Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1998-06-30
2001-05-01
Chin, Wellington (Department: 2664)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S304000, C370S503000
Reexamination Certificate
active
06226284
ABSTRACT:
OBJECT OF THE INVENTION
This invention refers to a method for the remote, or distant, synchronization of a remote unit making use of a temporary reference defined by a SPS (Satellite Positioning System) system.
STATE OF THE ART
SPS devices according to the state of the art, for example those described in the U.S. Pat. No. 5,501,797 patent being included in this application through reference, receive signals transmitted by satellites and thereby determine a SPS clock pattern, for example a pattern of one pulse per second. To synchronize an unit which is at a distance from the SPS device, the European Telecommunications Standard ETS 300 175-2 , pages 38-44, published by the E.T.S.I. (European Telecommunications Standards Institute) on September 1996, describes a solution in which the clock pattern is transmitted to the remote unit via its own link, other than that employed for data transmission.
This solution, according to the state of the art, is difficult to implement in already existing systems in which there is only one data transmission link between the local and remote units.
CHARACTERIZATION OF THE INVENTION
An object of the invention is to define a synchronization method of a remote unit based on a SPS timing signal produced in a local unit, the two units being connected via a data link, synchronous or asynchronous with the SPS signal. In this data transmission link there is a free channel for the transmission of data relating to the SPS signal.
As a consequence, a synchronization method of a remote unit from a SPS timing signal produced in a local unit, this SPS timing signal having the form of successive pulses produced from signals received from satellites, is characterized in that it includes the following steps:
calculation in the local unit of an information representing the number of local clock cycles occurring from the appearance of a pulse until the moment when this information is injected into the data stream;
injection of said information into said data stream; and
generation in the remote unit of a synchronization signal related to the SPS signal, depending on this information.
To take into account the transmission delay time that occurs between the local and remote units, the method is characterized in that the synchronization stage depends also on a data transmission time between said local and remote units.
Additionally, the method includes a correction stage of the SPS signal generation in the remote unit which is a function of the frequency shift of the local clock with respect to the SPS timing signal in the local unit.
REFERENCES:
patent: 5600329 (1997-02-01), Brenner
patent: 6055021 (2000-04-01), Twitchell
patent: 6111541 (2000-08-01), Karmel
patent: 6144336 (2000-11-01), Preston et al.
Alcatel
Chin Wellington
Pham Brenda H.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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