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 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;
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 a first access probe at a time corresponding to a first timing offset relative to the start of a super slot in a beacon slot;
transmitting a second access probe at a time corresponding to a second timing offset relative to the start of a super slot, said second access probe being transmitted at a point in time, which is less than the longer of i) twice the time required for a transmitted signal to travel from the communications device to the base station and ii) the duration of a superslot, from the point in time at which the first access probe was transmitted;
monitoring to determine if a response to one of the transmitted access probes was received from the base station; and
if it is determined that a response was received from the base station, performing a transmission timing adjustment as a function of information included in said response.
3 Assignments
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
20 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 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; 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 a first access probe at a time corresponding to a first timing offset relative to the start of a super slot in a beacon slot; transmitting a second access probe at a time corresponding to a second timing offset relative to the start of a super slot, said second access probe being transmitted at a point in time, which is less than the longer of i) twice the time required for a transmitted signal to travel from the communications device to the base station and ii) the duration of a superslot, from the point in time at which the first access probe was transmitted; monitoring to determine if a response to one of the transmitted access probes was received from the base station; and if it is determined that a response was received from the base station, performing a transmission timing adjustment as a function of information included in said response. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. 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 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 for receiving at least one beacon signal; a processing module for processing received beacon signals to determine, based on at least one received beacon signal, 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 a first access probe at a time corresponding to a first timing offset relative to the start of a super slot in a beacon slot and for transmitting a second access probe at a time corresponding to a second timing offset relative to the start of a super slot, said second access probe being transmitted at a point in time, which is less than the larger of i) twice the time required for a transmitted signal to travel from the communications device to the base station and ii) the duration of a downlink superslot, from the point in time at which the first access probe was transmitted; a monitoring module for determining if a response to one of the transmitted access probes was received from the base station; and a timing adjustment module for performing a transmission timing adjustment as a function of information included in a response to a transmitted access probe. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A machine readable medium in form of a memory device for use in a communications system where beacon time slots occur on a periodic basis, a beacon signal being transmitted by a 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 computer readable medium comprising:
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instructions for causing a device to receive a beacon signal; instructions for causing the device to determine a downlink timing reference point from the received beacon signal, the received beacon signal; instructions for causing the device to transmit a first access probe at a time corresponding to a first timing offset relative to the start of a super slot in a beacon slot; instructions for causing the device to transmit a second access probe at a time corresponding to a second timing offset relative to the start of a super slot, said second access probe being transmitted at a point in time, which is less than the longer of i) twice the time required for a transmitted signal to travel from the communications device to the base station and ii) the duration of a superslot, from the point in time at which the first access probe was transmitted; instructions for causing the device to monitor for a response to the transmitted access probes; and instructions for causing the device to perform a transmission timing adjustment as a function of information included in said response. - View Dependent Claims (16, 17)
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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 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 communication device comprising:
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means for receiving at least one beacon signal; 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 a first access probe at a time corresponding to a first timing offset relative to the start of a super slot in a beacon slot; means for transmitting a second access probe at a time corresponding to a second timing offset relative to the start of a super slot, said second access probe being transmitted at a point in time, which is less than the longer of i) twice the time required for a transmitted signal to travel from the communications device to the base station and ii) the duration of a superslot, from the point in time at which the first access probe was transmitted; means for monitoring to determine if a response to one of the transmitted access probes was received from the base station; and means for performing a transmission timing adjustment as a function of information included in said response. - View Dependent Claims (19, 20)
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Specification