HSDPA quality of service (QoS) management

HSDPA QoS management functionality allows to prioritize different QoS traffic class RABs on the HS-DSCH. The optional QoS Aware HSPA Scheduling feature is applied if the following conditions are fulfilled:

• HSDPA Dynamic Resource Allocation optional feature is used in the cell (HSDPADynamicResourceAllocation parameter is set to 'Enabled')
• QoS Aware HSPA Scheduling optional feature activated on cell level via the HSPAQoSEnabled RNP parameter

Whenever the optional QoS Aware HSPA Scheduling feature (HSPAQoSEnabled RNP parameter set to 'Enabled') is used, prioritizing RABs of interactive and background QoS traffic classes mapped to HSDPA transport channels is based on the following parameters received from the core network:

• Signaling indication
• Traffic class (TC)
• Traffic handling priority (THP)
• Allocation retention priority (ARP)

The latter three parameters (TC, THP, and ARP) are mapped according to operator-defined rules to the respective prioritization value used in the RNC. The mapping is realized via the QoSPriorityMapping RNP parameter. Whenever the HS-DSCH is affected, the relevant value is then sent to the BTS as scheduling priority indicator (SPI) value.

Additionally, the Streaming QoS for HSPA optional feature defines whether or not streaming RABs may be mapped to the HS-DSCH and handled by HSDPA QoS management. QoS support for PS streaming RBs mapped to the HS-DSCH is only applied if the HSPAQoSEnabled RNP parameter set to value '2' and the prerequisites for QoS Aware HSPA Scheduling are fulfilled.

Note that if the Streaming QoS for HSPA optional feature is not activated within the cell, RABs with streaming QoS traffic class cannot be mapped to the HS-DSCH but can be used on DCH. Furthermore, if the HSDPA Dynamic Resource Allocation optional feature is not activated (via the HSDPADynamicResourceAllocation RNP parameter), RABs with streaming QoS traffic class must not be mapped to the HS-DSCH but have to be used on DCH.

Basic principles and QoS prioritization decision

Based on the before-mentioned RNP parameters' values defined by the operator and the values of the parameters received via RANAP and RNSAP (TC, THP, ARP), QoS prioritization of RABs is handled with the QoSPriorityMapping RNP parameter. Whenever the received THP or ARP values are not smaller than or equal to three (3), value 3 is used for the mapping with the restriction that a maximum of 16 different priorities can be used.

The basic principles applied for QoS-based prioritizing of QoS classes are the following:

• Priorities for DCH streaming, interactive, and background connections are always read from the QoSPriorityMapping parameters
• Priority of non-realtime (NRT) RABs mapped to the HS-DSCH depends on whether or not QoS prioritization for NRT services is activated in the cell:
  • If QoS prioritization for NRT services is activated, the actual priority for these RABs is read from the structured QoSPriorityMapping parameters, defined on RNC level.
  • Otherwise, if QoS prioritization for NRT services is not activated, the actual priority for these RABs is always equal to zero (0).
• Priority of streaming RABs mapped to the HS-DSCH depends on whether or not streaming in HSDPA transport channels is activated in the cell
  • If streaming in HSDPA transport channels is activated, the actual priority for these RABs is read from the QoSPriorityMapping parameters.
  • Otherwise, if streaming in HSDPA transport channels is not activated, the actual priority for these RABs is always equal to zero (0).
• Priority of interactive signaling RABs has to be larger than the priority used for any other NRT service

The following table provides the default values of the QoSPriorityMapping parameters, which allow to define different priorities depending on the QoS class and the RAB's priority type.

QoS Class	Priority Type	Priority Value
Streaming	ARP 1	13
	ARP 2	13
	ARP 3	13
Interactive	Signaling	12
	THP 1 ARP 1	11
	THP 1ARP 2	11
	THP 1 ARP 3	11
	THP 2 ARP 1	8
	THP 2 ARP 2	8
	THP 2 ARP 3	8
	THP 3 ARP 1	5
	THP 3 ARP 2	5
	THP 3 ARP 3	5
Background	ARP 1	0
	ARP 2	0
	ARP 3	0

Table 1:

Default values of the QoSPriorityMapping parameters

Whenever the mapping of QoS priorities has been changed, these changes become effective for only those RABs to which DCH or HS-DSCH allocation or reconfiguration is applied afterward. As regards HS-DSCHs, the assigned priority is then directly used as SPI value which, in turn, is sent to the BTS. An SPI value equal to zero (0) is transmitted whenever the optional QoS Aware HSPA Scheduling feature is deactivated (HSPAQoSEnabled RNP parameter set to “Disabled”). Dedicated channels (DCHs) have a value in the range between zero (0) and 15, indicating the lowest and highest priority values, respectively.

How the various RAB parameters (TC, THP, ARP) received via RANAP or RNSAP are handled during branch addition or relocation, depends on the actual scenario:

• Branch addition over Iur interface
  When a branch is added to the drift RNC (DRNC), the TC, ARP and frame handling priority (FHP) parameters are received via the Iur interface. Admission control then defines the THP, based on the received FHP value, see Definition of the NBAP/RNSAP frame handling priorities in SRNC in WCDMA RAN RRM Admission Control. If the source RNC (SRNC; from a different manufacturer than Nokia Siemens Networks) then sends an FHP value which is higher or lower than the one defined by admission control for PS interactive services,
  • THP is adjusted to the nearest THP value in the mapping table.
  • FHP is not changed and remains as it has been received. The RNC then sends the FHP value to the BTS via NBAP message.
  The RNC uses the mapped THP value as well as the received TC and ARP values to define the QoS priority. This priority is only forwarded to transport network layer when the branch is set up. In this way, the transport priority is as exact as it can be with the information available.
• UE not involved relocation
  In this scenario, the target RNC defines the QoS priority from RAB parameters (TC, ARP, THP) received in RANAP: Relocation Request message. While the cell-specific packet scheduler becomes immediately aware of the defined QoS priority and RAB parameters, either of them will only be updated on the transport layer either
  • When the next channel type switch back to HSPA channel configuration occurs, for example, or
  • After inactivity resources are again needed for data transmission.
• UE involved relocation
  In the event of a hard handover (UE involved relocation), the target RNC defines the QoS priority from RAB parameters (TC, ARP, THP) received in RANAP: Relocation Request message. In this way, both the QoS priority and the RAB parameters are known when radio channels are allocated and set up on the transport network layer.

Nominal bit rates for HSDPA non-realtime (NRT) services

The nominal bit rate (NBR) is defined as the bit rate which is set in the RNC for NRT HS-DSCHs and sent to the BTS as guaranteed bit rate (GBR). The principles of NBR thus are the following:

• NBRs can only be used for NRT traffic classes.
• NBRs are applied in only those cells for which streaming in HSDPA transport channels is activated (HSPAQoSEnabled RNP parameter set to “Enabled”). Otherwise, an NBR value equal to zero (0) will be applied.
• For each QoS priority value used for the respective NRT traffic classes, NBRs can be defined either for both uplink (UL) and downlink (DL) directions or for only one direction.
• Priorities which have been assigned NBRs have to form a continuous block within the QoSPriorityMapping parameter, starting with the highest priority used for NRT services. After this block, traffic classes in the QoSPriorityMapping parameter have to be ordered as follows:

  1.	Priorities used by streaming services Their NBR always equals to zero (0); their priority value, however, is larger than the ones used for NRT users having defined QoS.
  2.	Priorities used by NRT users having defined QoS The NBR of these users is specified for at least one direction (UL or DL or both).
  3.	Priorities used by best effort (BE) users, i.e. NRT users without QoS. Their NBR always equals to zero (0).

In the RNC, NBRs are managed and stored using the structured HSPANBRValues RNP parameter, which is defined on RNC level. The HSPANBRValues parameter allows to specify NBRs for UL and DL directions for those HS-DSCHs with priority values (QoSPriorityMapping parameter) in the range between zero (0) and twelve (12). Whenever the defined NBR values are modified, the changes will become effective only for new RABs, while the mapping for existing RABs remains unchanged.

Whenever a RAB's maximum bit rate is smaller than the NBR defined for this QoS class and priority type, this maximum bit rate will be used as the RAB's NBR value and only the resources required for this bit rate are reserved. Otherwise, resources would be wasted.

Cell-level measurements used by PS streaming

If HSPA streaming is activated in a particular cell by setting the HSPAQoSEnabled parameter appropriately, two measurements are initiated: HS-DSCH provided bit rate measurement (PtxHSProBR) and HS-DSCH required power measurement (PtxHSRePo).

For each scheduling priority indicator (SPI), the WBTS measures both the provided bit rate and the power required by the HS-DSCH and reports the measured values to the RNC via the Nokia-proprietary NBAP: Radio Resource Measurement Report message. For the purpose of higher-layer filtering, the RNC informs the WBTS about the filter coefficient to be used, using the Nokia-proprietary NBAP:Radio Resource Measurement Initiation message's "Measurement Filter Coefficient" information element (IE). The value specified in this IE is controlled with the PtxMeasFilterCoeff parameter.

The RNC furthermore sends the Nokia-proprietary NBAP:Radio Resource Measurement Initiation message to the WBTS to control the reporting period of the cell-level measurements used by PS streaming, indicated by the RRIndPeriod parameter. The WBTS can however filter the measured values obtained in the PtxHSProBR and PtxHSRePo measurements with defined limits. The maximum number of consecutive filtered measurement reports is set to a fixed value of nine (9) periods. If no new measurement result is received from the WBTS, the RNC uses the result previously received.

The RNC does neither average nor estimate the HS-DSCH provided bit rate and HS-DSCH required power for the following reasons: as measurement periods can be quite long, averaging has to rely on estimated values. Estimation, in turn, is however not possible in the RNC because HSPA scheduling is performed by the BTS rather than the RNC.

PS NRT RAB reconfiguration

Basically, RAB reconfiguration can be requested by the SGSN or by the UE. Toward the RAN, the modification is triggered by the core network, signalled through a RANAP: RAB Assignment Request message. The RAB identifier (ID) contained in this message uniquely identifies the RAB to be modified, where several RAB IDs can be transmitted within one RANAP: RAB Assignment Request message.

For interactive and background traffic class RABs, the following RAB parameters can thus be changed:

• Traffic class (TC), from interactive to background and vice-versa
• Maximum bit rate (MBR) for uplink (UL) and downlink (DL)
• Traffic handling priority (THP) of an interactive RAB
• Allocation and retention priority (ARP)

If modification of any parameter other than the above-mentioned RAB parameters is requested, the RNC responds via a RANAP: RAB Assignment Response message with cause code set to Invalid RAB Parameters Combination.

Depending on the UE's current state, the type of request (downgrade or upgrade of QoS parameters), and whether the UE is using DCH or HSPA service, the RNC individually handles the particular PS NRT RAB reconfiguration request.

When a particular UE is in CELL_DCH state, using HSPA service, and modification of QoS parameters is requested, the new RAB parameters are taken into use immediately. The RNC thus matches the RAB's QoS parameters to a QoS priority mapping as is done for the QoSPriorityMapping management parameter, see table Default values of theQoSPriorityMapping parameters.

Before RAB modification is actually started, however, the RNC checks whether or not PS NRT RAB reconfiguration is supported in the BTS, verifying theNodeBRABReconfigSupport parameter. This check is only necessary in case of HSPA connections because the BTS is responsible for HSPA scheduling. Depending on the configuration, the BTSes with the following roles have to support PS NRT RAB reconfiguration:

• DCH/HS-DSCH configuration: the RNC only has to check the capability of the serving BTS, controlling the serving cell.
• E-DCH/HS-DSCH configuration: the RNC has to check the capability of all BTSes which are involved in the E-DCH active set.

In either case, if the queried BTSes do not support RAB modification, the update of the RAB parameters is stopped. Otherwise, RNC prioritizes the NRT RBs according to their QoS priority values and defines the scheduling priority indicator (SPI) for HSPA connections. The SPI is based on the QoS priority value and the value of the HSPAQoSEnabledparameter.

The following cases thus have to be distinguished:

• RAB's new maximum bit rate (MBR) is smaller than existing bit rate for HSDPA-associated UL DCH
  The HSDPA -associated UL DCH is downgraded to a rate that is both still suitable and equal to or lower than the new maximum bit rate of the RAB.
  • If none of the bit rates are allowed although there is no congestion situation, channel type switch (CTS) to DCH with UL and DL rates greater than 0 kbit/s (DCH >0/>0) is performed.
  • Otherwise, if UL bit rates cannot be assigned due to congestion, the RNC checks the source of congestion.
    If congestion occurred on the RNC's transport network layer, channel type switch (CTS) to DCH >0/>0 is performed.
    If congestion occurred due to any other reason, CTS to DCH 0/0 is done. CTS to DCH 0/0 is only performed when all other RABs assigned to the UE are also on DCH >0/>0. If at least one existing RAB is on DCH 0/0, however, the UE will be switched from CELL_DCH to CELL_FACH state.
• QoS parameter change in case of DCH/HS-DSCH configuration
  If the traffic class (TC) and/or the traffic handling priority (THP) change during DCH/HS-DSCH configuration, a new frame handling priority (FHP) as well as the updated UL DCH load factor will be calculated. During the next scheduling period (radio link reconfiguration), the BTS will also be informed about the changed FHP.

Whether or not particular services, identified by traffic class and traffic handling priority, can use HS-DSCH and E-DCH is defined by the HSDSCHQoSclasses andEDCHQOSClasses management parameters, respectively. As a consequence, CTS to DCH/HS-DSCH is performed if a UE uses HSUPA but HSUPA is not supported with the modified RAB parameter values. In a similar way, CTS to DCH >0/>0 is executed when a UE makes use of HSDPA or HSUPA but HSDPA is no longer allowed after RAB reconfiguration, when the changed values become effective.

If the optional Streaming QoS for HSPA feature is simultaneously active, calculation of the nominal bit rate (NBR) for NRT connections mapped to HSPA transport channels is based on the HSPANBRValues management parameter, see Nominal bit rates for HSDPA non-realtime (NRT) services.

For more information, see PS NRT RAB reconfiguration in and PS NRT RAB reconfiguration in

HSDPA mobility handling

In Nokia Siemens Networks RAN, there are two methods available to handle the HSDPA mobility:

• HSDPA mobility handling with the serving HS-DSCH cell change (see HSDPA mobility handling with the Serving HS-DSCH Cell Change)
• HSDPA cell reselection and HSDPA mobility handling with DCH switching (see HSDPA cell reselection)

The operators can set the preferred method with the HSDPAMobility management parameter.

Changing the parameter value does not affect the existing RRC connections. The new value is used for new RRC connections only.

Inter-RNC mobility (HSPA inter-RNC cell change feature) is described in the chapter Inter-RNC mobility.

Inter-frequency handovers for HSDPA services are described in section HSDPA inter-frequency handover.

HSDPA mobility handling with the Serving HS-DSCH Cell Change

This feature can be activated by enabling the HSDPAMobility parameter.

Figure 26:

The serving HS-DSCH cell change in active set

In the figure above, the HS-PDSCH allocation for a given UE only belongs to one of the radio links assigned to the UE, the serving HS-DSCH radio link. The cell associated with the serving HS-DSCH radio link is defined as the serving HS-DSCH cell. The HS-DSCH transport channel is never in diversity handover. A serving HS-DSCH cell change facilitates the transfer of the role of serving HS-DSCH radio link from one radio link belonging to the source HS-DSCH cell to a radio link belonging to the target HS-DSCH cell.

The serving HS-DSCH cell change is a network controlled synchronous procedure (for example, transmission and reception of HS-DSCH are stopped and started at the time instant given by the RNC). The RNC bases the target cell selection on the periodically reported measurements from UE (intra-frequency CPICH Ec/No) and the BTS (dedicated UL SIR_error). If there is no suitable target cell when the CPICH Ec/No triggers the serving HS-DSCH cell change, the current cell is kept. If there is no suitable target cell when any other trigger initiates the serving HS-DSCH cell change, the HS-DSCH MAC-d flow is released and the RB is mapped to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch).

Either an intra-BTS or an inter-BTS can execute the serving HS-DSCH cell change. The serving HS-DSCH cell change feature also includes the soft handover of an associated DPCH (that is, signalling link and UL DCH return channel can be in SHO).

Figure 27:

Inter-Node B serving HS-DSCH cell change combined with serving HS-DSCH Node B relocation

At an inter-Node B serving HS-DSCH cell change, a serving HS-DSCH Node B relocation must be performed at the UTRAN. Serving HS-DSCH Node B relocation and serving HS-DSCH cell change are two separate procedures, even if the serving HS-DSCH Node B relocation cannot be performed without a serving HS-DSCH cell change.

For details about inter-RNC serving HS-DSCH cell change, refer to Inter-RNC mobility.

Measurement reporting

The measurement events when HSDPAMobility is set to 'enabled' are explained in the table below:

Event	Description
1A: “A primary CPICH enters the reporting range”	This event is a trigger for starting HSDPA specific measurements and active set update for associated channels.
1B: “A primary CPICH leaves the reporting range”	This event is a trigger for serving HS-DSCH cell change and active set update for associated channels
1C: “A non-active primary CPICH becomes better than an active one”	This event is a trigger for serving HS-DSCH cell change and active set update for associated channels.

Table 4:

Intra-frequency measurements, which are used for UE having also the HS-DSCH allocated

Event	Description
6F: “UE Rx-Tx time difference for a RL included in the active set becomes larger than an absolute threshold	This event is a trigger for serving HS-DSCH cell change.
6G: “UE Rx-Tx time difference for a RL included in the active set becomes less than an absolute threshold”	This event is a trigger for serving HS-DSCH cell change.

Table 5:

Reporting events which are used when HSDPA associated DPCH is in SHO

Event	Description
1F: A primary CPICH goes below the absolute threshold	This event is a trigger for releasing the HS-DSCH MAC-d flow
1E: A primary CPICH becomes better than an absolute threshold	This event cancels event 1F.
6A: 'UE Tx power becomes larger than an absolute threshold'	This event is a trigger for releasing the HS-DSCH.
6B: 'UE Tx power becomes less than an absolute threshold'	This event cancels event 6A.

Table 6:

Triggers for releasing the HS-DSCH MAC-d flow

In addition to the above-mentioned events, a UL quality deterioration report from outer loop power control can trigger the HS-DSCH MAC-d flow release.

In the case of a single NRT PS RAB, the measurement event 1F (A primary CPICH goes below the absolute threshold) initiates HS-DSCH MAC-d flow release and mapping of a radio bearer to DCH 0/0 kbit/s. The measurement event 1E (A primary CPICH becomes better than an absolute threshold) cancels the measurement event 1F. Each cell of the active set must trigger the measurement event 1F before HS-DSCH MAC-d flow release is started.

In the case of an AMR multi-service, the measurement events 1F (A primary CPICH goes below the absolute threshold) and 1E (A primary CPICH becomes better than an absolute threshold) are used to initiate the inter-frequency measurements. The HS-DSCH MAC-d flow is then released before initiation of the inter-frequency measurements for AMR speech CS RAB. The same applies also to the DL Transmitted Code Power measurement.

However, if the HSDPA Inter-Frequency Handover optional feature is activated and inter-frequency handover triggers are present, HS-DSCH release is not triggered. Instead, an E-DCH to DCH switch in uplink is performed if needed and interfrequency-handover measurement is started after that immediately with DL: HS-DSCH/UL: DCH configuration. For more details, see HSDPA inter-frequency handover.

For more information on measurement events introduced above, see Measurement procedure for inter-frequency handover.

The RNC selects the new Serving HS-DSCH cell based on DL CPICH Ec/No and UL SIR_error measurement results. These, and the other related parameters, are introduced in the next chapter.

Setting up the DL CPICH Ec/No and UL SIR_error measurements

The RNC orders the UE to report DL CPICH Ec/No of the cells in the active set periodically and the BTS to report UL SIR_error measurement periodically. The properties of both measurements and the related parameters are described below.

The downlink CPICH Ec/No measurement

Periodical intra-frequency CPICH Ec/No measurement is applied to the serving HS-DSCH cell change procedure for triggering and selection of the new serving cell. The measurement is started in conjunction of the setup of the HS-DSCH MAC-d flow and stopped in conjunction of the deletion of the HS-DSCH MAC-d flow.

Periodical CPICH Ec/No measurement is started only if the size of the active set is greater than one. If the size of the active set is one, that is there is only one radio link in the active set, periodical CPICH Ec/No reporting is not used.

The RNC starts and stops the measurement with the RRC: MEASUREMENT CONTROL message.

The operator cannot switch off the periodical CPICH Ec/No measurement. The measurement is always active according to the conditions described above.

The intra-frequency measurement reporting criteria of the periodical CPICH Ec/No measurement for HSDPA serving cell change is the following:

• Measurement reporting mode is fixed.
  • Transfer Mode is 'Acknowledged mode RLC'
  • Reporting Mode is 'Periodical reporting'
• Measurement quantity is CPICH Ec/No. The operators can control the filtering of CPICH Ec/No measurements with the EcNoFilterCoefficient parameter, defined by theHSDPAFmcsIdentifier or the RTWithHSDPAFmcsIdentifier parameter set.
• Reporting quantity is CPICH Ec/No for active set cells. The reporting quantity of the measurement is fixed.
• Reporting criteria is periodical reporting. The operators can configure the reporting interval with the HSDPACPICHreportPeriod parameter.

Periodically reported DL CPICH Ec/No measurement results are then averaged in the RNC. Averaging is done within a sliding averaging window.

• The operators can use the HSDPACPICHAveWindow parameter to define how many CPICH Ec/No measurements, which are received in the RRC: MEASUREMENT REPORTmessage, are included in the sliding window used in the averaging.

Averaging is performed using the following formula:

Where CPICH _Ec|No (t) is the latest received CPICH _Ec|No measurement and n equals to the value of parameter HSDPACPICHAveWindow.

The RNC calculates the averaged values from the available measurement samples, until the number of measurement samples is adequate to calculate averaged values over the whole averaging window.

Notice that periodical CPICH Ec/N0 measurement is also used in the case of direct DCH to HS-DSCH switch (see Direct DCH to HS-DSCH switch).

The uplink SIR_error measurement

The dedicated UL SIR_error measurement is used to select the serving HS-DSCH cell in the serving HS-DSCH cell change procedure. It is also used as a criterion for the sufficient UL quality for HS-DPCCH transmission. Insufficient quality triggers the HS-DSCH release.

The UL SIR_error measurement is defined in the 3GPP TS 25.215: Physical Layer Measurements specifications.

The periodical UL SIR_error measurement is started after the HS-DSCH has been allocated to the UE.

The NBAP: DEDICATED MEASUREMENT INITIATION procedure is used to start and stop the UL SIR_error measurement.

The operators can switch the periodical UL SIR_error reporting off by setting the reporting interval to zero with the HSDPASIRErrorReportPeriod parameter. If the reporting is switched off, the RNC does not use UL SIR_error as a criterion for the serving HS-DSCH cell change.

The reporting of UL SIR_error is periodical, but a report is only sent if the value has changed significantly. The reporting criteria of the dedicated UL SIR_error measurement are determined as follows:

• Dedicated measurement type is SIR_error.
• Measurement filter coefficient can be configured with HSDPASIRErrorFilterCoefficientparameter. The parameter determines the filtering coefficient value to be used in higher layer filtering of the measurement result. The higher layer filtering has been specified in the 3GPP TS 25.433: UTRAN Iub interface NBAP signalling specification.
• Report characteristics is periodic. The report periodicity defined with the HSDPASIRErrorReportPeriod operator configurable parameter.

Periodically reported UL SIR_error measurement results are averaged in the RNC. Averaging is done within a sliding averaging window.

• The operators can use the configurable HSDPASIRErrorAveWindow parameter to define how many SIR_error measurements, which are received in the NBAP: DEDICATED MEASUREMENT REPORT message, are included in the sliding window used in the averaging.

If the measurement report was not received within the reporting period, the RNC uses the latest received value instead in averaging.

The averaging is performed using the following formula:

Where SIR_Error (t) is the latest received SIR_Error measurement and n equals to the value of the HSDPASIRErrorAveWindow parameter.

The RNC calculates the averaged values from the available measurement samples, until the number of measurement samples is adequate to calculate averaged values over the whole averaging window.

Algorithm for selecting the initial serving HS-DSCH cell

The initial serving HS-DSCH cell selection algorithm is executed when at least one PS RAB is established and a capacity request leads to the HS-DSCH allocation.

Figure 28:

Algorithm for selecting the initial serving HS-DSCH cell

Finding the candidate cells

Initial selection of the serving HS-DSCH cell is based on the latest received intra-frequency DL CPICH Ec/No measurement result reported by the UE. The RNC takes the CPICH Ec/No measurement result from the latest received and stored measurement event. Periodical intra-frequency CPICH Ec/No measurement is not used for the initial selection of the serving HS-DSCH cell.

If the active set size is one, that is, there is only one cell in the active set, the HS-DSCH allocation is executed without taking DL CPICH Ec/No into account.

If the active set size is greater than one, that is, there is more than one cell in the active set, the DL CPICH Ec/No is used as criteria. All the HSDPA-capable cells that fulfil the following condition are selected as possible candidate cells for the HS-DSCH allocation:

Figure 29:

Condition for selecting the candidate cells

Where:

• CPICH_Ec/NoCell is the CPICH Ec/No measurement of the candidate cell.
• CPICH_Ec/NoBest_cell is the CPICH Ec/No measurement of the best cell in the active set.
• HSDPAServCellWindow is an operator parameter, which determines the window - relative to the best cell in the active set - inside of which the serving HS-DSCH cell must be in order to allocate HS-DSCH.

In addition, HSPA streaming has to be activated (HSPAQosEnabled parameter set to 'Enabled') in the candidate cell if the UE possesses a PS streaming RB. Otherwise, the cell will not be selected as candidate.

When the cells which fulfil all these conditions are found, the serving HS-DSCH selection is executed according to the priorities below.

Notice that if active set contains just one cell then CPICH Ec/No is not checked.

Selecting the serving HS-DSCH cell from the candidates

Priority one:	The cell that has the best DL CPICH Ec/No is chosen as the serving HS-DSCH cell.
Priority two:	The cell that has the next best DL CPICH Ec/No (first 2nd and then 3rd best) is chosen as the serving HS-DSCH cell. Note that if the HSDPA Dynamic Resource Allocation is inactive in the RNC, the cell that already has HSDPA power allocated is given the highest priority for selection of the serving HS-DSCH cell.

If HS-DSCH allocation fails, the next best cell, in accordance with the priorities above, is attempted. If none of the cells in the active set can be chosen as the serving HS-DSCH cell, or if all the attempted allocations of the HS-DSCH are unsuccessful, a DCH is scheduled.

Notice that in order to execute the serving HS-DSCH cell change and allocate the HS-DSCH at the target cell, the channel type selection algorithm must be successful, that is, the Cell/BTS must fulfil all the criteria regarding HS-DSCH allocation.

Algorithm for changing the serving HS-DSCH cell

This chapter explains the principles used to select the target cell separately for each event that can trigger the serving HS-DSCH cell change.

Operation when DL CPICH Ec/No triggers the serving HS-DSCH cell change

Periodical reporting of the intra-frequency CPICH Ec/No measurement is used for the serving HS-DSCH cell change procedure. The CPICH Ec/No of the serving HS-DSCH cell has to be close enough to the currently best cell in the active set or else the serving HS-DSCH cell change is initiated. Each time the UE sends the periodical intra-frequency CPICH Ec/No measurement report, the need for the serving HS-DSCH cell change is evaluated:

Figure 30:

The condition to initiate serving HS-DSCH cell change

In the equation, CPICH_Ec/NoServ_cell is the CPICH Ec/No measurement of the serving HS-DSCH cell, CPICH_Ec/NoBest_cell is the CPICH Ec/No measurement of the best cell in the active set and HSDPAServCellWindow is the management parameter, which determines the window - relative to the best cell in the active set - inside of which the serving HS-DSCH cell must be in order to allocate HS-DSCH.

If the HSDPACellChangeMinInterval timer is running the serving HS-DSCH cell change is not initiated because of the CPICH Ec/No measurement.

If CPICH Ec/No of the serving HS-DSCH cell is greater than or equal to the threshold, determined by the HSDPACPICHEcNoThreshold parameter, the current serving cell is kept.

To execute inter-BTS serving HS-DSCH cell change, the UL SIR_error of the target BTS must exceed the threshold determined by the HSDPASIRErrorTargetCell parameter. SIR_error measurement to be used for evaluation is the latest averaged value. In the case of an intra-BTS serving HS-DSCH cell change, the UL SIR_error  is not checked.

All the HSDPA-capable cells that fulfil the condition defined by the Equation Condition for selecting the candidate cells are selected as possible candidate cells for new serving HS-DSCH cells.

Furthermore, if the UE uses a PS streaming RB, HSPA streaming has to be activated (HSPAQoSEnabled parameter) in the target cell, as well. If this condition is not fulfilled, the respective cell is then not selected as candidate cell.

When the cells that fulfil the DL CPICH Ec/No and UL SIR_error conditions are found, the serving HS-DSCH selection is executed according to the same priorities as in the selection of initial serving HS-DSCH cell.

If none of the cells in the active set can be chosen as the serving HS-DSCH cell, that is, the serving HS-DSCH cell change cannot be executed, the current HS-DSCH allocation is kept.

If the serving HS-DSCH cell change fails, the serving HS-DSCH cell change is retried at intervals determined as follows:

Interval = min (10 seconds, Number of failures * 2 seconds)

When the time interval from the previous unsuccessful attempt has elapsed, the next periodical CPICH Ec/No report is waited for. If the condition to start serving HS-DSCH cell change is still effective, a reattempt is made.

The serving HS-DSCH cell change algorithm is illustrated in the following flowchart.

Figure 31:

Serving HS-DSCH cell change algorithm

Operation with other triggers, which initiate the serving HS-DSCH cell change

The following reasons initiate the serving HS-DSCH cell change:

• The level of the UL SIR_error in the serving cell that initiates the inter-BTS serving HS-DSCH cell change can be configured with HSDPASIRErrorServCell parameter.
• Intra-frequency measurement event 1B (A primary CPICH leaves the reporting range) or 1C (A non-active primary CPICH becomes better than an active one) initiates the serving HS-DSCH cell change if the cell to be removed from the active set is the serving HS-DSCH cell. Active set update is delayed until either serving HS-DSCH cell change or HS-DSCH release (switch to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch)) has been performed.

The following reasons, which may cause removal of the radio link from the active set, trigger the serving HS-DSCH cell change:

• Radio link failure of the serving HS-DSCH radio link (loss of UL synchronisation)
  If the BTS sends NBAP: RADIO LINK FAILURE message (loss of UL synchronisation) to the RNC regarding the current serving HS-DSCH radio link and there are other HSDPA-capable cells in the active set, the serving HS-DSCH cell change is executed. Handover control initiates the serving cell change in 3 seconds after detection of the loss of synchronization.
• Serving HS-DSCH radio link is handed over to DRNC
  If the current serving HS-DSCH radio link is handed over to DRNC, and there are other HSDPA-capable cells under SRNC in the active set, the serving HS-DSCH cell change is executed. The candidate cell must be located under SRNC to execute serving HS-DSCH cell change.
• RL removal because of Rx-Tx time difference

If the current serving HS-DSCH radio link is deleted from the active set because of Rx-Tx time difference measurement (Event 6F, 6G), and there are other HSDPA-capable cells in the active set, the serving HS-DSCH cell change is executed.

The DL CPICH Ec/No, UL SIR_error, and the support of HSPA streaming (if a PS streaming RB exists) are used as criteria when finding the candidate cells:

• DL CPICH Ec/No of the candidate cell does not have to be inside of the window (determined by the HSDPAServCellWindow parameter) to change serving HS-DSCH cell. This is because in this case it is better to allocate any cell than to switch to DCH.
  The DL CPICH Ec/No measurements used to both select the new serving HS-DSCH cell and define the priority order of the candidate cells are taken from the reported measurement event 1B or 1C, depending on which measurement initiated the cell change.
• If the level of UL SIR_error triggers the change, UL SIR_error of the target cell must be above or equal to the threshold determined by the HSDPASIRErrorTargetCell operator management parameter to allocate HS-DSCH. With other triggers it is enough that the UL SIR_error of the target cell is above or equal to the threshold determined by theHSDPASIRErrorServCell operator management parameter to allocate HS-DSCH. The UL SIR_error trigger is valid only in the case of the inter-BTS serving cell change. UL SIR_error cannot trigger the intra-BTS serving cell change.
• If the UE uses a PS streaming RB, HSPA streaming has to be activated (HSPAQoSEnabled parameter) in the target cell, as well. If this condition is not fulfilled, the respective cell is therefore not selected as candidate cell.

When the cells that fulfil the UL SIR_error condition are found, the serving HS-DSCH selection is executed according to same priorities as when selecting the initial serving HS-DSCH cell.

If the serving HS-DSCH change to target cell fails, the other candidate cells are attempted. If similar failure occurs also for other candidate cells, the serving HS-DSCH cell is not changed. If the serving HS-DSCH cell cannot be kept, for example, because of low UL SIR_error or lost radio link, HS-DSCH is released and mapped to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch). If the release of HS-DSCH fails, the release is retried as long as the condition to perform the release remains.

The RNC sets a UE-specific guard timer after HS-DSCH MAC-d flow release to prevent immediate and recurring HS-DSCH allocations, when HS-DSCH MAC-d flow has been released due to any handover reason and the radio bearer is mapped onto DCH after release. HS-DSCH transport channel is not allowed to be allocated during the guard time period determined by the HsdschGuardTimerHOmanagement parameter.

The guard timer concerns the particular UE and it is effective in all the cells under the RNC. The restriction is effective for the UE in the CELL_DCH and CELL_FACH states. When the timer expires, HS-DSCH allocation is allowed to the particular UE again.

Limiting the number and interval of serving HS-DSCH cell changes

The operators can define the maximum number of allowed serving HS-DSCH cell changes (HSDPAMaxCellChangeRepetition parameter) within a desired time frame (HSDPACellChangeRepetitionTime parameter). If the number of serving HS-DSCH cell changes is exceeded within the configured time frame, the RNC releases the HS-DSCH and maps the RB to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch).

The operators can define the minimum interval between serving HS-DSCH cell changes caused by DL CPICH Ec/No reason (HSDPACellChangeMinInterval parameter ). While the timer is running, the RNC does not perform serving HS-DSCH cell change.

Inter-RNC mobility

The HSPA Inter-RNC Cell Change feature improves the end user performance by maintaining a high data rate HSPA service during intra-frequency inter-RNC mobility. Capacity gain is achieved at the cells of the RNC border area when HSPA instead of DCH can be utilized. In the case of CS AMR speech multi-service, direct switch to DCH is applied in order to guarantee strict quality and delay requirements for the speech. Both HSDPA and HSUPA are covered by this chapter.

When intra-frequency measurements indicate that the strongest cell in the active set is located under the DRNC, HSPA intra-frequency inter-RNC cell change is performed. Triggering point for inter-RNC cell change can be specifically defined by the operator by means of the management parameters.

HSPA intra-frequency inter-RNC cell change utilizes SRNS relocation with UE involvement, that is, the UE is reconfigured according to the resources of the target RNC during SRNS relocation.

Target RNC allocates resources on a best effort basis, that is, even though HSPA is primarily allocated, also DCH/DCH can be allocated in case HSPA is not available. Source RNC deletes the old configuration after a successful SRNS relocation. HSPA serving cell change (serving HS-DSCH/E-DCH cell change) is combined with an inter-RNC cell change.

HSPA data flow is not established over Iur-interface but HSPA resources are reserved and allocated under DRNC in conjunction with the SRNS relocation. Associated DCH (signalling link) and uplink DCH return channel can be set up over Iur-interface, whereas HS-DSCH and E-DCH are not allowed over Iur-interface. HSPA Inter-RNC cell change is supported also when Iur-interface is disabled, congested or not existing.

Figure Situation prior to HSPA inter-RNC cell change below illustrates the situation prior to HSPA inter-RNC cell change. In this figure, the active set contains three cells. Two cells are located under SRNC and one cell under DRNC. Serving HSPA cell is located under SRNC. Associated DCH is transmitted and received via each cell in the active set. The functionality depends on the type of the allocated uplink transport channel. Either E-DCH or DCH can be allocated. Should E-DCH be allocated in uplink direction, DRNC cell is excluded from the E-DCH active set, that is, E-DCH non serving radio link is not allocated over Iur-interface. Should DCH be allocated in uplink direction, DCH is transmitted and received via each cell in the active set. Both of these scenarios are illustrated in the below.

Figure Situation after successful HSPA inter-RNC cell change below illustrates the situation after a successful HSPA inter-RNC cell change. In this figure, a HSPA inter-RNC Cell Change has successfully been performed. Source RNC has deleted the old configuration and DRNC has established new HSPA resources.

Figure 32:

Situation prior to HSPA inter-RNC cell change

Figure 33:

Situation after successful HSPA inter-RNC cell change

The functionality of the HSPA intra-frequency inter-RNC cell change depends on the value of the parameter HSPAInterRNCMobility.

HSPAInterRNCMobility parameter may have three different values:

• (0) Disabled
  This value means that the feature is inactive.
• (1) Enabled without E-DCH trigger
  This value means that the feature is active but an unacceptable E-DCH active set does not trigger an HSPA inter-RNC cell change.
• (2) Enabled
  This value means that the feature is active and an unacceptable E-DCH active set triggers an HSPA inter-RNC cell change.

HSPA intra-frequency inter-RNC cell change is only applied if the HSDPA Serving Cell Change and HSDPA Soft/Softer Handover for Associated DPCH features are enabled. In other words, the HSDPAMobility parameter has to be set to ‘Enabled’. HSPA Inter-RNC cell change from source RNC to target RNC is performed by means of the ‘UE involved’ SRNS relocation procedure.

SRNC supports HSPA inter-RNC cell change only if the HSPAInterRNCMobility parameter is set to 'Enabled' or 'Enabled without E-DCH trigger'. If the parameter is set to ‘Disabled’, HSPA Inter-RNC cell change is not supported but SRNC applies a switch from HSPA to DCH at the RNC border. If the value of the parameter HSPAInterRNCMobility is changed online, current RRC connections are not affected. Instead, the new value will become effective only for new RRC connections in Cell_DCH state.

DRNC, which is the target RNC for ‘UE involved’ SRNS relocation procedure, supports HSPA inter-RNC cell change. DRNC ignores HSDPAMobility and HSPAInterRNCMobilityparameters in conjunction with the HSPA inter-RNC cell change. DRNC also ignores state of the licence of the HSPA Inter-RNC cell change feature.

The source RNC checks the 3GPP release version of the target RNC. If the 3GPP release version of the target RNC does not support HS-DSCH or/and E-DCH, SRNC executes a switch to DCH/DCH instead of starting a HSPA inter-RNC cell change.

Figure 34:

HSPA inter-RNC cell change

Serving cell selection

This section deals with the initial selection of the serving cell, the serving cell change, the UL SIR error measurement, and other serving cell change reasons.

Initial selection of the serving cell

The SRNC initially selects the serving HSPA cell from those SRNC cells which belong to the active set. If either no cells exist under the SRNC or if HSPA allocation — either HS-DSCH/E-DCH or HS-DSCH/DCH — is not possible in any cell under SRNC, HSPA allocation is prevented. DRNC cell is not chosen as a serving HSPA cell at the initial selection of the serving HSPA cell phase.

Initial selection of the serving HSPA cell follows the existing principles as described in the chapter HSDPA mobility handling with the Serving HS-DSCH Cell Change except for the following special condition:

Currently the following condition is effective for the initial selection of the serving cell.

Figure 35:

Condition for selecting the candidate cells

CPICHEc/NoCell is the CPICH Ec/No measurement of the candidate cell, CPICHEc/NoBest_cell is the CPICH Ec/No measurement of the best cell in the active set andHSDPAServCellWindow is the parameter that determines the window inside of which the serving cell must be.

However, if all conditions described below are true, SRNC ignores the condition in the equation Condition for selecting the candidate cells when initially selecting the serving HSPA cell. If any of the subsequent conditions is false, initial selection of the serving HSPA cell is performed only according to the existing principles, which means that the SRNC takes the condition in the equation Condition for selecting the candidate cells into account.

• HSPAInterRNCMobility parameter is set to 'Enabled' or 'Enabled without E-DCH trigger' under SRNC
• AMR CS speech RAB is not simultaneously established
• PS streaming RAB is not simultaneously established
• Both SRNC (CN) and DRNC support SRNS relocation
• There is at least one HSPA capable cell under SRNC and at least one cell under DRNC in the active set
• The best cell in terms of reported CPICH Ec/No is located under DRNC

Serving cell change

SRNC selects the new serving HSPA cell from those SRNC and DRNC cells which belong to the active set. If SRNC decides to select a DRNC cell as the new serving HSPA cell, SRNC initiates an intra-frequency inter-RNC cell change by using the ‘UE involved’ SRNS relocation procedure. If SRNC decides to select an SRNC cell as new serving HSPA cell, however, the existing serving HSPA cell change principles are followed as described in HSDPA mobility handling with the Serving HS-DSCH Cell Change.

HSPA inter-RNC cell change can be performed if the following conditions are effective:

• HSPAInterRNCMobility parameter is set to 'Enabled' or 'Enabled without E-DCH trigger' under SRNC
• AMR CS speech RAB is not simultaneously established
• PS streaming RAB is not simultaneously established
• Both SRNC (CN) and DRNC supports SRNS relocation
• There is at least one cell under DRNC in the active set

Basic difference between the traditional intra-RNC serving HSPA cell change and the HSPA inter-RNC cell change is the following: if SRNC selects the DRNC cell as a new serving cell, ‘UE involved’ SRNS relocation is started instead of the traditional serving cell change

Each DRNC cell which fulfils both of the following conditions can be selected as candidate cell for the serving HSPA cell change:

Figure 36:

Comparison to the best cell

Figure 37:

Comparison to the existing serving cell

CPICH_Ec/NoCell is the CPICH Ec/No measurement of the DRNC candidate cell, CPICH_Ec/NoBest_cell is the CPICH Ec/No measurement of the best cell in the active set andCPICH_Ec/NoServ_cell is the CPICH Ec/No measurement of the current serving HSPA cell.

The HSDPAServCellWindow parameter defines the range in which the serving cell's CPICH Ec/No measurement has to be. The HSPADRNCEcNoOffset parameter defines an offset deducted from the CPICH Ec/No measurement result of the DRNC cell.

If more than one candidate cell for the serving HSPA cell change has been detected and the candidate cells are to be prioritized, HSPADRNCEcNoOffset is taken into account when deciding the priority order of the cells. This means that HSPADRNCEcNoOffset is deducted from the CPICH Ec/No measurement of the DRNC cell.

Repetitive HSPA inter-RNC cell changes are prevented by using higher thresholds for triggering the new HSPA inter-RNC cell change during the guard time period after successful HSPA inter-RNC cell change.

The SRNC (target RNC, which has started to operate as a new SRNC after SRNS relocation) sets the timer "HSPA inter-RNC cell change prevention timer". The value of the timer is fixed to 10 s. As long as the timer "HSPA inter-RNC cell change prevention timer" is running, the SRNC applies higher thresholds for triggering the HSPA inter-RNC cell change. SRNC adds an additional offset "HSPA inter-RNC cell change prevention offset" to the value of the management parameter HSPADRNCEcNoOffset. The value of the additional offset is fixed to 1 dB.

Target RNC for ‘UE involved’ SRNS relocation performs a channel type selection and sets up the HSPA resources. The basic principle is that the target RNC allocates the best possible configuration for PS RAB in conjunction of the SRNS relocation.

• If PS RAB (without multi-RAB) was established in the source RNC before the SRNS relocation, the target RNC executes a channel type selection procedure in order to allocate either HSPA or DCH resources for the PS RAB.
• When multiple NRT RABs are supported by HSPA (see RAB combinations for HSDPA), HSPA inter-RNC cell change can be started. The following cases have to be distinguished:
  • Whenever multiple NRT RABs are combined with AMR or PS Streaming or both, however, channel type switching from HSPA to DCH is performed.
  • HSPA inter-RNC cell change is not applied if the UE has a streaming RB mapped to the HS-DSCH.
    In this case, the new serving cell is not selected under the DRNC. Instead, if the new serving cell cannot be found under the SRNC and the old cell cannot be kept, channel type switch to DCH is performed.

Primarily, DL HS-DSCH and UL E-DCH allocations are attempted. If HS-DSCH and E-DCH allocation fails due to BTS or transport congestion, DCH / DCH initial bit rate is attempted directly (no HS-DSCH / UL DCH attempt). Secondarily, DL HS-DSCH and UL DCH is attempted. If neither of the previous alternatives is successful, the target RNC allocates DL DCH and UL DCH for the PS RAB. Initial bit rate is allocated to the HSDPA UL DCH return channel or DL DCH / UL DCH. If the target RNC cannot allocate any user plane resources, which implies that the target RNC cannot allocate any other resources than SRB DCH (signalling link), SRNS relocation (HSPA inter-RNC cell change) is rejected.

UL SIR error measurement

SRNC starts the UL SIR error measurement for the SRNC cells according to the existing principles as described in the chapter Setting up the DL CPICH Ec/No and UL SIRerrormeasurements. UL SIR error measurement is not started for DRNC cells but for SRNC cells only.

Since the UL SIR error measurement is not received from the DRNC, this measurement is not taken into account as serving HSPA cell change criterion for DRNC cells. As a consequence, prioritization and selection of the DRNC candidate cells are based on the periodically reported CPICH Ec/No measurements only.

RNC offset is applied in the case of HSPA inter-RNC cell change. DRNC offset is defined by the parameter HSPADRNCSIRErrorOffset. SRNC applies HSPADRNCSIRErrorOffsetwhen the UL SIR error measurement triggers a serving HSPA cell change.

If the periodically reported UL SIR error measurement of the current serving HSPA cell (BTS) is below the threshold determined by the HSDPASIRErrorServCell parameter, this measurement result triggers a serving HSPA cell change. In this case, the following procedure is applied:

• If an applicable cell is allocated under DRNC and if the serving HSPA cell change cannot be performed, HS-DSCH/E-DCH MAC-d flow is not released. Instead the HSPA transport channels remain connected.
• A direct switch from HSPA to DCH, that means HS-DSCH/E-DCH MAC-d flow is released and RB mapped onto DCH, is applied only when the following conditions apply:
  • The UL SIR error measurement of the current serving HSPA cell (BTS) goes below the threshold determined by the parameter HSDPASIRErrorServCell deducted by the offset HSPADRNCSIRErrorOffset.
  • The serving HSPA cell change still cannot be performed.

Other serving cell change reasons

HSPA inter-RNC cell change can also be started due to following reasons:

• Measurement event 1B or 1C initiates HSPA inter-RNC cell change if the serving HSPA radio link is to be deleted from the active set, and if the selected candidate cell is located under DRNC.
• The serving HSPA radio link is to be removed from the active set due to other reasons:
  • Radio link failure of the serving HS-DSCH/E-DCH radio link (loss of UL synchronization).
  • Radio link removal due to Rx-Tx time difference.

The selection of the serving cell in the above mentioned cases follows the principles described previously in this chapter.

RNC checks if the E-DCH active set changes to unacceptable as described in WCDMA RAN RRM HSUPA functional area description. If the E-DCH active set changes to unacceptable, SRNC initiates a HSPA inter-RNC cell change instead of E-DCH to DCH switch provided:

• HSPAInterRNCMobility management parameter is set to (2) 'Enabled'
• Non E-DCH cell is located under DRNC when evaluating acceptability of the E-DCH active set.

Motivation is to avoid E-DCH to DCH switch due to an unacceptable E-DCH active set, which would immediately be followed by the HSPA inter-RNC cell change. If the management parameter HSPAInterRNCMobility is set to (0) 'Disabled' or (1) 'Enabled without E-DCH trigger', unacceptable E-DCH active set does not initiate HSPA inter-RNC cell change.

Iur-interface disabled

Allocation of the associated SRB DCH (and UL DCH return channel if applicable) under DRNC fails if both an HS-DSCH (and E-DCH) MAC-d flow is set up in the SRNC and the SHO branch setup over the Iur-interface fails. In this case, SRNC may initiate an HSPA inter-RNC cell change which is triggered in a similar way as the existing intra-frequency inter-RNC HHO triggering. For details about the existing intra-frequency inter-RNC HHO triggering, refer to the WCDMA RAN RRM Handover Control FAD. In order to initiate HSPA inter-RNC cell change, the following conditions must then be effective:

• HSPAInterRNCMobility parameter is set to 'Enabled' or 'Enabled without E-DCH trigger' under SRNC
• AMR CS speech RAB is not simultaneously established
• PS streaming RAB is not simultaneously established
• Both SRNC (CN) and DRNC supports SRNS relocation

The handover decision made by the SRNC is based on the DL CPICH Ec/No of the best active set cell (EcNoDownlink), DL CPICH Ec/No of the neighboring cell (EcNoNcell) and handover margins. Because RNC is not able to add the requested DRNC cell into the active set, the UE proceeds to periodic measurement reporting. The measurement results of the neighboring DRNC cell must satisfy either of the following equations (1) or (2) before the HSPA inter-RNC cell change can be initiated:

1.	AveEcNoDownlink + HHoMarginAverageEcNo(n) < AveEcNoNcell(n)
2.	EcNoDownlink + HHoMarginPeakEcNo(n) < EcNoNcell(n)

AveEcNoDownlink is the averaged DL CPICH Ec/No of the best active set cell. AveEcNoNcell(n) is the averaged DL CPICH Ec/No of the neighboring DRNC cell (n). RNC calculates the averaged values from a specified number of periodical event-triggered intra-frequency measurement reports. The averaging window is controlled by the existing management parameter EcNoAveragingWindow.

The parameter HHoMarginAverageEcNo(n) determines the maximum allowed difference between the averaged CPICH Ec/No of the neighboring DRNC cell (n) and the averaged CPICH Ec/No of the best active set cell. The parameter HHoMarginPeakEcNo(n) determines the maximum allowed difference between the CPICH Ec/No of the neighbouring DRNC cell (n) and the CPICH Ec/No of the best active cell.

SRNC uses the parameters from the HSDPA-specific parameter sets in decision making. In the case of AMR multi-service, SRNC uses the parameters from the RT+HSDPA specific parameter sets.

In the case of AMR multi-service, HSPA inter-RNC cell change is not allowed, but HSPA to DCH switch is performed before intra-frequency inter-RNC cell change can be started.

HSDPA inter-frequency handover

Based on inter-frequency handover (IFHO) triggers, the RNC orders compressed mode on HSDPA so that inter-frequency measurements can be performed on HSDPA without channel type switching to DCH. Thus, high HSDPA throughput can be experienced during compressed mode and the total handover execution time is reduced up to 1.5 s.

The following changes in the channel type are supported during HSDPA inter-frequency handover:

• DCH/HSDPA to DCH/HSDPA
• DCH/HSDPA to HSUPA/HSDPA
• DCH/HSDPA to DCH/DCH
• DCH/DCH to DCH/HSDPA
• DCH/DCH to HSUPA/HSDPA

Inter-frequency handover is triggered due to coverage and quality reasons, but also IMSI based handover and HSPA capability based handover can be initiated. The RNC selects the target cell according to the measurement results and performs inter-frequency handover along with HSDPA serving cell change. The target cell can be an intra- or inter-RNC cell depending on the defined neighboring cells.

This feature enables also inter-frequency handover directly to HSUPA/HSDPA, even if the handover is started from DCH. If the HSDPA allocation is not possible in the target cell, handover is performed to DCH. Channel type switching to DCH or FACH may be performed during compressed mode, for example if the active set is updated or inactivity is detected.

For details about HSDPA inter-frequency handover, see the WCDMA RAN RRM Handover Control functional area description.

Measurement control and handover path parameters

This chapter is common for both values of HSDPAMobility.

The HSDPA coverage can be maximized by defining separate measurement control and handover path parameters for UEs that support HSDPA. These HSDPA-specific parameter sets are sent with the RRC: MEASUREMENT CONTROL when a HS-DSCH transport channel is allocated.

When users have established only PS RABs (one or more) having HS-DSCH transport channel allocated, a particular parameter set is associated with the HSDPA UE by the identifiers:

• HSDPAFmcsIdentifier (intra-frequency measurement control)
• HSDPAFmciIdentifier (inter-frequency measurement control)
• HSDPAFmcgIdentifier (inter-system measurement control)
• HSDPAHopsIdentifier (intra-frequency handover path)

When AMR speech CS RAB is established simultaneously (possible when AMRWithHSDSCH parameter is enabled) with PS RABs (one or more) having HS-DSCH transport channel allocated, a particular parameter set is associated with the HSDPA UE by the identifiers:

• RTWithHSDPAFmcsIdentifier (intra-frequency measurement control)
• RTWithHSDPAFmciIdentifier (inter-frequency measurement control)
• RTWithHSDPAFmcgIdentifier (inter-system measurement control)
• RTWithHSDPAHopsIdentifier (intra-frequency handover path)

The following tables list the contents of the parameter sets that will be dedicated to the UE that has a HS-DSCH allocated.

See the following notes in the tables:

*)	Available for a single NRT PS RAB (HS-DSCH), multi NRT PS RABs (HS-DSCH), and PS streaming RAB when HSDPAMobility disabled.
**)	Available for a single NRT PS RAB (HS-DSCH), multi NRT PS RABs (HS-DSCH), and PS streaming RAB when HSDPAMobility enabled.
***)	Available for an AMR + HSDPA multi-service and for AMR + multi NRT RABs (HS-DSCH) and for AMR + PS streaming RAB (HS-DSCH) whenHSDPAMobility disabled.
****)	Available for an AMR + HSDPA multi-service and for AMR + multi NRT RABs (HS-DSCH) and for AMR + PS streaming RAB (HS-DSCH) whenHSDPAMobility enabled.

FMCS parameter name	Availability
Addition Window (1A)	*), **), ***), ****)
Addition Time (1A)	*), **), ***), ****)
Addition Reporting Interval (1A)	*), **), ***), ****)
Drop Window	**), ****)
Drop Time	**), ****)
Replacement Window	**), ****)
Replacement Time	**), ****)
Replacement Reporting Interval	**), ****)
Maximum Active Set Size	**), ****)
CPICH Ec/No Filter Coefficient	*), **), ***), ****)
Active Set Weighting Coefficient	**), ****)
CPICH Ec/No HHO Cancellation (1E)	*), **), ***), ****)
CPICH Ec/No HHO Cancellation Time (1E)	*), **), ***), ****)
CPICH Ec/No HHO Threshold (1F)	*), **), ***), ****)
CPICH Ec/No HHO Time Hysteresis (1F)	*), **), ***), ****)
CPICH RSCP HHO Cancellation (1E)	*), **), ***), ****)
CPICH RSCP HHO Cancellation Time (1E)	*), **), ***), ****)
CPICH RSCP HHO Filter Coefficient	*), **), ***), ****)
CPICH RSCP HHO Threshold (1F)	*), **), ***), ****)
CPICH RSCP HHO Time Hysteresis (1F)	*), **), ***), ****)
IMSI based HO	N/A

Table 7:

Intra-frequency measurement control (FMCS) parameters

FMCI parameter name	Availability
IFHO caused by CPICH Ec/No	*), **), ***), ****)
IFHO caused by CPICH RSCP	*), **), ***), ****)
IFHO caused by DL DPCH TX Power	***), ****)
IFHO caused by UE TX Power	*), **), ***), ****)
IFHO caused by UL DCH Quality	*), **), ***), ****)
DL DPCH TX Power Threshold for AMR	***), ****)
Maximum Measurement Period	***), ****)
Measurement Averaging Window	***), ****)
Measurement Reporting Interval	***), ****)
Minimum Interval Between IFHOs	***), ****)
Minimum Measurement Interval	***), ****)
Neighbour Cell Search Period	***), ****)
UE TX Power Filter Coefficient	*), **), ***), ****)
UE TX Power Threshold for AMR	***), ****)
UE TX Power Threshold for NRT PS	*), **)
Minimum Interval Between IF SLHOs	N/A
IMSI Based IFHO	N/A

Table 8:

Inter-frequency measurement control (FMCI) parameters

FMCG parameter name	Availability
GSM HO caused by CPICH Ec/No	*), **), ***), ****)
GSM HO caused by CPICH RSCP	*), **), ***), ****)
GSM HO caused by DL DPCH TX Power	***), ****)
GSM HO caused by UE TX Power	*), **), ***), ****)
GSM HO caused by UL DCH Quality	*), **), ***), ****)
DL DPCH TX Power Threshold for AMR	***), ****)
Maximum Measurement Period	***), ****)
Measurement Averaging Window	***), ****)
Measurement Reporting Interval	***), ****)
Minimum Interval Between Hos	***), ****)
Minimum Measurement Interval	***), ****)
GSM Neighbour Cell Search Period	***), ****)
UE TX Power Filter Coefficient	*), **), ***), ****)
UE TX Power Threshold for AMR	***), ****)
UE TX Power Threshold for NRT PS	*), **)
IMSI based GSM HO	N/A
Minimum Interval Between IS SLHOs	N/A

Table 9:

Inter-system measurement control (FMCG) parameters

HOPS parameter name	Availability
HHO Margin for Average Ec/No	Not relevant
HHO Margin for Peak Ec/No	Not relevant
Release Margin for Average Ec/No	*), **), ***), ****)
Release Margin for Peak Ec/No	*), **), ***), ****)
CPICH Ec/No Averaging Window	*), **), ***), ****)
Enable RRC Connection Release	*), **), ***), ****)
Enable Inter-RNC Soft Handover	**), ****)

Table 10:

Intra-frequency cell re-selection and handover path control parameters (HOPS)

For details about parameters in parameter sets, see Management data for handover control.

HSDPA cell reselection

Setting the HSDPAMobility parameter to 'disabled' activates the HSDPA cell reselection and mobility handling with DCH switching.

HSDPA cell reselection applies transition to the CELL_FACH state, triggered by the measurement event 1A, when UE enters soft handover coverage area. HSDPA mobility handling with DCH switching applies DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch) allocation based on the measurement events 1F and 6A. Also, UL DCH quality deterioration report can be used to control HSDPA mobility. Additionally, in the case of an AMR multi-service, DL Transmitted Code Power measurement is used as a trigger to initiate inter-frequency measurements. HS-DSCH MAC-d flow is released before transition to the CELL_FACH state or allocation of DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch) kbit/s. However, if the HSDPA Inter-Frequency Handover optional feature is activated and inter-frequency handover triggers are present, HS-DSCH release is not triggered. Instead, an E-DCH to DCH switch in uplink is performed if needed and interfrequency-handover measurement is started after that immediately with DL: HS-DSCH/UL: DCH configuration. For more details, see HSDPA inter-frequency handover.

Figure 38:

Mobility handling when UE moves from cell to cell

The figure above displays the principle of mobility handling with HSDPA cell reselection.

Intra-frequency mobility for the HSDPA users is implemented via CELL_FACH RRC state (HSDPA cell reselection). Based on the intra-frequency CPICH Ec/No measurement reports (Event 1A) from UE, RNC decides to transfer the UE to the CELL_FACH state when UE enters SHO coverage area.

HS-DSCH MAC-d flow is released and UE is transferred to the CELL_FACH state in the target cell (Cell B). Direction to the target cell can be performed under the serving RNC. The target cell corresponds with the cell, which initiated the measurement event 1A. Therefore, UE does not need to execute the Cell Update procedure and HS-DSCH can be reallocated immediately based on the data volume in accordance with the channel type selection procedure (see chapter HSDPA channel type selection).

Measurement reporting

The measurement reporting events in the table below are applied to the HSDPA mobility functionalities including HSDPA cell reselection, which is based on the measurement event 1A and channel type switching to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch) kbit/s, which, in turn, is based on the measurement events 1F and 6A.

Event	Description
1A	A primary CPICH enters the reporting range.
1F	A primary CPICH goes below the absolute threshold.
1E	A primary CPICH becomes better than an absolute threshold (cancels 1F)
6A	UE Tx power exceeds the absolute threshold.
6B	UE Tx power becomes less than an absolute threshold (cancels 6A)

Table 11:

The events that trigger channel type switching

The quality deterioration report also triggers the HS-DSCH MAC-d flow release and allocation of DCH X/X (0/0 or initial bit rates, see Direct HS-DSCH to DCH switch) kbit/s.

A UE with a HS-DSCH transport channel allocated can have only one cell in the active set at a time, that is, the size of the active set is limited to one. Because of this, the RNC does not add cells to the active set based on reporting event 1A when a HS-DSCH transport channel is allocated to the UE, but utilizes event 1A as a trigger for HS-DSCH MAC-d flow release and transition to the CELL_FACH state. An example is presented in the figure below.

Figure 39:

Example of triggering based on reporting event 1A

In the figure above, P-CPICH 1 is the serving HS-DSCH cell and the only cell in the active set. P-CPICH 2 and P-CPICH 3 are monitored set cells, which do not belong to the active set. If P-CPICH 2 is equal to the serving HS-DSCH cell (the assumption being that the intra-frequency measurement control parameter AdditionWindow is set to 0 dB and the parameter EnableRRCrelease is set to disabled), the UE sends measurement reporting event 1A. When the RNC receives event 1A, HS-DSCH MAC-d flow is released and the UE is transferred to the CELL_FACH state.

The HS-DSCH to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch) kbit/s channel type switching after HS-DSCH MAC-d flow release is performed in the case of inter-frequency or inter-RAT handovers. The actual triggers for the channel type switching before handovers are measurement reporting events 1F and 6A. In the case of an AMR multi-service, DL Transmitted Code Power measurement is also used as a trigger to initiate inter-frequency measurements. However, if the HSDPA Inter-Frequency Handoveroptional feature is activated and inter-frequency handover triggers are present, HS-DSCH release is not triggered. Instead, an E-DCH to DCH switch in uplink is performed if needed and interfrequency-handover measurement is started after that immediately with DL: HS-DSCH/UL: DCH configuration. For more details, see HSDPA inter-frequency handover.

If the HSDPA Inter-Frequency Handover optional feature is not activated, the functionality depends on the triggered measurement and the value of the intra-frequency handover path parameter EnableRRCrelease as specified below:

Measurement event 1A triggered HS-DSCH MAC-d flow release and parameter EnableRRCrelease is disabled:

In the case of PS RABs without AMR CS RAB and without PS streaming RAB, HS-DSCH MAC-d flow is released. The UE is transferred to the CELL_FACH state and the radio bearer is mapped to the FACH by using the RRC: Radio bearer reconfiguration procedure.

In the case of an AMR multi-service or PS streaming, after HS-DSCH MAC-d flow has been released and DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch) kbit/s allocated, the active set is updated immediately. The update is based on the same measurement event 1A, which caused triggering of HS-DSCH MAC-d flow release if the value of the RTWithHSDPA -specific parameter AdditionWindow is smaller than or equal to the RT-specific value of the AdditionWindow. After the active set update, UE measurements are restarted with DCH parameters and the received capacity requests are scheduled.

In the case of an AMR multi-service or PS streaming, if the value of the RTWithHSDPA -specific AdditionWindow parameter is greater than the RT-specific value, the active set is not updated. However, UE measurements are restarted with DCH parameters and the received capacity requests are scheduled.

If the HS-DSCH MAC-d flow release is unsuccessful in this case, HS-DSCH release is retried as long as measurement event 1A is effective.

Measurement event 1A triggered HS-DSCH MAC-d flow release and parameter EnableRRCrelease is enabled:

For users that have another transport channel than HS-DSCH allocated, the EnableRRCRelease parameter of the intra-frequency handover path indicates whether the RRC connection release (excluding emergency calls) is allowed due to non-optimum fast closed loop power control.

For users that have a HS-DSCH transport channel allocated, the parameter has a different meaning. If the RNC receives measurement event 1A and the EnableRRCReleaseparameter is enabled, it does not allow the HS-DSCH MAC-d flow release to be directly triggered.

When a cell has entered the reporting range and triggered event 1A and the RNC has not added the cell into the active set, the UE reverts to periodical reporting. This means that the UE continues reporting after the initial report by switching to the periodical measurement-reporting mode.

As the EnableRRCRelease parameter is enabled, the RNC’s decision on HS-DSCH MAC-d flow release is based on the CPICH Ec/No of the serving cell (EcNoDownlink), CPICH Ec/No of the neighbouring cell (EcNoNcell), and the ReleaseMarginAverageEcNo and ReleaseMarginPeakEcNo control parameters.

Based on the periodical measurement reporting mode and the control parameters, the UE is transferred to the CELL_FACH state and the radio bearer is mapped to the FACH by using the RRC: Radio bearer reconfiguration procedure if either of the following conditions is effective:

1.	EcNoDownlink + ReleaseMarginPeakEcNo(n) < EcNoNcell(n)
2.	AveEcNoDownlink + ReleaseMarginAverageEcNo(n) < AveEcNoNcell(n)

If the HS-DSCH MAC-d flow release is unsuccessful, the RRC connection is released.

In the case of an AMR multi-service or PS streaming, the HS-DSCH MAC-d flow is released and the RB is mapped to DCH X/X (0/0 or initial bit rates, see Direct HS-DSCH to DCH switch). When DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch) kbit/s has been allocated, the active set is updated immediately. After a successful active set update, the UE measurements are restarted with DCH parameters and the received capacity requests are scheduled.

Measurement event 1F or 6A triggered HS-DSCH MAC-d flow release (with PS RAB):

In the case of a PS RAB without AMR CS RAB when DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch) kbit/s has been allocated, IFHO/ISHO measurements are not directly started. Instead, UE measurements are restarted with DCH parameters and the received capacity requests are scheduled.

If the HS-DSCH MAC-d flow release is unsuccessful, the HS-DSCH release is retried as long as cancelling measurement event (1E/6B) has not been received.

Measurement event 1F triggered HS-DSCH MAC-d flow release (with AMR multi-service):

In the case of an AMR DCH multi-service, HS-DSCH MAC-d flow is released and the PS RB is mapped to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch). After the HS-DSCH MAC-d flow release, IFHO/ISHO measurements for the AMR are started.

If the HS-DSCH MAC-d flow release is unsuccessful, the release is retried as long as cancelling measurement event (1E) has not been received.

Measurement event 6A triggered HS-DSCH MAC-d flow release (with AMR multi-service):

In the case of an AMR DCH multi-service, HS-DSCH MAC-d flow is released and the PS RB is mapped to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch). After a successful HS-DSCH MAC-d flow release, the measurement control for the AMR is restarted. IFHO/ISHO measurements are not started directly afterwards; a new triggering is needed.

If the HS-DSCH MAC-d flow release is unsuccessful, the release is retried as long as cancelling measurement event (6B) has not been received.

DL Transmitted Code Power triggered HS-DSCH MAC-d flow release (AMR multi-service):

In the case of an AMR DCH multi-service, HS-DSCH MAC-d flow is released and the PS RB is mapped to DCH X/X (0/0 or initial bitrates, see Direct HS-DSCH to DCH switch). After a successful HS-DSCH MAC-d flow release, IFHO/ISHO measurements for the AMR are started.

If the HS-DSCH MAC-d flow release is unsuccessful, the release is retried.

Diversity handover of stand-alone signalling link

This chapter is valid when the HSDPAMobility parameter is set to disabled, that means when serving HS-DSCH cell change and soft handover of the associated DPCH are not supported.

If the active set size is greater than one, allocation of a HS-DSCH transport channel to the UE is prohibited.

• The operators can disable diversity handover of the RRC connection (stand-alone signalling link) of an HSDPA-capable UE with the HSDPARRCdiversity parameter in order to maximise HS-DSCH usage.

The HSDPARRCdiversity parameter value is checked immediately after a successful RRC connection setup procedure. If the SHO of the RRC connection (stand-alone signalling link) of the HSDPA-capable UE is not allowed, the active set size is limited to one for the RRC connection. Restriction is effective after an RRC-connection establishment when SRB only or SRB and DCH 0/0 is/are allocated.

Exception

The RNC ignores the parameter value (and allows diversity handover of stand-alone signalling link) if measurement event 1A is received and the reported CPICH Ec/No of the entering cell meets either of the following conditions (that is, the threshold to perform HS-DSCH to CELL_FACH transition is exceeded):

1.	EcNoDownlink + ReleaseMarginPeakEcNo(n) < EcNoNcell(n)
2.	AveEcNoDownlink + ReleaseMarginAverageEcNo(n) < AveEcNoNcell(n)

EcNoDownlink refers to the CPICH Ec/No of the serving cell and EcNoNcell(n) refers to the CPICH Ec/No of the entering cell. AveEcNoDownlink is the averaged CPICH Ec/No of the serving cell and AveEcNoNcell(n) is the averaged CPICH Ec/No of the entering cell.

The comparison is applied when a cell has entered the reporting range and triggered event 1A, and the RNC has not added the cell into the active set. In this case, the UE reverts to periodical reporting and continues reporting after the initial report by switching to the periodical measurement-reporting mode.

ReleaseMarginPeakEcNo(n) determines the maximum allowed difference between the CPICH Ec/No of the entering cell (n) and the CPICH Ec/No of the serving cell in order to not execute active set update.

ReleaseMarginAverageEcNo(n) determines the maximum allowed difference between the averaged CPICH Ec/No of the entering cell(n) and the averaged CPICH Ec/No of the serving cell correspondingly.

The HSDPA-specific HOPS parameters are used in the equation.

Service and load-based handover

The following restrictions with regards to the service- and load-based handovers are effective for the HSDPA capable UE:

• Service- and load-based handovers are not applied to the UE with HS-DSCH MAC-d flow set up
• Service- and load-based handovers are not applied to the HSDPA-capable UE with NRT DCH greater than 0 kbit/s and/or PS streaming DCH greater than 0 kbit/s allocated when HSDPA is enabled in the cell.

Mobility handling during PS NRT RAB reconfiguration

Situations may occur in which a RAB modification procedure is ongoing (see PS NRT RAB reconfiguration) - it started, for example, immediately upon receipt of RANAP: RAB Assignment Request or capacity request from the UE, for example via RRC:Measurement Report message - when suddenly one or several trigger conditions for one or more HSDPA mobility procedures are received. If triggers for HSDPA mobility emerge during ongoing PS NRT RAB reconfigurations, the RNC normally suspends the mobility procedure.

Special cases:

• In contrast to that general approach, SRNS relocation and hard handovers override however ongoing RAB modifications and start immediately.
• Changes of the serving cell are not initiated before the RAB configuration is completed because old Iub connections from the serving cell change are removed. The same applies when RAB reconfiguration triggers are received during ongoing serving cell change. For the same reason, the serving cell change procedure has to be finished before the RAB modification can actually start.