eRAN AQM Feature Parameter Description Issue 01 Date 2018-04-10 HUAWEI TECHNOLOGIES CO., LTD. Copyright © Huawei Technologies Co., Ltd. 2018. All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd. Trademarks and Permissions and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd. All other trademarks and trade names mentioned in this document are the property of their respective holders. Notice The purchased products, services and features are stipulated by the contract made between Huawei and the customer. All or part of the products, services and features described in this document may not be within the purchase scope or the usage scope. 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Address: Huawei Industrial Base Bantian, Longgang Shenzhen 518129 People's Republic of China Website: http://www.huawei.com Email: support@huawei.com Contents 1 Change History 1.1 eRAN13.1 01 (2018-04-10) 1.2 eRAN13.1 Draft B (2018-03-30) 1.3 eRAN13.1 Draft A (2018-01-15) (FDD) 2 About This Document 2.1 General Statements 2.2 Applicable RAT 2.3 Features in This Document 3 Overview 4 AQM 4.1 Principles 4.2 Network Analysis 4.2.1 Benefits 4.2.2 Impacts 4.3 Requirements 4.3.1 Licenses 4.3.2 Software 4.3.3 Hardware 4.3.4 Others 4.4 Operation and Maintenance 4.4.1 Data Configuration 4.4.1.1 Data Preparation 4.4.1.2 Using MML Commands 4.4.1.3 Using the CME 4.4.2 Activation Verification 4.4.3 Network Monitoring 5 Parameters 6 Counters 7 Glossary 8 Reference Documents 1 Change History This chapter describes changes not included in the "Parameters", "Counters", "Glossary", and "Reference Documents" chapters. These changes include: • Technical changes Changes in functions and their corresponding parameters • Editorial changes Improvements or revisions to the documentation 1.1 eRAN13.1 01 (2018-04-10) This issue includes the following changes. Technical Changes None Editorial Changes Deleted the descriptions of MLBFD-12100242 Active Queue Management (AQM). 1.2 eRAN13.1 Draft B (2018-03-30) This issue includes the following changes. Technical Changes Change Description Converted MLBFD-12100242 Active Queue Management (AQM) into a commercial feature. Parameter Change None Editorial Changes Added deactivation command examples. For details, see 4.4.1.2 Using MML Commands. 1.3 eRAN13.1 Draft A (2018-01-15) (FDD) This issue introduces the following changes to eRAN12.1 02 (2017-06-29). Technical Changes Change Description Added support for MLBFD-12100242 Active Queue Management (AQM) on DBS3900 LampSite and DBS5900 LampSite. Parameter Change None Editorial Changes Reorganized this document using a new template. 2 About This Document 2.1 General Statements Purpose This document is intended to acquaint readers with: • The technical principles of features and their related parameters • The scenarios where these features are used, the benefits they provide, and the impact they have on networks and functions • Requirements of the operating environment that must be met before feature activation • Parameter configuration required for feature activation, verification of feature activation, and monitoring of feature performance NOTE: This document only provides guidance for feature activation. Feature deployment and feature gains depend on the specifics of the network scenario where the feature is deployed. To achieve the desired gains, contact Huawei professional service engineers. Software Interfaces Any parameters, alarms, counters, or managed objects (MOs) described in this document apply only to the corresponding software release. For future software releases, refer to the corresponding updated product documentation. Trial Features Trial features are features that are not yet ready for full commercial release for certain reasons. For example, the industry chain (terminals/CN) may not be sufficiently compatible. However, these features can still be used for testing purposes or commercial network trials. Anyone who desires to use the trial features shall contact Huawei and enter into a memorandum of understanding (MoU) with Huawei prior to an official application of such trial features. Trial features are not for sale in the current version but customers may try them for free. Customers acknowledge and undertake that trial features may have a certain degree of risk due to absence of commercial testing. Before using them, customers shall fully understand not only the expected benefits of such trial features but also the possible impact they may exert on the network. In addition, customers acknowledge and undertake that since trial features are free, Huawei is not liable for any trial feature malfunctions or any losses incurred by using the trial features. Huawei does not promise that problems with trial features will be resolved in the current version. Huawei reserves the rights to convert trial features into commercial features in later R/C versions. If trial features are converted into commercial features in a later version, customers shall pay a licensing fee to obtain the relevant licenses prior to using the said commercial features. If a customer fails to purchase such a license, the trial feature(s) will be invalidated automatically when the product is upgraded. 2.2 Applicable RAT This document applies to FDD. 2.3 Features in This Document This document describes the following FDD features. Feature ID LBFD-001027 Feature Name Active Queue Management (AQM) 3 Overview Congestion has become a bottleneck in network development due to the limitation of resource capacity and processing capability of networks. End-to-end Transmission Control Protocol (TCP) congestion control techniques have been the primary methods to control IP network congestion. However, edge nodes in a network may not be able to obtain accurate information about network status in time. Therefore, it is hard for these TCP congestion control techniques to solve all congestion problems in the network. To address this issue, congestion control techniques based on intermediate network nodes, such as AQM, have been developed. 4 AQM 4.1 Principles Huawei AQM applies to non-guaranteed bit rate (non-GBR) services. AQM is controlled by the CellAlgoSwitch.AqmAlgoSwitch parameter. As an IP network node, the eNodeB uses AQM to check data packet queue lengths. AQM compares the average queue length with the minimum and maximum congestion thresholds, and then performs the following operations based on the comparison result: • Average queue length ≤ Minimum congestion threshold AQM does not drop any packets because the queue is not congested. • Minimum congestion threshold < Average queue length < Maximum congestion threshold AQM drops some packets because the queue is congested to some extent. The probability of dropping packets increases linearly with: • ▪ The average queue length ▪ The amount of data successfully sent from the core network to the eNodeB Average queue length ≥ Maximum congestion threshold AQM drops every newly arrived packet because the queue is severely congested. The minimum congestion threshold is automatically calculated by the eNodeB based on the real-time air interface data rate. The maximum congestion threshold is equal to the minimum congestion threshold multiplied by eight. As shown in Figure 4-1, the red lines denote the packet loss rates and Max represents the maximum packet loss rate of a non-GBR service in the congestion avoidance area. Figure 4-1 AQM working areas 4.2 Network Analysis 4.2.1 Benefits AQM offers the following benefits: • Proactively detects possible congestion in the queues and minimizes the congestion probability by dropping packets. • Maintains shorter queues to balance the throughput and transmission delay. • Avoids TCP global synchronization caused by simultaneous data overflow of multiple queues. NOTE: TCP global synchronization happens as follows: Data traffic is generally bursty, and data packets arrive at a queue suddenly. A large number of packets will be dropped when the queue becomes full, or is getting close to becoming full. Upon packet loss detection, multiple TCP senders adaptively and sharply decrease their send window. Consequently, the packet arrival rate declines quickly and the network congestion is relieved. After detecting that the network is no longer congested, the TCP senders start to increase transmission rates, which again results in network congestion. In the procedure, each sender decreases and increases transmission rates repeatedly at the same time as other senders. It is recommended that AQM be enabled when both of the following conditions are met: • The average processing delay of downlink Packet Data Convergence Protocol (PDCP) service data units (SDUs) for services carried on data radio bearers (DRBs) is larger than 500 ms per packet. The average processing delay of downlink PDCP SDUs for services carried on DRBs can be monitored by dividing L.Traffic.DL.PktDelay.Time.QCI.x by L.Traffic.DL.PktDelay.Num.QCI.x, where x indicates a QCI. For details about related counters, see Table 4-1. • The value of the Discard timer parameter for the QCI is larger than 500 ms. The parameter value can be queried by running the LST RLCPDCPPARAGROUP command. Table 4-1 Counters related to the average processing delay of downlink PDCP SDUs for services carried on DRBs Counter ID Counter 1526727922 L.Traffic.DL.PktDelay.Time.QCI.6 1526727925 L.Traffic.DL.PktDelay.Time.QCI.7 1526727928 L.Traffic.DL.PktDelay.Time.QCI.8 1526727931 L.Traffic.DL.PktDelay.Time.QCI.9 1526727923 L.Traffic.DL.PktDelay.Num.QCI.6 1526727926 L.Traffic.DL.PktDelay.Num.QCI.7 1526727929 L.Traffic.DL.PktDelay.Num.QCI.8 1526727932 L.Traffic.DL.PktDelay.Num.QCI.9 In the following scenarios, AQM offers no gains or could even have slightly negative effects: • AQM helps reduce only TCP traffic on a bearer when both TCP and User Datagram Protocol (UDP) services are carried on the bearer. • AQM drops packets randomly during network congestion. Therefore, if AQM drops packets of interactive services, user experience in these services deteriorates. • The eNodeB does not enter the congestion state when the data rates of cell edge users (CEUs) fluctuate due to interference, and therefore AQM offers no obvious gains for such UEs. • Dropping packets causes throughput fluctuation, and the fluctuation is more obvious when there are only a small number of TCP connections, for example, one or two connections. • Non-GBR services of a UE will not be congested when the downlink UE throughput on a bearer exceeds 30 Mbit/s. In this scenario, AQM offers no obvious gains. 4.2.2 Impacts Network Impacts AQM has the following impacts on throughput: • • The cell throughput and the throughput of some UEs fluctuate. ▪ If a cell has both CEUs and cell center users (CCUs), AQM will decrease the throughput of CEUs because CEU services are easily congested. CCU services are rarely congested, and therefore AQM will increase the throughput of CCUs. This increased throughput is larger than the decreased throughput for CEUs. In this case, the overall cell throughput increases. ▪ If a cell has only CEUs or CCUs, AQM has little impact on cell throughput. The throughput of GBR services increases. If GBR and non-GBR services coexist in a cell and the actual GBR service rate is less than the subscribed GBR service rate, the decrease in the throughput of non-GBR services possibly brings more scheduling opportunities to GBR services. This may increase the throughput of GBR services. Function Impacts None 4.3 Requirements 4.3.1 Licenses There are no license requirements. 4.3.2 Software Prerequisite Functions None Mutually Exclusive Functions None 4.3.3 Hardware Base Station Models No requirements Boards No requirements RF Modules No requirements 4.3.4 Others None 4.4 Operation and Maintenance 4.4.1 Data Configuration 4.4.1.1 Data Preparation Table 4-2 describes the parameters used for function activation. Table 4-2 Parameters used for activation Parameter Name AQM algorithm switch Parameter ID CellAlgoSwitch.AqmAlgoSwitch 4.4.1.2 Using MML Commands Activation Command Examples //Turning on the AQM algorithm switch MOD CELLALGOSWITCH: LocalCellId=0, AqmAlgoSwitch=AqmAlgoSwitch-1; Deactivation Command Examples //Turning off the AQM algorithm switch MOD CELLALGOSWITCH: LocalCellId=0, AqmAlgoSwitch=AqmAlgoSwitch-0; 4.4.1.3 Using the CME For detailed operations, see CME-based Feature Configuration. 4.4.2 Activation Verification Before the verification, ensure that: • The downlink throughput of the UE is lower than 10 Mbit/s. The downlink throughput can be controlled by decreasing the bandwidth of a cell or by increasing the number of UEs in the cell. • The UE properly accesses the network, connects to the download server, and runs FTP download services. • Multiple large files that are larger than 1 GB and multiple small files are available on the server for downloading. NOTE: Turn The size of a small file can be determined based on the air interface throughput of the UE. If the time for downloading a file while downloading one or multiple large files is within 10s, the file is a small file. The verification procedure is as follows: 1. Run the MOD CELLALGOSWITCH command with the AqmAlgoSwitch option of the CellAlgoSwitch.AqmAlgoSwitch parameter deselected to disable AQM. Then, enable the UE to access the given cell. 2. Download one or more large files and the small files simultaneously. Then, record the small file download latency. Repeat the test and average the recorded values. The average value works as the small file download latency with AQM disabled. 3. Run the MOD CELLALGOSWITCH command with the AqmAlgoSwitch option of the CellAlgoSwitch.AqmAlgoSwitch parameter selected to enable AQM. Then, enable the UE to re-access the given cell. 4. Download one or more large files and the small files simultaneously. Then, record the small file download latency. Repeat the test and average the recorded values. The average value works as the small file download latency with AQM enabled. 5. Compare the two average values and verify that the small file download latency is shortened after AQM is enabled. 4.4.3 Network Monitoring Benefit Monitoring After AQM is enabled, the average processing delay of downlink PDCP SDUs for services carried on DRBs may decrease slightly. The average processing delay of downlink PDCP SDUs for services carried on DRBs can be monitored by dividing L.Traffic.DL.PktDelay.Time.QCI.x by L.Traffic.DL.PktDelay.Num.QCI.x, where x indicates a QCI. For details about related counters, see Table 4-1. Impact Monitoring The number of downlink PDCP SDUs discarded for services carried on DRBs may increase slightly. Table 4-3 describes related counters. Table 4-3 Counters related to the number of downlink PDCP SDUs discarded for services carried on DRBs Counter ID Counter Na 1526726863 L.PDCP.Tx.Disc.Trf.SDU.QCI.6 1526726869 L.PDCP.Tx.Disc.Trf.SDU.QCI.7 1526726875 L.PDCP.Tx.Disc.Trf.SDU.QCI.8 1526726881 L.PDCP.Tx.Disc.Trf.SDU.QCI.9 5 Parameters Table 5-1 Parameters MO Parameter ID MML Command Feature ID CellAlgoSw AqmAlgoSw MOD LBFDCELLALGOSWI 001027/TDLB itch itch TCH FD-001027 LST CELLALGOSWI TCH Feature Name Description Active Queue Managem ent (AQM) Meaning: Indicates whether to enable the Active Queue Management (AQM) algorithm. If this switch is on, the AQM function is enabled to prevent or control congestion. The length of the data transmission queue is maintained at a relatively small value to help achieve an appropriate trade-off between throughput and latency. If this switch is off, the AQM function is disabled. This parameter applies only to LTE FDD and LTE TDD. GUI Value Range: AqmAlgoSwitch Unit: None Parameter ID MO MML Command Feature ID Feature Name Description Actual Value Range: AqmAlgoSwitch Default Value: AqmAlgoSwitch :Off 6 Counters Table 6-1 Counters Counter ID Counter Name Counter Descriptio n Feature ID Feature Name 152672686 3 L.PDCP.Tx.Disc.Trf.SDU.QCI.6 Number of downlink PDCP SDUs discarded for services carried on DRBs with a QCI of 6 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling 152672686 9 L.PDCP.Tx.Disc.Trf.SDU.QCI.7 Number of downlink PDCP SDUs discarded for services carried on DRBs with a QCI of 7 in a cell Multimode: None GSM: None UMTS: None Radio Bearer Managemen t Radio Bearer Managemen t Counter ID Counter Name Counter Descriptio n Feature ID Feature Name LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Basic Scheduling Basic Scheduling 152672687 5 L.PDCP.Tx.Disc.Trf.SDU.QCI.8 Number of downlink PDCP SDUs discarded for services carried on DRBs with a QCI of 8 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling 152672688 1 L.PDCP.Tx.Disc.Trf.SDU.QCI.9 Number of downlink PDCP SDUs discarded for services carried on DRBs with a QCI of 9 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Counter ID Counter Name Counter Descriptio n Feature ID Feature Name TDLBFD Basic -002008 Scheduling LBFD002025 TDLBFD -002025 NR: None 152672792 2 L.Traffic.DL.PktDelay.Time.QCI.6 Total processing delay of downlink PDCP SDUs for DRB services with the QCI of 6 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling 152672792 3 L.Traffic.DL.PktDelay.Num.QCI.6 Number of successfull y transmitted downlink PDCP SDUs for DRB services with the QCI of 6 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling Counter ID Counter Name Counter Descriptio n Feature ID Feature Name LBFD002025 TDLBFD -002025 NR: None 152672792 5 L.Traffic.DL.PktDelay.Time.QCI.7 Total processing delay of downlink PDCP SDUs for DRB services with the QCI of 7 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling 152672792 6 L.Traffic.DL.PktDelay.Num.QCI.7 Number of successfull y transmitted downlink PDCP SDUs for DRB services with the QCI of 7 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling Counter ID Counter Name Counter Descriptio n Feature ID Feature Name TDLBFD -002025 NR: None 152672792 8 L.Traffic.DL.PktDelay.Time.QCI.8 Total processing delay of downlink PDCP SDUs for DRB services with the QCI of 8 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling 152672792 9 L.Traffic.DL.PktDelay.Num.QCI.8 Number of successfull y transmitted downlink PDCP SDUs for DRB services with the QCI of 8 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling Counter ID Counter Name Counter Descriptio n Feature ID Feature Name 152672793 1 L.Traffic.DL.PktDelay.Time.QCI.9 Total processing delay of downlink PDCP SDUs for DRB services with the QCI of 9 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling 152672793 2 L.Traffic.DL.PktDelay.Num.QCI.9 Number of successfull y transmitted downlink PDCP SDUs for DRB services with the QCI of 9 in a cell Multimode: None GSM: None UMTS: None LTE: LBFD002008 TDLBFD -002008 LBFD002025 TDLBFD -002025 NR: None Radio Bearer Managemen t Radio Bearer Managemen t Basic Scheduling Basic Scheduling 152672946 6 L.RLC.FirstPacketDelay.NonGBR.Index Number of Multitimes delay mode: 0 of the first None non-GBR Active Queue Counter ID Counter Name Counter Descriptio n RLC packets ranges within index 0 Feature ID Feature Name GSM: None UMTS: None LTE: LBFD001027 LAOFD001001 NR: None Managemen t (AQM) LTE-A Introduction 152672946 7 L.RLC.FirstPacketDelay.NonGBR.Index Number of times delay 1 of the first non-GBR RLC packets ranges within index 1 Multimode: None GSM: None UMTS: None LTE: LBFD001027 LAOFD001001 NR: None Active Queue Managemen t (AQM) LTE-A Introduction 152672946 8 L.RLC.FirstPacketDelay.NonGBR.Index Number of times delay 2 of the first non-GBR RLC packets ranges within index 2 Multimode: None GSM: None UMTS: None LTE: LBFD001027 LAOFD001001 NR: None Active Queue Managemen t (AQM) LTE-A Introduction Counter ID Counter Name Counter Descriptio n Feature ID Feature Name 152672946 9 L.RLC.FirstPacketDelay.NonGBR.Index Number of times delay 3 of the first non-GBR RLC packets ranges within index 3 Multimode: None GSM: None UMTS: None LTE: LBFD001027 LAOFD001001 NR: None Active Queue Managemen t (AQM) LTE-A Introduction 152672947 0 L.RLC.FirstPacketDelay.NonGBR.Index Number of times delay 4 of the first non-GBR RLC packets ranges within index 4 Multimode: None GSM: None UMTS: None LTE: LBFD001027 LAOFD001001 NR: None Active Queue Managemen t (AQM) LTE-A Introduction 7 Glossary For the acronyms, abbreviations, terms, and definitions, see Glossary. 8 Reference Documents None