Wireless packet data distributed communications system
DCFirst Claim
1. A wireless packet data communications system, comprising:
- a control station, and a plurality of widely dispersed, remote terminals having an active mode during which they are capable of transmitting and receiving data packets and a sleep mode during which they are inactive, said control station and each of said remote terminals being capable of engaging in packet data communication over a TDM forward link from said control station to said terminals and a slotted multiple access return link from said terminals to said control station,each said remote terminal having an address and being assigned specific timeslots on the forward link during which it may be addressed by said control station, and each said terminal includinga timer operable in said sleep mode to cause said terminal to periodically enter the active mode during its assigned timeslot and listen for incoming data packets from said control station addressed to said terminal, anda processor for interpreting packets received over the forward link, andsaid control station includinga database for storing information pertaining to the timeslots assigned to the various remote terminals,means for transmitting on-demand, data packets addressed to specific terminals in their assigned timeslots on the forward link, andmeans for receiving data packets from the terminals in timeslots on the slotted return link.
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Abstract
A two-way satellite communications system includes an Earth station communicating with a plurality of remote terminals using a network access protocol that facilitates low power consumption by the terminals. The earth station generates forward link TDM packet data transmissions on one or-more satellite channels, and detects, despreads and decodes multiple concurrent return link slotted CDMA packet transmissions on one or more satellite channels. It communicates through a wired connection with a packet processing center which ultimately both delivers return link packet data to end-customers and receives forward link packet data from end-customers. The remote terminals receive, process and act upon forward link TDM transmissions on one or more satellite channels, and generate slotted spread spectrum CDMA transmissions on the return link on one or more satellite channels. The remote terminals communicate with a local digital data source and/or sink, digitize one or more local analog sensor signals, enter into a sleep mode to minimize the terminal'"'"'s power consumption, and access the satellite communications network in accordance with the system network access protocol.
416 Citations
37 Claims
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1. A wireless packet data communications system, comprising:
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a control station, and a plurality of widely dispersed, remote terminals having an active mode during which they are capable of transmitting and receiving data packets and a sleep mode during which they are inactive, said control station and each of said remote terminals being capable of engaging in packet data communication over a TDM forward link from said control station to said terminals and a slotted multiple access return link from said terminals to said control station, each said remote terminal having an address and being assigned specific timeslots on the forward link during which it may be addressed by said control station, and each said terminal including a timer operable in said sleep mode to cause said terminal to periodically enter the active mode during its assigned timeslot and listen for incoming data packets from said control station addressed to said terminal, and a processor for interpreting packets received over the forward link, and said control station including a database for storing information pertaining to the timeslots assigned to the various remote terminals, means for transmitting on-demand, data packets addressed to specific terminals in their assigned timeslots on the forward link, and means for receiving data packets from the terminals in timeslots on the slotted return link. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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- 20. A remote terminal for use in a wireless packet data communications system comprising a control station and a plurality of widely dispersed, remote terminals having an active mode during which they are capable of transmitting and receiving data packets and a sleep mode during they are inactive, said control station and each of said remote terminals being capable of engaging in packet data communication over a forward TDM link between said control station and said terminals and a slotted spread spectrum multiple access return link between said terminals and said control station, each said remote terminal having an address and being assigned timeslots during which it may be addressed by said control station, said remote terminal comprising an electronics unit for transmitting and receiving signals to and from said control station over said respective return and forward links, a timer operable in said sleep mode period to cause said terminal to periodically enter the active mode during said assigned timeslots to listen for incoming data packets from the control station addressed to said terminal, a processor for interpreting data received during said assigned timeslots and formatting outgoing data for transmission over said return link, and means for resetting said timer in response to packets received over said forward link.
- 30. A control station for a wireless packet data communications system comprising said control station and a plurality of widely dispersed, remote terminals having an active mode during which they are capable of transmitting and receiving data packets and a sleep mode during which they are inactive, said control station and each of said remote terminals being capable of engaging in packet data communication over a TDM forward link between said control station and said terminals and a slotted spread spectrum multiple access return link between said terminals and said control station, said forward and return links being established via satellite, each said remote terminal having an address and being assigned timeslots during which it wakes up to listen for a data racket from said control station, said control station comprising a database for storing the timeslots assigned to the various remote terminals, means for transmitting on-demand data packets addressed to specific terminals in their assigned timeslots in TDM format, means for interpreting data packets received in the timeslots on the slotted spread spectrum return link, and a packet processing center for formatting packets for transmission on the forward TDM link to remote terminals in their assigned timeslots and deformatting packets received on the return slotted spread spectrum link, said database being located in said packet processing center.
- 33. A wireless packet data communications system, comprising a control station and a plurality of widely dispersed, remote terminals, means for establishing a forward TDM link from said control station to said terminals, and means for establishing a slotted multiple access spread spectrum return link from said terminals to said control station to permit selective packet data communication between said control station and any of said terminals, groups of said terminals being assigned specific timeslots during which they may be addressed by said control station, and said control station assigning said timeslots so as to spread the active periods throughout the day means for controlling a delay between the time of reception of a command by a terminal and the time when it transmits its response back to the control station, said data packets transmitted over said forward link having an overflow flag to indicate that additional data is being transmitted in a subsequent timeslot, and said control station further comprising means for spreading the messages addressed to the terminals over two or more subframes and setting said overload flag to advise said terminals that messages for them may be spread over several subframes in order to relieve congestion in the system.
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35. A method of establishing communication in a wireless packet data communications system comprising a control station and a plurality of widely dispersed, remote terminals having an active mode during which they are capable of transmitting and receiving data packets and a sleep mode during which they are inactive, said control station and each of said remote terminals being capable of engaging in packet data communication over a TDM forward link from said control station to said terminals and a slotted multiple access return link from said terminals to said control station, said forward and return links being via satellite, and each said remote terminal having an address and being assigned specific timeslots on the forward link during which it may be addressed by said control station, said method comprising the steps of:
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periodically waking up said terminals in their assigned timeslots to listen for incoming data packets addressed thereto from the control station; extracting information pertaining to the timeslots assigned to the various remote terminals from a database at the control station; transmitting on-demand data packets addressed to specific terminals in their assigned timeslots on the forward link; and receiving data packets from the terminals in timeslots on the slotted return link. - View Dependent Claims (36, 37)
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Specification