Method of and apparatus for time synchronization in a communication system

A method of time aligning transmissions received from a plurality of remote units at a hub station, said method comprising:

• transmitting a first signal from a first remote unit to said hub station, said first signal advanced by time δt with respect to an on-time estimate;
• receiving a responsive advanced signal quality indication at said first remote unit from said hub station;
• sending a second signal from said first remote unit to said hub station, said second signal retarded by time δt with respect to said on-time estimate;
• receiving a responsive retarded signal quality indication at said first remote unit from said hub station;
• and
• advancing in time said on-time estimate if said responsive advanced signal quality indication indicates a better signal quality than said responsive retarded signal quality indication.

A method of time aligning transmissions received from a plurality of remote units at a hub station, said method comprising:

• transmitting a first signal from a first remote unit to said hub station, said first signal advanced by time δt with respect to an on-time estimate;
• determining an advanced signal quality indication at said hub station;
• sending a second signal from said first remote unit to said hub station, said second signal retarded by time δt with respect to said on-time estimate;
• determining a retarded signal quality indication at said hub station;
• and
• sending a command from said hub station to said remote unit to advance in time said on-time estimate if said advanced signal quality indication indicates a better signal quality than said retarded signal quality indication.

A method of time aligning transmissions received from a plurality of remote units at a hub station, said method comprising:

• receiving at a hub station an indication of actual time;
• transmitting a time tag transmission from said hub station to said plurality of remote units via a repeater, said time tag transmission indicating a time equal to said actual time offset by a current time delay estimate;
• receiving a copy of said time tag transmission from said repeater at said hub station;
• adjusting said current time delay estimate based upon the time at which said copy is received;
• and
• sending a subsequent time tag transmission based upon said adjusted current delay time estimate.

An remote unit comprising:

• a transmitter configured to transmit a signal to a repeater according to a transmission clock;
• a receiver configured to receive a copy of said signal as transmitted by said repeater and configured to receive a time reference;
• and
• a time alignment module coupled to said transmitter and said receiver and configured to determine a time difference between transmission of said signal and reception of said copy of said signal and configured to adjust said transmission clock based upon said time difference and said time reference.

A remote unit comprising:

• a transmitter configured to transmit a first signal to said hub station, said first signal advanced in time by a time δt with respect to an on-time estimate and configured to transmit a second signal to said hub station, said second signal retarded by a time δt with respect to said on-time estimate;
• a receiver configured to receive a responsive advanced signal quality indication from said hub station in response to said first signal and configured to receive a responsive retarded signal quality indication from said hub station in response to said second signal;
• and
• a timing module coupled to said transmitter and said receiver and configured to advance in time said on-time estimate if said responsive advanced signal quality indicates a higher signal quality than said responsive retarded signal quality.

A hub station, comprising:

• a receiver configured to receive an indication of actual time;
• a transmitter configured to transmit a time tag transmission to said plurality of remote units via a repeater, said time tag transmission indicating a time equal said actual time offset by a current time delay estimate;
• a receiver configured to receive a copy of said time tag transmission from said repeater;
• and
• a time adjustment module coupled to said receiver, configured to receive said copy and configured to adjust said current time delay estimate based upon the time at which said copy is received;
• wherein said transmitter is further configured to send a subsequent time tag transmission based upon said adjusted current delay time estimate.

An apparatus for time aligning transmissions received from a plurality of remote units at a hub station comprising:

• means for transmitting a first data signal to a repeater from a first remote unit;
• means for receiving a copy of said signal as transmitted by said repeater at said first remote unit;
• means for determining a time difference between transmitting said signal and receiving said copy of said signal;
• and
• means for transmitting a second data signal using a timing advanced from a received time by a time increment, wherein said time increment is determined based upon said time difference.

An apparatus for time aligning transmissions received from a plurality of remote units at a hub station comprising:

• means for transmitting a first signal from a first remote unit to said hub station, said first signal advanced by time δt with respect to an on-time estimate;
• means for receiving a responsive advanced signal quality indication at said first remote unit from said hub station;
• means for sending a second signal from said first remote unit to said hub station, said second signal retarded by time δt with respect to said on-time estimate;
• means for receiving a responsive retarded signal quality indication at said first remote unit from said hub station;
• and
• means for advancing in time said on-time estimate if said responsive advanced signal quality indication indicates a better signal quality than said responsive retarded signal quality indication.

A apparatus for time aligning transmissions received from a plurality of remote units at a hub station comprising:

• means for transmitting a first signal from a first remote unit to said hub station, said first signal advanced by time δt with respect to an on-time estimate;
• means for determining an advanced signal quality indication at said hub station;
• means for sending a second signal from said first remote unit to said hub station, said second signal retarded by time δt with respect to said on-time estimate;
• means for determining a retarded signal quality indication at said hub station;
• and
• means for sending a command from said hub station to said remote unit to advance in time said on-time estimate if said advanced signal quality indication indicates a better signal quality than said retarded signal quality indication.

A apparatus for time aligning transmissions received from a plurality of remote units at a hub station comprising:

• means for receiving at a hub station an indication of actual time;
• means for transmitting a time tag transmission from said hub station to said plurality of remote units via a repeater, said time tag transmission indicating a time equal to said actual time offset by a current time delay estimate;
• means for receiving a copy of said time tag transmission from said repeater at said hub station;
• means for adjusting said current time delay estimate based upon the time at which said copy is received;
• and
• means for sending a subsequent time tag transmission based upon said adjusted current delay time estimate.