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2-3G Interoperability Analysis Guide

2G-3G Interoperation Analysis Guide

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Revision History

Product VersionDocument VersionSerial NumberReason for Revision

RNC V3.07R1.0First published

RNC V3.09R2.01. Add the analysis of key 2G-3G networking parameters and configuration suggestions.2. Delete some old parts.3. Optimize the document structure.4. Replace some unclear figures.

Author

DateDocument VersionPrepared byReviewed byApproved by

2009-12-20R1.0Song JianjunExpert groupExpert group

2012-05-16R2.0Ma WeiWang ZhenhaiWang Zhenhai

Intended audience: Radio network optimization engineers

Proposal: Before reading this document, you had better have the following knowledge and skills.SEQKnowledge and skillsReference material

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Follow-up document: After reading this document, you may need the following information.SEQReference materialInformation

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About This DocumentSummaryChapterDescription

1 PrefaceGives a brief introduction to this guide.

2 Introduction to 2G/3G InteroperabilityDescribes the PLMN selection and reselection, cell selection and reselection, and inter-RAT handover.

3 2G/3G Interoperability ParametersDescribes the key parameters of 2G-3G interoperation.

4 Interoperability Problems Analysis and OptimizationDescribes the analysis of common 2G-3G interoperation problems and optimization suggestions.

5 Cases StudyGives some typical cases of 2G-3G interoperation.

TABLE OF CONTENTS1Preface12Introduction to 2G/3G Interoperability22.1Network Elements Structure for 2G/3G Interoperability22.2PLMN Selection and Reselection32.2.1Process Description32.2.2Application Analysis for PLMN Selection and Reselection52.3Cell Selection and Reselection62.3.1Process Description for Cell Selection62.3.2Scenario of Inter-RAT Cell Reselection72.3.3Policy of Inter-RAT Cell Reselection82.3.4Reselection from 3G to 2G82.3.5Reselection from 2G to 3G122.4Inter-RAT Handover122.4.1Inter-RAT Handover Scenario122.4.2Inter-RAT Handover Strategies122.4.3Measurements and Decisions before Inter-RAT Handover132.4.4Inter-RAT Handover Processes1732G/3G Interoperability Parameters333.12G/3G Interconnection Parameters333.2Typical Selection and Reselection Parameters333.2.1Key 2G->3G Reselection Parameters343.2.2Key 3G->2G Reselection Parameters363.2.3Recommended Values of Key Reselection Parameters463.3Typical Inter-RAT Handover Parameters483.3.12D/2F Event Threshold483.3.23A/3C Event Threshold493.3.3Hysteresis(Rat)513.3.4Recommended Values of Key Inter-RAT Handover Parameters533.4Setting for 2G/3G Inter-RAT Neighbor Cells534Interoperability Problems Analysis and Optimization554.1Reselection Problems Analysis and Optimization564.2Handover Problems Analysis and Optimization574.2.1Physical Channel Failure584.2.2Wrong Configuration594.2.3Protocol Error594.2.4Parameter Configuration594.2.5Neighbor Cell Configuration604.2.6Resource Refusing605Cases Study615.1PLMN Selection and Reselection615.1.1Case 1615.2Cell Selection and Reselection625.2.1Case 1625.2.2Case 2625.3Inter-RAT Handover635.3.1Case 1635.3.2Case 2665.3.3Case 3675.3.4Case 4675.3.5Case 5695.3.6Case 671

FIGURESFigure 21 Network Elements Structure for 2G/3G Interoperability2Figure 22 Idle Mode Process Description3Figure 23 Scenario of 2G/3G Inter-RAT Cell Reselection for UE8Figure 24 General Process of Reselection from 3G to 2G11Figure 25 Reselection Process for the Case that WCDMA Signal Strength is too Weak to Maintain Normal Network Service12Figure 26 Handover from WCDMA to GSM in CS Domain14Figure 27 Handover from GSM to WCDMA in CS Domain15Figure 28 Signaling Process of Inter-RAT Handover in MSC: WCDMA->GSM17Figure 29 Signaling Process of Handover from WCDMA to GSM20Figure 210 Inter-RAT Handover in SGSN From UTUE To GSM (Group Domain)22Figure 211 Handover between SGSNs From UMTS To GSM (group domain)24Figure 212 nter-RAT Handover From GSM To UMTS in SGSN (Group Domain)27Figure 213 Inter-RAT Handover From GSM To UMTS in SGSN (Group Domain)29Figure 41 RR Cause Information Element57Figure 51 Sites Locations of 3A Event Trigger and 3C Event Trigger65Figure 52 TRI358 Site Location66Figure 53 Relative Location of TRI119W and TRI19168Figure 54 Success Rate of Handover after Deleting 2G Neighbor Cells68Figure 55 Relocation Failure70Figure 56 Signaling Flowchart of Inter-RAT Handover70Figure 57 Inter-RAT Handover71Figure 58 Failure Signaling of Security Mode72Figure 59 Value of Failure Reason72Figure 510 Encryption Algorithm for PS Service72Figure 511 Encryption Algorithm for CS Service72Figure 512 Encryption Algorithm73TABLESTable 21 WCDMA Cell Selection Parameters6Table 22 WCDMA Cell Reselection Parameters9Table 23 GSM Important Control Parameters of Handover Measurement16Table 31 Parameters Provided to 3G by 2G33Table 32 Parameters Provided to 2G by 3G33Table 33 Key 2G->3G Cell Reselection Parameters34Table 34 Key 3G->2G Cell Reselection Parameters34Table 35 Qqualmin Description36Table 36 SsearchRAT Description37Table 37 QRxLevMin Description38Table 38 QHyst1S Description39Table 39 Qoffset1s,n in SIB11(dB) Description40Table 310 Qoffset1s,nin SIB12(dB) Description42Table 311 Treselection Description43Table 312 Qhyst2s(dB) Description44Table 313 Qoffset2s,n in SIB11(dB) Description45Table 314 Qoffset2s,n in SIB12(dB) Description46Table 315 Recommended Values of Key 3G ->2G Reselection Parameters47Table 316 Key 2G ->3G Reselection Parameters47Table 317 2D/2F Event Configured Threshold48Table 318 3A/3C Threshold Parameter50Table 319 Hysteresis(Rat) Parameter Description51Table 320 3G->2G Parameters List53Table 41 Optimization Methods of Typical Scenarios55Table 42 Inter-RAT Handover Failure57Table 51 3C Handover Trigger Parameters for the Whole Network and Sites Distribution of 3A Handover Trigger Parameters64

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PrefaceThe low-speed data services of 2G voice, short message and circuit field have been widely used in every corner of the world, in order to meet the new requirements for the human communications better. Symbolized by high-speed data services, video telephone, and a variety of online services, 3G communications have been pushed to the front. In the current 3G and 2G development, 3G WCDMA and 2G GSM/GPRS are most widely used; therefore, in the evolution from GSM/GPRS to WCDMA, the coexistence and complementarity between the two parties are considered as a very important factor for the seamless connection between 3G and 2G.Generally speaking, 3G networks are not easy to be constructed, and it takes some time to achieve better coverage and capacity. In the early stage of 3G network construction, they cannot reach the scale as big as 2G due to the limited coverage. How 3G can provide seamless services by using 2G, and how 2G can provide the newest services by using 2G are urgent and actual problems. The better coexistence between 3G and 2G depends on the seamless connection between 3G and 2G, which makes users experience continuous and omnipresent services. The seamless connection here means the interoperability between 3G and 2G, including reselection and handover between 3G and 2G.This article first describes the principles and policies of 2G/3G interoperability, and then it makes an analysis on the key parameters involved in the interoperability. According to the baseline of the ZXWR RNC radio parameters in the WCDMA network of China Unicom, it also provides the recommended values of the main related parameters for the 2G/3G interoperability, which is a reference for commercial configuration in each field. Finally it makes a detailed analysis on the various solutions to the problems of the 2G/3G interoperability, and provides some cases for analysis. Note:Taking into account the complexity of the actual radio environment, the final values of the parameters in different fields should be adjusted reasonably based on the actual radio environment. It should not ignore the flexibility of network optimization and only comply with the recommendations in this article completely. Introduction to 2G/3G Interoperability Network Elements Structure for 2G/3G InteroperabilityFigure 21 Network Elements Structure for 2G/3G Interoperability

PLMN Selection and ReselectionProcess DescriptionWhen a UE powers up or roams, its primary task is to find the network and contact with it, in order to obtain the network service. The UE behaviors in the idle mode can be divided into PLMN selection and reselection, cell selection and reselection, and location registration. The relationship among the three processes is as follows.Figure 22 Idle Mode Process Description

PLMN Selectionand ReselectionLocationRegistrationPLMNsavailablePLMNselectedLocationRegistrationresponseRegistrationareachangesIndicationto userUser selectionof PLMNAutomatic/Manual selectionCM requestsNAS ControlRadio measurementsCell Selectionand ReselectionAfter the UE powers up, firstly it should select one PLMN. After one PLMN is selected, it starts to select one cell which belongs to the PLMN. After the cell is founded, it can get the information of the neighbor cells from system information broadcast, thus the UE can choose one cell with the best signal to reside from all the cells. Then the UE initiates the process of location registration, after success, the UE resides in the cell successfully. There are four functions for cell residence:UE can receive the system information broadcasted by PLMN. It can initiate random access process within the cell.It can receive network paging.It can receive the broadcast service from the cell. After the UE resides in the cell and registers successfully, as it moves, the signal strength of the current cell and the neighbor cell is changing constantly. The UE needs to choose the most suitable cell, which is just the cell reselection process. There are some rules for the cell reselection, and it will be described later.After the UE reselects the cell and another cell is selected, it finds that this cell belongs to another LA or RA, the UE needs to initiate the location update process, so that the network can get the latest MS location information. The system information SIB1 includes CN common GSM-MAP NAS system information and PS domain system information, in which LAC and RAC information exists, so the UE can know whether LA or RA changes. If location registration or update is not successful (for example, when the network refuses the MS), or the UE leaves the current PLMN coverage area, the UE can reselect the PLMN and select another available PLMN.The purpose of PLMN selection/reselection is to select an available PLMN. To achieve this purpose, the UE will maintain a PLMN list, in which PLMN is ordered by priority, and then is searched from the high priority to find one PLMN with the highest priority. Additionally, there are two modes for the PLMN selection and reselection: auto and manual. The auto selection is that UE selects one PLMN automatically according to the PLMN priority, the manual selection is to show all the available networks for the user, and ask the user to choose one PLMN.In the list, RPLMN (Registered PLMN) has the highest priority. The RPLMN is the PLMN which registered successfully last time. There are two files in the USIM card, EFLOCI and EFLOCI, which record the RPLMN information. In these two files, LAI (=MCC+MNC+LAC) and RAI (=LAI+RAC) include MCC and MNC, which are just RPLMN.No matter auto or manual selection, after the UE powers up, firstly it will try to select RPLMN; if it is successful, there will be no subsequent operation. If not, the UE will generate a PLMN list (ordered by priority):HPLMNThe PLMN in the USIM file User Controlled PLMN Selector with Access Technology.The PLMN in the USIM file Operator Controlled PLMN Selector with Access Technology. PLMN with better signal quality (random order).Other PLMN (order from high to low signal quality).In the USIM card, the file EFIMSI records IMSI (MCC + MNC + MSIN), from which the UE can get HPLMN. 2) and 3) are the files EFPLMNwAcT and EFOPLMNwACT in the USIM. 4) and 5) are obtained through searching the frequency one by one by the UE. The UE searches the PLMN one by one according to the PLMN list ordered by the priority above, and attempts the location registration. UMTS is evaluated from GSM and both access technologies are different completely (GERAN vs. UTRAN), so it needs to specify the preferred access technology for each PLMN. The priority of the access technologies is specified in the file ...with Access Technology. If it is not specified, generally, GERAN is preferred.In addition, PLMN needs to be reselected for the following two cases:In any case, the user can request to initiate PLMN reselection manually.VPLMN (visited PLMN) reselection:After the user registers to VPLMN for the reason of handover/roaming, as the MCC is the same between VPLMN and HPLMN (home PLMN), only MNC is different from each other, and this case can be judged by the UE. For this case, the UE will return to the home network as much as possible. The method is to search the home network periodically. This period is specified by USIM and defined in the file EFHPLMN, from 6 minutes to 8 hours. The operator can also forbid this function, in this way the value is set to 0 in the file EFHPLMN.Note: HPLMN is the registration handover and HLR information, and it is defined as follows in the protocol:The HPLMN is the GSM network that a GSM user is a subscriber of. That implies that GSM users subscription data resides in the HLR in that PLMN. The HLR may transfer the subscription data to a VLR (during registration in a PLMN) or a GMSC (during mobile terminating call handling). The HPLMN may also contain various service nodes, such as a short message service centre (SMSC), service control point (SCP), etc.VPLMN is the roaming handover information, and it is defined as follows in the protocol:The VPLMN is the GSM network where a subscriber is currently registered. The subscriber may be registered in her HPLMN or in another PLMN. In the latter case, the subscriber is outbound roaming (from HPLMNs perspective) and inbounds roaming (from VPLMNs perspective). When the subscriber is currently registered in her HPLMN, then the HPLMN is at the same time VPLMN.Application Analysis for PLMN Selection and ReselectionBy using the functions of PLMN selection and reselection, the inter-RAT selection and roaming functions can be implemented without any upgrading for the GSM and WCDMA networks. The user can return to the WCDMA network from the GSM network by PLMN reselection. For the WCDMA user can handover to the WCDMA network from the GSM network when entering the coverage area of WCDMA, you can set different PLMNs for the WCDMA and GSM networks and set HPLMN for the WCDMA network in the USIM. And the selection time can be controlled by the operator.Cell Selection and ReselectionProcess Description for Cell SelectionCell selection process includes cell searching and reading broadcast channel. Cell searchingFirstly, if a UE has stored some relevant information of this PLMN, such as frequency, scrambling code, etc, the UE will use this information to search the cell (stored information cell selection) and find the network quickly. The information is stored in the USIM card or in the non-volatile memory of the cell phone. The purpose of cell searching is to find a cell, and the steps are as follows:Time slot synchronization by the synchronization code of PSCH.Frame synchronization, implemented by the synchronization code of SSCH, and the scrambling code group of the cell is confirmed.Obtaining the main scrambling code of the cell through CPICH, and then the UE can read the broadcast channel.Obviously, if the UE has already known some information of this cell, such as frequency and main scrambling code, the steps mentioned above can be speeded up. Reading broadcast channelMain information block MIBs dispatching information is already known, that is SIB_POS = 0, SIB_REP = 8. The UE can read out the MIB in the radio frame of SFN = 0, 8, 16 ... After reading out the MIB, the UE can judge whether the founded PLMN is the one expected by the field PLMN identity in the MIB. If yes, according to the other SIBs dispatching information in the MIB, the UE can the find the other SIB and obtain its content. If not, the UE needs to find the next frequency and start the process again from the cell searching. If the current PLMN is the one that the UE is looking for, the UE reads SIB3 and obtains Cell selection and re-selection info, in this IE, it reads out Qqualmin, Qrxlevmin, and Maximum allowed UL TX power (UE_TXPWR_MAX_RACH), it calculates according to the formula below:

Table 21 WCDMA Cell Selection ParametersParameterDescription

Squal Cell Selection quality value, (dB)Not applicable for TDD cells or GSM cells.

SrxlevCell Selection RX level value (dB)

QqualmeasMeasured cell quality value. The quality of the received signal expressed in CPICH Ec/No (dB) for FDD cells. Not applicable for TDD cells or GSM cells.

QrxlevmeasMeasured cell RX level value. This is received signal, CPICH RSCP for FDD cells (dBm), P-CCPCH RSCP for TDD cells (dBm) and RXLEV for GSM cells (dBm).

QqualminMinimum required quality level in the cell (dB). Not applicable for TDD cells or GSM cells. (read in system information)

QrxlevminMinimum required RX level in the cell (dBm). (read in system information)

PcompensationMax(UE_TXPWR_MAX_RACH - P_MAX, 0) (dB)

UE_TXPWR_MAX_RACHMaximum TX power level a UE may use when accessing the cell on RACH (read in system information), (dBm)

P_MAXMaximum RF output power of the UE, (dBm)

If

Then the UE considers this cell as a suitable cell, it resides and reads the other system information as needed, then the UE initiates the location registration process. If the criteria above is not satisfied, the UE reads the SIB11 to obtain the main scrambling code and the frequency of the neighbor cell, it can measure the Qqualmeas and Qrxlevmeas of the neighbor cell, in the IE Cell Selection and Re-selection info for SIB11/12, the UE can know the neighbor cells Maximum allowed UL TX power, Qqualmin and Qrxlevmin, thus the UE can calculate the neighbor cells Squal and Srxlev, and judge whether the neighbor cell satisfies the criteria above. If the UE can find any neighbor cell that satisfy the selection criteria, it will reside in the cell and read the other system information as needed, then initiate the process of location registration. If the UE cannot find a cell that satisfies the selection criteria, the UE will consider that it is not covered and continue to select and reselect PLMN.Scenario of Inter-RAT Cell ReselectionThe 2G/3G inter-RAT cell reselection mainly occurs in the following two modes.Idle ModeA UE performs the inter-RAT cell reselection in the idle states of WCDMA, GSM and GPRS. The UE measures the serving cell according to the parameters of network broadcast and determines whether to reselect another cell. Connected ModeA UE performs the inter-RAT cell reselection in the group connected states of Cell_FACH and Cell_PCH/URA_PCH.Figure 23 Scenario of 2G/3G Inter-RAT Cell Reselection for UE

Policy of Inter-RAT Cell ReselectionThe current policy of inter-RAT cell reselection for the 2G/3G interoperability is a bidirectional reselection between 2G and 3G. However, it performs the cell reselection from 3G to 2G only when a UE moves out the scale of 3G coverage. And once it returns to the scale of 3G coverage, the UE will initiate the cell reselection from 2G to 3G.Reselection from 3G to 2G1.Planning for the cell reselection measurementWhen a UE is in the idle mode, it needs to monitor the signal quality of the current and neighbor cells at any moment for selecting the best cell to provide service, this is called cell reselection.In the following rules, the UE uses Squal for FDD cells and Srxlev for TDD for Sx.i.If Sx > Sintrasearch, the UE does not perform co-frequency measurement; if Sx < Sintrasearch, the UE performs co-frequency measurement. If the current cell does not send Sintrasearch to the UE, the UE performs co-frequency measurement.ii.If Sx > Sintersearch, the UE does not perform inter-frequency measurement; if Sx < Sintersearch, the UE performs inter-frequency measurement. If the current cell does not send Sintersearch to the UE, the UE performs inter-frequency measurement.iii.If Sx > SsearchRATn, the UE does not perform system measurement; if Sx < SsearchRATn, the UE performs inter-RAT measurement. If the current cell does not send SsearchRATn to the UE, the UE performs inter-RAT system measurement.Sintrasearch, Sintersearch and SsearchRATn are specified in the SIB3s Cell selection and re-selection info.The UE measures the neighbor cells which satisfy the conditions mentioned above, firstly it calculates the S values for all the cells (including the current and neighbor cells) according to the cell selection method, for the all the cells which meet the condition S>0, calculate the R according to the formulas below.Rs = Qmeas,s + QhystsRn = Qmeas,n - Qoffsets,nRs: the R value of the serving cellRn: the R value of the neighbor cellQmeas: the signal measurement value of a cell, it adopts CPICH Ec/No or CPICH RSCP for the FDD cellQoffset1s,n: the offset between two cells, it is used for the FDD cell when the measurements of the cell selection and reselection are set to be CPICH RSCP.Qoffset2s,n: the offset between two cells, it is used for the FDD cell when the measurements of the cell selection and reselection are set to be CPICH Ec/No.Qhyst1s: the hysteresis value, it is used for the FDD cell when the measurements of the cell selection and reselection are set to be CPICH RSCP.Qhyst2s: it is used for the FDD cell when the measurements of the cell selection and reselection are set to be CPICH Ec/No.Treselection: the timer value for the cell reselectionTable 22 WCDMA Cell Reselection ParametersParameterDescription

Cell_selection_and_reselection_quality_measure (FDD only)Choice of measurement (CPICH Ec/N0 or CPICH RSCP) that is used to derive quality measures Qmap,n and Qmap,s, (read in system information).

Qmeas,sQuality of the serving cell, derived from CPICH Ec/N0 or CPICH RSCP for FDD cells, from RXLEV for GSM cells. For FDD cells, the measurement that is used to derive the quality value is set by the Cell_selection_and_reselection_quality_measure information element.

Qmeas,nQuality of the neighboring cell, derived from CPICH Ec/N0 or CPICH RSCP for FDD cells, from RXLEV for GSM cells. For FDD cells, the measurement that is used to derive the quality value is set by the Cell_selection_and_reselection_quality_measure information element.

Qoffset1s,nOffset value 1between the two cells considered in the evaluation (read in system information).

Qoffset2s,n,Offset value 2 between the two cells considered in the evaluation (read in system information).

Qhyst1sHysteresis value of the serving cell.

Qhyst2sHysteresis value of the serving cell.

TreselectionsTime-to-trigger for cell reselection, (s)

2.General process of reselectionA: When the pilot Ec/No of the WCDMA serving cell is smaller than Qqualmin+SsearchRAT, the UE starts to measure the signal strength of the neighbor GSM/GPRS cells. The SsearchRAT parameter is broadcasted in SIB3/4.A -> B: The UE starts to rank the signal strength of WCDMA serving cells and GSM/GPRS neighbor cells. Rank of serving WCDMA = RSCP_WCDMA + QHyst1sRank of neighbor GSM/GPRSn = RSSIGSMn - Qoffset1s,nB: When a GSM cell ranks the top, the Treselection timer is started. C: When a GSM cell ranks the top and it keeps for Treselection seconds, the UE reselects to the corresponding GSM cell as shown in the following figure. Figure 24 General Process of Reselection from 3G to 2G

3.Reselection process for special cellWhen the signal strength of WCDMA is too weak to maintain a normal network service, the process of cell reselection is as follows.A: The WCDMA serving cell cannot maintain a normal network service (pilot Ec/No > Qqualmin, but pilot RSCP < Qrxlevmin)A -> B: The WCDMA serving cell cannot maintain a normal network service, and it lasts for a period of Nserv DRX Cycles.B: UE measures and ranks all the neighbor cells in the neighbor cell list. It starts a timer when a GSM cell ranks the top.Rank of WCDMA = RSCP_WCDMA + QHyst1sRank of neighbor GSM/GPRSn = RSSIGSMn - Qoffset1s,nC: When a GSM cell ranks the top and it lasts for Treselection seconds, the UE reselects to the corresponding GSM cell as shown in the following figure.Figure 25 Reselection Process for the Case that WCDMA Signal Strength is too Weak to Maintain Normal Network Service

Reselection from 2G to 3GIn the idle state, inter-RAT selection can be implemented by cell selection and reselection. Additionally, the standards for the signal quality in the two GU systems are different, so the parameters setting for the selection and reselection needs to be very cautious, or it may occur inappropriate cell selection or ping-pong selection.Inter-RAT HandoverInter-RAT Handover ScenarioThe handover between WCDMA and GSM/GPRS occurs in the Cell_DCH state of the connected mode, and an effective handover between WCDMA and GSM/GPRS can ensure that the users can use the current service continuously.The typical process of inter-RAT handover: once UE is in the connection state (the CELL_DCH state in WCDMA), it performs the measurement instruction from network, and reports the result to the network by period or event, the network judges the UE signal quality based on the reported result, and determines whether the cell phone to handover.Inter-RAT Handover StrategiesInter-RAT Handover Strategies for Different Stages1.Coverage HandoverIn the initial stage of 3G construction, given the network condition of continuous GSM coverage and limited 3G coverage, it adopts the handover based on coverage for the places with poor coverage.2.Load HandoverIn the middle and late stages of 3G construction, 3G network extends very fast, 3G and 2G networks overlap basically, 2G network needs to share load for 3G network, it adopts load handover that is based on the load of 3G network.3.Service HandoverIn the middle and late stages of 3G construction, the RNC of 3G network receives RAB assignment message, the services should be handed over to 2G according to the requirement from core network, thus 3G users are handed over to 2G network, and it is called service handover.Current Inter-RAT Handover StrategyAt present, given the network condition of continuous GSM coverage and limited 3G coverage, it adopts the handover based on coverage for the places with poor coverage. The specific handover strategy is as follows: it is a one-way handover from 3G to 2G for CS, and it is a two-way handover from 3G to 2G for PS. So the handover process from 2G to 3G for CS will not be described in this article. Measurements and Decisions before Inter-RAT HandoverThe typical process of inter-RAT handover: once UE is in the connection state (the CELL_DCH state in WCDMA), it performs the measurement instruction from network, and reports the result to the network by period or event, the network judges the UE signal quality based on the reported result, and determines whether the cell phone to handover. The inter-RAT measurement processes in WCDMA and GSM are introduced below.Start Measurement to GSM in WCDMAThe process of starting measurement to GSM: When a UE finds that the value of carrier evaluation quality in the current system is lower than the assigned threshold in the measurement control, it reports a 2D event to the network. The WCDMA system requests the UE to start the compact mode, and the UE starts to measure the inter-RAT signal quality (if the UE finds that the value of carrier evaluation quality in the current system is higher than the assigned threshold in the measurement control, it stops the compact mode and inter-RAT measurement). When it satisfies the condition of 3A (or 3C) event trigger threshold, the UE reports the 3A (or 3C) event to the network. And the network triggers the inter-RAT handover command according to the information of measurement report and GSM neighbor cell in order to that the UE can switches to the destination cell. Note: The UE also can report the signal quality periodically and the network determines whether the trigger condition of 3A (or 3C) is satisfied.The related process is as follows. Figure 26 Handover from WCDMA to GSM in CS Domain

Start Measurement to WCDMA in GSMThe process of starting measurement to WCDMA: When a UE enters a GSM cell with 3G neighbor cells, the information of 3G neighbor cells and 3G measurement parameters are included in the measurement information instruction from the network, which requires the UE to measure the assigned 3G neighbor cells and report the result. Thus whether to perform an inter-RAT handover is determined by the 2G network. The related process is as follows.Figure 27 Handover from GSM to WCDMA in CS Domain

Handover Measurement Parameter Setting Preferred 3G1.GSM Parameter SettingThe main 3G parameters in Measurement Information include 3G Neighbour Cell Description and 3G MEASUREMENT PARAMETERS Description. The information of 3G neighbor cells is defined in the first parameter, and the informaiton of 3G measurement parameters setting is defined in the second parameter. In some foreign PLMNs, there is no information of 3G measurement parameters, which means that it will read the Qsearch_C_Initial parameter broadcasted on BCCH, and the handover measurement is carried out through the definition of the parameter. Other main parameters are in the SYSTEM_INFORMATION_2QUATER.Qsearch_C is set to 7, which shows an unconditional inter-RAT measurement. It is same to the Qsearch_I in the inter-RAT reselection parameters.REPORT_TYPE shows the type of measurement report, generally it is the enhanced Extended Measurement Report, but the default value is Common Measurement Report. 3G_SEARCH_PRIO shows that it can scan on the frame that is generally used for BSIC decoding, because the 3G neighbor cells do not need BSIC decoding (If indicated by the parameter 3G_SEARCH_PRIO, the UE may use up to 25 search frames per 13 seconds without considering the need for BSIC decoding in these frames). The default value is TRUE.FDD_REP_QUANT shows the reported type, RSCP or Ec/No.Table 23 GSM Important Control Parameters of Handover MeasurementParameter nameDescriptionRangeBitsMessage

Qsearch_C_InitialIndicates the Qsearch value to be used in connected mode before Qsearch_C is received,0 = use Qsearch_I, 1 = (always).Default value = use Qsearch_I.0/11BCCH D/L

Qsearch_CSame to Qsearch_I0-154SACCH D/L

REPORT_TYPEIndicates which report type the UE shall use,0 = enhanced, 1 = normalDefault value = normal0/11BCCH D/LSACCH D/L

3G_SEARCH_PRIOIndicates if 3G cells may be searched when BSIC decoding is required,0 = no, 1 = yesDefault value = yes0/11SACCH D/L

FDD_REP_QUANTIndicates the reporting quantity for UTRAN FDD cells,0 = RSCP, 1 = Ec/No0/11PBCCH D/L PCCCH D/LPACCH D/L(**)

2.GSM Signal MeasurementThe measurement to a GSM cell can be divided into two modes: BSIC check and no BSIC check. It only needs to measure GSM carrier RSSI for the no BSIC check mode. For the BSIC check mode, the two processes of Initial BSIC identification and BSIC re-confirmation are also needed.Initial BSIC identification: the process of BSIC searching and decodingBSIC re-confirmation: the tracing and decoding processes to the BSIC of a GSM cell after the Initial BSIC identificationIf the measurement to a GSM cell is BSIC check, the UE behaviors are as follows:The UE performs the GSM carrier RSSI measurement according to the TGPS setting with a target of GSM carrier RSSI measurements.The UE performs the initial BSIC identification according to the TGPS setting with a target of GSM Initial BSIC identification. If there are multiple GSM cells, it will perform the process according to the order of signal strength in the recent GSM carrier RSSI measurement.The UE performs the BSIC reconfirmation according to the TGPS setting with a target of GSM BSIC re-confirmation.Judging the BSIC check: The UE decodes the SCH on BCCH and identifies the BSIC for at least one time, after that, the BSIC is confirmed again for each Tre-confirm_abort seconds, then the BSIC of GSM cell is considered to be checked. Otherwise it is considered to be unchecked. Accepting or discarding the BSIC check:There may be multiple cells with the same ARFCN but different BSICs among the GSM cells in WCDMA. For the measurements without the BSIC check, which means that the BSIC is not judged, the network cannot distinguish which GSM cell each measurement belongs to, and the handover may fail as the destination is not clear. Therefore it must adopt the BSIC check.Inter-RAT Handover ProcessesHandover From 3G to 2G in CS DomainIn the initial stage of 3G construction, in order to keep the continuity of service in the edge of 3G coverage, it is necessary to support the handover from WCDMA to GSM.1.Intra-MSCFigure 28 Signaling Process of Inter-RAT Handover in MSC: WCDMA->GSM

RNS-A is the RNS where the cell phone locates before handover; BSS-B is the BSS where the cell phone locates after handover. All the messages above can be tracked in the user interface, Iu interface, and A interface. RI is Radio Interface. RRC is Radio Resource Control. 3G_MSC-A is the MSC where the cell phone locates before handover. i.RNS-A sends the RELOCATION_REQUIRED message to 3G_MSC-A. The available cell list and handover reason are included in this message. 3G_MSC-A choose one cell in the list as the destination cell. 3G_MSC-A queries the location of the destination cell according to the destination cell number, and determines the handover is intra-office or interoffice.ii.3G_MSC-A sends the HO_REQUEST message to BSS-B. After receiving the handover request, 3G_MSC-A queries in the corresponding tables and finds that the destination cell is the cell controlled by its subordinated BSS. Then 3G_MSC-A constructs the corresponding GSM handover request message according to the handover request, and sends the message to BSS-B. When constructing the request message, 3G_MSC-A needs to complete the interworking between UMTS and GSM handover request messages. Then 3G_MSC-A can send the HO_REQUEST message to BSC-B.iii.BSS-B sends the HO_REQUEST_ACK message to 3G_MSC-A. After BSS-B applies the radio resource and gets the circuit ready, it sends this message to 3G_MSC-A, the HANDOVER_COMMAND message is included in this message and will be transmitted transparently by RNS-A to the handover request side, which is called RNS-A.iv.3G_MSC-A sends the RELOCATION_COMMAND message to RNS-A. After MSC-A receives the HO_REQUEST_ACK message from BSS-B, it means that the radio resource of new interface A is ready and the cell phone can hand over to BSS-B from RNS-A, at this time it sends handover command message to notify the cell phone to hand over. v.BSS-B sends the HO_DETECT message to 3G_MSC-A. At this time the cell phone has already detected the new channel and has the condition to access the new radio channel, but actually has not accessed yet. As it is voice handover, the voice channel must be built up, so 3G_MSC-A connects the time slot of the opposite end to time slot of new interface, and continues to call by using the resource applied in the process of handover. vi.BSS-B sends the HO_COMPLETE message to 3G_MSC-A. The new channel has been built up, the user continues to call or be in the process of other services. BSS-B reports the handover completion message to 3G_MSC-A.vii.3G_MSC-A sends the LU RELEASE_COMMAND message to RNS-A. After the handover is completed, 3G_MSC-A sends RRC HO Command message to the source RNS-A, and releases the original radio resource. viii.RNS-A sends the LU RELEASE COMPLETE message to 3G_MSC-A. RNS-A releases the radio resource.2.Inter-MSCFor the inter-RAT handover, if a UE only has the circuit domain service, it follows the handover process of the circuit domain from WCDMA to GSM. The typical handover process includes: measurement control -> measurement report -> handover judge->handover execute.In the stage of measurement control, the network tells UE the measurement parameters by sending measurement control message. In the stage of measurement report, the UE sends measurement report to the network. In the stage of handover judge, the network determines to handover according to the measurement report. In the stage of handover execute, the UE and the network follow the signaling process, and take actions according to the signaling.For the handover from WCDMA to GSM, when the user is in the edge of WCDMA system and needs to handover between systems, WCDMA RNC notices the UE to start an inter-RAT measurement. The UE carries out the inter-RAT measurement and reports the result, RNC determines whether to execute the signaling process for inter-RAT handover according to the result. As the access mode of WCDMA is code division multiple access, all the connected UEs work under the specified frequency for all time, in order to continue to call in the process of inter-RAT measurement, WCDMA system and the UE may need to start the compression mode (if the UE only has one transceiver, it must start the compression mode; if the UE has two transceivers, the UE can test GSM cell without starting the compression mode).The signaling process of handover from WCDMA to GSM is as follows.Figure 29 Signaling Process of Handover from WCDMA to GSM

i.When URRAN determines to handover between systems based on the measurement, SRNC sends RANAP message RELOCATION REQUIRED to CN, and requests the other system to prepare for the handover.ii.WCDMA CN forwards this request to GSM UEC (through MAP/E message PREPARE HANDOVER).iii.GSM UEC sends the HANDOVER REQUEST message to BSC.iv.After GSM BSS gets the resource ready for the handover between systems, BSC replies the HANDOVER REQUEST ACK message to GSM UEC.v.GSM UEC sends MAP/E message PREPARE HANDOVER RESPONSE to WCDMA CN.vi.WCDMA CN answers the initial request from SRNC through sending RANAP message RELOCATION COMMAND.vii.SRNC sends the message HANDOVER FROM UTRAN COMMAND to UE through the existing RRC connection, and requests UE to handover from WCDMA to GSM.viii.UE hands over from WCDMA to GSM (hard handover), UE sends the message HANDOVER COMPLETE to BSC, notices BSC that the handover is completed, BSC sends the message HANDOVER COMPLETE to GSM UEC.ix.Combined with Step viii.x.Combined with Step viii.xi.When detecting that UE is in the area covered by GSM, GSM UEC sends the message SEND END SIGNAL REQUEST to WCDMA CN and notices WCDMA CN that the handover is completed, and the WCDMA resource occupied by this UE can be freed.xii.CN sends LU RELEASE COMMAND to RNC and notifies the original SRNC to free the resource. When the relevant resource in WCDMA is completed to free, WCDMA responses to GSM UEC and then the handover process is finished.xiii.Combined with Step xii.xiv.Combined with Step xii.Handover From 3G to 2G in PS DomainGroup domain handover from 3G to 2.5G is supported, and GSM BSS does not need to change.The version of GTP is negotiated between GSM SGSN and WCDMA SGSN by using the standard program. The backward compatibility of GTP protocol can assure the compatibility of GSM/WCDMA. The destination GSM SGSN will contact with the source WCDMA SGSN. If both the source and destination SGSNs support 3GPP R99, it adopts GTP v1; if GSM SGSN does not support 3GPP R99, it adopts GTP v0. In this case, some services may be degraded. The destination GSM SGSN will degrade the PDP contexts (such as Real time PDP contexts) which cannot be processed.If HLR does not support the version of 3GPP R99 MAP either, the version of MAP infoRetrievalContext will be rollback to v2. If it is WCDMA user, the HLR where it locates must support MAP v3.1.Intra-SGSNIt occurs when a UE radio interface hands over from UTRAN interface to GSM interface, UTRAN interface and GSM interface are connected to one SGSN. Figure 210 Inter-RAT Handover in SGSN From UTUE To GSM (Group Domain)

i.The UE hands over from UTRAN to the cell which supports GSM interface.ii.The UE initiates routing area update request.iii.2G+3G-SGSN sends the SRNS CONTEXT REQthe UEST (IMSI) message to SRNS, after SRNS receives the request, it begins to stop sending the downlink data and caches, at the same time it notices SGSN the serial number of datagram (GTP-SNDs, GTP-SNUs, PDCP-SNDs, PDCP-SNUs) through the SRNS CONTEXT RESPONSE message.iv.Combined with Step iii.v.Execute security function (optional).vi.2G+3G-SGSN sends the SRNS DATA FORWARD COMMAND message to SRNS, and notices SRNS to start to send the cached data back to SGSN, SRNS forwards the cached data.vii.Combined with Step vi.viii.The cached data is completed to forward, 2G+3G-SGSN releases the lu link.ix.If it is joint routing update and attached by IMSI or the location area changes, 2G+3G-SGSN sends the location update message to VLR. x.If the user data in VLR is not confirmed by HLR, the new VLR notices HLR to delete the user data in the old VLR, and inserts users in the new VLR. xi.The new VLR assigns new VLR TMSI and notices SGSN.xii.2G+3G-SGSN checks whether the user is forbidden to roam, if it is allowed, 2G+3G-SGSN can assign new P-TMSI, and send the ROUTING AREA UPDATE ACCEPT message to notice the UE.xiii.the UE can send the ROUTING AREA UPDATE COMPLETE (Receive N-PDU Number) message to SGSN, and notice SGSN that the serial number of datagram has been received. SGSN continues to forward the datagram that is after this serial number to the UE. xiv.If the UE has accepted VLR Tthe UEI, 2G+3G-SGSN sends the Tthe UEI REALLOCATION COMPLETE message to the new VLR.xv.2G+3G-SGSN and BSSs optional BSS Packet Flow Context flow, build up BSS Packet Flow. If UE is CAMEL user, the following processes will be triggered:i.CAMEL_GPRS_Routeing_Area_Update_Sessionii.CAMEL_GPRS_Routeing_Area_Update_Context2.Inter-SGSNThe process of group domain handover between SGSNs from UMTS to GSM is as shown in figure below.Figure 211 Handover between SGSNs From UMTS To GSM (group domain)

UE/MSnew2G-SGSNHLRGGSNold3G-SGSN 2. Routing Area Update Request 10. Update PDP Context Request 10. Update PDP Context Response 11. Update GPRS Location 15. Update GPRS Location Ack 5. SGSN Context Response 6. Security Functions 19. Routing Area Update Accept 12. Cancel Location 12. Cancel Location Ack 14. Insert Subscriber Data Ack 14. Insert Subscriber Data 7. SGSN Context AcknowledgeBSSSRNS 3. SGSN Context Request 13. Iu Release Command 13. Iu Release Complete 8a. Forward Packets 9. Forward Packets 4. SRNS Context Request 4. SRNS Context Response 8. SRNS Data Forward Command 22. BSS Packet Flow Context Procedure1. Inter-RAT changedecisionC3C1 20. Routing Area Update CompletenewMSC/VLRoldMSC/VLR 16. Location Update Request 17a. Update Location 17b. Cancel Location 17c. Cancel Location Ack 17d. Insert Subscriber Data 17e. Insert Subscriber Data Ack 17f. Update Location Ack 18. Location Update Accept 21. TMSI Reallocation CompleteC2i.The UE (UE is in the non-Cell-DCH state) or UTRAN (the UE is in the state of Cell-DCH or Cell_FACH) determines to initiate the group domain inter-RAT handover, in this way the UE is handed over to another new cell which supports GSM, at the same time the data transmission between the UE and network is stopped.ii.The UE initiates routing area update request to 2G-SGSN, routing area update or joint RA/LA update or joint RA/LA update with IMSI attached will be specified for the update type, before the message is sent to SGSN, BSS will add the CGI with RAC and LAC where it locates to the message received.iii.The new 2G-SGSN sends the SGSN Context Request message to the old 3G-SGSN for obtaining MM and PDP contexts, the old 3G-SGSN verifies the PTMSI signature of the UE. If it is successful, the old SGSN will start a timer; if the old SGSN does not recognize the UE, it will reply an appropriate error reason.iv.If the UE is in the state of PMM-CONNECTED before handover, the old 3G-SGSN sends SGSN Context Request message to SRNS, after receiving this message, SRNS starts to cache and stops to send data to PDU, and replies SRNS CONTEXT RESPONSE message to the old 3G-SGSN.v.The old 3G-SGSN sends the SGSN CONTEXT RESPONSE message to 2G-SGSN, in which MM and PDP contexts are included.vi.Execute security function.vii.The new 2G-SGSN sends the SGSN CONTEXT ACKNOWLEDGE message to 3G-SGSN, and notices 3G SGSN that the current 2G SGSN can accept the relevant data PPDU of activated PDP context.viii.If the cell phone is in the state of PMM-CONNECTED, the old 3G-SGSN sends data forward command to SRNS. After receiving the command, SRNS starts the data forward timer, SNNS sends the cached data PDU to the old SGSN.ix.The old 3G-SGSN sends GTP PDUs to 2G-SGSN by tunnel mode, the serial number in the head of GTP (obtained from the number of PDCP) does not change. x.The new 2G-SGSN sends the Update PDP CONTEXT REQUEST message to each relevant GGSN. GGSN updates PDP context and returns Update PDP Context Response.xi.The new 2G-SGSN sends the UPDATE GPRS LOCATION message to notice HLR to change SGSN number.xii.HLR sends the CANCEL LOCATION message to notice the old 3G-SGSN to cancel the location. The old 3G SGSN responses by the CANCEL LOCATION ACK message. After the clocking of operation timeout is completed, the old 3G-SGSN deletes MM and PDP Context.xiii.If the UE is in the state of PMM-CONNECTED, 3G-SGSN sends the LU RELEASE COMMAND message to SRNS, after the clocking of data forwarding is completed, SRNS responses by the LU RELEASE COMPLETE message.xiv.HLR sends the INSERT SUBSCRIBER DATA message to the new 2G-SGSN, 2G SGSN inserts subscription data to MM context and PDP context, and responses by the INSERT SUBSCRIBER DATA ACK message.xv.HLR confirms the modification is completed, and sends the UPDATE GPRS LOCATION message to 2G-SGSN.xvi.If the association is to be built up, the new 2G SGSN sends the LOCATION UPDATE REQUEST message to VLR, and notices the new the UEC/VLR to initiate location update; VLR can create or update association by saving SGSN number.xvii.If the user data mark in the VLR is not confirmed by HLR, VLR will notice HLR. HLR cancels the old VLR and inserts the user data to the new VLR:a)The new VLR sends the UPDATE LOCATION message to HLR. b)HLR cancels the data in the old VLR by sending the CANCEL LOCATION message to the old VLR. c)The old VLR responses by the CANCEL LOCATION message.d)HLR sends the INSERT SUBSCRIBER DATA ACK message to the new VLR.e)The new VLR responses by the INSERT SUBSCRIBER DATA ACK message.f)HLR responses to the new VLR by the UPDATE LOCATION ACK message.xviii.The new VLR assigns TMSI for the UE, and sends the LOCATION UPDATE ACCEPT message to notice 2G-SGSN.xix.The new 2G-SGSN verifies the validity of the UE in the new routing area, if all the checks are successful, 2G SGSN builds up MM context and PDP context, and establishes a logical link between the UE and 2G SGSN through 2G SGSN, 2G SGSN responses the ROUTING AREA UPDATE ACCEPT message to the UE.xx.The UE confirms the new assigned PTMSI by sending the ROUTING AREA UPDATE COMPLETE message, including confirming the data PDU sent to the UE successfully before the routing area update is initiated. xxi.After confirmed by the UE, 2G-SGSN sends the TMSI REALLOCATION COMPLETE message to notice VLR TMSI that the assignment is completed again.xxii.2G-SGSN and BSS execute BSS Packet Flow Context procedure.Handover From 2G to 3G in PS Domain1.Intra-SGSNWhen a UE radio interface hands over from GSM interface to UTRAN interface, UTRAN interface and GSM interface are connected to one SGSN.Figure 212 Inter-RAT Handover From GSM To UMTS in SGSN (Group Domain)

i.The UE hands over from UTRAN to the cell which supports UTRAN interface.ii.The UE initiates routing update request, the 2G+3G-SGSN stops forwarding data to the UE and caches.iii.Execute security function (optional).iv.If it is joint routing update and attached by IMSI or the location area changes, the 2G+3G-SGSN sends the LOCATION UPDATE message to VLR.v.If the user data in VLR is not confirmed by HLR, the new VLR notices HLR to delete the user data in the old VLR, and inserts users in the new VLR.vi.The new VLR assigns new VLR TUEI and notices the SGSN.vii.The 2G+3G-SGSN checks whether the user is forbidden to roam, if it is allowed, the 2G+3G-SGSN can assign new P-TUEI, and send the ROUTING AREA UPDATE ACCEPT message to notice UE.viii.The UE sends the ROUTING AREA UPDATE COMPLETE message to the SGSN by using the new P-TUEI.ix.If the UE accepts VLR TUEI, 2G+3G-SGSN sends the TUEI REALLOCATION COMPLETE message to the new VLR.x.If the UE needs to send signaling or uplink data, the UE can initiate the service request process. If the 2G+3G-SGSN needs to forward signaling or downlink data, the 2G+3G-SGSN will initiate the paging process.xi.The 2G+3G-SGSN requests SRNS to build radio bearer by RAB assignment.xii.Data forwarding recovers.xiii.Combined with Step xii.If the UE is CAMEL user, the following processes will be triggered:i.CAMEL_GPRS_Routeing_Area_Update_Sessionii.CAMEL_GPRS_Routeing_Area_Update_Context.2.Inter-SGSNThe process of group domain handover between SGSNs from GSM to UNTS is as shown in figure below.Figure 213 Inter-RAT Handover From GSM To UMTS in SGSN (Group Domain)

UE/MSnew3G-SGSNHLRGGSNold2G-SGSN 8. Update PDP Context Request 8. Update PDP Context Response 9. Update GPRS Location 12. Update GPRS Location Ack 2. Routing Area Update Request 4. SGSN Context Response 5. Security Functions 16. Routing Area Update Accept 10. Cancel Location 10. Cancel Location Ack 11. Insert Subscriber Data Ack 11. Insert Subscriber Data 17. Routing Area Update Complete 6. SGSN Context AcknowledgeBSSSRNS 3. SGSN Context Request 20. RAB Assignment Response 7. Forward Packets1. Inter-RATchange decisionC3C1 newMSC/VLR oldMSC/VLR 13. Location Update Request 14a. Update Location 14b. Cancel Location 14b. Cancel Location Ack 14c. Insert Subscriber Data 14d. Insert Subscriber Data Ack 14e. Update Location Ack 15. Location Update Accept 18. TMSI Reallocation CompleteSet up RadioResources 19. Service RequestC2 20. RAB Assignment Requesti.The UE or BSS determines to handover between systems for group domain, which makes the UE handover to another new WCDMA cell, at the same time the data transmission is stopped between the UE and the network.ii.The UE sends routing area update request to the new 3G-SGSN. Routing area update or joint RA/LA update or joint RA/LA update with IMSI attached will be specified for the Update Type, before the message is sent to SGSN. Before sending the user message to SGSN, SRNC will add the RAC and LAC routing identifiers of the area where the UE locates.iii.The 3G-SGSN obtains the address of the old 2G-SGSN through the old routing area identifier from the UE, and then sends the SGSN CONTEXT REQUEST message to the old 2G-SGSN, in order to obtain MM context and PDP context of the user. The old 2G-SGSN verifies the P-TMSI signature of the UE, if the P-TMSI signature is valid or 3G-SGSN indicates that the UE has already been authenticated, the 2G-SGSN starts a timer.iv.The old 2G-SGSN responds through the SGSN CONTEXT RESPONSE message, which includes MM Context and PDP Context.v.A security function process is initiated.vi.The 3G-SGSN sends the SGSN CONTEXT ACKNOWLEDGE message to the 2G-SGSN, so the 2G-SGSN knows that the 3G-SGSN can accept the relevant data packet of the activated PDP context.vii.The 2G-SGSN copies and caches N-PDUs, and it starts to send data packet to the 3G-SGSN. Before the timer times out, the extra N-PDUs received from GGSN will be copied and sent to 3G-SGSN. After the timer times out, no N-PDUs will be sent to 3G-SGSN.viii.The 3G-SGSN sends the UPDATE PDP CONTEXT REQUEST message to each GGSN related. Each GGSN updates its PDP context and responses the UPDATE PDP CONTEXT RESPONSE message.ix.The 3G-SGSN notices HLR that the SGSN has changed by sending the UPDATE GPRS LOCATION message.x.The HLR sends the CANCEL LOCATION message to the old 2G-SGSN. After the 2G-SGSN timer times out, the old 2G- SGSN will delete MM context and PDP context. The 2G-SGSN responds by sending the CANCEL LOCATION ACK message.xi.The HLR sends the INSERT SUBSCRIBER DATA message to the 3G-SGSN. The 3G-SGSN builds up MM context and replies the INSERT SUBSCRIBER DATA ACK message to the HLR.xii.The HLR confirms that the modification is completed, and responds to the 3G-SGSN through the UPDATE GPRS LOCATION message by returning an UPDATE GPRS LOCATION ACK.xiii.If the association is to be built up, and the joint RA/LA update attached by IUEI is specified for Update Type, or the LA changes in the routing area update, the new SGSN will sends the LOCATION UPDATE REQUEST message to the VLR, and notices the new VLR to initiate location update, the VLR creates or updates association by saving SGSN number.xiv.If the user data identifier in the VLR is not confirmed by the HLR, the VLR will notice the HLR. The HLR cancels the old VLR and inserts user data to the new VLR.a)The new VLR sends Update Location to the HLR.b)The HLR cancels the old data in the VLR by sending the CANCEL LOCATION message to the old VLR.c)The old VLR responds through the CANCEL LOCATION message.d)The HLR sends the INSERT SUBSCRIBER DATA ACK to the new VLR.e)The new VLR responds through the INSERT SUBSCRIBER DATA ACK message.f)The HLR responds to the new VLR through the UPDATE LOCATION ACK message.xv.The new VLR assigns a new TUEI and notices the 3G-SGSN through the LOCATION UPDATE ACCEPT message. xvi.The 3G-SGSN verifies the UE in the new routing area, if all the checks are passed, the 3G-SGSN builds up the MM context and PDP context of the user. The 3G-SGSN sends the ROUTING AREA UPDATE ACCEPT message to the UE.xvii.The UE confirms the new assigned PTMSI by sending the ROUTING AREA UPDATE COMPLETE message. xviii.If the confirmation is obtained from the UE, the 3G-SGSN sends the TMSI REALLOCATION COMPLETE message to the new VLR.xix.If the UE has uplink data or signaling, it will send the SERVICE REQUEST message to the SGSN. The requested service will be specified in Service Type (data or signaling)xx.If the UE has sent the service request, the 3G-SGSN sends the RAB ASSIGNMENT REQUEST message to request SRNS to build a radio access bearer. The SRNS sends the RADIO BEARER SETUP REQUEST message to the UE. The UE responds through the RADIO BEARER SETUP COMPLETE message. The SRNS sends the RAB ASSIGNMENT RESPONSE message to the SGSN. The SRNS sends N-PDUs to the UE.2G/3G Interoperability Parameters2G/3G Interconnection Parameters1.Parameters Provided to 3G by 2GThe radio parameters provided to 3G by 2G include the country code (MCC), network code (MNC), location area code (LAC), cell ID (CI), network color code (NCC), base station color code (BCC), band indication (900 or 1800) and BCCH. Table 31 shows an example of parameters for 2G, and all the parameters are decimal in the example.Table 31 Parameters Provided to 3G by 2GMCCMNCLACCINCCBCCBand IndicationBCCH

4602220090010

2.Parameters Provided to 2G by 3GThe radio parameters provided to 2G by 3G include country code (MCC), network code (MNC), location area code (LAC), RNC ID (RNC ID), cell ID (C_ID), downlink frequency point, primary scrambling code, and frequency bandwidth. Table 32 shows an example of parameters for 3G, and all the parameters are decimal in the example.Table 32 Parameters Provided to 2G by 3GMCCMNCLACRNC IDC_IDDownlink ARFCNPrimary Scrambling CodeFrequency Bandwidth

46022011501106871265

Typical Selection and Reselection ParametersThe reselection parameters from WCDMA to GSM/GPRS are delivered in the SIB3 and SIB11 WCDMA messages. The content of the current cell is delivered in the SIB3 message, and the content of the neighbor cells is delivered in the SIB11 message.Table 33 Key 2G->3G Cell Reselection ParametersFDD_QoffsetFDD Reselection Offset0 ()

FDD_QminMinimum value of Ec/No of UTRAN reselection cell7(12 dB)

Qsearch_IThreshold for UE to start UTRAN cell reselection measurement7 (always)

Table 34 Key 3G->2G Cell Reselection ParametersParameterDescriptionBaseline Value

QqualminLowest access quality of 3G cell signal18 dB

QRxLevMinLowest access strength of 3G cell signal115 dBm

SSearchRatInter-RAT measurement trigger threshold for cell reselection6 dB

QHyst1SReselection delay of serving cell 110 dB

Qoffset1SNSib11Quality offset 1 of serving and neighbor cells in SIB1110 dB

Qoffset1SNSib12Quality offset 2 of serving and neighbor cells in SIB120 dB

TreselectionTime duration of cell reselection timer1 s

Key 2G->3G Reselection ParametersFDD_QoffsetDescriptionIf a UTRAN neighbor cell has been switched on (a 3G cell itself should meet certain conditions) and it satisfies the demand of starting measurement that is set in the cell, a UE can reselect the UTRAN neighbor cell after it meets the three conditions below:The RSCP (received signal code power) of the neighbor cell is higher than the RLA_C.The RSCP of the neighbor cell is higher than the RLA_Cs of all the GSM neighbor cells by at least FDD_Qoffset (FDD reselection offset), and it lasts at least 5 seconds (if it reselected a GSM cell 15 seconds ago, the FDD_Qoffset still needs 5 dB increment).The Ec/No of the neighbor cell is higher than or equal to the FDD_Qmin set in the cell (the minimum Ec/No of the UTRAN reselection cell).If there are more than one UTRAN cells that can meet the conditions above, the cell with the highest RSCP is selected.Impact on the network performanceThis parameter is set to 8, which shows that the signal offset between GSM and 3G is 0. However, the 3G system is usually in the 2G band, and the propagation loss is large. It is better to set to 0 according to the actual experience, which means that the impact of the 3G signal is not taken into account in the reselection process from GSM to 3G, in order to improve the reselection success rate from 2G to 3G.Parameter configuration (iBSC V6.20.614C)OMC GERAN Subnet User ID BSC Management NE User ID Configuration Set ID BSC Global Resource ID BS Configuration BS ID Cell ID UTRAN Cell Control Basic Attribute 1FDD_QminDescriptionWhen it reselects the UTRAN neighbor cell, it requires that the value of Ec/No is not less than the value of the cell.Impact on the network performanceIt is a key 2G->3G reselection parameter and the recommended value is 7(-12 dB) for network optimization. The difference of the reselection judgment thresholds between the WCDMA and GSM/GPRS systems should be at least 4 dB, such as the SsearchRAT parameter for WCDMA and the FDD_Qmin parameter for GSM/GPRS. It is set to 7 in order to improve the reselection success rate from 2G to 3G.Parameter configuration (iBSC V6.20.614C)OMC GERAN Subnet User ID BSC Management NE User ID Configuration Set ID BSC Global Resource ID BS Configuration BS ID Cell ID UTRAN Cell Control Basic Attribute 1Qsearch_IDescriptionWhen the RLA_C of the cell is lower (0~6) or higher (8~14) than the threshold, a UE starts the measurement of the UTRAN reselection cells. 7 refers to always and 15 refers to never.Impact on the network performanceFor the Qsearch_I parameter, the UE measures the inter-RAT cells all the time after it enters the cell that is expected for interoperability. As long as the 3G system signal condition is satisfied for residence, it will reselect the system.If the system is requested to support the GSM->3G reselection, it is recommended to set to 7 for a cell with inter-RAT neighbor cells, in order to improve the reselection success rate from 2G to 3G. It is set to 15 for closing the measurement. Parameter configuration (iBSC V6.20.614C)OMC GERAN Subnet User ID BSC Management NE User ID Configuration Set ID BSC Global Resource ID BS Configuration BS ID Cell ID UTRAN Cell Control Basic Attribute 1Key 3G->2G Reselection ParametersQqualminDescriptionThis parameter shows the minimum level of quality demand for selection and reselection which is satisfied by a cell. When it is CPICH Ec/No for measurement, as long as the quality value of the measured cell is bigger than the Qqualmin, it can satisfy the condition of cell selection. The default value is -18 dB. Table 35 Qqualmin DescriptionWireless Parameter Name

Full NameQqualmin(dB)

AbbreviationQQualMin

DescriptionThis parameter shows the minimum level of quality demand for selection and reselection which is satisfied by a cell. When it is CPICH Ec/No for measurement, as long as the quality value of the measured cell is bigger than the Qqualmin, it can satisfy the condition of cell selection. The default value is -18 dB.

Value Range and Stepsize[-24, 0] dB; Step 1 dB

UnitdB

Default Value (Remarks)-18 dB

Impact on the network performanceIf the value of this parameter increases, the condition of cell selection is difficult to be satisfied; if the value of this parameter decreases, the condition of cell selection is easy to be satisfied. However, it is likely that a UE cannot receive the system message borne by the PCCPCH correctly after it resides in the cell. Parameter configuration Log on the OMC-R and set in the path below.Interface Path: view Configuration Management RNC NE RNC Radio Resource Management Utran cell Utran cell xx Modify Advanced Parameter SCCPCHSsearchRATDescriptionThis parameter shows the trigger threshold Ssearch,RAT of inter-RAT measurement for reselection. The UE is used to determine whether to carry out the inter-RAT measurement. When the HCS is not used, if the quality of the serving cell is higher than the Ssearch,RAT , the inter-RAT measurement will not be performed, if the quality of the serving cell is not higher than the Ssearch,RAT or the Ssearch,RAT is not configured, the inter-RAT measurement will be performed. For details, refer to TS 25.304.Table 36 SsearchRAT DescriptionWireless Parameter Name

Full NameSsearch, RAT(dB)

AbbreviationSSearchRat

DescriptionThis parameter shows the trigger threshold Ssearch, RAT of inter-RAT measurement for reselection. The UE is used to determine whether to carry out the inter-RAT measurement. When the HCS is not used, if the quality of the serving cell is higher than the Ssearch, RAT, the inter-RAT measurement will not be performed, if the quality of the serving cell is not higher than the Ssearch, RAT or the Ssearch, RAT is not configured, the inter-RAT measurement will be performed. For details, refer to TS 25.304.

Value Range and Stepsize[0, 20] dB; Step 2 dB

UnitdB

Default Value (Remarks)6 dB

Impact on the network performanceThis parameter works as the trigger threshold of inter-RAT measurement in the selection and reselection processes for the HCS cell. The factors that should be taken into account for parameter configuration include: cell residence and UE battery consumption.The higher the parameter is, the easier the inter-RAT measurement is triggered and the more the UE battery consumes. The smaller the parameter is, the more difficult the inter-RAT measurement is triggered; and it cannot reside in the cell with good quality in time, which causes call loss easily. Parameter configuration Log on the OMC-R and set in the path below.Interface Path: View Configuration Management RNC NE RNC Radio Resource Management Advanced Parameter Manage ueCnst Waiting Time for Receiving "In Sync" from L1 in Connected Mode (T312 in Connected Mode)QRxLevMinDescriptionThis parameter shows the minimum threshold of received level for selection and reselection which is satisfied by a cell. When it is CPICH RSCP for measurement, the quality value of the measured cell is bigger than the Qrxlevmin, which can just satisfy the condition of cell selection.Table 37 QRxLevMin DescriptionWireless Parameter Name

Full NameQrxlevmin(dBm)

AbbreviationQRxLevMin

DescriptionThis parameter shows the minimum threshold of received level for selection and reselection which is satisfied by a cell. When it is CPICH RSCP for measurement, the quality value of the measured cell is bigger than the Qrxlevmin, which can just satisfy the condition of cell selection.

Value Range and Stepsize[-115,-25] dBm step 2dBm

UnitdBm

Default Value (Remarks)-115 dBm

Impact on the network performanceThe higher this parameter is, the more difficult UE resides in the cell, which leads to be off the network. The lower this parameter is, the easier it is to reside, but it may lead to that a UE cannot receive the system message borne by PCCPCH correctly after it resides in the cell.Adjustment recommendation: it is not adjusted generally, and it is not recommended to be adjusted. Parameter configuration Log on the OMC-R and set in the path below.OMC path: View Configuration Management RNC NE RNC Radio Resource Management UltranCell UltranCellXXX Modify Advanced Parameter UTRAN Cell Indicator of Cell Re-establishment when OCNS Codes ChangedQHyst1SDescriptionThis parameter shows the delay parameter of FDD cell reselection for judgment when the measurement value is CPICH RSCP or Cpich EcNo. In the rule of value R ordering for reselection, the R value of serving cell is equal to the measurement value and reselection delay. When the measurement value is Cpich RSCP, calculate and order the R values according to the Qhyst1s. When the measurement value is Cpich EcNo, first calculate and order the R values according to the Qhyst1s, the UTRAN cell ranks at the top, then calculate and order the R values according to the signal quality of Cpich EcNo. Table 38 QHyst1S DescriptionWireless Parameter Name

Full NameQhyst1s(dB)

AbbreviationQHyst1S

DescriptionThis parameter shows the delay parameter of FDD cell reselection for judgment when the measurement value is CPICH RSCP or Cpich EcNo. In the rule of value R ordering for reselection, the R value of serving cell is equal to the measurement value and reselection delay. When the measurement value is Cpich RSCP, calculate and order the R values according to the Qhyst1s. When the measurement value is Cpich EcNo, first calculate and order the R values according to the Qhyst1s, the UTRAN cell ranks at the top, then calculate and order the R values according to the signal quality of Cpich EcNo.

Value Range and Stepsize[0, 40] dB; Step2 dB

UnitdB


Impact on the network performanceThe higher this parameter is, the more difficult the reselection is triggered, and the less sensitive it is relatively for the signal variation. The lower this parameter is, the easier the reselection is triggered, and the more ping-pong reselections occur, which increase the signaling load. Adjustment recommendation: It can be set to be higher properly for the scenario where the signal changes fast. Parameter configuration Log on the OMC-R and set in the path below.Interface Path: view Configuration Management RNC NE RNC Radio Resource Management Utran cell Utran cell xx Modify Advanced Parameter PICHQoffset1s,n in SIB11(dB)DescriptionThis parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH RSCP. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB11. The R value of the neighbor cell is equal to be the measured signal quality of the neighbor cell subtracting this offset. Note:For idle or connected mode, when the SIB12 is not broadcast, it is equal to the value of Qoffset1SNSib11 when the reselection measurement value is RSCP; for connected mode, when the SIB12 is broadcast, it is equal to the value of Qoffset1SNSib12 when the reselection measurement value is RSCP.Table 39 Qoffset1s,n in SIB11(dB) DescriptionWireless Parameter Name

Full NameQoffset1s,n in SIB11(dB)

AbbreviationQoffset1SNSib11

DescriptionThis parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH RSCP. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB11.

Value Range and StepsizeOMCR: [-50, 50] dB;

UnitdB


Impact on the network performanceThe factors that should be taken into account for configuring this parameter include the degree of difficulty for reselection and the tendentiousness of reselection.The lower this parameter is, the easier it reselects this neighbor cell. The higher this parameter is, the more difficult it reselects this neighbor cell. It can be set to be different values for different GSM neighbor cells, in order to control the tendentiousness of reselection for different GSM neighbor cells. Adjustment recommendation:For a co-frequency neighbor cell, adjust the value of this parameter in order to reselect cell when the neighbor cell is better than the source cell. For a different-frequency or inter-RAT neighbor cell, it is configured according to the service planning of the multi-carrier networking. Parameter configuration Log on the OMC-R and set in the path below.Interface Path: View Configuration Management RNC NE RNC Radio Resource Management UltranCell UltranCellXXX Neighboring Cell Advanced Parameter Manager Qoffset1s,n in SIB11(dB)Qoffset1s,n in SIB12(dB)DescriptionThis parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH RSCP. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB12. Note:For idle or connected mode, when the SIB12 is not broadcast, it is equal to the value of Qoffset1SNSib11 when the reselection measurement value is RSCP; for connected mode, when the SIB12 is broadcast, it is equal to the value of Qoffset1SNSib12 when the reselection measurement value is RSCP.Table 310 Qoffset1s,nin SIB12(dB) DescriptionWireless Parameter Name



DescriptionThis parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH RSCP. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB12.

Value Range and StepsizeOMCR: [-50, 50]dB

UnitdB


Impact on the network performanceThe factors that should be taken into account for configuring this parameter include the degree of difficulty for reselection and the tendentiousness of reselection.The lower this parameter is, the easier it reselects this neighbor cell. The higher this parameter is, the more difficult it reselects this neighbor cell. It can be different values for different UMTS neighbor cells, in order to control the tendentiousness of reselection for different UMTS neighbor cells.Adjustment recommendation:Generally the SIB12 is not used, it is not recommended to adjust this parameter.Parameter configuration Log on the OMC-R and set in the path below.Interface Path: View -> Configuration Management -> RNC NE -> RNC Radio Resource Management -> UltranCell -> UltranCellXXX -> Neighboring Cell -> Advanced Parameter Manager -> Qoffset1s,n in SIB12(dB)TreselectionDescriptionThis parameter shows the timer duration of reselection. To be a serving cell, a new cell must be the best cell according to the ordering R principle, and it lasts for Treselections, which can be selected the new serving cell. Table 311 Treselection DescriptionWireless Parameter Name

Full NameTreselection(s)

AbbreviationTReselection

DescriptionThis parameter shows the timer duration of reselection. To be a serving cell, a new cell must be the best cell according to the ordering R principle, and it lasts for Treselections, which can be selected the new serving cell.

Value Range and Stepsize[0, 31]s; step 1s

UnitS

Default Value (Remarks)1s

Impact on the network performanceThe factors that should be taken into account for configuring this parameter include the signal quality variation and ping-pong reselection. This parameter is used to avoid the ping-pong reselection. If it is set to be too lower, the ping-pong reselection is easy to occur. If it is set to be too higher, the reselection is slower, which may lead to call loss. Adjustment recommendation: In the scenario of high-speed railway or highway, it is set to be lower in order to speed up the reselection speed and improve the call success rate. Parameter configuration Log on the OMC-R and set in the path below.Interface Path: View Configuration Management RNC NE RNC Radio Resource Management Advanced Parameter Manage ueCnst Waiting Time for Completion of Cell Update When Radio Link Fails and Radio Bearer(s) Associated with T315 Exist (T315)Qhyst2s(dB)DescriptionThis parameter shows the delay parameter of FDD cell reselection for judgment when the measurement value is CPICH Ec/No. In the rule of value R ordering for reselection, the R value of serving cell is equal to the measurement value and reselection delay. Refer to TS 25.304 for details.Table 312 Qhyst2s(dB) DescriptionWireless Parameter Name

Full NameQhyst2s(dB)

AbbreviationQHyst2S

DescriptionThis parameter shows the delay parameter of FDD cell reselection for judgment when the measurement value is CPICH Ec/No. In the rule of value R ordering for reselection, the R value of serving cell is equal to the measurement value and reselection delay. Refer to TS 25.304 for details.

Value Range and Stepsize[0, 40] dB; Step 2 dB

UnitdB


Impact on the network performanceThe factors that should be taken into account for configuring this parameter include the signal variation and ping-pong reselection. The higher this parameter is, the more difficult the reselection is triggered, and the less sensitive it is relatively for the signal variation. The lower this parameter is, the easier the reselection is triggered, and the more ping-pong reselections occur, which increase the signaling load. Adjustment recommendation: it can be set to be higher properly for the scenario where the signal varies very fast. Parameter configuration Log on the OMC-R and set in the path below.Interface Path: View -> Configuration Management -> RNC NE -> RNC Radio Resource Management -> RCP Scrambling Code Configuration Information -> Ending No. of RCP Scrambling CodeQoffset2s,n in SIB11(dB)DescriptionThis parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH Ec/No. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB11. The R value of the neighbor cell is equal to be the measured signal quality of the neighbor cell subtracting this offset. Table 313 Qoffset2s,n in SIB11(dB) DescriptionWireless Parameter Name



DescriptionThis parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH Ec/No. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB11. The R value of the neighbor cell is equal to be the measured signal quality of the neighbor cell subtracting this offset.

Value Range and StepsizeOMCR: [-50, 50] dB;

UnitdB


Impact on the network performanceThe factors that should be taken into account for configuring this parameter include the degree of difficulty for reselection and the tendentiousness of reselection.The lower this parameter is, the easier it reselects this neighbor cell. The higher this parameter is, the more difficult it reselects this neighbor cell. It can be set to be different values for different UMTS neighbor cells, in order to control the tendentiousness of reselection for different UMTS neighbor cells. Adjustment recommendation:For a co-frequency neighbor cell, adjust the value of this parameter in order to reselect cell when the neighbor cell is better than the source cell. For a different-frequency or inter-RAT neighbor cell, it is configured according to the service planning of the multi-carrier networking. Parameter configuration Log on the OMC-R and set in the path below.Interface Path: View -> Configuration Management -> RNC NE -> RNC Radio Resource Management -> UltranCell -> UltranCellXXX -> Neighboring Cell -> Advanced Parameter Manager -> Qoffset2s,n in SIB11(dB)Qoffset2s,n in SIB12(dB)DescriptionThis parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH Ec/No. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB12.Table 314 Qoffset2s,n in SIB12(dB) DescriptionWireless Parameter Name



DescriptionThis parameter shows the quality offset of serving and neighbor cells when the measurement value is CPICH Ec/No. It is used for cell ordering in the reselection rule. This parameter is broadcast to UE in the SIB12.

Value Range and StepsizeOMCR: [-50, 50] dB;RNC: D=P+50, [0, 100]

UnitdB


Impact on the network performanceThe factors that should be taken into account for configuring this parameter include the degree of difficulty for reselection and the tendentiousness of reselection.The lower this parameter is, the easier it reselects this neighbor cell. The higher this parameter is, the more difficult it reselects this neighbor cell. It can be set to be different values for different UMTS neighbor cells, in order to control the tendentiousness of reselection for different UMTS neighbor cells.Adjustment recommendation:Generally the SIB12 is not used, it is not recommended to adjust this parameter.Parameter configuration Log on the OMC-R and set in the path below.Interface Path: View -> Configuration Management -> RNC NE -> RNC Radio Resource Management -> UltranCell -> UltranCellXXX -> Neighboring Cell -> Advanced Parameter Manager -> Qoffset2s,n in SIB12(dB)Recommended Values of Key Reselection Parameters1.3G->2G ReselectionTable 315 Recommended Values of Key 3G ->2G Reselection ParametersParameterDescriptionBaseline ValueValue of Unicom

QqualminLowest access quality of 3G cell signal-18 dB-18 dB

QRxLevMinLowest access strength of 3G cell signal-115 dBm-115 dBm

SSearchRatinter-RAT measurement trigger threshold for cell reselection6 dB4dB

QHyst1SReselection delay of serving cell 110 dB10 dB

Qoffset1SNSib11Quality offset 1 of serving and neighbor cells in SIB1110 dB0 dB

Qoffset1SNSib12Quality offset 2 of serving and neighbor cells in SIB120 dB0 dB

TreselectionTime duration of cell reselection timer1 s1 s

Note:The values of Unicom are different according to the different requirements from each city. The values above are only for reference, the values for each project depend on the actual. 2.2G->3G ReselectionTable 316 Key 2G ->3G Reselection ParametersFDD_QoffsetFDD Reselection Offset0 ()

FDD_QminMinimum value of Ec/No of UTRAN reselection cell7(-12 dB)

Qsearch_IThreshold for UE to start UTRAN cell reselection measurement7 (always)

Note:It shows - when the FDD_Qoffset is set to 0. The reason for setting it to be 0 is that UE does not need to consider the strength comparison between 2G and 3G. If it requires the UE to select 3G as far as possible in the field, this parameter can be set to 0.It is only reference for 2G parameters, which should be set according to the demands of each project. Typical Inter-RAT Handover Parameters The key handover control parameters from WCDMA to 2G are mainly determined by the parameters that trigger the 2D, 2F and 3A events. The lower the trigger thresholds of 2D and 3A are, the more traffic stays in the 3G network. But the lower the two parameters are, the worse 3G signal there is for handover and the easier the call drops occur. The 2D and 3A parameters are set to be higher, thus the service can be switched to 2G cell before the WCDMA signal gets worse, in order to decrease the call drop rate. Through the test results, in order to avoid the call drop in the edge of 3G network, it should start the inter-RAT measurement in the condition of a better 3G signal, which means that the 2D event trigger level should be too lower for the circuit domain service in the different system. However, the thresholds of 2D and 3A cannot be too higher, or it will lead to that a large number of 3G subscribers switch to the 2G cells and the GSM traffic increases. These key parameters are described below. 2D/2F Event ThresholdDescriptionThis parameter shows the absolute threshold configured for 2D/2F event (used for judging the quality of the carrier frequency being used).Table 317 2D/2F Event Configured ThresholdWireless Parameter Name

Full NameAbsolute threshold configured for 2D/2F event (used for judging the quality of the carrier frequency being used).

AbbreviationThreshUsedFreq[MAX_INTER_MEAS_EVENT]

DescriptionThis parameter shows the absolute threshold configured for 2D/2F event (used for judging the quality of the carrier frequency being used). The MAX_INTER_MEAS_EVENT is the maximum number of inter-frequency measurement event, and the value is 6.

Value Range and StepsizeCPICH RSCP: [-115,-25] dBm;CPICH Ec/No: [-24,0] dBPathloss: [30,165] dB

UnitdBm /dB

Default Value (Remarks)Reported parameter of UE periodical measurement when the measurement value is CPICH Ec/No: -Reported parameter of UE inter-frequency event when the measurement value is CPICH Ec/No: [-13, -5]dBReported parameter of UE periodical measurement when the measurement value is CPICH RSCP: -Reported parameter of UE inter-frequency event when the measurement value is CPICH RSCP: [-95, -80] dBm

Impact on the network performanceThe 2D and 2F events are the switch of the compact model. The lower the 2D threshold is, the more difficult the 2D is triggered. The lower the 2F threshold is, the easier the 2F is triggered. As the requested signal quality and inter-RAT handover policies are different according to different service types, so the inter-RAT measurement thresholds are divided into CS and PS signaling. When a cell is in the center of carrier frequency coverage, it will use the Ec/No measurement value as the criterion of the 2D and 2F events. Therefore, if the compact model is expected to start as early as possible, set the 2D event threshold to be higher, otherwise set it to be lower. If the ping-pong handover is expected to decrease in the start and stop processes of the compact model, it can increase the difference between the 2D and 2F thresholds. The easier the event is triggered, the more number of average handover time there is, which increases the handover success rate, but consumes the system resources. Note:It can choose Ec/Io or RSCP as the trigger threshold of each event, according to the actual situation. At the edge of the cell coverage, the system is usually limited for the uplink loss, which triggers the inter-RAT handover caused by coverage. The range of Ec/Io is relatively smaller, which is not suitable for the handover caused by coverage as it varies very fast, so it is recommended to adopt the RSCP. For the center of the cell coverage, there is more interference and the system is usually limited for the downlink interference, which triggers the inter-RAT handover. Therefore, the Ec/Io can better reflect the interference degree of the system. Currently it adopts RSCP for the trigger threshold of each event. Parameter configurationLog on the OMC-R and set in the path below.Interface Path: View->Configuration Management->RNC NE->RNC Radio Resource Management->Modify Advanced Parameter->UE Inter-frequency Measurement Configuration-> Absolute Threshold of the Quality of the Currently Used Frequency for 2B/2D/2F3A/3C Event ThresholdDescriptionThis parameter shows the absolute threshold value for judging the quality of other system, which is configured for 3A/3C event. The value range and unit of this parameter are related to the measurement value of other system cell, which is only for the GSM Carrier RSSI of GSM system now, corresponding to the CPICH RSCP of local system. Therefore, the value range and unit of this parameter correspond to the CPICH RSCP.Table 318 3A/3C Threshold ParameterWireless Parameter Name

Full NameAbsolute threshold value for judging the quality of other system, which is configured for 3A/3C event

AbbreviationThreshSys[MAX_RAT_MEAS_EVENT]

DescriptionThis parameter shows the absolute threshold value for judging the quality of other system, which is configured for 3A/3C event. The value range and unit of this parameter are related to the measurement value of other system cell, which is only for the GSM Carrier RSSI of GSM system now, corresponding to the CPICH RSCP of local system. Therefore, the value range and unit of this parameter correspond to the CPICH RSCP. MAX_RAT_MEAS_EVENT is the maximum number of inter-RAT measurement event, and the value is 4.

Value Range and StepsizeCPICH RSCP: [-115,-25]dBm step 1dBmCPICH Ec/No: [-24,0] dB step 1dB

UnitdBm /dB

Default Value (Remarks)Periodically-reported parameter when the measurement value is CPICH Ec/No of local system: -Reported parameter by UE event when the measurement value is CPICH Ec/No of local system: [-6, -24]Periodically-reported parameter when the measurement value is CPICH RSCP of local system: -Reported parameter by UE event when the measurement value is CPICH RSCP of local system: [-95, -115]

Impact on the network performanceThe factors that should be taken into account for configuration include the compression moulding start time, the average handover times, and the handover success rate. For the 3A/3C, the lower it is, the more difficult it is triggered, or the higher it is, the easier it is triggered. For the 3B, the higher it is, the more difficult it is triggered, or the lower it is, the easier it is triggered.Adjustment recommendation: i.In order to avoid the capacity loss caused by starting compression moulding, as long as the compression moulding of inter-RAT measurement is enabled by 2D event trigger, it is expected to switch to the 2G system as soon as possible, so the 2G system threshold should not be higher. ii.If the quality of inter-RAT neighbor cell is also poor, the service switches rashly. There is a high rate of call drop, and the service quality cannot be guaranteed after handover. So this threshold cannot be set to be lower, in order to guarantee the service to be normal. Note:According to the current 3G strategy, let the 3G subscribers enjo

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