DEVELOPMENT OF A SOFTWARE TOOL FOR PLANNING MICROWAVE SYSTEMS AT ABOVE 10 GHz, ESTIMATING CO-CHANNEL INTERFERENCE AND RAIN ATTENUAITON, USING ITU-MODEL ON MATLAB AND TO VALIDATE THE SOFTWARE AGAINST AN INDUSTRY STANDARD (CONNECT) TOOL”

1. “DEVELOPMENT OF A SOFTWARE TOOL FOR PLANNING MICROWAVE
SYSTEMS AT ABOVE 10 GHz, ESTIMATING CO-CHANNEL
INTERFERENCE AND RAIN ATTENUAITON, USING ITU-MODEL ON
MATLAB AND TO VALIDATE THE SOFTWARE AGAINST AN INDUSTRY
STANDARD (CONNECT) TOOL”
Presented by:
SHIV DUTT
RF Lead Engineer
Vedang Radio Technology
Mumbai, India

2. Microwave CommunicationMicrowave Communication
Atmospheric Loss
FSL
Tx/Rx
(IDU)
Tx/Rx
(IDU)
ODU ODU
Branching Loss
Branching Loss
- Lr
- Lt
PrPt
+ Gr
+ Gt

3. Pr(dBm) = Pt(dBm) + Gt (dBi) + Gr (dBi) – Net Path
Loss(dB)
Where
Pr =power received ;
Pt = Transmissted Power;
Gt = Tx Ant Gain;
Gr = Rx Ant Gain;
Signal strength received at Receiver is given by
Friis Transmission Equation

4. The plot of power received versus free space loss is drawn
from calculated result on Matlab . Which is showing power
received level decreases with varying FSL and increases
with varying transmit power.

5. FSL (dB) = 92.45 + 20*LOG(f) + 20*LOG(D)
Where, f : Frequency of Operation, in GHz
D: Hop length, in Km
Net Path Loss = FSL + Aa + Lt + Lr + Lb + Lo
Where, Aa = attenuation due to atmospheric gases,
Lt & Lr = feeder loss in dB
Lb = branching loss in dB (circulators, filters)
Lo = other loss in dB (e.g. attenuators , degradation of threshold)

6. Free space loss increases
sharply with Distance less
then 10 km, but it increases
slowly with distance greater
than 10 km.
Free space loss increases
wiht frequency and distance
both.

7. Radio link

8. Fade margin (dB)
Fade Margin (dB)= Pr (dBm)-Pth(dBm)
Where
Pr : power received
Pth: threshold of receiver =-83dBm, ITU standard
Fade margin is the difference between the unfaded receive
signal level and the receiver sensitivity threshold.
Fade margin is the insurance against unexpected system
outages.
The percentage of time that the link is available increases as
the fade margin increases

9. Fade margin also called System Operating Margin

10. Types of fade margin
Flat fade margin
Interference fade margin
Rain fading
Refrection – diffraction fading
Dispersive fade margin
Composite fade margin

11. Interference
Interference in microwave systems is caused by the
presence of an undesired signal in a receiver. When
this undesired signal exceeds certain limiting values,
the quality of the desired received signal is affected. To
maintain reliable service, the ratio of the desired
received signal to the (undesired) interfering signal
should always be larger than the threshold value.

12. Co-channel interference
A company has been subscribed a particular frequency band of
total spectrum by the IT government. When number of
customers increases, this band becomes limited. Then
company works under a stretagy that is reuse of frequency
band. When same frequency is repeated for different links
within small region. This can be done upto a certain limit and
beyond this limitation links would make a interference to each
other

13. Desired link Rx
Undesired link Tx
Link2 at18 GHz
Link1 at 18 GHz
Co-channel interference

14. Importants facts
• Arrangements of lat/long data in left-to-right
standard format
• Determine distance angle of each link
• Calculate north bearing angle of each site of
link
• Interference angle
• Gain at intereference angle

15. Lat/long arrangement
Figure: left-to-right arrangement of lat/long.

16. Δx, Δy and θ in geometry view
( )
( )12
12
21
*
*
2
cos*
θθ
θθ
−=∆
Φ−Φ




 +
=∆
Ry
Rx
R= 6378 km, radius of earth
22
yxD ∆+∆=

17. Distance angle






∆
∆
= −
x
y1
tanθ
If latitude angle is less than other latitude angle then use following logic:
Bearing angle of ‘X’: 900
- 400
= 500
Bearing angle of ‘Y’: 2700
– 400
=2300
If latitude angle is greater than other latitude angle then use following logic:
Bearing angle of ‘X’: 900
+ 300
=1200
Bearing angle of ‘Z’: 2700
+ 300
=3000

18. ‘X’ is aligned with ‘Y’ because the difference of angles
with respect to north is 1800
:
2300
- 500
= 1800
And now ‘X’ is also aligned with ‘Z’ in similar manners:
3000
– 1200
=1800
North bearing Angle

19. Here is a practical result of north bearing angles that is
calculated on Matlab:
bearing angle =
NaN 130.8148 125.1292 119.3291 111.8986
310.8148 NaN 116.4396 110.4509 104.1879
305.1292 296.4396 NaN 104.3306 99.7064
299.3291 290.4509 284.3306 NaN 97.1108
291.8986 284.1879 279.7064 277.1108 NaN

20. Interference angle
Suppose N- number of nodes or stations
N2
– number of all possible links in Mesh geometry,
N links are self to self Which is not accounted?
Thus N (N-1)/2- number of links in one direction
N (N-1) - number of all possible links in both directions (duplex)
N2
– number of interference angle matrix having N2
element
diagonal elements are not significant, N self to self matrices
are not accounted.
Each node has N receiver

21. Interference angle from each link when N12
is desired link.

23. Gain at interference angle

24. Interference power calculation
I = PT
+ GRD + GCD - FSL- LCT
-LCR
Where,
I : is the received interfering carrier power.
PT
: is the transmit power from the interfering station in dBm.
GT
: is the antenna gain of the interfering transmit station in dB.
GRD : is the antenna gain of the desired receive station in dB measured
at the angle of arrival of the interfering signal.
GCD : is the combined angular discrimination of the two antennas at their
respective discrimination angles.
FSL: is the free space loss of the interfering path in dB.
LCT
: is the cable loss of the interfering transmit station.
LCR
: is the loss of the waveguide of the desired receive station.

25. Rotation of undesired Tx toward desired Rx

26. Ex. Interference power for link NEx. Interference power for link N1-21-2
I1-2
=PT(1-1,1-2.........2-1,2-2........,3-1,3-2.........)
+GRD(1-1,1-2.........2-1,2-2........,3-1,3-2.........)
+
GCD(1-1,1-2.........2-1,2-2........,3-1,3-2.........)
- FSL(1-1,1-2.........2-1,2-2........,3-1,3-2.........)
-
LCT (1-1,1-2.........2-1,2-2........,3-1,3-2.........)
- LCR (1-1,1-2, .........2-1,2-2........,3-1,3-2.........)
FSL : freespace loss will be involved such FSL(desired Rx node, Undesired Tx node)
LCT and LCR are also in same manners
idbm =
NaN -23.3506 -27.5823 -30.3440 -33.7818
-24.7931 NaN -19.6899 -25.4579 -30.8555
-29.0062 -21.1229 NaN -19.4801 -27.8931
-31.7623 -26.8673 -20.9170 NaN -24.4599
-35.1903 -32.2283 -29.1867 -25.7525 NaN
Calculated result

27. Comparission with standard connect tool

28. Site IDs are represented
By blue dots, which
does not have tarrain
map like connect.

31. Plot of interference power matrix
for all possible links
Plot of interference power matrix
when some links are masked

36. Rain Attenuation
•Rain attenuation is a major constraint in microwave radio
link design above 10 GHz.
•Several empirical and non-empirical rain attenuation
prediction models that have been developed are based on
the measured data obtained from temperate regions.
•Most of these existing rain attenuation prediction models do
not appear to perform well in high rainfall regions.
•The ITU-R [4] model is currently being widely used by many
researchers.
•Other impairments are due to gaseous absorption, cloud,
tropospheric refractive effects, scintillation, wet antenna etc.

37. Specific Attenuaiton
γR= k.Rα
dB/km
Where
R=rain rate in mm/hr
k=[kH+ kV+(kH- kV)cos2
θ.cos2τ]/2
α=[ kH.αH+ kV.αV+(kH.αH- kV.αV)cos2
θ.cos2τ]/2k
• where θ is the path elevation angle
• and τ is the polarization tilt angle relative to the
horizontal (τ=45o
for circular polarization,0o
for
horizontal polarization and 90o
for vertical
polarization)

38. freq(GHz) kH kV αH αV
1 3.87E-05 3.52E-05 0.9116 0.8802
2 0.000154 0.000138 0.9632 0.9234
4 0.00065 0.000591 1.121 1.075
6 0.00175 0.00155 1.308 1.265
7 0.00301 0.00265 1.332 1.312
8 0.00454 0.00395 1.327 1.31
10 0.0101 0.00887 1.276 1.264
12 0.0188 0.0168 1.217 1.2
15 0.0367 0.0335 1.154 1.128
20 0.0751 0.0691 1.099 1.065
25 0.124 0.113 1.061 1.03
30 0.187 0.167 1.021 1
TABLE: regression coefficients for estimating specific attenuations

39. Ap = 0.12(A0.01).p[-(0.546+0.043logp)]
dB
Where
• Ap is the attenuation (dB), exceeded for p percent of the time.
• A0.01 = γR.r.d (dB) for 0.01 percent of the time
• It depends on the model assumed for the spatial structure of
rainfall and is computed by multiplying the actual path length
d by a reduction factor r
r=(1+0.045d)-1
Total rain attenuation

40. Results
When elevation angle is
choosen zero degree

41. Rain Zone codes
The International Telecommunication Union (ITU) has created a statistical
model in which the Earth is divided into different “rain zones,” where each
zone corresponds to a certain level of rain rate.

42. • Signal with Vertical polarization is far less susceptible to
rainfall attenuation (almost 40 to 60%) than horizontal
polarization.
• Radios with Automatic Transmitter Power Control have been
used in highly vulnerable links. Automatic Transmitter
Power Control is one of the parameters of radio, which
allows a control over the power level of the transmitted
signal within the limits defined by the vendor.
• Wet radome loss effects can also be reduced by employing
shrouded antennas.
Factors leads to reduction in Rain AttenuationFactors leads to reduction in Rain Attenuation

43. REFRENCES
Microwave Radio Transmission Design Guide.……….by Trevor Manning
Transmission Systems Design for Wireless Networks....... ......by Harvey Lehpamer.
Data communnication ……………………………..………...by Behrouz A. Forouzan
Digital line of sight …………………………………………..by A. A. R. Townsend
Wireless communication …………………………………..…by Lin
ITU –T recommendation sheets
Planning a Microwave Radio Link....................... By Michael F. Young
Microwave Transmission With Digital Applications by Harris Farinon
Paper on ‘Simulation of flat fading using MATLAB for classroom Instruction’
by G. S. Prabhu, P. Mnhana
Research paper by Mehrbod Mohajer, Ramin Khosravi, Mehrnoosh Khabiri
International Telecommunications Union (ITU-R),
“Propagation data and prediction method required for the design of
terrestrial line-of-sight systems”.
www.nsma.org
indiastudychannel.com
www.electronic-tutorials.com
www.radio-electronic.com