. It can be used for

replacing the cell with bad quality in the active set.

Event 1D: The best cell changes. It can be used for soft/softer handover, intra-frequency hard handover and

inter-frequency load balance.

6.1.2 Neighboring Cells Configuration

In neighboring cells configuration, adjacent cell list used for reselection in non-CELL_DCH state and that used

for handover in CELL_DCH state can be configured separately. In handover, target cells are chosed by

neighboring cells configuration state (StateMode). When UE in macro diversity state, the neighboring cell listis the union of neighboring cell list of each cell active set, then the number of intra-frequency neighboring cells

may exceed 32 which is the maximum number regulated by protocol. If the number of intra-frequency


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neighboring cells exceeds 32, it needs to delete some cells to ensure that there are only 32 intra-frequency

neighboring cells.

6.2 Intra-Frequency Handover Decision

6.2.1 Event 1A-Triggered Handover

Event 1A means the quality of certain cell outside the active set ameliorates. Upon receiving Event 1A, the

RNC adds corresponding target cell into the active set to enhance the gain of macro diversity. When the cell

meets the conditions in the following formula, the UE reports Event 1A to the RNC.

/2)H(RLogM10W)(1MLog10WCIOLogM10 1a1aBest

N

1iiNewNew

A

The meanings of all parameters are described as follows:R1a: Refers to the reporting range of Event 1A. It is used to control the extent of difficulty in adding a cell into

the active set (RptRange [MAX_INTRA_MEAS_EVENT]).

H1a: Refers to the reporting hysteresis of Event 1A. It is used to control the extent of difficulty in adding a cell

into the active set (Hysteresis[MAX_INTRA_MEAS_EVENT] (Intra)).

MNew:Refers to measurement of the to-be-evaluated cell outside the active set.

CIONew: Refers to offset of cell outside active set in relation to other cells (CellIndivOffset(utranRelation)).

Mi:Refers to the mean measurement value of other cells except the best cell in active set.

NA:Refers to the number of other cells except the best cell in active set.MBest: Refers to the measurement of the best cell in the active set.

W:Refers to the weight proportion (W[MAX_INTRA_MEAS_EVENT]) of the best cell to the rest cells in the

active set in evaluation standards.

As can be calculated from the above formula, you can increase the probability of triggering Event 1A by either

increasing R1a(Event 1A meets the reporting range conditions) or decreasing H1a(Decision hysteresis

range.Otherwise, you can reduce the probability of triggering Event 1A.

Event 1A supports period-based report, that is, once Event 1A meets the reporting range of quality standards,

the UE will report Event 1A periodically (EvtRptInterval[MAX_INTRA_MEAS_EVENT]) until this event doesnot meet reporting conditions or the reporting times reach the maximum allowed times

(EvtRptAmount[MAX_INTRA_MEAS_EVENT]).

There is restriction on the number of radio links in active set, so Event 1A will not be reported once the

number of cells in the active set reaches certain threshold (RptDeactThr[MAX_INTRA_MEAS_EVENT]).

6.2.2 Event 1B-Triggered Handover

Event 1B indicates the quality deterioration of certain cell in the active set. Upon receiving the Event 1B, the

RNC may delete the cell from the active set. When the cell meets the conditions in the following formula, theUE reports Event 1B to the RNC.

/2)H(RLogM10W)(1MLog10WCIOLogM10 1b1bBest

N

1i

iOldOld

A

R1b: Refers to the reporting range of Event 1B. It is used to control the extent of difficulty in dropping a cellfrom the active set (RptRange [MAX_INTRA_MEAS_EVENT]).

H1bRefers to the reporting hysteresis of Event 1B. It is used to control the extent of difficulty in dropping a

cell from the active set (Hysteresis[MAX_INTRA_MEAS_EVENT] (Intra)).

MOld:Refers to measurement of the to-be-evaluated cell in the active set.

CIOOld: Refers to offset of cell in active set in relation to other cells (CellIndivOffset(utranCell)).

Mi:Refers to the mean measurement value of other cells except the best cell in active set.

NA:Refers to the number of other cells except the best cell in active set.


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MBest: Refers to the measurement of the best cell in the active set.

W:Refers to the weight proportion (W[MAX_INTRA_MEAS_EVENT]) of the best cell to the rest cells in the

active set in evaluation standards.As can be calculated from the above formula, you can decrease the probability of triggering Event 1B by either

increasing R1b(Event 1B meets the reporting range conditions) or decreasing H1b(Decision hysteresis range).Otherwise, you can increase the probability of triggering Event 1B.

6.2.3 Event 1C-Triggered Handover

Event 1C indicates the quality of a cell in non-active set is better than that of a cell in certain active set. Uponreceiving Event 1C, the RNC may replace the cell in the active set with a cell in non-active set to obtain better

gain of macro diversity. When the cell meets the conditions in the following formula, the UE reports Event 1C

to the RNC.

/2HCIOLogM10CIOLogM10 1cInASInASNewNew

H1cRefers to the reporting hysteresis of Event 1C. It is used to control the extent of difficulty in replacing a

cell in the active set (Hysteresis[MAX_INTRA_MEAS_EVENT] (Intra)).

MNew:Refers to measurement of the to-be-evaluated cell outside the active set.

MInAS: Refers to the cell with poorest quality in the active set.CIONew: Refers to offset of the to-be-evaluated cell outside the active set in relation to other cells(CellIndivOffset(utranRelation)).

CIOInAS: Refers to offset of cell with poorest quality in active set in relation to other cells (CellIndivOffset

(utranCell)).As can be calculated from the above formula, you can decrease the probability of triggering Event 1C by

increasing H1c(decision hysteresis range); otherwise, you can increase the probability of triggering Event 1C.

Event 1C supports period-based report, that is, once Event 1C meets the reporting range of quality standards,the UE will report Event 1C periodically (EvtRptInterval[MAX_INTRA_MEAS_EVENT]) until this event does

not meet reporting conditions or the reporting times reach the maximum allowed times

(EvtRptAmount[MAX_INTRA_MEAS_EVENT]).

To ensure the gain of macro diversity, the report of Event 1C is only allowed when the number of cells in the

active set reaches certain threshold (RplcActThr[MAX_INTRA_MEAS_EVENT]).

6.2.4 Event 1D-Triggered Handover

Event 1D indicates the quality of certain cell within or outside current active set is better than the best cell in

current active set, that is, the best cell changes in the active set. The following can be triggered upon the receiptof Event 1D:

Add a cell into the active set (the cell outside the active set reports Event 1D and the

number of links in the active set does not reach the maximum).

Replace the cell with bad quality in active set (the cell outside the active set reports

Event 1D but the number of links in the active set reaches the maximum).

The serving cell changes (for HS-DSCH/E-DCH).

When the cell meets the conditions in the following formula, the UE reports Event 1D to the RNC.

/2HCIOLogM10CIOLogM10 1dBestBestNotBestNotBest

MNotBest: Refers to the measurement of the to-be-evaluated cell within or outside the active set.

CIONotBest: Refers to the offset of the to-be-evaluated cell within the active set (CellIndivOffset(utranCell)) or

outside the active set (CellIndivOffset (utranRelation)) in relation to other cells.


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CIOBest: Refers to offset of the to-be-evaluated cell in the active set in relation to other cells (CellIndivOffset

(utranCell)).

MBest: Refers to the measurement of the to-be-evaluated cell in the active set.

H1d: Refers to Event 1D report hysteresis (Hysteresis[MAX_INTRA_MEAS_EVENT] (Intra)).

As can be calculated from the above formula, you can decrease the probability of triggering Event 1D byincreasing H1d(decision hysteresis range); otherwise, you can increase the probability of triggering Event 1D.

6.2.5 CIO Configuration Strategy

The CIO (Cell individual offsets) defined by 3GPP is used to control the difficulty of event triggering . Andthe tendency of handover can be also controlled by CIO in actual scenario.

The CIO principals of target cell are described as follows.

If there is neighboring relationship between target cell and best cell , the CIO is chose

from the best cell (utranRelation, externalGsmCell). If there is not any neighboring

relationship between target cell and best cell, the CIO is the minimum of absolute

values chose from the cells(utranRelation, externalGsmCell) in active set. If there is

not any neighboring relationship between target cell and cells in active set, the CIO is

set to zero.

If target cell is the best cell, the CIO is chose from the serving cell (utranCell).

If the best cell changes, RNC will inform UEs to update CIO.

6.2.6 Time-To-Trigger Mechanism Used to Control Event Report

If a to-be-evaluated cell meets the reporting range or threshold of certain event, the condition must be met

within a period of time (TrigTime[MAX_INTRA_MEAS_EVENT] (Intra)) before the reporting of this event to

avoid intra-frequency event misreport due to the fluctuation of radio quality. Take Event 1A as an example,

suppose a cell meets the reporting range, the UE only reports Event 1A only if the cell quality meets this

reporting range condition within TrigTime[MAX_INTRA_MEAS_EVENT] (Intra).

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