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1 Introduction to This Document 1.1 Scope This document describes the 2G/3G interoperability feature of Huawei GBSS. It covers the functions of and technologies related to this feature, including measurement of neighboring 3G cells, inter-RAT cell reselection, and inter-RAT handover.
1.2 Intended Audience It is assumed that users of this document are familiar with GSM basics and have a working knowledge of GSM telecommunication.
This document is intended for:
Personnel working on Huawei GSM products or systems System operators who need a general understanding of this feature
1.3 Change History The change history provides information on the changes on the 2G/3G interoperability (TDD) feature in different document versions.
There are two types of changes, which are defined as follows:
Feature change Feature change refers to the change in the 2G/3G interoperability (TDD) feature of a specific product version.
Editorial change Editorial change refers to the change in wording or the addition of the information that was not described in the earlier version.
Document Issues The document issues are as follows:
02 (2009-09-30) 01 (2009-06-30)
02(2009-09-30) This is the second commercial release of GBSS9.0.
Compared with issue 01 (2009-06-30) of GBSS9.0, issue 02 (2009-09-30) of GBSS9.0 incorporates the changes described in the following table.
2 Overview The UMTS network and the GSM network will coexist and provide services together for a long time. To facilitate the service provision by both the networks, Huawei introduces 2G/3G interoperability into the BSS, which consists of two functions: inter-RAT handover and inter-RAT cell reselection between GSM and UMTS.
Through 2G/3G interoperability, a smooth evolution from GSM to UMTS can be achieved, thus saving the investment. For the operator that has both the UMTS network and the GSM network, 2G/3G interoperability enables the GSM network and the UMTS network to complement each other, thus expanding the network coverage and improving the service quality. For example, when a dual-mode MS moves to an area without UMTS coverage, it can reselect or be handed over to a GSM cell through 2G/3G interoperability. The continous coverage brought by this feature improves the user experience.
For the areas covered by both the GSM network and the UMTS network, 2G/3G interoperability can be performed to achieve traffic balance between the GSM system and the UMTS system. For example, when the traffic load in a GSM cell is too heavy, 2G/3G interoperability can be performed to hand over some calls from the GSM cell to a UMTS cell.
With 2G/3G interoperability, the access policy for the GSM network can be different from that for the UMTS network in the areas covered by both the GSM network and the UMTS network. For example, the GSM network can be preferentially selected by CS services and the UMTS network can be preferentially selected by PS services. In this way, the advantages of both networks can be achieved.
All the MSs involved in this feature are dual-mode MSs.
3 Technical Description 3.1 Measurement of Neighboring UMTS Cells The system information contains the neighboring UMTS cell list and UMTS cell reselection parameters, based on which the MS measures the neighboring cell information and performs cell reselection and handover. The system information refers to System Information 2ter, System Information 2Quater, and Measurement Information. System Information 2ter and System Information 2Quater are sent on the BCCH, and Measurement Information is sent on the SACCH. The parameter Support Sent 2QUATER controls whether System Information 2Quater should be sent.
The MSs in a GSM cell measure the information of both neighboring GSM cells and neighboring UMTS cells. To reduce unnecessary measurements and save power consumption of MSs, the BSS controls the neighboring cell measurement of MSs through parameters. The MSs in idle mode or packet transfer mode can perform inter-RAT cell reselection. The MSs in dedicated mode can perform inter-RAT handover. Operators can set measurement parameters to different values for the MSs in different states.
The MSs in idle mode determine whether to measure the information of neighboring UMTS cells according to Qsearch I and the receive level of the serving cell. The conditions for triggering the measurement differ with the value of Qsearch I.
If the value of Qsearch I ranges from 0 to 6, the measurement is triggered when the receive level of the serving cell is lower than the value of Qsearch I.
If the value of Qsearch I ranges from 8 to 14, the measurement is triggered when the receive level of the serving cell is higher than the value of Qsearch I.
If the value of Qsearch I is 7, the MSs always measure the neighboring UMTS cell information regardless of the receive level of the serving cell.
If the value of Qsearch I is 15, the MSs never measure the neighboring UMTS cell information regardless of the receive level of the serving cell.
The MSs in packet transfer mode determine whether to measure the information of neighboring UMTS cells according to Qsearch P and the receive level of the serving cell. The conditions for triggering the measurement differ with the value of Qsearch P.
If the value of Qsearch P ranges from 0 to 6, the measurement is triggered when the receive level of the serving cell is lower than the value of Qsearch P.
If the value of Qsearch P ranges from 8 to 14, the measurement is triggered when the receive level of the serving cell is higher than the value of Qsearch P.
If the value of Qsearch P is 7, the MSs always measure the neighboring UMTS cell information regardless of the receive level of the serving cell.
If the value of Qsearch P is 15, the MSs never measure the neighboring UMTS cell information regardless of the receive level of the serving cell.
The MSs in dedicated mode determine whether to measure the information of neighboring UMTS cells according to Qsearch C and the receive level of the serving cell. The conditions for triggering the measurement differ with the value of Qsearch C.
If the value of Qsearch C is between 0 and 6, the measurement is triggered when the receive level of the serving cell is lower than the value of Qsearch C.
If the value of Qsearch C is between 8 and 14, the measurement is triggered when the receive level of the serving cell is higher than the value of Qsearch C.
If the value of Qsearch C is 7, the MSs always measure the neighboring UMTS cell information regardless of the receive level of the serving cell.
If the value of Qsearch C is 15, the MSs never measure the neighboring UMTS cell information regardless of the receive level of the serving cell.
Qsearch C is contained in the Measurement Information. After entering the dedicated mode, MSs try to obtain the Qsearch C from the Measurement Information transmitted on the SACCH. Before Qsearch C is obtained, MSs take the value of Qsearch C Initial that is transmitted on the BCCH as the value of Qsearch C.
3.2 2G/3G Inter-RAT Cell Reselection 2G/3G inter-RAT cell reselection involves the cell reselection from GSM to UMTS and the cell reselection from UMTS to GSM. Cell reselection is performed mainly by the MS.
For MSs in idle mode, cell reselection is mainly performed to implement 2G/3G interoperability. A dual-mode MS camping on a GSM cell can reselect a UMTS cell. It measures the information of the neighboring UMTS cell, and then decides whether to reselect the UMTS cell according to cell reselection parameters.
For MSs in packet transfer mode, they can reselect a UMTS cell for data services through autonomous cell reselection, Network Assisted Cell Change (NACC), or Network Control Mode 2 (NC2). The cell reselection procedure in packet transfer mode is the same as that in idle mode. The autonomous cell reselection is performed by the MS without the intervention of the network. In NACC and NC2, the network affects the cell reselection through signaling so that the MS will camp on the desired cell.
The parameter Inter-RAT Cell Reselection Enable determines whether cell reselection between GSM and UMTS is enabled. When Inter-RAT Cell Reselection Enable is set to No, the BSS does not send the neighboring UMTS cell list and the parameters related to 2G/3G inter-RAT cell reselection. In this way, MSs in a GSM cell cannot select a UMTS cell.
3.2.1 Inter-RAT Cell Reselection from UMTS to GSM When an MS moves into the GSM coverage area and reselects a GSM cell, the MS initiates the location update in the GSM network. The GSM network handles the location update regardless of whether the MS is from a UMTS cell or a GSM cell.
For the BSS, the cell reselection procedure from UMTS to GSM is the same as that between GSM cells. Thus, it is not repeated in this document.
3.2.2 Inter-RAT Cell Reselection from GSM to UMTS The MSs in a GSM cell obtain the neighboring UMTS cell list and cell reselection parameters through System Information 2ter and System Information 2Quater, and then measure the neighboring UMTS cells according to the list and parameters. When the MS is in idle mode or packet transfer mode, the mechanism of cell reselection from the GSM cell to the UMTS cell is the same as that between GSM cells. The GSM network controls the cell reselection from the GSM cell to the UMTS cell through TDD Cell Reselect Diversity.
TDD Cell Reselect Diversity indicates the signal strength difference between the candidate UMTS cells and the serving GSM cell. This parameter is a key factor for controlling the cell reselection from the GSM cell to the UMTS cell.
When TDD Cell Reselect Diversity is set to a small value, the cell reselection condition is easy to meet. In this case, the number of MSs that camp on the GSM cell is reduced. When TDD Cell Reselect Diversity is set to a great value, the cell reselection condition is difficult to meet. In this case, the number of MSs that camp on the GSM cell is increased.
For the UMTS TDD cell, the measurement quantity to be used is Received Signal Code Power (RSCP) of the Common Pilot Channel (CPICH). If the measurement result meets the following condition within
five seconds, the MS initiates the cell reselection from GSM to UMTS. If there is more than one UMTS cell that meets the condition, the MS selects a cell with the highest RSCP as the target cell.
CPICH RSCP > RLA_C + TDD Cell Reselect Diversity
In the preceding condition, RLA_C refers to the average receive level. The RSCP of the neighboring UMTS cell must be greater than the sum of the value of TDD Cell Reselect Diversity and the average receive level of the serving cell. In addition, the RSCP of the neighboring UMTS cell must be greater than the sum of the value of TDD Cell Reselect Diversity and the receive level of each GSM neighboring cell.
The inter-RAT cell reselection from GSM to UMTS cannot be triggered within 5s after the cell reselection from UMTS to GSM. If the inter-RAT cell reselection from GSM to UMTS is triggered within 15s after the cell reselection from UMTS to GSM, the value of TDD Cell Reselect Diversity must be increased by 5 dB.
When the condition for the cell reselection from GSM to UMTS and the condition for the cell reselection between GSM cells are met, the MS selects the UMTS cell as the target cell.
3.2.3 Fast 3G Reselection at 2G CS Call Release Overview Normally, after an MS terminates a call in a GSM cell, it camps on the GSM cell. When a neighboring UMTS cell meets the requirements for cell reselection, the MS camps on the UMTS cell after the cell reselection. Before initiating the UMTS cell reselection, the MS must receive system information and calculate cell reselection parameters. When the Fast 3G Reselection at 2G CS Call Release feature is activated, the BSS determines the best neighboring UMTS cell based on the measurement information on the neighboring UMTS cells after the call termination in a GSM cell. Then, the BSS sends the frequency information on the neighboring UMTS cell through a Channel Release message to the MS to instruct it to camp on the UMTS cell. In this way, the MS camps on a UMTS cell without calculating cell reselection parameters, thus accelerating cell reselection. In addition, the MS camps on the UMTS cell for a longer period, thus increasing the revenue of operators in the UMTS network.
This feature is activated when Select 3G Cell After Call Release is set to YES.
A UMTS cell is classified into the UTRAN FDD cell and the UTRAN TDD cell.
Procedure Take the case of call termination by the MS as an example. Figure 3-1 shows the cell reselection procedure.
1. After receiving the Release Complete message from the MS, the MSC sends a Clear Command message to the BSC to instruct the BSC to release the occupied resources on the A and Um interfaces.
2. The BSC sends a Channel Release message to the MS to instruct the MS to release the TCH or SDCCH on the Um interface. The Channel Release message may carry the information element "Cell selection indicator after release of all TCH and SDCCH", which contains the information on the target neighboring UMTS cell.
3. After receiving the Channel Release message, the MS disconnects the uplink signaling link. Then, the MS sends a DISC frame to the BTS to instruct the BTS to release the TCH or SDCCH.
4. After receiving the UA message, the MS switches to idle mode and initiates cell reselection.
If... Then...
The Channel Release message contains the information element "Cell selection indicator after release of all TCH and SDCCH",
The MS attempts to camp on the cell indicated in the Channel Release message.
The Channel Release message does not contain the information element "Cell selection indicator after release of all TCH and SDCCH",
The MS attempts to camp on the cell where the TCH or SDCCH is already released.
5. If the 4 fails, the MS performs the normal cell reselection procedure. For details on the normal cell reselection procedure, see Inter-RAT Cell Reselection from GSM to UMTS.
Before sending the Channel Release message, the BSC determines whether to carry the information element "Cell selection indicator after release of all TCH and SDCCH" in the message.
1. If Select 3G Cell After Call Release is set to YES, the procedure proceeds to 2. Otherwise, the procedure is complete, and the BSC sends the Channel Release message to the MS. The message does not carry the information element "Cell selection indicator after release of all TCH and SDCCH".
2. The BSC determines whether an MS supports both GSM and UMTS through the classmark. If the classmark does not indicate the MS capability of supporting the GSM/UMTS, the procedure proceeds to 3. Otherwise, the procedure is complete, and the BSC sends the Channel Release message to the MS. The message does not carry the information element "Cell selection indicator after release of all TCH and SDCCH".
3. The BSC figures out the best neighboring UMTS cell based on the related measurement report, and then the procedure proceeds to 4. If there is no measurement report or the measurement report does not contain the information on the neighboring UMTS cell, the procedure is complete, and the BSC sends the Channel Release message to the MS. The message does not carry the information element "Cell selection indicator after release of all TCH and SDCCH".
4. If the measurement report indicates a neighboring UMTS FDD cell, Cell Selection Indicator is set to UTRAN FDD Description. If the measurement report indicates a neighboring UTRAN TDD cell, Cell Selection Indicator is set to UTRAN TDD Description, and the procedure is complete. Meanwhile, the MSC sends the Channel Release message to the MS. The message contains the information element "Cell selection indicator after release of all TCH and SDCCH".
3.2.4 NACC and NC2 When MS is in packet transfer mode, NACC and NC2 can be performed for inter-RAT cell reselection. For details, see NACC Parameter Description and NC2 Parameter Description.
3.3 2G/3G Inter-RAT Handover The 2G/3G inter-RAT handover involves the handover from GSM to UMTS and the handover from UMTS to GSM. The handover is controlled mainly by the network.
For MSs in dedicated mode, inter-RAT handovers can be performed, including the emergency handover, better cell handover, inter-RAT load handover, and inter-RAT service handover.
Emergency handover refers to the handover that is triggered when the call cannot be processed in the serving cell because of poor coverage or other reasons during the CS service of the dual-mode MS. For example, when an MS during a call in the GSM cell is moving to the outside of the cell, the emergency handover is triggered to avoid call drops.
Better cell handover refers to the handover that is triggered when the signal quality of the neighboring cell is better than that of the serving cell, so that better service quality and user experience can be achieved. For example, when the signal quality of a UMTS cell is better than that of the serving GSM cell, MSs in the serving cell can be handed over to the UMTS cell to achieve better voice quality.
Inter-RAT load handover refers to the handover wherein some calls served by a GSM cell are handed over to a UMTS cell or some calls served by a UMTS cell are handed over to a GSM cell because of heavy load in the serving cell. For an incoming inter-RAT handover to a GSM cell, if the traffic load in the target GSM cell is also heavy, the target cell rejects the handover to avoid ping-pong handovers.
In the inter-RAT service handover, the operator can choose the network that the MS will access through the MSC. For a call to be accessed in a GSM cell, if the MSC indicates that the service handover should be performed, the BSS hands over the call to the UMTS cell. Otherwise, the BSS does not hand over the call to a UMTS cell when a handover is required during the call.
When the cell delivers the neighboring TD-SCDMA cell information, MSs from certain manufacturers may be restarted because defects exist in MS chips. To solve the problem, Huawei optimizes GSM/TD-SCDMA interoperability.
3.3.1 Inter-RAT Handover from UMTS to GSM MSs in dedicated mode can be handed over from a UMTS cell to a GSM cell. The handover decision and handover procedure are controlled by the RNC. The BSS considers the incoming handover from UMTS to GSM as a general inter-BSC handover.
The parameter Inter-RAT In BSC Handover Enable determines whether inter-RAT handover from UMTS to GSM is enabled. If Inter-RAT In BSC Handover Enable is set to No, the BSS rejects all the requests for the handover from UMTS to GSM.
3.3.2 Inter-RAT Handover from GSM to UMTS The parameter Inter-RAT In BSC Handover Enable determines whether the inter-RAT handover from GSM to UMTS is enabled. If Inter-RAT In BSC Handover Enable is set to NO(No), the BSS rejects all the requests for the handover from GSM to UMTS and does not select a UMTS cell as the target cell.
In dedicated mode, the MS obtains the neighboring UMTS cell list and other information from the Measurement Information. Then, the MS reports the measurement result to the BSS through the measurement report. After receiving the measurement result, the BSS determines whether to initiate the inter-RAT handover from GSM to UMTS based on the measurement result and the handover algorithm.
The inter-RAT handover from GSM to UMTS can be classified into emergency handover and better 3G cell handover. The algorithm for the emergency handover from GSM to UMTS is the same as that for the general emergency handover. For details, see Handover Parameter Description.
In the GSM network, the parameter Inter-rat HO Preference determines whether the GSM cell or the UMTS cell is preferentially selected as the target cell.
When Inter-rat HO Preference is set to Pre_2G_Cell(Preference for 2G cell), the BSC preferentially selects the GSM cell as the target cell.
When Inter-rat HO Preference is set to Pre_3G_Cell(Preference for 3G cell), the BSC preferentially selects the UMTS cell as the target cell.
When Inter-rat HO Preference is set to Pre_2G_CellThres(Preference 2G cell by thresh), the BSC determines the target cell according to the levels of the neighboring GSM cells and the value of HO Preference Threshold for 2G Cell. If no neighboring GSM cell has a level higher than HO Preference Threshold for 2G Cell, the BSC selects a UMTS cell as the target cell.
Better 3G cell handover can be performed only when both Inter-RAT Out BSC Handover Enable and Better 3G Cell HO Allowed are set to YES(Yes). The system performs a handover decision based on the measurement result.
If there is TDD 3G Better Cell HO Valid Time in TDD 3G Better Cell HO Watch Time and the measured value meets the following condition, the better 3G cell handover is triggered. CPICH RSCP > RSCP Threshold for Better 3G Cell HO
3.3.3 2G/3G Inter-RAT Load Handover The parameters Inter-RAT Out BSC Handover Enable and Allow Inter-RAT Load HO in Connect State determine whether inter-RAT load handover is enabled.
The algorithm for inter-RAT load handover is the same as that for load handover. For details, see Load Handover in Handover Parameter Description. The BSC obtains the traffic load on the UMTS cell from the load information contained in the handover request from UMTS to GSM. To avoid the ping-pong handover, the system takes the traffic load on the UMTS cell into consideration when initiating the inter-RAT load handover from GSM to UMTS. If the load on the UMTS cell exceeds Load handover Load Accept Threshold of the external 3G cell, the BSC does not consider that UMTS cell as the target cell.
3.3.4 2G/3G Inter-RAT Service Handover The parameters Inter-RAT Out BSC Handover Enable and Service Based Handover Switch determine whether inter-RAT service handover is enabled.
The inter-RAT service handover is processed according to the service handover indication from the MSC. The MSC instructs the BSS whether the service handover should be performed through the Service Handover information element in the Assignment Request or Handover Request. The service handover indication in the Service Handover information element can be of three values: Handover to UTRAN or cdma2000 should be performed, Handover to UTRAN or cdma2000 should not be performed, or Handover to UTRAN or cdma2000 shall not be performed.
The BSC handles the handover request as follows:
If the service handover indication is "Handover to UTRAN or cdma2000 should be performed", the BSC selects a UMTS cell from the neighboring cell list as the target cell, and then initiates the handover from GSM to UMTS.
If the service handover indication is "Handover to UTRAN or cdma2000 should not be performed", the BSC does not initiate the handover procedure. If a handover is needed during the call, a GSM cell is preferentially selected as the target cell.
If the service handover indication is "Handover to UTRAN or cdma2000 shall not be performed", the call is not allowed to be handed over to a UMTS cell. The BSC selects only the GSM cell as the target cell during the whole call.
3.4 GSM/TD-SCDMA Interoperability Optimization After the GSM cell is configured with neighboring TD-SCDMA cells, some MSs restart or stop working. This is because these MSs have defects in system information decoding. To solve this problem, Huawei optimizes GSM/TD-SCDMA interoperability. The parameter TDD System Information Optimized Allowed determines whether to enable GSM/TD-SCDMA interoperability optimization.
If TDD System Information Optimized Allowed is set to YES(Yes) and the neighboring UMTS cell of the )GSM cell is a TDD cell, the BSS adds a virtual FDD cell description before the TDD cell description when delivering the System Information 2Quater and Measurement Information. In addition, the BSS delivers only the frequency information of the TDD cell in the TDD cell description without scrambling code information. If the GSM cell has multiple neighboring TDD cells with the same frequency and different scrambling codes, the BSS delivers the description of only one cell in the System Information 2Quater and Measurement Information to the MS, that is, these neighboring TDD cells are regarded as one neighboring cell. The neighboring TDD cell of a GSM cell can be configured with a maximum of 16 different frequencies.
During network planning, different frequencies must be planned for the neighboring TDD cells of each GSM cell. Otherwise, the handover from the GSM cell to the TD-SCDMA cell may fail.
In addition, the parameter TDD MI System INFO Broadcasting Prohibit determines whether the BSS delivers the Measurement Information that contains the neighboring 3G cell information to avoid faults occurring in some MSs with decoding defects.
3.5 PS GSM and TD-SCDMA Interoperability Optimization When the network is not configured with the PBCCH, the MS in packet transfer mode performs the cell reselection procedure in idle mode.
During the PS service, if the MS performs autonomous cell reselection from GSM to TD-SCDMA, the KPIs may deteriorate after the cell reselection. To solve this problem, the BSC sends the PACKET
MEASUREMENT ORDER message to the MS, instructing the MS to filter the neighboring TDD cell list. In this way, the MS in packet transfer mode does not reselect a neighboring TDD cell.
Prohibiting cell reselection from GSM to TD-SCDMA When TDD System Information Optimized Allowed is set to NO(No), the BSC sends the PACKET MEASUREMENT ORDER message to the MS after the PS service access is successful. The cell reselection parameter Qsearch P is set to 15 to prohibit the MS from listening to the neighboring TDD cell list, thus prohibiting the MS from reselecting the neighboring TDD cell.
Modifying parameter settings When the value of TDD MI System INFO Broadcasting Prohibit, Network Control Mode, or Cell Reselection MR Period in Packet Transfer Mode is changed, the BSC sends the PACKET MEASUREMENT ORDER message to all the MSs in packet transfer mode in the cell, instructing the MSs to update the parameter value dynamically.
4 Engineering Guidelines Related Parameters in the System Information 2G/3G interoperability requires the support of MSs. After 2G/3G interoperability is enabled, the system should obtain the support capability of MSs. Therefore, the early classmark sending function should be enabled so that MSs report their support capability as soon as possible. It is recommended that ECSC be set to YES(Yes).
During the configuration of the inter-RAT cell reselection parameters and handover thresholds, the consistency between the GSM parameters and the UMTS parameters should be taken into account to avoid ping-pong handovers.
The network can control the cell reselection between GSM and UMTS through related parameters in the system information. If the operator requires that MSs access the UMTS network preferentially in the areas covered by the UMTS network, it is recommended that Qsearch I be set to 7. If Qsearch I be set to 7, the UMTS cell searching is performed.
The value of TDD Cell Reselect Diversity determines cell reselection. If MSs are expected to camp on the UMTS network, the value of TDD Cell Reselect Diversity should be changed so that the actual offset is a negative value.
When the value of TDD Cell Reselect Diversity is smaller than 8, the corresponding actual offset is smaller than 0.
Neighboring UMTS Cell Configuration Currently, the BSC6900 supports two types of neighboring UMTS cells using different access technologies. One is the neighboring WCDMA cell, a neighboring UMTS cell using FDD, which is called neighboring FDD cell. The other is the neighboring TD-SCDMA cell, a neighboring UMTS cell using TDD, which is called neighboring TDD cell. The neighboring UMTS cells of a cell must be all the neighboring FDD cells or neighboring TDD cells. The neighboring FDD cells and neighboring TDD cells cannot be configured for a GSM cell simultaneously.
Before 2G/3G interoperability is enabled, neighboring UMTS cells must be configured. The UMTS cell can be configured on the BSS side through the addition of external 3G cells. If the UMTS cell is a TD-SCDMA cell, Utran Cell Type is set to TDD(TDD).
When GSM/TD-SCDMA interoperability optimization is not enabled, a GSM cell can be configured with a maximum of 64 neighboring TDD cells. These neighboring cells can have a maximum of 3 different frequencies, and a maximum of 32 neighboring TDD cells can have the same frequency.
When GSM/TD-SCDMA interoperability optimization is enabled, the neighboring TDD cells of a GSM cell can have a maximum of 16 different frequencies. In addition, a maximum of 64 neighboring TDD cells can be configured. When GSM/TD-SCDMA interoperability optimization is enabled, the scrambling code information of TD-SCDMA cells is not delivered in the system information. If multiple neighboring TD-SCDMA cells of the GSM cell have the same frequency, the BSS cannot determine the mapping between the measurement information and the neighboring cells. This may cause handover failures easily. Therefore, when GSM/TD-SCDMA interoperability optimization is enabled, a GSM cell should not be configured with neighboring TDD cells that have the same frequency and different scrambling codes.
GSM/TD-SCDMA Interoperability Optimization To avoid communication failures due to MS chip defects, both TDD System Information Optimized Allowed and TDD MI System INFO Broadcasting Prohibit are set to YES(Yes) in the cell configured with neighboring TDD cells.
5 Parameters This chapter describes the parameters related to 2G/3G Interoperability (TDD).
For the meaning of each parameter, see Table 5-1. For the default value, value ranges, and MML commands of each parameter, see Table 5-2.
Table 5-1 Parameter description (1)
Parameter Description
TDD 3G Better Cell HO Watch Time
According to the P/N rule, if the conditions for the handover to a better 3G cell are met in P of N measurement reports, the handover is triggered. This parameter specifies the number N.
Better 3G Cell HO Allowed
This parameter specifies whether to allow 3G better cell handover algorithm.
Better Cell HO Valid Time
According to the P/N rule, if the conditions for the handover to a better cell due to interference are met for P seconds within N seconds, the handover is triggered. This parameter specifies the number P.
Cell Reselection MR Period in Packet Transfer Mode
Cell reselection measurement report period in packet transmission mode.
ECSC
The early classmark sending control (ECSC) parameter specifies whether the MSs in a cell use early classmark sending. After a successful immediate assignment, the MS sends additional classmark information to the network as early as possible. The additional classmark information mainly contains the CM3 (classmark 3) information. The CM3 (classmark 3) information contains the frequency band support capability of the MS (used for the future channel assignment), power information about each frequency band supported by the MS (used for the handover between different frequency bands), and encryption capability of the MS.
HO Preference Threshold for 2G Cell
If the receive level of the neighboring 2G cell that ranks the first in the candidate cell list is equal to or smaller than this threshold, the BSC preferentially selects a neighboring 3G cell as the handover target cell. Otherwise, the BSC preferentially selects a neighboring 2G cell as the handover target cell.
This parameter specifies whether a 2G cell or to a 3G cell is preferentially selected asthe target cell for handover. When this parameter is set to Pre_2G_Cell, the BSC preferentially selects a 2G candidate cell as the target cell for handover. When this parameter is set to Pre_3G_Cell, the BSCpreferentially selects a 3G candidate cell as the target cell for handover. When this parameter isset to Pre_2G_CellThres, the BSC preferentially selects a neighboring 3G cell as thehandover target cell if the receive level of the neighboring 2G cell that ranks the firstin the candidate cell list is equal to or smaller than "HO Preference Threshold for 2GCell". Otherwise, the BSC preferentially selects a neighboring 2G cell as the handovertarget cell.
Inter-RAT In BSC Handover Enable
This parameter specifies whether the handover from 3G cells to 2G cells is allowed.
Inter-RAT Out BSC Handover Enable
This parameter specifies whether the handover from 2G cells to 3G cells is allowed.
Network Control Mode
Network control mode for cell reselection of the MS. There are three modes. NC0: normal MS control. The MS shall perform autonomous cell re-selection. NC1: MS control with measurement reports. The MS shall send measurement reports to the network and the MS shall perform autonomous cell re-selection. NC2: network control. The MS shall send measurement reports to the network . The MS shall only perform autonomous cell re-selection when the reselection is triggered by a downlink signalling failure or a random access failure.
This parameter specifies the level threshold for cell reselection in idle mode. In idle mode, if the signal level of the serving cell is below [0, 7] or above [8, 15], the MS starts to search for 3G cells. For example, if this parameter is set to 5 and if the signal level of the serving cell is lower than 5, the MS starts to search for 3G cells; if this parameter is set to 10 and if the signal level of the serving cell is above 10, then the MS starts to search for 3G cells The values of this parameter correspond to the following decibel values: 0: -98 dBm 1: -94 dBm 2: -90 dBm 3: -86 dBm 4: -82 dBm 5: -78 dBm 6: -74 dBm 7: (always), that is, the MS keeps searching for 3G cells 8: -78 dBm 9: -74 dBm 10: -70 dBm 11: -66 dBm 12: -62 dBm 13: -58 dBm 14: -54 dBm 15: (never), that is, the MS does not search for 3G cells
This parameter specifies one threshold of the signal level for cell reselection in packet transfer mode. In packet transfer mode, if the signal level of the serving cell is below [0, 7] or above [8, 15], the MS starts to search for 3G cells. For example, if this parameter is set to 5 and if the signal level of the serving cell is lower than 5, the MS starts to search for 3G cells; if this parameter is set to 10 and if the signal level of the serving cell is above 10, then the MS starts to search for 3G cells. The values of this parameter correspond to the following decibel values: 0: -98 dBm 1: -94 dBm 2: -90 dBm 3: -86 dBm 4: -82 dBm 5: -78 dBm 6: -74 dBm 7: (always), that is, the MS keeps searching for 3G cells 8: -78 dBm 9: -74 dBm 10: -70 dBm 11: -66 dBm 12: -62 dBm 13: -58 dBm 14: -54 dBm 15: (never), that is, the MS does not search for 3G cells
RSCP Threshold for Better 3G Cell HO
The 3G better cell handover is triggered only when the RSCP of a neighboring 3G cell is greater than this threshold for a period of time.
Select 3G Cell After Call Release
This parameter specifies whether to allow a mobile phone to preferentially camp on a 3G cell after a call is terminated in the areas covered by both the GSM network and the UMTS network.
TDD Cell Reselect Diversity
A TDD cell can become a candidate cell only when the average receive level of the TDD cell is greater than the TDD Cell Reselect Diversity of the serving cell. The value of this parameter corresponds to the following decibel value: 0: negative infinity 1: -28 dB 2: -24 dB ... 15: 28 dB
TDD MI System INFO Broadcasting Prohibit
This parameter determines whether the broadcasting of the MI system information is prohibited.
8 Reference Documents 3GPP TS 45.008 Radio subsystem link control 3GPP TS 44.018 Mobile radio interface layer 3 specification; Radio Resource Control (RRC) protocol 3GPP TS 48.008 Mobile Switching Centre - Base Station system (MSC-BSS) interface; Layer 3 specification
