Confidentiality: INTERNAL
Introduction to the RAN14.0 Feature CE Overbooking
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Copyright © 2010 Huawei Technologies Technologies Co., Ltd. All rights reserved.
About This Course
This course is based on the radio access network (RAN) 14.0 version. Before you learn this course, ensure that you have completed the following courses based on the RAN 13.0 version:
Dynamic channel element (CE) resource management
Load control
Dynamic selection of the transmission time interval (TTI)
Objectives
After completing this course, you will be able to:
Understand the values and application scenarios of the CE Overbooking feature.
Explain the basic principles of the CE Overbooking feature.
Enable and verify the CE Overbooking feature based on manuals.
Contents 1 Feature Desc riptio n
2 Feature Planning 3 Feature Deployment 4 Performance Monitoring 5 Reference Document and Acronyms & Abbreviations
Feature Description Background The transmission rates of HSUPA UEs are low in most cases due to the high penetration rate of smart phones. In this case, if the RNC reserves a certain amount of credit resources for each admitted UE, the RNC rejects new UE access attempts due to congested uplink credit resources. However, the actual CE usage of the NodeB is low. This problem can be resolved by enabling the TTI switching algorithm. However, if the TTI of most UEs is switched from 2 ms to 10 ms, the benefits of using a 2 ms TTI, such as the peak rate, short delay, and quick scheduling, are unavailable. This reduces user experience.
Benefit The CE Overbooking feature provides the following benefits when the penetration rate of smart phones with an HSUPA TTI of 2 is high and the average uplink throughput is low: Relieves CE congestion during UE access. Increases the number of admitted UEs and the number of UEs with a 2 ms TTI. Increases cell throughput when Uu resources are sufficient.
Technical Principles With this feature, the NodeB adjusts the credit resource usage of admitted UEs based on the actual CE usage, includes the credit resource usage in a private information element (IE) in a measurement report, and sends the report to t he RNC every measurement report period. The RNC then directly uses the reported credit resource usage. The following figure shows the implementation principle of this feature.
UE
RNC
NodeB Uu
Iub
Processing on the NodeB: The credit resources that are consumed by admitted HSUPA UEs are adjusted periodically based on whether the amount of CE resources that are available for HSUPA UEs is smaller than the CE resource usage calculated with the following formula: CE resource usage = Max (CE resources required for ensuring the GBR, CE resources required for transmitting one RLC PDU)
CN Iu
Processing on the RNC: The RNC receives information about consumed credit resources that is reported by the NodeB using proprietary IEs of Iub-interface messages. The RNC performs CAC, LDR, or TTI selection based on the information.
This feature applies only to uplink CE resources.
Functions When dynamic CE resource management is implemented, the CE resources that are available for HSUPA UEs are managed dynamically. That is, idle CEs are recycled when the data transmission rates of HSUPA UEs are low, or no data is transmitted. When this feature is enabled, the credit resource usage of HSUPA UEs with low transmission rates is calculated based on the actual CE usage. The following table lists the methods for calculating consumed credit resources before and after the CE Overbooking feature is enabled.
Whether CE Overbooking Is Enabled Not enabled
Enabled
Method for Calculating the Credit Resource Usage The RNC calculates the credit resource usage as follows: For R99 UEs, the RNC calculates the credit resource usage of admitted UEs based on the maximum bit rate (MBR). For HSUPA UEs, the RNC calculates the credit resource usage of admitted UEs by using the following formula: Credit resource usage = Max (Credit reso urces required for ensuring the GBR, Credit resource s required for transmitting one RLC PDU) The NodeB calculates the credit resource usage as follows: For R99 UEs, the RNC calculates the credit resource usage of admitted UEs based on the MBR. For HSUPA UEs, the NodeB adjusts the credit resource usage of admitted UEs to be less than or equal to the calculation result of the following formula: Credit resource usage = Max (Credit reso urces required for ensuring the GBR, Credit resource s required for transmitting one RLC PDU) If the UEs use a 10 ms TTI, the adjustment is based on the UE rate. If the UEs use a 2 ms TTI, the adjustment is based on the UE rate and the REVDPARA4 parameter.
Related Feature
Required Features
This feature depends on the feature WRFD-010638 Dynamic CE Resource Management.
When CE Overbooking is enabled, it is recommended that DRA_BASE_ADM_CE_BE_TTI_RECFG_SWITCH under DraSwitch be turned on.
Mutually Exclusive Features
None
Impact of CE Overbooking
Impact on resource consumption Congestion of credit resources on the RNC is reduced.
Impact on the system capacity
Enabling this feature affects system capacity as follows:
Relieves congestion of credit resources on the RNC.
Increases the number of admitted UEs and online UEs.
Increases the average cell throughput when Uu resources are sufficient.
When CE resources are insufficient, enabling this feature reduces the resources available to each user, leading to lower per user throughput.
Impact on network performance This feature relieves congestion of credit resources on the RNC and therefore affects network performance as follows:
Increases the success rates for RRC connection setups, RAB setups, and handovers.
Increases the call drop rate due to insufficient CE resources on the NodeB when multiple UEs transmit data simultaneously.
Possibly increases the call drop rate due to increased Uu load when more UEs are admitted.
Application Scenarios and Benefits
Application scenarios
There is a large number of 2 ms HSUPA smart phones in the network.
Credit resources are congested on the RNC.
The average HSUPA throughput is low.
The CE usage on the NodeB is lower than the credit resource usage on the RNC.
Benefits
When the CE usage on the NodeB is low due to the low average throughput of 2 m s HSUPA smart phones, this feature provides the following benefits:
Reduces the congestion of credit resources on the RNC. This increases the success rate of access based on CE resources, and reduces the number of CE resource request failures, probability of TTI switching triggered by CE congestion, and CE based load reshufflings (LDRs).
Increases the number of admitted UEs and the number of HSUPA UEs with a 2 ms TTI.
Contents 1 Feature Description 2 Feature Plann ing
3 Feature Deployment 4 Performance Monitoring 5 Reference Document and Acronyms & Abbreviations
Activation Suggestion and Information Collection
Activation suggestion
Activate CE overbooking when one of the following conditions is met:
There is a large number of 2 ms HSUPA smart phones in the network.
Credit resources are congested on the RNC.
The average HSUPA throughput is low.
The CE usage on the NodeB is lower than the credit resource on the RNC.
Information collection
Check the following counters:
VS.LC.ULCreditUsed.Mean: credit resource usage on the RNC
VS.LC.ULMean.LicenseGroup: CE usage on the NodeB
VS.RRC.Rej.ULCE.Cong and VS.RAC.NewCallReq.Fail.ULCE.Cong: whether credit resources on the RNC are congested
You are advised to enable this feature when credit resources are congested, and the CE usage on the NodeB is much lower than the credit resource usage on the RNC.
Version/License Planning Version RAN14.0 or later versions License The license contolling the CE Overbooking feature is activated on the M2000. Required feature WRFD-010638 Dynamic CE Resource Management
Contents 1 Feature Description 2 Feature Planning 3 Feature Deplo ym ent
4 Performance Monitoring 5 Reference Document and Acronyms & Abbreviations
Feature Deployment
Deployment Requirements
The license controlling the CE Overbooking feature must be obtained.
The feature WRFD-010638 Dynamic CE Resource Management must be enabled.
The requirements on NodeB hardware deployment are as follows:
The BTS3812E, BTS3812A, and BTS3812AE must be configured with the EBBI, EBOI, EULP, or EULPd.
The DBS3800 must be configured with the EBBC or EBBCd. The BBU3806C must be configured with the EBBM.
Activation/Initial Configuration
The 3900 series base stations must be configured with the WBBPb, WBBPd, or WBBPf.
Activate the license and parameter settings for this feature on the M2000.
Feature Verification
Check the VS.NodeB.ULCreditUsed.Mean counter introduced for this feature. If the value is not 0, this feature takes effect.
Contents 1 Feature Description 2 Feature Planning 3 Feature Deployment 4 Pe r f o r m a n c e M o n i t o r i n g
5 Reference Document and Acronyms & Abbreviations
Performance Monitoring
Check whether the CE Overbooking feature takes effect based on the following counters:
VS.NodeB.ULCreditUsed.Mean: added on the RNC and used to measure the credit resource usage at the NodeB level when this feature is enabled
VS.LC.ULCreditUsed.Mean: used to measure the credit resource usage on the RNC
When th is feature takes effect, the value of the V S .N o d e B . U L C r e d i t U s e d . M ea n c o u n t e r o n t h e N o d e B i s s m a l l e r t h a n t h e s u m o f t h e v a l u e o f t h e V S .L C . U L C r ed i t U s e d . M e an c o u n t e r i n a l l t h e c e l l s u n d e r t h e No d e B . W h e n t h i s f e a t u r e t a k e s ef f e c t , i f C E c o n g e s t i o n ( w h i c h c a u s e s a c c e s s r e j e c t s ) s t i l l e x i s t s , an d t h e s t a t i s t i c r e s u l t o f t h e c o u n t e r s a d d e d f o r t h i s f e a t u r e is c l o s e t o t h e L i c e n s e d C E c a p a b i l i t y , c a p a c i t y e x p a n s i o n i s recommended.
Performance Monitoring When CE usage is low due to a large number of 2 ms HSUPA smart
phones in the network, and the average uplink throughput is low, check the following counters to observe performance changes:
VS.RRC.Rej.ULCE.Cong, VS.RAC.NewCallReq.Fail.ULCE.Cong, and VS.HSUPA.RAB.FailEstab.ULCE.Cong: whether the success rate of access based on CE resources increases, and whether the number of
CE resource request failures decreases.
VS.HSUPA.TTI2to10.Succ: whether the probability of TTI switching triggered by CE congestion decreases
VS.MeanRTWP: whether Uu load increases
VS.HSUPA.MeanBitRate: whether the average cell throughput
increases
VS.HSUPA.UE.Mean.TTI2ms: number of HSUPA UEs with a 2 ms TTI
Contents 1 Feature Description 2 Feature Planning 3 Feature Deployment 4 Performance Monitoring 5 Re fe re n c e D o c u m e n t an d A c r o n y m s & A b b r ev i at i o n s
Reference Document WCDMA RAN CE Overbooking Feature Parameter Description
Acronyms & Abbreviations C E : c h a n n e l e le m e n t G B R : g u a r a n t e ed b i t r a t e H S UPA : h i g h s p e e d u p l i n k p a c k e t ac c e s s M B R : m a x i m u m b i t r at e P D U: p a c k e t d a t a u n i t R L C : r ad i o l i n k c o n t r o l RNC: radio netwo rk contro ller T T I: t r a n s m i s s i o n t i m e i n t e r v a l
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