Let's see the comparison between C- Band and Ku-Band.........which are the most important frequency bands used for satellite communication.............
C-Band
Although the equipment required for C-band is in inexpensive than Ku-band,less number of satellites in the C-band can be accommodated in the geo-stationary orbit....which is the most useful orbit available.The reason for less number of satellites is that the spacing that can be obtained for C-band satellites in geo-stationary orbit is more(2,2.5 and 3.5 degrees) since the beams are wider.
Ku-Band
The advantages involve with Ku-band is far greater than C-band.Since the frequencies involved are high smaller antennas are required (typically 2 metres) and hence are cheap to install in buildings and towers.Due to high frequency the signals tend to be narrower and hence donot spread out much.The energy in the beam is concentrated and directed and hence receiving signals is comparitvely easier than C-band.
Multiple beams could use same frequency on different points on earth in the form of space division multiplexing (SDM) which is a channel access method based on creating parallel spatial pipes next to higher capacity pipes through spatial multiplexing , by which it is able to offer superior performance in radio multiple access communication systems.SDM can be implemented using phased array techniques. Hence beams can crisscross each other without interference.Because the beams are narrower large number of satellites in Ku-band can be accommodated in the geo-stationary orbit.
The uplink frequencies(14-14.5 GHz) are not used by the terrestrial systems but the downlink frequencies (11.7-12.2GHz) are used by them.Hence uplink transmissions don't observe interference but downlink transmission do.The most important disadvantage is the it suffers more atmospheric attenuation than C-band. It suffers absorption by clouds,rain and atmospheric depolarisation(change in the polarisation of the desired signal) and signal scintillations.So we require high gain both in transmitting and receiving equipments.
One practical application of Ku-band is the Direct to Home (DTH) satellite broadcasting.This is solely because we require smaller antennas appropriate for home users. Also by increasing FM deviation of video carrier in satellite uplink we can obtain improved FM carrier to noise ratio (CNR) .Greater FM deviation means wider FM bandwidth signals which can be converted into equivalent AM signals.Thus the installalations cost involved in Ku-band are greatly reduced.
Now the question arises which one is better ?
Both the C-band and Ku-band deliver high quality transmissions .So basically it depends on the choice of the interested frequency band and the location where the connection is required.For example in the Middle East Ku-band is efficient to use.
Upcoming Ka-Band?
Ka-band(27-40 GHz) is the newest band in satellite communication which offers high bandwidth communication.It is currently used for vehicle speed detection by law enforcement. It is also used by the Kepler which is a is a space observatory launched by NASA to discover earth like planets orbiting other stars.It basically downlinks the scientific data collected at the telescope. The main disadvantage of Ka-band is that it more signal attenuation in rainy conditions.However it is going to be used by upcoming Iridium Next satellite series.
C-Band
Although the equipment required for C-band is in inexpensive than Ku-band,less number of satellites in the C-band can be accommodated in the geo-stationary orbit....which is the most useful orbit available.The reason for less number of satellites is that the spacing that can be obtained for C-band satellites in geo-stationary orbit is more(2,2.5 and 3.5 degrees) since the beams are wider.
One more disadvantage attached to C-band is that since the frequencies involved in C -band are less than K-band it involves the use of large and expensive satellite antenna (typically about 15 meters in diameter) .Also the C-band is used by terrestrial microwave systems ,hence earth stations(ES) must be located from them.
The most important advantage of C-band is that they are immune to atmospheric attenuation.Rainfall and cosmic noise don't appreciably attenuate C-band signals. Also ionospheric scintillations are small compared to Ku-band.Hence they are mostly used for television broadcasting purposes. |
| C-Band Radar Dish antenna |
Ku-Band
The advantages involve with Ku-band is far greater than C-band.Since the frequencies involved are high smaller antennas are required (typically 2 metres) and hence are cheap to install in buildings and towers.Due to high frequency the signals tend to be narrower and hence donot spread out much.The energy in the beam is concentrated and directed and hence receiving signals is comparitvely easier than C-band.
Multiple beams could use same frequency on different points on earth in the form of space division multiplexing (SDM) which is a channel access method based on creating parallel spatial pipes next to higher capacity pipes through spatial multiplexing , by which it is able to offer superior performance in radio multiple access communication systems.SDM can be implemented using phased array techniques. Hence beams can crisscross each other without interference.Because the beams are narrower large number of satellites in Ku-band can be accommodated in the geo-stationary orbit.
The uplink frequencies(14-14.5 GHz) are not used by the terrestrial systems but the downlink frequencies (11.7-12.2GHz) are used by them.Hence uplink transmissions don't observe interference but downlink transmission do.The most important disadvantage is the it suffers more atmospheric attenuation than C-band. It suffers absorption by clouds,rain and atmospheric depolarisation(change in the polarisation of the desired signal) and signal scintillations.So we require high gain both in transmitting and receiving equipments.
One practical application of Ku-band is the Direct to Home (DTH) satellite broadcasting.This is solely because we require smaller antennas appropriate for home users. Also by increasing FM deviation of video carrier in satellite uplink we can obtain improved FM carrier to noise ratio (CNR) .Greater FM deviation means wider FM bandwidth signals which can be converted into equivalent AM signals.Thus the installalations cost involved in Ku-band are greatly reduced.
| Ku-Band DTH dish antenna |
Now the question arises which one is better ?
Both the C-band and Ku-band deliver high quality transmissions .So basically it depends on the choice of the interested frequency band and the location where the connection is required.For example in the Middle East Ku-band is efficient to use.
Upcoming Ka-Band?
Ka-band(27-40 GHz) is the newest band in satellite communication which offers high bandwidth communication.It is currently used for vehicle speed detection by law enforcement. It is also used by the Kepler which is a is a space observatory launched by NASA to discover earth like planets orbiting other stars.It basically downlinks the scientific data collected at the telescope. The main disadvantage of Ka-band is that it more signal attenuation in rainy conditions.However it is going to be used by upcoming Iridium Next satellite series.
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