lte self organizing networks (son) - afralti · engineering and installation services” “son...

LTE Self Organizing Networks (SON)

AGENDA

• SON Drivers and Functionalities

• SON Use Cases & Solutions

• SON Benefits

Drivers For Self-Organization

3GPP Long Term Evolution LTE and Wireless Sensor Networks (WSNs)

Dr.-Ing. Abdalkarim Awad

• High complexity and high number of parameters• Operation of heterogeneous networks• Expanding number of Base Stations (BSs)

– Introducing of home evolved NodeBs (eNodeBs) leads to a hugenumber of nodes to be operated in multi-vendor scenarios

OPEX is expanding• Reduction of OPEX requires reducing human interactions by

– Configuring and optimizing the network automatically whileallowing the operator to be the final control instance

• High quality must be ensured SONs are essential

Drivers For Self-Organization



• SON can improve the network performance and quality ofservice. This can be achieved through applying differenttechniques that can optimize the performance of thenetwork.

• Unlike 2G and 3G, in next generation mobile communicationnetworks, there will be no need for RNC. Therefore theeNodeBs will be more interactive.

• There is room for cooperative management of basestations among different operators.

Why do we need SON?

Plan Deploy Optimise Maintain

Self Configuration Function Reduces CAPEX and OPEX

Self Optimization and Energy Saving Function

Reduces CAPEX and OPEX

Self Optimisation and Self Healing Improves User Experience

“About 24 % of a typical wireless operator’s revenue goes to network OPEX”

“About 17 % of wireless operator’s CAPEX is spent on engineering and installation services”

“SON will improve the operational efficiency by >60%”

SON benefits during the four steps of the mobile network lifecycle [Source: Analysys Mason, 2012]

Functionalities of SONs

CATEGORIES OF SON FEATURES • Self-Configuration

Autonomous configuration of parameters during commissioning

• Self-OptimisationContinuous improvement of service quality, network performance, and network capacity

• Self-HealingDetection, analysis, and mitigation of network outages

Self- Optimization

Auto-tune

Self-Healing Auto-repair

Self- Configuration Plug-and-Play

Functionalities of SONs

Self-Configuration (plug and play)

Self-Optimization (auto-tune)

Self-Healing (auto-repair)

Self-Planning (dynm

ic re-computation)



• Auto-setup• Auto- detection • ...

neighbour

• Coverage & capacity• Mobility robustness• Load balancing• ...

• HW/SW failuredetection

• Cell outage detection• ...

Self-Configuration



• Definition– “The process where newly deployed eNBs are configured by

automatic installation procedures to get the configuration for system operation”

• Works in preoperational state

• How– Create logical associations with the network

necessary basic

• Establishment of necessary security contexts (providing asecure control channel between new elements and servers inthe network)

– Download configuration files from a configuration server (usingNETCONF protocol)

– Doing a self-test to ensure that everything is working as intended

Self-Configuration

eNB

eNB 4. Transport and radio configuration

eNB

1. IP address allocation, self-configuration subsystem detection

GW

Self-configuration subsystem

Normal OAM subsystem

OAM subsystem 3GPP Long Term Evolution LTE and Wireless Sensor Networks (WSNs)


Self-Optimization



• Definition– “The process where User Equipments‟ (UE) and eNBs‟

performance measurements are used to auto tune the network”• Works in operational state

• How– Optimizing the configuration while taking into account regional

characteristics of radio propagation, traffic and UEs mobility– Analysis of statistics and deciding what are optimal parameters– Detecting problems with quality, identifies the root cause, and

automatically takes remedial actions• Examples: neighbor list optimization, coverage optimization,

etc.

Self-Healing



• Definition– “The process enabling the system detecting the problems by

itself and mitigating them whilst avoiding user impact and reducing maintenance costs”

• Works in operational state• End-to-end service recovery time should be < 1 sec• How

performance degradation

– Automated fault detection– Root cause identification– Recovery actions application– If fault cannot be resolved, do some actions to avoid

SON IMPLEMENTATIONS

NMS manages the policies Network Management Systems

Some SON functions are implemented in the EMS Element Manager Systems

The eNB implements some SON functions and analyzes UE measurements Network Elements

The UE performs over-the-air measurements User Equipment

SON implementations are typically multi-layered in a distributed, centralized, or hybrid architecture.

Spee

d Re

quire

d

Num

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f Sec

tors

SON LIFECYCLE

Deployment Phase Optimization Phase Maintenance Phase

Self-Configuration • Automatic SW Download• Automatic Neighbor Relation• Automatic PCI• …

Self-Optimization • Interference Reduction• Load Balancing• RACH Optimization• …

Self-Healing • Capacity & Coverage

Optimization• Cell Outage Detection• Self-healing• …

Release 8

Release 9 Release 10

NETWORK LIFECYCLE

Optimization Phase Deployment Phase

3GPP TS36.902 1. Coverage and Capacity Optimization

(Rel 9,10);2. Energy Savings (Rel 9);3. Interference Reduction (Rel 10);4. Automated Configuration of Physical

Cell Identity (Rel 8);5. Mobility Robustness Optimization

(Rel 9,10);6. Mobility Load Balancing Optimization

(Rel 8,9,10);7. RACH Optimization (Rel 9);8. Automatic Neighbor Relation Function

(Rel 8,9);9. Inter-cell Interference Coordination

(Rel 8,9)

SON

Coverage and Capacity

Optimization

Energy Savings

Mobility Robustness

Optimization

Mobility Load Balancing

Optimization

Inter-cell Interference Coordination

Automatic Neighbor Relation

RACH Optimization

Automated Configuration

of Physical Cell Identity

Interference Reduction

3GPP TS36.902

1. Coverage and Capacity Optimization• Discovery of coverage and capacity problems automatically through the measurements at

the eNB and those reported by UEs. It minimizes the human intervention and reduces thefeedback delay.

• Providing optimal coverage• Providing optimal capacity• Ability to balance the trade-off between coverage and capacity

2. Energy Savings• Reduction of energy consumption by the eNBs during normal operating circumstances• Powering down of eNBs when not required to provide capacity or coverage.

3. Interference Reduction• Switching off cells that do not support traffic for a defined period of time (particularly home

eNodeB, femtocell…).

NGMN Use Case Definitions

SON Use Cases and Solutions



What Are The Use Cases Defined In 3GPP?



• Automatic Neighbor Relation (ANR)• Coverage and capacity optimization• Energy saving• Interference reduction• Physical cell-ID automatic configuration• Mobility robust optimization• Mobility load balancing optimization• Random Access Channel (RACH) optimization

Automatic Neighbor Relation (ANR)

• Relations between neighbor eNBs should be carefullydetermined since they affect the network performance– Handoff performance, call dropping probability, etc.

x2 x2 x2 eNB1

eNB2

eNB3

eNB4 The mobiles residing in the range of eNB2 may move to either eNB1 or eNB3 an in advance actions maybe done to optimize the performance (ressources reservation)



Automatic Neighbor Relation (ANR)



• ANRs covers following steps– Neighbor cell discovery

• eNB instructs UEs to do measurements

• New joined eNBs are detected based on the analysis ofmeasurent results

– Configuration of X2 interfaces between eNBs– Connection setup with neighbor eNBs– ANR optimization

• Update as new eNBs join/disjoin the network

• How to accurately optimize the neighbor relation is still an openissue till now

• Some steps work in preoperational state, while someothers work in operational state


• ObjectiveAutomation of neighbor relations.

• BenefitsMinimize manual handling of neighbor relations i.e. increase the number of successful handovers and reduce dropped connections due to missing neighbor relations.

• DescriptionAutomatic discovery and setup of neighbor relations when a user (UE)moves from a serving eNB to another (target) eNB, including automatedsetup of the X2 interface between eNBs, primarily used for handover.


• Process– The UE reports all detected PCIs

(Physical Cell Identities)– For an unknown PCI, SAE may

request the GCI from the UE– With the GCI, the eNB can

request the IP address from theMME and setup an X2connection

– The eNBs exchange informationand update their neighbor’s lists

– Unused neighbor relations canbe removed later Serving

eNodeB

MME DHCP/DNS S/P--GW ConfigurationDB

UE

Target eNodeB

S1 S1

S1

Coverage & Capacity Optimization • Goal

– Maximizingrequirements

the capacity while ensuring coverage

• Holes free coverage• Improved capacity with given

• Works in operational state• 3 Cases

resources

− LTE coverage holes within other Radio Access Technologies (RATs) • QoS degradation due to

frequent inter RAT handoffsNon LTE coverage LTE coverage

LTE cell smaller than planned

Coverage & Capacity Optimization

– LTE coverage holes and no alternative RAT• Significant call drops due to coverage holes



Coverage & Capacity Optimization – Isolated LTE cells

• Coverage blackouts in network‟s border areas



Coverage & Capacity Optimization

• Solution– Update the BS parameters

such as height, tilt and Txpower



Energy Saving



• Goal– Reduction of OPEX by saving energy resources

• Works in operational state• How can energy be saved

– Tx power optimization• Minimal saving but possible throughout the day

– Switching off some of the Tx of a cell• Possible where antenna diversity is not required

– Complete eNB switch off• Maximum saving but possible only during low load times• Also if users are away from home eNB and closed subscriber

group cells

Interference Reduction



• Goal– Improving the network performance by means of reducing the

interference between its equipments• Works in operational state• Many limitations due to the applied frequency band

– Interference depends on frequency band characteristics• Solutions

– Decrease eNBs density• Hard to apply due to the capacity decrease and the existence of

home eNBs that are not under the control of the networkoperator

– Power control and/or reconfigure the wireless setup– Interference cancellation, coordination and randomization

Physical Cell-ID Automatic Configuration

•Goal– Automatically configure the physical Cell-ID (collision and

confusion free assignment of physical Cell-ID)

• Works in preoperational state– A part of self-configuration procedure

•Main limitation is that there is only 504physical Cell-IDs available

• Solution–eNB-based solution(distributed solution) –OAM-based solution(centralized solution)



Physical Cell-ID Automatic Configuration



• eNB-based solution (distributed solution)– eNB chooses an arbitrary Cell-ID– eNB instructs UEs to do measurements, collects and analyses

measurements results– eNB starts communicating with neighbors using X2 interfaces– In case the eNB has detected a conflict, a new Cell-ID is

assigned and the procedure is repeated again• OAM-based solution (centralized solution)

– eNB instructs UEs to do measurements, collects and sends theresults to the OAM

– The OAM assigns a Cell-ID to the eNB– Cell-ID assigning procedure may require doing updates to other

eNBs in the network

Mobility robust optimization

Reduce the number of HO-related RadioLink Failure (RLF) Reduce the HO-related issues that lead todegradation in the QoS.

• Failures due to too late HO triggering• Failures due to too early HOtriggering • Failures due to HO to a wrong cell

Time

Power

Too Late HO

Too Early HO

HO To wrong cell

Load Balancing • Objective

Automatically spread user traffic across the system’s radio resources as necessary in order to provide quality end-user experience and performance, while simultaneously optimizing system capacity.

• BenefitsIncreased QoS, network performance and network capacity.

• DescriptionDistributed (via X2) or centralized (via central server) implementation. Idle or active users are transferred between eNodes by modifying cell- neighbor-pair parameters or user-specific parameters. Can include intra-carrier, inter- carrier, or even inter-RAT resources.

Cell A Cell B Cell C

Cell A Cell B Cell C

RACH Optimization • Objective

Automatic configuration of the Random Access Channel (RACH) parameters to minimize delays andinterferences, and optimize the performance of the RACH.

• BenefitsIncreased QoS, network performance and network capacity : shorter call setup delays, shorterhandover delays, higher call setup success rate, higher handover success rate

• DescriptionAutomated setting of parameters related to the performance of the RACH (exact list is still forfurther study)

Source: RACH Procedure 3GPP TR 36.902 V9.1.0 (2010-03)

Inter-cell Interference Coordination • Objective

Coordinated usage of Physical Resource Blocks (PRBs) in the related cells leading to reduce interference (and thus improved throughput) on both the uplink from other UEs and on the downlink from other eNBs (particularly on the cell edge).

• BenefitsImproved overall network performance and capacity.

• DescriptionThe eNB automatically adjust its powerand scheduling of physical resource blockssettings to avoid inter-cell interference

eNodeB-2 eNodeB-3

eNodeB-1

ICIC

eNode-B Self-Configuration

• ObjectiveReduce human intervention in the overall installation process with “plug and play” functionality in the eNodeBs

• BenefitsFaster network deployment, reduced equipment configuration costs, and improved inventory management system.

• DescriptionSeveral distinct functions such as Automatic Software Management, SelfTest and Automatic Neighbor Relation configuration.

eNode-B Self-Configuration

• Prerequisites– RF and transport parameters

available in the configurationserver

– Latest SW package available

• Actions on boot-up– Self-test & self-discovery– Connection to DHCP/DNS (IP

addresses of key servers)– Secure tunnels to the

configuration servereNodeB

NEW eNodeB

MME DHCP/DNS S/P--GW

eNodeB

Configuration Server

Tracking Area Planning

• ObjectiveAutomation of optimized tracking areas.

• BenefitsReduced network costs with an optimized trade-off between the registration update signalling traffic load (when a UE moves from one TA to another) and the paging signalling traffic load (all eNodeBs within a TA are paged when the UE receives a call).

• DescriptionThe SON algorithm actively monitors the Tracking Area Updates (TAU) andthe load on the radio access channel (RACH) and allocate eNodeBs to theappropriate TA in order to reduce the overall signalling load.

SON Benefits

SON Benefits

Reduction of Capex & Opex Savings

Improved User Experience

Improved Network Performance and Qos

Optimized Coverage and Capacity Additional revenue from the higher data rates available from LTE

SON BENEFITS

Relative SON benefits for LTE networks

Source : Analysys Mason 2012

SON BENEFITS

3-year SON benefits for large US operator Source : Analysys Mason 2012

THANK YOU

lte self organizing networks (son) - afralti · engineering and installation services” “son...

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