DIGITAL ADAPTOR FOR RADIO SUBSCRIBER TERMINALS

Abstract: Disclosed is a cordless terminal adapter designed to link a plurality of subscriber terminals by RF means with a base station of the telephone network. This adapter is of the type comprising a subscriber interface linked with the subscriber terminals, a DECT interface to convert the signals coming from the subscriber interface into DECT signals and, conversely, means for the transmission and reception of said DECT signals and an antenna. Its subscriber interface is constituted by a plurality of independent interface modules communicating with the DECT interface. Each interface module is designed for the connection of a subscriber terminal to the DECT interface. Application to the field of public or private networks with high user capacity.

Description: BACKGROUND OF THE INVENTION The present invention relates to a cordless terminal adapter or CTA, namely an interface device designed for communication, on the one hand by RF means with a base station linked to a standard telephone network and, on the other hand, by radio links or wire links with subscriber terminals (analog or digital telephones, facsimile machines, modems, NUMERIS interfaces, DECT sets, etc.). The invention can be applied especially in the field of public or private wireless links, with low or high density of users. In general, these adapters communicate with the base station of the telephone network by means of digital signals in accordance with the digital European cordless telephony (DECT) standard. The frequency band used in systems working according to the DECT standard ranges from 1880 to 1900 Mhz. For the widebands, it ranges from 1900 to 1920 MHz or from 1910 to 1930 MHz. This band is subdivided into ten carrier frequencies with a frame structure for each of them according to the frequency division multiple access (FDMA) technique. Each carrier is divided into 24 time intervals, of which 12 are used for transmission from the adapter to the base station while the other 12 are used for transmission from the base station to the adapter. This method takes the capacity of the system to 120 channels, each adapter being capable of transmitting on each of the channels and simultaneously on 12 of them. This type of adapter generally comprises: - a subscriber interface linked with subscriber terminals; this subscriber interface may be a conventional telephone interface for the connection of the telephones, facsimile machines or modems, a digital interface, an interface for the connection of modems at high bit rates, an ATM interface for the transfer of data packets in asynchronous mode, an ISDN interface for the connection of ISDN terminals or, quite often, a combination of these devices; - a DECT interface responsible for obtaining matching between the DECT protocol and the signalling commands of the subscriber interface as well as the adaptive differential PCM (AD-PCM) transcoding; and - means for the transmission and reception of these DECT signals as well as an antenna to set up an RF link with the base station of the telephone networks . All these means are generally brought together in a single pack. The antenna may, if necessary, be may be separated from the pack and placed at a distance in a place more suitable for it to be aimed at the base station. This pack therefore contains an electronic unit that is customized according to the needs of the subscriber (this is the subscriber interface) and an electronic unit common to all the adapters. These are the transmission/reception means and the DECT interface. This bringing together of electronic circuits, where some are customized and the others are not, in a single pack has a major drawback. When the subscriber decides to modify his telephone installation, for example by adding an ISDN terminal or an additional telephone line, he is forced to modify or change his adapter. This entails a certain cost. SUMMARY OF THE INVENTION The present invention seeks to overcome this drawback of the prior art by proposing a cordless terminal adapter that is more open-ended. Thus, according to the invention, the adapter takes a modular form. It comprises a module common to all the adapters and a plurality of interface modules each enabling the connection of a terminal to the telephone network. In the event of the addition of a terminal, all that needs to be done is to add the corresponding interface module and connect it to the common module of the adapter. An object of the invention therefore is a cordless terminal adapter designed to link a plurality of subscriber terminals by RF means to a base station of the telephone network, the signals exchanged between said base station and said cordless terminal adapter being DECT digital signals, said adapter being of the type comprising a subscriber interface linked with the subscriber terminals, a DECT interface to convert the signals coming from the subscriber - interface into DECT signals and, conversely, means for the transmission and reception of said DECT signals and an antenna, wherein the subscriber interface consists of a plurality of independent interface modules communicating with the DECT interface, each interface module being designed for the connection of a subscriber terminal to the DECT interface. Each interface module has an interface circuit designed for the connection of a subscriber terminal, for example an ISDN interface circuit for the connection of an ISDN terminal and a telephone interface circuit for the connection of an analog telephone station. The interface modules are connected to the DECT interface of the adapter, either by means of a digital communications bus or by RF link. Preferably, the DECT interface and the transmission and reception means are placed together in a processing module, and the antenna of the adapter is detachable and may or may not be placed at a distance from this module. BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention shall appear from the following detailed description made with reference to the appended drawings, of which: - Figure 1 shows a first embodiment ' of a cordless terminal adapter according to the present invention, - Figure 2 shows a second embodiment of a cordless terminal adapter according to the present invention. MORE DETAILED DESCRIPTION According to the invention, the subscriber interface of the cordless terminal adapter consists of a plurality of interface modules, each designed for the connection of a terminal to the telephone network. The adapter therefore has as many interface modules as there are terminals to be connected to the telephone network. In figure 1, the cordless terminal adapter 1 has two interface modules 2 and 3 connected by a communications bus 4 to a processing module 5 comprising a DECT interface 6 and means 7 for the transmission and reception of DECT signals. In technical language, the interface modules are sometimes designated by the abbreviation ATS (active terminal socket) and the processing module is designated by the abbreviation CTU (cordless terminal unit) . In the example of the figure 1, the interface modules 2 and 3 are designed respectively to connect a standard analog telephone 8 and an ISDN terminal 9. To this end, the interface modules 2 and 3 respectively comprise a standard telephone interface 10 and an ISDN interface 11. If the subscriber wishes to add an additional telephone line to connect a telephone, a fax machine or a modem, it is enough to provide for an additional interface module identical to the module 2 and connect it to the processing module of the adapter. Thus, unlike the prior art adapters, the subscriber interface does not have to be customized in the factory. Similarly, for the connection of a digital telephone, it will be enough to provide for an interface module comprising -a digital interface. This elimination of the customization of the subscriber interface has advantages for the manufacturer (at the production level) and for the subscriber who pays only for the additional interface modules when his or her telephone installation is modified. The communications bus 4 is for example a time- shared digital bus capable of simultaneously transferring up to six telephone calls encoded at 64 Kbit/s. The adapter may then comprise up to six interface modules. The plurality of interface modules and the communications bus are managed by the processing module 5. Naturally, for a different encoding factor, for example 32 Kbit/s, the communications bus could simultaneously transfer a larger number of telephone calls. The adapter will then comprise at most a number of interface modules corresponding to the maximum number of simultaneous calls possible. Advantageously, each interface module has its own power supply circuit. In this way, the interface modules are completely independent. In the example of the single figure, power supply circuits 12 and 13 are designed to supply respectively the telephone interface 10 and the ISDN interface 11. These power supply circuits will also contribute to supplying the processing module 5 of the adapter by means of the communication bus 4. The task of supplying the common module 5 is therefore carried out by all the interface modules of the adapter. Each of the n interface modules gives 1/n of the current needed to supply the module 5. The power supply circuits of the interface modules are, for example, switching supply type circuits. A non-return diode internal to each interface module protects these modules and makes it possible to obtain a power supply that is stable in voltage. The regulation of the current at output is done automatically as a function' of the number of modules connected. Furthermore, the processing module 5 is connected to a directional antenna 14 connected by RF means to a base station 15 of the telephone network which is itself connected to the standard telephone network by an automatic branch exchange 16. This antenna may or may not be kept at a distance from the processing module 5. The processing module 5 is responsible for converting the signals coming from the interface modules into DECT signals and the DECT signals coming from the antenna 14 into signals that can be used by the interface modules . The DECT interface 6 and the transmission and reception means 7 are powered by a DC/DC converter 17 which is itself powered by the power supply circuits of the different interface modules. In one improved version, the processing module 5 may also be used as a telephone repeater for DECT telephone handsets. The processing module 5 then comprises two omnidirectional antennas to communicate with the handsets and installations of a standard radio terminal DECT. According to an improved embodiment, each interface module is provided with an electronic key so as to attach an interface module to a specific processing module and thus prevent the interface module from being re-used with another processing module, for example, in the event of theft. A alternative to the embodiment of figure 1 is proposed in Figure 2. In this alternative, the interface modules 2 and 3 are connected by RF links to the DECT interface 6. To this end, the interface modules 2 and 3 are each provided with a transceiver, respectively 18 and 19, and two omnidirectional antennas. In the same way, the DECT interface 6 is provided with an additional transceiver 20 and two omnidirectional antennas. The transceivers 18 and 19 are supplied with power by the power supply devices of the modules 2 and 3. In this alternative embodiment, the processing module 5 is no longer supplied by the interface modules but has its own power supply device 21 connected to the DC/DC interface 17. This alternative embodiment permits a more dynamic management of communications. Indeed, each interface module is, at the minimum, connected by radio to a processing module. Should a processing module be overloaded, each interface module may be assigned to the processing module of another adapter so as to let all the calls go through. The present invention has been described with known interface circuits (standard telephone interfaces, ISDN interfaces, etc.). Nevertheless, it is quite clear that the use of other types of interface (for example specific interfaces for data transfer) would not go beyond the scope of the invention.

Claims: WHAT IS CLAIMED IS: 1. A cordless terminal adapter designed to link a plurality of subscriber terminals by RF means to a base station of the telephone network, the signals exchanged between said base station and said cordless terminal adapter being DECT digital signals, said adapter being of the type comprising a subscriber interface linked with the subscriber terminals, a DECT interface to convert the signals coming from the subscriber interface into DECT signals and, conversely, means for the transmission and reception of said DECT signals and an antenna, wherein the subscriber interface consists of a plurality of independent interface modules communicating with the DECT interface, each interface module being designed for the connection of a subscriber terminal to the DECT interface. 2. A cordless terminal adapter according to claim 1, wherein each interface module is connected to the DECT interface by means of a digital communications bus. 3. A cordless terminal adapter according to claim 2, wherein each interface module has its own power supply device, each power supply device contributing to the supply of the DECT interface and of the transmission and reception means of the adapter. 4. A cordless terminal adapter according to claim 1, wherein each interface module is connected to the DECT interface by RF links. 5. A cordless terminal adapter according to claim 4, wherein the interface modules and the DECT interface each have their own power supply device. 6 A cordless terminal adapter according to claim 4 or 5 wherein, if it is overloaded, at least one of its interface modules can communicate with the DECT interface of another adapter. 7 A cordless terminal adapter according to one of the claims 1 to 6, wherein the DECT interface and the means for the transmission and reception of the DECT signals are brought together in a processing module, it being possible for the antenna of the adapter to be separated or not separated from this module. 8. A cordless terminal adapter according to one of the claims 1 to 7, wherein each interface module comprises an electronic key.

Inventors: CARMINE ARMAND, DAULASIM KHAMPHUC, LELONG PATRICK, CARMINE, ARMAND, DAULASIM, KHAMPHUC, LELONG, PATRICK
Applicants: CARMINE ARMAND, DAULASIM KHAMPHUC, LELONG PATRICK, LUCENT TECHNOLOGIES INC, CARMINE, ARMAND, DAULASIM, KHAMPHUC, LELONG, PATRICK, LUCENT TECHNOLOGIES INC.
Application year: 1999
Main classification: H04Q7
IPC codes: H04W84