The television & radio broadcasting band like C-band & Ku-band were the frequency band that was allocated for commercial use via satellites in India. Most of the million people’s in the India still used C-band & Ku-band. The lower frequencies used by C-Band perform better under adverse weather conditions than the Ku-band or Ka-band frequencies.
In a submission to the Telecom Regulatory Authority of India (TRAI), CASBAA pointed out that satellite C-band frequencies support television services to 149 million Indian homes, as well as VSAT networks and other critical communications services. Said CASBAA: “the wide use currently being made of this spectrum for the benefit of the Indian population is a convincing reason for the Indian government to oppose “harmonized” designation of the C-band frequencies for IMT.”
The submission rebutted “fallacies and misinformation” provided to the TRAI in a submission by the mobile industry, some parts of which were “manifestly untrue.” The mobile industry is seeking to have the ITU’s next World Radiocommunication Conference (WRC) divert C-band frequencies for mobile use. This strategy, said the CASBAA submission, seeks to lower mobile investment costs by acquiring additional spectrum which is providing television and other services to Indian consumers. “The cheapest option that allows this wealthy industry to avoid investing money into their networks is to ask for more spectrum. Taking spectrum used by other industries such as satellite costs mobile operators nothing but has a massive knock-on cost to society in terms of services lost.”
The C-band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 4.0 to 8.0 gigahertz (GHz); however, this definition is the one used by radar manufacturers and users, not necessarily by microwave radio telecommunications users. The C-band (4 to 8 GHz) is used for many satellite communications transmissions, some Wi-Fi devices, some cordless telephones, and some weather radar systems.
The communications C-band was the first frequency band that was allocated for commercial telecommunications via satellites. The same frequencies were already in use for terrestrial microwave radio relay chains. Nearly all C-band communication satellites use the band of frequencies from 3.7 to 4.2 GHz for their downlinks, and the band of frequencies from 5.925 to 6.425 GHz for their uplinks. Note that by using the band from 3.7 to 4.0 GHz, this C-band overlaps somewhat into the IEEE S-band for radars.
The C-band communication satellites typically have 24 radio transponders spaced 20 MHz apart, but with the adjacent transponders on opposite polarizations. Hence, the transponders on the same polarization are always 40 MHz apart. Of this 40 MHz, each transponder utilizes about 36 MHz. (The unused 4.0 MHz between the pairs of transponders acts as “guard bands” for the likely case of imperfections in the microwave electronics.)
One use of the C-band is for satellite communication, whether for full-time satellite television networks or raw satellite feeds, although subscription programming also exists. This use contrasts with direct-broadcast satellite, which is a completely closed system used to deliver subscription programming to small satellite dishes that are connected with proprietary receiving equipment.
The satellite communications portion of the C-band is highly associated with television receive-only satellite reception systems, commonly called “big dish” systems, since small receiving antennas are not optimal for C-band systems. Typical antenna sizes on C-band capable systems ranges from 7.5 to 12 feet (2.5 to 3.5 meters) on consumer satellite dishes, although larger ones also can be used. For satellite communications, the microwave frequencies of the C-band perform better under adverse weather conditions in comparison with the Ku band (11.2 GHz to 14.5 GHz), microwave frequencies used by other communication satellites. Rain fade – the collective name for the negative effects of adverse weather conditions on transmission – is mostly a consequence of precipitation and moisture in the air.
The C-band also includes the 5.8 GHz ISM band between 5.725 – 5.875 GHz, which is used for medical and industrial heating applications and many unlicensed short range microwave communication systems, such as cordless phones, baby monitors, and keyless entry systems for vehicles. The C-band frequencies of 5.4 GHz band [5.15 to 5.35 GHz, 5.47 to 5.725 GHz, or 5.725 to 5.875 GHz, depending on the region of the world] are used for IEEE 802.11a Wi-Fi wireless computer networks.
Slight variations in the assignments of C-band frequencies have been approved for use in various parts of the world, depending on their locations in the three ITU radio regions. Note that one region includes all of Europe and Africa, plus all of Russia; a second includes all of the Americas, and the third region includes all of Asia outside of Russia, plus Australia and New Zealand. This latter region is the most populous one, since it includes the People’s Republic of China, India, Pakistan, Japan, and Southeast Asia.
This band is comprised of Digital signals in the 12 to 18 GHz frequency range used for Direct to Home (DTH) broadcast in India and requires much smaller dish antenna (2 to 4 feet) to receive the more focused signals but is susceptible to outages during bad weather conditions like heavy rains.
The Ku band is the portion of the electromagnetic spectrum in the microwave range of frequencies from 12 to 18 gigahertz (GHz). The symbol is short for “K-under” (originally German: Kurz-unten), because it is the lower part of the original NATO K band, which was split into three bands (Ku, K, and Ka) because of the presence of the atmospheric water vapor resonance peak at 22.24 GHz, (1.35 cm) which made the center unusable for long range transmission. In radar applications, it ranges from 12-18 GHz according to the formal definition of radar frequency band nomenclature in IEEE Standard 521-2002.
Ku band is primarily used for satellite communications, most notably the downlink used by direct broadcast satellites to broadcast satellite television, and for specific applications such as NASA’s Tracking Data Relay Satellite used for both space shuttle and International Space Station (ISS) communications. Ku band satellites are also used for backhauls and particularly for satellite from remote locations back to a television network’s studio for editing and broadcasting. The band is split by the International Telecommunication Union (ITU) into multiple segments that vary by geographical region. NBC was the first television network to uplink a majority of its affiliate feeds via Ku band in 1983. Some frequencies in this radio band are employed in radar guns used by law enforcement to detect vehicles speeding, especially in Europe.
Compared with C-band, Ku band is not similarly restricted in power to avoid interference with terrestrial microwave systems, and the power of its uplinks and downlinks can be increased. This higher power also translates into smaller receiving dishes and points out a generalization between a satellite’s transmission and a dish’s size. As the power increases, the size of an antenna’s dish will decrease. This is because the purpose of the dish element of the antenna is to collect the incident waves over an area and focus them all onto the antenna’s actual receiving element, mounted in front of the dish (and pointed back towards its face); if the waves are more intense, fewer of them need to be collected to achieve the same intensity at the receiving element.
A major attraction of the band over lower frequency microwave bands is that the shorter wavelengths allow sufficient angular resolution to separate the signals of different communication satellites to be achieved with smaller terrestrial parabolic antennas. From the Rayleigh criterion, the diameter of a parabolic dish required to create a radiation pattern with a given angular beamwidth (gain) is proportional to the wavelength, and thus inversely proportional to the frequency. At 12 GHz a 1-meter dish is capable of focusing on one satellite while sufficiently rejecting the signal from another satellite only 2 degrees away. This is important because satellites in FSS (Fixed Satellite Service) service (11.7-12.2 GHz in the U.S.) are only 2 degrees apart. At 4 GHz (C-band) a 3-meter dish is required to achieve this narrow angular resolution. Note the inverse linear correlation between dish size and frequency. For Ku satellites in DBS (Direct Broadcast Satellite) service (12.2-12.7 GHz in the U.S.) dishes much smaller than 1-meter can be used because those satellites are spaced 9 degrees apart. As power levels on both C and Ku band satellites have increased over the years, dish beam-width has become much more critical than gain.
The Ku band also offers a user more flexibility. A smaller dish size and a Ku band system’s freedom from terrestrial operations simplifies finding a suitable dish site. For the end users Ku band is generally cheaper and enables smaller antennas (both because of the higher frequency and a more focused beam). Ku band is also less vulnerable to rain fade than the Ka band frequency spectrum.
The satellite operator’s Earth Station antenna does require more accurate position control when operating at Ku band due to its much narrower focus beam compared to C band for a dish of a given size. Position feedback accuracies are higher and the antenna may require a closed loop control system to maintain position under wind loading of the dish surface.
There are, however, some disadvantages of Ku band system. Around 10 GHz is the absorption peak due to orientation relaxation of molecules in liquid water. Above 10 GHz, Mie scattering takes over. The effect is a noticeable degradation, commonly known as rain fade, at heavy rain (100 mm/h). This problem can be mitigated, however, by deploying an appropriate link-budget strategy when designing the satellite network, and allocating a higher power consumption to compensate rain fade loss. Therefore, the Ku band satellites typically require considerably more power to transmit than the C-band satellites. A similar phenomenon, called “snow fade”, is not specific for the Ku band. It is due to snow or ice accumulation on a dish significantly altering its focal point.
The frequency band of 26.5-40 GHz is used for Ka-Band communication which includes wide band multimedia services, mobile information systems, SPACELAN, e-Commerce and high bandwidth internet using high capacity for more user demand. But communication in this high frequency is more susceptible to rain attenuation which degrades the link quality and decreases the signal to noise ratio mainly in India.
The band is called Ka, short for “K-above” because it is the upper part of the original NATO K band, which was split into three bands because of the presence of the atmospheric water vapor resonance peak at 22.24 GHz, (1.35 cm) which made the center unusable for long range transmission. The 30/20 GHz band is used in communications satellites, uplink in either the 27.5 GHz and 31 GHz bands, and high-resolution, close-range targeting radars aboard military airplanes. Some frequencies in this radio band are used for vehicle speed detection by law enforcement. The Kepler Mission uses this frequency range to downlink the scientific data collected by the space telescope.
The designation “Ka-band” is from Kurz-above, which stems from the German word “kurz” meaning short. In satellite communications, the Ka band allows higher bandwidth communication. It is used in the Inmarsat I-5 system and will be used in the Iridium Next satellite series, as well as the James Webb Space Telescope. The Ka band is more susceptible to rain attenuation than is the Ku band, which in turn is more susceptible than the C band. The frequency is commonly used by cosmic microwave background experiments.