Operating Documentation,
Issue 03
Automatic Neighbor Relation
(ANR)
DN0989276
Issue 04A
Approval Date 2014-06-16
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Table of Contents
This document has 65 pages Summary of changes... 8 1 Introduction to Automatic Neighbor Relation (ANR)...9 2 Automatic Neighbor Relation (ANR) Features... 10 2.1 LTE724: LTE Automatic Neighbor Cell Configuration...11 2.2 LTE539: Central ANR...12 2.3 LTE492: Automatic Neighbor Relation (ANR)... 12 2.4 LTE510: Synchronization of InterRAT Neighbors...13 2.5 LTE783: ANR InterRAT UTRAN...13 2.6 LTE784: ANR InterRAT GERAN... 13 2.7 LTE782: ANR Fully UE based... 14 2.8 LTE771: Optimization of Intra-LTE Neighbor Relations...14 2.9 LTE1019: SON Reports...15 2.10 LTE1045: Full SON Support for Distributed Sites... 15 2.11 LTE1222: SON Automation Modes... 15 2.12 LTE507: Inter-RAT Neighbor Relation Optimization...15 2.13 LTE1383: Cell-specific Neighbor Relation/PCI Handling... 16 2.14 LTE556: ANR Intra-LTE, Inter-frequency - UE Based... 16 2.15 LTE1708: Extend Maximum Number of X2 Links...16 3 Architecture of Automatic Neighbor Relation (ANR)... 17 4 Functional Description for ANR... 18 4.1 LTE724: Automatic Neighbor Cell Configuration...18 4.1.1 Benefits... 18 4.1.2 Pre-planning... 18 4.1.3 Commissioning and integration phase of a new eNB... 18 4.1.4 Neighbor cell update... 18 4.1.5 Configuration data exchange via X2... 19 4.1.6 LTE724 Interaction with Common Object Model... 20 4.2 LTE539: Central ANR...20 4.2.1 Functional overview... 20 4.2.1.1 NetAct Optimizer... 21 4.2.1.2 NetAct Configurator...23 4.2.1.3 Integration in the auto-configuration workflow...23 4.3 External LTE Cell Support in NetAct... 24 4.3.1 NetAct SON features support for the external LTE cells... 24 4.3.2 Intra-system adjacency border area management...25 4.3.3 External LTE cell support for the LTE492: ANR in NetAct...25 4.3.4 External LTE object support for LTE468: PCI Management in NetAct... 254.3.5 External LTE cell support for the LTE539: Central ANR in NetAct... 26 4.3.6 External LTE cell support for the LTE581: PRACH Management in NetAct... 26 4.4 X2 link management... 26 4.4.1 oamControlled X2 links... 26 4.4.2 enbControlled X2 links... 26 4.4.2.1 Outgoing enbControlled X2 link (establishment triggered by the eNB)... 27 4.4.2.2 Incoming enbControlled X2 link (establishment triggered by neighbor eNB)... 27 4.5 LTE1708: Extend Maximum Number of X2 Links...28 4.6 LTE492: Automatic Neighbor Relation (ANR) ... 29 4.6.1 Prerequisites... 29 4.6.2 Functional overview/details... 30 4.6.2.1 NetAct Optimizer: neighbor evaluation procedure... 32 4.6.2.2 NetAct Configurator: automated neighbor site IP connectivity configuration completion... 32 4.6.2.3 Use cases... 33 4.7 Neighbor relation clean up in the NetAct...33 4.7.1 Optimizer: select and delete...33 4.7.2 Configurator: delete consistently... 34 4.8 LTE510: Synchronization of InterRAT Neighbors...34 4.9 LTE783: ANR InterRAT UTRAN...35 4.10 LTE784: ANR InterRAT GERAN... 38 4.11 LTE782: ANR Fully UE based... 40 4.12 LTE771: Optimization of Intra-LTE Neighbor Relations...45 4.12.1 Functional description... 45 4.12.1.1 RAN system level scope... 47 4.13 LTE1019: SON Reports...48 4.14 LTE1045: Full SON Support for Distributed Sites... 49 4.15 LTE1222: SON Automation Modes ... 52 4.16 LTE507: Inter-RAT Neighbor Relation Optimization...53 4.17 LTE1383: Cell-specific Neighbor Relation/PCI Handling... 53 4.18 LTE556: ANR Intra-LTE, Inter-frequency - UE Based... 57 5 Management data for ANR... 58 6 Operating Tasks Related to ANR... 59 6.1 LTE771: Optimization of Intra-LTE Neighbor Relations...59 6.1.1 Scheduled workflow for LTE771: Optimization of Intra-LTE Neighbor Relations...59 6.1.2 ANR Optimization...60 6.2 LTE782: ANR - UE based... 60 6.2.1 UE-based ANR Retrieval by eNB...60 6.3 LTE783: ANR InterRAT UTRAN...61 6.3.1 The establishment of NR for Inter-RAT UTRAN...61
6.3.2 New UTRAN neighborship generation during LTE auto-configuration...62 6.4 LTE784: ANR InterRAT GERAN... 62 6.4.1 Establishment of NR for Inter-RAT GERAN... 62 6.4.2 New GERAN neighbor ship generation during LTE auto-configuration...63 6.5 LTE539: Central ANR...64 6.5.1 Central ANR for New eNBs... 64
List of Figures
Figure 1 Architecture of ANR...17 Figure 2 Configuration of neighbor cells... 19 Figure 3 Border area management - info model...25 Figure 4 LTE492: ANR...29 Figure 5 LNREL deletion... 34 Figure 6 LTE510 Synchronization of InterRAT Neighbors... 35 Figure 7 LTE784: ANR InterRAT GERAN...39 Figure 8 ANR principle...41 Figure 9 LTE771: Optimization of Intra-LTE Neighbor Relations... 47 Figure 10 Centralized and decentralized parameter change...49 Figure 11 LTE NRs of eNB-A for a given LTE carrier... 55 Figure 12 UE-based ANR Retrieval by eNB... 61List of Tables
Table 1 ANR features... 11 Table 2 Minimum number of supported neighbor objects... 28
Summary of changes
Changes between issues 04 (2014-03-24, RL60) and 04A (2014-06-16, RL60) All chapters: editorial changes
The following chapters have been updated:
• LTE1222: SON Automation Modes
• LTE782: ANR Fully UE based
• LTE771: Optimization of Intra-LTE Neighbor Relations
Changes between issues 03B (2013-12-05, RL50) and 04 (2014-03-24, RL60) All chapters: editorial changes
The following features have been added:
• LTE556: ANR Intra-LTE, Inter-frequency - UE Based
• LTE1708: Extend Maximum Number of X2 Links
Changes between issues 03A (2013-09-20, RL50) and 03B (2013-12-05, RL50) The ANR principle figure has been changed.
1 Introduction to Automatic Neighbor Relation
(ANR)
3GPP defines LTE network support for the ANR feature in 3GPP TS 32.511 Automatic Neighbor Relation (ANR) management. NSN supports ANR on a different level of interworking of eNB and NetAct, to give the operator full control of the the neighbor relation management. For all ANR functions it is the goal to provide the neighbor cell configuration data at the source eNB to support a handover to the target eNB.Basic X2 Link Establishment
The establishment of neighbors is based on information, which is prepared in a pre planning phase. Only a subset of standard configuration information is required. For all neighbor cells only the Node-ID and the IP address of the neighbor LTE eNB hosting the expected neighbor cells need to be configured by offline pre-planning. All other configuration information for cells of neighbor LTE eNBs are automatically derived and updated via the X2 interface. For the LTE782: ANR-UE-based feature, this info is autonomously retrieved by the eNB.
ANR-Intra-LTE
If an unknown physical cell ID is reported by UE, the eNB derives the cell configuration information of the LTE neighbor cell (that is ECGI, TAC, and supported PLMNs) with the help of the UE. This information is stored for further use by mobility management in the eNB.ANR-Optimization of Intra-LTE neighbor relations
Optimization of Intra-LTE neighbor relations is a part of the overall ANR functionality. LTE
neighbor cells will be discovered and added by ANR features or manual input by the operator. The NetAct Optimizer evaluates all current relations between neighboring LTE cells if they are still valid and reliable candidates to be a handover destination. When the outcome results in an inefficient neighbor relation the according cell relation may be blacklisted for handover.
ANR to other Radio Access Technology (UTRAN)
The features are requested as centralized SON features. The O&M based inter-RAT feature supports operator initiated and/or automatic set-up and maintenance of neighborship to other RAT (radio access technology). The target of these features is to keep the operator's effort low for inter-RAT neighborship configuration based on site planning data. For more information on SON management, see:
• Functional area description: SON management
2 Automatic Neighbor Relation (ANR) Features
NSN features offer the following ANR features: • LTE724: LTE Automatic Neighbor Cell Configuration Manual setup of the X2 link target to a neighbor eNB to learn neighbor information. • LTE539: Central ANR Automatic preparation of X2 link targets from the NetAct-known neighbor eNBs. • LTE492: Automatic Neighbor Relation (ANR) Provision of a look-up table for X2 link targets from the NetAct-known neighbor eNBs. • LTE782: ANR Fully UE based Learning the neighbor information as 3GPP TS 32.511 ANR, without the NetAct support. • LTE783: ANR InterRAT UTRAN Automatic configuration of UTRAN target cells and control data from the NetAct-known neighbor RNCs. • LTE784: ANR InterRAT GERAN Automatic configuration of GERAN target cells and control data from the NetAct-known neighbor BSCs. • LTE510: Synchronization of InterRAT Neighbors Establishing a new inter-RAT NRs when new UTRAN/GERAN cells are created within the optimization scope of an existing LTE cell. • LTE1019: SON reports Provision of a report mechanism for the parameter changes done in the network. • LTE1045: Full SON support for distributed sites Introduction of antenna site location information differentiation for distributed site deployments.• LTE1222: SON Automation Modes
Automatization of the inter-RAT neighbor-related features and optimization of intra-LTE. • LTE507: Inter-RAT Neighbor Relation Optimization Managing and optimizing the existing inter-RAT neighbor relations (NRs) between: LTE and WCDMA and/or LTE and GERAN for a defined set of mobility procedures. • LTE1383: Cell-specific Neighbor Relation/PCI Handling Supporting of 64 X2-links, cell-specific NR and PCI handling. • LTE556: ANR Intra-LTE, Inter-frequency - UE Based Establishment of new NRs between intra-LTE cells with different frequencies. • LTE1708: Extend Maximum Number of X2 Links Extending the number of supported X2 links within the eNB to 256 for FSMr3 and to 128 for FSMr2. For all features, the NetAct supports suitable means for activation, control, and monitoring of the ANR features. For more information on the management, see NetAct Customer Documentation or the online help support. This functional area description aims to provide the content of the ANR features with focus on the eNB. Table 1: ANR features shows all features related to ANR per release. Automatic Neighbor Relation (ANR) Features Automatic Neighbor Relation (ANR)
Table 1 ANR features
Feature: Related documents Release
LTE724: LTE Automatic Neighbor Cell Configuration
FAD: ANR RL09
LTE539: Central ANR FAD: ANR RL10
LTE492: Automatic Neighbor Relation (ANR) FAD: ANR RL20
LTE510: Synchronization of InterRAT Neighbors
FAD: ANR RL30
LTE783: ANR InterRAT UTRAN FAD: ANR RL30
LTE784: ANR InterRAT GERAN FAD: ANR RL30
LTE782: ANR Fully UE based FAD: ANR RL30
LTE771: Optimization of Neighbor Relations FAD: ANR RL30
LTE1019: SON reports FAD: ANR RL40
LTE1045: Full SON Support for Distributed Sites
FAD: ANR RL40
LTE1222: SON Automation Modes FAD: ANR RL40
LTE507: Inter-RAT Neighbor Relation Optimization
FAD: ANR RL50
LTE1383: Cell-specific Neighbor Relation/PCI Handling
FAD: ANR RL50
LTE556: ANR Intra-LTE, Inter-frequency - UE Based
FAD: ANR RL60
LTE1708: Extend Maximum Number of X2 Links
FAD: ANR RL60
2.1 LTE724: LTE Automatic Neighbor Cell
Configuration
This feature supports manual configuration of intra-LTE neighbors for all cells of the target and source eNB by the operator. With the configuration of the neighbor identification, the X2 link is established and both eNB exchange their cell configuration to be prepared for HO. The neighbor identification can be prepared in a pre-planning phase or configured during operation of the eNBs. Automatic Neighbor Relation (ANR) Automatic Neighbor Relation (ANR) FeaturesOnly a subset of the standard information configuration is required. Off-line planning applies to the Node-ID and/or the IP address of the neighbor LTE eNB hosting the expected neighbor cells. All other configuration information for cells of neighbor LTE eNBs are automatically derived and updated via the X2 interface.
2.2 LTE539: Central ANR
The LTE539: Central ANR feature is a centralized SON process for automatic neighbor relation (ANR) preparation. During auto-configuration (see the LTE720: SON LTE Auto
Configuration feature) or manually triggered by the operator at the NetAct, the NetAct
prepares for these eNB the most suitable neighbor cells based on geo-locations. The NetAct considers all LTE cells (inter- or intra-frequency) known within its scope. In addition the operator can add external LTE cells in border situations. The NetAct generates the configuration data that an operator would manually generate for the
LTE724: Automatic Neighbor Cell Configuration feature. The NetAct supports an
operator policy to define the wanted minimum and maximum number of neighbor cells per served cell. From that all closest intra-LTE neighbor cells within a distance limit are collected and their hosting eNB configuration is prepared.
2.3 LTE492: Automatic Neighbor Relation (ANR)
The LTE492: Automatic Neighbor Relation (ANR) feature is a hybrid SON process for ANR finding. During auto configuration (see the LTE720: SON LTE Auto Configuration feature) or manually triggered configuration by the operator at the NetAct, the NetAct prepares for these eNBs a look-up table for resolving the neighbor eNB X2-IP address from a newly found PCI value. The look-up table keeps a wider number of most suitable neighbor cells based on geo-locations for this eNB. The NetAct considers all LTE cells (inter- or intra-frequency) known within its scope. In addition, the operator can add external LTE cells in border situations. During the operation of the eNB, the mobility measurements are activated for each UE. If the UE measurement reports show PCI values without existing configuration, the eNB will search the PCI value in the look-up table. If the value is found, the eNB itself generates this configuration data, which an operator would manually generate for the LTE724: Automatic Neighbor Cell Configuration feature. The target eNB supports the LTE492: Automatic Neighbor Relation (ANR) feature as well, and will accept incoming X2 link setup from the other peer. The X2 link set-up happens as for the LTE724: Automatic Neighbor Cell Configuration feature. The LTE492:
Automatic Neighbor Relation (ANR) feature allows still manual neighbor configuration, or
even running of the LTE539: Central ANR feature.
2.4 LTE510: Synchronization of InterRAT Neighbors
The LTE510: Synchronization of InterRAT Neighbors feature is a centralized SON process for automatic inter-RAT neighbor relation (IRAT-ANR) preparation. During normal operation by a scheduled, or manually triggered process by the operator at the NetAct, the NetAct checks for new inter-RAT cells and selects those eNB, for which this inter-RAT cell would be a suitable inter-RAT neighbor cells based on geo-locations. The NetAct considers all inter-RAT (GERAN or UTRAN) cells for all LTE cells. In addition, the operator can add external inter-RAT cells in border situations. The NetAct activates for the selected eNBs either the LTE783: ANR InterRAT UTRAN feature or the
LTE784:ANR InterRAT GERAN feature to set-up the wanted inter-RAT neighbor
configuration.
2.5 LTE783: ANR InterRAT UTRAN
The automatic planning of neighbor relations to UTRAN cells is done on NMS (network management system) level with the help of the NetAct Configurator and Optimizer. This feature prepares neighbor relations for each LTE cell in the optimization scope and UTRAN automatically based on current LTE and legacy UTRAN network configuration data with an intelligent algorithm in Optimizer to identify possible UTRAN neighbor cells. The established relations are updated and synchronized automatically in case of changes occurring at the UTRAN side (deletion of cell or change of the parameters), ensuring up-to-date inter-RAT neighbor relationships. This functionality is a part of auto configuration process of the LTE site. In addition, it is possible to trigger the functionality manually. The NetAct configures at the eNB plan file the inter-RAT cell configuration table according to the UTRAN cell configuration. In addition, the dependent inter-RAT SIB, measurement and redirect configuration is aligned. The NetAct supports inter-RAT UTRAN user-templates to control inter-RAT configuration data.
2.6 LTE784: ANR InterRAT GERAN
The automatic planning of neighbor relations to GERAN cells is done on NMS level with the help of the NetAct Configurator and Optimizer. This feature prepares neighbor relations for each LTE cell in the optimization scope and GERAN automatically based on current LTE and legacy GERAN network configuration data with an intelligent algorithm in Optimizer to identify possible GERAN neighbor cells. The established relations are updated/synchronized automatically if any changes occur at the GERAN side (for example, deletion of cell or change of the parameters), ensuring up-to-date inter-RAT neighbor relationships. This functionality is a part of the auto-configuration process of the LTE site. In addition, it is possible to trigger the functionality manually. Automatic Neighbor Relation (ANR) Automatic Neighbor Relation (ANR) Features
The NetAct configures at the eNB plan file the inter-RAT cell configuration table according to the GERAN cell configuration. In addition, the dependent inter-RAT SIB, measurement and redirect configuration is aligned. The NetAct supports inter-RAT GERAN user-templates to control inter-RAT configuration data.
2.7 LTE782: ANR Fully UE based
This feature covers Intra-LTE, Intra-frequency automatic neighbor relation configuration (ANR). The neighbor relations stored by the eNB provide information about the neighbor cell environment visible to each eNB cell. This information is persistently stored for further use by the mobility management in the eNB. In this situation, S1 HO is supported towards this neighbor cell. Furthermore, the eNB resolves the X2 C-plane IP address of the node serving the discovered LTE neighbor cell via S1 interface using the SON information exchange procedure and establishes the X2 connection to exchange neighbor cell information with the newly discovered site.
In addition to the LTE724: Automatic Neighbor Cell Configuration feature in RL30 the LTE neighbor cell configuration is persistently stored at the eNB. This is a common approach for all ANR features. According to the activated ANR features, the X2 link can be re-established after each link drop based on:
• oamControlled LNADJ: the IP address
• enbControlled LNADJ and the LTE492: ANR feature activated: the PCI/IP
address table with any PCI of a child LNADJL object
• enbControlled LNADJ and the LTE782: ANR Fully UE based feature activated:
the MME-S1 based IP address resolution from global eNB ID, in case LTE492: ANR is also activated, then eNB tries first to check the PCI/IP address table. For all cells on the eNB the persistent neighbor cell information allows S1 handover, while X2 handover is preferred if the X2-link is active. Whenever one camping UE sees one of these known neighbor cells and this neighbor is selected as HO target, then within this cell a neighbor cell relation is established. This feature needs no support from the NetAct level, even the found LTE cells can remain unknown to the NetAct.
2.8 LTE771: Optimization of Intra-LTE Neighbor
Relations
The NetAct Optimizer supervises all registered cell relations between the neighboring LTE cells if they are still valid and reliable candidates to be a handover destination. When the outcome results in an inefficient neighbor relation the relevant cell relation might be blacklisted for handover. Automatic Neighbor Relation (ANR) Features Automatic Neighbor Relation (ANR)2.9 LTE1019: SON Reports
The LTE1019: SON Reports feature provides a report mechanism for the parameter changes made in the network, especially with focus to automatic changes made for configuration parameters.
2.10 LTE1045: Full SON Support for Distributed Sites
This feature includes the introduction of antenna site location information differentiation for distributed site deployments.
The SON algorithms calculating possible neighbor sites are adapted to consider the site location info from antenna.
g
Repeater supportThe LTE1195: FHCC Flexi 850 Repeater Interface Unit (RIU) or similar
LTE1106: FHCB Flexi RRH 2TX 850 Low Power for Optical Repeater Interface
and LTE1337: FHEC Flexi RRH 2TX 1800 Low Power features represent repeater units that are usually installed within the same coverage area as the macro cell. Therefore, the LTE1045: Full SON Support for Distributed Sites feature has to check only for the macro cell. As repeater supports a dedicated mode, where a repeater is configured like a normal cell with up to 20 km distance, then operator needs to configure the correct antenna geo-location data at NetAct. The LTE1045: Full SON Support for Distributed Sites feature does not check consistency of such special deployments, as those are often 3rd party products.
2.11 LTE1222: SON Automation Modes
With the LTE1222: SON Automation Modes feature the inter-RAT neighbor-related features and optimization of intra-LTE are executed in an automatic manner.
2.12 LTE507: Inter-RAT Neighbor Relation Optimization
The LTE507: Inter-RAT Neighbor Relation Optimization feature enables automatic blacklisting the individual mobility procedure of the existing inter-RAT NR. To be considered by this feature, the NR must have the following parameter settings: the
LNRELx.nrControl parameter set to AUTOMATIC and the LNRELx.xyzAllowed
parameter set to ALLOWED.
2.13 LTE1383: Cell-specific Neighbor Relation/PCI
Handling
Cell-specific NR and PCI handling is needed to cope with network deployments with distributed sites, respectively for non-optimized network environments, for which handling of NRs per eNB is not sufficient. This enables the eNB to handle situations, where different neighbor cells with the same PCI and frequency are visible for different eNB cells. The LTE1383: Cell-specific Neighbor Relation/PCI Handling feature also provides the extension of supported X2-links number to 64.2.14 LTE556: ANR Intra-LTE, Inter-frequency - UE Based
This feature enables establishment of new neighbor relations (NRs) between intra-LTE cells with different frequencies. Automatic Neighbor Relation (ANR) for intra-LTE, inter-frequency neighbor cells is based on UE measurements search on demand for the currently unknown intra-LTE, inter-frequency neighbor cells. It can be started to properly update and configure the neighbor cell list for adjacent LTE cells.
2.15 LTE1708: Extend Maximum Number of X2 Links
The LTE1708: Extend Maximum Number of X2 Links feature extends the number of supported X2 links within the eNB from 64 to 256 X2 links for FSMr3 and from 64 to 128 for FSMr2.
3 Architecture of Automatic Neighbor Relation
(ANR)
Figure 1: Architecture of ANR shows the architecture of FAD: ANR. Figure 1 Architecture of ANR •Triggered!by!the!UE!!measurements •Physical!ID!- Global!ID!Mapping!done by!the!UE!Measurements;!required: - UE!supporting ANR •Triggered!by!the!UE!measurements •Physical!ID!- Global!ID mapping!done!by!the!NetAct -!no!UE!supporting ANR!needed •No!pre-configuration •Neighbor!cell!entries!automatic completed!by!the!NetAct •No!UE support •Neighbors!preconfigured!by IP address •Neighbor!cell!entries completed automatically!by!the!NetAct!during pre-planning Rl09LTE539: Central ANR
LTE492: ANR!for!LTE LTE782: ANR!for!LTE fully!UE!based LTE724: Automatic Adjacent!Cell!Configuration - MME!support!for!IP address!resolution •Report!of!the!automatic parameter!changes!in!the!network LTE1019:!SON!reports Additional!information!about!the applied!change!to!the!user • •Introduction!of!antenna!location!information differentiation!for!distributed!site!deployments LTE1045:!Full!SON!Support for!Distributed!Sites The!SON!algorithms!calculating possible!neighbor!sites!adapted • •Additional!functionality!for!the existing!centralized!SON!features LTE1222:!SON Automation
Modes •Inter-RAT auto!setup!and
scheduled!optimization Optimizing!the!existing!inter-RAT NRs!between!LTE!and!2G/3G for!mobility!procedures LTE507:!Inter-RAT Neighbor!Relation!Optimization NR!and!PCI!support!per!eNB!cell and!per!carrier LTE1383:!Cell!Specific Neighbor!Relation/PCI!Handling 64!supported X2-links RL50 • • • Rl30 Rl20 Rl10 RL50 RL40 RL40 RL40 Establishing!inter-RAT NRs!when new!UTRAN/GERAN!cells!are!created RL30 LTE510:!Synchronization • of!InterRAT Neighbors Establishing!new!NRs!between!intra-LTE cells!with!different!frequencies RL60 LTE556: ANR!Intra-LTE, • Inter-frequency!-!UE!Based 256!X2!links!supported!for!FSMr3 RL60 LTE1708:!Extend • Maximum!Number!of!X2!Links •128!X2!links!supported!for!FSMr2 Automatic Neighbor Relation (ANR) Architecture of Automatic Neighbor Relation (ANR)
4 Functional Description for ANR
4.1 LTE724: Automatic Neighbor Cell Configuration
4.1.1 Benefits
The operator considers only for the configuration of the eNB's served cells and the IP connectivity to all its neighbor LTE eNBs. For all LTE neighbor cells, the configuration data necessary for establishing the required IP connectivity towards the hosting BTS site is pre-planned offline or can be re-configured during operation. The eNB establishes X2 connections to all neighbor eNBs, up to the supported number of X2 links. With an established X2 link, at both peers the eNBs keep an up-to-date knowledge of the neighbor cell configuration data for S1 and X2 handover.4.1.2 Pre-planning
During offline planning with the NetAct planning tools or the BTS Site Manager, the operator has to plan the IP addresses of all neighbor sites. All further neighbor base station information about the hosted neighbor cell is derived automatically during the corresponding X2 set-up procedures.g
Only one single X2 connection is established between two base stations regardless of the number of supported cells per eNB. This means all cells of an eNB, each assigned with a unique global Cell-ID, have the same X2 IP address because IP addresses are assigned to the BTS nodes.4.1.3 Commissioning and integration phase of a new eNB
If a newly deployed Flexi BTS for LTE has all the commissioning data including the configuration data, it runs the X2 Set up procedure to each configured neighbor eNB. When the connection is established successfully, for example the listed neighbor is already installed and commissioned too, then after establishment of the control plane, all required neighbor information is exchanged between the requesting eNB and all responding ones. The information is stored in the corresponding NCL entries of the involved eNB on both sides. If a listed neighbor does not respond, it is marked as not reachable without any further notification.4.1.4 Neighbor cell update
When one eNB in operational mode receives an X2 Set-up request from another eNB, it responds to the request, sends its own cell configuration data to the requesting eNB, and stores the received configuration information in its own NCL list.
g
Without activation of the LTE492: Automatic Neighbor Relation (ANR) and/orLTE782: ANR-UE based feature, the eNB will discard incoming connection
requests from a neighbor site if there is no IP address configuration available for this particular site. In RL30, if either the LTE492: ANR feature or the
LTE782: ANR-UE based feature is activated at the target eNB, then for the LTE724: LTE Automatic Neighbor Cell Configuration feature X2 configuration it
is sufficient to configure the IP address, as OAM-controlled, at one peer.
If the requesting eNB of the X2 Set-up procedure is already known and the neighbor configuration information is available, the responding Flexi LTE still sends its own cell configuration to the initiating eNB. The received information is compared with the existing information and is updated if modifications are identified.
4.1.5 Configuration data exchange via X2
The common X2 procedures on the control plane are used to derive and update the OAM neighbor cell configuration data.
g
In RL10/20, these cells reported from the connected neighbor eNB become neighbors of the own cells. From RL30 more details are given in the common Object Model behavior description. It is up to the operator to consider the topology and configure the correct neighbors. The LTE539: Central ANR feature runs in the NetAct to find out the most suitable neighbors based on geo-location. Figure 2 Configuration of neighbor cells NetAct BTSSitemanager Data communication network Configuration ofowncells Configuration ofneighborcells X2interface X2interface eNB1 Cell#2 eNB2 Cell#2 eNB2 Cell#3 eNB2 Cell#1 eNB1 Cell#1 eNB1 Cell#3 Automatic Neighbor Relation (ANR) Functional Description for ANR4.1.6 LTE724 Interaction with Common Object Model
With the introduction of the common object model approach, there is a common storage of neighbor cell and relationship information for S1, X2 handover for manual
configuration and/or automatic learning of neighbor cells, either in the auto configuration or later during operation of the eNB. This has impact on the LTE724: LTE Automatic
Neighbor Cell Configuration, LTE539: Central ANR, LTE492: ANR and LTE782: ANR Fully UE based features, and allows concurrent operation of all these features. The
operator can even configure neighbor eNB in a similar way as the LTE492: ANR/LTE782:
ANR - UE based feature would find those during operation of the eNB.
The eNB will not only store the neighbor IP address all the time, but also all the neighbor cell information. This supports X2 as well as S1 handover to these neighbors. In case the X2 link is dropped and X2 hand over is not possible, then automatically S1 handover is applied. The cell's neighbor information will be resolved as soon as the UE reports the neighbor PCI during mobility measurements. After an HO attempt is initiated to this cell, a persistent neighbor relation is established. The management of the neighborships with blacklists on the cell and the eNB levels are supported. More neighbor eNBs and cells are supported to allow even more learning of neighbors. Still the manual configuration of neighbor eNB and cells is possible in parallel to ANR functions.
The LTE724: Automatic Neighbor Cell Configuration feature is a basic feature, together with the activation of the optional features LTE492: ANR or LTE782: ANR - UE based, the incoming X2 links are supported as well. The original LTE724: LTE Automatic
Neighbor Cell Configuration feature behavior is obtained, if the IP address is configured
as oamControlled IP address. Applying the feature requires only configuring at both peers the other neighbor eNB's IP address (neighbor identification).
4.2 LTE539: Central ANR
4.2.1 Functional overview
Feature scope
The LTE539: Central ANR feature requests the NetAct Configurator and Optimizer to generate automatically LTE intra- and inter-frequency neighbor relations for a new eNB of an LTE network during auto-configuration, while the corresponding operational neighbor eNBs are not configured. It is assumed, that those will accept the X2 setup based on the LTE492: ANR or LTE782: ANR Fully UE based feature. The LTE539:
Central ANR is a feature purely of the NetAct Optimizer and Configurator; the BTS will not be impacted by this feature. • The NetAct Optimizer generates adjacency information as required for UE mobility management. • The operator can control with a profile the number of minimum and maximum neighbor cell relation to be prepared for each served cell. The NetAct adapts this information to the eNB level neighbor relations and configures the required eNB identifications at the selected scope of eNBs. New installed eNBs will try to set-up the X2 link to the other peer. • The NetAct Configurator will include neighbor cell relation information in the CM database for eNB auto-configuration. Functional Description for ANR Automatic Neighbor Relation (ANR)
• For the eNB, the neighbor cell relation information is stored in the parameter database. One “Neighbor Relation” is always affecting 2 eNB DB.
4.2.1.1 NetAct Optimizer
To support “Central ANR,” Optimizer creates for each (newly) planned eNB a list of neighboring eNBs based on a priority function composed of distance and antenna directions of the hosted LTE cells. The Optimizer identifies the neighbor relations based on cell-eCGI and identifies the required eNB-global eNB ID to inform the Configurator about the modifications. The lists of neighboring eNBs: • The Optimizer passes lists of neighboring eNBs to the Configurator. • The Optimizer passes one neighbor list for each given eNB of the plan to the Configurator. • The Optimizer and Configurator use the global eNB ID to identify eNBs. The Optimizer ranks the list of cell neighbors according to a priority criterion and enforces the number of neighbor cells to be in an operator-definable range between the lower and the upper limit. The lower limit will only be enforced in case there are enough neighbor cells fulfilling the priority criterion.g
The aim of the LTE539: Central ANR feature is to provide a ranked list of neighbor eNBs to a given eNB. To reserve free entries in the neighbor table for not yet planned neighboring eNBs, it is possible to restrict the number of entries by limiting the number of neighbor cells. The policies, the lower and the upper number of neighbor cells and the priority criterion are existing mechanism for GSM and WCDMA neighbor cell configurations.Manual execution of Central ANR in Optimizer
Manual execution of the LTE539: Central ANR feature allows to determine neighbor eNBs according to an operator selected scope of the eNBs based on geo-locations. Usually the eNB is in operational state and has existing neighbor eNBs. The manual execution of centralized ANR enforces the current policy. This means, that the neighborships for the selected eNBs are adapted to the latest findings of this workflow. As those eNBs run in a new NRT (Neighbor Relation Table) setup, the currently applied neighbor relation settings (for example, black listings and CIO settings) for deleted neighbor eNBs are useless. To avoid race conditions with the current configuration of the eNBs, the operator needs to disable existing decentralized ANR functions (the LTE782:
ANR - UE based and LTE492: Automatic Neighbor Relation (ANR) features) in the scope
of the selected eNBs. According to the described use cases, it is required, that the
LTE782: ANR - UE based and the LTE492: Automatic Neighbor Relation (ANR) features
are disabled during plan provisioning. Of course the operator can enable the two features after the execution of the manually triggered the LTE539: Central ANR feature. The use cases for manual execution of the centralized ANR are:
• Some eNBs have been installed without auto-configuration, no neighbors exist.
• The operator creates eNBs and manually creates plan files to be activated by installation personnel.
• Some eNBs failed during auto-configuration and need to be configured in a post-process.
• The operator runs the network without the LTE492: ANR feature or LTE782: ANR
UE based feature. • Some eNBs have changed HW and cell deployment, and require re-configuration. • Some eNBs have too much useless neighbors and need to obtain a new NRT. The operator can select a scope of planned and/or operational eNBs and execute in NetAct Optimizer the tool for “centralized ANR”. This tool determines for each of the selected eNB a list of neighboring eNBs based on a priority function described below. The selected neighbor eNB might be: • a part of the selected set • other eNBs that are controlled by the same NetAct cluster • external cells, which are controlled by another element manager, even from other vendor During auto-configuration “Centralized ANR” ignores already planned neighbor relations, since it operates on a newly installed eNB. In contrast, if the user manually starts “Centralized ANR”, the algorithm needs to apply a certain replacement strategy to consider existing neighbors, that have been created manually or by ANR. Existing neighbor cells might be whitelisted or blacklisted, neighbor eNB might be blacklisted for handover via X2. Existing neighbors might have been optimized with respect to - for example - time to trigger or cell individual offset. Manual execution of centralized ANR supports distributed sites. The operator can configure the execution of the neighbor finding algorithm with preference settings: • minimum required number of neighbor eNBs (irrespective of distance) • maximum allowed number of neighbor eNBs (64 oamControlled LNADJ) • maximum allowed distance between any cell-pair of source and neighboring eNBs The neighbor finding algorithm ranks for each served cell of the selected eNBs the potential neighbor cells. The algorithm considers all managed cells of the NetAct cluster as well as all external LTE cells. For each found neighbor eNB, the Optimizer creates the respective LNADJ instances to the source eNB as required for each eNB. The NetAct Optimizer creates the configuration plan file for further processing in Configurator. • The Optimizer deletes all not required actual LNADJs and Configurator deletes their LNADJLs. • The Optimizer creates all required LNADJs that are not yet existing and free instances are available. • The Optimizer reconfigures all existing and required LNADJs to oamControlled. • Configurator also deletes all LNRELs related to deleted LNADJLs - no matter if those are blacklisted, have CIO settings different from default (“0”) or their nrControl property is set equal to “manual”. The NetAct Optimizer creates new neighbor eNBs. The configurator provides all further required information for the eNB to execute the LTE724: LTE Automatic Neighbor Cell
Configuration feature functions to connect the X2 link.
g
• During the execution of manually triggered centralized ANR the UE based ANR features need to be disabled to avoid a commissioning alarm and abort of the plan activation.• The eNBs outside the scope of the selected eNBs will never be configured.
• The feature prepares the new LNADJs for the eNB feature
LTE724: LTE Automatic Neighbor Cell Configuration as oamControlled
LNADJs with the IP address. The IP address is not necessarily configured at both peers. Therefore, the operator should temporary enable the
LTE782: ANR UE based or the LTE492: ANR feature afterwards to enable
the acceptance of incoming X2 links at the other peer.
• The workflow does not consider the capability of the eNBs to support ANR, intra- or inter-frequency LTE HO. If the LTE782: ANR UE based or
LTE492: ANR feature is configured at the other peer afterwards, then the
peer will accept incoming X2 links.
• If the target global eNB ID is X2-black-listed, this is ignored for the
LTE539: Centralized ANR feature, as still S1 HO is supported. The LTE539: Centralized ANR feature does not modify any X2-black-listing
setting.
• The LTE539: Centralized ANR feature does not consider the PCI configuration. It is left to the operator whether or not he runs the
LTE468: PCI Management feature to clean-up the PCI configuration
• The manual execution of central ANR does not support former ADIPNO LTE neighbor modeling as supported up to RL20.
• The operator has to run and provision the manually executed the
LTE539: Central ANR feature twice, if there are no sufficient free LNADJ
instances available. The NetAct Optimizer gives a hint to the operator on the need for the second execution.
4.2.1.2 NetAct Configurator
The Configurator in turn finds for each global eNB ID the corresponding IP address, completes the entry in the attribute adjEnbIPAddressMap of the object ADIPNO (RL30: object LNADJ parameter cPlaneIpAddrCtrl) and writes this into a plan. In addition the NetAct Configurator updates the other peer's plan files to have a
symmetrical X2 configuration. At each neighbor eNB, identified by the global eNB ID, the attribute adjEnbIPAddressMap of the object ADIPNO is updated with the IP address and global eNB ID of the new eNB. With introduction of the common object model in RL30, the Configurator creates an LNADJ instance and sets the parameter
cPlaneIpAddr, cPlaneIpAddressCtrl=oamControlled.
After downloading and activating the plan, the affected eNB proceeds as defined by the
LTE724: LTE Automatic Neighbor Cell Configuration feature:
The eNB starts X2 setup to another eNB (or other eNBs) and exchanges data about the cell it hosts.
4.2.1.3 Integration in the auto-configuration workflow
• The operator in front of the Configurator manually creates/imports a plan with newly planned eNBs. The plan contains the global eNB Id, the geo-location and direction of cells and possibly also the location of the sites. The IP addresses of the eNBs are either pre-planned or manually configured by the operator. In addition, the Configurator knows the actual configuration of the already running network. Automatic Neighbor Relation (ANR) Functional Description for ANR
• The auto-configuration workflow triggers the Optimizer.
• The Optimizer retrieves a list of new eNBs in the master plan to be handled. The Optimizer has already access to the actual configuration.
• The Optimizer plans intra-LTE neighbors for the eNBs in the list.
• The Optimizer allocates collision and confusion free compliant PCI values (the
LTE468: PCI Management feature).
• The Optimizer transfers information about PCIs and intra-LTE neighbors to the Configurator.
• The Configurator then uses this neighbor information to complete “pre-planning” for the new eNBs and their impacted neighbor eNBs.
– The Configurator adds the new eNB to ADIPNO.adjEnbIPAddressMap or in RL30 to LNADJ.cPlaneIpAddr&cPlaneIpAddrCtrl of the running
neighboring eNB. This update of the running eNB is necessary because the IP address of the new eNB has not been available before auto configuration of the new eNB.
– The Configurator creates entries in ADIPNO.adjEnbIPAddressMap or in RL30
to LNADJ.cPlaneIpAddr&cPlaneIpAddrCtrl for all the neighboring eNBs
that are already running
• The Configurator downloads and activates the plan to the network. This results in:
– Auto configuration of the new eNB
– Update of the neighbor relation table in the already running eNB
4.3 External LTE Cell Support in NetAct
4.3.1 NetAct SON features support for the external LTE cells
The external LTE cells in the NetAct are cells of another NetAct region or another vendor cells. The NetAct Configurator is able to support external LTE cells already with RL30. With RL30 the external cell and adjacency (X2 or S1) to it can be created manually by CM Editor or via northbound interface, XML, or CSV file input to Configurator.The external cell information is available in the NetAct in a way that SON features, as the
LTE492: ANR, LTE469: PCI Management can use it also for the border management of
the external cells.
For that the location information and antenna information is provided as well for the external cells and used in Configurator and Optimizer.
The used OSS version is OSS5.4 CD2.
4.3.2 Intra-system adjacency border area management
Figure 3 Border area management - info model EXENBF EXEUCE EXENBF EXEUCE LNBTS-234 LNCEL LNBTS-345 LNCEL LNADJ LNADJL LNCEL LNREL MRBTS LNBTS PLMN (SourceeNB) (ExternalLTEeNB) (ExternalLTEcell) (TargeteNB) (NetActregionborder) MCC:111 MNC:10 FurtherPLMNID,m5 MCC:111 MNC:20 MCC:111 MNC:30 FurtherPLMNID,m5 MCC:111 MNC:20 MCC:111 MNC:30 0..64 1..3,max192 0..194 1..3 1..1 MCC:111 MNC:10 LNBTSID:123 (TargeteNB) MCC:111 MNC:10 LNBTS:2344.3.3 External LTE cell support for the LTE492: ANR in NetAct.
The NetAct Optimizers ANR algorithm for the LTE492: Automatic Neighbor Relation(ANR) feature considers the external LTE objects as candidates for neighbor objects. If an external eNB or external cell satisfies the conditions of the ANR algorithm, the Optimizer adds this external cell to the mapping table (PCI, frequency, IP address) of a corresponding eNB. The ANR function in eNB detects new neighbor cells and the eNB creates corresponding LNADJ and LNADJL objects. The NetAct creates suitable external LTE objects for those. The NetAct synchronizes the parameter updates from the LNADJ and LNADJL objects towards the external cell objects. The geo-location data need to be maintained by the operator. The feature LTE492: ANR ignores external objects if those do not have geo-location information assigned. This behavior is different to the own-managed cells, for more information on distributed sites see the LTE1045: Full SON Support for Distributed Sites feature.
4.3.4 External LTE object support for LTE468: PCI Management
in NetAct.
The LTE468: PCI Management feature considers all relevant LTE cells irrespective of the management system they are connected to. Since the cells managed by another
management system also influence the selection of suitable PCI values, the NetAct's algorithms consider external cells when assigning PCI values to “own” cells.
Nevertheless, the NetAct is not able to assign PCI values to external cells.
4.3.5 External LTE cell support for the LTE539: Central ANR in
NetAct.
The NetAct Optimizer considers external eNBs and its sub-ordinate cells as neighbor cell candidates during the centralized ANR configuration (the LTE539: Central ANR feature). Similar as for the own-managed LTE cells the preference settings or the operator selections are applied for external eNBs and its sub-ordinate cells during neighbor cell candidate selection.
4.3.6 External LTE cell support for the LTE581: PRACH
Management in NetAct.
The NetAct Optimizer considers external eNBs and its subordinate cells during the PRACH configuration (see the LTE581: PRACH Management feature description). Similar as for the own-managed LTE cells the preference settings or operator selections are applied for external eNBs and its subordinate cells during neighbor cell candidate selection.
4.4 X2 link management
The eNB supports two types of X2 links: oamControlled X2 links (that is X2 links which are provided and controlled by the operator) and enbControlled X2 links (that is X2 links that the eNB learned via ANR procedures, respectively the ones that are under control of ANR). The type of the X2 link is provided in the associated LNADJ object instance.4.4.1 oamControlled X2 links
The oamControlled X2 links have the following basic properties: • The IP-address to be used for the establishment of the oamControlled X2 link is provided by the operator in the LNADJ object instance. It is the responsibility of the operator to cater for correct configuration of the IP-address of the oamControlled X2 link. • The eNB automatically triggers the establishment of the oamControlled X2 link configured by the operator (for example, if a startup of the eNB occurs). No further conditions are checked by the eNB. • Establishment of the oamControlled X2 link has priority over establishment of the enbControlled X2 link. • If the establishment of the oamControlled X2 link fails, an alarm is raised by the eNB. To avoid inconsistencies regarding establishment/re-establishment behavior, it is recommended to configure the same X2 link type at both sides of the X2 link (that is if the X2 link is configured as oamControlled in eNB, then it should be also configured as oamControlled in the peer eNB).4.4.2 enbControlled X2 links
The enbControlled X2 links have the following basic properties: Functional Description for ANR Automatic Neighbor Relation (ANR)• All X2 links which are automatically established by the ANR functions are labeled as the enbControlled X2 links. Activation of at least one of the ANR features (either the
LTE492: Automatic Neighbor Relation (ANR) or LTE782: ANR Fully UE based) is a
pre-condition for the establishment of the enbControlled X2 link. • The ANR functions of the eNB trigger the automatic establishment of the enbControlled X2 link, if the eNB detects that handover procedures to cells of the neighbor eNB have to be performed. • The IP-address needed for X2 link establishment is automatically determined by the eNB (for IP-address retrieval mechanisms, see LTE492: Automatic Neighbor Relation (ANR) or LTE782: ANR Fully UE based).
• Establishment of the enbControlled X2 link to some neighbor eNB might be forbidden by the operator via X2 link blacklisting.
Regarding re-establishment of enbControlled X2 links, the eNB behaves as described in
Outgoing enbControlled X2 link (establishment triggered by the eNB) and Incoming enbControlled X2 link (establishment triggered by neighbor eNB).
4.4.2.1 Outgoing enbControlled X2 link (establishment triggered by the eNB)
The eNB will trigger (re-)establishment of the enbControlled X2 link if all of the following conditions are met: • The eNB has seen that cells of the neighbor eNB are necessary as targets for handover (in this case LNREL/LNADJL object pairs are available associated with the neighbor eNB). • The operator has not forbidden establishment of the enbControlled X2 link via X2 link blacklisting (see the New parameters table in the LTE782: ANR Fully UE based
feature).
• Either LTE492: Automatic Neighbor Relation (ANR) or LTE782: ANR Fully UE based is activated.
• The maximum number of X2 links, which can be established by the eNB, is not reached yet.
4.4.2.2 Incoming enbControlled X2 link (establishment triggered by
neighbor eNB)
The eNB will accept establishment request of the enbControlled X2 from the neighbor eNB if all of the following conditions are met:
• The operator has not forbidden establishment of the enbControlled X2 link via X2 link blacklisting.
• Either the LTE492: Automatic Neighbor Relation (ANR) or the LTE782: ANR Fully UE
based is activated.
• The maximum number of X2 links which can be established by the eNB is not reached yet.
g
Automatic re-establishment of the enbControlled X2 links might occur only if one of the ANR-features (either theLTE492: Automatic Neighbor Relation (ANR) or LTE782: ANR Fully UE based)
or both of them are activated. If the operator wants to deactivate both ANR features (the LTE492: Automatic Neighbor Relation (ANR) and the
LTE782: ANR Fully UE based) but still wants to be sure that an X2 link is always
re-established (for example after eNB re-start), then the X2 link has to be defined by the operator as oamControlled.
Otherwise, after the eNB reset, the X2 link will be lost. If there is LNADJ oamControlled and LNADJ enbControlled neighboring pair, the
Transport layer connection failure in X2 interface alarm is activated.
g
In case when the LTE492: Automatic Neighbor Relation (ANR) feature is activated, it is in addition required to have for the LNADJ to be re-established a valid PCI/IP@ entry for one of the LNADJLs.g
It is recommended to run whole network or subclusters in common ANR mode (ANR ON or OFF).4.5 LTE1708: Extend Maximum Number of X2 Links
The LTE1708 Extend Maximum Number of X2 Links feature introduces the extension of the number of supported X2 links within the eNB from 64 to 256 X2 links for FSMr3 and from 64 to 128 for FSMr2.
The Table 2: Minimum number of supported neighbor objects shows the minimum number of neighbor objects which are supported:
Table 2 Minimum number of supported neighbor objects
Object MO per FSMr2 FSMr3
neighbor eNB LNADJ source eNB 128 256
neighbor cell LNADJL neighbor eNB 24 24
neighbor cell (total) LNADJL source eNB 768 1536
source cell LNCEL source eNB 12 18
neighbor relationship LNREL source cell 389 389
neighbor relationship (total) LNREL source eNB 480 1728*
* assumption: 48 LNREL per carrier, 2 carriers per cell In case that higher values, as presented in the Table 2: Minimum number of supported neighbor objects are used, the system performance could be decreased. The increase of the number of X2 links are realized in the following way: • The size of the X2 black-list table is increased. Functional Description for ANR Automatic Neighbor Relation (ANR)
• With the setup of 256 (128) X2 links, also the learned neighbor cells are considered. Taking 6 cells per eNB in average into account an overall amount of 256x6 = 1536 (FSMr3) and 128x6 = 768 (FSMr2) neighbor cells can be considered.
4.6 LTE492: Automatic Neighbor Relation (ANR)
Figure 4 LTE492: ANR
4.6.1 Prerequisites
The prerequisites are as follows: • Geo-locations • Antenna direction has to be configured for all LTE cells at the NetAct Configurator non-network parameters. • The external LTE cell can be configured in case of several NetAct clusters support one LTE network. • The operator has to ensure, that the LTE cell black-lists (blacklistHoL) does not contain the PCIs in the PCI/IP address table, that is learned by the LTE492: ANR feature. • The neighboring eNBs have IP connectivity to establish an X2 link.• All the neighbor eNBs have the LTE492: ANR feature or the LTE782: ANR - UE
based feature activated to accept the incoming calls.
4.6.2 Functional overview/details
In LTE networks, the UE mobility relies on information given by neighbor cell relations and neighbor cell configurations. An automatic mechanism is implemented to discover and integrate unknown cells. It supports and allows the automated configuration and update of neighbor cell information without the need of an off-line planning update of the neighbor cell configurations. The neighbor cell configuration via X2 is initiated by the UE-measurements of a connected UE. Only the connected UE reports this measurements during mobility procedure. The UE reports all detected/strongest cells above a given threshold. Therefore, it might report strong cells whose PCI is currently not yet known to the Flexi Multiradio BTS. The eNB checks in the A3/A5 measurement when there are more PCI reported, if the unknown PCI is the only target to be selected. In this case, the Flexi Multiradio BTS looks up the C-plane IP-connectivity information (IP address) of the relevant neighbor eNB, hosting the unknown cell. The eNB uses only the strongest unknown PCI for this and only if there is no other known PCI that could be selected for HO preparation. If the Flexi Multiradio BTS successfully looks up the IP-connectivity information, the X2 signaling connectivity is set up, and an IPsec tunnel that is used for S1 traffic is also used for the X2 traffic as configured, if the network domain security is applied. The X2 UP interface (X2_U) is set up during the first handover event between a pair of eNBs, including IPsec tunnel over S1 interface, if network domain security is applied.g
The parameters limiting learning of new neighbors defined in ANRPRL are applied also to the LTE492: ANR feature.g
The ANR supports IPsec star topology configurations where an IPsec tunnel that is used for S1 traffic is also used for X2 traffic as configured. IPsec meshed topology configurations are not supported. The resolution of PCI to IP-connectivity information is done by means of a PCI/RF/IP address look up table stored at the eNB, provided by O&M-configuration (NetAct Optimizer, NetAct Configurator). The PCI/RF/IP address look-up table provides a mapping of PCI assigned to a neighbor cell. The table includes information about the relation of the cell's PCI identification at a certain RF-carrier to the C-plane IPaddress of the Flexi Multiradio BTS serving that cell. Functional Description for ANR Automatic Neighbor Relation (ANR)g
The PCI values of neighbor cells are configured unique for the given center frequency (RF-carrier) and the geo-location area of the cells. The LTE492: ANR feature supports finding of the neighbor on the same (common) center frequency as the actual cell. It is a general assumption, that all cells are assigned to the same center frequency. Therefore, in the PCI/IP address table all PCI values have usually the same RF-carrier. In special cases, for example PLMN border areas or urban/rural multi vendor borders, the operator might assign cells of one eNB to different center frequencies, then the PCI/IP address table allows configuration of potential neighbors for each center frequency (RF-carrier). The selection inside the NetAct is based on the geo-data and collects in a typical two center frequency network the potential neighbor cells from either center frequency. This allows the operator to assign the cells later on to different center frequencies without update of the eNB PCI/IP address table.g
It is not recommended to use the LTE492: ANR feature in a networkdeployment with three center frequencies and/or with huge difference in the cell sizes on each center frequency, for example for 800 and 2600 MHz bands, as in those cases some RF carriers might have less potential candidates prepared than required. The generation of the PCI/RF/IP address look-up table is part of the Auto-connection/Auto-configuration procedure. With introduction of the common object model in RL30, the feature is adapted to the new modeling. The neighbor relation and the neighbor cell information is persistently stored. This allows S1 handover, if X2 link is for any reason not running. The neighbor cell relation is only generated if the PCI is reported by a UE connected to this cell. The cell-specific relationship allows to see the relevant neighbor cells, while still all known cells at the eNB level are available for handover. The new neighbors found by the LTE492: ANR feature will be created as LNADJ
instance and set the parameter cPlaneIpAddrCtrl=enbControled and all neighbor data from the X2 link among them LNADJL.phyCellId. After each X2 link drop one of the persistent configured LNADJL.phyCellId will be used to look-up the IP address again. This behavior requires to have an up-to-date IP address/PCI look-up table in RL30. The PCI update at the neighbor cell is informed to the neighbors connected via X2, but the PCI/IP address table is not updated. The operator can do this manually triggered. Refer to the LTE468: PCI Management feature and self-healing of PCI violation.
The LTE492: ANR and the LTE782: ANR - UE based features can be activated
concurrently in the eNB. In this case for resolving the IP address, the look-up table has precedence before the MME look-up. In case of X2 link drop the re-connection of the X2 link for enbControled IP address will be resolved via the look-up table first, if no suitable PCI value is found, then the MME procedure is applied. Dependent on PCI or IP address changes, it is possible, that a different eNB is finally selected as neighbor, or before established X2 link cannot be resolved. A work around is to set the IP address to oamControled, if the IP address is still the same, see if the eNB sets up the X2 link correctly, and then change to enbControled again. This can help updating the PCI values in LNADJL so that there is a valid resolution next time. Automatic Neighbor Relation (ANR) Functional Description for ANR