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the Title Master

Concentric CellsConcentric CellsTheory and Applications

Sherif Bahieg

January 2004

Motorola and Mobilink Confidential Proprietary

Outline

• Introduction• Theory• Applications• DB Parameters and Statistic• Conclusion• What’s Next ?

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Outline

• Introduction• Theory

– Coverage Overview

– Traffic Models Overview

– Layer Management

– Types of Concentric Cells

• Applications• DB Parameters and Statistic• Conclusion• What’s Next ?

1/42


Outline

• Introduction• Theory• Applications

– Cells Upgrade (Aggressive Re-Use Pattern)

– Enhancing Quality of Service

• DB Parameters and Statistic• Conclusion• What’s Next ?

1/42


Outline

• Introduction• Theory• Applications• DB Parameters and Statistic

– DB Overview

– Statistics Overview

• Conclusion• What’s Next ?

1/42


Outline

• Introduction• Theory• Applications• DB Parameters and Statistic• Conclusion• What’s Next ?

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Introduction

• Main Definitions– Overlay

– Underlay

– Concentric Cells

– Intelligent Underlay / Overlay

– Super Re-Use


Introduction


• A capacity adding network layer using an aggressive frequency re-use pattern to obtain high spectral efficiency. These are “mini cells” providing high capacity over a limited area.

– Underlay



– Super Re-use


Introduction


– Underlay• Conventional cellular network using standard frequency re-use

pattern to ensure contiguous coverage. These are the umbrella cells providing contiguous coverage.



– Super Re-use


Introduction


– Underlay

– Concentric Cells• The use of overlay and underlay layers to provide high capacity with

contiguous coverage. The underlay maintains contiguous coverage and the overlay provides higher capacity. The layers appear as being concentric due to overlay cells having a reduced coverage area when compared with the underlay cell.


– Super Re-Use


Introduction


– Underlay


– Intelligent Underlay / Overlay• One implementation of concentric cells which manages the

placement of traffic on overlay or underlay according to dynamic measurements on interference.

– Super Re-use


Introduction


– Underlay



– Super Re-use• An aggressive frequency re-use pattern e.g. single site or two site

re-use. Geographical coverage is reduced due to co‑channel and adjacent channel interference, however within the good coverage area the spectral efficiency is high. An overlay layer is implemented using super-reuse and thus the overlay may also be known as the super-reuse layer.


Introduction

• Concentric Cells offers:

• Low cost capacity enhancement technique

• Advanced frequency re-use patterns

• Improved spectral efficiency

• Re-use of existing sites and site infrastructure

• Exploits surplus backhaul capacity

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Introduction

• Requirements– Advanced re-use patterns

– Support for moving traffic between layers

– Call processing procedures to maximize capacity

• Call originations• Handovers

– Optimal frequency plan assessment

• Capacity demand survey tools• Engineering support to analyze data• Assess optimal method to increase capacity using

concentric cells, micro cells or other methods


Theory

• Coverage Overview– Overlay/Underlay divides the coverage of a certain cell based on

the traffic and Level Distribution into a Multiplayer Environment

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Coverage Profile


Theory



Coverage Profile

X

YZ

X

YZ

X

YZ

X

YZ

Good coverage area

High interference area


Theory



Coverage Profile

Zone 0

Zone1 - Carrier A

Zone1-carrier B

The cell can be divided into multi inner zone, not only one.


Theory

• Traffic Models Overview

– Capacity gains from concentric cells requires capacity supply to

correlate with traffic location

– Choice of optimal super re-use plan according to traffic density profile

– Single site re-use pattern

• Limited coverage area• Requires concentration of traffic towards cell site

– Two site re-use pattern

• Improved coverage area • Better for general application

– Traffic models help assess the capacity gain

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Theory


• Uniform Traffic Distribution– Traffic model assumes that subscriber

density is equal over cell area

– Allows a large coverage area to be assessed for potential gain from concentric cells using a standardized frequency plan

– Uniformly divide traffic between inner and outer Zone

– CAUTION: has to be taken from Raising the blocking in outer Zone

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Theory


• Non-Uniform Traffic Distribution– Traffic model considers the effect of

traffic concentration in particular locations

– Allows detailed and accurate assessment of the capacity gain from a specific cell

– Capacity gain can be improved using hybrid frequency plans

– Requires field data study on traffic locations (capacity survey)

– CAUTION: Proper planning to the inner zone has to be considred

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Theory

• Layer Management• Overview

• Efficient management of traffic required to exploit capacity gain potential of concentric cells

• Goals

– Maximize handled capacity

– Avoid congestion

– Maintain good call quality

– Avoid unnecessary handovers

• Best system performance through optimal choice over

– Call originations

– Traffic movement between concentric cell layers

– Generalized handover situations

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A

B

C

Theory

• Layer Management• Call Origination (BCCH)

• BCCH Carrier is always considered as outer zone

• Call Origination is always done using outer zone resources

• Handovers between Layer

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• From outer to inner

Call is moving toward the site location and its level is exceeding the required threshold for handover


Theory





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• From inner to outer

Call is moving away from the site location and its level is going below the threshold

A

B

C


Theory





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• From inner to inner

• Call is moving deep toward another inner zone toward the site

• Call is moving away from the site toward another inner zone

• Call is moving from inner zone in Cell A to inner Zone in Cell B


Theory

• Types of Concentric Cells

• Power Based Algorithm• Inner zone have reduced max UL and DL transmit levels.• Intra-cell Handover of different zones is based on power

control.• Different Max. DL transmit power levels may be set for

different carriers.• One zone can be configured to sub-zones

RXLEV_DL > ZONE THRESHOLD andRXLEV_UL > ZONE THRESHOLD

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Theory

• Types of Concentric Cells

• Interference Based Algorithm• Inner Zone defined by interference levels from neighbor

cells.• Intra-cell Handovers based on path loss between the MS and

the serving cell.• Using modified PGBT equation.• Inner zone threshold and margin are added to the decision

criteria.

RXLEV_DL_Neighbor < ZONE THRESHOLD andRXLEV_UL_Neighbor > ZONE THRESHOLDWhere the neighbor is defined as interfering neighbor

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Applications

• Cells Upgrade (Aggressive Re-Use Patterns)• Concentric cells use aggressive re-use patterns

• Interference limits effective coverage area of cells using these patterns

• Best capacity increases available from most aggressive re-use patterns

• Single site

• Two site

• Balance coverage area and capacity increase

• Optimum solution is use

• Conventional re-use pattern for Overlaying cells

• Aggressive re-use pattern to add capacity

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Applications

• Cells Upgrade (Aggressive Re-Use Patterns)– 4x3 Conventional Re-Use Pattern

• Four site repeat, three sectors/site (reuse 12)• Near complete coverage with low interference• Contiguous coverage between sites• Used to provide umbrella cells

C/I in range 9 to12 dB

C/I >17dB

C/I in range 12 to 15 dB

C/I <= 9 dB

A

BC

DF

EG

HI

JL

K


Applications

• Cells Upgrade (Aggressive Re-Use Patterns)– Single Site Concentric Re-Use Pattern

• Single site repeat, three sectors/site (reuse 3)• High repeat efficiency - four times normal• Large coverage area susceptible to “high” interference• Useful in a subset of sites where traffic concentrated near cell site


C/I >17dB


C/I <= 9 dB

X

YZ

X

YZ

X

YZ

X

YZ


Applications

• Cells Upgrade (Aggressive Re-Use Patterns)– Two Site Concentric Re-Use Pattern

• Two site repeat, three sectors/site• Twice normal repeat efficiency• Majority of deployment area with low interference• Usable in majority of sites except where traffic around site periphery


C/I >17dB


C/I <= 9 dB

X

YZ

U

VW

U

VW

X

YZ


Applications

• Cells Upgrade (Aggressive Re-Use Patterns)– Benefits

• Allows very easy frequency allocation for upgrades• Allows more tight frequency re-use for the inner zone and thus high

utilization of the frequency band• Giving more spectrum easily for new sites frequency planning• Allows offloading of high configuration sites and thus enhancing the

quality of service of high configuration sites• Reducing interference caused by high sites by allowing few radios

transmitting max power so that not to lose coverage for far traffic (overshoot), while maintaining good quality of service for near traffic.

In General Concentric Cells is very efficient for optimization work to enhance the Quality of service


DB Parameters and Statistics

• DB Parameters Overview (Power Based Algorithm)– Cell_Zone

– Rtf parameter, determines if rtf is in outer or inner zone

– Inner_zone_alg– Cell Parameter, determines the concentric cell type used

– ms_txpwr_max_inner– Cell Parameter, determines the max ms power transmitted inside the

inner zone

– Outer_zone_usage_level– Cell Parameter, determines the min level of % TCH usage in the

outer zone to allow allocation for resources in the inner zone

– Rxlev_xx_zone– Cell Parameter, act as the threshold used in qualifying MS to hand

over to or from inner zone.

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• DB Parameters Overview (Power Based Algorithm)– Trx_pwr_red

– RTF parameter, used to determine the reduction in DB’s for each dri in the inner zone

– Zone_ho_hyst– Cell Parameter, Used to prevent ping pong Handovers between

inner and outer zones

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• DB Overview– Power Based Handover Equation

– Outer to Inner Handovers Trigger

(RXLEV_DL > RXLEV_DL_ZONE + ZONE_HO_HYST + (BS_TXPWR - BS_TXPWR_MAX_INNER))

AND

(RXLEV_UL > RXLEV_UL_ZONE + ZONE_HO_HYST + (MS_TXPWR - MS_TXPWR_MAX_INNER))

AND

% of TCH used in outer zone is >= outer_zone_usage_level

Where:

BS_TXPWR_MAX_INNER = TRX maximum power capability - TRX_TXPWR_RED


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• DB Overview– Power Based Handover Equation

– Inner to Outer Handovers Trigger

[(RXLEV_DL < RXLEV_DL_ZONE AND

BS_TXPWR = BS_TXPWR_MAX_INNER]

OR

[(RXLEV_UL < RXLEV_UL_ZONE AND

MS_TXPWR = MS_TXPWR_MAX_INNER]


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• Statistics Overview– TCH_Usage: TCH usage for outer zone measurements only

– TCH_Usage_inner: TCH usage for inner zone measurements

– TCH_congestion: congested time for outer zone resources

– TCH_congestion_inner: congested time for inner zone resources

– Inner to outer zone_ho: attempts and success

– Outer to inner zone_ho: attempts and success

– Intra_zone_ho: attempt and success

– Inner_zone_TCH_assignment

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Conclusion

• C.C allows • more aggressive frequency patterns• Easy Site upgrades and Frequency Plans• More Controlled coverage over traffic distribution• Perfect re-use when traffic is existing near the cells• Offloading high configuration sites• Limiting interference of high sites and overshooting ones• Good results without major changes in site

configurations

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What’s Next ??

• Filtering out High configuration cells and high sites

• Checking IOS Rxlev Distributions for check of traffic

locations

• Working jointly with Mobilink Team to finalize a list of cells

that C.C will be applied on them

• Applying C.C on these cells to offload them and enhance the

quality of service for Karachi Network

concentric cells new

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