Cell Cluster Rev Jan2011

8/3/2019 Cell Cluster Rev Jan2011

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How to create more COV & CAP

Cell Splitting

Cell Splitting - The process of creating more coverage andcapacity in a wireless system by having

more than one cell site cover a particular amount ofgeography.

Each cell site covers a smaller area, with lower power and

thus offers the ability to reuse frequencies moretimes in a larger geographic coverage area, such as a city.


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CELL Splitting


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CELL Sectoring


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Cell Size

The size of a cell is influenced by several factors.

O/P Power of BTSA = P

Small A+ Low P

Pico cell .. Low P

Geography of the Cell Site

Hilly or Plain

DU, U, SU or Rural

Ant. Characteristics

Gain, Ht., O or S,

S60 or S120, Tilt,

Orientation

1

3

2


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Most common Cluster

configurations are :

7 cell cluster

(7 Omnidirectional

cells in

one cluster)

21 cell cluster

(7 base stations sites, each with

3 sector cells ).


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Maximum Coverage & Frequency Reuse

For an operator to obtain maximum coverage,

frequencies must be REUSED.

Thus Various cells can be combined properly to form

the overall network.

Cellular Structure is like Honey Comb Configuration


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What is Cell Splitting

is the process of creating more coverage andcapacity in a wireless system.

This is done by having more than one cell sitecover a particular amount of geography.

Each cell site covers a smaller Area, with lowerTx. P , lower Ant. Ht.

This config offers the ability to reuse frequenciesmore times in a larger Cov. Area (geographic

coverage areas), such as a city. This in turn puts lower load on users Bty. and

hence longer Bty. Life.


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Cellular Network and Frequency Reuse

Frequency reuse is the process that allows formany phones to operate in a given area.

There is a set frequency band that limits the

number of cellular phones that can use any givencommunication tower.

This is why handshaking is needed to allow for

the user to move between the towers.

An example of how the separate cells are

organized in a given area for frequency reuse is

shown .


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? Cell cluster


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Frequency Reuse

Frequency Reuse is the core concept of cellularmobile radio

Users in different geographical areas (in differentcells) may simultaneously use the same frequency

Frequency reuse drastically increases user capacityand spectrum efficiency

But Frequency reuse causes mutual interference (Hence trade off link quality versus subscriber

capacity)


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Frequency Reuse


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Geometry of a Hexagon

Surface area is 6 R^2times ( sq root 3)/4


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Why is the GSM 900 better than GSM 1800 and GSM 1900?

As the frequency increases its penetration power decreases.

The signal travels a lesser distance. Hence for a particular area more no of towers need to be erected in 1800/1900 than in

900MHZ for full coverage...

Hence Co A (1800MHZ) has more towers per unit area than Co B (900MHz) .....

Band of 900 is from 890-915( uplink) 935-960Mhz( downlink)....Band of 1800 is from 1710-1785(uplink) and 1805-1880MHZ(Downlink)....

.The uplink is lower ( MS -BTS) than the downlink frequency (BTS-MS)...

This may help the uplink signal to travel further without consuming much power...

BTS due to its increased power ,has higher frequency to travel the same distance....


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GSM 900 2W vs GSM 1800 1W

Apart from the radio propagation characteristics the onlyother difference is the maximum output power

which is defined in the standards forGSM900 versusGSM1800.

A GSM900 handset can have a Max. output power of 2WA GSM1800 handset can have a Max. output power of 1W


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cellular COW , or a site on wheels (SOW) ormobile tower unit(MTU)

COWs are used to provide expanded cellular networkcoverage and/or capacity at special events such as major

sporting events , majorconventions, or in disasterareas

where cellular coverage is not present .

Following the 9/11 attacks on New York City, 36cellular COWs were deployed . for the inaugural ceremony ofBarack Obama inJan 09 to handle the millions

ofextra people and calls in the city


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cell site

A cell site is where antennas and electronic comm. eqpt

are placed to create a cell in a cellular network.A cell site is composed of

a tower or an elevated structure for mounting antennas,

one or more sets of Tx/Rx transceivers,

Digital signal processors,

control electronics, a GPS receiver for timing ,

Normal & S/B Power sources, and

sheltering.


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Why Hexagonal Shaped Cells?

Fictitious Ideal Real

The hexagonal shaped cells are artificial and cannot begenerated in the real world.Engineers draw these shaped cells because they approach the

circular shape but get rid of the ambiguity and unclarityproduced from the overlap between the cells.Hexagonal shaped cells fit in a planned area nicely and haveno gaps or overlaps between them.


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The Cellular concept

The concept ofcellular radio can be used toexplain the diffening receptions at various

locations. An area to be supplied with radio service is

divided into cells.

Each of these cells is assigned a range offrequencies (f1 - f6) and they each havecorresponding radio base stations.


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The Cellular concept

The group of frequencies can be reused in other

cells bearing in mind that it is not reused in

adjacent cells as that will cause co-channelinterference (CCI).

Co-channel interference results when frequencies

are reused in adjacent neighbouring cells. A reuse

distance,D is calculated as


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where R is the cell radius andNis the number of cells

per cluster.

Cells may vary in radius in the ranges (1 km to 30 km).

The shape of the cells can be hexagonal, circular or

some other undefined irregular shapes.

The boundaries of the cells can also overlapbetweenadjacent cells.


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This provides a minimum of 3CHLs for each cell. Thenumbers are channel numbers,Large cells can be subdivided

into smaller cells for highvolume areas.

Cellular telephonefrequency reusepattern.


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COW


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Cell onW

heels (COW

) A cell on wheels, usually referred to as a

COW, is a mobile cell site that consists of a

cellularantenna towerand electronic radiotransceiverequipment on a truckortrailer,

designed to be part of a cellular network.


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CIAB (Cell-in-a-Box)


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Sharing Resources, Cell Site, BTS, BS Site

Many cell site antennas are mounted on buildings

rather than on towers.

In GSM networks, the technically correct term isBase Transceiver Station (BTS), or "base station".

The term "base station site" might better reflect

the increasing co-location of multiple mobile

operators, and therefore multiple base stations, at asingle site.


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multiple base stations at a Site Depending on an operator's technology,

even a site hosting just a single mobile

operator may house multiple base stations,each to serve a different air interface

technology (CDMA orGSM,).


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Cellular frequencies All cellular phone networks worldwide use a portion of

the radio frequency spectrum designated as Ultra High

Frequency, or "UHF", for the transmission andreception of their signals.

The UHFband is also shared with TV, Wi-Fi and

Bluetooth transmission.

The cellular frequencies are the sets of frequency

ranges within the UHFband that have been allocated

forcellular phone use


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Ultra high frequency (UHF) Ultra high frequency (UHF) designates a range of

electromagnetic waves with frequenciesbetween

300 MHz and 3 GHz (3,000 MHz),

also known as the decimetre band ordecimetre wave as thewavelengths range from one to ten decimetres (10 cm to 1metre)., (1m to 100mm)

Radio waves with frequencies above the UHF band fall into the

SHF (super high frequency) and EHF (extremely highfrequency) bands, all of which fall into the microwave frequencyrange. Lower frequency signals fall into the VHF (very highfrequency) or lower bands.

Cell Cluster Rev Jan2011

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