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OMNIAC M
OMNIAC M
TAWAPropagation and Cell
Planning
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OMNIAC M
OMNIAC M
DECT Standard :
High subscriber density
High traffic capacity
Low cost
Micro cellular deployment
Supports toll-quality voice service and high bit
rate data services
Introduction
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OMNIAC M
OMNIAC M
The sensitivity (defined as received power level at
which the Bit Error Rate is 10-3)
TAWA Enhancements
DECT Norm TAWA
FRS 83 dBm with BER=10-3 -91 dBm with BER=10-3
BS 86 dBm with BER=10-3 -91 dBm with BER=10-3
-73 dBm with BER=10-5 -86 dBm with BER=10-5
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OMNIAC M
OMNIAC M
The frequency of operation in DECT is around 1.9
GHz, at which the wavelength is only 15 cm Compact
Antenna:
Compact
High-gain
Several antennas have been specifically developed
for the TAWA system
Antennas (1)
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OMNIAC M
OMNIAC M
Sectoral antenna for FRS:
Gain: 10 dBi
Weigh: 150gm
Horizontal beam width = 80
Vertical beam width = 50
Antennas (2)
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OMNIAC M
OMNIAC MAntennas (3)
Sectoral antenna for BS and RBS:
Gain: 12,14, 16 or 18 dBi
Weigh: 300 gm
Horizontal beam width = 60
Vertical beam width = 25
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OMNIAC MOMNIAC M
Omnidirectionnal antenna for BS and RBS:
Gain 6, 9 or 11 dB
Vertical beam width = 10
Antennas (4)
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OMNIAC MOMNIAC M
-Transmit power Tx : 24 dBm
- Loss 1 m from antenna : +20log(/4) = -38
- BS antenna gain : +Gb- FRS antenna gain : +Gw
- BS and FRS cables loses : -Lc
- Propagation Loss : -Lp
- Fade margin : -Lf
Total : -14+Gb+Gw-Lc-Lp-Lf > -90 dBm(sensitivity limit for BER < 10-3)
FRS-BS Link Analysis
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OMNIAC MOMNIAC M
Path Loss:
LOS path : 6 dB loss for each doubling of distance (or20 dB every decade)
Wall / Floor : 7 dB loss for 9- 12 brick walls and 5 RCC
floorsTrees : 6-15 dB loss depending on canopy thickness
Cable Loss
BS : < 1 dB (short cable since antenna co-located with BS)
FRS : 1 5 dB (depending on cable lengthand type)
2 3 dB typical
Losses
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OMNIAC MOMNIAC M
Non-LOS links
At 2 GHz, signal fades by 20 dB in non-LOS situation due to
multi-path
With antenna diversity at BS, fade margin required is only 10
dB
no FRS installed with signal strength < -80 dBm
BER < 10-5 most of the time, occasionally dropping to
10-3
LOS Links
In LOS situations, multi-path fading is rare
5 dB margin is adequate
BER < 10-5 always
Fading
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OMNIAC MOMNIAC M
For 60 Sectors :
Antenna Gain Gb : 12 dB
Gw
: 7.5 dB
Cable Loss Lc : 3 dB (typical)
Fade Margin Lf : 10 dB (non-LOS)
Recd. Signal Strength = -14 + 12 + 7.5 - 3 - 10 - Lp
500 m propagation in free space 54 dB loss
28.5 dB margin in Lp for loss through walls / ceiling
4 walls / ceiling can be penetrated
Link Analysis Example : Roof-top Base
Station Cluster
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OMNIAC MOMNIAC M
Gb 12 dB
Gw 7.5 dB
Lc 6 dB (assume worst case cable losses of 1 + 5 dB)
Lp 80 dB (10 km)
Lf 5 dB (LOS case)
Received Signal Strength = -14 + 12 dB + 7.5 - 6 - 80 - 5
= 85.5 dBm
4.5 dB margin still available
Link Analysis Example : Long Distance BS
FRS Link at 10 km
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OMNIAC MOMNIAC M
BS
Roof-top BS cluster (macro-cell)
Street-level dispersed BS ( micro-cell) In-building multi-floor ( Pico-cell)
FRS
Integral whip antenna/indoor patch antenna
Window-mounted patch antenna
Roof-top patch antenna
Deployment Options
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OMNIAC MOMNIAC MSingle Omni Roof-top BS
Mount BS on a pole
Use 2/4/6 dBi omni antennas
vertical beam width decreases with gain
e.g. for 6 dBi antenna beam width, it is 100
shadow region in the vicinity of the BS
(where antenna has some lossinstead of gain)
shadow region increases in size with antenna height
and gain
)
Vert. beam width
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OMNIAC MOMNIAC MMultiple Omni Roof-top BS on a Pole (1)
Multiple BS can be co-located to increase capacity
1 BS with 12 channels gives 5.8 E (@ 1% GOS)
2 BS with 24 channels gives 15 E i.e 7.5 E per BS 4 BS with 48 channels gives 9 E per BS
Critical issues same as with single omni BS
In addition, spacing between antennas of different BS
should be about 50 cm
minimize parasitic effects
Suggested deployment geometries shown next, whether ontop of pole or otherwise
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OMNIAC MOMNIAC MMultiple Omni Roof-top BS on a Pole (2)
Could have a separate axially-mounted lightning interceptor (spikes) instead of industrial
antenna lightning protectors,
need to mount interceptor at a height sufficient to ensure that BS
antennas are within the protection funnel
Pole
Two OmniBS
Four Omni BS
Pole
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With Sectorised deployment, one can Increase frequency re-use by reducing interference in undesireddirections
can co-locate very large number of BSs
can deploy cell-sites every 1-2 kms to get high tele-density
Increase antenna gain at BS
easy to get 12 dB gain with compact antennas( ~ 60 cm length, < 1 kg weight)
Increase vertical beam-width despite high gain (~50)
Down tiltantenna (up to a few degrees less than
half of vertical beam width) reduce shadow region
reduce illumination above the horizon
reduce interference in neighbouring cells
Avoid shadowing due to tower/pole
Sectorised BS Cluster
Downtilt angle
Side view
)
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OMNIAC MOMNIAC MDiversity in Sectorised Deployment
45cm
45cm
45cm
Sectors illuminated by the pair ofdiversity antennas for each BS must beidentical
Diversity antennas can bemounted
a) side by side
b) one below the other
c) diagonally across
Antenna spacing in all cases atleast 45 cm
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OMNIAC MOMNIAC MNumber of Sectors
With 7.5 dB antennas, typical horizontal beam width =80- 90
4 to 5 sectors
With 12 dB antennas, horizontal beam width is 60
6 sectors
Each BS gives 5.8 E per sector @ 1% GOS
4-sectors
BS antennapair
) 60
6-sector
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