Telecommunications – Carrier wave repeater or relay system – Portable or mobile repeater
Patent
1996-09-16
1999-04-27
Vo, Nguyen
Telecommunications
Carrier wave repeater or relay system
Portable or mobile repeater
455 132, H04B 7185
Patent
active
058989021
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the field of communication via satellite transponders, and more specifically, to a method of constructing a multi-station communications system with free access of subscribers through low-orbit satellites, a method of multiple-station communication with integration of low-orbit and high-orbit satellite systems, and a method of signal search end initial channel synchronization in the satellite communications system, and to apparatus for implementing these methods.
BACKGROUND ART
There are presently communications systems operating via satellite transponders located in a stationary or a high-elliptical orbit.
In the last few years, however, there is great interest in systems of personal communications with direct access by users and with low-orbit satellite transponders, which affords a drastic decrease in the energetics of radio lines and the use of small-size user stations. Such systems hold particular promise for personal communication with the users disposed on mobile objects or in hard-to-reach areas.
It is to be noted at the same time that the low-orbit satellite systems are extremely complicated because at a height of the satellite transponder in the order of 700 to 22000 km, there are considerable movements of the satellite transponder relative to users, resulting in high Doppler shifts of signal frequencies, and a short time period within which satellite transponders remain in the visibility range of the user consequently, complex equipment of satellite transponders and user stations must be used. Considerable problems arise in case it is required to establish continuous and stable communication of the users during any period of time.
Most known in the art are satellite communications systems with direct signal re-relaying by satellite transponders. A class of satellite communications systems is known in which a partial (or complete) processing of signals from the user stations is performed at the satellite transponders.
Systems are also known of the same class which ensure synchronization of not only the receivers of the user stations but their transmitters as well, which makes it possible to simplify the transponder process, which performs processing of signals from many user stations (G. I. Tuzov et al, "Interference immunity of radio systems with composite signals", edited by G. I. Tuzov, M., Radio i svyaz publishers, 1985, pp 130-132).
There are disclosures of a number of specific satellite low-orbit telephone communications systems. Thus, in the application of "Motorola satellite communication Inc." for the low-orbit communications system, "IRIDIUM" submitted to FCS , Washington, USA, 1990, by the inventors Golsky L. S., Malet F. I., Mutke A. M. is disclosed a communications system including 66 satellite transponders, which ensures global cellular personal telephone communications. This system is disadvantageous in that it has a low level of noise immunity and electromagnetic compatibility, which is defined by the shape of the simple signals used in the system and by the problems in implementing the specific in addition, the system suffers from cellular structure low level of privacy of talks without application of specialized means.
In the application of "Loral cellular systems, corp.," for the system "Globalstar " submitted to FCS , Washington, USA, 1991, by the inventors L. K. Smith, R. M. Halperin, L. A. Taylor, is disclosed another form of a low-orbit satellite communications system. This system is most close to the method of the present invention by the technical essence, shape of the signals used and the effect obtained. Both the method of the present invention and the prior-art method use wide-band pseudorandom phase-shift keyed signals.
Among the disadvantages of the prior-art method is the presence of regional stations providing for control of the communications system and switching of signal flows at satellite transponders, which, though simplifying the transponder design, results, however, in narrowing the area and time of
REFERENCES:
patent: 4375697 (1983-03-01), Visher
patent: 4532635 (1985-07-01), Mangulis
patent: 5471641 (1995-11-01), Dosiere et al.
Tuzov et al., "Interference Immunmity of Radio Systems with Composite Signals", Radio i Svyaz Publishers, pp. 130-157, 1985.
Application of Motorola Satellite Communications, Inc. to the Federal Communications Commission, Washington, District of Columbia, to construct IRIDIUM Low Earth Orbit Mobile Satelite Communication System, Dec. 1990.
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