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Satellite communications
Published in Matthew N. O. Sadiku, Optical and Wireless Communications, 2018
A very small aperture terminal (VSAT) is a dish antenna that receives signals from a satellite. (The dish antenna has a diameter that is typically in the range of 1.2 to 2.8 m, but the trend is toward smaller dishes no more than 1.5 m in diameter.) A VSAT may also be regarded as a complete earth station that can be installed on the user’s premises and provide communication services in conjunction with a larger (typically 6–9 m) earth station acting as a network management center (NMC), as illustrated in Figure 8.5.
Satellites
Published in Michael M. A. Mirabito, Barbara L. Morgenstern, Mitchell Kapor, The New Communications Technologies, 2004
Michael M. A. Mirabito, Barbara L. Morgenstern, Mitchell Kapor
Ku-band technology spurred the growth of a satellite system that employs very small aperture terminals (VSATs). A VSAT is a compact dish mated with the necessary electronic hardware to create a cost-effective communications system composed of a few or numerous sites.
Board-Level Ku-Band Power Amplifier: Design and Challenges
Published in IETE Journal of Research, 2022
Hemant Kumar Singhal, Karun Rawat
For time-sensitive and critical communications, satellite services have grown tremendously in the past few decades. Cost reduction and compact size along with high data rate are the key requirements of the communication industry. For high data rate satellite communications, transceivers with very small aperture terminals (VSAT) are used. In this context, the design of Ku-band power amplifier (PA) becomes challenging [1–4]. For the design of the Ku-band PA, Gallium arsenide (GaAs) PAs have been used for a long time, but they have limitations in terms of output power level. Recently, Gallium nitride (GaN) devices have emerged as a high power device at high frequency due to their wide bandgap, which results in high breakdown voltage as compared to GaAs [5,6].
A Survey of National Disaster Communication Systems and Spectrum Allocation - an Indian Perspective
Published in IETE Technical Review, 2020
Shrayan Das, Kirtan Gopal Panda, Debarati Sen, Wasim Arif
Nation Informatics Center (NIC) is the nodal IT organization of GOI for informatics development and networking. NIC undertook informatics R&D under the “Natural Hazards Management Information System” program in the 1990s to support the United Nation Natural Disaster Reduction Decade Program. This led to the development of NICNET. NICNET [9] connects all 35 States and Union Territories in the country to central government ministries and departments which act as nodal coordination centers for disaster mitigation. The network supports both terrestrial and satellite connectivity which has been briefly discussed below: Terrestrial Connectivity: NICNET provides terrestrial connectivity through dedicated leased lines and countrywide fiber optic networks belonging to the Bharat Sanchar Nigam Limited (BSNL), the Power Grid Corporation of India Limited (PGCIL) and RailTel Corporation of India Limited (RAILTEL) among others. The network links Central Government Ministries and Departments in Delhi, acting as nodal coordination centers for PPDR operations through 10–100 Mbps high-speed links. At the same time, NIC state centers are connected to GOI departments and ministries through 45–155 Mbps internet connectivity, with satellite networks as standby. Leased lines and user dial-up facilities connect NIC state centers to state departments. The network links a total of 576 NIC District Units to states through 2 Mbps lines. NICNET works on SCPC and DAMA Mesh Networks. Video-conferencing on NICNET is through IP based prefixed scheduling at data rates of 384 Kbps or more. The main advantage of terrestrial NICNET is that it provides high speed and secure communication services between disaster hit zones and centralized coordinating centers thereby enabling fast decision making and prompt action by authorities.Satellite Connectivity: NICNET satellite connectivity through VSAT terminals are used in locations where either terrestrial connectivity is not available (less than 5 to 10% locations) or there has been a complete collapse of the existing terrestrial network. NICNET satellite network uses both Intelsat and the indigenously developed Indian National Satellite System (INSAT) constellations, ensuring adequate system redundancy. The network consists of five Ku Band transponders having variable bandwidths. Four of these transponders operate on a bandwidth of 36 MHz while the remaining one has a bandwidth of 72 MHz. The transponders are leased from INTELSAT-906 with the INSAT-3A providing 3-4 additional transponders of 22.5 MHz bandwidth each. The satellite network operates about 2500 VSAT terminals in both districts and blocks of Jammu and Kashmir, Chhattisgarh, Orissa, and a few other North Eastern States. Similar to the NICNET terrestrial networks, these VSATs are based on DAMA (for voice and video communication) and DVB (for data communication) technologies.