Telecommunications – Carrier wave repeater or relay system – Portable or mobile repeater
Reexamination Certificate
1998-11-03
2001-05-15
Bost, Dwayne (Department: 2681)
Telecommunications
Carrier wave repeater or relay system
Portable or mobile repeater
C455S427000, C455S428000
Reexamination Certificate
active
06233429
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to telecommunication in general, and in particular to improved VSAT satellite telecommunications methods and apparatus.
BACKGROUND OF THE INVENTION
Primary design considerations for a VSAT geostationary satellite telecommunication network include the cost of the remote terminal (VSAT) as a function of its complexity, the bandwidth efficiency as determined by the access scheme, and the communications delay as a function of the distance to the satellite. VSAT networks typically have two basic network configurations, the “star” configuration and the “mesh” configuration, with each configuration having important implications regarding cost, efficiency, and delay.
In a star network each inbound message from a VSAT is transmitted via satellite to a hub station, being the center of the star network, which then directs the message to its destination, usually to an external terminal, the hub station itself, or another VSAT. In a star network, when one VSAT sends a message to another VSAT the message is transmitted twice via satellite, and is referred to as having traveled two “hops,” one from the source VSAT to the satellite and then to the hub (first hop), and another from the hub back to the satellite and then to the destination VSAT (second hop). With each hop an additional delay is added to the communication. A long delay is particularly undesirable in voice telecommunication where a delay is most noticeable between two VSATs The VSAT in a star network is relatively inexpensive, mainly because the hub station has a large satellite dish and powerful amplifiers that allow for simple and inexpensive RF VSAT components such as small antennas, commercial LNBs, and simple transmitter devices. Synchronization of VSATs is relatively simple as all VSATs listen to the hub station's outbound carrier, therefore timing “ticks” on the outbound transmission or any other similar method may be used.
In a mesh network any VSAT can communicate directly with any other VSAT in the network directly through a satellite without the need for an intermediate hub to relay messages between the VSATs, thus the delay is only one hop. In a mesh network the hub station is generally used to manage satellite resources such as allocating frequencies and performing Monitor & Control functions.
The VSAT in a mesh network is generally more expensive than the VSAT in a star network because of the former's ability to communicate with other VSATs and because there is no large antenna with which the VSAT communicates, such as the hub has in a star network. VSATs in a mesh network, therefore, generally require larger antennas and more powerful and stable RF front ends (i.e., LNBs, SSPAs, etc.) due to the symmetrical nature of the network and the link budget. Synchronization of VSATs is relatively complicated since each VSAT needs to acquire a time base from hub burst transmissions, which might be sparse and bursty, thus adding to the complexity and cost of a VSAT.
The hub-to-VSAT portion in a star network is usually more efficient than the same link in a mesh network as this link in a star network is continuous and may support multiple simultaneous communications efficiently by employing silence removal algorithms.
Some VSAT satellite telecommunications networks provide one or more links to a terrestrial network, such as a public switched telephone network (PSTN). In a star network this connection is usually located at the hub, and in a mesh network it can be at any VSAT as well. Multiple links to the PSTN at different locations would reduce the cost and delay of calls being made from the satellite network to the terrestrial one and vice-versa.
SUMMARY OF THE INVENTION
The present invention seeks to provide improved VSAT satellite telecommunications methods and apparatus that combine the benefits of star and mesh VSAT networks such that the average number of hops in VSAT-to-VSAT communication is reduced while keeping the VSATs relatively inexpensive.
There is thus provided in accordance with a preferred embodiment of the present invention a VSAT telecommunications system including a satellite, first and second VSAT terminals, and a hub communicating via the satellite with the first and second VSAT terminals, the transmissions from the hub are generally continuous, while transmissions from the VSAT terminals are generally in bursts, and the at least one first VSAT terminal has the capability of receiving transmissions from the hub but lacks the capability of receiving transmissions from another VSAT terminal, and the at least one second VSAT terminal has the capability of receiving transmissions from the hub and also has the capability of receiving transmissions from another VSAT terminal.
There is also provided in accordance with a preferred embodiment of the present invention an asymmetric VSAT telecommunications system for use with a satellite and a hub, the system including at least one first VSAT terminal, and at least one second VSAT terminal, the first VSAT terminal being operative to receive from the second VSAT terminal only via the hub, and the second VSAT terminal being operative to receive from the first VSAT terminal via the satellite and without passing through the hub.
There is additionally provided in accordance with a preferred embodiment of the present invention an asymmetric VSAT telecommunications system for use with a satellite and a hub, the system including at least first and second VSAT terminals and being characterized in that the transmission path from the first to the second VSAT terminals is shorter than the transmission path from the second to the first VSAT terminals.
Further in accordance with a preferred embodiment of the present invention the transmission path from the first to the second VSAT terminal does not pass through the hub, while the transmission path from the second to the first VSAT terminal does pass through the hub.
There is also provided in accordance with a preferred embodiment of the present invention a VSAT telecommunications system including a satellite, a hub, and a plurality of VSAT terminals, the transmissions from the hub are generally continuous, while transmissions from the VSAT terminals are generally in bursts, and each of the plurality of VSAT terminals communicate with the hub in a star configuration for management functions and communicate with others of the plurality of VSAT terminals in a mesh configuration for non-management functions.
There is additionally provided in accordance with a preferred embodiment of the present invention a VSAT telecommunications method for use with a satellite, a hub and at least first and second VSAT terminals which communicate with each other, the method including the steps of causing the at least first VSAT terminal to receive communications only via the hub, and causing the at least second VSAT terminal to receive communications not only via the hub.
There is also provided in accordance with a preferred embodiment of the present invention an asymmetric VSAT telecommunications method for use with a satellite and a hub, the method including operating a first VSAT terminal to receive from a second VSAT terminal only via the hub, and operating the second VSAT terminal to receive from the first VSAT terminal via the satellite and without passing through the hub.
There is additionally provided in accordance with a preferred embodiment of the present invention an asymmetric VSAT telecommunications method for use with a satellite and a hub, the method including operating at least one first and at least one second VSAT terminals for two way communications therebetween characterized in that the transmission path from the first VSAT terminal to the second VSAT terminal is shorter than the transmission path from the second VSAT terminal to the first VSAT terminal.
Further in accordance with a preferred embodiment of the present invention the transmission path from the first VSAT terminal to the second VSAT terminal does not pass through the hub, while the transmission path from
Frimerman Osher
Soffer Yaron
Bost Dwayne
Friedman Mark M.
Gilat Satellite Networks Ltd.
Persino Raymond B.
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