Efficient communication system using time division multiplexing and timing adjustment control

In a communication system employing time division multiplexing, a method for establishing communication between a base station and a user station comprising the steps of

• transmitting from a base station, over a specified frequency band and during an initial portion of a time frame, a 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,
• transmitting from a user station seeking to establish communication with said base station, over said specified frequency band and during a user time slot in a user portion of said time frame, a reply message directed to said base station, said user time slot paired with said available base time slot,
• receiving at said base station said reply message,
• calculating a propagation delay at said base station based on a relative time of receiving said reply message and deriving a timing adjustment command thereby,
• transmitting from said base station, over said specified frequency band and during a subsequent time frame, a timing adjustment command to said user station,
• in response to said timing adjustment command, advancing or retarding a relative timing of subsequent user-to-base messages from said user station to said base station by an amount specified by said timing adjustment command.

A method for carrying out time division multiplexed communication between a base station and a plurality of user stations over a single frequency band, comprising the steps of

• transmitting, during a base portion of a time frame, a base station burst over a designated frequency band, said base station burst comprising a plurality of time intervals corresponding to base time slots, wherein either a base-to-user message or a general polling message is transmitted in each of said base time slots, said base-to-user message being transmitted in the base time slots already in use for established communication with user stations, and said general polling message being transmitted in the base time slots available for communication,
• receiving in user time slots, during a user portion of said time frame and over said designated frequency band, a user-to-base message in the user time slots already in use for established communication with said base station, and a reply message in the user time slots in which a new user station is attempting to establish communication with said base station, and
• periodically transmitting from said base station, over said designated frequency band, a timing adjustment command to at least one of said user stations, whereby subsequent user-to-base messages from said user station are advanced or retarded in time by an amount specified by said timing adjustment command.