ZTE LTE FDD Handover Feature Description
Short Description
Descripción: ZTE LTE FDD Handover Feature Description...
Description
LTE FDD
Handover Feature Description
Handover Feature Description
Product Type Technical Description
Version
Date
Author
Approved By
Remarks
V1.0
2011-02-15
Cheng Hao
Not open to the Third Party
V2.0
2011-08-15
Cheng Hao
Not open to the Third Party
V2.1
2011-09-01
Cheng Hao
V2.2
2011-9-21
Cheng Hao
Add the parameter“Redirect for Coverage” description Add the parameter “Redirection Measurement Configuration Index” description
© 2011 ZTE Corporation. All rights reserved. ZTE CONFIDENTIAL: This document contains proprietary information of ZTE and is not to be ZTE Confidential Proprietary © 2011 ZTE Corporation. All rights reserved. I disclosed or used without the prior written permission of ZTE. Due to update and improvement of ZTE products and technologies, information in this document is subjected to change without notice.
Handover Feature Description
TABLE OF CONTENTS 1
Introduction ................................................................................................................ 1
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8
Function Description ................................................................................................. 1 Intra-Freq Handover Strategy ...................................................................................... 1 Inter-Freq Handover Strategy ...................................................................................... 2 Measurement Gap Configuration Strategy .................................................................. 2 Redirection Strategy .................................................................................................... 2 Intra-RAT Handover Based on Load Balancing .......................................................... 3 Handover to UTRAN .................................................................................................... 3 Handover to GERAN ................................................................................................... 3 CS Fallback to GERAN/UTRAN .................................................................................. 4
3 3.1 3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.6 3.2 3.2.1 3.3 3.3.1 3.3.2 3.4 3.4.1 3.4.2 3.5 3.5.1 3.5.2 3.6 3.6.1 3.6.2 3.7 3.7.1
Technical Description ................................................................................................ 4 Measurement in RRC_Connected ............................................................................... 4 Intra-RAT Event-triggered Measurement Reporting .................................................... 4 Inter-RAT Event-triggered Measurement Reporting .................................................. 10 Intra-Freq Measurement ............................................................................................ 12 Inter-Freq Measurement ............................................................................................ 14 Inter-RAT Measurement ............................................................................................ 14 Measurement Gap Configuration Strategy ................................................................ 15 Intra-Freq Handover Strategy .................................................................................... 18 Intra-Freq Event Handling.......................................................................................... 18 Inter-Freq Handover Strategy .................................................................................... 19 Inter-Freq Handover Decision.................................................................................... 19 Inter-Freq Event Handling.......................................................................................... 19 Handover Based on Load Balancing ......................................................................... 20 Load Balancing Triggered.......................................................................................... 20 Handover Handling .................................................................................................... 20 Inter-RAT Handover Strategy .................................................................................... 20 Handover to GERAN ................................................................................................. 20 Handover to UTRAN .................................................................................................. 21 Redirection ................................................................................................................. 22 Redirection Judgment and Related Measurement .................................................... 23 Redirection Target System/Frequency Band Selection ............................................. 24 CS Fallback to GERAN/UTRAN ................................................................................ 24 CS Fallback Target Cell and Method Selection ......................................................... 24
4 4.1 4.1.1 4.1.2
Parameter and Configuration .................................................................................. 25 Related Parameters ................................................................................................... 25 Parameter List ........................................................................................................... 25 Parameter Configuration............................................................................................ 26
5
Glossary .................................................................................................................... 36
FIGURES Figure 1 Figure 2
Measurement Gap Configuration with Propagation Delay .......................................... 16 Measurement Gap Configuration without Propagation Delay ..................................... 17
II
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Handover Feature Description
1
Introduction This document describes the connection mode management functions within the eNodeB in LTE network. Abbreviations used in this document are explained in Glossary.
2
Function Description In LTE system, RRC-connection mobility management is realized by cell handover strategy for the reason of UE mobility; the load balancing can adjust the traffic distribution among the cells to reduce the traffic of high-load cell. During the handover, the service continuity should be guaranteed and the service Qos should be satisfied. Based on the different characteristics of cell frequency and access technologies before and after the handover, the cell handover strategy can be divided into intra-frequency handover, inter-frequency handover and inter-RAT handover. This document mainly introduces the ZTE eNodeB mobility management in RRC connection state by adopting cell handover strategy. Based on the different characteristics of cell frequency before and after the handover, the cell handover strategy can be divided into: 1
Intra-Freq handover strategy
2
Inter-Freq handover strategy
3
Measurement interval configuration strategy for Inter-Freq handover
4
Redirection strategy
5
Intra-RAT Handover based on Load Balancing
6
Handover to UTRAN
7
Handover to GERAN
8
CS fallback to GERAN/UTRAN
Handover strategy includes measurement control and event report. Handover include measurement, handover decision and handover execution. Measurement is the prerequisite for handover, and handover decision is the core and the handover execution is the procedure realizing the handover.
2.1
Intra-Freq Handover Strategy When the UE in connected state moves between different cells, it is necessary to introduce handover to guarantee the service continuity.
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Handover Feature Description
Intra-Freq handover means the UE in connected state performs handover between the neighbor cells with the same frequency in E-UTRAN. Intra-Freq handover algorithm is based on the measurement including Intra-Freq measurement control and Intra-Freq measurement report handling. Intra-Freq measurement control involves the establishment, modification, and release of Intra-Freq measurement. For related details, please refer to Section 3.1.1. The Intra-Freq measurement report handling means that when eNB receives the Intra-Freq measurement report from UE, the eNB performs IntraFreq handover judgment according to the specific measurement report and other related information. byReportQuan controls the Intra-Freq measurement quantity that triggers the report. For related details, please refer to Section 3.2.
2.2
Inter-Freq Handover Strategy When operators deploy the network, the Inter-Freq neighboring cells shall be configured besides configuring Intra-Freq neighboring cells. Therefore, there are the Intra-Freq handover and Inter-Freq handover. The Inter-Freq handover means the UE in connected state performs handover from one E-UTRAN frequency cell to another frequency cell. The Inter-Freq handover algorithm is based on measurement including Inter-Freq measurement control and Inter-Freq measurement handling. For related details on InterFreq measurement control, please refer to Section 3.1.4. The Inter-Freq measurement control mainly involves the establishment, modification, and release of InterFreqmeasurement. The Inter-Freq measurement report handling means when eNB receives the Inter-Freq measurement report from UE, the eNB performs Inter-Freq handover judgment according to the specific measurement report and other related information. byReportQuan control the Inter-Freq measurement quantity that trigger the report; For details on Inter-Freq measurement report handling, please refer to Section 3.3.
2.3
Measurement Gap Configuration Strategy The terminal which needs the measurement gap to perform Inter-Freq/Inter-RAT measurement, the eNB shall activate measurement gap when taking Inter-Freq/InterRAT measurement. The measurement gap means some subframes are not used to transmit data during transmitting and receiving. Some factors, such as the time and conditions of activation and deactivation, measurement interval offset and coupling with DRX should be considered during configuration. For the details on measurement gap configuration, please refer to Section 3.1.6.
2.4
Redirection Strategy The system use redirectedCarrierInfo in the Message RRCConnectionRelease to indicate UE to camp on the specified system/frequency when disconnected. LTE supports Intra-Rat redirection and Inter-Rat redirection. This algorithm in this documents mainly describes redirection from LTE to 3GPP 2G/3G, CDMA2000-HRPD and CDMA2000-1xRTT. The UE wireless ability is optional for handover to some target system/neighbor cell. As long as UE supports the target system/frequency, it can support redirection to target system/frequency. Therefore, in this mobility management algorithm based on coverage, if the Intra-Freq measurement report from CEU (Cell Edge UE) shows that the signal quality of the serving cell is deteriorating, and if the UE wireless ability or network don’t 2
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Handover Feature Description
support handover to target system/frequency, the UE will handover to specified target system/frequency by redirection. Therefore, the UE can camp on the specified system/frequency immediately after the RRC connection is released, and the business interrupt time is shortened. byRd4Coverage is the switch of this feature and abyRdRATPriority sets the priorities for candidate target systems. For more details, please refer to Section 3.6. The redirection applications in other scenarios like camping load balance, are not supported in this algorithm version.
2.5
Intra-RAT Handover Based on Load Balancing When the load balancing is switched on, and the cell load balancing parameter is higher than the threshold, the load balancing among the same coverage cells or overlapped inter-frequency cells shall be triggered, that is, the UEs with low priority shall be handover to the neighboring cells with low load so that the traffic of high load cell can be handover to the neighboring cell with low load to achieve the load balancing without user release. Based on the selected target UEs and target cell lists, the UE shall be handover to the target cell but the target cell number is limited. It can not be larger than the OMC parameter ucLBMaxHOCell.
2.6
Handover to UTRAN LTE is all IP system, and all services are based on IP bearer. When UE handovers to UTRAN PS domain, the handover is called PS handover to UTRAN. And if UE handovers to UTRAN CS domain, for example, LTE VoIP is handover to UTRAN CS, this handover is called SRVCC handover to UTRAN. PS HO needs target UTRAN cell support and OMC configuration field byUTRANNBRcellPSHOFlg. SRVCC handover, depends on whether the UE supports the voice service and whether the target cell supports VoIP, and whether UE and MME support SRVCC. For more details, please refer to Section 3.5.2.
2.7
Handover to GERAN GERAN is different from UTRAN. Its special attribute DTM (Dual Transfer Mode) indicates whether GERAN supports PS and CS simultaneously. Because some GERAN supports CS only (OMC field byDtmsupport can configure the DTM capability of target GERAN neighboring cell), the LTE handover to GERAN can be DTM HO ( PS and CS handover at the same time) or CS HO only. LTE voice handover to GERAN PS domain is PS HO and the prerequisite is the GERAN cell supports VoIP ( OMC field ucGERANNBRcellVoIPFlg is configured). The data PS service, PS HO is performed to GERAN (OMC field byDtmsupport indirectly reflects the PS HO capability of target GERAN); LTE voice service can be handover to GERAN CS domain, that is, SRVCC handover to GERAN. When the UE with voice and data services is handover to GERAN, the data service is handover to PS domain and the voice service is switched by SRVCC, that is, DTM HO. Handover to GERAN has another CCO process. During CCO process, the air interface command can carry the SIB information of the target cell to reduce the access latency. Currently, SRVCC is not supported. For more details, please refer to Section 3.5.1.
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Handover Feature Description
2.8
CS Fallback to GERAN/UTRAN At the initial stage of LTE network deployment, if the operator has not IMS for its core network, LTE system can not provide voice service. The voice service can be supported by CS Fallback to the same coverage cells or overlapped inter-RAT neighboring cells. That is, when initiating a voice service, the service is handover to the target GERAN/UTRAN cell and the voice service is provided by the CS domain resources of GERAN/UTRAN. More specifically, if eNodeB receives INITIAL CONTEXT SETUP REQUEST or UE CONTEXT MODIFICATION REQUEST with CS Fallback Indicator from MME at S1 interface, UE shall be triggered to switch to GERAN/UTRAN cell to perform voice service by means of PS HO, CCO or redirection. Before the handover, the target cell is selected based on measurement or blind measurement. The present version supports CS Fallback based on blind measurement, so the target cell can only be the same coverage cells or the overlapped GERAN/UTRAN cells.
3
Technical Description
3.1
Measurement in RRC_Connected When UE is in RRC_connected state, the measurement reporting criterion, on which the UE bases to send a measurement report, consists of periodical reporting and single event triggered. Periodical reporting means that the UE regularly reports the measured quality of DL cell reference signals to eNodeB. Event–triggered reporting means that the UE shall judge whether the measured quality of DL cell reference signal meets the reporting criterion. If yes, the UE shall report the event (including the information such as Event ID, target cell and so on).
3.1.1
Intra-RAT Event-triggered Measurement Reporting LTE defines altogether 5 intra-system measurements: A1~A5, of which A1 and A2 are applied to Intra-Freq measurement, and A3~A5 are applied to intra- Freq or Inter-Freq measurement. They are described in details below.
3.1.1.1
Event A1 Event A1 means serving cell quality becomes better than threshold. When receiving Event A1, eNB shall stop the Inter-Freq measurement the UE is conducting. If the measurement gap is activated, the measurement gap should be deactivated. The UE shall: Apply inequality A1-1, as the entering condition for this event Apply inequality A1-2, as the leaving condition for this event Inequality A1-1 (Entering condition)
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Ms − Hys > Thresh When the following leaving condition is fulfilled, UE shall not report A1 event any more to eNB: Inequality A1-2（Leaving condition）
Ms + Hys < Thresh The variables in the formula are defined as follows: Ms is the measurement result of the serving cell, not taking into account any cell individual offset. Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Hys is the hysteresis parameter for this event. Its corresponding OMC parameter is byHysterisis. Hys is expressed in dB； Thresh is the threshold parameter for this event, and it is expressed in the same unit as Ms. The above formulas show: An increasing Thresh will reduce the triggering probability of A1 event and vice versa. If Hys is increased, the probability of entering Event A1 will be decreased. Once the Event A1 entering condition is satisfied, even if the quality of the serving cell is very bad, it still meets the Event A1 entering condition because it is very difficult to meet the Event A1 leaving condition. If Hys is decreased otherwise, the probability of leaving Event A1 will be increased and once the Event A1 entering condition is satisfied, even if the quality of the serving cell deteriorates slightly, it will meet the Event A1 leaving condition because it is very easy to get triggered. Event A1 supports event-triggered periodical reporting. That is, when UE detects that the signal quality falls in the reporting range of Event A1, the UE shall begin to report Event A1 periodically (OMC parameter is byRptIntvl) until the reporting criteria is not fulfilled any longer or the allowed maximal number of reporting times has been reached (OMC parameter is byRptAmt ）. Event A1 in this algorithm is mainly used to close the Intra-Freq/ Inter-RAT measurement. Event A1 will be triggered when the eNB receives Event A2 from UE which is used for starting the Inter-Freq/ Inter-RAT measurement.
3.1.1.2
Event A2 Event A2 means the signal quality of the serving cell becomes worse than a predefined threshold. When receiving Event A2, eNB shall start UE Inter-Freq measurement or start UE inter-Rat measurement. If the measurement gap needs to be activated, eNB activates the measurement gap. The UE shall: Apply inequality A2-1, as the entering condition for this event Apply inequality A2-2, as the leaving condition for this event
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Inequality A2-1 (Entering condition)
Ms + Hys < Thresh Inequality A2-2（Leaving condition）
Ms − Hys > Thresh The variables in the formula are defined as follows: Ms is the measurement result of the serving cell, not taking into account any cell individual offset. Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Hys is the hysteresis parameter for this event. Its corresponding OMC parameter is byHysterisis. Hys is expressed in dB； Thresh is the threshold parameter for this event, and it is in the same unit as Ms.. The two formulas show: If Thresh is increased, the triggering probability of Event A2 will be increased And vice versa. If Hys is increased, the probability of Event A2 triggering will be decreased. Once Event A2 reporting range is satisfied, even if the measured quality of the serving cell becomes better, it will still meet the Event A2 reporting condition because it becomes more difficult to meet the leaving condition of Event A2 reporting. Otherwise, the probability of Event A2 triggering will be increased, and at the same time once the Event A2 reporting range is satisfied, even if the measurement quality of the serving cell improves slightly, it shall meet the Event A2 leaving condition because it is easier to leave Event A2 reporting. Event A2 supports event-triggered periodical reporting. That is, when UE detects that the signal quality falls in the reporting range of Event A2, the UE shall begin to report Event A2 periodically (OMC parameter is byRptIntvl) until the reporting criteria is not fulfilled any longer or the allowed maximal number of reporting times has been reached （OMC parameter is byRptAmt）. Event A2 in this algorithm is used for starting the Inter-Freq/Inter-RAT measurement and redirection judgment. eNB shall configure for each UE one of the two versions of Event A2 at certain moment. Once receiving Event A2, eNB starts corresponding procedures. For more details, please refer to Section 3.1.4 and 3.4.
3.1.1.3
Event A3 Event A3 means neighboring cell quality becomes a predefined offset better than serving cell. When receiving Event A3, eNB shall start the coverage-based Intra-Freq or Inter-Freq handover decision. The UE shall: Apply inequality A3-1, as the entering condition for this event Apply inequality A3-2, as the leaving condition for this event
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Inequality A3-1 (Entering condition)
Mn + Ofn + Ocn − Hys > Ms + Ofs + Ocs + Off Inequality A3-2（Leaving condition）
Mn + Ofn + Ocn + Hys < Ms + Ofs + Ocs + Off The variables in the formula are defined as follows: Mn is the measurement result of the neighboring cell, not taking into account any cell individual offset. Mn is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Ofn is the frequency specific offset of neighboring cell (equals Ofs for Intra-Freq measurements and is included in measObjectEUTRA corresponding to the Inter-Freq as offsetFreq for interfrequency measurements). Its corresponding OMC parameter is abyOffsetFreq,and it is expressed in dB; Ocn is the cell specific offset of neighboring cell. (included in measObjectEUTRA of the serving frequency as parameter cellIndividualOffset, Its corresponding OMC parameter is byCellIndivOffset). It is expressed in dB; Ms is the measurement result of the serving cell, not taking into account any cell individual offset. Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Ofs is the frequency specific offset of the serving cell (i.e offsetFreq within measObjectEUTRA corresponding to the serving frequency). It is expressed in dB; Ocs is the cell specific offset of the serving cell (included in measObjectEUTRA of the serving frequency as parameterbyCellIndivOffset, Its corresponding OMC parameter is byCellIndivOffset). It is expressed in dB; Hys is the hysteresis parameter for this event. Its corresponding OMC parameter is byHysteresis, and Hys is expressed in dB； Off is the offset parameter for this event, Its corresponding OMC parameter is byA3offset. It is expressed in dB； The configuration of Hys is similar to Hys in Event A1 and Event A2 in terms of its influence on Event triggering, and Off is similar to Thresh in Event A1 in terms of its influence on Event triggering. But Off is a relative threshold, rather than an absolute threshold, it serves to compare the difference between neighboring cell and serving cell qualities. Event A3 supports event-triggered periodical reporting. That is, when UE detects that the signal quality falls in the reporting range of Event A3, the UE shall begin to report Event A3 periodically (Its corresponding OMC parameter is byRptIntvl) until the reporting criteria is not fulfilled any longer or the allowed maximal number of reporting times has been reached (Its corresponding OMC parameter is byRptAmt).
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Handover Feature Description
3.1.1.4
Event A4 Event A4 means neighboring becomes better than a predefined threshold. When receiving Event A4, eNB may trigger handover driven by load balancing. The UE shall: Apply inequality A4-1, as the entering condition for this event Apply inequality A4-2, as the leaving condition for this event Inequality A4-1 (Entering condition)
Mn + Ofn + Ocn − Hys > Thresh Inequality A4-2（Leaving condition）
Mn + Ofn + Ocn + Hys < Thresh The variables in the formula are defined as follows: Mn is the measurement result of the neighboring cell, not taking into account any cell individual offset. Mn is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Ofn is the frequency specific offset of the neighboring cell (equals Ofs for Intra-Freq measurements and is included in measObjectEUTRA corresponding to the Inter-Freq as offsetFreq for interfrequency measurements). Its corresponding OMC parameter is,and it is expressed in dB； Ocn is the cell specific offset of neighboring cell. (Included in measObjectEUTRA of the neighboring frequency as parameter cellIndividualOffset). It is expressed in dB; Hys is the hysteresis parameter for this event. Its corresponding OMC parameter is byHysteresis, and Hys is expressed in dB； Thresh is the threshold parameter for this event, it is expressed in the same unit as Mn. The configuration of Hys is similar to Hys in Event A1 and Event A2 in terms of its influence on Event triggering, and the configuration of Thresh is similar to Thresh in Event A1 in terms of its influence on Event triggering. Event A4 supports event-triggered periodical reporting. That is, when UE detects that the signal quality falls in the reporting range of Event A4, the UE shall begin to report Event A4 periodically (Its corresponding OMC parameter is byRptIntvl) until the reporting criteria is not fulfilled any longer or the allowed maximal number of reporting times has been reached (Its corresponding OMC parameter is byRptAmt).
3.1.1.5
Event A5 Event A5 means serving cell becomes worse than threshold 1 and neighboring cell becomes better than threshold 2. When receiving Event A5, eNB may trigger coverage based Intra-Freq or Inter-Freq handover.
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The UE shall: Apply inequality A5-1 and equation A5-2, both have to be fulfilled, as the entering condition for this event Apply inequality A5-3 and equation A5-4, at least one of the two has to be fulfilled, as the leaving condition for this event Inequality A5-1 (Entering condition 1)
Ms + Hys < Thresh1 Inequality A5-2 (Entering condition 2）
Mn + Ofn + Ocn − Hys > Thresh 2 Inequality A5-3 (Leaving condition 1）
Ms − Hys > Thresh1 Inequality A5-4 (Leaving condition 2）
Mn + Ofn + Ocn + Hys < Thresh 2 The variables in the formula are defined as follows: Mn is the measurement result of the neighboring cell, not taking into account any cell individual offset. Mn is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Ofn is the frequency specific offset of the neighboring cell(equals Ofs for Intra-Freq measurements and is included in measObjectEUTRA corresponding to the Inter-Freq as offsetFreq for interfrequency measurements). Its corresponding OMC parameter is abyOffsetFreq, and it is expressed in dB； Ocn is the cell specific offset of neighboring cell. (included in measObjectEUTRA of the neighboring frequency as parameterbyCellIndivOffset). It is expressed in dB; Ms is the measurement result of the serving cell, not taking into account any cell individual offset. Mn is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Ofs is the frequency specific offset of the serving cell (i.e offsetFreq within measObjectEUTRA corresponding to the serving frequency). Its corresponding OMC parameter is,and is expressed in dB； Ocs is the cell specific offset of the serving cell (included in measObjectEUTRA of the serving frequency as parameter Cell Individual Offset. It is expressed in dB; Hys is the hysteresis parameter for this event. Its corresponding OMC parameter is IntraF Hysteresis ,and Hys is expressed in dB； Thresh1 is the threshold 1 in Event A5, and it is expressed in the same unit as Ms. Thresh2 is the threshold 2 in Event A5, and it is expressed in the same unit as Mn.
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Handover Feature Description
The configuration of Hys is similar to Hys in Event A1 and Event A2 in terms of its influence on Event triggering. If Thresh1is set too high and Thresh2 is set too low, the probability of Event A5 reporting will be increased. Otherwise, if Thresh1 is set too low and Thresh2 is set too high, the probability of Event A5 reporting will be decreased. Event A5 supports event-triggered periodical reporting. That is, when UE detects that the signal quality falls in the reporting range of Event A5, the UE shall begin to report Event A5 periodically (Its corresponding OMC parameter is byRptIntvl) until the reporting criteria is not fulfilled any longer or the allowed maximal number of reporting times has been reached (Its corresponding OMC parameter is byRptAmt).
3.1.1.6
Time-To-Trigger Mechanism To avoid the event misreport due to the radio quality fluctuation, the event shall be reported only when the signal quality of the cell to be evaluated meets the report range or threshold and the reporting condition must be met for a certain time period. The timeto-trigger mechanism is applied to intra- and Inter-Freq measurement (Its corresponding OMC parameter is byTrigTime). Take Event A1 as an example, UE can only report Event A1 when serving cell meets the reporting condition and the cell quality meets the reporting condition for the time period byTrigTime.
3.1.2
Inter-RAT Event-triggered Measurement Reporting
3.1.2.1
Event B1 Event B1 means inter RAT neighbor becomes better than threshold. When receiving Event B1, eNB may trigger coverage based inter RAT handover. The UE shall: Apply inequality B1-1, as the entering condition for this event Apply inequality B1-2, as the leaving condition for this event Inequality B1-1 (Entering condition) Mn + Ofn − Hys > Thresh
Inequality B1-2 (Leaving condition) Mn + Ofn + Hys < Thresh
The variables in the formula are defined as follows: Mn is the measurement result of the inter-RAT neighbour cell, not taking into account any offsets. For CDMA 2000 measurement result, pilotStrength is divided by -2. Ofn is the frequency specific offset of the frequency of the inter-RAT neighbour cell (i.e. offsetFreq as defined within the measObject corresponding to the frequency of the neighbour inter-RAT cell).
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Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigInterRAT for this event). Thresh is the threshold parameter for this event (i.e. b1-Threshold as defined within reportConfigInterRAT for this event). For CDMA2000, b1-Threshold is divided by -2. Its corresponding OMC parameter is byRscpSysNbrTrd or byEcNoSysNbrTrd for UTRAN, byRatSysNbrTrd for GERAN Mn is expressed in dBm or in dB, depending on the measurement quantity of the interRAT neighbour cell. Ofn, Hys are expressed in dB. Thresh is expressed in the same unit as Mn.
3.1.2.2
Event B2 Event B2 means serving becomes worse than threshold1 and inter RAT neighbor becomes better than threshold2. When receiving Event B2, eNB may trigger coverage based inter RAT handover. The UE shall: Apply inequality B2-1 and equation B2-2, both have to be fulfilled, as the entering condition for this event Apply inequality B2-3 and equation B2-4, at least one of the two has to be fulfilled, as the leaving condition for this event Inequality B2-1 (Entering condition 1) Ms + Hys < Thresh1
Inequality B2-2 (Entering condition 2) Mn + Ofn − Hys > Thresh 2
Inequality B2-3 (Leaving condition 1) Ms − Hys > Thresh1
Inequality B2-4 (Leaving condition 2) Mn + Ofn + Hys < Thresh 2
The variables in the formula are defined as follows: Ms is the measurement result of the serving cell, not taking into account any offsets. Mn is the measurement result of the inter-RAT neighbor cell, not taking into account any offsets. For CDMA2000 measurement result, pilotStrength is divided by -2.
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Handover Feature Description
Ofn is the frequency specific offset of the frequency of the inter-RAT neighbor cell (i.e. offsetFreq as defined within the measObject corresponding to the frequency of the interRAT neighbor cell). Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigInterRAT for this event). Thresh1 is the threshold parameter for this event (i.e. b2-Threshold1 as defined within reportConfigInterRAT for this event). Thresh2 is the threshold parameter for this event (i.e. b2-Threshold2 as defined within reportConfigInterRAT for this event). For CDMA2000, b2-Threshold2 is divided by -2. Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Mn is expressed in dBm or dB, depending on the measurement quantity of the inter-RAT neighbor cell. Ofn, Hys are expressed in dB. Thresh1 is expressed in the same unit as Ms. Thresh2 is expressed in the same unit as Mn.
3.1.3
Intra-Freq Measurement Intra-Freq measurement aims at Intra-Freq cells measurement (including serving cell), and the measurement report can be periodical report or event-triggered report. The measurement quantity can be RSRP or RSRQ.
3.1.3.1
Measurement Filtering To avoid measurement fluctuation while performing Intra-Freq measurement, the UE can perform Layer 3 filtering used for all events evaluation and related reporting of that measurement type. The filtering formula is shown below:
Fn = (1 − a ) ⋅ Fn −1 + a ⋅ M n Where: Fn-1
is the old filtered measurement result;
Fn is the updated filter measurement result, that is used for evaluation of reporting criteria or for measurement reporting； Mn
is the latest received measurement result from the physical layer；
a = 1/2(k/4) is the factor calculated according to filter coefficient K（Filter Coefficient for RSRP or Filter Coefficient for RSRQ）
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3.1.3.2
Measurement Establishment When RRC connection has been established, the information of Intra-Freq measurement will be sent to UE in the first RRCConnectionReconfiguration message containing information for UE context setup. When UE handovers from the other RAT to LTE, the information of Intra-Freq measurement will be sent in the RRCConnectionReconfiguration message. When RRC connection has been established and the first RRCConnectionRecongfiguration has been send, Event A2 for redirection judgement should be sent if these conditions below can be satisfied:
3.1.3.3
1
There exists Inter-Freq/Inter-RAT neighbouring cell UE can access to;
2
But UE radio capability or network does not support handover to the neighbouring cell;
3
Event A2 for starting Inter-Freq/ Inter-RAT has not been sent.
Measurement Modification In the condition that Intra-Freq measurement has been activated, the Intra-Freq measurement may be modified on the following occasions: 1
After Intra-Freq/ Inter-Freq handover;
2
If Event A2 measurement has not been activated and there are Inter-Freq neighboring cells, Event A2 measurement configuration can be sent to the UE;
3
When receiving Event A2 for starting Inter-Freq/ Inter-RAT measurement from UE and eNB has decided to start Inter-Freq/ Inter-RAT measurement:
4
−
Send Event A1 measurement;
−
Start Inter-Freq/ Inter-RAT measurement for handover judgement;
−
If there exists Inter-Freq/Inter-RAT neighbouring cell UE can access to, but UE radio capability or network can not support the handover to this neighbouring cell, UE modifies Event A2 threshold to Event A2 threshold for redirection judgement;
When receiving Event A1 for closing Inter-Freq/ Inter-RAT measurement from UE and eNB has decided to close Inter-Freq/ Inter-RAT measurement: −
If Event A2 for redirection has been sent and eNB modifies Event A2 threshold into Event A2 threshold for starting Inter-Freq/ Inter-RAT measurement;
−
Close Inter-Freq/ Inter-RAT measurement for handover judgement;
−
Close Event A1 for Inter-Freq/ Inter-RAT measurement;
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3.1.3.4
Measurement Release When the UE moves to RRC_IDLE state, the UE shall release all the Intra-Freq measurements automatically without any message notification.
3.1.4
Inter-Freq Measurement Inter-Freq measurement means that UE performs measurement on neighboring cells of non-serving frequency carrier. The measurement report can be periodical or eventtriggered. Among all of the events, Event A1 and A2 are measurements on serving frequency carrier. Therefore, measurement gap is not needed and will not introduce extra overhead to UE and the network. Event A1 and A2 can serve to activate and deactivate the measurement gap. Accordingly, when the service is established, if the serving cell has Inter-Freq neighboring cells, the eNodeB may send Event A1/A2 in addition to Intra-Freq measurement to the UE. The following measurement establishment, modification, release are all targeted at Inter-Freq measurement other than Event A1/A2.
3.1.4.1
Measurement Filtering To avoid measurement fluctuation while performing Inter-Freq measurement, the UE shall perform Layer 3 filtering used for all event evaluation and related reporting of that measurement type. The Layer 3 filtering related factor is Filter Coefficient for RSRP or Filter Coefficient for RSRQ. The application principle is similar to the formula used for “Intra-Freq measurement filtering”.
3.1.4.2
Measurement Establishment Inter-Freq measurement is only established after Event A2 reporting.
3.1.4.3
Measurement Modification Inter-Freq measurement is modified after intra-or Inter-Freq handover.
3.1.4.4
Measurement Release The eNB shall deactivate the Inter-Freq measurement after Event A1 reporting or when UE moves to RRC_IDLE state. For the latter case, the Inter-Freq measurement can be released automatically without any notification to the UE.
3.1.5
Inter-RAT Measurement Inter-RAT measurement refers to that UE performs measurement on the adjacent cell of non serving system. For all the measurement events, Event A1 and Event A2 are for serving carrier frequency measurements, and during the measurement it is not necessary to activate measurement gap and it shall not bring additional overhead to the UE and the system. According to Event A1 and Event A2 definitions, Inter-RAT measurement can be used to activate and deactivate the measurement gap. Therefore,
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at service establishment, if there exist inter-RAT adjacent cells, eNodeB shall send Event A1/A2 to the UE. The later measurement establishment, modification and release all aim at Inter-RAT measurement Events except Event A1/A2. Inter-RAT measurement report events are mainly Event B1 and Event B2. For detailed description, please see the relevant Section 3.1.2.2.
3.1.5.1
Measurement Filtering To avoid measurement fluctuation while performing inter-RAT measurement, the UE can perform Layer 3 filtering on measurement result, and then perform event judgment and report according to the filtered value. GERAN Layer 3 filter factor is byFilterCoeffGera,
and UTRAN Layer 3 factor is byFilterCoeffUtra . For the principle, please refer to Intra-Freq measurement Filter Formula.
3.1.5.2
Measurement Establishment Inter-RAT measurement is only established after Event A2 reporting.
3.1.5.3
Measurement Modification Inter-RAT measurement is modified after Inter-RAT handover.
3.1.5.4
Measurement Release The eNB shall deactivate the Inter-RAT measurement after Event A1 reporting or when UE moves to RRC_IDLE state. For the latter case, the Inter-RAT measurement can be released automatically without any notification to the UE.
3.1.6
Measurement Gap Configuration Strategy The measurement gap may be activated according to UE’s radio capability when performing Inter-Freq or inter-RAT measurement. The gap assisted measurement means that part of subframes can not be used for data transmission but are specifically applied to monitor target frequency. The UE is configured with measurement gap related parameters if the UE’s radio capability related RRC message shows that the measurement can only be supported with measurement gap. Otherwise, the measurement gap are not needed. The current protocol version configures 6ms measurement gap for both Inter-Freq and inter-RAT measurement.
3.1.6.1
Measurement Gap Repetition Period (MGRP) The current protocol defines two MGRPs: 40ms and 80ms. Both are applicable for the Inter-Freq and inter-RAT measurements.
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3.1.6.2
Subframes for Measurement Gap The measurement gap is the time period used for Inter-Freq and inter-RAT meansurment performed by UEs in RRC_CONNECTED state. During this time period, both the UL and DL data transmission are interrupted. The measurement gap is based on the time in DL subframes, so the number of interrupted UL subframes is dependent on the TA value sent by eNB and received by UE. As illustrated in figure 1, TA value is not zero under the conditon that FDD has propagation delay and ＃2 to ＃8 UL subframes are interrupted. As illustrated in figure 2, the TA value is zero when FDD ‘s propagation delay is zero. The red subframes do not overlap with the DL measurement gaps, so they are not interrupted. When not condsidering TA value, ＃8 subframe can always be interrupted. For FDD, the DL measurememt gaps fix to 6 subframes and 7 subframes for the UL measurement gaps.
Figure 1
Measurement Gap Configuration with Propagation Delay subframe
Transmission at eNB
DL #1
DL #0
DL #0
DL #9
DL #8
DL #7
DL #6
DL #5
DL #4
DL #3
DL #2
DL measurement gap Propagation delay Reception at UE
DL #0
DL #1 DL #2
DL #3
DL #4
DL #6
DL #5
DL #7
DL #8
DL #9
DL #0
DL measurement gap DL/UL offset by TA Transmission at UE
UL #0
UL #1
UL #2
UL #3
UL #4
UL #5
UL #6
UL #7
UL #8
UL #9
UL #0
UL #1
UL measurement gap
Propagation delay Reception at eNB
UL #0
UL #1
UL #2
UL #3
UL #4
UL #5
UL #6
UL #7
UL #8
UL #9
UL #0
UL #1
UL measurement gap
16
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Figure 2
Measurement Gap Configuration without Propagation Delay
subframe Transmission at eNB
DL #0
DL #1
DL #2
DL #3
DL #4
DL #5
DL #6
DL #7
DL #8
DL #9
DL #0
DL #6
DL #7
DL #8
DL #9
DL #0
UL #6
UL #7
UL #8
UL #9
UL #0
UL #1
UL #9
UL #0
UL #1
DL measurement gap
Reception at UE
DL #0
DL #1 DL #2
DL #3
DL #4
DL #5
DL measurement gap
Transmission at UE
UL #0
UL #1
UL #2
UL #3
UL #4
UL #5
UL measurement gap
Reception at eNB
UL #0
UL #1
UL #2
UL #3
UL #4
UL #5
?
UL #6
UL #7
UL #8
UL measurement gap
3.1.6.3
3.1.6.4
3.1.6.5
?
Measurement Gap Activation Occasions 1
Inter-Freq measurement or inter-RAT measurement has been established;
2
UE radio capability information indicates that the Inter-Freq measurement or interRAT measurement needs measurement gap;
3
The measurement gap needs to be activated as long as the measurement of the neighboring cell is gap-assisted.
Measurement Gap Deactivation Occasions 1
Intra-Freq measurement and inter-RAT measurement are both turned off (Event A1 triggering or measurement gap activation conditions are not fulfilled any longer)
2
After Intra-Freq/ Inter-Freq/ inter-RAT handover (UE shall automatically deactivate measurement gap without notification to UE)
3
UE moves to RRC_IDLE state (UE shall automatically deactivate measurement gap without notification to UE)
Gap offset Configuration without DRX Gapoffset configuration aims to activate the gaps as soon as possible. This allows UE to start measurement in the nearest possible MGRP, which enables UE to obtain as many measurement results as possible before the handover decision.
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3.1.6.6
Gap offset Configuration with DRX For the UE configured with DRX, the measurement gap is not needed when the socalled Opportunity-for-DRX is available for Inter-Freq or inter-RAT measurement, during which UE is sleeping. Due to the uncertanty of this time period because of the variable DRX cycles, short DRX cycles and retransmissions, the nubmer of availble subframes for measurement can be less than 6. Taking the worst cases into consideration, the measurement gap is configured with all kinds of DRX cycles to make sure the normal performance of measurement. According to the specifications, there is information element to indicate whether measurement gap is needed in the UE radio capability section. Measurement gap shall not be configured unless the UE radio capability shows that UE can perform the corresponding Inter-Freq or inter-RAT measurement without gap. Otherwise, it is necessary to configure measurement gap, even for the case where Opportunity-for-DRX is available. If the DRX is configured, the gapoffset configuration is to avoid the conflict between the measurement gap period and the On-Duration period in DRX. Meanwhile, 7 subframes are reserved as default for measurement gap.
3.2
Intra-Freq Handover Strategy Intra-Freq handover indicates handover of UE between E-UTRAN cells with same frequency. The Intra-Freq handover can be triggered based on RSRP or RSRQ, which can be controlled through parameter byTrigQuan
3.2.1
Intra-Freq Event Handling Event A3/A5 handling:
Judge the first cell in the measurement report cell list is the intra-eNodeB cell or Inter-eNodeB cell. 1. If the first cell in the measurement report cell list is the intra-eNodeB cell, the procedure is as follows: Initiate handover request and attemp to access. If all the services of the UE are accepted, move the Step 2. Otherwise, jump to Step 3. 2. Execute Intra-RAT handover. Handover to the target cell of successful access. Jump to Step 5 after the handover complete. 3. If some intra-eNodeB byHoPartCacSwicth for access handover are switched on, judge whether the UE services are accessed successfully or not. If one service is accepted, jump to Step 4. Otherwise, delete the cell of best quality in the target cell list and move the next step (some byHoPartCacSwicth are switched off or all services access failure). 4. Judge Whether there is a cell secondary to the best cell in the target handover cell list. If Yes, jump to the step that judges the cell is intra-eNodeB cell or Inter-eNodeB cell. If No, move the next step. 5. The procedure ends.
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If the first cell in the measurement report cell list is the inter-eNodeB cell, the procedure is as follows: 1. Initiate handover preparation to the eNodeB, and move to the next step if handover preparation is success. Jump to Step 3 if receiving HANDOVER PREPARATION FAILURE. 2. Execute Intra-RAT handover. Handover to the target cell and move to the next step after the handover complete. 3. The procedure ends.
3.3
Inter-Freq Handover Strategy The Inter-Freq handover denotes that UE switches from one frequency of E-UTRAN network to another frequency. The premise of Inter-Freq handover based on measurement is quality measurement of UE to non-serving carrier frequency and the measurement quantity can be either RSRP or RSRQ. This is controlled by OMC parameter byTrigQuan. The Inter-Freq measurement performed by UE in RRC_CONNECTED state in E-UTRAN may need measurement gap according to UE capability information. The activation of measurement gap has impact not only on system resource consumption (like DL power, UL interference, etc.) but also on UE itself (such as UE Tx-power, UE power consumption, etc.). Hence, the Inter-Freq measurement can be activated only when the signal quality of the serving carrier frequency becomes worse. When the eNodeB receives the Inter-Freq measurement report from the UE, it can make Inter-Freq handover decision and then handover the UE to the target cell whose carrier frequency is the same as the measurement report indicated.
3.3.1
Inter-Freq Handover Decision The Inter-Freq measurement used for Inter-Freq handover decision is controlled through A1 and A2 events reporting. Inter-Freq handover decision is triggered by A3/A5 event. The event ID and threshold of A3/A5 event used for Inter-Freq handover decision can be different from those of A3/A5 event used for Intra-Freq handover decision.
3.3.2
Inter-Freq Event Handling The Inter-Freq event has the same event ID as Intra-Freq event but different measurement objects ID and measurement ID. 1
When receiving Event A1 for deactivating inter-frequency measurement, eNodeB shall deactivate all the measurement events for inter-frequency handover judgment and judge whether inter-frequency measurement gap is configured. Deactivate the measurement gap if it exists.
2
When receiving Event A2 for activating inter-frequency measurement, eNodeB activates all related inter-frequency measurements and judges whether the measurement gap is needed. If yes, the measurement gap shall be activated.
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3
When receiving Event A3/A5 for inter-frequency handover judgment, eNodeB performs the procedures similar to the Intra-frequency handover Event handling described in Section 3.2.1/
3.4
Handover Based on Load Balancing
3.4.1
Load Balancing Triggered When the load balancing is switched on, and the cell load balancing parameter is higher than the threshold, the load balancing among the same coverage cells or overlapped inter-frequency cells shall be triggered, that is, the UEs with low priority shall be handover to the neighboring cells with low load so that the traffic of high load cell can be handover to the neighboring cell with low load to achieve the load balancing without user release. For the detailed judgment and UE selection flow, please refer to ZTE LTE Load Management Feature Description V2.1 CHS.doc.
3.4.2
Handover Handling Load balancing result indicates the UEs to be handovered and target handover cell list. By the OMC field ucLBMaxHOCell, the maximum cell number which UE attempts to access can be configured. eNodeB judges whether the cell list number is larger than the ucLBMaxHOCell. If yes, the first ucLBMaxHOCell cells are regarded as the target cells. Otherwise, the target handover cell list remains unchanged. The UE attempts to handover to all the cells in the cell list until the handover is successful and UE receives Handover Command. If all the attempts fail, the load balancing is regarded as failure and wait for the next load balancing.
3.5
Inter-RAT Handover Strategy The Inter-RAT handover in this document indicates that UE switches from one cell of EUTRAN network to another wireless network, such as UTRAN, GERAN (the UE switch from other wireless networks to EUTRAN network depends on the strategy of other network instead of ETRAN). Inter-RAT handover can be based on Inter-RAT measurement, or be the blind handover based on the same coverage or overlapping.
3.5.1
Handover to GERAN The handover from LTE to GERAN can be divided into PS HO, SRVCC, and CCO. When adopting CCO procedure, eNB needs to configure OMC parameter bySwitchNacc indicating whether the target GERAN cell supports NACC or not. If the target GERAN cell supports NACC, the eNB can obtain the system information of the target GERAN cell via RIM procedure, shortening delay from CCO to target GERAN cell.
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3.5.1.1
Handover Events with GERAN The measurement switch for E-UTRAN/GERAN handover is controlled by Events A1/A2 reporting, and the handovers are triggered by Event B1/B2. The measurement quantity for GERAN is RSSI. The event trigger threshold is OMC parameter byRatSysNbrTrd.
3.5.1.2
Handover Event processing with GERAN After eNB has received measurement report Event B1/B2 from UE for LTE/GERAN handover judgement, eNodeB shall decides the handover methods. The following factors are considered: Whether UE has services of QCI=1; Whether target GERAN cell supports VoIP ( configured by OMC field ucGERANNBRcellVoIPFlg); whether target GERAN cell supports PS HO (configured by OMC field byDtmsupport); whether UE supports CCO or not. eNodeB initiates PS HO when: 1. UE has no services of QCI=1 and the target GERAN cell supports PS HO; 2. UE has services of QCI=1 and the target GERAN cell supports VoIP. eNodeB initiates SRVCC when: UE has services of QCI=1 and the target GERAN cell does not support VoIP. UE and MME support SRVCC. eNodeB initiates CCO when: 1. UE has no services of QCI=1 and the target GERAN cell doesnot support PS HO. UE supports CCO. 2. UE has services of QCI=1 and the target GERAN cell does not support VoIP. UE or MME does not support SRVCC and UE supports CCO. 3. Handover preparation failure. UE supports CCO. Considering the above factors, ZTE eNodeB will initiates different handover methods to UE and tries to minimize handover latency and reduce the handover influence on the services.
3.5.2
Handover to UTRAN LTE handover to UTRAN consists of PS HO or SRVCC. SRVCC is triggered when UE has voice service of QCI=1 and the Utran cell does not support VoIP.
3.5.2.1
Handover Event with UTRAN The measurement switch for UTRAN handover is controlled by Event A1/A2 reporting. Handover judgement is triggered by Event B1/B2. UTRAN measurement quantity is RSCP or Ec/No, corresponding to OMC parameters byRscpSysNbrTrd and
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byEcNoSysNbrTrd respectively for Event threshold. Event-triggered selection is decided by parameter byUtranMeasQuan.
3.5.2.2
Handover Event processing with UTRAN After eNodeB has received measurement report Event B1/B2 from UE for LTE/UTRAN handover judgment, eNodeB shall decides the handover methods. The following factors are considered:
Whether UE has services of QCI=1; Whether target UTRAN cell supports VoIP ( configured by OMC field ucUTRANNBRcellVoIPFlg); whether target UTRAN cell supports PS HO (configured by OMC field ucUTRANNBRcellPSHOFlg). eNodeB initiates PS HO when: 1.
UE has no services of QCI=1 and the target UTRAN cell supports PS HO;
2.
UE has services of QCI=1 and the target UTRAN cell supports VoIP.
eNodeB initiates SRVCC when: UE has services of QCI=1 and the target UTRAN cell does not support VoIP. UE and MME support SRVCC. Considering the above factors, ZTE eNodeB will initiates different handover methods to UE and tries to minimize handover latency and reduce the handover influence on the services. .
3.6
Redirection For mobility management application scenarios which are based on coverage, PS HO or CCO is preferred if supported by UE and network because PH HO and CCO have better performance in time delay than redirection. If PS HO and CCO are not supported by UE radio capacity or the network, redirection is considered (configured by OMC parameter byRd4Coverage). The scenarios for this feature:
22
1
UE supports the frequency band of Inter-Freq or inter-RAT target neighboring cell and is allowed to access to this neighboring cell, and
2
UE radio capacity doesn’t support handover (and CCO) to Inter-Freq or(and) interRAT neighboring cell, or
3
Network side (including RAN or /and Core Network) temporarily can’t support InterFreq or (and) inter-RAT handover (and CCO).
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3.6.1
Redirection Judgment and Related Measurement According to the above description, when eNB decides to use redirection based on coverage, UE should be at the edge of serving cell. At this moment, if UE supports the measurement on system and frequency band of target neighboring cell in the connected state, UE must be able to handover to that neighboring cell according to protocols. So if UE can’t perform handover, UE can’t perform Inter-Freq/inter-RAT measurement of that neighboring cell while connected, either. Accordingly, eNB can’t configure UE for A3/A5 measurement event which is used for Inter-Freq handover judgment. eNB can’t configure UE for B1/B2 measurement event which is used for inter-RAT handover judgment, either. But eNB can configure UE for Intra-Freq measurement Event A2 and uses relevant report to decide whether UE is at the edge of serving cell（the OMC parameter is wOpenRedMeasCfg,which is Redirection Measurement Configuration Index）. In this algorithm, Event A2 is called the Event A2 for redirection judgment. The threshold setting for Event A2 in this version is different from that for Inter-Freq/Inter-RAT measurement in Inter-Freq/Inter-RAT system handover. Since Inter-Freq/Inter-RAT handover priority is higher than redirection, the Event A2threshold for redirection judgment is lower than Event A2 threshold for Inter-Freq/ Inter-RAT measurement. In another word, when the signal quality of serving cell begins to deteriorate, the InterFreq/Inter-RAT measurement will be activated first. Only when the signal quality of the serving cell is bad to a certain degree, Event A2 for redirection judgment shall be activated.
At any moment, eNB only configures one version of Event A2 for UE to perform intraFreq measurement. When UE radio capacity, network capacity, neighboring cell configuration only satisfy one of the two Event A2 versions, eNB configures UE for the corresponding Event A2 measurement. Event A2 report of UE shall trigger eNB to proceed with relevant actions. When UE radio capacity, network capacity, neighbor cell configuration can satisfy both two versions of Event A2, Event A2 Inter-Freq/Inter-RAT measurement will be first configured and issued. When eNB receives Event A2 reported by UE, measurement event for Inter-Freq/Inter-RAT handover judgment will be activated. Meantime, Event A2 threshold will be modified to the Event A2 threshold for redirection judgment and Event A1 will be issued to terminate Inter-Freq/Inter-RAT measurement. After these, if UE reports measurement events for Inter-Freq/Inter-RAT handover judgment, eNB shall be triggered to perform, handover judgment; if UE reports measurement event Event A2 for redirection judgment, eNB shall be triggered to perform redirection judgment; if UE reports Event A1 for terminating Inter-Freq/Inter-RAT measurement, eNB shall be triggered to terminate the Inter-Freq/Inter-RAT measurement of UE and adjusts Event A2 threshold to the Event A2 threshold for starting Inter-Freq/Inter-RAT measurement. The Event A2 threshold for redirection judgment can be based on the redirection activating parameter which is preset in the OMC database. The activating threshold can be based on RSRP, RSRQ of serving cell or on both at the same time. Specific choice is differentiated through the selecting of different redirection measurement configuration.
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3.6.2
Redirection Target System/Frequency Band Selection After eNB starts redirection judgment, the target system and frequency band for redirection need to be chosen for UE. After the target system and frequency band are determined by eNB, relevant information is sent to UE through RRC connection release signaling. The target system is decided first and then the target frequency band of this system will be decided. For flexible selection of the target system, the OMC database field abyRdRATPriority can indicate the priorities of different target systems. For serving cells with neighbor cells, the redirection system priority needs to be configured for the system and frequency band of each neighboring cell. When there are multiple candidates target systems, the target with higher priority will be chosen. After determining the target system according to redirection priority of each system, if the target system in neighboring cell has only one frequency band, then this band will be chosen as the target frequency band. If the target system in neighboring cell has more than one frequency band, the frequency band of the neighbor cell which has the same coverage with the serving cell or includes the serving cell will be first selected. This will guarantee the reliability of redirection. If there is no such neighboring cell, because there is no neighboring cell measurement available for target frequency band judgment, a random frequency band will chosen as the target frequency band for redirection.
3.7
CS Fallback to GERAN/UTRAN By CS Fallback technology, UE can initiate CS service (calling) when UE accesses or in camped in LTE network, and UE can receive CS service (called), and this technology can unable UE to handle PS service properly when UE accesses to LTE network. CS Fallback to GSM cells can be performed by PS HO, CCO or redirection method; CS Fallback to UTRAN cells can be performed by PS HO or redirection method.
3.7.1
CS Fallback Target Cell and Method Selection The present version supports blind CS Fallback only. It requires LTE and neighboring GERAN/UTRAN cells are the same coverage or overlapped. When GERAN and UTRAN neighboring cells exist at the same time, the CS fallback to GERAN or UTRAN can be decided by configuring OMC parameter ucTarRATforCSFB. If eNodeB receives INITIAL CONTEXT SETUP REQUEST or UE CONTEXT MODIFICATION REQUEST with CS Fallback Indicator from MME at S1 interface, eNodeB shall first decide the target system for CS Fallback, and then select the target cell. PS HO, CCO (target GERAN cell) or redirection can be used for CS Fallback, and the corresponding latency increases progressively, so ranking is necessary based on UE and target cell capabilities when selecting the target cells. The cells supporting PS HO are ranked first, After the ranking, the eNodeB shall initiate the corresponding CS Fallback to the target cell according to the first cell capability.
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4
Parameter and Configuration
4.1
Related Parameters
4.1.1
Parameter List Abbreviated name
Parameter name
byTrigQuan
Trigger Quantity
byReportQuan
Measurement report quantity
byRptCriteria
Report Criteria
byEvtId
Event Identity
byRsrpThreshold
Threshold for RSRP
byRsrqThreshold
Threshold for RSRQ
byA3offset
A3 Offset
byA5Thrd2Rsrp
A5 Threshold2 for RSRP
byA5Thrd2Rsrq
A5 Threshold2 for RSRQ
byHysterisis
Hysteresis
byTrigTime
Time to Trigger
byRptIntvl
Reporting interval for event
byRptAmt
Amount of Reporting for event
byPrdRptInterval
Reporting Interval for Periodical
byPrdRptAmount
Amount of Reporting for Periodical
byMaxRptCellNum
Maximum Cell Number reported
byReportOnLeave
The Indicator for A3 Report On Leaving
byFilterCoeffRsrp
Filter Coefficient for RSRP
byFilterCoeffRsrq
Filter Coefficient for RSRQ
byHOCandCelNum
Candidate Cell Number for Handover
byHoPartCacSwicth
Partial Admission Switch for Intra-eNB HO
ucLBMaxHOCell
Maximum number of HO cells for Load balance
byFilterCoeffGera
Filter Coefficient for GERAN
byFilterCoeffUtra
Filter Coefficient for UTRAN
byUtranMeasQuan
UTRAN Measurement Quantity
byRscpSysNbrTrd
Inter-RAT Threshold of RSCP for UTRA FDD
byEcNoSysNbrTrd
Inter-RAT Threshold of EcNo for UTRA FDD
byRatSysNbrTrd
Threshold for GERAN/CDMA System Measurement
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Abbreviated name
Parameter name
bySwitchNacc
Switch for NACC
byRd4Coverage
Redirect for Coverage
wOpenRedMeasCfg
Redirection Measurement Configuration Index
abyRdRATPriority[6]
Redirect RAT Priority
byDtmsupport
The GERAN Neighbour Cell Supports DTM Indicator
ucGERANNBRcellVoIPFlg
The GERAN Neighbour Cell Supports VoIP Indicator
ucUTRANNBRcellVoIPFlg
The UTRAN neighbour cell supports VoIP Indicator
ucUTRANNBRcellPSHOFlg
The UTRAN Neighbour Cell Supports PS HO Indicator
4.1.2
Parameter Configuration
4.1.2.1
Trigger Quantity
4.1.2.2
Parameter name
Trigger Quantity
Abbreviated name
byTrigQuan
Description
This parameter indicates the measurement quantity used to evaluate the triggering condition for the event. The quantities used to evaluate the triggering condition for the event. The values rsrp and rsrq correspond to Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ).
Range and Step
enum(rsrp, rsrq)
Unit
N/A
Default Value
rsrp
Measurement Report Quantity
4.1.2.3
Parameter name
Measurement report quantity
Abbreviated name
byReportQuan
Description
This parameter indicates whether UE should report the measurement result based on the measurement quantity RSRP
Range and Step
enum (sameAsTriggerQuantity, both)
Unit
N/A
Default Value
Both
Report Criteria Parameter name 26
Report Criteria
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4.1.2.4
4.1.2.5
Abbreviated name
byRptCriteria
Description
This parameter indicates the report rules of the Inter-Freq measurement
Range and Step
enum (Event triggered reporting, Periodical reporting)
Unit
N/A
Default Value
Event triggered reporting
Event Identity Parameter name
Event Identity
Abbreviated name
byEvtId
Description
This parameter indicates the event triggered by the InterFreq measurement, which is related to the measurement quantity.
Range and Step
A1,A2,A3, A4, A5
Unit
N/A
Default Value
A1
Threshold for RSRP Parameter name
Threshold for RSRP
Abbreviated name
byRsrpThreshold
Description
This parameter indicates the absolute RSRP threshold used for judging event A1/A2/A4/A5 for server cell. The principle of actual value of event A4 threshold corresponding to value in protocol 36.331 is -140 corresponding to 1, -139 corresponding to 2, by parity of reasoning, -44 corresponding to 97, and 0 in protocol 36.331 can not be gotten. The principle of actual value of event A5 threshold 1 corresponding to value in protocol 36.331 is -140 corresponding to 0, -139 corresponding to 1, by parity of reasoning, -44 corresponding to 96, and 97 in protocol 36.331 can not be gotten.
Range and Step
int (-140, …, -44) unit dBm
Unit
dBm
Default Value
4.1.2.6
-75
Threshold for RSRQ Parameter name
Threshold for RSRQ
Abbreviated name
byRsrqThreshold
Description
This parameter indicates the absolute RSRQ threshold used for judging event A1/A2/A4/A5 for server cell. The principle of actual value of event A4 threshold corresponding to value in protocol 36.331 is -19.5
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Handover Feature Description
corresponding to 1, -19 corresponding to 2, by parity of reasoning, -3 corresponding to 34, and 0 in protocol 36.331 can not be gotten. The principle of actual value of event A5 threshold 1 corresponding to value in protocol 36.331 is -19.5 corresponding to 0, -19 corresponding to 1, by parity of reasoning, -3 corresponding to 33, and 34 in protocol 36.331 can not be gotten.
4.1.2.7
Range and Step
int (-19.5, …, -3) step 0.5 unit dB
Unit
dB
Default Value
-8
A3 Offset
4.1.2.8
Parameter name
A3 Offset
Abbreviated name
byA3offset
Description
Range of event A3 threshold is actual value, equaling to half of value in protocol 36.331
Range and Step
float (-15, …, 15) step 0.5 unit dB
Unit
dB
Default Value
3
A5 Threshold2 for RSRP
4.1.2.9
Parameter name
A5 Threshold2 for RSRP
Abbreviated name
byA5Thrd2Rsrp
Description
This parameter indicates the absolute RSRP threshold 2 used for judging event A5 for neighbouring cell. The principle of actual value of event A5 threshold 2 corresponding to value in protocol 36.331 is -140 corresponding to 1, -139 corresponding to 2, by parity of reasoning, -44 corresponding to 97, and 0 in protocol 36.331 can not be gotten.
Range and Step
int (-140, …, -44)
Unit
dBm
Default Value
-90
A5 Threshold2 for RSRQ
28
Parameter name
A5 Threshold2 for RSRQ
Abbreviated name
byA5Thrd2Rsrq
Description
This parameter indicates the absolute RSRQ threshold offset used for judging event A5 for neighbouring cell. The principle of actual value of event A5 threshold 2 corresponding to value in protocol 36.331 is -19.5 corresponding to 1, -19 corresponding to 2, by parity of reasoning, -3 corresponding to 34, and 0 in protocol 36.331
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Handover Feature Description
can not be gotten.
4.1.2.10
4.1.2.11
4.1.2.12
Range and Step
int (-19.5, …, -3) step 0.5
Unit
dB
Default Value
-11
Hysteresis Parameter name
Hysteresis
Abbreviated name
byHysterisis
Description
This parameter indicates the hysteresis used for judging event.
Range and Step
float (0, …, 15) step 0.5
Unit
dB
Default Value
0
Time to Trigger Parameter name
Time to Trigger
Abbreviated name
byTrigTime
Description
This parameter indicates the time difference between having detected the event generation and reporting the event. Only when the event generation is detected and still meets all requirements of event triggering after Time to trigger, the event can be triggered and reported. The larger the value is, the stricter the judgment is for the event to be triggered. The parameter should be set according to the actual requirements. Sometimes, if it is set too large, the quality of calls may decrease.
Range and Step
enum (0, 40, 64, 80, 100, 128, 160, 256, 320, 480, 512, 640, 1024, 1280, 2560, 5120)
Unit
ms
Default Value
256
Reporting Interval for Event Parameter name
Reporting interval for event
Abbreviated name
byRptIntvl
Description
This parameter indicates the time interval to report the measurement results after triggering event. After event is triggered, the UE reports the measurement results according to the report intervals. If the times of event reports exceeds Amount of Reporting, UE stops reporting the measurement results.
Range and Step
enum (120, 240, 480, 640, 1024, 2048, 5120, 10240, 60000, 360000, 720000, 1800000, 3600000)
Unit
Ms
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Handover Feature Description
Default Value
4.1.2.13
4.1.2.14
4.1.2.15
4.1.2.16
30
1024
Amount of Reporting for Event Parameter name
Amount of Reporting for event
Abbreviated name
byRptAmt
Description
This parameter indicates the maximum times to report the measurement report after triggering event. After event is triggered, the UE reports the measurement results according to the report intervals. If the times of event reports exceeds the value indicated by this parameter, UE stops reporting the measurement results.
Range and Step
enum (1, 2, 4, 8, 16, 32, 64, Infinity)
Unit
N/A
Default Value
1
Reporting Interval for Periodical Parameter name
Reporting Interval for Periodical
Abbreviated name
byPrdRptInterval
Description
This parameter indicates the interval of periodical reporting when such reporting is triggered periodically.
Range and Step
enum (120, 240, 480, 640, 1024, 2048, 5120, 10240, 60000, 360000, 720000, 1800000, 3600000)
Unit
ms
Default Value
1024
Amount of Reporting for Periodical Parameter name
Amount of Reporting for Periodical
Abbreviated name
byPrdRptAmount
Description
This parameter indicates the times of the periodical reports to be reported. If the UE detects that the times of event reports exceeds the value of Amount of Reporting, UE stops reporting the measurement results.
Range and Step
enum (1, 2, 4, 8, 16, 32, 64, Infinity)
Unit
N/A
Default Value
Infinity
Maximum Cell Number Reported Parameter name
Maximum Cell Number reported
Abbreviated name
byMaxRptCellNum
Description
This parameter indicates maximum cell number reported
Range and Step
int (1, 2, …, 8)
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ZTE Confidential Proprietary
Handover Feature Description
4.1.2.17
4.1.2.18
4.1.2.19
4.1.2.20
Unit
N/A
Default Value
3
The Indicator for A3 Report On Leaving Parameter name
The Indicator for A3 Report On Leaving
Abbreviated name
byReportOnLeave
Description
This parameter indicates whether or not the UE shall initiate the measurement reporting procedure when the leaving condition is met for a cell in cellsTriggeredList. Value 0 indicates when the entering condition is met UE shall report the measurement result and value 1 shows when the entering condition or the leaving condition is met UE shall report the measurement result.
Range and Step
enum (false, true)
Unit
N/A
Default Value
false
Filter Coefficient for RSRP Parameter name
Filter Coefficient for RSRP
Abbreviated name
byFilterCoeffRsrp
Description
This parameter indicates the RSRP measurement filtering coefficient for layer 3.
Range and Step
enum (0,1,2,3,4,5,6,7,8,9,11,13,15,17,19)
Unit
N/A
Default Value
4
Filter Coefficient for RSRQ Parameter name
Filter Coefficient for RSRQ
Abbreviated name
byFilterCoeffRsrq
Description
This parameter indicates the RSRQ measurement filtering coefficient for layer 3.
Range and Step
enum (0,1,2,3,4,5,6,7,8,9,11,13,15,17,19)
Unit
N/A
Default Value
4
Candidate Cell Number for Handover Parameter name
Candidate Cell Number for Handover
Abbreviated name
byHOCandCelNum
Description
This parameter indicates the selected numbers as handover candidate cell in the cell list of measurement report.
Range and Step
enum (0,1,2,3,4,5,6,7,8)
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Handover Feature Description
4.1.2.21
4.1.2.22
4.1.2.23
4.1.2.24
32
Unit
N/A
Default Value
2
Partial Admission Switch for Intra-eNB HO Parameter name
Partial Admission Switch for Intra-eNB HO
Abbreviated name
byHoPartCacSwicth
Description
The parameter determine whether UE can handover to intra-eNB Cell .If this switch is open,UE can handover to target cell even if there is only one service admission;If this switch is closed,UE can handover to target cell when all of services gain admission.
Range and Step
enum (0 , 1) 0:close; 1:open
Unit
N/A
Default Value
close
Maximum number of HO cells for Load balance Parameter name
Maximum number of HO cells for Load balance
Abbreviated name
ucLBMaxHOCell
Description
This parameter indicates maximum number of handover cells for load balance
Range and Step
int (1, 2, …, 6)
Unit
N/A
Default Value
2
Filter Coefficient for GERAN Parameter name
Filter Coefficient for GERAN
Abbreviated name
byFilterCoeffGera
Description
This parameter indicates the filter coefficient used in the measurement to GERAN cell.
Range and Step
enum (0,1,2,3,4,5,6,7,8,9,11,13,15,17,19)
Unit
N/A
Default Value
4
Filter Coefficient for UTRAN Parameter name
Filter Coefficient for UTRAN
Abbreviated name
byFilterCoeffUtra
Description
This parameter indicates the filter coefficient used in the measurement to UTRA FDD cell.
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Handover Feature Description
4.1.2.25
4.1.2.26
4.1.2.27
4.1.2.28
Range and Step
enum (0,1,2,3,4,5,6,7,8,9,11,13,15,17,19)
Unit
N/A
Default Value
4
UTRAN Measurement Quantity Parameter name
UTRAN Measurement Quantity
Abbreviated name
byUtranMeasQuan
Description
This parameter indicates the trigger quantity used in the measurement to UTRA FDD neighbour cell.
Range and Step
enum (0, 1) 0: Cpich Ec/No; 1: Cpich RSCP
Unit
N/A
Default Value
Cpich RSCP
Inter-RAT Threshold of RSCP for UTRA FDD Parameter name
Inter-RAT Threshold of RSCP for UTRA FDD
Abbreviated name
byRscpSysNbrTrd
Description
As CPICH_RSCP of UTRA FDD cell is above this threshold, the handover to UTRA FDD cell is triggered.
Range and Step
int (-120, …, -24) unit dBm
Unit
dBm
Default Value
-95
Inter-RAT Threshold of EcNo for UTRA FDD Parameter name
Inter-RAT Threshold of EcNo for UTRA FDD
Abbreviated name
byEcNoSysNbrTrd
Description
As CPICH_Ec/No of UTRA FDD cell is above this threshold, the handover to UTRA FDD.
Range and Step
float (-24.5, …, -48) step 0.5 unit dB
Unit
dB
Default Value
-24
Threshold for GERAN Neighbour Cell Measurement Parameter name
Threshold for GERAN neighbour cell measurement
Abbreviated name
byRatSysNbrTrd
Description
This parameter indicates the threshold which is used to handover to GERAN. As the received signal power of the GERAN, the handover to GERAN is triggered. The default value consists of two value, corresponding to B1 event and B2 event.
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Handover Feature Description
4.1.2.29
4.1.2.30
4.1.2.31
4.1.2.32
34
Range and Step
int (-110, …, -47) unit dBm
Unit
N/A
Default Value
-90
Switch for NACC Parameter name
Switch for NACC
Abbreviated name
bySwitchNacc
Description
The parameter indicates whether the target GERAN support NACC. If the target GERAN cell support NACC, LTE cell can obtain basic information of GERAN cell via NACC and this information can be send to UE during handover.
Range and Step
enum(close,open)
Unit
N/A
Default Value
close
Redirect for Coverage Parameter name
Redirect for Coverage
Abbreviated name
byRd4Coverage
Description
This is a switch for the algorithm applied for coverage based redirect.If this switch is closed,redirection wouldn’t be considered
Range and Step
enum(false,true)
Unit
N/A
Default Value
false
Redirection Measurement Configuration Index Parameter name
Redirection Measurement Configuration Index
Abbreviated name
wOpenRedMeasCfg
Description
This is Redirection Measurement Configuration Index
Range and Step
0~2047
Unit
N/A
Default Value
1400
Redirect RAT Priority Parameter name
Redirect RAT Priority
Abbreviated name
abyRdRATPriority
Description
This array indicates the priority of candidate RATs for redirect target. eNB selects the target RAT based on this information. From the first array member, each denotes the corresponding priority of EUTRA, GERAN, UTRA-FDD, UTRA-TDD, CDMA2000-HRPD and CDMA2000-1xRTT
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Handover Feature Description
respectively. The value range of each integer array member is from 0 to 255. A higher value indicates a higher priority. The default value 0 means there is no applicable neighbor cell for the corresponding RAT. Each non-isolated serving cell shall be configured with the redirect RAT priority for the corresponding neighbouring cell(s).
4.1.2.33
Range and Step
int(0,…,255) step1
Unit
N/A
Default Value
[100, 0, 0, 0, 0, 0]
The GERAN Neighbour Cell Supports DTM Indicator Parameter name
The GERAN Neighbour Cell Supports DTM Indicator
Abbreviated name
byDtmsupport
Description
This parameter indicates the GERAN neighbouring cell supports DTM and DTM HO, or not.
Range and Step
enum (0,1,2) 0 ：Supports DTM and DTM HO 1 ：Supports DTM , Not Support DTM HO 2 ：Not Support DTM
4.1.2.34
4.1.2.35
Unit
N/A
Default Value
Supports DTM and DTM HO
The GERAN Neighbour Cell Supports VoIP Indicator Parameter name
The GERAN Neighbour Cell Supports VoIP Indicator
Abbreviated name
ucGERANNBRcellVoIPFlg
Description
This parameter indicates the GERAN neighbour cell supports VoIP, or not.
Range and Step
enum (Not Support VoIP,Supports VoIP)
Unit
N/A
Default Value
Not Support VoIP
The UTRAN neighbour cell supports VoIP Indicator Parameter name
The UTRAN neighbour cell supports VoIP Indicator
Abbreviated name
ucUTRANNBRcellVoIPFlg
Description
This parameter indicates the UTRAN neighbour cell supports VoIP, or not.
Range and Step
enum (Not Support VoIP,Support VoIP)
Unit
N/A
Default Value
Not Support VoIP
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Handover Feature Description
4.1.2.36
5
The UTRAN Neighbour Cell Supports PS HO Indicator Parameter name
The UTRAN Neighbour Cell Supports PS HO Indicator
Abbreviated name
ucUTRANNBRcellPSHOFlg
Description
This parameter indicates the UTRAN neighbour cell supports PS HO, or not.
Range and Step
enum(Supports PS HO,Not support PS HO)
Unit
N/A
Default Value
Supports PS HO
Glossary 1xRRT
CDMA2000 1x Radio Transmission Technology
3GPP
3rd Generation Partnership Project
B BCCH
Broadcast Control Channel
C CCO
Cell Change Order
CDMA2000
Code Division Multiple Access 2000
CIO
Cell Individual Offset
CS
Circuit-Switched
CSG
Closed Subscriber Group
D DL
Downlink
DRX
Discontinuous Reception
E
36
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Handover Feature Description
eNB EPLMN
E-UTRAN NodeB Equivalent PLMN
E-UTRAN
Evolved Universal Terrestrial Radio Access Network
F FDD
Frequency Division Duplex
G GERAN
GSM EDGE Radio Access Network
GSM
Global System for Mobile Communications
H HRPD
High Rate Packet Data
HPLMN
Home PLMN
I ID
Identity
IMSI
International Mobile Subscriber Identity
L LTE
Long-Term Evolution
M MIB
Master Information Block
MME
Mobility Management Entity
N NAS
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Non Access Stratum
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Handover Feature Description
P PS HO
Packet-switched handover
PLMN
Public Land Mobile Network
R RAT
Radio Access Technology
RSRP
Reference Signal Received Power
RSRQ
Reference Signal Received Quality
S SGW
Serving GateWay
SIB
System Information Block
SIM
Subscriber Identity Module
SRVCC
Single Radio Voice Call Continuity
T TA
Timing Advance
TA
Tracking Area
U USIM
Universal Subscriber Identity Module
UE
User Equipment
UTRAN
Universal Terrestrial Radio Access Network
UL
Uplink
V VPLMN 38
Visited PLMN
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