Timing adjustment control for efficient time division duplex communication

A method of time duplex communication between a base station and a plurality of user stations over a single frequency band, wherein said base station communicates sequentially during a time frame with the user stations in established communication with said base station, and wherein said time frame is divided into a plurality of time slots of equal duration, said method comprising the steps of

• transmitting, over a designated frequency band, during a designated time slot, a first base-to-user message from said base station to a user station,
• receiving at said base station, during said designated time slot in said first time frame and over said designated frequency band, a first user-to-base message from said user station,
• transmitting, during said designated time slot in a second time frame subsequent to said first time frame and over said designated frequency band, a second base-to-user message from said base station to said user station, said second base-to-user message comprising a timing adjustment command, and
• receiving at said base station, during said designated time slot in said second time frame and over said designated frequency band, a second user-to-base message from said user station, said second user-to-base message advanced or retarded in time in response to said timing adjustment command, wherein said user station maintains a timing parameter relative to a fixed reference, and wherein said timing adjustment command modifies said timing parameter in order to advance or retard said timing of said second user-to-base message.

A system for carrying out time division duplex communication between a base station and a plurality of user stations over a single frequency band, said system comprising

• a plurality of time frames, and
• a plurality of time slots in each of said time frames, each of said time slots comprising
• a base message interval during which a base message may be sent over a predetermined frequency band by a base station to a user station in established communication with said base station, and
• a user message interval during which a user message may be sent over said predetermined frequency band to said base station by said user station in established communication with said base station,
• wherein said base station periodically transmits, during said base message interval, a timing adjustment command to said user station in established communication with said base station, wherein said user station maintains a timing parameter relative to a fixed reference, and wherein said timing adjustment command modifies said timing parameter in order to advance or retard a timing of said user station.

A method for establishing time division duplex communication between a base station and a user station over a single frequency band, wherein said base station communicates sequentially during a time frame with user stations in established communication with said base station, and wherein said time frame is divided into a plurality of time slots of equal duration, said method comprising the steps of

• transmitting, over a designated frequency band and during a first base interval of an available time slot in a first time frame, a general polling message,
• plurality of base-to-user messages directed to user stations with which said base station has previously established communication, said initial portion comprising a plurality of base time slots, wherein each of said base-to-user messages corresponds to a different base time slot and at least one of said base time slots is available for communication,
• receiving, over said designated frequency band and during a user interval of said available time slot, a reply message from a user station,
• calculating at said base station, based on the time of receiving said reply message at said base station, a distance of said user station relative to said base station, and
• transmitting, over said designated frequency band and during a second base interval of said available time slot in a second time frame, a base message from said base station directed to said user station, said base message comprising a timing adjustment command whereby timing of a subsequent message from said user station directed to said base station over said designated frequency band is advanced or retarded, wherein said user station maintains a timing parameter relative to a fixed reference, and wherein said timing adjustment command modifies said timing parameter in order to advance or retard said timing.