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Meshed NetworkMeshed or hub-less VSAT networks offer a means of establishing a switched point-to-point data and telephony network. Links are set up directly between remote terminals, often on a call by call basis.
When compared to a star network, the main advantage of a meshed VSAT network lies in the low delay between remote sites. As connections between remote terminals are made directly without requiring a central hub station, the so called “double hop” involving two up-links and two downlinks is avoided. This results in half the round trip delay – in the range of 750 ms for a TDM / TDMA mesh instead of 1500 ms in a hubbed network using the same technology. Latency is a crucial quality parameter of telephony applications. Thus many meshed VSAT networks were originally designed for telephony and have been adapted for data later. A meshed VSAT network generally consists of several user terminals and a single network control station which can be adjacent to one user terminal. Because of the missing hub station, the technical specifications of the terminals for meeting the link budget requirements are much higher than for the remotes stations of a star VSAT network. Antenna sizes of 2.4 to 3.8 m and a transmitter power range from 10 to 50 W are typical for terminals of a meshed networks. In addition a DAMA controller and a bank of modems are common for meshed terminals, which increases the terminal cost further. Thus the number of terminals in a meshed VSAT networks is generally small (a few to several dozens) when compared to a star network (up to several thousands). Meshed systems tend to be a niche market among VSAT networks. Typical applications for meshed VSAT networks include:
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Although meshed VSAT networks do not have a hub, they generally have a network control station which controls the allocation of satellite resources across the network. The network control center is only involved in the signaling for call set up, and in monitoring the operation of the network. This is in contrast to a star VSAT network in which all communications, even between two remote terminals on the network, must pass through the hub. The network control center is only involved in the call set up and tearing down processes.