Multiplex communications – Duplex – Communication over free space
Patent
1995-05-01
1997-05-06
Safourek, Benedict V.
Multiplex communications
Duplex
Communication over free space
370330, 379 58, H04B 7212
Patent
active
056278233
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a wire-free telecommunications system, preferably a cordless telecommunications system having a plurality of base stations and mobile elements.
In wire-free telecommunications systems--such as mobile radio or cordless telecommunications systems for example--having a plurality of base stations and mobile elements which form telecommunications subsystems and use, for example, the time division multiple access method TDMA (Time Division Multiple Access) or the code division multiple access method CDMA (Code Division Multiple Access), optimum channel utilization in the telecommunications subsystems (in the sense of no mutual interference between the channels in the telecommunications subsystems) can be achieved only if the telecommunications subsystems, which are based, for example, on the TDMA principle, are synchronized (no drift between the time bases of the telecommunications subsystems) (synchronous wire-free telecommunications system).
In asynchronous wire-free telecommunications systems, in contrast, in which drift occurs between the time bases of the telecommunications subsystems, mutual interference between the channels of the telecommunications subsystems can occur as a result of the drift of the time bases, which interference severely reduces the overall channel selection which can be used in the respective telecommunications subsystem in unfavorable cases.
SUMMARY OF THE INVENTION
The object on which the invention is based is to specify a wire-free telecommunications system, preferably a cordless telecommunications system of the type mentioned initially, in the case of which there is no mutual interference between telecommunications subsystems.
This object is achieved by a wire-free telecommunications system, preferably a cordless telecommunications system, having a plurality of base stations and mobile elements which each form a wire-free telecommunications subsystem. The base stations and the mobile elements respectively have a circuit arrangement to which is assigned a controlling program. The controlling program is designed such that radio links take place at predetermined frequencies (Frequency Division Multiple Access FDMA) and in a plurality of time slots in time-division multiplex channels (Time Division Multiple Access TDMA). The controlling program is furthermore designed such that only a subset of time slots, which do not directly follow one another, is selected from a number of predetermined time slots for the radio links.
It can be regarded as being essential to the invention in this case that only a subset of the time slots which are available overall in the telecommunications subsystems of the wire-free telecommunications system (for example every other time slot) is used. In consequence, the usable channel capacity of the wire-free telecommunications subsystem or telecommunications system is admittedly reduced, but the reduced channel capacity is preferably not less if, to be precise, all the time slots which are available in the telecommunications subsystems are used, but only half of these are available, rather than all of them, because of interference in which a channel a of a telecommunications subsystem A interferes with two channels b1, b2 of a telecommunications subsystem B.
In an advantageous development of the invention only every other time slot is selected from the number of predetermined time slots for the radio links.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several Figures of which like reference numerals identify like elements, and in which:
FIG. 1 shows the outline of the construction of a base station or of a mobile element of a cordless telecommunications subsystem,
FIG. 2 shows a TDMA time frame of a cord
REFERENCES:
patent: 4525835 (1985-07-01), Vance et al.
patent: 5134710 (1992-07-01), Akerberg
patent: 5291475 (1994-03-01), Bruckert
patent: 5371780 (1994-12-01), Amitay
patent: 5440544 (1995-08-01), Zinzer, Jr.
"Auch ohne Schnue >>auf Draht<<", Klaus Wolf, Siemens AG, Telcom report 10 (1987), pp. 130-137, in particular, pp. 134 and 135.
"Digital European Cordless Telecommunications System" (DECT) Standard (draft prETS 300 175-1) pp. 1-31 Aug. 1991.
"Digital European Cordless Telecommunications System" (DECT) Standard (draft prETS 300 175-2) pp. 1-36 Aug. 1991.
"Digital European Cordless Telecommunications System" (DECT) Standard (draft prETS 300 175-3) pp. 1-177 Aug. 1991.
Safourek Benedict V.
Siemens Aktiengesellschaft
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