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Nokia Siemens Networks Self Organizing Network (SON) Features Technical White Paper

Nokia Siemens Networks

Copyright 2007 Nokia Siemens Networks. All rights reserved.

CONFIDENTIAL Page 2 of 63

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Copyright Nokia Siemens Networks 2009. All rights reserved.




Table of Contents

1 Introduction............................................................................................7

2 SON Overview.......................................................................................7 2.1 SON Scope ..........................................................................................................................7 2.2 SON Architecture .................................................................................................................9 3.1.1 Hybrid SON ..........................................................................................................................9 3.1.2 SON enabling interfaces and SON enabled products ........................................................11 3.1.3 SON Coordinator in NetAct ................................................................................................12

3 LTE SON Features ..............................................................................14

3. LTE Self Configuration ........................................................................15 3.1 Auto connection of Flexi Multiradio BTS ............................................................................15 3.2 Auto configuration of Flexi Multiradio BTS .........................................................................17 3.3 Network Integration ............................................................................................................19 3.4 Parameters self-configured ................................................................................................20 3.5 Operator Input ....................................................................................................................21 3.6 Operator policies ................................................................................................................22 3.7 Basic Hardware Installation of Flexi Multiradio BTS...........................................................22

4. ANR Automatic Neighbor Relation function.........................................26 4.1 LTE Neighbor cell configuration with preplanned IP addresses.........................................26 4.2 3GPP Automated Neighbor Relation (ANR) support for LTE............................................27 4.3 Automated Neighbor relation establishment for IRAT ........................................................33 4.4 ANR and Changes in the network ......................................................................................34 4.5 Multivendor support............................................................................................................35 4.6 Handling of X2 continuity....................................................................................................35

5. Self Optimization .................................................................................37 5.1 Autonomous network optimization at network launch ........................................................37 5.2 Self Optimization setup - Operator policies ........................................................................37 5.3 Self Optimization: Data sources used ................................................................................38 5.4 Localized SON features .....................................................................................................39 5.4.1 Efficient usage of PDCCH resources via Link adaptation ..................................................40 5.4.2 Optimization of handover parameters ................................................................................40 5.4.3 CQI adaptation (DL) ...........................................................................................................40 5.4.4 Link adaptation by AMC (UL/DL)........................................................................................41 5.4.5 Closed loop UL power control ............................................................................................42 5.4.6 Downlink adaptive open loop MIMO for two antennas .......................................................43 5.4.7 Support of group hopping for the uplink reference signal...................................................43 5.4.8 Fair scheduler (UL/DL) .......................................................................................................44 5.4.9 Advanced target cell selection and handover retry for intra frequency handover...............45 5.4.10 S1 Flex load balancing ....................................................................................................45 5.5 Centralized SON ................................................................................................................46




5.5.1 Overview ............................................................................................................................46 5.5.2 Physical Cell ID Management ............................................................................................48 5.5.3 Auto configuration support .................................................................................................49 5.5.4 RACH Optimization ............................................................................................................50 5.5.5 ANR Optimization...............................................................................................................51 5.5.6 QoS related parameter Optimization..................................................................................52 5.6 Coverage and Capacity Optimization.................................................................................53 5.7 Energy Savings ..................................................................................................................54 5.8 Interference Reduction .......................................................................................................55 5.9 Mobility Robustness Optimization ......................................................................................55 5.10 Mobility Load Balancing Optimization ................................................................................55

6. Self healing..........................................................................................57 6.1 Self healing in Flexi Multiradio BTS....................................................................................57 6.2 Cell Outage ........................................................................................................................58 6.2.1 Cell Outage Detection ........................................................................................................58 6.2.2 Cell Outage Compensation ................................................................................................58 6.3 Compensation for Outage of Higher Level Network Elements...........................................59 6.4 Automated Fault Correction ...............................................................................................59 6.5 Real-time network monitoring.............................................................................................60 6.6 Reducing the alarm flow.....................................................................................................60 6.7 Automated actions..............................................................................................................61 6.8 Alarm correlation ................................................................................................................61

7. Conclusion...........................................................................................63




Table of Figures

Figure 1 : LTE SON functionalities................................................................................................8

Figure 2 : SON Advantages ..........................................................................................................8

Figure 3 : SON benefits splitted in different use cases .................................................................9

Figure 4 : Nokia Siemens Networks Hybrid SON Architecture ...................................................10

Figure 5 : Hybrid SON solution decision criterias.......................................................................11

Figure 6 : SON enabling interfaces.............................................................................................12

Figure 7 : SON enabled NSN products.......................................................................................12

Figure 8 : Network operation w/o SON .......................................................................................13

Figure 9 : Network operation with SON ......................................................................................13

Figure 10 : Auto connection sequence .......................................................................................17

Figure 11 : Auto configuration sequence ....................................................................................19

Figure 12 : Network integration sequence ..................................................................................20

Figure 13 : Automated Network Planning ...................................................................................21

Figure 14 : Flexi Multiradio BTS..................................................................................................24

Figure 15 : Physical Cell ID and Global Cell ID ..........................................................................28

Figure 16 : Neighbor cell discovery.............................................................................................29

Figure 17 : IP address resolver flow ...........................................................................................30

Figure 18 : X2 set-up and configuration exchange .....................................................................31

Figure 19 : Neighbor cell and site relations.................................................................................32

Figure 20 : Neighbor site & cell list and Neighbor relation table .................................................32

Figure 21 : Automated Neighbor Relation Establishment support for UTRAN............................33

Figure 22 : Cell mapping from UTRAN to LTE............................................................................34

Figure 23 : Local versus centralized optimization .......................................................................38




Figure 24 : NetAct Optimizer multi vendor support .....................................................................39

Figure 25 : Link adaptation .........................................................................................................40

Figure 26 : CQI adaptation..........................................................................................................41

Figure 27 : Link adaptation by AMC............................................................................................42

Figure 28 : Closed loop power control ........................................................................................42

Figure 29 : Adaptive open loop MIMO .......................................................................................43

Figure 30 : Group hopping for UL reference signal....................................................................44

Figure 31 : Fair scheduler ..........................................................................................................44

Figure 32 : Advanced target Cell selection ................................................................................45

Figure 33 : S1 load balancing ....................................................................................................46

Figure 34 : NetAct Optimizer .....................................................................................................47

Figure 35 : PID assignment .......................................................................................................49

Figure 36 : Optimizer Auto configuration support .......................................................................50

Figure 37 : Optimizer ANR optimization......................................................................................52




1 Introduction Nokia Siemens Networks recognizes the challenge of the mobile radio networks and complex operational tasks in order to build and maintain highly reliable and high performance networks. Historical development and evolution of mobile radio introduced network architectures where multiple radio technologies overlaid each other with multiple vendors supplying equipment for these technologies. This introduced high complexity to many operational tasks and increased the operational expenses of many operators. With the introduction of Long Term Evolution (LTE) technology, operators have the opportunity to optimize their network management operations and reduce their operational expenses.

Nokia Siemens Networks recognizes this and offers a rich series of LTE Self Organizing Network (SON) features that allow network operators to manage their networks easily and reduce their OPEX. The LTE SON features provide intelligent solutions from the initial network setup to the daily operation of the network.

Nokia Siemens Networks eNBs (Flexi Multiradio BTS) provide plug and play features that allow the eNB to automatically integrate itself to the existing network with minimal or no manual intervention.

Besides the eNB based SON features, Nokia Siemens Networks NetAct EMS platform offers SON features to optimize the entire network based on the current traffic trends and the network operators policies. The SON features are fully integrated into the EMS platform and its applications. The NetAct applications are enhanced with LTE features with the evolution from the 2G and 3G technologies. This allows easy introduction of the LTE technology into the existing networks by overlaying 2G and 3G technologies.

The NetAct applications also include multi vendor extensions that extend the SON capabilities satisfying the network operators needs for the management of their network comprised of multiple vendors equipment.

2 SON Overview 2.1 SON Scope

The main SON functionalities consist of:

Self-configuration: automated network integration of new eNB by auto connection and auto configuration, core connectivity (S1) and automated neighbor site configuration (X2)

Self-optimization: auto-tune the network with the help of UE and eNB measurements on local eNB level and/or network management level




Self-healing: automatic detection and localization and removal of failures

Self-planning: dynamic re-computation of network plan, e.g. due to capacity extensions, traffic monitoring or optimization results

Healing

Optimisation

Configuration

Self-

Plan

ning

Healing

Optimisation

Configuration

Self-

Healing

Optimisation

Configuration

Self-Self-

Plan

ning

Figure 1 : LTE SON functionalities

Following benefits are seen with SON:

Healing

Optimisation

Configuration

Self-Self- Reduce cost Simplifies installation

procedure Reduces planning effort

Parameter optimization based on network monitoring and measurement data from terminals

Minimize operational effort Increase quality and performance

System detects problems itself and mitigates/ solves these

Avoid user impact Significantly reduce

maintenance costs

Plug and play behavior of new installed network

Figure 2 : SON Advantages




Self planning is often going along with self optimization, esp. in respect of efficient way of network growth support.

The above listed SON advantages result in following SON benefits grouped in use cases:

ImpexField

Installation

ImpexPlanning

Capacity based

optimizationCoverage

based optimization

Quality based optimization

Opex ReductionNOC

Opex Reduction Field Maintenance

Bene

fit fo

r Ope

rato

r

Low

High

Time to MarketImmediate atLTE Rollout

Later

Opex Power Savings

Figure 3 : SON benefits splitted in different use cases

2.2 SON Architecture 3.1.1 Hybrid SON

The Nokia Siemens Networks SON solution is based on harmonized cooperation of the eNBs and EMS platform.

It does not require separate platforms to do SON functions. Nokia Siemens Networks goes for Hybrid SON, parts of the self-organizing functions and algorithms are executed on NetAct/OAM level while others are done autonomously in eNB.

NetAct northbound Interface for interworking with proprietary OSS systems and 3GPP defined northbound interworking objects and processes provide the needed flexibility and evolution safety to support all the already specified and forthcoming SON configuration & optimization cases.




The SON related network architecture includes with launch timeframe all components and interfaces which are needed also by later releases.

Figure 4 : Nokia Siemens Networks Hybrid SON Architecture

The choice of where functions are going to be solved either autonomously on eNB localized level or distributed between eNB / NetAct or centralized on Net act level, depends on each single SON use case.

Please find here some overview for selection criteria:

- Quick short term and simple/localized optimization schemes in eNB - Complex, mid & long term optimization schemes in OAM (e.g. Optimizer) - Multivendor support via X2 and S1 Interface for realization of 3GPP

standardized SON use cases




Hybrid SON: Guideline for SON Use Cases

faster timescale of operation

number of cells involved

Centralized

> 2 cells involved Slower update rate Long term statistics

coverage andcapacity optimization

Distributed

~ 2 cells involved > 2 cells if changed

parameters have only local impact(only neighbor inforequired)for > 2 cells master/slave relations required toallow convergence

utilize X2 signaling

HO & InterferenceOptimization

Localized

single cell scope fast update rate short term statistics

RACH optimization

Crit

eria

Exam

ples

faster timescale of operation

number of cells involved

Centralized

> 2 cells involved Slower update rate Long term statistics

coverage andcapacity optimization

Distributed

~ 2 cells involved > 2 cells if changed

parameters have only local impact(only neighbor inforequired)for > 2 cells master/slave relations required toallow convergence

utilize X2 signaling

HO & InterferenceOptimization

Localized

single cell scope fast update rate short term statistics

RACH optimization

Crit

eria

Exam

ples

Figure 5 : Hybrid SON solution decision criterias

3.1.2 SON enabling interfaces and SON enabled products Following interfaces are enabling the NSN SON functionalities:

Element & Network Management

MME

SAE-GW

eNB

eNB

Public Key InfrastructureNokia Siemens NetworksIdentity Management System

DHCP

Public Key InfrastructureNokia Siemens NetworksIdentity Management System

DHCP

NetAct

traditional OAM Itf

S1 Interfacec/u plane

X2 Interfacec/u plane S1

X2

X2

uU

& OAM

& OAM

& OAM

& OAM

& OAM

& OAM

& OAM

& OAM




Figure 6 : SON enabling interfaces

SON is defined by Operation and Maintenance and Radio Resource Management and Telecom functions.

These are the Nokia Siemens Networks SON enabled products:

SAE-GW

Flexi Multimode BTS

Entry level configuration:Rack mounted servers

Medium & large configuration:

Blade servers

NetAct OSS5.2 CD 2NetAct Unify ( E/2011)

Flexi Network GatewayFlexi-NG

Flexi Network ServerFlexi NS

MME & eNB EMS/NMS

Certification AuthorityNokia Siemens Networks entity

Management System forPublic Key Infrastructure

SON

SON

SON

SON

SON

SON

Figure 7 : SON enabled NSN products

3.1.3 SON Coordinator in NetAct In current network operation NetAct is used to do the operational tasks, which are seen as single applications more or less working separately. There are single interactions per kind of functionality.




Rep

orte

r Th

resh

olde

r& P

rofil

er

Mon

itor

Opt

imiz

er

Con

figur

ator

External RadioNetwork Planning

CM

NetAct

Serv

ices

(Too

ls)

LTE RA Access & Core Network

SW M

anag

erLi

cens

e M

ange

r

PM FMCM

Figure 8 : Network operation w/o SON

With the central SON coordinator in NetAct the existing processes are co-coordinated with minimized operator intervention. The usage of BPEL (Business Process Executive Language) does allow a smooth interworking of the different applications, so no need for any operator intervention.

With the policy machine in the SON coordinator SON feature behavior can be adjusted to operator needs.

Rep

orte

r Th

resh

olde

r& P

rofil

er

Mon

itor

Opt

imiz

er

Con

figur

ator


NetAct

Serv

ices

(Too

ls)

Workflow:eNB Auto

Configurator

Workflow:Cell Outage

Compensation

Workflow:Alarm triggered

actions

Workflow:eNB Auto

Configurator

Workflow:Cell Outage

Compensation

Workflow:Alarm triggered

actions

LTE RA Access & Core Network

SW M

anag

erLi

cens

e M

ange

r

PM FMCM

Policy machine (SON Coordinator)

Workflow Engine(Business Process Execution Language)

Policy machine (SON Coordinator)

Workflow Engine(Business Process Execution Language)

Figure 9 : Network operation with SON




3 LTE SON Features Nokia Siemens Networks SON solution does cover

Self Configuration with

Auto connection of Flexi Multiradio BTS Auto configuration of Flexi Multiradio BTS

ANR Automatic Neighbor Relation function with

LTE Neighbor cell configuration with preplanned IP addresses 3GPP Automated Neighbor Relation (ANR) support for LTE Automated Neighbor Relation Establishment for UTRAN

Self Optimization with

Localized SON in Flexi Multiradio BTS Centralized SON, as Physical Cell ID Management, ANR Optimization,

Self healing with

Self healing in Flexi Multiradio BTS Compensation for Outage of Higher Level Network Elements Automated Fault Correction

Please find in the following chapters each of these areas described in detail.




3. LTE Self Configuration Nokia Siemens Networks provides a solution for a real plug and play eNB roll out which doesnt need any individual eNB specific configuration at site executed by the field installer. All the needed steps are provided like,

- auto connection to the network with PKI based node authentication - auto configuration of SW and configuration data - automated deployment of licenses - automated integration into the network

3.1 Auto connection of Flexi Multiradio BTS The Flexi Multiradio BTS is delivered from the factory with an initial basic SW to allow the basic boot process and the transmission software enabling the establishment of a connection to the IP backhaul and to derive the PKI operator certificates. Network Server Preparation

Before the roll out could be started some Network servers need to be up deployed and configured properly.

DHCP server preparation: Since the auto connection trust on the usage of standard DHCP services, the DHCP servers are preconfigured with suitable options and Nokia Siemens Networks Flexi Multiradio BTS specific data (vendor specific attributes) like IP address of the Identity Management System (IDM), IP address of the VPN/Security Gateway protecting the responsible NetAct OAM system etc.

Identity Management System (IDMS) server : The IDM's certificate server respectively the data base directory are preconfigured with the Nokia Siemens Networks device serial numbers of the ordered Flexi System Modules, the Nokia Siemens Networks signing Factory CA root certificate and proposal other operator trust certificates (trust anchors) that shall be installed to the BTS.

Establishment of IP connectivity

The Flexi Multiradio BTS transport module is automatically configured to enable the Flexi Multiradio BTS to communicate with the network backhaul. It performs automatically L1/L2 auto negotiation and IP address assignment. A DHCP server assigns a public IP address, net mask and default gateway IP@ to the Flexi Multiradio BTS and delivers in addition further information as vendor specific attributes like the vendors the IP address of the Identity Management System (IDM) respectively a 3rd party PKI Certificate Server an other server addresses.

Retrieval of Operator Certificate and trust anchors




After receiving IP address information, the Flexi Multiradio BTS starts the automatic acquisition of the operator Flexi Multiradio BTS node certificate and trust anchors by contacting the operators IDMS / PKI certificate server.

Secure connection establishment

As soon as the final certificates are available in the Flexi Multiradio BTS, it starts the secure O&M plane connection to the NetAct framework in a twofold manner:

- First an IPSec tunnel is established between Flexi Multiradio BTS and the VPN Gateway at the domain border of the operator or in front of the Network Management operating center.

- Second by a TLS connection between the Flexi Multiradio BTS OAM application and the Operation and Mediation System Application integrated into NetAct. This second security layer provides E2E security between applications. So there is no open vulnerability to intercept e.g. user identification or passwords of operating personnel even within the local LAN.

Flexi Multiradio Registration

When the TLS connection is established the Registration is sent to NetAct to trigger the Auto Configuration sequence or manual remote commissioning. For executing proper automated configuration the provision of the geographical site location is essential because the NetAct SON Coordinator respectively Configurator needs to assign the BTS individual configuration data. The Flexi Multiradio BTS supports the automated identification with the help of a fixed mounted GPS receiver available on site.




Figure 10 : Auto connection sequence

As soon as Registration is finished the NetAct SON Coordinator initiates the auto configuration sequence.

3.2 Auto configuration of Flexi Multiradio BTS The NetAct SON Coordinator triggered auto-configuration can be run fully autonomously or certain stop points can be defined for manual intervention.

Software Update

The Flexi Multiradio receives the pre-configured SW configuration list from NetAct and connects to the SW Repository Server to download all required SW build files.

Configuration plan file download

The geographical map coordinates of a newly registering site are used to derive the proper configuration plan file. The plan file is downloaded and includes all needed site, radio and transport configurations.

Software and configuration activation




If the SW and configuration data verifications are successfully done the Flexi Multiradio BTS activates the downloaded SW and configuration data. This will cause re-starts of the Flexi Multiradio BTS. After the re-start the secure IPSec and TLS connections towards NetAct are established again.

Tests

After the new start-up the Flexi Multiradio BTS continues with BTS tests (antenna line communication tests, Ethernet tests, EAC tests).

License preparation

After re-connection to NetAct the Flexi Multiradio BTS looks into the enabled features and requests the needed license files automatically from NetAct. If the files are not available at that time respectively not received during auto configuration process then the license free period is applied and the license files are requested to be prepared.

HW Inventory

The HW inventory identifies the available components and initiates the upload of the inventory to NetAct.

SW Inventory

NetAct uploads of the activated SW build with migrated patches and available configuration data for back-up reasons.




Figure 11 : Auto configuration sequence

With inventory upload the automated commissioning is finished and the Flexi Multiradio BTS is ready for Network integration.

3.3 Network Integration When the Flexi Multiradio BTS was successfully configured the network integration starts either automatically or by a dedicated operator command. During the integration phase all preconfigured X2 interface and S1 interface relations are established, i.e. IPSec associations are done and SCTP peers are connected.




Figure 12 : Network integration sequence

3.4 Parameters self-configured From Flexi Multiradio BTS perspective around 400 parameters in first release are used in operation. They can be classified into

- Radio network parameters - Transport network parameters - BTS Site specific parameters

Amount of parameters: ~ 400 parameters are managed in RL09 ~ 260 parameters do have default values assigned ~ 100 parameters need to be defined for initial deployment from which ~10 - 20 need to be provided from operator as BTS individual parameter settings rest can be set, if required

The planning tool needs to deliver very few parameter, all other parameter are autonomously derived by the system like physical cell identifier, pilot specific settings, neighbors and other cell specific parameter by tight interworking of Configurator & Optimizer.




SONCoordinator

Optimizer

NetActCMCM


Templates

Configurator

eNB Config

~ 10 parameters

~ 400 parameters

Polices

Figure 13 : Automated Network Planning

The initial configurations are self-configured in terms of a set of pre-defined templates which are made available to NetAct Configurator. It is possible to have several templates and Configurator decides on a given criteria like BTS HW configuration which template to choose.

Also the parameters of features come along with default values in the software, where applicable. The Radio Network parameters are the majority were most of them are of static behavior and needs only minor additional manual configuration. The same is valid for the transport parameters. They are either fixed by the templates or self-configuring like the IP address assignment via DHCP. BTS site specific parameter like Antenna configuration, cell size; BTS-ID/names etc. are either derived from an OSS planning tools and imported to NetAct Configurator or mapped to a limited number of templates reflecting the basic configurations or are automatically generated in NetAct Optimizer as Physical Cell ID.

3.5 Operator Input With the support of SON only few operator inputs are required as explained in the chapter before.

But especially from site planning perspective generally the same parameters as today needs to be available for network setup. These parameters will be made available either via an OSS network planning tool, pre-configured NetAct Configurator templates or manual input.




These are for instance Cell range, eNB Global ID, BTS-ID, BTS-logical-ID. Also all the IP configuration of node servers like Certificate Management servers, LDAP servers, VPN-Gateways, MME/SAE-GW IP addresses and port numbers are needed from the operator.

3.6 Operator policies Self-Configuration may happen on different levels, e.g. autonomously by the Flexi Multiradio BTS itself or via the NetAct/NMS loop. If possible and suitable Nokia Siemens implements control capabilities for the operator like to enable/disable self-configuration functions or to over-rule a self-configured value with a own defined one. For example initial the IP address given by the DHCP server can be substituted by another pre-planned IP address.

Optionally also stop points can be used by the operator to have decision points. Parameter values proposed by NetAct Optimizer can be checked before they are put into configuration data and activation is done, if required.

3.7 Basic Hardware Installation of Flexi Multiradio BTS During the initial phase of life the total costs of a network are governed by efforts for planning and deployment. From LTE perspective already in this phase major OPEX savings will be getting possible due to the introduced SON features and the Flexi Multiradio BTS concept.

Therefore Nokia Siemens Networks has dedicated special effort to these points. Together with the unique form factor of the Flexi Multiradio BTS, Nokia Siemens Networks auto-connection and auto-configuration functionality enables a true Plug and Play installation of the eNB. The operators benefits include reduction of effort for planning and handling of configuration data, easier logistics during roll-out, and finally commercial operation of eNB directly after first site visit without need for scheduled network synchronization events.

The HW installation shall include all tasks for the installation of a new Node like support of mounting, connecting with physical connections and first configuration.

A single form factor is used for all components.

Flexi Multiradio BTS reduces BTS installation costs, since no cabinet is needed for a LTE site. Flexi Multiradio BTS reduces the weight of the BTS site dramatically. A Flexi Multiradio BTS module can be lifted, carried, and put into place by one single person.




Due to its small weight, small size, modular design and full frontal accessibility, the Flexi Multiradio BTS is easy to install practically anywhere with minimized site installation time The average modular BTS installation time is reduced to one third of the installation time for a traditional cabinet BTS.

Due to the highly unified and modular architecture HW extensions and replacements can be done with no/minimized downtime:

RF Module: Any RF Module or extension System Module is swappable with System Module in operation

Any RF Module can be removed or installed without affecting cabling of other RF Modules

Adding/changing of RF Module will not affect ongoing calls handled by other modules

System Module Can be easily replaced by pulling out the core of the unit from the casing

Transmission Sub-Module: Easy to change on site by pulling out the System Module core mechanics from the front.

The Flexi Multiradio automatically detects new added or substituted HW and request respectively updates missing SW parts from the NetAct SW Manager autonomously.




System Module (LTE mode)3-sector RF Moduleoptional AC/DC Battery Module

optionalTMA/MHA

Figure 14 : Flexi Multiradio BTS

The Flexi Multiradio BTS can be installed on the wall but it fits into the corresponding legacy GSM/EDGE or CDMA or WCDMA BTS footprints as well. The operator does not need to alter previous plans for expansion that are based on the area. Installation locations for the Flexi Multiradio BTS can be smaller or the same as those reserved for existing legacy GSM/EDGE or CDMA or WCDMA BTS.

The modules fit also into 19 racks. The transport module with integrated firewall and Layer 2 router is an integral part of the Flexi System module, so no external equipment needed to be connected.

The Flexi BTS multipurpose outdoor cabinets and indoor cabinets are further options for sites where cabinet is needed.

Detection and configuration active site equipment like active TMA happens automatically.

The BTS Site Mangers offers an easy to use GUI to cope with exceptional cases of missing auto-connectivity information.

The capacity of pre-installed HW is simply activated or modified by setting new capacity values of the according feature activation entries within the configuration file with the help of the NetAct Configurator. The Flexi Multiradio BTS automatically request and download required licenses from the NetAct License Management application, so there is no operator activity at all required on license handling. There is no need for manual license management at all as long as there is a sufficient




amount of ordered licenses in the pool. During start-up each BTS takes care to get the licenses automatically according to the installed HW and activated features.




4. ANR Automatic Neighbor Relation function In LTE networks the UE mobility relies on information given by neighbor cell relations and neighbor cell configurations. To support and allow as well a flexible pre-planning, and an automated configuration and update of neighbor cell information several mechanisms are implemented.

Nokia Siemens Networks supports 3 features for ANR realization

- LTE Neighbor cell configuration with preplanned IP addresses - 3GPP Automated Neighbor Relation (ANR) support for LTE - Automated Neighbor Relation Establishment for IRAT

4.1 LTE Neighbor cell configuration with preplanned IP addresses This feature is meant to ease the work in early technology trials for establishing the neighbor cell relations. It doesnt need any UE support and supports networks with Nokia Siemens Networks Flexi Multiradio BTS.

For all neighbors cells only the Networks Flexi Multiradio BTS ID and the IP address of the neighbor LTE eNB hosting the excepted adjacent cells need to be configured by off-line pre-planning. During start-up of the Flexi Multiradio BTS the X2 connections are established to all planned neighbor base stations. All the further needed cell configuration information is exchanged between the requesting Flexi Multiradio BTS and all responding neighbor eNB.

During off-line planning with the NetAct planning tools or the BTS Site Manager the operator has to plan the IP addresses of all adjacent neighbor sites. All further adjacent base station information about the hosted adjacent cell information is derived automatically during the according X2 set-up procedures.

Note: Only one single X2 connection is established between two base stations regardless of the number of supported cells per Flexi Multiradio BTS. This means all cell, each of them assigned with a unique global Cell-ID, of a Flexi Multiradio BTS have the same X2 IP address because IP addresses are assigned to BTS nodes ( US = cell) at not to cells (US = sectors).

If a new deployed Flexi LTE has got all the commissioning data including the configuration data it runs the X2-Set up procedure to each configured neighbor Flexi Multiradio BTS. When the connection could be established successfully, e.g. the listed neighbor is already installed and commissioned too, then subsequent with the establishment of the control plane all required neighbor information is exchanged between the requesting Flexi Multiradio BTS and all responding ones and stored vice versa in the according neighbor cell list entries of the involved Flexi Multiradio




BTS on both sides. If a listed neighbor does not respond it is marked as not reachable without any further notification.

When a Flexi Multiradio BTS in operational mode receives an X2 Set-up request of a Flexi Multiradio BTS then it responds to the request, sends its own cell configuration data to the requesting Flexi Multiradio BTS, stores the received configuration information in its own NCL list and marks it as reachable.

If the requesting Flexi Multiradio BTS of the X2 Set-up procedure is already known and neighbor configuration information is available then the responding Flexi LTE still sends it own cell configuration to the initiation Flexi Multiradio BTS. The received information is compared with the existing ones and updated in case of identified modifications. The common X2 procedures on control plane are used to derive and update the OAM neighbor cell configuration data.

4.2 3GPP Automated Neighbor Relation (ANR) support for LTE This feature is 3GPP compliant and supports multi vendor radio networks trusting on UEs capability to identify neighbor cells with appropriate measurements.

The 3GPP variant of automated detection and configuration of unknown LTE cells respectively sites supports the self configuration of the neighbor cell information without operator involvement and planning efforts and requires proper measurement support from UEs. The relations between neighbor cells need to be known respectively carefully planned. Wrong configurations cause HO failures and call drops. The self configuration of relations avoids manual planning & maintenance and subsequent planning mistakes.

ANR spans over 4 steps:

o The radio part with neighbor cell discovery o The core part for the neighbor Sites X2 transport configuration discovery o The X2 Connection Set-up with neighbor cell configuration update o The ANR Optimization

1st Step: The radio part with neighbor cell discovery

A LTE cell identifies itself on the radio interface in two ways:

- First with the so called physical Cell ID (phy_ID) which is part of the Reference Symbol sent out every 1 ms. This ID as a limited range of 504 distinct values and is




therefore not unique. As the phy_ID is the primary anchor point for a UE camping in a cell the value must be unique in the coverage area of the cell itself and all neighbor cells which could be received by an UE. The radio network planning has to guarantee the proper re-use of the same phy_ID without any conflicts.

- Second with the Global Cell ID (GID) broadcasted as part of the System Information Block #1. It has a longer repetition cycle of 80 ms, repeated every 20 ms, but is unique in the whole network and allows an unambiguous identification of a cell.

Figure 15 : Physical Cell ID and Global Cell ID

When a UE change from idle state into connected state it receives the measurement configuration and the order to UE reports all detected/strongest cells above a given threshold. Therefore it may report strong cells which physical IDs are currently not yet known to the Flexi Multiradio BTS. In this case the Flexi Multiradio BTS sends a measurement request to the UE to discover and report the Cell Global ID (GID) for the previously reported unknown physical cell ID. Note: The request is not sent if the phy_ID is blacklisted in the radio resource control blacklist.




Figure 16 : Neighbor cell discovery

If the UE is able to deliver the GID then as the next step the derived GID is to derive the IP connectivity information needed to address the neighbor BTS parenting the new found cell.

2nd Step: The core part for the neighbor Sites X2 transport configuration discovery

The derived Global Cell ID cannot be used to directly address neighbor sites on IP Transport level because it is not structured to be a full qualified domain name. Therefore the GID needs to be resolved to the transport network layer (TNL) configuration which is needed to establish the IP/IPSec connection with SCTP on top of it towards the new found neighbor site.

3GPP RAN 3 defined to use the Information Transfer procedure (TS 43.413) to exchange the TNL configuration respectively IP addresses between 2 neighbor sites with the help of the MME. With the combination of ENB CONFIGURATION TRANSFER and MME CONFIGURATION TRANSFER procedures the two neighbors exchange their transport network layer configuration were the MME acts as relay for the container (transparent for the MME). As each eNB connected to an MME has registered to the MME before with the S1 set-up procedure the MME is able to find the right SCTP route to a neighbor eNB.




Figure 17 : IP address resolver flow

3rd Step: The X2 Connection Set-up with neighbor cell configuration updates

When the transport network layer (TNL) configuration is received then and there is no X2 interface already established to this neighbor site then the X2 connectivity is set-up and the Flexi Multiradio BTS exchanges the list of served cells with the new neighbor as defined by 3GPP TS 36.423. The exchanged cell information covers all served cells of a site and is stored in the configuration.




Figure 18 : X2 set-up and configuration exchange

4th step: The ANR Optimization

There are 2 kinds of neighbor relations to distinguish:

o One between neighbor sites o And one between neighbor cells

A neighbor site relation is given when a direct X2 connection exists between 2 sites respectively a communication link via S1 / MME is known. A neighbor cell relation is given when 2 cells have a common/overlapping coverage area. So a UE reposts always a neighbor cell relation and never a neighbor site relation and only proper configured neighbor cell relations are relevant for handover performance figures. Referring to the example given by the figure below:

o eNB-A has a X2 connection to eNB-B -> neighbor site relation o eNB-B parents 3 Cells with GIDs B11, B12 and B13 o but only to the cell with GID B10 a neighbor cell relation exists




Figure 19 : Neighbor cell and site relations

When a new neighbor site relation is established the configuration information of all parented cells are stored in the neighbor site & cell list (NCL). But only the identified respectively measured neighbor cell is listed as relation in the neighbor relation table (NRT) between an own cell and a neighboring cell of this site of this neighbor. Note: NCL and NRT are logical objects and will not refer to a particular implementation.

During daily operation it may turn out that a cell relation doesnt work properly for handovers, i.e. HO performance counters show higher failure rates then average. In this case a relation can be blacklisted by optimization algorithms. With NetAct Optimizer Nokia Siemens Networks offers a centralized SON ANR optimization solution.

Figure 20 : Neighbor site & cell list and Neighbor relation table




4.3 Automated Neighbor relation establishment for IRAT

This feature supports legal UTRAN/GSM networks and utilizes the capabilities of NetActs SON Coordinator and Configurator to create the neighbor information out of existing UTRAN site plan information.

The automated planning of neighbor relation to UTRAN/GSM cells is done on NMS level with the help of NetAct Configurator and Optimizer. NetAct imports the UTRAN/GSM network configuration respectively plan data and maps it with the LTE topology. The assumption is done, that LTE will be designed as an overlay network and that existing sites will be re-used for LTE. Therefore it is also assumed that the existing UTRAN/GSM neighbor ship information can be re-used as an initial setup for neighbor relations as well from LTE cells.

To allow an automatic mapping the operator needs to define few anchor points for cell mapping.

Figure 21 : Automated Neighbor Relation Establishment support for UTRAN / GERAN/ HRPD




LTE

UTRAN

Cell 4

Cell 2Cell 3

Cell 1

Cell XLTE

UTRAN

Cell 4

Cell 2Cell 3

Cell 1

Cell X

Figure 22 : Cell mapping from UTRAN to LTE

The mechanism shown in the figures for UTRAN are the same way applicable for GSM or HRPD

4.4 ANR and Changes in the network Removal / addition of cells belonging to a removed / new site:

Changes in the network need to be considered by the automated features for neighbor relations. Here the different behavior of the features is listed:

LTE Neighbor cell configuration with preplanned IP addresses: The relations to existing sites respectively their cells are automatically updated with the deployment of the new site with pre-planned expected neighbors. Removal is possible with an updated configuration file deployed to all sites.

3GPP Automated Neighbor Relation (ANR) support for LTE: The UE discover and measure a new identified cell, the Flexi Multiradio BTS resolves the IP address of the new neighbor site and exchange the neighbor cell information via X2. Removed cells which go out of service with the whole site are removed after some time by the ANR optimization function. The function monitors e.g. handovers from or to cells and if there is no activity for a longer time it removes the cell from the neighbor relation table.




Automated Neighbor Relation Establishment for IRAT: The relevant UTRAN network configuration respectively plan data will be needed (study item)

Note: from radio perspective it is not necessary to deploy the removal information in real time to all neighbors. As soon as a cell goes out of service no UE will ask for a handover to this cell ID.

Removal or adding of cell belonging to an existing site:

LTE Neighbor cell configuration with preplanned IP addresses: The relations to existing sites respectively their cells are automatically updated via the X2 interface utilizing the X2-Update message.

3GPP Automated Neighbor Relation (ANR) support for LTE The relations to existing sites respectively their cells are automatically updated via the X2 interface utilizing the X2-Update message.

Automated Neighbor Relation Establishment for IRAT: The relevant UTRAN network configuration respectively plan data will be needed.

4.5 Multivendor support LTE Neighbor cell configuration with preplanned IP addresses other vendors not supported

3GPP Automated Neighbor Relation (ANR) support for LTE no impacts, works with every 3GPP compliant vendor

Automated Neighbor Relation Establishment for IRAT: as this is handled via the NetAct Northbound interface it has no impacts to the Flexi Multiradio BTS. If the UTRAN sites are from different vendors operated each with their own domain manager then NetAct needs to convert and merge the data of multiple vendors on import side.

4.6 Handling of X2 continuity After the initial SCTP communication link set-up the connection is monitored by the SCTP layer supervision were an SCTP instance monitors all transmission paths to the peer by heartbeats (RFC 2960 and RFC 4960).

Both peers respectively eNB maintain states that an instance of the SCTP protocol enters while an association is established, and when it is taken down again.

SCTP signaling association will be automatically re-established after return of connectivity.




Using the inherent congestion control of the SCTP protocol SCTP uses an end-to-end window based flow and congestion control mechanism were each stream is individually controlled.




5. Self Optimization 5.1 Autonomous network optimization at network launch

At network launch it is important to understand the network behavior, so the monitoring of the network to learn about proper optimization areas is the first step to getting to an optimized network.

The self-optimization is normally not of the highest importance in the beginning as the load per cell will be not exceptional and network coverage is still evolving. Nevertheless it is important to have

With NetAct Optimizer Nokia Siemens Network provides the tool for network wide optimization analysis offering:

- Detailed analysis of the exceptional cells - Health check analysis - Visualization of cell alarm history

The planned NetAct Optimizer scope in RL10 is mainly configuration support and network overview.

The Flexi Multiradio BTS localized optimization features in the beginning are: eNB scheduler supporting automated tuning functions e.g. Scheduler performs CQI adaptation in order to compensates possible non-idealities of the link adaptation, takes traffic volume based on BSR into account.

CL UL power control to achieve correct UL power control

5.2 Self Optimization setup - Operator policies SON Optimization is to a large extent impacting Radio Resource Management and automating the tasks which have been done previously with operator intervention.

In addition the communication needed between nodes is not longer limited to the management plane but utilize now direct control plane on the S1 and X2 links. The Flexi Multiradio BTS is therefore able to optimize in a very fast way the radio channel behavior on its own depending channel measurements. It can communicate decisions directly to neighbor site respectively ask neighbor sites without involving EMS/NMS.

If the optimization goes more common like network wide physical cell ID planning then NMS located optimization should be the proper place.




Figure 23 : Local versus centralized optimization

For all real time optimization on radio side like scheduler resource block assignments an operator control makes no sense (except fixing value boundaries) for other an additional operator control may be suitable.

So for localized optimization in Flexi Multiradio BTS parameter settings by the operator will steer the algorithms. For centralized optimization with NetAct Optimizer break points are planned to be supported, which allows the operator to intervene, in case he would like to. Generally the definition of what is seen as the optimum needs to be mutually agreed with operator involvement for algorithms steering.

5.3 Self Optimization: Data sources used Nokia Siemens Network NetAct Optimizer Application is utilizing all performance data coming from the network, as well as the configuration settings actual valid in the network. For instance with the help of KPIs and other monitored data Optimizer provides

- Visualization of the LTE configuration, parameters and KPIs - Physical Cell Identity Management for LTE Networks - Automatic Neighbor Relation Optimization for LTE Networks - Support for Flexi Multiradio auto-configuration for LTE Networks




Figure 24 : NetAct Optimizer multi vendor support

The localized optimization in Flexi Multiradio BTS is using trigger points from local available messages and measurements.

5.4 Localized SON features Besides the centralized optimization algorithms based on NetAct Optimizer Nokia Siemens Networks is also implementing distributed self optimization solutions, which will complement the centralized functionalities depending on the employed time scale and scope of optimization. Independent from the architecture both approaches will be implemented such that configuration and monitoring of the algorithms according to the policies of the ordering party will be uniform and requiring minimal human effort.

An example of both possible solutions is seen with RACH optimization. A localized optimization can be used for short term traffic change reactions based on demand requests in eNB, whereas the centralized optimization can consider long term traffic behavior in a cell and detect possible shortfalls based on counters and network evaluation data.

In the Flexi Multiradio BTS we do support from the very beginning localized optimization which may be called as well Intelligent Adaptive Algorithms in RRM / Telecom.

Examples for these are:




5.4.1 Efficient usage of PDCCH resources via Link adaptation Fast link adaptation for the PDCCH selects - code rate / CCE (channel control element) aggregation level [1/12, 1/6, 1/3 and 2/3 rsp. 8 CCEs, 4 CCEs, 2 CCEs and 1 CCE ]

based on - CQI reports - available PDCCH resources

This algorithm runs UE specific.

Link Adaptation(PDCCH)

eNBC

QI v

alue

: A

CQ

I val

ue: B

Code rate/ CCE per UE

Available PDCCH resources per TTI

Figure 25 : Link adaptation

5.4.2 Optimization of handover parameters The optimization of handover parameters (intra and inter eNB X2 HO) are performed as a localized solution based on

Event-triggered reporting from UE Best cell change triggered Coverage triggered measurement reporting Configurable threshold values Even this is basic mobility feature to make the cellular system work in reliable manner.

5.4.3 CQI adaptation (DL) Flexi Multiradio BTS adds a CQI offset to the reported CQI in order to compensates possible non-idealities of the link adaptation, e.g. CQI estimation error of the UE




It offers an operator adjustable target BLER value. It used an average transport block error of 1st transport block transmission

With this the UEs are normalized and Link adaptation behavior is controlled with the remedy of UE measurement errors.

CQI Adaptation

eNB

CQ

I val

ue: A

CQ

I val

ue: B

A + xB + y

Figure 26 : CQI adaptation

5.4.4 Link adaptation by AMC (UL/DL) This is the most essential radio link control function for optimizing the air interface performance.

The link adaptation function in eNB is done per UE and downlink / uplink.

Based on reception quality estimate, which reflects temporary coverage and interference condition as - CQI report from UE for DL data channel - Signaling payload, CQI report for DL common channel (PDCCH) - BLER measurements in eNB for Uplink the selection of the modulation and channel coding is done.




AMC

eNBModulation

Channel coding

CQ

I val

ue

BLE

R

CQ

I val

ue

BLE

R

CQ

I val

ue

BLE

R

CQ

I val

ue

BLE

R

Figure 27 : Link adaptation by AMC

5.4.5 Closed loop UL power control The closed loop function adapts the fast open loop behavior based on receive signal level and quality measures.

With the adaptive UL power control the network planning is simplified, enhances UL performance and reduces UE power dissipation.

The Flexi Multiradio BTS measures received signal quality (e.g. SINR) and signal level, so that the Power offset is effectively adjusted for optimal reception quality per UE.

No complicated manual radio link configuration is required and the operator can configure target window for signal quality and level.

Operator may enable or disable closed loop mode by O&M setting.

IncreaseUL power

DecreaseUL power

Figure 28 : Closed loop power control




5.4.6 Downlink adaptive open loop MIMO for two antennas The Flexi Multiradio BTS selects dynamically between TX diversity (SFBC) and open loop spatial multiplexing with large CDD.

With this it can

gain of high peak rates (two code words) and good cell edge performance (single code word)

Either two code words (A+B) are transmitted in parallel to one UE which doubles the peak rate or one code word A is transmitted via two antennas to one UE which improves the link budget (TX div, SFBC).

The dynamic switch takes into account the UE specific link quality and rank information.

AB

A

Figure 29 : Adaptive open loop MIMO

5.4.7 Support of group hopping for the uplink reference signal With this feature there is no need for reference signal planning and configuration.

There is randomized usage of reference signal of PUCCH and PUSCH in UL. For which 17 group hopping patterns are defined.

The group hopping pattern is derived from the physical cell ID.




UL referencesignal assignment

eNB

Phy.

Cel

l ID

Phy.

Cel

l ID

Group 1 ..17

Figure 30 : Group hopping for UL reference signal

5.4.8 Fair scheduler (UL/DL) Fair scheduling strategies are provided in downlink and uplink utilizing both time and frequency domain multiplexing of multiple users. The downlink resource allocation is channel-aware, while in uplink random frequency allocation is applied.

The Fair scheduler is necessary for efficient usage of HW and radio resources.

Common channels, like system information, random access, paging etc., are scheduled with highest priority before scheduling any dedicated channels.

Operator can configure the following parameters to steer the PS behavior: - Maximum bit rate for downlink and for uplink (will be replaced by UE capability constraint and by UE-AMBR enforcement) - Minimum bit rate for downlink and for uplink - Maximum number of UEs scheduled per TTI for downlink and for uplink

Scheduler

eNB

Allocated resources per TTI

Figure 31 : Fair scheduler




5.4.9 Advanced target cell selection and handover retry for intra frequency handover

The target of this feature is to achieve higher handover success rates.

An intelligent selection of target cells and handover retry is done based on target cell selection which uses only cells with -X2 connectivity of target eNB -S1 connectivity of target eNB - no entry in blacklist.

If a handover with one entry of the target cell list fails the next entry of that list will be used to retry a handover.

Inter eNB H

andover

Intra

eNB

Han

dove

r

Intra

eNB

Han

dove

r

9Not in blacklist}9S1 available ?}9X2 available ?}

9Not in blacklist}9S1 available ?}9X2 available ?}

Figure 32 : Advanced target Cell selection

5.4.10 S1 Flex load balancing The Flexi Multiradio BTS can be connected simultaneously up to eight different MMEs within one PLMN.

A load balancing algorithm is used to balance the load between the MMEs which uses the assigned MME weights.

A re-balancing will be started with

successful S1 setup successful MME configuration update S1 reset




S1-MME failure

1 ..8

Flexi Multimode BTS

MMEMME

MMEMME

MMEMME

Figure 33 : S1 load balancing

5.5 Centralized SON 5.5.1 Overview

Using NetAct Optimizer for initial parameter tuning and for visualization and analysis of the LTE network on a geographical view helps to ease decision making and to reduce the operational effort for network optimization and configuration.

As LTE matures and demand for capacity increases only optimal utilization of all network resources will enable the ordering party to efficiently harvest the entire available revenue potential.

NetAct Optimizer is the key part of the centralized SON solution of Nokia Siemens Networks. It provides means to visualize the network situation and to execute the optimization actions via the in-built algorithms. The optimization process frequency and automation level can be adjusted by the operator to meet the needs.




OptimizerNetAct

NetActOptimizer

NetActOptimizer

Configurator Reporter

Figure 34 : NetAct Optimizer

Visualization of the actual network topology, parameters and KPIs, Identifying rollout errors, areas with poor performance, lack of capacity etc. The Visualization can be tuned to view the important network performance aspects. Visualization provides automated and effortless means of viewing the actual network status and provides analysis of reasons for problems.

Optimizer provides the algorithms to find optimal values for the key parameters. Optimization is based on mid or long-term statistics and focuses on cases when many cells are involved in optimization.

Optimizer will receive the network configuration, performance and other optimization related data automatically from LTE NEs by using the interfaces of NetAct. Also information from other network technologies (GSM, WCDMA) managed by NetAct management system is automatically available. The other vendor network elements can be integrated to NetAct from the other managements systems.




Another striking advantage of NetAct Optimizer is related to the fact that after LTE roll-out the ordering party will be faced with a simultaneous operation of three different radio technologies. Since NetAct Optimizer is multi-technology capable form day one, joint optimization of LTE and GSM/WCDMA will be possible in an efficient way.

So NetAct Optimizer is seen as major part in following areas:

Visualization and analysis functionality

Visualization of LTE network Topology, parameters, KPIs in one view Geographical visualization and analysis KPIs and parameters automatically on map

Measurement based optimization for the key tasks

Physical Cell Identity Management Neighbor cell relation optimization Interference reduction optimization Coverage and capacity Optimization Handover optimization and load balancing optimization Radio optimizations like RACH optimization

Tight interworking with NetAct Configurator for automated network re-configuration

optimization results stored as new configuration plans in Configurator database

automated distribution and activation to impacted eNB

5.5.2 Physical Cell ID Management NetAct Optimizer plays an active role in providing the physical Cell IDs to the Flexi Multiradio Configuration.

It is proposed to do the assignment of the physical cell IDs automatically with the help of NetAct Optimizer for initial deployment. NetAct Optimizer bases its algorithm for proper distribution of the values on the other configuration data of the eNB in the network.




Optimizer

PMCMPMCM

Configurator

7777

Figure 35 : PID assignment

The assignment proposals will be done collision and confusion free. The key principle is to check the identity codes of neighboring cells and neighbors neighbors. The operator can then decide to accept the proposed values via NetAct Configurator into the eNB settings in the network.

NetAct Optimizer will also support a check of already available physical cell id allocations in the actual network. Optimizer can detect the collisions and correct these. The collision detection and correction can be scheduled to happen frequently or otherwise when needed.

In light of 3GPP definitions from Nokia Siemens Networks perspective the physical Cell ID handling needs to be standardized in Release 9. These can be used for enhancing the network settings in case of detected collisions.

5.5.3 Auto configuration support NetAct Optimizer together with Configurator is able to dynamically complete network planning for distinct Flexi Multiradio BTS with automated procedure for on-line planning for a new Flexi Multiradio BTS appearing in the RAN.

If a new Flexi Multiradio BTS registers at NetAct SON Coordinator it triggers Optimizer to create missing parts of the configuration plan file. Optimizer defines initial radio configuration such as neighbor relations, physical cell IDs and other parameters, taking into account the existing neighbor sites from geographical neighboring and further network plan data. Optimizer provides / completes not only the configuration plan for the new Flexi Multiradio BTS but it suggest also new and adopted values for the parameters of the surrounding sites and cells, e.g. modified power and antenna tilt values.




The configuration proposal for the new eNB and all impacted neighbor eNB are reported to Configurator which finalizes the configuration plan information and sends them down to the eNBs to be either activated automatically or on operator request.

Figure 36 : Optimizer Auto configuration support

5.5.4 RACH Optimization The configuration of the RACH has great impact on the performance of mobile cellular radio networks. It significantly affects the probability of blocked access attempts from the UEs and leads to delays and reduced success rates in connection setup and handover.

RACH optimization is seen as to be possibly optimized locally and also centrally.

The target of optimization of RACH is understood as to adapt the number of RACH access slot to the RACH traffic load. The RACH load measurements are used as basis to optimize RACH configurations. Finally an optimized setting leads to




Reduced call setup delays Reduced HO delays High call setup and HO success rate Optimization of Capacity

A localized optimization can be used for short term traffic change reactions based on demand requests in eNB, e.g. when a sudden high traffic request is coming along, e.g. when an advertisement is announced.

The centralized optimization can consider long term traffic behavior in a cell and detect possible shortfalls based on counters and network evaluation data. Nokia Siemens Networks solution for central RACH optimization will be based in NetAct Optimizer. Thresholds e.g. to supervise RACH overload can be done with PM based alarming.

The optimization process frequency can be adjusted by the operator according to configurable thresholds or schedules etc. Therefore, the optimization, centralized settings of RACH can be triggered with the overload threshold, if necessary.

Optimizer can also analyze the RACH load status of the neighboring eNB.

The actual settings of RACH in each eNB can be followed with NetAct Configurator. That application can also be used for centralized provisioning of the new values to all eNBs.

RACH optimization is as other optimization scenarios still in analysis phase, whereas especially the localized approach in eNBs needs careful check of advantages of short term reactions to any drawbacks coming along with it.

5.5.5 ANR Optimization The Optimizer neighbor cell optimization is based on statistically reliable data derived from the measurements collected by terminals and eNB during their normal operation.

Compared with the localized eNB cell optimization it works in a mid to long term schedule.

It uploads existing configuration and Optimizer suggests white or blacklisting of neighbor cell relations.

Reports for the new eNB attributes are exported to NetAct Configurator.




Optimizer

PMCMPMCM

Configurator

No HO

Figure 37 : Optimizer ANR optimization

5.5.6 QoS related parameter Optimization QoS related optimization becomes essential when the LTE network is highly loaded with various kind of traffic. Therefore Nokia Siemens Networks does consider this optimization within RL30 timeframe. Before that, however, it will be essential to be able to monitor the location, volumes and performance of different types of traffic in LTE networks. Therefore the QoS differentiation mechanisms and Visualization capabilities are provided in the solutions of Nokia Siemens Networks.

Nokia Siemens Networks solution will support the standardized QCI values in different steps in upcoming releases and support for operator defined QCIs is seen as study item. The QCI values will be assigned per bearer and the QCI tables will be definable per BTS.

The Flexi Multiradio BTS will provide measurements related to QCIs and these measurements will be available as well via the NetAct Northbound interface as other Performance Data.

The SON solution of Nokia Siemens Networks will support not only the standard 3GPP QCIs but will complement the capabilities with some additional parameters.

The initial settings for all QCI parameters can be made in NetAct Configurator by using the cell parameter templates.




Interference reduction optimization

Interference reduction is a use case in which a centralized approach is preferred, as several dependent parameter evaluations need to be taken into account for this.

Other optimization use cases are considered in the area of neighbor list handling at installation/removal of eNBs, which is described in under 4.7.3 chapter 1).

The different optimization use cases are still under investigation from the real improvements they will bring into the real lifetime network.

5.6 Coverage and Capacity Optimization Controlling the LTE network interference in network management level is essential for maximizing the overall network performance. The most accurate way to handle this is by relying on the accurate network measurements. NetAct Optimizer as part of centralized SON solution will therefore help the operator to improve the network performance with cost efficient means.

In the first release Optimizer will provide views for automated interference situation analysis. In subsequent releases the parameter optimization algorithms can be linked to the analysis.

The Flexi Multiradio BTS will also support optimizing the network in localized manner. Several features are realized in Flexi Multiradio BTS which do require only local knowledge and can react on short term.

In the LTE network of Nokia Siemens Networks a frequency re-use of one will be used.

The eNB scheduler is supporting automated tuning functions e.g. Scheduler performs CQI adaptation in order to compensate possible non-idealities of the link adaptation, takes traffic volume based on BSR into account.

TTI bundling will be done to get cell edge improvements Semi-persistent scheduling is supported to enhance the voice capacity CL UL power control to achieve correct UL power control PDCCH power control to enhance DL control channel capacity

However, as power, especially eNB DL transmit signal power, has impact on the LTE network coverage in general it is not enough to leave it for eNBs only. When adjusting the power level of one cell the impact on surrounding cells has to be taken into account to ensure e.g. maintenance of HO capability.

Documents

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