The WCDMA system is a self interference system. As the load of the WCDMA systemincreases, the interference rises. A relatively high interference may affect the coverageand Quality of Service (QoS) of established services. Therefore, capacity, coverage and
QoS of the WCDMA system are mutually affected. The purpose of load control is tomaximize the system capacity while ensuring coverage and QoS.
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1,Power ,include DL transmitting power of cell and increased UL interference (RTWP).
2,DL OVSF code of a cell3,DL and UL NodeB processing capability which is defined by NodeB credit.
4,Iub transmission bandwidth of a NodeB
The power resource is related to the mobility, distribution of the UE and also effected bythe radio conditions. Therefore, for a fixed power resource, the numbers of service canbe supported is not a fix result. We believe the UL and DL power resources are soft.
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z Maximizing system capacity while ensuring coverage and
QoS
z Realize different priorities for different service and different
user
WCDMA network load can be defined by 4 factors:
1,Power ,include DL transmitting power of cell and increased UL interference (RTWP).
2,DL OVSF code of a cell3,DL and UL NodeB processing capability which is defined by NodeB credit.
4,Iub transmission bandwidth of a NodeB
The power resource is related to the mobility, distribution of the UE and also effectedby the radio conditions. Therefore, for a fixed power resource, the numbers of servicecan be supported is not a fix result. We believe the UL and DL power resources aresoft.
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z The load control algorithms are applied to the different
UE access phases as follows:
PUC: Potential User Control CAC: Call Admission Control
IAC: Intelligent Admission Control LDB : Intra-frequency Load BalancingLDR: Load Reshuffling OLC: Overload Control
The load control algorithms are applied to the different UE access phases as follows:
Before UE access: Potential User Control (PUC)
During UE access: Intelligent Access Control (IAC) and Call Admission Control (CAC)After UE access: intra-frequency Load Balancing (LDB), Load Reshuffling (LDR), andOverload Control (OLC)
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Soft Load Measurement The major measurement objects of the load measurement
Received scheduled Enhanced Dedicated Channel (E-DCH)power share (RSEPS)
•
Uplink Received Total Wideband Power (RTWP)
UL Load
HSDPA GBP
HSDPA PBR
Non-HSPA TCPDL Load
TCP
E-DCH Provided Bit Rate
The soft load control algorithms use load measurement values in the uplink and thedownlink. A common Load Measurement (LDM) algorithm is required to control loadmeasurement in the uplink and the downlink.
The NodeB and the RNC perform measurements and filtering in accordance with theparameter settings. The statistics obtained after the measurements and filtering serveas the data input for the load control algorithms.
The major measurement objects of the LDM are as follows:
Uplink Received Total Wideband Power (RTWP)
•Received scheduled Enhanced Dedicated Channel (E-DCH) power share (RSEPS)
•E-DCH Provided Bit Rate
Downlink Transmitted Carrier Power (TCP)
TCP of all codes not used for High Speed Physical Downlink Shared Channel (HS-PDSCH), High Speed Shared Control Channel， (Non-HSPA TCP)
Provided Bit Rate on HS-DSCH (PBR)
HS-DSCH required power，also called Guaranteed Bit Rate (GBR) required power(GBP)
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Based on the measurement parameters set on the NodeB Local Maintenance Terminal(LMT), the NodeB measures the major measurement quantities and then obtainsoriginal measurement values. After layer 3 filtering on the NodeB side, the NodeBreports the cell measurement values to the RNC.Based on the measurement parameters set on the RNC LMT, the RNC performssmooth filtering on the measurement values reported from the NodeB and then obtainsthe measurement values, which further serve as data input for the load controlalgorithms.
Filtering on the NodeB Side
A is the sampling value of the measurement.
B is the measurement value after layer 1 filtering.
C is the measurement value after layer 3 filtering ,which is the reported measurementvalue
Layer 1 filtering is not standardized by protocols and it depends on vendor equipment.
Layer 3 filtering is standardized. The filtering effect is controlled by a higher layer.
The interval at which the NodeB reports each measurement quantity to the RNC isconfigured by the Time unit and Report cycle on RNC LMT: SET LDM
The report interval =Time unit * Report cycle
By default, Time unit for all measurement are set to 10ms ;Report cycle forRTWP is 100, that is 1s; Report cycle for TCP and Non HSPA TCP is 20 ,that is
200ms ;Report cycle for HSDPA GBP is 10, that is 100 ms; Report cyc le forHSDPA PBR is 10, that is 100 ms
Smooth Window Filtering on the RNC Side
After the RNC receives the measurement report, it filters the measurement valuewith the smooth window.
Assuming that the reported measurement value is Qn and that the size of thesmooth window is N, the filtered measurement value is :
Delay susceptibilities of PUC, CAC, LDB，LDR, and OLC to common measurementare different. The LDM algorithm must apply different smooth filter coefficients andmeasurement periods to those algorithms , on RNC LMT, we can set the smoothwindow length for different algorithms by SET LDM:
The following table lists the parameters :
251 to 32DlOLCAvgFilterLenDL OLC moving averagefilter length
251 to 32UlOLCAvgFilterLenUL OLC moving averagefilter length
31 to 32DlCACAvgFilterLenDL CAC moving averagefilter length
31 to 32UlCACAvgFilterLenUL CAC moving averagefilter length
251 to 32DlLdrAvgFilterLenDL LDR moving averagefilter length
251 to 32UlLdrAvgFilterLenUL LDR moving averagefilter length
321 to 32LdbAvgFilterLenLDB moving averagefilter length
321 to 32PucAvgFilterLenPUC moving averagefilter length
defaultValue
ValueRangeParameter IDParameter Name
Smooth window for GBP for all related algorithms are the same and the default setting is 1
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z The service of user with low priority will be affected by the
load control algorithms first
z Three kinds of priorities
User Priority
RAB Integrate Priority
User Integrate Priority
User Priority: mainly applying to provide different QoS for different users. Eg., settingdifferent GBR according to the user priority for BE service. No consideration about theservice.
RAB Integrate Priority: Priority of a service, related to the service type, and the userpriority of the user.
User Integrate Priority: Only used for multi-RAB user ,it is a temporary priority of anongoing-service user.
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gold (high), silver (middle) and copper (low) user
32kbps64kbps128kbpsUplink
CopperSilverGoldUser priority
32kbps64kbps128kbpsDownlink
gold
user Pay $100
for 3G
services
In CN HLR, we can set ARP (Allocation Retention Priority ), during service setup, CNsends ARP to RNC .Based on the mapping relation( configured in RNC), RNC canidentify the user is a gold, silver or copper one.
The user priority affect GBR of BE service in RAN, Iub transmission management and soon.
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Services of the same class: Priority based on Allocation/Retention Priority (ARP)values, that is, ARP1 ->ARP2 ->ARP3 ->... ->ARP14=>
Only for the interactive service of the same ARP value: prioritybased on TrafficHandling Priority (THP, defined in CN , sent to RNC during service setup), that is, THP1 -> THP2 -> THP3 -> ... -> THP14=>
Services of the same ARP, class and THP (only for interactive services): HighSpeed Packet Access (HSPA) or Dedicated Channel (DCH) service preferred
depending on the value of the Indicator of Carrier Type Prior ity parameter.
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Only for the interactive service of the same ARP value: prioritybased on TrafficHandling Priority (THP), that is, THP1 -> THP2 -> THP3 -> ... -> THP14 =>
Services of the same ARP, class and THP (only for interactive services): HSPAor DCH service preferred depending on the value of the Indicator of Carrier Type Prior ity parameter.
Integrate Prior ity Configured Reference and Indicator of Carrier TypePriority are set by SET USERPRIORITY .
By default
Integrate Prior ity Configured Reference is set to ARP
Indicator of Carrier Type Prior ity is set to NONE, that means HSDPA and DCHservices have the same priority.
ARP and THP are carried in the RAB ASSIGNMENT REQUEST message, and they arenot configurable on the RNC LMT.
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z When the user has one RAB, User integrate priority is the
same as the RAB integrate priority
z For multiple RAB users, the integrate priority of the user is
based on the service of the highest priority
When the user has one RAB, User integrate priority is the same as the service of theRAB integrate priority;
For multiple RAB users, the integrate priority of the user is based on the service of thehighest priority.
User integrate priority is used in user-specific load control. For example, the selection of R99 users during preemption, the selection of users during inter-frequency loadhandover for LDR, and the selection of users during switching BE services to CCH areperformed according to the user integrate priority.
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Value range: ARP, Traffic ClassContent: This parameter is used to set the criterion by which the priority is first sorted.
The default value of this parameter is ARP
Set this parameter through SET USERPRIORITY
Indicator of Carrier Type Priority
Parameter ID: CARRIERTYPEPRIORIND
Value range: NONE, DCH, HSPA
Content: This parameter is used to decide which carrier (DCH or HSPA) takes
precedence when ARP and Traffic Class are identical. When this parameter is set toNONE, the bearing priority of services on the DCH is the same as that of HSPA
services.
The default value of this parameter is NONE,
Set this parameter through SET USERPRIORITY
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The parameters related to cell selection and cell reselection are Qoffset1(s,n) (load leveloffset), Qoffset2(s,n) (load level offset), and Sintersearch (start threshold for inter-frequency cell reselection).
The NodeB periodically reports the total TCP of the cell, and the PUC periodically triggersthe following activities:
Assessing the cell load level based on the total TCP
Configuring Sintersearch, Qoffset1(s,n), and Qoffset2(s,n) based on the cell load level
PUC can Modify inter-frequency cell reselection parameters based on the load:
1. Sintersearch :
when the load of a cell is “Heavy”, PUC will increase Sintersearch
when the load of a cell is “Light”, PUC will decrease Sintersearch
2. QOffset:when the load of current cell is “Heavy”and neighbor is “Non heavy”, PUC will decrease
QOffset
when the load of current cell is “Non heavy”and neighbor is “Heavy”, PUC will increaseQOffset
Updating the parameters of system information SIB3 and SIB11
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→: indicates that the parameter value remains unchanged.↗: indicates that the parameter value increases.↘: indicates that the parameter value decreases.
Value range: –10 to 10 ,step:2dBContent: This parameter defines the offset of Sintersearch when the center cell load
level is "Light". It is strongly recommended that this parameterbe set to a value not
higher than 0. The default value of this parameter is –2 (-4dB)
Set this parameter through ADD CELLPUC / MOD CELLPUC
Sintersearch offset 2
Parameter ID: OFFSINTERHEAVY
Value range: –10 to 10 ,step:2dB
Content: This parameter defines the offset of Sintersearch when the center cell loadlevel is "Heavy". It is strongly recommended that this parameterbe set to a value not
lower than 0. The default value of this parameter is 2 (4dB)
Set this parameter through ADD CELLPUC / MOD CELLPUC
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The NodeB periodically reports the total TCP of the cell, and the LDB periodically triggersthe following activities:
Assessing the cell load level based on the total TCP
If the downlink load of a cell is higher than the value of the Cell overload threshold, it isan indication that the cell is heavily loaded. In this case, the transmit power of the P-CPICH needs to be reduced by a step, which is defined by the Pilot power adjustmentstep parameter. However, if the current transmit power is equal to the value of the Mintransmit power of PCPICH parameter, no adjustment is performed.
If the downlink load of a cell is lower than the value of the Cell underload threshold, it isan indication that the cell has sufficient remaining capacity for more load. In this case, thetransmit power of the P-CPICH increases by a step, which is defined by the Pilot power adjustment step parameter, to help to lighten the load of neighboring cells. However, if the current transmit power is equal to the value of the Max transmit power of PCPICHparameter, no adjustment is performed.
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The default value of this parameter is 346 (34.6dBm)
Key parameters LDB
Pilot power adjustment step
Parameter ID: PCPICHPowerPace
Value range: 0 to 10 , Step 0.1dBContent: This parameter defines the step for the adjustment to the pilot power.
The default value of this parameter is 2, 0.2dB
Set this parameter through ADD CELLLDB / MOD CELLLDB
Max transmit power of PCPICH
Parameter ID: MaxPCPICHPower
Value range: –100 to 500 ,Step 0.1dB
Content: This parameter defines the maximum transmit power of the P-CPICH in a cell.
This parameter has to be set according to the actual system environment, that is, for
example, cell coverage (radius) and geographical environment. If the maximum transmitpower of the P-CPICH is set too low, the cell coverage decreases. When a certainproportion of soft handover area is ensured, any more increase in the pilot powerachieves no improvement on the performance of the downlink coverage.
The default value of this parameter is 346 (34.6dBm)
Set this parameter through ADD PCPICH / MOD PCPICHPWR
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The default value of this parameter is 313 (31.3dBm)
Key parameters LDB
Min transmit power of PCPICH
Parameter ID: MinPCPICHPower
Value range: -100 to 500Content: This parameter defines the minimum transmit power of the P-CPICH in a cell.
This parameter has to be set according to the actual system environment, that is, forexample, (radius) and geographical environment. If the minimum transmit power of theP-CPICH is set too low, the cell coverage will be affected. The parameter has to be setunder the condition that a certain proportion of soft handover area is ensured or theoccurrence of coverage hole can be prevented.
The default value of this parameter is 313 (31.3dBm)
Set this parameter through ADD PCPICH / MOD PCPICHPWR
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Note: RRC connection setup and Handover have higher priority
When a new service attempts to access the network, code resource admission ismandatory.
1. For RRC connection setup requests, the code resource admission is successful if thecurrent remaining code resource is enough for the RRC connection.
2. For handover services, the code resource admission is successful if the currentremaining code resource is enough for the service.
3. For other R99 services, the RNC has to ensure that the remaining code does notexceed the configurable threshold after admission of the new service.
4. For HSDPA services, the reserved codes are shared by all HSDPA services. Therefore,the code resource admission is not needed.
So the RRC connection setup and Handover has higher priority to access a cell
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Note: RRC connection setup and Handover have higher priority
The UL CAC and DL CAC are independent .
The basic principle of Power CAC is: RNC predict the cell power load after the access. If the load will be higher than a threshold, the admission is failed.
So, by setting different threshold for different access, we can realize different priorities.
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z Algorithm 1: based on UL/DL load measurement and load
prediction (RTWP and TCP)z Algorithm 2: based on Equivalent Number of User (ENU)
z Algorithm 3: loose call admission control algorithm
Huawei provide 3 Power CAC Algorithms
Algorithm 1: power resource admission decision based on power or interference.
Depending on the current cell load (uplink load factor and downlink transmitted carrier power)and the access request, the RNC determines whether the cell load will exceed the thresholdupon admitting a new call. If yes, the RNC rejects the request. If not, the RNC accepts therequest.
Algorithm 2: power resource admission decision based on the number of equivalentusers.Based on Huawei testing and experience, The 12.2 kbit/s AMR traffic is used tocalculate the Equivalent Number of Users (ENU) of all other services in UL and DL. The12.2 kbit/s AMR traffic's ENU is assumed to be 1. Depending on the current number of equivalent users and the access request in UL and DL, the RNC determines whether thenumber of equivalent users will exceed the threshold upon admitting a new call. If yes, theRNC rejects the request. If not, the RNC accepts the request.
Algorithm 3: power resource admission decision based on power or interference, but withthe estimated load increment always set to 0.Depending on the current cell load (uplink loadfactor and downlink TCP) and the access request, the RNC determines whether the cellload will exceed the threshold, with the estimated load increment set to 0. If yes, the RNCrejects the request. If not, the RNC accepts the request.
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Get current RTWP, and calculate thecurrent load factor
Admission request
Get the traffic characteristic, andestimate the increment of load factor
Calculate the predicted load factor
admitted rejected
End of UL CAC
Y NSmaller than
the threshold?
RTWPP N
UL −= 1η
η Δ
CCH UL predicted UL η η η η +Δ+= _
Pn is uplink receive background noise.
The procedure for uplink power resource decision is as follows:
1. The RNC obtains the uplink RTWP of the cell, and calculate the current uplink loadfactor.
2. The RNC calculates the uplink load incrementΔηUL based on the service request.
3. The RNC uses the formulaηUL,predicted=ηUL +ΔηUL to forecast the uplink loadfactor.
4. By comparing the forecasted uplink load factorηUL,predicted with the correspondingthreshold ,the RNC decides whether to accept the access request or not.
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The procedure for downlink power resource decision is as follows:
1. The RNC obtains the cell downlink TCP, and calculates the downlink load factor bymultiplying the maximum downlink transmit power by this TCP.
2. The RNC calculates the downlink load incrementΔP based on the service request andthe current load.
3. The RNC forecasts the downlink load factor.
4. By comparing the downlink load factor with the corresponding threshold (DL thresholdof ConvAMR service, DL threshold of Convnon_AMR service, DL threshold of otherservices, DL Handover access threshold), the RNC decides whether to accept theaccess request or not.
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Get the traffic characteristic, andestimate the increment of ENU
Calculate the predicted ENU
admitted rejected
End of UL/DL CAC
Y NSmaller than
the threshold?
∑==
N
iitotal ENU N ENU 1)(
new ENU
newtotaltotalENU N ENU N ENU +=+ )()1(
max/)1( ENU N ENU ENULoad total+=
The procedure for ENU resource decision is as follows:
1. The RNC obtains the total ENU of all exist users ENUtotal.
2. The RNC get the ENU of the new incoming user ENUnew.3. The RNC forecast the ENU load.
4. By comparing the forecasted ENU load with the corresponding threshold (the samethreshold as power resource), the RNC decides whether to accept the access requestor not.
The ENUmax can be set by LMT, the ENUnewand ENUi is determined by Huaweialgorithm, there is an example in next slide.
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z For the RRC connection request is, tolerance principles are
applied : Emergency call, Detach , Registration
Direct Admission
RRC connection request for other reasons
UL/ DL OLC Trigger threshold Admission
To ensure that the RRC connection request is not denied by mistake, tolerance principlesare applied.
The admission decision is made for the following reasons of the RRC connection request:
1. For the RRC connection request for the reasons of emergency call, detach orregistration, direct admission is used ,that is no limitation.
2. For the RRC connection request for other reasons, UL/DL OLC Trigger threshold is used for admission. By default, the OLC trigger threshold isrelatively high (DL/UL 95%), which make the RRC connections are easily setup.
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z UL Power CAC for HSUPA Scheduling Services and HSUPA Non-Scheduling Services
z RNC admits HSUPA scheduling service in either of the follow ing cases
Formula 1,2 or 3 is fulfilled
Formula 4 is fulfilled
z RNC admits HSUPA Non-scheduling service in either of the foll owing cases
Formula 1,2 or 3 is fulfilled
Formula 4 and 5 are fulfilled
ThdL is the Low priority HSUPA user PBR threshold of the current cell
ThdE is the Equal priority HSUPA user PBR threshold of the current cell
ThdGE is the High priority HSUPA user PBR threshold of the current cell
ηHS-DPCCH is the value of the UL HS-DPCCH reserve factor parameter, which defines the factor of UL HS-DPCCH resource reserved
ηthd is the cell UL admission threshold for specific type of service, that is UL threshold of ConvAMR service, UL threshold of Convnon_AMR service, UL threshold of other services or ULhandover access service threshold
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Uncontollable interference must be kept within a givenrange. The purpose is to ensure the stabilit y of system and
to prevent non-scheduling services and DCH services
from seizing the resources of HSUPA services
RNC admits R99 services if formula 1 and 2 are fulf illed
thd DPCCH HS cchULULctrlnonUL η η η <++Δ+−− ,,
totalthd DPCCH HS cchULULUL −−<++Δ+ η η η η .,
ηthd-total is the UL total power threshold of the current cell
ηthd is the cell UL admission threshold for specific type of service, that is UL threshold of ConvAMR service, UL threshold of Convnon_AMR service, UL threshold of other services or ULhandover access service threshold
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z For R99 and HSDPA RAB, The RNC uses the following formula
to predict the uplink load factor :
(ENUtotal + ENUnew) / ENUmax
z By comparing the forecasted ENU load with the corresponding
threshold ,the RNC decides whether to accept the access request
or not
ENUtotal is the total ENU of all existing users.
ENUnewis ENU of the new incoming user .
ENUmax is the configured maximum ENU (UL total equivalent user number or DL totalnonhsdpa equivalent user number) .
The threshold for Algori thm2 are the same with Algori thm1,for Conv AMR service ,Conv non_AMR service , Other R99 services , Handover , HSDPA are set independently:
DL total power thresholdHSDPA
DL threshold of Conv AMR serviceDL threshold of Conv non_AMR serviceDL threshold of other servicesDL Handover access threshold
DL DCH
UL threshold of Conv AMR serviceUL threshold of Conv non_AMR serviceUL threshold of other servicesUL Handover access threshold
UL DCH/HSUPA
Admission ThresholdService Type
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Value range: 0 to 100 %Content: The uplink threshold for the AMR conversational service is used for the uplinkadmission of AMR conversational service users. The threshold is shared by algorithm 1,algorithm 2 and algorithm 3.
The default value of this parameter is 75%
Set this parameter through ADD CELLCAC / MOD CELLCAC
UL threshold of Conv non_AMR service
Parameter ID: UlNonCtrlThdForNonAMR
Value range: 0 to 100 %Content: The downlink threshold for the AMR conversational service is used for thedownlink admission of AMR conversational service users. The threshold is shared byalgorithm 1, algorithm 2 and algorithm 3.
The default value of this parameter is 75%
Set this parameter through ADD CELLCAC / MOD CELLCAC
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Value range: 0 to 100 %Content: This parameter is the uplink threshold for services other than theconversational service. It is used for uplink admission of other services. The threshold isshared by algorithm 1, algorithm 2 and algorithm 3.
The default value of this parameter is 60%
Set this parameter through ADD CELLCAC / MOD CELLCAC
UL Handover access threshold
Parameter ID: UlNonCtrlThdForHo
Value range: 0 to 100 %
Content: The uplink handover threshold is used for uplink admission of handover users. The parameter is useful only to uplink inter-frequency handovers. Do not make theadmission decision in the uplink soft handover. The threshold is shared by algorithm 1,algorithm 2 and algorithm 3.
The default value of this parameter is 80%
Set this parameter through ADD CELLCAC / MOD CELLCAC
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Value range: 0 to 100 %Content: The downlink threshold for the AMR conversational service is used for thedownlink admission of AMR conversational service users. The threshold is shared byalgorithm 1, algorithm 2 and algorithm 3.
The default value of this parameter is 80%
Set this parameter through ADD CELLCAC / MOD CELLCAC
DL threshold of Conv non_AMR service
Parameter ID: DLCONVNAMRTHD
Value range: 0 to 100 %
Content: The downlink threshold for the non-AMR conversational service is used for thedownlink admission of non-AMR conversational service users. The threshold is sharedby algorithm 1, algorithm 2 and algorithm 3.
The default value of this parameter is 80%
Set this parameter through ADD CELLCAC / MOD CELLCAC
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Value range: 0 to 100 %Content: This parameter is the downlink threshold for services other than theconversational service. It is used for downlink admission of users of other services. Thethreshold is shared by algorithm 1, algorithm 2 and algorithm 3.
The default value of this parameter is 75%
Set this parameter through ADD CELLCAC/MOD CELLCAC
DL Handover access threshold
Parameter ID: DLHOTHD
Value range: 0 to 100 %
Content: The downlink handover threshold is used for downlink admission of handoverusers. The threshold is shared by algorithm 1, algorithm 2 and algorithm 3.
The default value of this parameter is 85%
Set this parameter through ADD CELLCAC / MOD CELLCAC
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Value range: 1 to 200Content: When algorithm 2 is used, this parameter defines the total equivalent numberof users corresponding to the 100% uplink load.
The default value of this parameter is 80
Set this parameter through ADD CELLCAC/MOD CELLCAC
DL total equivalent user number
Parameter ID: DLTOTALEQUSERNUM
Value range: 1 to 200
Content: When algorithm 2 is used, this parameter defines the total equivalent numberof users corresponding to the 100% downlink load.
The default value of this parameter is 80
Set this parameter through ADD CELLCAC / MOD CELLCAC
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z When a new service accesses the network, NodeB credit
resource admission is optional
z The principles of NodeB credit admission control are similar
to those of power resource admission control, that is, to
check in the local cell whether the remaining credit can
support the requesting services
CE stands for NodeB credit on RNC side and for Channel Element on NodeB side. It isused to measure the channel demodulation capability of the NodeBs
The resource of one 12.2kbps voice service, including 3.4kbps signaling on the DCCH,consumed in baseband is defined as one CE. If there is 3.4kbps signaling on the DCCH,but no voice channel, one CE is consumed.The credit resource are divided into severalresource pools. Each resource pool is shared by a local cell.
According to the common and dedicated channels capacity consumption laws, as well asthe addition, removal, and reconfiguration of the common and dedicated channels, theControlling RNC (CRNC) debits the amount of the credit resource consumed from orcredits the amount to the Capacity Credit of the local cell group (and local cell , if any)based on the spreading factor.
the UL Capacity Credit and DL Capacity Credit are separate, so the CAC is performed inthe UL and DL, respectively.
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z When a new service tries to access the network, the credit
resource admission CAC functions in :
RRC connection setup
Handover service
The other services
For an RRC connection setup request, the credit resource admission is successful if the currentremaining credit resource is sufficient for the RRC connection.
For a handover service, the credit resource admission is successful if the current remaining creditresource is sufficient for the service.
For other services, the RNC has to ensure that the remaining credit does not exceed theconfigurable thresholds after admission of the new services.
There is no capacity consumption law for HS-DSCH in 3GPP TS 25.433, so certain credits arereserved for HSDPA RAB, and credit admission for HSDPA is not needed.
UL Capacity Credit and DL Capacity Credit are separate, the credit resource admission isimplemented in the UL and DL, respectively.
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Value range: SF4, SF8, SF16, SF32, SF64, SF128, SF256, SFOFFContent: The spreading factor specified by this parameter is used to define the uplinkcredit resource reserved for handover services.
SFOFF means that none of resources are reserved for handover services. If theremaining uplink resource cannot fulfill the requirement for the reserved resource afterthe admission of a new service, the service is rejected.
The default value of this parameter is SF16
Set this parameter through ADD CELLCAC / MOD CELLCAC
Dl HandOver Credit and Code Reserved SF
Parameter ID: DlHoCeCodeResvSf
Value range: SF4, SF8, SF16, SF32, SF64, SF128, SF256, SFOFF
Content: The spreading factor specified by this parameter is used to define the downlinkcredit and channelized code resources reserved for handover services.
SFOFF means that none of the resources is reserved for handover. If the remainingdownlink resource cannot fulfill the requirement for the reserved resource after theaccess of a new service, the service is rejected.
The default value of this parameter is SF32
Set this parameter through ADD CELLCAC / MOD CELLCAC
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The UMTS supports four traffic classes: conversational, streaming, interactive, andbackground.
The transmission rate varies with the traffic class as follows:
For Circuit Switched (CS) conversational services, the channel transmits voice signals ata certain rate (for example, 12.2 kbit/s) during a conversation and only transmits SilenceDescriptors (SIDs) at intervals when there is no conversation.
For Packet Switched (PS) interactive and background services, such as web browsing,there is data transmitted during data downloading. After a web page has beendownloaded, and when the user is reading the page, however, there is very little data to
transfer.
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Maximum number of HSPA users in all the cells configured in
one NodeB
When the HSDPA_UU_ADCTRL is on, the HSDPA services have to undergo HSDPAuser number admission decision.
When a new HSDPA service attempts to access the network, it is admitted if the numberof HSDPA users in the cell and that in the NodeB do not exceed the associatedthresholds
When the HSUPA_UU_ADCTRL is on, the HSUPA services have to undergo HSUPAuser number admission decision.
When a new HSUPA service attempts to access the network, it is admitted if the numberof HSUPA users in the cell and that in the NodeB do not exceed the associatedthresholds
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For PS NRT (Non-Real Time) services, CAC is not flexible
No consideration about the priority of different users
No consideration about Directed Retry after CAC rejection
z “Intelligent”means the algorithm can increase admission
successful rate
CAC limits the setup of RRC and RAB . When the cell is overloaded , the CAC will causeaccess failure.
In order to improve the access success rate the Intelligent Access Control (IAC) algorithm isused to improve the access success rate. The IAC procedure includes rate negotiation,Call Admission Control (CAC), preemption, queuing, and Directed Retry Decision (DRD).
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When a new service accesses the network, an RRC connection must be set up first. If theRRC connection request is denied, DRD is performed. If DRD also fails, RRCredirection is performed to direct the UE to an inter-frequency or inter-RAT cell
through cell reselection.
After the RNC receives the RRC CONNECTION REQUEST message, the CAC algorithmdecides whether an RRC connection can be set up between the UE and the currentcell.
If the RRC connection can be set up between the UE and the current cell, the RNC sendsan RRC CONNECTION SETUP message to the UE. If the RRC connection cannotbe set up between the UE and the current cell, the RNC takes the follow ingactions:
RRC DRD :
If the DRD_SWITCH is set to 0, the RRC DRD fails, and RRC redirection is performed.
Else, the RNC performs the following steps:1. The RNC selects inter-frequency neighboring cells of the current cell. These
neighboring cells are suitable for blind handovers.
2. The RNC generates a list of candidate DRD-supportive inter-frequency cells. Thequality of the candidate cell meets the requirements of inter-frequency DRD:
(CPICH_Ec/No)RACH > DRD_Ec/No nbcell
where
(CPICH_Ec/No)RACH is the cached CPICH Ec/N0 value included in the RACHmeasurement report.
DRD_Ec/No nbcell is the DRD Ec/N0 Threshold set for the inter-frequencyneighboring cell.
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3. RNC selects a target cell from the candidate cells for UE access. If the candidate cell list containsmore than one cell, the UE tries a cell randomly.
1. If the admission is successful, the RNC initiates an RRC DRD procedure.
2. If the admission to a cell fails, the UE tries admission to another cell in the candidate cell
list. If all the admission attempts fail, the RNC makes an RRC redirection decision.4. If the candidate cell list does not contain any cell, the RRC DRD fails. The RNC performs the next
step, that is, RRC redirection.
5. RRC redirection, the RNC performs the following steps:
1. The RNC selects all inter-frequency cells of the local cell.
2. The RNC selects candidate cells. That is, exclude the cells to which inter-frequency RRCDRD attempts have been made from the cells selected in the previous step.
3. If more than one candidate cell is available, the RNC selects a cell randomly and redirectsthe UE to the cell.
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Rate negotiation includes the maximum expected rate negotiation, initial rate negotiation, and target rate negotiation.
When setting up, modifying, or admitting a PS service (conversational, streaming, interactive, or background service)the RNC and the CN negotiate the rate according to the UE capability to obtain the maximum expected rate whileensuring a proper QoS.
For a non-real-time service in the PS domain, the RNC selects an initial rate to allocate bandwidth for the servicewhen Setup or UE state transits from CELL_FACH to CELL_DCH based on cell code and credit resource
The Initial rate selection is affected by 2 algorithm switches: RAB Downsizing Switch, DCCC Switch
For DCH For HSUPA
For a non-real-time service in the PS domain, if cell resource admission fails, the RNC chooses a target rate toallocate bandwidth for the service based on cell resource in Service setup or Soft handover
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z RAB Directed Retry Decision (DRD) is used to select a
suitable cell for the UE to try an access
Inter-frequency DRD
Service Steering
Load Balancing
Inter-RAT DRD
Through the RAB DRD procedure, the RNC selects a suitable cell for RAB processingduring access control. RAB DRD is of two types: inter-frequency DRD and inter-RATDRD. For inter-frequency DRD, the service steering and load balancing algorithms are
available.
After receiving a RANAP RAB ASSIGNMENT REQUEST, the RNC initiates an RABDRD procedure to select a suitable cell for RAB processing during access control.
The RNC performs inter-frequency DRD firstly. If all admission attempts of inter-frequency DRD fail, the RNC performs an inter-RAT DRD. If all admission attempts of inter-RAT DRD fail, the RNC selects a suitable cell to perform preemption andqueuing .
Relation Between Service Steering DRD and Load Balancing DRD
When both service steering DRD and load balancing DRD are enabled, the generalprinciples of inter-frequency DRD are as follows:
• Service steering DRD takes precedence over load balancing DRD. That is,preferably take service priorities into consideration.
• To services of the same service priority, load balancing applies.
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DRD for Service Steering is based on Service priorities of cells ,include:
– R99 RT services pr iority
– R99 NRT services pr iorit y
– HSPA services priority
– Other services priority
Called Service priority group
If the UE requests a service in an area covered by multiple frequencies, the RNC selectsthe cell with the highest service priority for UE access, based on the service type of RAB and the definitions of service priorities in the cells.
Cell service priorities help achieve traffic absorption in a hierarchical way.
The priorities of specific service types in cells are configurable. If a cell does not support aservice type, the priority of this service type is set to 0 in this cell.
The service priorities in each cell is calledService priority group , which is identified bythe Service priority group Identity parameter.
Service priority groups are configured on the LMT. In each group, priorities of R99 RTservices, R99 NRT services, HSPA services, and other services are defined.
When selecting a target cell for RAB processing, the RNC check the service type firstly ,then, selects a cell with a high priority for the service, that is, a cell that has a smallvalue of service priority.
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Assume that the service priority groups given in the table are defined on an RNC, 2groups of service priorities are defined.
Then ,Cell A is configured with service priority group 1. Cell B is configured with servicepriority group 2
If UE requests a R99 RT service in cell A ,Cell B has a higher service priority of the R99RT service than cell A. If the UE requests an RT service in cell A, preferably, the RNCselects cell B for the UE to access.
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z Inter-Frequency DRD procedure for Service Steering
The procedure for the service steering DRD is as follows:
1、 The RNC determines candidate cells to which blind handovers can be performed and sorts thecandidate cells into a descending order according to service priority.
A candidate cell must meet the following conditions:
• The frequency of the candidate cell is within the band supported by the UE.
• The quality of the candidate cell meets the Ec/No requirements of inter-frequency DRD (DRDEc/N0 Threshold )
• The candidate cell supports the requested service.
2、 The RNC selects a target cell from the candidate cells in order of service priority for UE access.
3、 The CAC algorithm makes an admission decision based on the status of the target cell.
• If the admission attempt is successful, the RNC accepts the service request.
• If the admission attempt fails, the RNC removes the cell from the candidate cells and then
choose next candidate cell.4、If admission decisions have been made in all the candidate cells
• For HSPA access, the HSPA request falls back to a DCH one. Then, the algorithm goes backto Step 1 to make an admission decision based on R99 service priorities.
• For DCH access, the RNC initiates an inter-RAT DRD.
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Content: This parameter specifies the support of the cells with a specific Service prioritygroup Identity for R99 RT services.
The value 0 means that these cells do not support R99 RT services.
For the values 1 through 7, the service priority is inversely proportional to the value, that is,the value 7 indicates the lowest service priority, whereas the value 1 indicates the highest.
Set this parameter through ADD SPG
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IAC – Inter-frequency DRDz Inter-Frequency DRD procedure for DL Power Load Balance
The procedure for the service steering DRD is as follows:
1、 The RNC determines candidate cells to which blind handovers can be performed and sortsthe candidate cells into a descending order according to service priority.
A candidate cell must meet the following conditions:
• The frequency of the candidate cell is within the band supported by the UE.
• The quality of the candidate cell meets the Ec/No requirements of inter-frequency
DRD (DRD Ec/N0 Threshold )
• The candidate cell supports the requested service.
2、 The RNC determines whether the DL radio load of the current cell is lower than the power threshold for load balancing DRD (condition 1 )
power threshold for load balancing DRD is CAC parameter.
•If the DL load of the current cell is lower than the threshold, the service tries admission tothe current cell.
•If the DL load of the current cell is equal to or higher than the threshold, the RNC checksthe candidate cells to try to find out a target cell for UE access.
RNC will check if there is a candidate cell will meet the following condition (condition 2 ) :
•Ptotal_thd,nbcell is DL total power threshold for the inter-frequency neighboring cell.
•P load,nbcell is total power load of the inter-frequency neighboring cell. For a R99 cell, it isthe Downlink Transmitted Carrier Power of the cell, and for an HSPA cell, it is the non-HSDPA power and GBP.
•Ptotal_thd,cutcell is DL total power threshold for the current cell.
•P load,cutcell is the total downlink load of the current cell.
•P loadoffset is the Power balancing drd offset of the current cell.
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•If there is only one inter-frequency neighboring cell that meets the load balancing DRDconditions, the RNC selects this cell as the target cell.
•If there are multiple such cells, the RNC selects the cell with the lightest load as the
target cell.•If there is no such cell, the RNC selects the current cell as the target cell.
3、 The CAC algorithm makes an admission decision based on the status of the target cell.
•If the admission attempt is successful, the RNC accepts the service request.
•If the admission attempt fails, the RNC removes the cell from the candidate cells andthen choose next candidate cell.
4、If admission decisions have been made in all the candidate cells
•For HSPA access, the HSPA request falls back to a DCH one. Then, the algorithm goesback to Step 1to make an admission decision based on R99 service priorities.
•For DCH access, the RNC initiates an inter-RAT DRD.
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The default value of this parameter is 430 (43dBm)
z Dl power balancing drd power threshold for DCH
Parameter ID: LdbDRDOffsetDCH
The default value of this parameter is 10%
z Dl power balancing drd power threshold for HSDPA
Parameter ID: LdbDRDOffsetHSDPA
The default value of this parameter is 10%
Key parameters
Power balancing drd switch
Parameter ID: PowerBalancingDrdSwitch
Value range: ON, OFFContent: This parameter specifies whether to enable the power-based loadbalancing DRD algorithm .
The default value of this parameter is OFF.
Set this parameter through SET DRD / ADD CELLDRD
Max transmit power of cell
Parameter ID: MaxTxPower
Value range: 0 to 500 , step:0.1dBm
Content: This parameter specifies the sum of the maximum transmit power of all the downlink channels in a cell.
The default value of this parameter is 430 (43dBm).
Set this parameter through MOD CELL
Power balancing drd offset
Parameter ID: LoadBalanceDRDOffset
Value range: 0% to 100%
Content: This parameter specifies the load offset threshold of the current celland the inter-frequency cell when power balancing drd algorithm is applied.Only when the cell load offset reaches this threshold, the inter-frequency cellcan be selected to be the target drd cell.
The default value of this parameter is 10%
Set this parameter through SET DRD / ADD CELLDRD
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The procedure of load balancing DRD based on code resource is similar to that based on powerresource.
1、 The RNC determines whether the minimum remaining spreading factor of the current cell issmaller than Minimum SF threshold for code balancing drd.
• If the minimum SF is smaller thanMinimum SF threshold for code balancing drd, theRNC tries the admission of the service request to the current cell.
• If the minimum SF is not smaller thanMinimum SF threshold for code balancing drd,the RNC performs the next step .
2、 The RNC determines whether the code load of the current cell is lower thanCode occupiedrate threshold for code balancing drd. .
• If the code load is lower than Code occupied rate threshold for code balancing drd,the service tries the admission to the current cell.
• If the code load is not lower than Code occupied rate threshold for code balancing
drd, the RNC selects the cell with the lightest code load or the current cell as the targetcell.
3、 The RNC selects the cell as follows:
• If the difference between the code resource occupancies of the cell and the current cellis larger than the value of Delta code occupied rate , the RNC selects the cell with thelightest code load as the target cell. Otherwise, the RNC selects the current cell as thetarget cell.
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z Code occupied rate threshold for code balancing drd
Parameter ID: CodeBalancingDrdCodeRateThd
The default value of this parameter is 13%
z Delta code occupied rate
Parameter ID: DeltaCodeOccupiedRate
The default value of this parameter is 7%
Key parameters
Code occupied rate threshold for code balancing drd
Parameter ID: CodeBalancingDrdCodeRateThd
Value range: 0% to 100%Content: This parameter specifies the code occupancy threshold of the current cell forcode-based load balancing DRD.Only when the code occupancy of the best cellreaches this threshold can code-based load balancing DRD be triggered.
The default value of this parameter is 13%.
Set this parameter through SET DRD / ADD CELLDRD
Delta code occupied rate
Parameter ID: DeltaCodeOccupiedRate
Value range: 0% to 100%
Content: This parameter specifies the code occupied rate offset threshold of thecurrent cell and the inter-frequency cell when code balancing drdalgorithm is applied.Only when the code occupied rate offset reaches this threshold, the inter-frequencycell can be selected to be the target drd cell.
The default value of this parameter is 7% .
Set this parameter through SET DRD
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Inter-RAT DRD is available for AMR service only in RAN 10:
The inter-RAT DRD procedure is as follows:
1,If the current cell is configured with any neighboring GSM cell suitable for blind handoverand the Service Handover Indicator is set to HO_TO_GSM_SHOULD_BE_PERFORM,the RNC performs next step. Otherwise, the service request undergoes preemption andqueuing.
2,The RNC generates a list of candidate DRD-supportive inter-RAT cells that fulfill the Ec/Nothreshold.
3,The service request then tries admission to a target GSM cell in order of blind handover priority.
4,If all admission attempts fail or the number of inter-RAT directed retries exceeds the valueof Max inter-RAT direct retry number , the service request undergoes preemption andqueuing.
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Value range: 0 to 5Content: This parameter defines the maximum number of inter-RAT directedretries for an RAB. The value 0 means that inter-RAT DRD is not allowed.
The default value of this parameter is 2
Set this parameter through ADD CELLDRD
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IAC – Preemptionz Preemption on different resources
√√-Number of users
√√√Iub bandwidth
---CE
√√√Power
---CodeHSDPAservice
√√√Iub bandwidth
√-√CE
√√√Power
√-√CodeR99 service
R99 + HSPA Combined ServiceHSDPA ServiceR99 Service
Service That can Be PreemptedResourceService
The preemption procedure is as follows:
1、 The preemption algorithm determines which radio link sets can be preempted. Thealgorithm proceeds as follows:
Chooses SRNC users first. If no user under the SRNC is available, thealgorithm chooses users under the DRNC.
Sorts the pre-emptable users by user integrate priority, or sorts the pre-emptable RABs byRAB integrate priority.
Determines candidate users or RABs.
Only the users or RABs with priorities lower than the RAB to beestablished are selected.
Selects as many users or RABs as necessary in order to match the resourceneeded by the RAB to be established. When the priorities of two users orRABs are the same, the algorithm chooses the user or RAB that can release
the most resources.
2、 The RNC releases the resources occupied by the candidate users or RABs.
3、 The requested service directly uses the released resources to access the networkwithout admission decision.
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z After Preemption rejection, UE can wait in queue, then
admission attempts for the service are made periodically till Tmax expires.
z Admission attempts are made based on Queuing priority:
Pqueue = Tmax – Telapsed
Tmax is the maximum time in the queue, default value is 5s
Telapsed is the time has queued
After the cell resource decision fails, the RNC performs queuing if the RNC receives an RABASSIGNMENT REQUEST message indicating the queuing function is supported
The queuing algorithm checks whether the queue is full, that is, whether the number of service
requests in the queue exceeds the queue length that is defined by the Queue length The queuing algorithm is triggered by the heartbeat timer, which is set through the Poll timer
length .
If the queue is not full:
• Stamps this request with the current time.
• Puts this request into the queue.
If the queue is full:
• Checks whether there are requests whose integrate priorities are lower than that of the priority of the new request. If there is, delete the low priority request, put the newservice in the queue. (Otherwise, the queuing algorithm rejects the new requestdirectly.)
• Stamps the new request with the current time and then puts it into the queue.
After the heartbeat timer (Poll timer length) expires, the queuing algorithm proceeds as follows:
• Selects the request with the highest integrate priority for an attempt of resourceallocation .
• If the attempt fails, the queuing algorithm proceeds as follows:
• Puts the service request back into the queue with the time stampunchanged for the next attempt.
• Chooses the request with the greatest weight from the rest and makesanother attempt until a request is accepted or all requests are rejected.
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Value range: 1 to 6000 , step: 10msContent: This parameter defines the length of the heartbeat timer. Each time the timerexpires, the RNC chooses the service that meets the requirement to make anadmission attempt .
The default value of this parameter is 50 (500ms)
Set this parameter through SET QUEUEPREEMPT
Max queuing time length
Parameter ID: MAXQUEUETIMELEN
Value range: 1 to 60s
Content: This parameter defines the maximum time that the service request can be inthe queue.
The default value of this parameter is 5s
Set this parameter through SET QUEUEPREEMPT
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When the usage of cell resource exceeds the basic congestion triggering threshold, thecell enters the basic congestion state. In this case, LDR is required to reduce the cell load
and increase the access success rate.
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For power resource, the RNC performs periodic measurement and checks whether thecells are congested. For code, Iub, and NodeB credit resources, event-triggered congestionapplies, that is, the RNC checks whether the cells are congestedwhen resource usage
changes.
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Load Reshuffling Actions tr iggered by dif ferent resources
If the downlink power admission uses the equivalent user number algorithm, basic congestion can also betriggered by the equivalent number of users. In this situation, LDR actions do not involve AMR ratereduction or MBMS power reduction, as indicated by the symbol "*" in above table
Congestion of different resource may trigger different actions.
For example, Credit congestion do not trigger “Inter-Frequency Load Handover” , “ AMR RateReduction”, and “Code Reshuffling”
When congestion of all resources is triggered, the action to be taken is based on the resource priorityconfiguration.
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Value range: 0 to 100 , %Content: If the UL load of the cell is not lower than this threshold, the UL loadreshuffling function of the cell is triggered.
The default value of this parameter is 55%
Set this parameter through ADD CELLLDM/MOD CELLLDM
UL LDR release threshold
Parameter ID: ULLDRRELTHD
Value range: 0 to 100 , %
Content: If the UL load of the cell is lower than this threshold, the UL load reshufflingfunction of the cell is stopped.
The default value of this parameter is 45%
Set this parameter through ADD CELLLDM / MOD CELLLDM
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Value range: 0 to 100 , %Content: If the DL load of the cell is not lower than this threshold, the DL loadreshuffling function of the cell is triggered.
The default value of this parameter is 70%
Set this parameter through ADD CELLLDM / MOD CELLLDM
DL LDR release threshold
Parameter ID: DLLDRRELTHD
Value range: 0 to 100 , %
Content: If the DL load of the cell is lower than this threshold, the DL load reshufflingfunction of the cell is stopped.
The default value of this parameter is 60%
Set this parameter through ADD CELLLDM / MOD CELLLDM
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Value range: SF4, SF8, SF16, SF32, SF64, SF128, SF256Content: If the SF corresponding to the current remaining code of the cell is higher thanthe threshold defined by this parameter, code congestion is triggered and the relatedhandling actions are taken.
The default value of this parameter is SF8
Set this parameter through ADD CELLLDR / MOD CELLLDR
Ul LDR Credit SF reserved threshold
Parameter ID: ULLDRCREDITSFRESTHD
Value range: 0 to 100 , %
Content: If the SF corresponding to the current UL remaining credit resource is higherthan the threshold defined by this parameter, the UL credit LDR can be performed andthe related handling actions are taken.
The default value of this parameter is 60%
Set this parameter through ADD NODEBLDR/MOD NODEBLDR
Dl LDR Credit SF reserved threshold
Parameter ID: DLLDRCREDITSFRESTHD
Value range: 0 to 100 , %
Content: If the value of SF corresponding to the current DL remaining credit resource ishigher than the threshold defined by this parameter, the DL credit LDR can be
performed and the related handling actions are taken. The default value of this parameter is SF8
Set this parameter through ADD NODEBLDR/MOD NODEBLDR
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Current bandwidth for DCH or “GBR bandwidth for HSPA”has to be less
than the UL/DL Inter-freq cell load handover maximum bandwidth
parameter
Target cells
Load difference between current load and the basic congestion trigger
threshold of target cell is larger than “UL/DL Inter-freq cell load handover
load space threshold”
It is implemented as follows:
1. The LDR check whether the existing cell has a target cell of inter-frequency blind handover. If there is nosuch a target cell, the action fails, and the LDR performs the next action.
2. The principles of selecting inter-freq handover target cell are different as a result of the different resourceswhich trigger the basic congestion.
1. If the basic congestion is triggered by the power resource:
The LDR checks whether the load difference between the current load and the basic congestion triggeringthreshold of each target cell for blink handover is larger than the UL/DL Inter-freq cell load handover loadspace threshold (both the uplink and downlink conditions must be fulfilled). The other resources (coderesource, Iub bandwidth, and NodeB credit resource) in the target cell do not trigger basic congestion.
If the difference is not larger than the threshold, the action fails, and the LDR takes the next action.
If there are more than one cell meeting the requirements, the first one is selected as the blind handovertarget cell.
2. If the basic congestion is triggered by the code resource:
Weather there are blind handover target cells meeting the requirements is decided by the followingconditions:
The minimum SF of the target cell is not greater than that of current cell.
The difference of code occupy rate between current cell and the target cell is greater than InterFreq HOcode used ratio space threshold.
The state of target cell is normal.
If there is no such cell, this action fails and the LDR performs the next action. If there are more than one cellmeeting the requirements, the first cell is selected as the blind handover target cell.
3. If the LDR finds out a target cell that meets the specified blind handover conditions, the LDR selects one UEto make an inter-frequency blind handover, depending on the UE’s ARP and occupied bandwidth. For theselected UE other than a gold user, its UL/DL current bandwidth for DCH, GBR bandwidth for HSPA, shall be
less than and have the least difference from the UL/DL Inter-freq cell load handover maximum bandwidthparameter (Both the uplink and downlink condition must be fulfilled). If the LDR cannot find such a UE, theaction fails. The LDR performs the next action.
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z UL/DL Inter-freq cell load handover load space threshold
Parameter ID: UL/DLINTERFREQHOCELLLOADSPACETHD
The default value of this parameter is 20
z InterFreq HO code used ratio space threshold
Parameter ID: LdrCodeUsedSpaceThd
The default value of this parameter is 13
z UL/DL Inter-freq cell load handover maximum bandwidth
Parameter ID: UL/DLINTERFREQHOBWTHD
The default value of this parameter is 200000
Key parameters
UL/DL Inter-freq cell load handover load space threshold
Parameter ID: UL/DLINTERFREQHOCELLLOADSPACETHD
Value range: 0 to 11 %
Content: The target cell can be a cell for inter-frequency blind handover only when theUL/DL load space is higher than the threshold.
The UL/DL load space is the difference between the UL/DL basic congestion triggeringthreshold and the current UL/DL load of a target cell for blind handover. .
The default value of this parameter is 20%
Set this parameter through ADD CELLLDR / MOD CELLLDR
InterFreq HO code used ratio space threshold
Parameter ID: LdrCodeUsedSpaceThd
Value range: 0% to 100% (0~1) ,step:1%
Content: The target cell can be used for inter-frequency blind handover only when theDL Code used ratio space is higher than the threshold. The DL Code used ratio spaceis the difference of code used ratio between the source cell and the target cell.
The default value of this parameter is 13%
Set this parameter through ADD CELLLDR / LST CELLLDR / MOD CELLLDR
UL/DL Inter-freq cell load handover maximum bandwidth
Parameter ID: UL/DLINTERFREQHOBWTHD
Value range: 0 to 400000 bps
Content: During the inter-frequency load handover, the UE is selected as the target of
inter-frequency load handover from the UE set where the bandwidth is less than thisthreshold.
The default value of this parameter is 200000
Set this parameter through ADD CELLLDR / MOD CELLLDR
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BE rate reduction is implemented by reconfiguring the bandwidth. Bandwidthreconfiguration requires signaling interaction on the Uu interface.
The LDR algorithm is implemented as follows:
1. Based on the integrate priority, the LDR sorts the RABs into a descending order. Thetop RABs related to the BE services (whose current rate is higher than its GBRconfigured by SET USERGBR command) are selected. If the integrate priorities of some RABs are identical, the RAB with the highest rate is selected. The number of RABs to select is determined by the UL/DL LDR-BE rate reduction RAB number parameter.
2. The bandwidth of the selected services is reduced to the specified rate.
3. If services can be selected, the action is successful. If services cannot be selected, theaction fails. The LDR takes the next action.
4. The reconfiguration is completed as indicated by the RB RECONFIGURATION
message on the Uu interface and through the RL RECONFIGURATION message onthe Iub interface.
5. The BE rate reduction algorithm is controlled by the DCCC algorithm switch. BE rate
reduction can be performed only when the DCCC algorithm is enabled.
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Value range: 1 to 10Content: These parameters specify the number of RABs to select in a UL/DL LDR BErate reduction.
If the number of RABs that fulfil the criteria for BE rate reduction is smaller than thevalue of this parameter, then all the RABs that fulfil the criteria are selected.
The default value of this parameter is 1
Set this parameter through ADD CELLLDR / MOD CELLLDR
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z Uncontrolled Real-time service QoS Renegotiation
Target RABs
Based on RAB integrate priority
Real-time services in the PS domain
The load is reduced by adjusting the rate of the real-time services through uncontrolled real-time OoS renegotiation.
Upon receipt of the message, the CN sends the RAB ASSIGNMENT REQUEST messageto the RNC for RAB parameter reconfiguration. Based on this function, the RNC canadjust the rate of real-time services to reduce the load.
The LDR algorithm is implemented as follows:
1. Based on the integrate priority, the LDR sorts the real-time services in the PS domain indescending order. The top services are selected for QoS renegotiation.
2. The LDR performs QoS renegotiation for the selected services. The GBR duringservice setup is the rate of the service after QoS renegotiation.
3. The RNC initiates the RAB Modification Request message to the CN for QoSrenegotiation.
4. If the RNC cannot find a proper service for QoS renegotiation, the action fails. The LDR
performs the next action.
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Value range: 1 to 10Content: These parameters specify the number of RABs to select in a UL/DL LDRuncontrolled real-time QoS renegotiation.
If the number of RABs that fulfil the criteria for uncontrolled real-time QoS renegotiationis smaller than the value of this parameter, then all the RABs that fulfil the criteria areselected.
The default value of this parameter is 1
Set this parameter through ADD CELLLDR / MOD CELLLDR
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The 2G and 3G systems have different cell sizes and coverage modes. Therefore, blindhandover across systems is not taken into account.
The LDR is implemented in the downlink (e.g.) as follows:
1. Based on the integrate priority, the LDR sorts the UEs in descending order. The topCS/PS services are selected.
2. For the selected UEs, the LDR sends the load handover command to the inter-systemhandover module to ask the UEs to hand over to the 2G system.
3. The handover module decides to trigger inter-system handover, depending on thecapability of the UE and the capability of the algorithm switch to support thecompression mode.
4. This action is successful if any load handover UE is found. Otherwise, this action fails.
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Value range: 1 to 10Content: These parameters specify the number of users to select in a UL/DL Inter-RATShould Be Load Handover in the PS Domain.
If the number of users that fulfil the criteria for Inter-RAT Should Be Load Handover inthe PS Domain is smaller than the value of this parameter, then all the users that fulfilthe criteria are selected.
The default value of this parameter is 3
Set this parameter through ADD CELLLDR / MOD CELLLDR
UL / DL PS should not be ho user number
Parameter ID: UL/DLPSINTERRATSHOULDNOTBEHOUENUM
Value range: 1 to 10
Content: These parameters specify the number of users to select in a UL/DL Inter-RATShould Not Be Load Handover in the PS Domain.
If the number of users that fulfil the criteria for Inter-RAT Should Not Be Load Handoverin the PS Domain is smaller than the value of this parameter, then all the users that fulfilthe criteria are selected.
The default value of this parameter is 3
Set this parameter through ADD CELLLDR / MOD CELLLDR
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AMR services and with the bit rate higher than the GBR
Based on RAB integrate priority
In the WCDMA system, voice services work in eight AMR modes. Each mode has its ownrate. Therefore, mode control is functionally equal to rate control.
The LDR algorithm is implemented as follows:
1. Based on the integrate priority, the LDR sorts the RABs in the descending order. The topUEs accessing the AMR services (conversational) and with the bit rate higher than theGBR are selected.
2. In uplink, the RNC sends the “Rate Control request”message through the Iu-UP to theCN to adjust the AMR rate to the GBR.
3. In downlink, The RNC sends the TFC CONTROL command to the UE to adjust the AMRrate to the assured rate.
4. If the RNC cannot find a proper service for AMR rate reduction, the action fails. The LDRperforms the next action.
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Value range: 1 to 10Content: These parameters specify the number of RABs to select in a UL/DL LDR AMRrate reduction.
If the number of RABs that fulfil the criteria for AMR rate reduction is smaller than thevalue of this parameter, then all the RABs that fulfil the criteria are selected.
The default value of this parameter is 3
Set this parameter through ADD CELLLDR / MOD CELLLDR
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1,Initialize the SF_Cur of the root node of subtrees to Cell LDR SF reserved threshold.
2,Traverse all the subtrees with this SF_Cur at the root node. Leaving the subtreesoccupied by common channels and HSDPA channels out of account, take thesubtrees in which the number of users is not larger than the value of the Max user number of code adjust parameter as candidates for code reshuffling.
3,Select a subtree from the candidates according to the setting of the LDR code priorityindicator parameter.
z If this parameter is set to TRUE, select the subtree with the largest codenumber from the candidates.
z If this parameter is set to FALSE, select the subtree with the smallestnumber of users from the candidates. In the case that multiple subtrees havethe same number of users, select the subtree with the largest code number.
4,Treat each user in the subtree as a new user and allocate code resources to each user.
5,Initiate the reconfiguration procedure for each user in the subtree and reconfigure thechannel codes of the users to the newly allocated code resources.
The reconfiguration procedure on the air interface is implemented through the PHYSICALCHANNEL RECONFIGURATION message and that on the Iub interface through theRL RECONFIGURATION message.
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Content: This parameter specifies the switch of UL/DL OLC.
UL_UU_OLC: UL overload control algorithm
DL_UU_OLC: DL overload control algorithm
Set this parameter through ADD CELLALGOSWITCH / MOD CELLALGOSWITCH
UL/DL OLC trigger threshold
Parameter ID: UL/DLOLCTRIGTHD
Value range: 0 to 100 %
Content: If the UL load of the cell is not lower than the value of the UL OLC trigger
threshold, the UL overload congestion control of the cell is activated.If the DL load of the cell is not lower than the value of the DL OLC trigger threshold,the DL overload congestion control of the cell is activated.
Set this parameter through ADD CELLLDR / MOD CELLLDR
UL/DL OLC release threshold
Parameter ID: UL/DLOLCRELTHD
Value range: 0 to 100 %
Content: If the UL load of the cell is lower than the value of the UL OLC releasethreshold, the UL overload congestion control of the cell is deactivated.
If the DL load of the cell is lower than the value of the DL OLC release threshold, theDL overload congestion control of the cell is deactivated.
Set this parameter through ADD CELLLDR / MOD CELLLDR
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The general OLC procedure covers the following actions: TF control of BE services, channelswitching of BE services, and release of RABs. The RNC takes periodical actions if overloadcongestion is detected.
When the cell is overloaded, the RNC takes one of the following actions in each period (defined bythe OLC period timer length parameter, e.g.3s) until the congestion is resolved:
1. TF control of BE service (only for DCH BE service)
2. Switching BE services to common channel
3. Choosing and releasing the RABs (for HSPA or DCH service)
If the first action fails or the first action is completed but the cell is still in congestion, then thesecond action is taken.
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The RNC sends the “TF control indication”message to the MAC.
MAC restricts the TFC selection :
TFmax(N+1) =TFmax(N) x Ratelimitcoeff
Based on the RAB integrate priority, the OLC sorts the RABs into a descending order.Thefollowing RABs are selected:
1. The RABs with the DCH BE services
2. The RABs with the lowest integrate priority.
3. The number of RABs selected is DL/UL OLC fast TF restrict RAB number .
The RNC sends the TF control indication message to the MAC. Each MAC of selectedRABs will receive one TF control indication message and will restrict the TFC selectionof the BE services to reduce the data rate step by step.
MAC restricts the TFC selection in a way like that the maximum TB number is calculatedwith the formula:
TFmax(N+1) = TFmax(N) x Ratelimitcoeff
Ratelimitcoeff is a configurable parameter (DL OLC fast TF restric t data rate restrictcoefficient).
If the RNC cannot find an appropriate service for the TF control or the time for performingthe TF control exceed the DL OLC fast TF restrict times parameter, the action fails. The OLC performs the next action.
If the congestion is released, the RNC sends the congestion release indication to the MAC.At the same time, the rate recovery timer (whose length is defined by DL OLC fast TFrestrict data rate recover timer length) is started. When this timer is expired, theMAC increases the data rate step by step.
MAC recovers the TFC selection by calculating the maximum TB number with the formula:
TFmax(N+1) = TFmax(N) x RateRecoverCoeff
RateRecoverCoeff is a configurable parameter (DL TF rate recover coefficient)
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Value range: 0 to 10Content: These parameters specify the maximum number of RABs selected in a fast TF restriction of UL/DL OLC.
If the number of RABs that fulfil the criteria for TF control is smaller than the value of this parameter, then all the RABs that fulfil the criteria are selected.
The default value of this parameter is 3
Set this parameter through ADD CELLOLC / MOD CELLOLC
UL/DL OLC fast TF restrict times
Parameter ID: UL/DLOLCFTFRSTRCTTIMES
Value range: 0 to 100
Content: These parameters specify the times of UL/DL OLC fast TF restrictions thatare executed.
The default value of this parameter is 3
Set this parameter through ADD CELLOLC / MOD CELLOLC
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Value range: 1 to 65535 msContent: This parameter specifies the length of the data rate recovery timer. Thesmaller the value of this parameter is, the faster the BE traffic rate increases after thecongestion is resolved.
The default value of this parameter is 5000 ms
Set this parameter through ADD CELLOLC / MOD CELLOLC
DL TF rate recover coefficient
Parameter ID: RecoverCoef
Value range: 100 to 200 %
Content: This parameter specifies the data rate recovery coefficient in the fast TFrestriction. The larger the parameter is, the larger the TF recover effect. After receivingcongestion release indication, the MAC obtains the maximum TF format with theformula TFmax' =TFmax x RateRecovercoeff.
The default value of this parameter is 130%
Set this parameter through ADD CELLOLC / MOD CELLOLC
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The RNC sends “RRC Connection Release”message to UE
OLC Algorithm for the Release of Some RABs in the Uplink:
The OLC algorithm for the release of some RABs in the uplink operates as follows:
Based on the integrate priority, the OLC sorts all RABs including HSUPA and DCH servicesinto a descending order.
The top RABs selected. If the integrate priorities of some RABs are identical, the RAB withhigher rate (current rate for DCH RAB and GBR for HSUPA RAB) in the uplink isselected. The number of selected RABs is equal to UL OLC traff release RAB number.
The selected RABs are released directly.
OLC Algorithm for the Release of Some RABs in the Downlink
The OLC algorithm for the release of some RABs in the downlink operates as follows:
Based on the integrate priority, the OLC sorts all RABs into a descending order.
The top-priority RABs are selected. If the integrate priorities of some RABs are identical,
the RAB with higher rate (current rate) The number of selected RABs is equal to DLOLC traff release RAB number .
The selected RABs are directly released.
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Value range: 0 to 10Content: Either parameter specifies the number of RABs released in a UL or DL OLCrelease action.
If the number of RABs that fulfil the criteria for release is smaller than the value of thisparameter, then all the RABs that fulfil the criteria are selected.
The default value of this parameter is 0
Set this parameter through ADD CELLOLC / MOD CELLOLC
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z QoS Parameters Mapped onto the MAC-hs Layer of the NodeB
MAC-hs Discard timer
Scheduling Priority Indicator (SPI)
Guaranteed Bit Rate (GBR)
IMS/SRB: Signaling has a high requirement for transmission delay. If the requirement
cannot be met, the service may be affected. For example, an SRB delay may lead to a
handover delay. The average rate of signaling is lower than 20 kbit/s.
VoIP: The VoIP service is highly delay sensitive. The end-to-end delay of a voice frame
should be shorter than 250 ms. The tolerant frame error rate is about 1%. The average
rate of the VoIP service with the header compressed is about 20 kbit/s.
Streaming: The streams at the receiver end should be continuous. Compared with VoIP,
the streaming service has a relatively low delay sensitivity, because a buffer that can
avoid jitter for several seconds is configured at the receiver end. When the rate of the
streaming service is equal to or higher than the GBR, the QoS can be guaranteed.
BE (background and interactive): The data rate at the service source end can reach a highvalue, for example, several Mbit/s during a burst. The BE service has a low
requirement for transmission delay but has a high requirement for reliable transmission.
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z Huawei RAN10 product supports 4 scheduling algorithms:
Max C/I
RR (Round Robin)
PF (Proportional Fair)
EPF (Enhanced Proportional Fair)
When the HS-DSCH carries only the BE service, the PF scheduling algorithm can make a
tradeoff between user equity and cell throughput. When the HS-DSCH carries more
types of services, such as VoIP, streaming, SRB, and IMS, the HSDPA schedulingalgorithm needs to guarantee the QoS. The reason is that such services have high
requirements for delay or GBR. Based on the PF, the EPF algorithm is designed to
guarantee the QoS of these services as follows.
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ÂDS_PQ_SCHEDULE: SRB/IMS scheduling policy. The SRB and IMS queues are
scheduled before the VoIP, streaming and BE queues. DS means delay sensitive. PQ
means priority queue.
ÂDS_URGENT_SCHEDULE: VoIP scheduling policy. The VoIP queues arescheduled before the streaming and BE queues but after the SRB and IMS queues.
ÂTS_SCHEDULE: streaming/BE scheduling policy. The streaming and BE queues
are scheduled after the SRB, IMS, and VoIP queues. Among the streaming and BE
queues, the resources for GBR are allocated first. The remaining resources are
allocated as required by golden, silver, and copper users. TS means throughput
sensitive
Queue types i.e.
QOS requirement of
different services
EPF
ÂTo select users according to the value of R/r in descending order, where R is
the maximum data rate corresponding to the CQI, and r is the average data
rate of the MAC-hs priority queue.
ÂThe PF scheduler uses the variation in the radio channel qualities of
individual users (for example, multi-user diversity) and provides the user with
an average throughput proportional to its average CQI. This algorithm is a
tradeoff between cell capacity and fairness among users.
CQI,
Average data rate of
the MAC-hs priority
queue
PF
ÂTo select users according to the waiting time of data buffered in the MAC-hspriority queue in descending order. The waiting time is the only factor
considered in this algorithm and therefore the fairness among users can be
guaranteed but the cell capacity degrades because the channel quality is not
taken into account.
Waiting time of databuffered in the
MAC-hs priority
queue
RR
ÂTo select users according to the CQI value in descending order. The radio
channel quality is the only factor considered in this algorithm and therefore the
fairness among users cannot be guaranteed.
CQIMAX C/I
Scheduling PrincipleFactor considered in
algorithmScheduling Algori thm
When the HS-DSCH carries only the BE service, the PF scheduling algorithm can make a
tradeoff between user equity and cell throughput. When the HS-DSCH carries more
types of services, such as VoIP, streaming, SRB, and IMS, the HSDPA schedulingalgorithm needs to guarantee the QoS. The reason is that such services have high
requirements for delay or GBR. Based on the PF, the EPF algorithm is designed to
guarantee the QoS of the multiple services
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Qos guarantee for delay-sensitive service (delay) and throughput-
sensitive service (GBR)
Configurable for SPI
ÂDS_PQ_SCHEDULE: SRB/IMS scheduling policy. The SRB and
IMS queues are scheduled before the VoIP, streaming and BE
queues. DS means delay sensitive. PQ means priority queue.ÂDS_URGENT_SCHEDULE: VoIP scheduling policy. The VoIP
queues are scheduled before the streaming and BE queues but after
the SRB and IMS queues.ÂTS_SCHEDULE: streaming/BE scheduling policy. The streaming
and BE queues are scheduled after the SRB, IMS, and VoIP queues.
Among the streaming and BE queues, the resources for GBR are
allocated first. The remaining resources are allocated as required by
golden, silver, and copper users. TS means throughput sensitive
Queue types i.e.
QOS requirement
of different
services
EPF
Scheduling Principle
Factor
considered in
algorithm
Schedulin
g
Algor ithm
When the HS-DSCH carries more types of services, such as VoIP, streaming, SRB, and
IMS signaling, the HSDPA scheduling algorithm needs to guarantee the QoS. The
reason is that such services have high requirements for delay or GBR. Based on thePF, the EPF algorithm is designed to guarantee the QoS of the following services:
z SRB and IMS have high requirements for service connection delay and handover delay.
In addition, the average traffic volume and the consumption of the Uu interface are low.
Therefore, the algorithm always selects the MAC-hs queues of SRB and IMS first.
z The VoIP service is highly delay sensitive. The maximum delay of MAC-d PDUs in a
queue is specified by the discard timer of the MAC-hs queue. The scheduler needs to
send out the MAC-d PDUs before the discard timer expires. The discard timer is
usually shorter than 100 ms. Therefore, the scheduler has little chance of considering
the channel quality. The scheduler always selects VoIP services after scheduling SRB
and IMS services. Among MAC-hs queues of VoIP, the selection is based on both
delay and channel quality.
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z MAC-hs / MAC-d flow control when Iub interface resource is
not congested
If there is not enough data in the queue, large bandwidth is
allocated
If there is enough data in the queue, the bandwidth that is
close to the rate on the Uu interface is allocated
If there is too much data in the queue, small bandwidth or no
bandwidth is allocated
If the resource on the Uu interface is the bottleneck, or the total traffic volume within the
NodeB (i.e. Mac-hs queue) is low, or the congestion on the Iub interface is managed
by the RNC back pressure algorithm, then the algorithm allocates the capacity basedonly on the rate of each queue on the Uu interface. The MAC-hs performs flow control
for each priority queue periodically.
Whether there is enough data in the queue is judged by the time length of the priority
queue. Time length is defined as the ratio of the length of the queue to the air interface
bit rate of the queue. In this way, the average delay of MAC-d PDU at the MAC-hs
layer is limited within a hundred milliseconds.
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The algorithm actively adjusts the Iub bandwidth based on the congestion
detection
If the Iub is in the congestion due to delay, the Iub bandwidth available for HSDPA is
decreased by a step in direct proportion to the delay buildup
If the Iub is in the due to frame loss, the Iub bandwidth available for HSDPA is
decreased by a big step regardless of the delay buildup
If the Iub is in the congestion released, the Iub bandwidth available for HSDPA is
increased by a smaller step, applying the Policy of increasing slowly, yet decreasing
fast
In a time window of tens of seconds, if consecutive "congestion released" is
detected, the Iub resource is identified as not the bottleneck. In this case, theMAC-hs/MAC-d flow control does not take the Iub bandwidth available for
HSDPA as the limitation of capacity allocation
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z Event 4a triggered by an increase in the transport channel
traffic volume
z In the uplink:
When the traffic volume is higher than the value of Traffic Measurement Event 4A
threshold for a period of time defined by Time to trigger 4A, the UE reports an event4a. No more events 4a are reported during the time defined by Pending time after
trigger 4A.
z In the downlink:
When the traffic volume is higher than the value of Traffic Measurement Event 4A
threshold for a period of time defined by Time to trigger 4A, the RNC reports
internally an event 4a. No more events 4a are reported during the time defined by
Pending time after trigger 4A.
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z Event 4b triggered by a decrease in the transport channel
traffic volume
z In the uplink:
When the traffic volume is lower than the value of Traffic Measurement Event 4B
threshold for a period of time defined by Time to trigger 4B, the UE reports an event4b. No more events 4b are reported during the time defined by Pending time after
trigger 4B.
z In the downlink:
When the traffic volume is lower than the value of Traffic Measurement Event 4B
threshold for a period of time defined by Time to trigger 4B, the RNC reports
internally an event 4b. No more events 4b are reported during the time defined by
Pending time after trigger 4B.
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z Each time a block is received, the number of error blocks within the sliding window is
compared with the Event 5A Threshold parameter. If the number of error blocks is equal to or
greater than the value of the parameter, an event 5A is triggered. When event 5A is triggered,a pending counter is started to prevent further triggering of the event before a certain number
of transport blocks which is specified by Interval Block Number are received.
z The whole process is based on the sliding window mechanism. This window slides with the
arrival of each block. Each time a block is received, the decision on whether to trigger event 5A
is made. The number of error blocks is still counted when the pending timer after trigger timer
works. However, no event 5A is triggered even if the triggering conditions are met.
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z Event F is used to check whether the current transmit power
allows rate upsizing.
z Event F has two measurement thresholds, threshold 1, and
threshold 2.
Event Fa means that the transmit power falls below threshold 1.
Event Fb means that the transmit power rises above threshold 2.
z The threshold is calculated according to the following formula:
z where:
△P is the power difference between current rate and target rate which is calculated in
RNC through the parameters acquired by the simulation and field test results. Pmargin is the event F reporting power margin (Event F reporting power margin).
Event Ea relative threshold is used to protect triggering event report Ea after
upsizing.
Pmax is the maximum DL power of target rate, that is, the maximum configured power
of the target rate.
PO3 is the relative transmit power offset between pilot fields of the DPCCH and
DPDCHs.
z Though these parameters can be changed by using the MML commands on the LMT, it is
strongly recommended that no change be made to them.
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z For rate downsizing based on uplink quality, only the 3-rate
downsizing applies.
If the current rate is MBR, the rate is downsized to the value of
Uplink mid bi t rate threshold.
If the current rate is higher than Uplink full coverage bit rate
and lower than MBR, the rate is downsized to the value of
Uplink full coverage bit rate.
z The Uplink mid bit rate threshold parameter is the same as that described in Rate
Reallocation Based on Traffic Volume.
z The Uplink mid bit rate threshold is the middle bit rate threshold for adjustment of the trafficvolume in the uplink. When Uplink Rate decrease adjust level is 2_Rates, the middle bit rate
for the rate reallocation based on uplink quality is equal to the RB rate closest to the highest
rate divided by two. The bit rate is calculated in the RNC.
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z For rate downsizing based on downlink quality, only the 3-
rate downsizing applies.
If the current rate is MBR, the rate is downsized to the value of
Downlink mid bi t rate threshold.
If the current rate is higher than Downlink fu ll coverage bit
rate and lower than MBR, the rate is downsized to the value of
Downlink fu ll coverage bit rate.
z The Downlink mid bit rate threshold parameter is the same as that described in Rate
Reallocation Based on Traffic Volume.
z The Downlink mid bit rate threshold is the middle bit rate threshold for adjustment of thetraffic volume in the downlink. When Downlink Rate adjust level is 2_Rates, the middle bit
rate for the rate reallocation based on downlink quality is equal to the RB rate closest to the
highest rate divided by two. The bit rate is calculated in the RNC.
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z UE state transition and status of the RRC connection
z The above figure shows the RRC states in UTRA RRC connected mode, including transitions
between UTRA RRC connected mode and GSM connected mode for CS domain services and
transitions between UTRA RRC connected mode and GSM/GPRS packet modes for PSdomain services. It also shows the transitions between idle mode and UTRA RRC connected
mode, and the transitions within UTRA RRC connected mode. Only the state transitions within
the UTRAN connected mode is described herein.
z The principles of UE state transition are as follows:
The state of the UE transits from CELL_DCH to CELL_FACH or from CELL_FACH to
CELL_PCH/URA_PCH if the activity of UE decreases.
The state of the UE transits from CELL_PCH/URA_PCH to CELL_FACH or from
CELL_FACH to CELL_DCH if the activity of UE increases.
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z When the RNC receives the 4b event report, the CELL_DCH to CELL_FACH transition timer
and the uplink and downlink 4b counters are started on the RNC side. If both uplink and
downlink 4b counters of traffic volume event 4b report are greater than or equal to aCELL_DCH to CELL_FACH transition threshold before the timer expires, the UE state transits
from CELL_DCH to CELL_FACH when the timer expires.
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z The CELL_DCH to CELL_FACH transition threshold is the
rounded-down value of the following formula:
CELL_DCH to CELL_FACH transition threshold = [CELL_DCH
to CELL_FACH transition time / (time to trigger + pending time
after trigger) * state transition traffic redundancy coefficient]
z where:
CELL_DCH to CELL_FACH transition time, time to trigger, and pending time after
trigger are set through the parameters listed in the following table. State transition traffic redundancy coefficient is used to avoid detecting UE in low-
activity state incorrectly due to the loss of measurement reports. The value of this
coefficient is set to 80%.
z Parameters used for UE state transition from CELL_DCH to CELL_FACH
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z UE state transition is not applicable in the following cases:
For BE services on the DCH:
If PS_BE_STATE_TRANS_SWITCH is set to OFF, or other
services which cannot perform state transition are configured for
the UE, no state transition is performed on the UE.
z Instead, if both uplink and downlink 4b counters of traffic volume event 4b report are greater
than or equal to a CELL_DCH to CELL_FACH transition threshold when the CELL_DCH to
CELL_FACH transition timer expires, the UE is reconfigured to the low-activity rate that isdefined through the Low activity bit rate threshold parameter.
z However, if the value of Low activity bit rate threshold is greater than or equal to that of
Uplink/Downlink bit rate threshold for DCCC, the reconfiguration to Low activity bit rate
threshold is prohibited.
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z This UE state transition occurs when only the BE service of
the PS domain exists.
z The procedure of UE state transition from CELL_FACH to
CELL_PCH is similar to that of UE state transition from
CELL_DCH to CELL_FACH.
z When the RNC receives the 4b report in which the traffic volume is zero, the CELL_FACH to
CELL_PCH transition timer and the uplink and downlink 4b counters are started on the RNC
side. If both uplink and downlink 4b counters of traffic volume event 4b report are greater thanor equal to a CELL_FACH to CELL_PCH transition threshold before the timer expires, the UE
state transits from CELL_FACH to CELL_PCH when the timer expires.
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z If there is no data transmission for a PS service of a UE, the
connection for the service is released, but the CN reservesthe Packet Data Protocol (PDP) context of the PS service
for the UE.
z When the UE reinitiates the service of this PDP context, it
does not have to apply for the PDP context again. Therefore,
the PS UE is always online.
z When the RNC detects that there is no data transmission for a PS service, the RNC sends a
request to the CN for release of the service. The CN initiates the release procedure, and
requests the RNC to release the corresponding radio resources. However, the CN reservesthe PDP context for the PS UE. When the UE reinitiates the service of this PDP context, it
does not have to apply for the PDP context again. Therefore, the PS UE is always online.
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z When the PDCP entity of a service is set up, timer T1 is started.
z When timer T1 expires and the PDCP entity still detects no data packet either in UL or DL, the
PDCP entity sends the request to the RRC layer for the service release and timer T2 is started.z If the CN does not initiate the service release, and the PDCP still detects no UL or DL data
packet when timer T2 expires, the PDCP entity sends the request again to the RRC layer for
the service release.
If there is only one RAB for the UE in the PS domain, the RNC sends an IU RELEASE
REQUEST message to the CN.
If there is more than one RAB for the UE in the PS domain, the RNC sends an RAB
RELEASE REQUEST message to the CN.
The release cause carried in both messages is "User Inactivity".
z When the CN receives the message, it initiates the release procedure.
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