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Huawei Confidential. All Rights Reserved WCDMA Load Control ISSUE1.0 InternalUse 1 In WCDMA system, the load of air interface should be kept under the threshold because too high load can result in Qos getting worse.And the high load level can cause some problems, such as low coverage and capacity ability, the Qos deteriorated etc. It also increase the risk ofsystem instability The load control can maintain the system load level in a stable range to ensure the Qos. InternalUse 2 Object Upon completion this course, you will be able to: Know the load control principles Know the load control realization methods inWCDMA system Know The load control parameters in WCDMA system InternalUse 3 Chapter 1 Load Overview Chapter 2 laod reformingChapter 3 Overload control Chapter 4 Other Load control Algorithm InternalUse 4 Load Measurement Uplink Load Level: By the background noise rise Downlink Load level By the carrier transmission power UL NPRTWPrise noiseq = =11HSDPA cchjj own totalP P p P P + + = =InternalUse 5 Load State load state can be classified to three categories normal, elementary congestion and overload congestion In the stage of elementary congestion and overload congestion, different methods can be employed to make the system back to the normal state Besides state trigged load management, the load adjustment trigged by other conditions can also manage the load state Elementary congestion:system is still stable, but the resource is limited. System needs to be reformed for the potential users Overload congestion:system is not stable, and call drops may happened.Fast overload control should be employed to decrease the system load InternalUse 6 Load state Overload state: System is not stable now. The OLCA can be used, which includes 1 fast TF control 2 release part of users. Load% TH TH olc 100% A section B section C section Normal state: Permit entry Times Congestion state: System is still stable but the resource is very limited. The LDRA can be used, which includes 1 inter-frequency handover 2 decreasing user date rate by DCCC 3 AMRC 4 inter-RAT handover for CS domain services and PS domain services. InternalUse 7 Chapter 1 Load Overview Chapter 2 laod reformingChapter 3 Overload control Chapter 4 Other Load control Algorithm InternalUse 8 Load Reforming Reasons: when the system load arrived to a certain extend, the left resource is very limited, but the system is still stable.In this condition, new coming calls could be rejected by system directly. CharacteristicNo influence to the system stability, but admission rejection often happened PurposeThrough load reforming, load level can be decreased to the state which non admission rejection happenedInternalUse 9 Downlink Load reforming flow Open the downlink LDRA switch Initial the LDM congestion state indicator report LDM indicator Is the cell in elementary congestion? AMRC Yes No Waiting for the LDM indicator No Inter-frequency handover Succeed? No Inter-RAT handover for CS domain services Decrease BE services data rate? No Scheduling by the steps No Inter-RAT handover for PS domainn services No YesYes Yes YesYes Succeed? Succeed?Succeed?Succeed? Can not find any proper solution method InternalUse 10 Each users service priority is defined by a service weight asfollowing formula: The lower P is, the lower possibility of being selected will be For the users who has more RABs (each RAB has a P value), the minimum one is the final P value.User selection times selected the times selected theRate Rate tion Classifica tion Classifica tion Classifica Priority ServiceW KW K W K W K P + + =InternalUse 11 Inter-frequency handover based on loadDecrease the local cell load by handing users over to the lighter load inter-frequency cell There is blind handover target cell with the congestion cell The load difference between the target cell and the congestion cell is greater than a threshold A user my be handed over to other cell, and the handover is called blind handover. The chosen method is based on the equivalent user number. The maximum one, which is less than a upper threshold for the inter-frequency handover equivalent number,should be selected to do the handover. If non users are found, the load control action is failed and do the next LDR action InternalUse 12 Decrease the date rate of BE serviceDecrease the data rate of BE service through the service bandwidth reconfiguration Rank users by the P value, then choose the maximum one, Kclassification>1Krate>Downlink LDR which is target decreasing rate of BE service Execution decrease the users data rate to the target levelPlus one to the Kselected times

InternalUse 13 QoS renegotiation for non-controlled timing servicesDefinitionsThe timing services have the guaranteed bit rate In order to decreasing the load level, the bit rate of non-controlled timing services can be decreased by the QoS renegotiationChoose the PS domain timing services which the P values are greaterThe selected service should take the guaranteed rate to be the maximum negotiation rateRNC transmit the RAB Modification Request message to CN for renegotiation QoSIf RNC does not find any service to do the QoS negotiation, select the next LDR actionInternalUse 14 Inter-RAT handover in CS domain based on load level DecreasingthesystemloadbyhandingCSservicesovertoother systems Select the users by P values. Only single service user can be selected, and the combined services users are not considered Handover the selected user over to 2GOtherwise, select the next LDR action InternalUse 15 Other LDR methods Inter-RAT handover in PS domain based on load level It is the same to the inter-RAT handover in CS domain based on load level Uplink LDR algorithm It is the same to the downlink LDR algorithm InternalUse 16 Chapter 1 Load Overview Chapter 2 laod reformingChapter 3 Overload control Chapter 4 Other Load control Algorithm InternalUse 17 Overload controlWhy are load control needed? Admission control is a kind of insurance for keeping the system stable. But the unpredictable factors like the mobility, data rate can increase the system load How do we know the load increased? for the uplink, because of the background noise rise, power control can not catch up with the requirement. So the QoS may not be ensured for the downlink, the carrier transmission power is close to the maximum transmission power. Call drop may happened because of that. What is the purpose of load control? To ensure the system stability and the QoS of the services, the load control algorithm should make the system back to the normal state as soon as possible. InternalUse 18 Action decision module is the cell inoverload congestion? K dl_olc < N dl_olc ? Downlink TF control Yes release some users No Yes No K dl_olc = 0K dl_olc = K dl_olc+ 1 Yes waiting for LDM indicator Succeed No switch off the periodically action timer olc_action LDM indicator Open the downlink OLCA switch Initial the LDM congestion state indicator report Record the downlink overload congestion state Already initiatedthe OLC timer? Yes Record the downlink overload congestion state The uplink isalso in overload congestion state? No Yes Action Execution module No Initiate the OLC timer olc_action1 InternalUse 19 Overload control Trigger conditions uplink: load factor (RTWP) downlink: transmission carrier power (TCP) Trigger method event reportingperiodic reporting InternalUse 20 Overload control T1 T1 Measured entity Time Measurement Threshold 1 Measurement Threshold 2 T1 Measurement Hysteresis Time T1 Report AReport B Periodic Reports Report APeriodic Report Measurement Reports InternalUse 21 Downlink overload control Downlink TF overload control method Introduction of TF control Decreasing the data rate through changing the TF by adjusting the numbers of TB event reporting When the carrier transmission power is greater than the overload control initiation threshold TH1and lasts longer than Ti, the NodeB will report the transmission power periodically.After the LCC algorithm gets the report, it will inform the MAC-D to do the fast TF control.With the decreasing system load level, the transmission carrier power is also decreasing.After the TCP is less than TH2 and lasts longer than T1, NodeB will stop reporting.Then the fast TF control will stop User Selection Select the users which the P values are greater to do the fast TF control InternalUse 22 Downlink overload control Release usersUser selection Release the users which the P values are greater InternalUse 23 Uplink overload control Uplink overload control is the same to the downlink overload control Fast TF control Release users Release users which the SIR are abnormal Release users According to the priorities InternalUse 24 Overload control The cooperation overload control for both of uplink and downlink Uplink action decision module K ul_olc < N ul_olc ? Uplink TF control Yes Release some users No K ul_olc = K ul_olc + 1 Yes Succeed No Overload Congestion in uplink? Downlink action decision module K dl_olc< N dl_olc ? Downlink TF control Yes Release some users No K dl_olc = K dl_olc+ 1 Yes Succeed No No OLC action execution module Decide to rele ase users inboth uplink and downlink Only release the users who are selected by uplink OLC Decide to release users in uplink or downlink Release users of the link, keep users of another link No decision for the user of downlink and uplink Execute the OLC action of both links T olc_action overtime OLC timer Overload congestion in downlink? Yes Yes Yes Yes Yes No No No InternalUse 25 Overload control The relationship between overload control algorithm and other algorithms with the DCCC algorithm: When the system is in the overload state, transport channels reconfiguration can not be adopted with the CAC algorithm: when the system is in the overload state, system refuse new users directly With the downlink inner-loop control: when the system is in the overload state, NodeBs will neglect the increasing power indication from UE and always decrease the transmission power InternalUse 26 Chapter 1 Load Overview Chapter 2 laod reformingChapter 3 Overload control Chapter 4 Other Load control Algorithm InternalUse 27 Section 1 Load Balance Section 2 Potential Users Control Section 3 The limited transmission resource of Iub Interface

Chapter 4 Other Load control Algorithm InternalUse 28 Load Balance Load balance overview Thefactorssuchasnewcalls,handovers,thechangeabledatarate,the outside interference can cause load unbalance among cells in real network The QoSof some cells may be not good enough because of the very high load level. Meanwhile, other cells resource may be not used fully due to the light load. Toavoidthisphenomenon,somemethodshouldbeusedfortheselection and utilization of resource, such as load balance. Load balance algorithms: Load balance algorithm among inter-frequency cells Load balance algorithm among intra-frequency cells The priority of first algorithm is higher than the second one. InternalUse 29 Load decreased, coverageenlarged Original cell radius Load balance among Intra-frequency cells Load increased,coverage shrank InternalUse 30 Covered by different frequency cells Load balance among Inter-frequency cells f1 Load Level Low f2 High f1 & f2 Middle InternalUse 31 The advantages of load balanceIntra-frequency LDB Users in high load level cells will be handed over to light load ones Inter-frequency LDB Users in high load level cells will be handed over to co-site inter-frequency light load cells InternalUse 32 Intra-frequencyLDBDecrease the P CPICH one step y P tx > P shrink & P CPICH > P CPICH, min n n Wait for next period Increase the P CPICH one step y P tx < P expand & P CPICH < P CPICH,max Measure transmitted carrier power P tx InternalUse 33 LDB among Intra-frequency cells Principal While Load increased, decrease coverage ability to decrease the load level;While the Load decreased, enlarge the coverage ability to share the load of adjacent cells Realization Method Adjust the cell coverage ability by adjusting the transmission power of CPICH InternalUse 34 LDB among Intra-frequency cells Trigger conditionsWhen the percentage of downlink transmission power is greater thanthe threshold for the coverage shrank, decrease the CPICH transmission power periodically When the percentage of downlink transmission power is less than the threshold for the coverage enlarged, increase the CPICH transmission power periodically CPICH power step should be considered very carefully The percentage of downlink transmission power Threshold for the coverage shrank Threshold for the coverage enlarged InternalUse 35 LDB among inter-frequency cells nPtx,max >P adjust & Ptx,max - Ptx,min> Pdifference Wait for next period i < N? Get P tx,max and P tx,minfrom P tx (m) Measure transmitted carrier power P tx (m),m=1,2,...M i + 1 n Select one suitable user in the highest loaded cell, and attempt to be handover to the lowest loaded cell. y y Initialize the hard handover attempt counter i=0 y Successful? InternalUse 36 LDB among inter-frequency cells Trigger conditionsThe load of a cell is beyond the threshold of high load level The level difference between the highest load cell and the lightest load one is beyond the threshold for the difference the threshold of high load level the threshold for the difference between the highest load cell and the lightest load oneThe percentage of downlinktransmission power InternalUse 37 ( )WRN EWRN Eireferencereference o bi ii o b=) / () / (NTFvUser selection Selection criteria: 1Users are not in soft handover 2Users are not in the different SRNC and CRNC 3Based on the users NTF InternalUse 38 Section 1 Load Balance Section 2 Potential Users Control Section 3 The limited transmission resource of Iub Interface

Chapter 4 Other Load control Algorithm InternalUse 39 Potential users control In WCDMA network, when UEs are in IDLE, CELL_FACHCELL_PCH and URA_PCH, their mobility management is realized by the cell reselection. Through cell reselection, the purpose of PUC algorithm, which the potential users can not stay in high load level cell, can be realized PUC introduction InternalUse 40 Potential users control cell reselection is the mainly method for the PUC the cell load is decided to be high when it is greater than the upper threshold of load level plus a hysteresis the cell load is decided to be light when it is less than the down threshold of load level sub a hysteresis According to the load grade, RNC can adjust the references QOffset1Sn, QOffset2Sn and Sintersearch, which is the measurement initial threshold for inter-frequency cell reselection, to control the UE camping cell in the process of cell reselectionRealization method InternalUse 41 Potential users control NodeBs report the total transmission power periodically Trigged PUC periodically Decide the cell load grade according to the total carrier transmission power Configure the references Sintersearch, Qoffset1(s,n) and Qoffset2(s,n) according to cell load grade Refresh the corresponding system information unit of SIB3 and SIB11 Realization method InternalUse 42 Potential users control Utilize the characters of inter-frequency cell reselectionSintersearch:Augmenting this value can initial the inter-frequency cell reselection earlierDecreasing this value can initial the inter-frequency cell reselection later Qoffset1(s,n)the R criteria based on RSC Augmenting this value, the possibility which UE selects adjacent cell will be lower Decreasing this value, the possibility which UE selects adjacent cell will be higher Qoffset2(s,n)the R criteria based on Ec/I0 Augmenting this value, the possibility which UE selects adjacent cell will be lower Decreasing this value, the possibility which UE selects adjacent cell will be higher Adjustment method InternalUse 43 Potential users control Remark PUC algorithm is only used for load balance among inter-frequency cells because of the following reasons: Usually, the edge of cell is soft handover area When UEs initiate a connection with a better cell after cell reselection, it still has to setup a connection with adjacent cells in soft handover area. In this case, the PUC algorithm is useless This algorithm does not consider the cell load which belongs to other RNC because the load information can not be exchanged through Iur interface InternalUse 44 Section 1 Load Balance Section 2 Potential Users Control Section 3 The limited transmission resource of Iub Interface

Chapter 4 Other Load control Algorithm InternalUse 45 The limited transmission resource of Iub Interface In some scenarios, the Iub transmission resource is limited very serious In order to letting more users obtained the services, decreasing some users data rate is feasible method When the Iub resource is limited very serious, the data rate of BE services can be decreased to ensure the Qos of high priority servicesInternalUse 46 The limited transmission resource of Iub Interface Methods A timer will be initiated whenever receiving a congestion warning from Iub interface RNC will choose a NodeB randomly, then rank the BE services by P value descendingly Choose the users ranked in the first part of queue, then decrease the data arte to the guaranteed rateThe selective decreasing rate for BE services has to be done again when the timer expired. Then system will initial the timer againClear the timer if the warning went offHuawei Confidential. All Rights Reserved


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