Oeo106060 Lte Eran3.0 Handover Feature Issue1.00

3.0 (Update to eRAN3.0 feature)

( Add more message tracing )

(Add muti-band mobility deployment policy)

LTE eRAN3.0 Load Control Feature

Confidential Information of Huawei. No Spreading Without Permission

LTE eRAN3.0 Handover Feature


Mobility management is classified into mobility management in idle mode and mobility

management in connected mode, based on RRC states. A UE with an RRC connection to

the radio network is considered to be in connected mode. In the case of mobility

management in connected mode, an eNodeB delivers the associated configuration through

signaling on the control plane, and UEs perform measurements accordingly and complete

the handover procedures under the control of the eNodeB, thus ensuring uninterrupted

service provision.

In the case of mobility management in connected mode, the mobile network ensures

continuity of physical channels and provides uninterrupted communications service for UEs

in connected mode through handovers when the UEs are moving in the network. A

handover is a procedure where the serving cell of a UE in connected mode is changed.

Handovers can be classified into intra-frequency handover, inter-frequency handover, and

inter-RAT handover.



All the handover involve 3 setups

Measurement step: UE strart intra-frequency or inter-frequency measurement

according to the different triggers

Decision step: eNodeB make handover decision according to the resource state and

related parameters

Execution step: eNodeB send execution command to UE to perform handover

The relative parameters can be automatically optimized by MRO



Different types of handover measurement are triggered by different causes, as shown

above



When a UE establishes a radio bearer, the eNodeB delivers the intra-frequency

measurement configuration to the UE through an RRC Connection Reconfiguration

message by default. Then, the UE performs intra-frequency measurements by default.

When measurement gaps need to be set up, the eNodeB delivers the inter-frequency

and/or inter-RAT measurement configuration to the UE. After that, the UE performs gap-

assisted inter-frequency and/or inter-RAT measurements. Inter-frequency and inter-RAT

measurements can use the same gap pattern, but the eNodeB is able to differentiate

between the gap configurations for inter-frequency and inter-RAT measurements.



Related commands



The concept of event-triggered reporting as specified in 3GPP is used by the measurement

and decision phases of handovers. Reporting configurations consist of the parameters

related to specific events. Currently, the eNodeB supports mechanisms as responses to the

above events.

In the report configuration IE, eNodeB should deliver all the relevant for event based

report. After eNodeB receive specific report, it will implement corresponding action

Each event has the individual report configuration with the unique report configuration ID.



Before evaluating the reporting criteria and sending measurement reports, the UE performs

layer 1 (L1) filtering and L3 filtering on the measurement results. The L1 filtering is

performed by the UE at the physical layer to eliminate the impact of fast fading on the

measurement results. No user configuration is required for the L1 filtering. The L3 filtering

aims at eliminating the impact of shadow fading and certain fast fading. In this way, better

measurement data can be provided for the evaluation of the reporting criteria. Based on

the triggering quantity, two L3 filtering coefficients are applicable: one for RSRP

measurements and the other for RSRQ measurements.



A measurement gap is a time period during which the UE performs measurements on a neighboring

frequency of the serving frequency. Measurement gaps are applicable to inter-frequency and inter-

RAT measurements. The UE performs inter-frequency or inter-RAT measurements only within the

measurement gaps. One UE normally has only one receiver, and consequently one UE can receive

the signals on only one frequency at a time.

When inter-frequency or inter-RAT measurements are triggered, the eNodeB delivers the

measurement gap configuration, and then the UE starts gap-assisted measurements accordingly. As

shown above, Tperiod denotes the repetition period of measurement gaps, and TGAP denotes the gap

width, within which the UE performs measurements.

Gap-assisted measurements for the following types of handover may co-exist: coverage-based, load-

based, and service-based handovers. When two or all of the preceding types of gap-assisted

measurement co-exist, the eNodeB records the measurements based on these types. These different

types of measurement are called member gap-assisted measurements. The member gap-assisted

measurements can share the measurement gap configuration. A UE releases measurement gaps

only when all member measurements are stopped.

There are two measurement gap patterns available: pattern 1 and pattern 2. In pattern 1, TGAP is 6

ms and Tperiod is 40 ms. In pattern 2, TGAP is 6 ms and Tperiod is 80 ms. The pattern to be used is

specified through the GapPatternType parameter.



A neighboring relation is a relation between the serving cell and each candidate cell involved in a

handover. Neighboring relation management covers the following aspects:

Whether to allow automatic removal of a neighboring relation by ANR or not

Whether to allow handovers of UEs between two cells or not

Whether to allow handovers over an X2 interface or not

Neighboring relations are planned in the network design stage. They can be automatically adjusted

by ANR. The ANR function reduces the risk of missing neighboring cells and solves the problems of

inappropriate neighboring relations caused by collisions of physical cell IDs or by physical positions.

In this way, the call drop rate is reduced and the handover success rate is increased.

Intra-frequency neighboring cell

An intra-frequency neighboring cell is a neighboring cell whose DL E-UTRA Absolute Radio

Frequency Channel Number (EARFCN) is the same as the DL EARFCN of the serving cell. An

E-UTRAN cell can be configured with a maximum of 32 intra-frequency neighboring cells.

Inter-frequency neighboring cell

An inter-frequency neighboring cell is a neighboring cell whose DL EARFCN is different from

the DL EARFCN of the serving cell. An E-UTRAN cell can be configured with a maximum of

64 inter-frequency neighboring cells, which can be located on a maximum of 8 neighboring

E-UTRAN frequencies. TDD cells can also be configured as inter-frequency neighboring cells

of FDD cells. Huawei eNodeB supports interoperability between LTE FDD and LTE TDD.



Inter-RAT neighboring cell

Inter-RAT neighboring cells are neighboring UTRAN cells, neighboring GERAN cells,

and neighboring CDMA2000 cells. The maximum configurations of neighboring

cells and frequencies for an E-UTRAN cell are as follows: 64 neighboring UTRAN

cells and 16 neighboring UTRAN frequencies; 64 neighboring GSM cells and 16

neighboring GSM frequency groups; 32 neighboring CDMA2000 EVDO cells and

32 neighboring CDMA2000 1x cells.

Black cell:

Blacklisted cells are not considered in event evaluation or measurement reporting.

This list should be configured manually and delivered to UE via SIB



The handover switch can be modified by the following command:



Each object has a unique ID, and the object is mapping with frequency number but not

cell. If some neighbors for this object is configured, then you can also find the neighbor

info to simplify UE measurement



Mn: The measurement result of the neighboring cell

Ofn: The frequency-specific offset for the frequency of the neighboring cell, it is not valid

during intra-frequency handover.

Ocn: The cell-specific offset (that is, CIO) for the neighboring cell, related command: MOD

EUTRANINTERFREQNCELL

Ms: The measurement result of the serving cell

Ofs: The frequency-specific offset for the serving frequency

Ocs: The cell-specific offset for the serving cell

Hys: The hysteresis for event A3. It is specified through the IntraFreqHoA3Hyst

parameter and contained in the delivered measurement configuration.

Off: The offset for event A3. It is specified through the IntraFreqHoA3Offset parameter.

If the entering condition of the event is continuously met during the time specified through

IntraFreqHoA3TimeToTrig, the UE reports event A3 and starts the event-triggered

periodical reporting. Then, if the leaving condition of the event is continuously met during

the time specified through IntraFreqHoA3TimeToTrig, the UE stops reporting event A3.



Load based HO is controlled by MLB module which is enabled with MlbAlgoSwitch, once

it is triggered then CIO can be modified by MLB, to easily trigger A3 event report.



After receiving a measurement report from the UE, the eNodeB generates a list of

candidate cells, which meet the triggering condition of the specific event. As a second

step, the eNodeB filters the candidate cells. If the measurement result of an intra-eNodeB

cell is the same as that of an inter-eNodeB cell among the candidate cells, the eNodeB

prioritizes the intra-eNodeB cell to prevent signaling and data forwarding required in an

inter-eNodeB handover.



In the handover execution phase, the UE and the eNodeB exchange signaling over the

radio interface according to 3GPP TS 36.331. During an inter-eNodeB handover, the

source eNodeB and the target eNodeB exchange signaling and data through X2/S1

adaptation. The LTE system uses hard handover, that is, only one radio link is connected to

a UE at a time. Therefore, to prevent user data loss at the eNodeB during the handover,

data forwarding is performed to ensure eNodeB data integrity. The loss of data may cause

a decrease in the data transfer ratio and an increase in the data transfer delay.

In the case of an intra-MME inter-eNodeB handover, the source eNodeB checks whether

the X2 interface is available between the source and target eNodeBs or not and then

automatically selects a path for the handover as follows:

If the X2 interface is available, the handover request is sent over the X2 interface.

Data forwarding is also performed over the X2 interface.

If the X2 interface is unavailable, the handover request is sent over the S1

interface. Data forwarding is also performed over the S1 interface.

In the case of an inter-MME inter-eNodeB handover, the handover request is sent over the

S1 interface. In addition, the source eNodeB checks whether the X2 interface is available

between the source and target eNodeBs or not and then automatically selects a path for

data forwarding as follows:

If the X2 interface is available, data forwarding is performed over the X2 interface.

If the X2 interface is unavailable, data forwarding is performed over the S1

interface.



The data forwarding process is as follows: After the source eNodeB sends a handover

command to the UE, the UE detaches the connection from the source eNodeB. The source

eNodeB then forwards the uplink (UL) data that is received out of order and the DL data to

be transmitted, to the target eNodeB.

Data forwarding prevents a decrease in the data transfer ratio and an increase in the data

transfer delay that are caused by user data loss during the handover.

Intra-eNodeB handovers do not require data forwarding. In the case of inter-eNodeB

handover, the source eNodeB selects a data forwarding path by using the X2/S1

adaptation mechanism.

In the case of an inter-RAT handover to UTRAN or GERAN, the eNodeB checks whether the

core network supports direct forwarding or not and then selects a data forwarding path

accordingly. If the core network supports direct forwarding, the eNodeB directly forwards

the data to the target Radio Network Controller (RNC) in the case of UTRAN or to the

target Serving GPRS Support Node (SGSN) in the case of GERAN, so as to shorten the data

forwarding time. If the core network does not support direct forwarding, the eNodeB

sends the data to the Serving Gateway (S-GW).

In the case of an inter-RAT handover to CDMA2000, the eNodeB sends the data to the S-

GW.

LTE Handover Feature


Specific Cell Individual Offset (CIO) values can be set for the serving cell and its neighboring

cells. (Ocs and Ocn described in the subsequent chapters denote the CIO for the serving

cell and the CIO for the neighboring cell respectively.) When the quality of signals

fluctuates, the probability of triggering handovers to or from a specific cell can be adjusted

by changing the value of CIO. This reduces the risk of call drops. The CIO values can be

adjusted automatically by the MRO function.



Each parameters are described as below:

Max report cell number: Indicates the maximum number of cells to be included in

the measurement report after an event for the intra- or inter-frequency handover

within the E-UTRAN is triggered.

Measurement report amount: Indicates the number of periodic measurement

reports to be sent after an event for the intra- or inter-frequency handover within

the E-UTRAN is triggered. It is used to prevent the impact of measurement report

loss and internal processing failure on the handover.

A3 measurement trigger quantity: Indicates the quantity used to evaluate the

triggering condition for the intra-frequency handover event. The quantity can be

RSRP or RSRQ. Recommended value: RSRP

A3 measurement report quantity: Indicates the quantity to be included in the

measurement report for the intra-frequency handover event

Intrafreq measurement report interval: Indicates the interval between each periodic

report

Measurement A4 report quantity: The same meaning as A3 measurement

A1A2 Measurement trigger quantity: The same meaning as A3 measurement

Interfreq measurement report interval: The same as itrafreq measurement report

interval



In LTE, 9 QCI are defined as QoS level. Each QCI is mapped with a series handover group.

The related command is : MOD CELLSTANDARDQCI

The main parameters for intra-handover decision algorithm are shown as following

Intrafreq handover hysteresis: Indicates the hysteresis to be used in the triggering

condition for the intra-frequency handover event. This parameter helps reduce the

number of times the event is triggered because of radio signal fluctuation. Thus,

the probability of ping-pong handovers or wrong handover decisions is reduced.

Intrafreq handover offset: Indicates the quality offset of the neighboring cell over

the serving cell to be used in the triggering condition of the intra-frequency

handover event.

Intrafreq handover time to trigger: Indicates the time-to-trigger for intra-frequency

handover event A3.When detecting that the signal quality in the serving cell and

that in at least one neighboring cell meet the entering condition, the UE does not

send a measurement report to the eNodeB immediately. Instead, the UE sends a

report only when the signal quality continuously meets the entering condition

during the time-to-trigger



The signaling procedure shown in above figure is described as follows:

When the UE establishes a radio bearer, the source eNodeB sends the UE an RRC

Connection Reconfiguration message that contains the measurement

configuration. The measurement configuration is set by the source eNodeB to

control the measurements of the UE in connected mode.

The UE sends measurement reports to the source eNodeB based on the

measurement results.

The source eNodeB makes a handover decision based on the measurement reports.

After deciding that a handover is preferred, the source eNodeB sends a Handover

Request message to the target eNodeB, to request the target eNodeB to prepare

for the handover.

The target eNodeB makes admission decisions. If resources can be granted by the

target eNodeB, the target eNodeB performs admission control depending on the

QoS information about the Evolved Packet System (EPS) bearer.

The target eNodeB prepares L1/L2 resources for the handover and then sends a

Handover Request Acknowledge message to the source eNodeB.

The source eNodeB sends the UE an RRC Connection Reconfiguration message that

contains the mobilityControlInfo IE, indicating that the handover shall start.



The UE performs a procedure of random access towards the target eNodeB, to

achieve the UL synchronization of the UE with the target eNodeB.

After successfully accessing the target cell, the UE sends the target eNodeB an RRC

Connection Reconfiguration Complete message, indicating that the handover

procedure is complete. At this time, the target eNodeB can start sending data to

the UE.

The DL data path switching is performed.

The target eNodeB sends the source eNodeB a UE Context Release message, to

inform the source eNodeB of the success of the handover and to trigger the release

of the resources at the source eNodeB.

After receiving the UE Context Release message, the source eNodeB releases the

radio and control-plane resources associated with the UE context.



Blind HO switch:

Once blind HO is activated, eNodeB directly decide the HO target based on the priority

configuration of each neighbor



The switch for each scenario

eNodeB level switch: coverage based, service based, UL quality based

Cell level switch: frequency priority based and distance based



This execution is mandatory to for inter-frequency measurement, must be done by manual

configuration.

If it is configured, then A1/A2 event parameters will be delivered by eNB by default, thus

to trigger inter-frequency measurement.



In a coverage-based inter-frequency handover, event A2 triggers inter-frequency

measurements. The triggering of this event indicates that the signal quality in the serving

cell is lower than a specified threshold.

Ms: The measurement result of the serving cell

Hys: The hysteresis for event A2

Thresh: The threshold for event A2, it can be defined separately with RSRP or RSRQ



The triggering and stopping of inter-frequency measurements for load-based handovers

are determined by the MLB algorithm. When the load of the serving cell reaches the

threshold for inter-frequency load balancing, the MLB algorithm selects a number of UEs

based on the frequency capabilities of the UEs, ARPs, and resource usage and then

instructs the UEs to perform gap-assisted inter-frequency measurements for load-based

handovers. The MLB algorithm also determines the cells on which the measurements need

to be performed.

After load-based inter-frequency measurements are triggered, the eNodeB does not

process the outputs from the MLB algorithm if the eNodeB detects that measurement gaps

have been set up among which there are measurement gaps for other types of handover.

Otherwise, the eNodeB sets up the measurement gaps for the load-based handovers.

When the measurement gaps for load-based handovers are released, the gap-assisted

measurements for other types of handover are not affected. The measurement gap

configuration stops only when all gap-assisted measurements are stopped.



Event A1 triggers measurements for frequency-priority-based handover.

The FreqPriInterFreqHoA1TrigQuan parameter specifies the event A1 triggering

quantity for frequency-priority-based measurement, which can be either RSRP or RSRQ. If

the triggering quantity is RSRP, the threshold for this event is specified by the

FreqPriInterFreqHoA1ThdRsrp parameter. If the triggering quantity is RSRQ, the

threshold for this event is specified by the FreqPriInterFreqHoA1ThdRsrq parameter.

Other parameters related to event A1 for frequency-priority-based measurement are the

same as those for coverage-based inter-frequency measurement.

After receiving an event A1 report from a UE, the eNodeB proceeds as follows:

If frequency-priority-based blind handover is enabled,the eNodeB selects the

neighboring cell with the highest blind-handover priority to perform a handover.

However, if load balancing from that neighboring cell to the serving cell is in

progress, the eNodeB selects the neighboring cell with the second highest priority.

If the eNodeB traverses all candidate cells but fails to find a cell that fulfills the

criteria, the eNodeB will decide not to perform a handover.

If frequency-priority-based blind handover is disabled, the eNodeB delivers the

inter-frequency measurement configuration to the UE. If the triggering condition of

event A4 is fulfilled, the UE sends a frequency-priority-based event A4 report to the

eNodeB. (The triggering of event A4 for frequency-priority-based handover is

similar to that for coverage-based inter-frequency handover



Service-based inter-frequency handovers are applicable to two neighboring E-UTRAN

frequencies that cover the same area. Based on the QCIs of the services that are running

on a UE, the eNodeB can divert the UE to an appropriate co-coverage E-UTRAN frequency

by means of a service-based inter-frequency handover.

To implement service-based inter-frequency handovers, operators need to configure

service-based inter-frequency handover policies. Each service-based inter-frequency

handover policy has an ID (ServiceIfHoCfgGroupId) and specifies the frequency

(DlEarfcn) that is preferentially used to carry the services of a specific operator

(CnOperatorId). Since the services of each operator are further classified by QCIs, each

QCI can be associated with a service-based inter-frequency handover policy so that the

frequency specified by the policy preferentially carries the services with this QCI.

Service-based inter-frequency handovers are controlled by the corresponding switch under

the HoAlgoSwitch parameter. If this switch is turned on, the eNodeB triggers a service-

based inter-frequency handover for a UE based on the highest-priority QCI of the services

running on the UE. If the highest-priority QCI is associated with a service-based inter-

frequency handover policy with the InterFreqHoState parameter set to PERMIT_HO,

and there is at least one neighboring cell working on the frequency, the eNodeB delivers

the measurement configuration related to event A4 to the UE. The triggering of event A4

in service-based inter-frequency handovers is the same as that in coverage-based inter-

frequency handovers.



Related commands:



As shown above, F1 and F2 indicate two frequencies: Cell 1 uses F1, and Cells 2, 3, and 4

all use F2. The gray area in the figure (Cell 1) is covered by F1, while Cells 2, 3, and 4 is

covered by F2. It is obvious that cell 1 exerts cross-cell coverage to the other three cells.

Assume that the UE moves along the direction indicated by the arrow. As the UE moves,

F1 provides sustained signal quality and therefore inter-frequency measurements are not

triggered for the UE even when the UE has been in the coverage of F2 for a long time.

Gradually, the UE enters the overlap coverage between Cell 1 and Cell 4. Considering the

long distance between the two cells, it is unlikely that Cell 4 is configured as a neighboring

cell of Cell 1. As a result, as soon as the UE leaves the coverage of Cell 1, it experiences a

call drop. To prevent such a call drop and ensure service continuity, the UE should have

been handed over to F2 earlier.

Related command:



UL-quality-based inter-frequency handovers are triggered based on the UL quality. When

the UL quality is unsatisfactory, call drops may occur if handovers are not performed in

time. Therefore, UL-quality-based inter-frequency handovers are introduced to reduce call

drops caused by poor UL quality. The eNodeB uses the modulation and coding scheme

(MCS) and initial block error rate (IBLER) to determine the UL quality.



In this message it contain inter-frequency measurement control parameters, almost the

same as intra-frequency measurement, just one more gap configuration, used to trigger or

stop the measurement



Related command:



Mn: The measurement result of the neighboring cell.

Ofn: The frequency-specific offset for the frequency of the neighboring cell.

Ocn: The cell-specific offset for the neighboring cell.

Hys: The hysteresis for event A4

Thresh: The threshold for event A4



Each parameters are described as below:

Max report cell number: Indicates the maximum number of cells to be included in

the measurement report after an event for the intra- or inter-frequency handover

within the E-UTRAN is triggered.

Measurement report amount: Indicates the number of periodic measurement

reports to be sent after an event for the intra- or inter-frequency handover within

the E-UTRAN is triggered. It is used to prevent the impact of measurement report

loss and internal processing failure on the handover.

A3 measurement trigger quantity: Indicates the quantity used to evaluate the

triggering condition for the intra-frequency handover event. The quantity can be

RSRP or RSRQ. Recommended value: RSRP

A3 measurement report quantity: Indicates the quantity to be included in the

measurement report for the intra-frequency handover event

Intrafreq measurement report interval: Indicates the interval between each periodic

report

Measurement A4 report quantity: The same meaning as A3 measurement

A1A2 Measurement trigger quantity: The same meaning as A3 measurement

Interfreq measurement report interval: The same as itrafreq measurement report

interval



The same commands are used for inter-frequency handover as intra-frequency handover,

the main related parameters are shown as following:

Measurement parameters

Measurement A4 trigger quantity: Indicates the quantity to be included in the

measurement report for the inter-frequency handover event. The quantity can be

RSRP, RSRQ, or both.

Interfreq measurement report interval: Indicates the interval at which periodical

measurement reports are sent after an inter-frequency handover event is triggered.

A1A2 Measurement trigger quantity: Indicates the quantity used to evaluate the

triggering condition for inter-frequency measurement event A1 or A2.

QCI based parameters

Interfreq A1A2 hysteresis: Indicates the hysteresis to be used in the triggering

condition of event A1 or A2 for the inter-frequency handover.

Interfreq A1A2 time to trigger: Indicates the time-to-trigger for inter-frequency

measurement event A1 or A2.

Interfreq handover hysteresis: Indicates the hysteresis to be used in the triggering

condition of the inter-frequency handover event.

Interfreq HandOver Time to Trigger: Indicates the time-to-trigger for inter-

frequency handover event A4.



If the InterRatHoState parameter is set to MUST_HO for a QCI, the eNodeB delivers the

service-based handover measurement configuration to a UE when the UE initiates a service

with that QCI.

If the InterRatHoState parameter is set to NO_HO for a QCI, the eNodeB does not deliver

the service-based handover measurement configuration to a UE on which a service with

that QCI is running, even if the UE initiates a service for which InterRatHoState is set to

MUST_HO.

If the InterRatHoState parameter is set to PERMIT_HO for a QCI, the eNodeB does not

deliver the service-based handover measurement configuration to a UE when the UE

initiates a service with that QCI. When a service with that QCI is running on the UE, the

eNodeB delivers the service-based handover measurement configuration to the UE if the

UE initiates a service for which InterRatHoState is set to MUST_HO.

If a service-based inter-RAT handover is not initiated after the gap-assisted measurements

are performed for a relatively long time, the eNodeB instructs the UE to stop the service-

based inter-RAT measurements and release the measurement gaps.



Mn: The measurement result of the neighboring cell

Ofn: The frequency-specific offset for the frequency of the neighboring cell

Hys: The hysteresis for event B1. The hysteresis values for inter-RAT handovers to UTRAN,

GERAN, and CDMA2000



The following inter-RAT handover policies are applicable:

PS handover: is applicable to PS services. In PS handover, services are handed over

from the PS domain of the source system to the PS domain of the target system to

ensure continuous service provision.

Single Radio Voice Call Continuity (SRVCC): is applicable to voice services. In the

case of SRVCC, the services are handed over from the LTE system to the CS domain

of the target system.

Cell Change Order with or without Network Assisted Cell Change (CCO/NACC): is

specific to the GSM cases. During the CCO/NACC, the UE is ordered to switch to

the GERAN idle mode, and consequently it can try to access the GSM network. The

procedure is simple but causes a long delay. In GSM, however, the CCO/NACC

mode is a substitute for PS handover. For the CCO with NACC, the eNodeB needs

to acquire the system information from the target system and then send the

information to the UE through a handover command, thereby accelerating the UE

access to the target GSM cell.

Redirection: It is the simplest method to transfer UEs to an inter-RAT system. The

3GPP protocols stipulate that UEs that can work in another RAT also support

redirections to the RAT.



For SRVCC from E-UTRAN to UTRAN/GERAN, MME first receives the handover request

from E-UTRAN with the indication that this is for SRVCC handling, and then triggers the

SRVCC procedure with the MSC Server enhanced with SRVCC via the Sv reference point if

MME has SRVCC STN-SR information for this UE. MSC Server enhanced for SRVCC then

initiates the session transfer procedure to IMS and coordinates it with the CS handover

procedure to the target cell. MSC Server enhanced for SRVCC then sends PS-CS handover

Response to MME, which includes the necessary CS HO command information for the UE

to access the UTRAN/GERAN.



In the case of CCO/NACC to GERAN, the eNodeB directly orders the UE to switch to the

GERAN, instead of sending a handover request over the S1 interface. In the procedure

shown in the figure, steps 3 to 8 are used to request the system information of the

GERAN. They are applicable only to CCO with NACC.



Intra-frequency key parameters



Id Name Description Recommended

Value

IntraFreqHoA3

Hyst

Intrafreq

handover

hysteresis

Indicates the hysteresis for event A3. This

parameter is used to prevent frequent

triggering of event evaluation due to radio

signal fluctuation. In this way, the

probability of ping-pong handovers or

handover decision errors is reduced. A

larger value of this parameter results in a

lower probability

GUL value: 2

Actual value: 1dB

IntraFreqHoA3

Offset

Intrafreq

handover

offset

Indicates the offset for event A3. If the

parameter is set to a large value, an intra-

frequency handover is performed only

when the signal quality of the neighboring

cell is significantly better than that of the

serving cell and other triggering conditions

are met.

GUL value: 2

Actual value: 1dB

IntraFreqHoA3

TimeToTrig

Intrafreq

handover

time to

trigger

Indicates the time-to-trigger for event A3

for the intra-frequency handover.

When detecting that the signal quality in

the serving cell and that in at least one

neighboring cell meet the entering

condition, the UE does not send a

measurement report to the eNodeB

immediately. Instead, the UE sends a

report only when the signal quality

continuously meets the entering condition

during the time-to-trigger.

This parameter helps decrease the number

of occasionally triggered event reports, the

average number of handovers, and the

number of wrong handovers. In summary,

it helps prevent unnecessary handovers.

320ms

CellIndividualO

ffset

Cell

individual

offset

Indicates the cell-specific offset for the

intra-frequency neighboring cell. It affects

the probability of triggering intra-frequency

measurement reports. A larger value of

this parameter indicates a higher

probability.

dB0

Inter-frequency key parameters



Id Name Description Recomm

ended

Value

InterFreqHoA

1A2Hyst

Interfreq

A1A2

hysteresis

Indicates the hysteresis for inter-frequency

measurement events A1 and A2. This parameter is

used to prevent frequent triggering of event

evaluation caused by radio signal fluctuation. In

this way, the probability of ping-pong handovers or

handover decision errors is reduced. A larger value

of this parameter results in a lower probability.

GUL

value: 2

Actual

value:

1dB

InterFreqHoA

1A2TimeToT

rig

Interfreq

A1A2 time

to trigger

Indicates the time-to-trigger for inter-frequency


When detecting that the signal quality in the

serving cell meets the triggering condition, the UE

does not send a measurement report to the

eNodeB immediately. Instead, the UE sends a

report only when the signal quality continuously

meets the entering condition during the time-to-

trigger. This parameter helps decrease the number

of occasionally triggered event reports, the average

number of handovers, and the number of wrong

handovers. In summary, it helps prevent

unnecessary handovers.

640ms

InterFreqHoA

1A2TrigQuan

InterFreq

A1A2

Measurem

ent trigger

quantity

The quantity can be RSRP, RSRQ, or both. The

measured RSRP values are stable, varying little

with the load, and therefore there is little signal

fluctuation. The measured RSRQ values vary with

the load and are likely to reflect the signal quality of

the cell in real time.

RSRP

CellIndividual

Offset

Cell

individual

offset

Indicates the cell-specific offset for the intra-

frequency neighboring cell. It affects the probability

of triggering intra-frequency measurement reports.

A larger value of this parameter indicates a higher

probability.

dB0

InterFreqHoA

1ThdRsrp

Interfreq

A1 RSRP

threshold

Indicates the RSRP threshold for inter-frequency

measurement event A1.

When the measured RSRP value exceeds this

threshold, a measurement report may be sent.

-105dBm

InterFreqHoA

2ThdRsrp

Interfreq

A2 RSRP

threshold

Indicates the RSRP threshold for inter-frequency


When the measured RSRP value is below the


-109dBm

Inter-frequency key parameter




ended

Value

InterFreqHoA

4Hyst

Interfreq

handover

hysteresis

Indicates the hysteresis for event A4. This

parameter is used to prevent frequent triggering of

event evaluation caused by radio signal fluctuation.

In this way, the probability of ping-pong handovers

or handover decision errors is reduced. A larger

value of this parameter results in a lower

probability.

2dB

InterFreqHoA

4ThdRsrp

Coverage

Based

Interfreq

RSRP

threshold

Indicates the RSRP threshold for event A4 related

to coverage-based or distance-based inter-

frequency handover. When the measured RSRP

value exceeds this threshold, an inter-frequency

measurement report may be sent.

-105dBm

InterFreqHoA

4RprtQuan

Measurem

ent A4

report

quantity

The measured RSRP values are stable, varying

little with the load, and therefore there is little signal




After an inter-frequency handover event is

triggered, the reporting quantity is BOTH, that is,

both RSRP and RSRQ.

SAME_A

S_TRIG_

QUAN

InterFreqHoA

4TimeToTrig

Interfreq

HandOver

Time to

Trigger

Indicates the time-to-trigger for event A4 for the

inter-frequency handover. When detecting that the

signal quality in at least one neighboring cell meets

the entering condition, the UE does not send a

measurement report to the eNodeB immediately.

Instead, the UE sends a report only when the

signal quality continuously meets the entering

condition during the time-to-trigger.

This parameter helps decrease the number of

occasionally triggered event reports, the average

number of handovers, and the number of wrong

handovers. In summary, it helps prevent

unnecessary handovers.

640ms

InterFreqLoa

dBasedHoA4

ThdRsrp

Load

Based

Interfreq

RSRP

threshold


to load- based, frequency-priority-based, UL quality

based or service based inter-frequency handover.


threshold, an inter-frequency measurement report

may be sent.

-103dBm





ended

Value

FreqPriInt

erFreqHo

A1ThdRsr

p

Freq Priority

Based Interfreq

A1 RSRP

threshold

Indicates the RSRP threshold for frequency-

priority-based inter-frequency measurement event

A1. When the measured RSRP value exceeds this

threshold, an event A1 report may be sent.

-85dBm

IFreqPriInt

erFreqHo

A2ThdRsr

p

Freq Priority

Based Interfreq

A2 RSRP

threshold

Indicates the RSRP threshold for frequency-


A2.When the measured RSRP value exceeds this


-87dBm

FreqPriInt

erFreqHo

A1TrigQu

an

A1 Measurement

trigger quantity

of Freq Priority

Indicates the triggering quantity for frequency-


A1. The quantity can be either RSRP or RSRQ.

The measured RSRP values are stable, varying

little with the load, and therefore there is little signal




RSRP

InterFreq

HoA4Trig

Quan

FreqPrior

loadBased A4

Measurement

trigger quantity

Indicates the triggering quantity for frequency

priority, load based, UL quality based, service

based or distance based inter-frequency handover

event A4.

RSRP

InterFreqL

oadBased

HoA4Thd

Rsrp

Load Based

Interfreq

RSRP

threshold


to load- based, frequency-priority-based, UL quality

based or service based inter-frequency handover.


threshold, an inter-frequency measurement report

may be sent.

-103dBm

InterFreq

HoA3Offs

et

Interfreq A3

offset

Indicates the offset for event A3 associated with

inter-frequency handover. This parameter

determines the border between the serving cell and

the neighboring cell. If the parameter is set to a

large value, an inter-frequency handover is

performed only when the signal quality of the

neighboring cell is significantly better than that of

the serving cell and other triggering conditions are

met.

1dB





ended

Value

A3InterFre

qHoA1Thd

Rsrp

A3 based

interfreq A1

RSRP

threshold

Indicates the RSRP threshold for event A1

associated with event-A3-triggered inter-frequency

handover.



-95dBm

A3InterFre

qHoA2Thd

Rsrp

A3 based

Interfreq A2

RSRP

threshold

Indicates the RSRP threshold for event A2

associated with event-A3-triggered inter-frequency

handover. When the measured RSRP value is

below the threshold, a measurement report may be

sent.

-99dBm

InterFreq

HoEventT

ype

Inter-Freq HO

trigger Event

Type

Indicates the event to trigger inter-frequency

handovers. If the neighboring E-UTRAN frequency

and the serving frequency are in the same

frequency band, either event A3 or event A4 can

be used to trigger an inter-frequency handover.

Note that the handover performance when event

A3 is used is better than that when event A2 is

used. If the neighboring E-UTRAN frequency and

the serving frequency are in different frequency

bands, only event A4 can be used to trigger an

inter-frequency handover

EventA4

Inter-RAT key parameter




ended

Value

InterRatH

oA1A2Hys

t

InterRAT A1A2

hysteresis

Indicates the hysteresis for inter-RAT

measurement events A1 and A2. This parameter is

used to prevent frequent triggering of event

evaluation caused by radio signal fluctuation. In

this way, the probability of ping-pong handovers or

handover decision errors is reduced. A larger value

of this parameter results in a lower probability.

2dB

InterRatH

oA1A2Tim

eToTrig

InterRAT A1A2

time to trigger

Indicates the time-to-trigger for inter-RAT


When detecting that the signal quality in the

serving cell meets the entering condition, the UE

does not send a measurement report to the

eNodeB immediately. Instead, the UE sends a

report only when the signal quality continuously

meets the entering condition during the time-to-

trigger.

640ms

InterRatH

oA1A2Trig

Quan

InterRat A1A2

measurement

trigger quantity

Indicates the RSRP threshold for inter-RAT


When the measured RSRP value of the serving

cell exceeds this threshold, an event A1 report may

be sent.

RSRP

InterRatH

oA1ThdRs

rp

InterRAT A1

RSRP trigger

threshold

Indicates the RSRP threshold for inter-RAT


When the measured RSRP value of the serving

cell exceeds this threshold, an event A1 report may

be sent.

-115dBm

InterRatH

oUtranB1

MeasQua

n

Utran

measurement

trigger

quantity

Indicates the measurement quantity required for

the inter-RAT handover to UTRAN.

The RSCP values are relatively stable, and Ec/No

fluctuates much with the network load.

UTRAN_

RSCP

InterRatH

oUtranB1

ThdRscp

CoverageBas

ed UTRAN

RSCP trigger

threshold

Indicates the RSCP threshold for event B1 related

to coverage-based inter-RAT handover to UTRAN.

This parameter specifies the requirement for RSCP

of the target UTRAN cell.

When the measurement value exceeds this


-103dBm

Inter-RAT key parameter




ended

Value

InterRat

HoUtran

B1ThdEc

n0

CoverageBased

UTRAN ECN0

trigger threshold

This parameter specifies the requirement for Ec/No

of the target UTRAN cell. For a cell with large

signal fading variance, set this parameter to a large

value to prevent unnecessary handovers. For a cell

with small signal fading variance, set this

parameter to a small value to ensure timely

handovers. A larger value of this parameter results

in a lower probability of handover to the UTRAN

cell, and a smaller value leads to a higher

probability.

-20dB

InterRat

HoUtran

B1TimeT

oTrig

UTRAN time to

trigger

Indicates the time-to-trigger for event B1 related to

inter-RAT handover to UTRAN. When detecting

that the signal quality in at least one neighboring

cell meets the entering condition, the UE does not

send a measurement report to the eNodeB

immediately. Instead, the UE sends a report only

when the signal quality continuously meets the

entering condition during the time-to-trigger

640ms

LdSvBas

edHoUtr

anB1Thd

Rscp

Load Service

Based UTRAN

EventB1 RSCP

trigger threshold

Indicates the RSCP threshold for event B1 related

to load- or service-based inter-RAT handover to

UTRAN.

-101dBm

LdSvBas

edHoUtr

anB1Thd

Ecn0

Load Service

Based

UTRANB1

ECN0 threshold

Indicates the Ec/No threshold for event B1 related

to load- or service-based inter-RAT handover to

UTRAN.

-18dB

InterRat

HoGeran

B1Thd

Coverage

Based GERAN

trigger

threshold

Indicates the RSSI threshold for event B1 related

to coverage-based inter-RAT handover to GERAN.

A UE sends a measurement report related to event

B1 to the eNodeB when the RSSI in at least one

GERAN cell exceeds this threshold and other

triggering conditions are met.

-100dBm

LdSvBas

edHoGer

anB1Thd

Load Service

Based Geran

EventB1 trigger

threshold

Indicates the RSSI threshold for event B1 related

to load- based or service-based inter-RAT

handover to GERAN.

When the measured RSSI value exceeds this


-98dBm

Documents

Oeo106060 Lte Eran3.0 Handover Feature Issue1.00