2. APPLICATIONS:
• Fixed Radio Communication Services.
• Fixed Satellite Services.
• Mobile Services.
• Broadcasting Services.
• Radio Navigation Services.
• Meteorological Services.
• Radio Astronomy Services.

3. • M/W systems used to provide communication on
major trunk routes with high traffic density and
serving long distances are classified as long haul
M/W systems. 2, 4, and 6 GHz systems are long haul
systems.
• Systems used to provide communication over short
distances for trunk routes with light traffic density
are classified as short haul system. 7 and 11 GHz
systems are short haul systems.

4. RANGE NAME WAVELENGTH USES
0–30 KHz V.L.F. Up to 10 km. Used for long communication. Has limited
information. Bandwidth require very high
power.
30–300 KHz L.F. 10 km to 1 km
0.3–3 MHz M.F. 1 km to 100 m Radio Broadcast, Marine Power in KW,
ground wave propagation, i.e. follows the
curvature of the Earth.
3–30 MHz H.F. 100 m to 10 m Long haul point to point communication.
Propagation is by one or more reflections
from ionosphere layers and so subject to
variations.
30–300 MHz V.H.F. 10 m to 1 m Line of sight, Tropo-scatter
communication.
0.3–3 GHz U.H.F. 1 m to 10 cm. –––––– do ––––––
3–30 GHz S.H.F. 10 cm to 1 cm. Line of sight, terrestrial M/W and Satellite
communication.
30–300 GHz E.H.F. 1 cm to 1 mm. Experimental.

5. WPC
• In this regard (in the national context) the wireless
planning and co–ordination wing (WPC) of the
ministry of communication has allotted m/w
frequencies spectrum, on the basis of various
wireless users classified as general users and major
users. Wireless users who are permitted to plan
their services and take action for the development
of the required equipment's are major users. BSNL
has been nominated as a major wireless user by the
WPC in 1981 in the following sub base band of the
M/W spectrum for fixed radio communication.
Microwave Spectrum Available for BSNL.

6. CCIR
The CCIR recommends 2 GHz band for 60,120, 300 and 600-
1800 channel systems, 6 GHz for 1800 channel system
upper 6 GHz band for 960 to 2700 channel system, and 7
GHz band for 60, 120 and 300 channel systems. Taking into
account various factors the following gives some of the
trends of frequency usage in India.
1. Long-haul wideband systems-4 GHz and 6 GHz
2. Narrowband Long-haul system -2 GHz
3. Narrowband short haul systems -7 GHz and 13 GHz.
4. Wideband short haul systems -11 and 12 GHz.
Besides this digital microwave systems are proposed to be used
in the band 2GHz and 13 GHz which is also recommended
for digital transmission by CCIR.

7. Nomenclature Bit rate No. of Frequency band
chls.
Small capacity 0.704 10 658–712 MHz (UHF)
Small capacity 2.048 30 400 MHz band (UHF)
520–585 MHz (UHF)
Small capacity 8.448 120
622–712 MHz (UHF)
Small capacity 8.448 120 2 GHz band (M/W)(2.0–2.3 GHz)
7 GHz band (M/W)
Medium capacity 34.368 480
(7.425–7.725 GHz)
13 GHz band (M/W)
Medium capacity 34.368 480
[12.75–13.25 GHz band (M/W)]
4 GHz band (M/W)
High capacity 139.264 1920
(3.3–3.8 and 3.8–4.2 GHz)
6 GHz band (M/W)
High capacity 139.264 1920 (5.925–6.425 GHz : Lower)
(6.430–7.110 GHz : Upper)
11 GHz band (M/W)
High capacity 139.264 1920
(10.7–11.7 GHz)

8. RF channel arrangement
Let us look at a typical RF channel arrangement for a 6
GHz band 5925 to 6425 MHz). This band of 500 MHz
is designed for 1800 channel capacity system with 8
pairs of frequencies. The individual channel
frequencies are given by
Fn = Fc - 259.45 + 29.65 n
Fn' = Fc-7.41 + 29.65 n
Where Fo = Centre freq. of band= 6175 MHz.
Fn and Fn’ are centre frequencies of nth channel in
lower and upper half .

9. Digital system route
The RF channel occupy 6430–
7110 MHz, accommodating 8
both way RF channels with 40
MHz spacing between adjacent
RF channels.
The radio frequency channels
assignment for Bombay Panjim
route is shown in Fig.3 as an
example. Polarization employed
(V/H) at various stations is also
depicted in the figure.

10. Lower half band Upper half band
RF CH No. Radio frequency (MHz) RF CH No. Radiofrequency (MHz)
1 6460 1' 6800
2 6500 2' 6840
3 6540 3' 6880
4 6580 4' 6920
5 6620 5' 6960
6 6660 6' 7000
7 6700 7' 7040
8 6740 8' 7080

11. CCIR
Frequency band
The CCIR Upper 6 GHz frequency plan as shown
in Fig.2(a) and 2(b) is employed in these
systems.
fo : 6770 MHz
Lower half of band : fn = fo–350+40n
Upper half of band : fn' = fo–10+40n
n = 1, 2, 3, 4, 5, 6, 7 or 8

12. SACFA
• The main objective of the function of
the SACFA Board is to investigate the
interference possibilities, etc. and allot
the frequency and spectrum for new
routes. All types of Microwave routes
should be cleared by this body as far as
the frequency to be used, the location,
the height of tower are concerned.

13. A Microwave Terminal

14. BLOCK DIAGRAM

15. MICROWAVE ROUTE
BRANCHING RF IF RF RF IF RF BRANCHING
RF
RF
IF TERMINAL IF
REPEATER REPEATER
MOD STATION DEMOD
TERMINAL
BB IN BB OUT

16. Digital System
• 1 x 10–7 BER for more than 1% of any
month.
• 1 x 10–3 BER for more than 0.5% of any
month.
• HRDP (2500 kms), but greater than 280 kms
• 1 x 10–7 BER for more than (L/2500) x 1% of
any month.
• 1 x 10–3 BER for more than (L/2500) x
0.05% of any month

17. Link is less than 250 kms
• 1 x 10–7 BER for more than (280/2500) x 1% of any month.
• 1 x 10–3 BER for more than (280/2500) x 0.05% of any
month.
• This takes into account fading, interference and all other
sources of performance degradation. It does not include
BER greater than 1 x 10–3 for periods exceeding 10
consecutive seconds. This condition is included in the
availability criterion. The high BERs caused by switching
operations are included in the above criterion, but not the
ones caused by scheduled switching for maintenance).
Availability criterion is 1 x 10–3 BER (measured for 10s
time interval) not exceeding 0.3% of a year.

18. Switching Criteria and Switching
Priority
• The switching is initiated by the detection of
transmission quality degradation or manual
control.
• The automatic switching criteria are as follows :
• Bit error rate degradation.
1. Initiation : BER = 1 x 10–4 (1 x 10–4 to 1 x 10–9)
2. Restoration : BER = 1 x 10–6 (1 x 10–4 to 1 x 10–9)
3. Threshold setting can be made on site.
• Loss of frame alignment.
• Mismatch of route identification.
• Loss of data stream.

19. Switching
• Case A
• Forced switching
• Automatic switching
• Manual switching
• Occasional switching
• Case B
• Forced switching
• Automatic switching
• Manual switching
• Occasional switching

20. SATELLITE COMMUNICATION

21. Satellite

22. Satellites
• The basic component of a communications
satellite is a receiver-transmitter combination
called a transponder.
• A satellite stays in orbit because the
gravitational pull of the earth is balanced by
the centripetal force of the revolving satellite.
Satellite orbits about the earth are either
circular or elliptical.

24. Satellite orbits
SKG

25. SKG
Satellite orbit altitudes
23 Hrs 56 Min 4 Sec
2000

26. Orbits of Different Satellites
LEO (Iridium) GEO (Inmarsat)
Earth
10,000 km
MEO (Intermediate
Circular Orbit )
15,000 km
MEO
35,768 km
Not drawn to scale

27. SKG Satellite categories
categories Orbit speed Rotation time Application
Low Earth 0 - 2,000 km 17,000 90 minutes Mobile Satellite Services (MSS)
Orbit (LEO) miles per Globalstar, Iridium satellite
hour
27,400 k
m/h
Medium 2,000 - Global Positioning System
Earth Orbit 35,760km T=201 (GPS) 20,200 km
(MEO) R=11400 km minutes
Geosynchron 35,786 km 23 hrs, 56 Telecommunications
ous Orbit (22,240 mins, 4.09 Radio and Television
(GEO) miles). secs Boradcasting
Meteorology
Highly
Elliptical Orbit
(HEO)
So, an object placed at the orbit approx. 36 000 km above the
equator will be seen at the same position in the sky from Earth.

28. Important Satellite Classifications
• GEO (Geostationary Earth Orbit) satellites orbit about
36,000 km above Earth’s surface.
• LEO (Low Earth Orbit) satellites are about 500-2500 km
above earth’s surface.
• MEO (Medium EO) satellites are about 6000-20,000 km
above earth’s surface.
• There are also HEO (Highly Elliptical Orbit) satellites.

29. Satellites in geosynchronous orbit
GEO systems are less
complicated to maintain
because fixed location
requires relatively little
tracking capability at
ground.
High orbital altitude allows Single satellite
GEOs to remain in orbit
longer than systems
gives more than
operating closer to earth. 40% Coverage.

31. Hardware: ground segment
• Antenna
• Receiving/transmitting chain
• Types of connection
• Link budget
August 26, 2001 31

32. CHOICE OF FREQUENCY
Band DOWN LINK UP LINK BANDWIDTH
“C” BAND 5.925 to 3.7 to 4.2 GHz 500 MHz
6.425GHz
Extended “C” 5.85 to 5.9 GHz 3.4 to 3.7GHz
Band
6.425 to 4.5 to 4.8 GHz
7.025GHz
“Ku” Band 12.75 to 13.25 500 MHz
GHz
14.00 to 14.5 10.7 to 11.7 GHz 500 MHz
GHz
“Ka” Band 27.00 to 30.00 18.10 to
GHz 20.20GHz

33. Frequency Bands For Satellite
Communication
• C- Band :
• U/L : 5.925 – 6.425 GHz.
• D/L : 3.7 – 4.2 G Hz.
• Total 500 M Hz BW.
• Extended C- Band :
• U/L : 6.725 – 7.025 GHz.
• D/L : 4.5 – 4.8 G Hz.
• Additional 300 MHz BW.
• Ku band :
• U/L : 14.0 - 14.5 G Hz.
• D/L : 10.95 – 11.2 and 11.45 - 11.7 GHz.
• A total of 500 MHz BW in Ku band.

34. RF Channels
UPLINK FREQUENCY BAND 5925-6425 MHz.
Receive by satellite and modulated with 2225 MHz
before retransmitted to earth station.
DOWNLINK FREQUENCY BAND 3700-4200
MHz.
BEACON SIGNAL IN THE
4 MHZ
DOWNLINK FREQUENCY BAND
36 MHZ
1 2 3 4 5 6 7 8 9 10 11 12
500 MHz

35. Transponder
• Some satellites have (hundreds of) transponders for
communication purposes.
• A transponder
1) receives transmissions from earth (uplink);
2) changes signal frequency;
3) amplifies the signal; and
4) transmits the signal to earth (downlink).

36. Satellite Subsystems
• The main subsystems in a satellite are
– communications;
– power;
– telemetry; tracking, and control (TTC);
– propulsion;
– attitude stabilization; and
– antenna subsystems.
• Power subsystem consists of solar panels, batteries, dc-
to-dc converters, and regulators. Solar panels convert
sunlight into power to operate all satellite electronics
and to charge batteries (used when sunlight is blocked).

37. Satellite Subsystems (Cont’d)
• The TTC subsystem contains a receiver that picks up
commands from a ground station and translates them
into control signals that initiate some action on board.
• The telemetry system monitors physical conditions within
the satellites and converts them into electrical signals
that are transmitted back to earth.

38. Ground Stations: The Other End
• Satellites in space communicate (transmit/receive radio
waves) with ground stations.
• Ground stations consist of subsystems:
– transmit/receive;
– Power;
– Antenna;
– TTC; and
– ground control equipment (GCE).

39. Satellite Dish
• Ground stations feature large parabolic dish
antennas with high gain and directivity for
receiving the weak satellite signal.
Satellite signals
The larger the dish is
the higher the received
signal power.

40. Remote Communication is
economic reliable through a
GEO stationary satellite which
act as a repeater.

41. Using inexpensive receive-
only satellite dishes, the
university stores the updated
material on a server inside
the LAN…
 Internet LAN 

42. Wide coverage:-Area irrespective of intervening terrain using
a single satellite. Satellite media is the only alternative for
remote areas inaccessible through terrestrial routes.

43. REMOTE
COMMUNICATION

44. •Suitable for both Digital and Analog
Transmission
Same satellite can be used for both digital and
analog communication links. Satellite is
transparent to the type of service being
provided.
•High Quality
Satellite links are designed for high quality of
performance. The links are free from
atmospheric disturbances and fading. As only
one repeater is involved, the reliability is very
high.
•Flexibility
A satellite can be accessed from any point on
the earth from where it is visible. The earth
stations can be relocated and reconfigured
providing complete flexibility of operation
and utilisation of the satellite capacity.
•Quick Provision of Services
Compared to the conventional links, earth
stations can be installed in much shorter
period and, therefore, services can become
available faster.

45. • Mobile and Emergency Communication
An earth station can be mounted on a vehicle to
provide mobile communication services. Using
small airlift able earth station terminals,
telecommunication services can be extended to
any location in emergency.
August 26, 2001 45