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An Introduction to Self-Organizing Networks (SON)

Training notes on SON from Dec. 2013

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An Introduction to Self-Organizing Networks (SON)

  1. 1. An Introduction to Self-Organizing Networks (SON) Date: Dec 2013
  2. 2. This material is protected by UK and international copyright laws. Re- distributing this material or a part of it in any form is not permitted without written permission from the copyright holder. There are references to information in public domain (books, websites, standard documents, etc.) in this material. Attempt has been made to give credit to all such references wherever possible. The original copyright holders retain the copyright to their material. This training strives to provide the latest and most correct information. Due to the vastness of standards, constant change and revision, it is possible that the following information may not be entirely up to date or correct. E&OE. Disclaimer and Copyright Information 2
  3. 3. Parameter Update What is happening now in operation of typical cellular system? Performance analysis Optimal parameter calculation In field Remote Measurement User Reports based Drive test based Database Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 3
  4. 4. How SON will benefit? Parameter Update Performance analysis Optimal parameter calculation In field Remote Measurement User Reports based Drive test based Database Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 4
  5. 5. SON Architecture: Centralized 1 2 3 4 5 6 7 8 9 * 0 # 1 2 3 4 5 6 7 8 9 * 0 # 1 2 3 4 5 6 7 8 9 * 0 # Counters/KPIs Sector-specific settings SON Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 5
  6. 6. SON Architecture: Distributed 1 2 3 4 5 6 7 8 9 * 0 # 1 2 3 4 5 6 7 8 9 * 0 # 1 2 3 4 5 6 7 8 9 * 0 # High level reports High level SON policies Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 6
  7. 7. SON Architecture: Hybrid 1 2 3 4 5 6 7 8 9 * 0 # 1 2 3 4 5 6 7 8 9 * 0 # 1 2 3 4 5 6 7 8 9 * 0 # Counters / KPIs High level reports Sector-specific settings High level SON policies SON Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 7
  8. 8. Three stages of SON Self- Configuration • Plug and Play (PnP) • Faster Rollout • Consistency • Licensees, Hardware Inventory and Software build • Efficient resource utilization Self- Optimization • Mobility Robustness Optimisation (MRO) • Mobility Load Balancing (MLB) • Minimization of Drive Testing (MDT) • Fast and proactive parameter optimization • Increased Network performance Self- Healing • Fast, autonomous failure mitigation • Continuous performance monitoring • Faster Network maintenance • More efficient resource utilisation, less effort Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 8
  9. 9. SON Features in Release-8  Release-8 focussed on eNodeB self-configuration.  The following features have been defined in Rel-8  Automatic Neighbour Relationship (ANR) management  Automatic PCI assignment  Automatic Inventory  Automatic Software download  Mobility Load Balancing (MLB)  ANR and MLB are discussed in detail Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 9
  10. 10. eNodeB self-configuration • When eNodeB is switched on for the first time, it requires minimal information as following: – Domain name of NMS – Domain name of its MME’s – Domain name of S-GW • eNodeB contacts the NMS: – Downloads the software (if required) – Download configuration parameters • TAC, PLMN identities, global cell id, power info • The Physical cell Id can be assigned or automatic • Run S1 setup to establish connection with MME’s eNB eNB DHCP / DNS server S-GW MME Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 10
  11. 11. Automatic Neighbour Relationship (ANR)  Due to the location of the UE, it may be able to see more cells than the scanner in an eNB  The UE’s can then report the Cell Id’s in Measurement report  This means the NMS does not need to worry about assigning Neighbour lists to eNB when its setup. • This is particularly important in the case of Small cells whose location can change  Once a new neighbour cell is identified, the eNB should setup X2 connection that can be very useful. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 11
  12. 12. ANR Procedure Measurement Procedure RRC Connection Reconfiguration (Meas) RRC Connection Reconfiguration Complete Measurement Report (Global Cell Id) S1-AP: eNB Configuration Transfer S1-AP: MME Configuration Transfer S1-AP: eNB Configuration Transfer S1-AP: MME Configuration Transfer X2-AP: X2 Setup Request X2-AP: X2 Setup Response eNB MMEeNB NeighbourUE Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 12
  13. 13. Mobility Load Balancing (MLB) • eNB’s can co-operate to balance load between them, thereby increasing network capacity • Even though this procedure was introduced part of Rel-8, there were enhancements in Rel-9 and Rel-10 that has made this procedure much more useful. X2-AP: Resource Status Request X2-AP: Resource Status Response X2-AP: Resource Status Update (Resource block usage, S1 load, available capacity, hardware load, etc.) eNBeNB Neighbour Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 13
  14. 14. MLB Enhancements in Rel-9  Two enhancements have been added in Rel-9: – The neighbour eNB now reports a fourth field in its Resource Status Update, the ‘composite available capacity group’, which indicates the capacity that it has available for load balancing purposes on the uplink and downlink. The original eNB can use this information to assist its handover decision. – There is also a risk that after such a handover that the new base station will hand the mobile straight back to the old one. To prevent this from happening, a new X2 procedure, known as mobility settings change has been introduced. Using this procedure, a base station can ask a neighbour to adjust the thresholds that it is using for measurement reporting, by means of the cell specific offsets. After the adjustment, the mobile should stay in the target cell, instead of being handed back. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 14
  15. 15. MLB Enhancements in Rel-10  In Rel-10, using S1 procedure direct information transfer, a base station can initiate the exchange of radio access network information management (RIM) information with a UMTS or GSM neighbour. The information includes the composite available capacity group in the case of an LTE cell and similar information known as the cell load information group in the case of the other technologies. In turn, this information can trigger a load balancing handover to a UMTS or GSM neighbour. UTRAN MME SGSN GGSN eNB Iu-PS Gn S1-MME S3 RIM Signalling RIM Signalling Relaying RIM Signalling Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 15
  16. 16. SON Features in Release-9  Release-9 has been focussed mainly on Network Optimization procedures.  The following features have been defined in Rel-9  Mobility Robustness (MRO) and Handover Optimization (HO)  RACH Optimization  Load Balancing Optimization  Inter-Cell Interference Co-ordination (ICIC)  Load Balancing Optimization was just discussed  ICIC is covered as part of Interference Management section Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 16
  17. 17. How Self Optimization will work? User reports based Continuous Self Optimization Parameter Update Centralized Autonomous Distributed Autonomous 1 2 3 4 5 6 7 8 9 * 0 # 1 2 3 4 5 6 7 8 9 * 0 # 1 2 3 4 5 6 7 8 9 * 0 # Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 17
  18. 18. Self-configuration/Self-optimization support and inter-operability eNB power on (or cable connected ) (C) Optimization / Adaptation (B) Initial Radio Configuration (A) Basic Setup a-1 : configuration of IP address and detection of OAM a- 2 : authentication of eNB/NW a- 3 : association of aGW a- 4 : downloading of eNB software (and operational parameters) b- 1 : neighbour list configuration B-2 : coverage/capacity related parameter configuration c- 1 : neighbour list optimisation c- 2 : coverage and capacity control Self-Configuration (pre-operational state) Self-Optimisation (operational state) Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 18
  19. 19. Mobility Robustness Optimization (MRO)  MRO was introduced in Rel-9  MRO helps eNB to find the problems in handover and then by using this information, it can adjust the thresholds  Three main causes of failures can be seen in the pictures C AB XX C AB C AB HO Request HO Confirm Drop Re-establish RLF HO Report HO Report X A CB A CB Drop Re-establish RLF XC AB C AB C AB HO Request HO Failure Drop Re-establish RLF HO Report INTRA-RAT LATE HO TRIGGERING XC AB A CB Drop Re-establish RLF HO Report INTRA-RAT EARLY HO TRIGGERING WRONG CELL HANDOVER (RLF AFTER HO) WRONG CELL HANDOVER (RLF BEFORE HO) Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 19
  20. 20. MRO: Late Handover (HO) Triggering Radio Link Failure RRC Connection Reestablishment Handover Procedure On-going Contention based random access RRC Connection Reestablishment Complete UE Information Response UE Information Request X2-AP: RLF Indication (old cell ID, C-RNTI, UE Information) RRC Connection Reestablishment Request (old Cell Id and C-RNTI) New eNBOld eNB UE Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 20
  21. 21. MRO: Early Handover (HO) Triggering RRC Connection Reestablishment (new Cell Id and C-RNTI) Handover to a coverage island of the target cell on new eNB Radio Link Failure X2-AP: RLF Indication (new cell ID, C-RNTI, UE Information) X2-AP: Handover report (handover too early) New eNBOld eNB UE Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 21
  22. 22. MRO: Handover (HO) to Incorrect Cell RRC Connection Reestablishment (new Cell Id and C-RNTI) Handover to wrong cell Radio Link Failure X2-AP: RLF Indication X2-AP: Handover report (handover to wrong cell) (new cell ID, C-RNTI, UE Information) New eNBOld eNB UE Third eNB Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 22
  23. 23. MRO: Release-10 enhancements  MRO was enhanced in Rel-10 to detect unnecessary inter- RAT (Radio Access Technology) handover.  After handover to the other RAT, the new Access Network can configure LTE measurements for the nearby cells.  If the power received is sufficiently high, the network can tell the old eNB that the handover was triggered unnecessarily.  This is informed to the old eNB using the S1-AP direct transfer procedure. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 23
  24. 24. RACH Optimization • The eNB continuously or periodically performs RACH optimization based on the UE feedback and knowledge of neighbouring eNB’s RACH configuration • An optimized RACH will: – Reduce connection time – Help achieve Higher Throughput – Improve cell coverage RRC: UE Information Response RRC: UE Information Request New eNBUE Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 24
  25. 25. RRC UE Information Request message Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 25
  26. 26. RRC UE Information Response message Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 26
  27. 27. PRACH Configuration in X2-Setup X2-AP: X2 Setup Response X2-AP: X2 Setup Request eNB 1 eNB 2 Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 27
  28. 28. SON Features in Release-10 • Release-10 has been focussed mainly on self-healing functions. • The following features have been defined in Rel-10 – Coverage and Capacity Optimization (CCO) – Minimization of Drive Testing (MDT) – enhanced ICIC (eICIC) – Cell outage detection and compensation – Energy savings • eICIC is discussed as part of Interference Management Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 28
  29. 29. Example flowchart of Self-Healing process MONITORING ALARM DIAGNOSIS COMPENSATION Start Monitor TCoSH Trigger self healing process Take measurements and NCL data Analysis and Diagnosis False detection? Update NCL and begin compensation action(s) Performance analysis (faulty cell and neighbouring cells) Alarm cleared? Monitor, Repair and control compensating actions Store alarm information for future analysis Y N Y N Clustering algorithm classifies to determine type of fault and identify necessary compensating action Analyse all alarms, alarm correlation and determine specific compensating actions(s) from neighbouring cell(s) Update Neighbour Cell List (NCL) and begin compensation action via specific neighbouring cells Ensure compensating actions are relaxed when a faulty node has been restored Algorithm continuously monitors system for alarms that Trigger Conditions of Self Healing (TCoSH) TCoSH reached? Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 29
  30. 30. Coverage and Capacity Optimization (CCO) • This has traditionally been the key area of optimization. • This is carried out over a rather long time-scale in the order of days or weeks by capturing and reacting to long-term changes in physical environment, load imbalance, and UL/DL mismatch. • The network should periodically be automatically able to adjust the key RF parameters once the cells have been deployed. • The key RF parameters are: – Power of the cell – Antenna configuration (eg., tilts of the antenna) • CCO is more of an ‘automatic cell planning’. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 30
  31. 31. CCO Examples Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 31
  32. 32. Minimization of Drive Testing (MDT) • Drive testing is one of the biggest cost of running the network after the energy usage • In a traditional network, drive tests have to be done multiple times on different network loads to get an accurate picture of the cells coverage and capacity • To reduce the amount of drive test, MDT feature was introduced in Release-10 • Two types of MDT are defined: – Immediate MDT – Logged MDT • MDT Measurements can be on Control Plane or User Plane. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 32
  33. 33. U-plane and C-plane MDT • The U-plane MDT is operator specific with operator deploying an application on the phone to do this measurements • The C-plane MDT is based on the signalling and would be standardised across all devices and form factors. MDT server MDT server RANRAN UEUE Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 33
  34. 34. Logged v/s Immediate MDT Logged MDT • Measurements in Idle mode • Logging measurements and reporting later on • Optional for the UE to support Immediate MDT • Measurement in Connected mode • Immediate reporting e.g., at RLF • Mandatory for the UE to support Log Coverage Hole Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 34
  35. 35. Logged MDT example • Same amount of measurements as in normal case • Periodical logging : 1280ms~61440ms • logging duration : 10min~120min IDLE measurement occasions Logging Logging interval Logging duration : radio measurements : detailed location info. (if available) : time stamp Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 35
  36. 36. Immediate MDT example • UE can discard RLF info 48 hour after the radio link failure is detected MDT configuration RRCConnectionReestablishmentComplete CONNECTED Re-establishment CONECTECDRLFCoverage Hole Logging Signal strength, location measurement occasions RLF log indication Log retrieval Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 36
  37. 37. Procedure for collecting RLF reports by OAM Trace session activation MDT server (TCE) UE information request UE information response (RLF report) Trace record reporting Cell trace session started Connected mode UE records the RLF report Idle mode Call setup Include RLF report available indication Storing RLF report in trace record RLF/HOF eNB UEOAM Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 37
  38. 38. RRC UE Information Request message Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 38
  39. 39. RRC UE Information Response message Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 39
  40. 40. MDT Enhancements for Rel-11 • MDT was enhanced for Rel-11 to collect not only measurements indicating the network coverage condition but also those indicating the users’ real-life throughput and connectivity issues. • For most cases, the battery consumption is not significantly impacted by MDT. One exception is the ability to request the UE to activate its GNSS receiver for MDT that is introduced in Rel-11, which is expected to involve significant battery power consumption. The operator may choose to handle this by subscription agreements, and only use requested location for subscribers that have consented to this. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 40
  41. 41. Cell Outage Detection and Compensation • Cell Outage Detection and Compensation provides automatic mitigation of eNB failures especially in the case where the eNB equipment is unable to recognize being out of service and has therefore failed to notify OAM of the outage. Detection and Compensation are two distinct cases that cooperate to provide a complete solution: – Cell Outage Detection typically combines multiple separate mechanisms to determine whether an outage has occurred. This is needed to detect the latent fault case, often described as “Sleeping Cell”, where OAM is unaware of the issue. – Cell Outage Compensation techniques are generally only applied after standard soft recovery techniques have failed to restore normal service. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 41
  42. 42. Energy Savings • Power Amplifiers are the biggest source of power consumption for an eNB. • In hotspots where small cells are deployed, they can be switched off during off-peak hours – Switching cells off should not create coverage holes – The eNB is still on, only the transmitter/receiver is switched off • The active users should be handed over to an overlapping cell(s) – It should also inform the cell(s) about the change using X2-AP eNB Configuration Update message. • A neighbour can ask at a later stage to the eNB to switch the cell on using X2-AP Cell Activation Request message. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 42
  43. 43. SON Features in Release-11 • Release-11 has been focussed mainly on Heterogeneous Networks (HetNets). • The following features have been defined in Rel-11 – UTRAN SON Management – Inter-RAT Energy saving management – Automated network management – Troubleshooting – Multi-layer, Multi-RAT HetNets • Will not be covered as part of this training. Confidential – Restricted Distribution © eXplanoTech Ltd., 2013 43

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