A presentation on RF survey, showing how survey of a cell site is done, how a microwave link is established, and how to perform the LOS survey for clearing the obstacles in between the links
2. Sharing site survey
New site survey
i) Sharing site survey:-
-coverage capacity
ii) New site survey:-
- GBT, RBT, RTP
- Nominal point
- Range (100-200m)
- Site options
3. Survey of land
-size
-tools
compass, GPS, measuring tape, camera,
binoculars, ultimeter, inclinometer, maps, 10 or 50
meter tape measure, Site survey document
Deviation P1 r
known as side shift. 0 P3
P2
4. Coordinates
latitude and longitude
AMSL
Complete Address of proposed site
Accessibility
- nearest city, highway, railway
station, airport
5.
6. Tower height
GSM height
Orientation
BTS (indoor/outdoor)
Wiring distance
Hop length
Shelter
Layout of proposed site
13. Para photos
- 12 photos
- at every 30 degrees
30º 270º
330º
14. Line of sight survey
Connectivity of two sites
Clearing links
carried out physically checking the terrain
between the hop
and selecting the sites for acquisition.
15. Collect Nominals of proposed site and those of the nearest
locations to which customer proposes the LOS connectivity &
Verification
Record latitude, longitude, building data, obstruction data
and surrounding terrain data on the LOS Survey template.
Generate LOS Path Profile for the proposed Link using Path
Loss 4.0
Generate LOS report for the proposed Link using Path Loss
4.0.Conduct physical survey of the hop to identify any field
obstructions and verify the LOS path profile
16.
17. Microwave Links
Basics
The preferred media when building new
access network links
High capacity transmission links
from 2x2Mbps to 16x2Mbps, 34Mbps
Pros: Cons:
low operating costs needs frequency license
easy to install environment dependant
flexible link quality (e.g. rainfall)
quick & reliable solution LOS not always available
Repeater
station
Terminal Terminal
station A station B
18. Microwave Links
Types of MW
• Long Haul Radios: ~ 30 - 80 km
2 GHz, 7 GHz
• Medium Haul Radios: ~ 25 - 45 km
10 GHz, 13 GHz, 15 GHz
• Short Haul Radios: ~ 5 - 30 km
18 GHz, 23 GHz, 26 GHz, 38 GHz,
• Nokia Metrohopper: < 1 km
57 GHz
(uses oxygen absorption in air to
limit range)
19. Microwave Links
Radio Link Availability
• Microwave outages
– equipment failures
• use protected equipment
– caused by nature
• temporary failures
• self-recovery
• use protected connections
• Examples of natural outages:
– heavy rainfall zones:
• most severe in upper bands (2..3dB/km)
• significant above 10 GHz
– multipath fading
• problem with lower bands
20. Microwave Links
How to Avoid Interference
• Use the highest available frequency band
• Attenuate the Tx power to a minimum just
to meet the required availability
• Locate dishes as low as possible with
maintaining the required LOS
• Use big dishes
• Use different polarisation
• Select your channel(s) carefully
• Maintain High-Low -rule on hub sites
• Try to get similar received signal levels at
hub sites
21. Microwave Links
LOS Check
LOS Methods
Balloon method
Mirror reflection method
Using binoculars
Route track method
22. Microwave Links
Fresnel Zone
• Line-of-sight path needed between both nodes of
a microwave link
• Keep 1st Fresnel zone clear of obstacles
• nth Fresnel zone: Ellipse around direct path, where
path difference to direct line is n* /2.
1st Fresnel zone
2nd
3rd
d
b
d [km]
b 274 [ m]
f [ MHz ] Radius for n-th zone = b * sqrt(n)
23. Curvature of earth
= (d1*d2)/(12.75* k)
where k=(eff. Earth radius/true earth radius)
RF effect of fresnel zone
fresnel zone= 17.32*[√{(d1*d2)/(D*f)}]
Path loss
Transmitted and received power
Transmission line losses
Frequency of operation
Antenna gain
gain= {17.8+20log(D.f)}
24. Earth bulge
Antenna Height = Earth Buldge + Maximum Obstacle Height+ Fresnel Zone
25. To establish links
Feasibility of studies
Upgradation of existing links