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| Author: | Prodigy [ Thu Jul 01, 2010 7:56 pm ] |
| Post subject: | he Three Categories of Satellite Communications Architecture |
he Three Categories of Satellite Communications Architecture: Which is Best for Satellite Optimization? By David Sims If you’re interested in signal gain, double-hop elimination, IP multiplexing and mesh networking without a teleport, check into satellite communications. “On-board processing has the potential to bring video on-demand, capacity growth and convergence of ground and space networks, thus promising to revolutionize satellite as we know it,” says Giovanni Verlini in a piece appearing in Satellite Today. The article tackles the question, “what exactly is on-board processing, and what are the characteristics of the payloads equipped with this technology?” As Jeff Snyder, group vice president, SkyTerra Communications explains the answer, satellite architectures “can be put into three categories: conventional bent-pipe radiofrequency systems, on-board processed bent-pipe systems and on-board digital processed systems.” The first type, Snyder says, “is used in fixed service and direct broadcast satellites, the second type in systems such as SkyTerra satellites, while the last type is typical of systems such as the Iridium constellation.” And it might not appear so at first, but Snyder assures us that “the differences between these systems are significant. On-board processed bent-pipe systems typically perform frequency channelization of signals by digitally processing them at baseband or near baseband.” This means the channelized signals can then be “conditioned and processed prior to up-conversion for retransmission.” However, the signals are not demodulated to their digital content: “The advantage of on-board processed bent-pipe systems over conventional bent-pipe systems is that relatively narrowband channels can be processed and the resulting channels can be switched between a large number of beams,” he says, resulting in frequency reuse in narrowband communications networks. Snyder says on-board digital processed systems, “take the capacity optimization process a step further. They process signals by demodulating and decoding the received waveforms to the digital packet or bit level… so the system has extremely flexible signal and information routing.” Furthermore, he adds, “depending on the complexity of the digital payload, services such as packet replication and directed multicasting can also be implemented,” and such systems “also enable inter-satellite links, thus reducing the need for gateways in a global satellite network.” And considering the benefits of satellite optimization, it’s good that we have someone like Snyder to explain the variances in architecture. |
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