Methods and apparatus for performing timing synchronization with base stations
First Claim
1. A method of operating a communications device for use in a communications system Where beacon time slots occur on a periodic basis, a beacon signal being transmitted by a satellite base station during each beacon time slot according to a periodic downlink timing structure, said downlink timing structure including a plurality of superslots within each beacon slot, the individual superslots within a beacon slot being identifiable through the use of a superslot index, each superslot including a plurality of symbol transmission time periods, the method comprising:
- receiving at least one beacon signal from the satellite base station;
processing the received beacon signal to determine a downlink timing reference point, superslots occurring within a beacon slot having a predetermined relationship to the determined downlink timing reference point;
transmitting an access probe signal to said base station;
receiving a response to the access probe signal from the base station, the response including information indicating at least one of;
i) an amount of an indicated main superslot timing offset correction, the amount of the main superslot timing offset correction being an integer multiple of a superslot time period;
ii) a superslot identifier indicating the position of a superslot within a beacon slot during which the base station received the access probe signal to which the received response corresponds;
iii) an identifier that identifies the communications device which transmitted the access probe signal to which the received response corresponds or iv) an identifier that identifies the access probe to which the response being responding to; and
performing a transmission timing adjustment as a function of the information included in the received response.
1 Assignment
0 Petitions
Accused Products
Abstract
A wireless terminal using OFDM signaling supporting both terrestrial and satellite base station connectivity operates using conventional access probe signaling in a first mode of operation to establish a timing synchronized wireless link with a terrestrial base station. In a second mode of operation, used to establish a timing synchronized wireless link with a satellite base station, a slightly modified access protocol is employed. The round trip signaling time and timing ambiguity between a wireless terminal and a satellite base station is substantially greater than with a terrestrial base station. The modified access protocol uses coding of access probe signals to uniquely identify a superslot index within a beaconslot. The modified protocol uses multiple access probes with different timing offsets to further resolve timing ambiguity and allows the satellite base station access monitoring interval to remain small in duration. Terrestrial base station location/connection information is used to estimate initial timing.
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Citations
31 Claims
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1. A method of operating a communications device for use in a communications system Where beacon time slots occur on a periodic basis, a beacon signal being transmitted by a satellite base station during each beacon time slot according to a periodic downlink timing structure, said downlink timing structure including a plurality of superslots within each beacon slot, the individual superslots within a beacon slot being identifiable through the use of a superslot index, each superslot including a plurality of symbol transmission time periods, the method comprising:
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receiving at least one beacon signal from the satellite base station; processing the received beacon signal to determine a downlink timing reference point, superslots occurring within a beacon slot having a predetermined relationship to the determined downlink timing reference point; transmitting an access probe signal to said base station; receiving a response to the access probe signal from the base station, the response including information indicating at least one of;
i) an amount of an indicated main superslot timing offset correction, the amount of the main superslot timing offset correction being an integer multiple of a superslot time period;
ii) a superslot identifier indicating the position of a superslot within a beacon slot during which the base station received the access probe signal to which the received response corresponds;
iii) an identifier that identifies the communications device which transmitted the access probe signal to which the received response corresponds or iv) an identifier that identifies the access probe to which the response being responding to; andperforming a transmission timing adjustment as a function of the information included in the received response. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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2. The method of 1, wherein said identifier of the received access probe includes information that identifies the downlink superslot in which the communication device determined the probe was transmitted.
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18. A communications device for use in a communications system where beacon time slots occur on a periodic basis, a beacon signal being transmitted by a satellite base station during each beacon time slot according to a periodic downlink timing structure, said downlink timing structure including a plurality of superslots within each beacon slot, the individual superslots within a beacon slot being identifiable through the use of a superslot index, each superslot including a plurality of symbol transmission time periods, the method comprising:
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a receiver configured to receive at least one beacon signal from the satellite base station; a processing module configured to process the received beacon signal to determine a downlink timing reference point, superslots occurring within a beacon slot having a predetermined relationship to the determined downlink timing reference point; a transmitter module for transmitting an access probe signal to said base station; a receiver module for receiving a response to the access probe signal from the base station, the response including information indicating at least one of;
i) an amount of an indicated main superslot timing offset correction, the amount of the main superslot timing offset correction being an integer multiple of a superslot time period;
ii) a superslot identifier indicating the position of a superslot within a beacon slot during which the base station received the access probe signal to which the received response corresponds, iii) an identifier that identifies the communications device which transmitted the access probe signal to which the received response corresponds or iv) an identifier that identifies the access probe to which the response being responding to; anda transmission timing adjustment module for performing a transmission timing adjustment as a function of the information included in the received response.
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- 19. The communications device of aim 18, wherein said access probe signal is an OFDM signal.
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21. A method of operating a communications terminal in an OFDM system including terrestrial and satellite base stations which use OFDM signals for both uplink and downlink signaling, the method comprising:
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determining if a base station to which said communications terminal is seeking to send OFDM uplink signals is a satellite base station or a terrestrial base station; performing a first uplink timing synchronization process if it is determined that said base station is a satellite base station; performing a second uplink timing synchronization process if it is determined that said base station is a terrestrial base station, said second uplink timing synchronization process being different from said first uplink timing synchronization process; wherein both said terrestrial and satellite base stations have a downlink timing structure that includes a plurality of superslots which recur in a periodic manner, each superslot including a plurality of OFDM symbol transmission time periods; and wherein said first uplink timing synchronization process supports the communication of an uplink timing correction signal to the communications terminal which indicates an uplink transmission timing synchronization correction exceeding the duration of a downlink superslot. - View Dependent Claims (22, 23)
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24. A method of operating a wireless terminal to communicate with base stations in a communications system including a plurality of base stations, the method comprising:
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storing base station location information in memory; receiving a signal from a first base station; determining a time at which to transmit an access signal to a second base station as a function of stored location information indicating the location of said first base station from which said wireless terminal received said signal, said determining a time at which to transmit an access signal to a second base station including receiving a signal from the second base station, determining from the received signal a timing reference point, and determining said time at which to transmit an access signal relative to the determined reference point using uplink timing correction information calculated from said stored location information indicating the location of said first base station and information indicating the location of said second base station, said time at which to transmit an access signal being determined so that the transmitted access signal will be received at the second base station during an access interval in which received access signals are processed by said second base station; and transmitting said access signal at the determined time. - View Dependent Claims (25, 26, 27)
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28. A communications device for use in a communications system where beacon time slots occur on a periodic basis, a beacon signal being transmitted by a satellite base station during each beacon time slot according to a periodic downlink timing structure, said downlink timing structure including a plurality of superslots within each beacon slot, the individual superslots within a beacon slot being identifiable through the use of a superslot index, each superslot including a plurality of symbol transmission time periods, the device comprising:
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means for receiving at least one beacon signal from the satellite base station; means for processing the received beacon signal to determine a downlink timing reference point, superslots occurring within a beacon slot having a predetermined relationship to the determined downlink timing reference point; means for transmitting an access probe signal to said base station; wherein said means for receiving are also for receiving a response to the access probe signal from the base station, the response including information indicating at least one of;
i) an amount of an indicated main superslot timing offset correction, the amount of the main superslot timing offset correction being an integer multiple of a superslot time period;
ii) superslot identifier indicating the position of a superslot within a beacon slot during which the base station received the access probe signal to which the received response corresponds;
iii) identifier that identifies the communications device which transmitted the access probe signal to which the received response corresponds or iv) an identifier that identifies the access probe to which the response being responding to; andmeans for performing a transmission timing adjustment as a function of the information included in the received response.
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29. A wireless terminal to communicate with base stations in a communications system including a plurality of base stations, the wireless terminal comprising:
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a memory for storing base station location information; a receiver configured to receive a signal from a first base station; a location based timing determination module configured to determine a time at which to transmit an access signal to a second base station as a function of stored location information indicating the location of said first base station from which said wireless terminal received said signal; a transmitter configured to transmit said access signal at the determined time; wherein said location based timing determination module determines a timing reference point from a signal received from the second base station, as part of determining said time at which to transmit an access signal to the second base station; wherein said location based timing determination module determines the time at which to transmit an access signal to the second base station relative to the determined timing reference point using uplink timing correction information calculated from the stored location information indicating the location of said first base station and information indicating the location of said second base station, said time at which to transmit an access signal being determined so that the transmitted access signal will be received at the second base station during an access interval in which received access signals are processed by said second base station.
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30. A wireless terminal to communicate with base stations in a communications system including a plurality of base stations, the wireless terminal comprising:
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means for storing base station location information; means for receiving a signal from a first base station; means for determining a time at which to transmit an access signal to a second base station as a function of stored location information indicating the location of said first base station from which said wireless terminal received said signal; means for transmitting said access signal at the determined time; wherein said means for determining determine a timing reference point from a signal received from the second base station, as part of said determining the time at which to transmit an access signal to the second base station; and wherein said means for determining determine the time at which to transmit an access signal to the second base station relative to the determined timing reference point using uplink timing correction information calculated from the stored location information indicating the location of said first base station and information indicating the location of said second base station, said time at which to transmit an access signal being determined so that the transmitted access signal will be received at the second base station during an access interval in which received access signals are processed by said second base station.
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31. A communications terminal in an OFDM system including terrestrial and satellite base stations which use OFDM signals for both uplink and downlink signaling, the communications terminal comprising:
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a processor configured to control the communications terminal to; determine if a base station to which said communications terminal is seeking to send OFDM uplink signals is a satellite base station or a terrestrial base station; perform a first uplink timing synchronization process if it is determined that said base station is a satellite base station; and perform a second uplink timing synchronization process if it is determined that said base station is a terrestrial base station, said second uplink timing synchronization process being different from said first uplink timing synchronization process; wherein both said terrestrial and satellite base stations have a downlink timing structure that includes a plurality of superslots which recur in a periodic manner, each superslot including a plurality of OFDM symbol transmission time periods; and wherein said first uplink tuning synchronization process supports the communication of an uplink timing correction signal to the communications terminal which indicates an uplink transmission timing synchronization correction exceeding the duration of a downlink superslot.
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Specification