CELL SECTORINGPREPARED BY: MUHAMMAD TALHA ISLAM

SECTION C2010-TE-054

TELECOMMUNICATION ENGINEERING DEPARTMENT

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Sectoringcell splitting keeps D / R unchanged

(same cluster size and CCI) but increases frequency reuse/area

alternate way to ↑ capacity is to _____ CCI (increase S / I ratio)

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replace omni-directional antennas at base station with several directional antennas3 sectors → 3 120° antennas6 sectors → 6 60° antennas

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cell channels broken down into sectored groups

CCI reduced because only some of neighboring co-channel cells radiate energy in direction of main cell

center cell labeled "5" has all co-channel cells illustrated

only 2 co-channel cells will interfere if all are using 120° sectoring

only 1 co-channel cell would interfere when using 60° sectoring

If the S/I was 17 dB for N = 7 and n = 4, what is the S / I now with 120° sectoring? 24.2 dB

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How is capacity increased?sectoring only improves S/I which increases voice

quality, beyond what is really necessaryby reducing CCI, the cell system designer can choose

smaller cluster size (N ↓) for acceptable voice qualitysmaller N → greater frequency reuse → larger system

capacity

What would the system capacity, Cnew, now be when 120° using sectoring, as compared to the old capacity, Cold ?

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Example

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SOLUTION

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PROS AND CONSmuch less costly than cell splitting

only require more antennas @ base station vs. multiple new base stations for cell splitting

primary disadvantage is that the available channels in a cell are subdivided into sectored groupstrunked channel pool ↓, therefore trunking

efficiency ↓There are more channels per cell, because of

smaller cluster sizes, but those channels are broken into sectors.

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other disadvantages:must design network coverage with sectoring

decided in advancecan’t effectively use sectoring to increase

capacity after setting cluster size Ncan’t be used to gradually expand capacity as

traffic ↑ like cell splittingMore HandoffsMore antenna, more cost

JAZAKALLAH