INFORMS Keynote Capone

8/13/2019 INFORMS Keynote Capone

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Politecnico di Milano

Advanced Network Technologies Laboratory

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From Pre-Planned to Self-Organizingand Green Wireless Networks

Antonio Capone

The 10th INFORMS Telecommunications

Conference

Concordia University, May 5 - 7, 2010


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Disclaimer:Engineers and Mathematicians

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Picture borrowed from:A. Eisenbltter, H.-F. Geerdes, Wireless Network Design: Solution-oriented

Modeling And Mathematical Optimization, IEEE Wireless Communications, December 2006


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Summary

Wireless networks Radio planning evolution (2G and 3G)

Coverage Planning

Capacity Planning

Self-organizing networks (4G) Complexity of network management

4G systems (LTE)

Concept of SON

Dynamic resource management

Wireless Green networks

Energy consumption

Green energy management

Conclusion


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Phones

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Mobile phones

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Cellular subscribers vs fixedlines

6

0

500

1000

1500

2000

2500

3000

3500

1990 1995 2000 2005 2007 2010

Cellular

Subscribers

Telephone Lines

Source: www.etforecasts.com

M bil fi d


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Mobile vs fixed vsinternet

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60 mobile subscribers per 100 inhabitants 19fixed lines per 100 inhabitants

23internet users per 100 inhabitants

9 broadband users per 100 inhabitants

Source: ITUData: 2008


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Mobile subscribers bycountry

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Radio planning

The deployment of mobile radio networksrequired so far HUGE investments

The extension of existing network, new dataservices, and new technologies are continuing

to require a lot of money This has stimulated mobile operators to use

automatic tools for the design and theoptimization of their networks

In the last ~15 years the research communityhas proposed a large number of approaches fordesigning and optimizing wireless accessnetworks (more than 16000 results in GoogleScholar)

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Network planning tools

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Main PlanningTools:

Aircom Asset

Mentum Planet

Atoll FORSK

ATDI

WinProp

EDX Signal Pro

CelPlan

Siradel

Pathloss

Main OptimizationEngines

Actix

Capesso


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What is radio planning?

The basic decisions that must be taken duringthe radio planning phase are: Where to install base stations (or access points,

depending on the technology) How to configure base stations (antenna type,

height, sectors orientation, tilt, maximum power,

device capacity, etc.)

XX

XX

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What is radio planning? This is, however, not enough

Multiple access techniques are used to define

communication channels on the available radiospectrum

Radio resources for wireless systems are limitedand must be reusedin different areas (cells)

Resource reuse generates interference

FDMA TDMA CDMA

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Interference

Interference is the key parameter that drivesnetwork planning and optimization processes

Interference can be tolerated (goodcommunication quality) if the Signal-to-Interference and Noise Ratio (SINR)is high

enough

SIR constraint limits the number of simultaneouscommunications per cells, i.e. the systemcapacity

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GOAL:minimize costs

maximize covered traffic

inout

rec

II

PSFSINR


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2G Planning

FDMA/TDMA cellular systems adopt a two phases radioplanning

Coverage planning

Capacity planning (frequency assignment)

Coverage planning:

Select where to install base stations

Select antenna configurations

s.t. constraints on signal level in the area

Capacity planning:

Define which radio resources can be used by eachcell

s.t. SINR (quality) constraints

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Coverage Planning Many different models have been proposed for

the coverage planning

Basically all of them are based on the classicalset covering problem

With several specific features that have been

added depending on technology and service mix

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min Objective function:total network cost

Full coverage constraints

One configuration per site

Integrality constraints


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Coverage Planning

Example: Cell overlap

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Cell overlap may be requiredfor mobility management

Overlap can negatively affectcapacity (e.g. in WLANs)

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Capacity planning(aka frequency assignment)

After coverage planning,capacity planning is in chargeof defining which radioresources can be used by

each cell

The amount of resources(frequencies) assigned to cells

determines system capacity Frequencies can be reused,

but SINR (quality) constraintsmust be enforced

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F2

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Frequency assignment

Maximizing the simultaneoustransmission with SINRconstraints is a key problem isall wireless networks

ij

SINRij>t

However, the most popularmodels for frequencyassignment have been basedon compatibility graphs

Frequency assignment problems

are modeled as variants of the

graph coloring problems

i j

cij

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Frequency assignment

Since Graph based models do not considerSINR constrains explicitly the cumulative effectof interference is not accouter for

Compatible?

Minimum InterferenceFrequency AssignmentProblem (MI-FAP) andits variants modelsdirectly interferenceeffect

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3G Planning

3rd Generation Systems are based on W-CDMA(UMTS)

Two-phases approach not suitable because:

Channels are shared and there is no frequencyplanning for CDMA

Coverage depends on SINR values

Joint coverage and capacity planning

SINR constraints make the problem ageneralization of the capacitated facility

location problems

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N t k t &


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Network management &control

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Network configuration and optimization is becoming

far too complex for mobile operators


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4G Long Term Evolution

The need to plan, configure, manage a newwireless network from scratch

with up to 10 times more base stations

and many more parameters to set

simply worries mobile operators

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LTE architecture

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eNB

MME / S-GW MME / S-GW

eNB

eNB

S1

S1

S1

S1

X2

X2X2

E-UTRAN

The radio architecture

of LTE is more complex

Base stations (eNodeB)are connected alsoamong them (mesh

topology) and they have

computation capabilityto perform advancesfunctions

The presence offemto-cellscanmake the networkmanagement evenmore complicated


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LTE radio interface

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More similar to 2G than to 3G

S lf O i i N t k


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Self Organizing Network(SON)

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Self Planning

Self Configuration

Self Optimizationand Self Tuning

Self Testing andSelf Healing

Self Mantenance

PerformanceImprovement

Cost reduction

self-organizing network is a cellular network in

which the tasks of configuring, operating, andoptimizing are largely automated.


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Self Organizing Network


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Self Organizing Network(SON)

Most of the SON features are aimed at simplifyingpreoperational and operational procedures

HW configuration

SW installation and configuration

Radio basic parameters

Transport parameters

Etc.

However, the most interesting issues from ourperspective are related to the configuration and

management of radio resources

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Automaticcarrier

selectionFractional reuse Load balancing


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Dynamic assignment

The idea of self-configuring and self-optimizing

wireless network is not new!

Several Dynamic Channel Assignment (DCA)schemes have been proposed and analyzed for 2G

Channel/frequency assigned on demand based on

compatibility or interference constraints

but they have never been used in real networks

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Resource assignment in LTE

LTE-advanced offers several instrumentsto make configuration and dynamicmanagement of radio resources possible

eNBs can make measurements over the

radio interface before first resourceconfiguration

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User terminals can providemeasurements to eNBsduring system operationto dynamically selectresources


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Resource assignment in LTE

Defining both centralized and distributedself-configuration and self-optimizationmodels and algorithms for LTE is still anopen problem

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Automatic carrier selection

Channel assignment basedon position in the cell

(fractional reuse) Load balancing among cells

forcing handover

Etc.


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Green Wireless Networks

In addition to configuration, energyconsumption of wireless network is anotherissue that concerns of operators

The power consumption of cellular networks

infrastructure (base stations and core network)doubles every 4-5 years - to 60 TWh in 2008

Energy consumption of mobile telephonyoperators in Italy is 0,7% of total nationalelectric consumption, 55% of wholecommunications sector, with bills of more than300Mper year

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Energy consumption

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Radio accessand core

network

Base

Stations

80%

Mobile

Stations

Network

90%

User

Terminals

10%

Mobile

Network20%


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Energy consumption

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Energy Savings

Significant energy savings can be achieved ifparts or all components of some wirelessnetwork devices are powered off when traffic islow, and powered on based on the volume andlocation of user demand

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Energy Savings

It is also possible to partially switchoff internal modules of base stations

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Base Station

Cabinet

TRXs

Air

Conditioner


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Green Network Management

Switching on and off networkelements based on traffic level

Re-planning of the network based on

different traffic scenarios

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Green Network Management

Radio Planning models can be re-used But some additional features need to be

modeled like:

Coverage and capacity constraints

Cost of network reconfiguration

Performance Energy trade off

Etc.

Energy saving is one of the issues thatis being considered as part of SelfOrganizing Network by standardizationbodies and manufacturers

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Conclusion

The need to plan and manage newgeneration wireless network in a costeffective way is even more acute now thanin the past

Network complexity is increasing Network re-planning is required more

often also for energy saving

New design and management approachesare required

Dont let engineers play alone with thesenew challenging problems

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Politecnico di Milano

Advanced Network Technologies Laboratory

From Pre-Planned to Self-Organizingand Green Wireless Networks

Antonio Capone

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INFORMS Keynote Capone