US 6,388,997 B1 · Timing adjustment control for efficient time division duplex communication

Abstract

A system and method for time division duplex communication over a single frequency band wherein guard time overhead is reduced by active adjustment of reverse link transmission timing as a function of round trip propagation time. A time frame is divided into a plurality of time slots, during each of which the base station transmits to a user station and the user station transmits to the base station. Communication is initiated by a round trip timing transaction. In response to a general polling message from the base station, a user station seeking to establish communication transmits a short reply message. The base station calculates the distance of the user station by measuring the propagation delay with respect to receipt of the reply message. The base station sends a timing adjustment command to the user station instructing the user station to advance or retard its timing according to the calculated distance, so as to minimize guard times between time slots. Thereafter, the base station monitors the user station transmissions and periodically commands the user station to advance or retard its timing in a like manner. The user station may transmit a control preamble at the start of each time slot to allow the base station to perform round trip timing calculations, and/or to allow adjustment or user station power or antenna selection.

Claims28

Dependent claims

A system for communicating with a plurality of user stations, comprising:

a base station;
a transmission format;
said transmission format comprising a plurality of time frames of equal duration, each of said time frames comprising a base transmission portion, a collective guard portion, and a user transmission portion, said collective guard portion located between said base transmission portion and said user transmission portion, each base transmission portion comprised of a plurality of base time slots and each user transmission portion comprised of a plurality of user time slots;
said base station comprising a base station transmitter for transmitting a polling message from the base station to two or more of the plurality of said user stations in a base time slot of a first of said time frames, said base station comprising a base station receiver for receiving a reply message from at least one of said two or more user stations during the collective guard band portion of said first time frame;
a propagation delay calculator, said propagation delay calculator comprising the capability to determine a propagation delay between said base station and said at least one user station;
and
said base station transmitter further for transmitting a timing command during the base transmission portion of a time frame subsequent to the first time frame to the at least one user station for instructing the at least one user station to adjust the transmission time of the at least one user station, the timing command based at least in part on said propagation delay.

4 more elements

A system for communicating with a plurality of user stations, comprising:

a base station;
a transmission format;
said transmission format comprising a plurality of time frames of equal duration, each of said time frames comprising a base transmission portion, a collective guard portion, and a user transmission portion, said collective guard portion located between said base transmission portion and said user transmission portion, each base transmission portion comprised of a plurality of base time slots and each user transmission portion comprised of a plurality of user time slots;
said base station comprising a base station transmitter for transmitting a polling message from the base station to two or more of the plurality of said user stations in a base time slot of a first of said time frames,
said base station comprising a base station receiver for receiving a reply message from the at least one of said two or more user stations during one of said user time slots of said first time frame;
a propagation delay calculator, said propagation delay calculator comprising the capability to determine a propagation delay between said base station and said at least one user station;
and
said base station transmitter further for transmitting a timing command during the base transmission portion of a time frame subsequent to said first time frame to the at least one user station for instructing the at least one user station to adjust the transmission time of the at least one user station, the timing command based at least in part on said propagation delay.

5 more elements

In a base station, a method for communicating with a plurality of user stations, comprising:

using a transmission format comprising a plurality of time frames of equal duration, each of said time frames comprising a base transmission portion, a collective guard portion, and a user transmission portion, said collective guard portion located between said base transmission portion and said user transmission portion, each base transmission portion comprised of a plurality of base time slots and each user transmission portion comprised of a plurality of user time slots;
transmitting a polling message from the base station to two or more of the plurality of said user stations in a base time slot of a first of said time frames,
receiving a reply message from at least one of said two or more user stations during the collective guard band portion of said first time frame;
determining a propagation delay between said base station and said at least one user station;
and
transmitting a timing command during the base transmission portion of a time frame subsequent to said first time frame to the at least one user station for instructing the at least one user station to adjust the transmission time of the at least one user station, the timing command based at least in part on said propagation delay.

3 more elements

In a base station, a method for communicating with a plurality of user stations, comprising:

using a transmission format comprising a plurality of time frames of equal duration, each of said time frames comprising a base transmission portion, a collective guard portion, and a user transmission portion, said collective guard portion located between said base transmission portion and said user transmission portion, each base transmission portion comprised of a plurality of base time slots and each user transmission portion comprised of a plurality of user time slots;
transmitting a polling message from the base station to two or more of the plurality of said user stations in a base time slot of a first of said time frames,
receiving a reply message from the at least one user station during one of said user time slots of said first time frame;
determining a propagation delay between said base station and said at least one user station;
and
transmitting a timing command during the base transmission portion of a time frame subsequent to said first time frame to the at least one user station for instructing the at least one user station to adjust the transmission time of the at least one user station, the timing command based at least in part on said propagation delay.

3 more elements

Dependencies are inferred from the claim text.

Timing adjustment control for efficient time division duplex communication

Life of this patent

Timing adjustment control for efficient time division duplex communication

Life of this patent

Abstract

Claims28