The RNC periodically takes actions if the basic congestion is detected.
The following procedures apply to HSPA cells and R99 cells. For R99 cells, only DCH UEs are selected by LDR actions.
Whether the users of gold priority are selected by LDR actions is specified by the GoldUserLoadControlSwitch parameter.
When the cell is in the basic congestion state, the RNC takes one of the following actions in each period (specified by the LdrPeriodTimerLen parameter) until the congestion is relieved:
Inter-frequency load handover
Code reshuffling
BE service rate reduction
AMR rate reduction
Inter-RAT load handover in the CS domain, which involves the following actions:
− Inter-RAT Should Be Load Handover in the CS Domain
− Inter-RAT Should Not Be Load Handover in the CS Domain
Inter-RAT load handover in the PS domain, which involves the following actions:
− Inter-RAT Should Be Load Handover in the PS Domain
− Inter-RAT Should Not Be Load Handover in the PS Domain
Iu QoS renegotiation
MBMS power reduction
Figure 9-27 illustrates the detailed LDR procedure. In this example, the sequence of LDR actions is fixed to frequency load handover, code reshuffling, BE rate reduction, inter-RAT handover in CS domain, inter-inter-RAT handover in PS domain, AMR rate reduction, QOS renegotiation on Iu interface, and MBMS power reduction.
The sequence of LDR actions can be changed through the ADD CELLLDR command, and the waiting timer for LDR period is specified by the LdrPeriodTimerLen parameter through the SET LDCPERIOD command.
Issue Error! Unknown Error! Unknown document property 5 Figure 9-27 LDR procedure
Mark "current LDR state = uncongested"
Wait for congestion indication Congestion
state indication
Turn on the LDR algorithm switch
Current LDR state = congested?
Start sending the LDM congestion indication
Mark "current action = first LDR action"
Clear "selected" mark of all UE LDR actions
Keep the
"current action = first LDR action"
No LDR action is taken or all actions fail
No expiration of the timer Yes
Trigger the LDR period timer
As shown in Figure 9-27, when the system is congested, the inter-frequency load handover is initiated first.
If the handover succeeds, the algorithm continues to check whether the system is congested. If the system is still congested, the inter-frequency load handover is initiated again.
If the handover fails, code reshuffling is performed:
− If the code reshuffling succeeds, the algorithm continues to check whether the system is congested. If the system is still congested, the code reshuffling is initiated again.
− If the code reshuffling fails, the next action, that is, BE rate reduction, is taken.
The rest may be deduced by analogy. For details about LDR actions, see 9.3 "LDR Actions."
Table 9-15 describes the LDR actions intended for different resources.
Table 9-15 LDR actions intended for different resources Resource UL/DL Channel LDR Actions
Inter-Frequency Load Handover BE Rate Reduction Inter-RAT Handover in CS Domain Inter-RAT Handover in PS Domain AMR Rate Reduction Iu QoS Renegotiation Code Reshuffling MBMS Power Reduction
Power UL DCH √ √ √ √ √ √
HSUPA √ √
DL DCH √ √ √ √ √* √
HSDPA √ √
FACH (MBMS)
√*
Iub UL DCH √ √ √
HSUPA √
DL DCH √ √ √
HSDPA √
FACH (MBMS)
Code – –
DL DCH √ √ √
HSDPA FACH (MBMS)
Credit UL DCH √ √ √ √
HSUPA √ √
DL DCH √ √ √ √
HSDPA
Issue Error! Unknown Error! Unknown document property 7 Resource UL/DL Channel LDR Actions
Inter-Frequency Load Handover BE Rate Reduction Inter-RAT Handover in CS Domain Inter-RAT Handover in PS Domain AMR Rate Reduction Iu QoS Renegotiation Code Reshuffling MBMS Power Reduction
FACH (MBMS)
If the downlink power–based admission uses the ENU algorithm, the basic congestion can also be caused by the ENU. In this situation, LDR actions do not involve AMR rate reduction or MBMS power reduction, as indicated by the symbol "*" in Table 9-15.
For HSUPA services, the CE consumption, which is calculated on the basis of the Maximum Bit Rate (MBR), can be reduced through rate downsizing. Therefore, the BE service rate downsizing for HSUPA is applicable only to the relief of CE resource congestion.
If the basic congestion of uplink power in an HSPA cell occurs, scheduled HSUPA users cannot be selected by LDR actions.
The parameter CodeCongSelInterFreqHoInd can be set so that the inter-frequency handover can relieve the basic congestion caused by code resource.
When the inter-frequency load handover is made to reduce the cell load, only an inter-frequency neighboring cell that supports blind handover can be a target cell of the inter-frequency load handover.
The difference between the RAT Should Be Load Handover In the CS/PS Domain" and "Inter-RAT Should Not Be Load Handover In the CS/PS Domain" actions lies in the selection of users. The former only involves CS/PS users with the "service handover" IE set to "handover to GSM should be performed", while the latter only involves CS/PS users with the "service handover" IE set to
"handover to GSM should not be performed". For details about the "service handover" IE, see the Handover Parameter Description.