WO1995029569A1

WO1995029569A1 - Telephone installation with digital transmission line and reduced flow rate

Info

Publication number: WO1995029569A1
Application number: PCT/FR1994/000464
Authority: WO
Inventors: Joël SOUPIROT
Original assignee: Dassault Automatismes Et Telecommunications
Priority date: 1993-04-21
Filing date: 1994-04-22
Publication date: 1995-11-02
Also published as: FR2704378B1; FR2704378A1

Abstract

The telephone installation comprises a plurality of fixed telephone sets (TT-i), a telephone communication network (RTC), and fixed connection and management means (MFG), having direct connection means (AD) to the telephone communication network (RTC). Reduced flow rate elementary transmission lines (LE-i) are each arranged between a fixed telephone set and the fixed connection and management means, if necessary through a grouping unit. The fixed connection means comprise a plurality of coding/decoding means (20-i) for restoring and reciprocally receiving the elementary voice (BE-i) and signalling (Dei) channels; multiplexing/demultiplexing means between the plurality of elementary voice channels; and means (40) for receiving the elementary signalling channels in order to control access to the communication network.

Description

Telephone installation with reduced speed digital transmission line.

The invention relates to a telephone installation with a reduced speed digital transmission line.

It finds an application in the connection of fixed telephone terminals.

Given the current evolution of telephony, certain fixed telephone terminals intended to be connected to telephone communication networks must now ensure, in addition to the telephone link, the data transmission allowing the supervision of said link, in particular for operations access control or payment (for example for payphones with payment cards).

Most often, these fixed telephone terminals are connected to a connection unit itself ensuring the connection of said terminals to the telephone communication network and to the data transmission network.

According to a first known solution, the connection between the fixed telephone terminal and the connection unit is of the analog type and uses a technique called "supravocal" making it possible to transmit control data over the telephone band.

Such a solution has the disadvantage of being costly and of conferring a short transmission range due in particular to the strong attenuation of the useful signal in supravocal transmission.

Another known solution consists in using a digital transmission of voice signals associated with control data such as that carried out by digital networks. with integration of ISDN services (Registered trademark) of FRANCE TELECOM.

However, this type of link implements high bit rates of the order of a few hundred Kbits per second, which is not economically satisfactory for isolated terminals requiring only reduced bit rates of the order of a few tens of Kbits.

The invention overcomes this drawback.

Thus, a first object of the invention is to provide a telephone installation with fixed telephone terminals each connected by a digital transmission link at a reduced speed, to fixed connection and management means, if necessary via a grouping unit. .

Another object of the invention is to provide a telephone installation in which the management and control of telephone communications are transferred to the fixed connection and management means.

According to a general definition of the invention, the telephone installation comprises:

- a plurality of fixed telephone terminals;

- a telephone communication network;

- fixed connection and management means having direct connection means to the telephone communication network for the circulation of voice information between the telephone terminals and the fixed connection and management means;

a plurality of elementary transmission lines each disposed between a fixed telephone terminal and the fixed connection and management means, each elementary transmission line being capable of carrying at least an elementary voice channel and an elementary signaling channel according to a bidirec¬ tional elementary temporal framing in alternation predetermined and at reduced rate;

fixed connection and management means including:

* a plurality of elementary line interfaces on the management side respectively with an elementary transmission line;

* a plurality of coding / decoding means of elementary frames on the management side connected respectively to an elementary line interface on the management side, and capable of each performing a bidirectional conversion of frames to restore and vice versa receive the elementary voice and signaling channels;

* elementary multiplexing / demultiplexing means on the management side connected between the plurality of coding / de¬ coding means of elementary frames on the management side and the direct connection means, and capable of operating bidirectionally multiplexing / demultiplexing between the plurality of voice channels elementary and an elementary multiplex voice channel, to allow the exchange of voice information between the direct connection means and the plurality of coding / decoding means of elementary frames on the management side, and

* elementary processing means on the management side connected to the plurality of coding / decoding means of elementary frames on the management side in order to receive the elementary signaling channels capable of maintaining a dialogue between the plurality of telephone terminals and the fixed connection means and management to control access to the telephone communication network and supervise telephone communications.

Such an installation allows fixed telephone terminals to be connected to fixed connection and management means, which has the advantage of being implemented very little. expensive and far-reaching thanks to the use of basic digital transmission lines at reduced speed. In addition, the management and control of telephone communications are deported to the fixed connection and management means.

It finds an advantageous application in the connection of isolated fixed terminals at reduced speed, such as payphones, simple or advanced telephone sets using a reduced speed.

The term “reduced bit rate” is understood here to mean a bit rate capable of supporting an elementary voice channel and an elementary signaling channel.

Telephone terminals can also be connected via grouping units remote from terminals and fixed connection and management means.

In this case, according to the invention, the telephone installation comprises:

- a plurality of fixed telephone terminals;

- a telephone communication network;

- at least one grouping unit;

a plurality of elementary transmission lines each disposed between a fixed telephone terminal and the grouping unit, each elementary transmission line being capable of carrying at least one elementary voice channel and one elementary signaling channel according to an elementary bidirectional time framing alternating predetermined and reduced flow;

the grouping unit comprising: * a plurality of elementary line interfaces on the unit side respectively with an elementary transmission line;

* a plurality of coding / decoding means of elementary frames on the unit side respectively connected to an elementary line interface on the unit side, and capable of each effecting a bidirectional conversion of frames to restore and reciprocally receive the elementary voice and signaling channels;

* at least one main transmission line capable of carrying at least one main voice channel consisting of elementary voice channels and one main signaling channel consisting of elementary signaling channels according to a predetermined bidirectional time main framing;

* at least one main line interface on the unit side with the main transmission line; and

* main multiplexing / demultiplexing means on the unit side capable of operating bidirectionally a multiplexing / - demultiplexing between on the one hand the plurality of elementary voice and signaling channels and on the other hand elementary multiplex voice and signaling channels;

* means for coding / decoding main frames on the unit side connected between the main multiplexing / demulti¬ plexing means on the unit side and the main line interface on the unit side, and suitable for performing bidirec¬ tional conversion of frames and ensuring a correspondence between 'a part between the signaling information contained in the elementary multiplex signaling channel. and in the main signaling channel, and on the other hand between the voice information contained in the elementary multiplex voice channel and in the main voice channel, to allow the exchange of voice and signaling information between the various elementary transmission lines and the main transmission line; - Fixed connection and management means having direct connection means to the telephone communication network for the circulation of voice information between the telephone terminals and the fixed connection and management means, said fixed connection and connection means management including:

* at least one main line interface on the management side with the main transmission line; and

* means for coding / decoding main frames on the management side connected to the main line interface, and capable of performing a bidirectional conversion of frames to restore and vice versa receive the main voice and signaling channels; and

* main processing means on the management side connected to the coding / decoding of main frames on the management side to receive the main signaling channel and suitable for maintaining a dialogue with the grouping unit via the main signaling channel to control access to the telephone communication network and supervise telephone communications.

Such an installation thus makes it possible to provide a connection of fixed telephone terminals to fixed connection and management means via the grouping unit, which has the advantage of being inexpensive and far-reaching thanks to the use of basic digital transmission lines at reduced speed. In addition, the management and control of telephone communications are deported to the level of fixed connection and management means.

In practice, the installation comprises several grouping units and several main transmission lines each connected between a grouping unit and the fixed connection and management means. In this case, the fixed connection and management means further comprise;

- a plurality of main line management side interfaces each connected with a main transmission line;

a plurality of coding / decoding means of main frames on the management side each connected to a main line interface, and

- main multiplexing / demultiplexing means on the management side connected between the plurality of coding / de¬ coding means of main frames on the management side and the direct connection means, and capable of operating bidirectionally a multiplexing / demultiplexing between the plurality of voice channels main and a main multiplex voice channel, to allow the exchange of voice information between the direct connection means and the coding / decoding means of main frames on the management side.

Preferably, each fixed telephone terminal comprises:

- an elementary line interface on the terminal side with an elementary transmission line at reduced speed;

- means for coding / decoding elementary frames on the terminal side connected to the elementary line interface on the terminal side, and capable of performing bidirectional conversion of frames to restore and vice versa receive the elementary voice and signaling channels;

- means for coding / decoding speech connected to the means for coding / decoding elementary frames on the terminal side and suitable for carrying out a bidirectional conversion of speech to decode the channel from elementary voice to speech and conversely coding speech into a channel for elementary voice; and - data processing means on the terminal side connected to the coding / decoding means of elementary frames on the terminal side and capable of performing data processing to code the data into an elementary signaling channel and conversely decode an elementary signaling channel into data.

Preferably, the useful bit rate of each elementary transmission line is of the order of 68 Kbits per second with 64 Kbits per second allocated to the elementary voice channels and 4 Kbits per second allocated to the elementary signaling channels.

In addition, the wired connection of telephone terminals can prove to be difficult to implement because of the drawbacks linked to cable placement, especially in difficult or unsuitable environment due to the varying needs in time of telephone traffic (manifesta¬ such as the Olympic Games, holiday resorts).

Radiofrequency digital links are known which make it possible to eliminate cables and which provide flexibility in telephone services.

The Applicant has posed the problem of using the installation as referred to above and supplementing it with characteristics based on radiofrequency transmission / reception means when the environment of the installation presents for example the aforementioned drawbacks.

Thus, the installation according to the invention further comprises:

- a plurality of autonomous telephone sets with radiofrequency emission / reception;

- at least one fixed terminal comprising:

* a radiofrequency transmission / reception interface on the terminal side capable of operating according to a plurality of radiofrequency channels capable of each carrying at least one elementary radiofrequency voice according to a predetermined elementary time framing, to allow the exchange of voice and signaling information with the telephones;

* a terminal-side line interface with a main transmission line, the other end of which is connected to the fixed connection and management means described above and which is capable of carrying at least one main voice channel and one main signaling according to a predetermined bidirectional time main framing; and

* terminal side processing means comprising:

. multiplexing / demultiplexing means on the terminal side capable of operating bidirectionally multiplexing / demuliplexing between, on the one hand, the plurality of elementary radiofrequency voice channels and elementary radiofrequency signaling channels and, on the other hand, a channel of elementary multiplex voice and an elementary multiplex signaling channel; and

. terminal side frame coding / decoding means connected between the terminal side multiplexing / demultiplexing means and the terminal side line interface, and suitable for performing bidirectional frame conversion and ensuring correspondence, on the one hand between the information of signaling contained in the elementary multiplex signaling channel and in the main signaling channel, and on the other hand between the voice information contained in the elementary multiplexed voice channel and in the main voice channel, to allow the exchange of information voice and signaling between the main transmission line and the different radio frequency channels allocated to the different autonomous telephone sets in telephone communication with the telephone communication network; the main processing means on the management side described above being suitable for maintaining a dialogue with the fixed terminal via the main signaling channel for manage the allocation of radio frequency channels and control telephone communications.

In practice, each autonomous radio transmission / reception telephone set includes:

- a radio frequency transmission / reception interface on the station side;

- means for coding / decoding elementary frames on the station side, connected to the radio frequency transmission / reception interface on the station side, and suitable for performing bidirectional frame conversion to restore and reciprocally receive the radiofrequency elementary voice channels;

- speech coding / decoding means connected to the coding / decoding of elementary frames on the station side and suitable for carrying out bidirectional speech conversion to decode the elementary radio frequency channel into speech and conversely coding speech into a channel elementary radiofrequency voice; and

- station side data processing means connected to the station side frame coding / decoding means and suitable for performing data processing to encode data into an elementary radio signaling channel, and conversely decode an elementary radio signaling channel in data.

For example, stand-alone telephones are telephones of the public phone type.

Other characteristics and advantages of the invention will become apparent in the light of the detailed description below and of the drawings in which:

- Figure 1 is a schematic representation of a telephone installation in which the telephone terminals are connected to the fixed connection means and management through elementary transmission lines at reduced speed according to the invention;

Figure 2 is a schematic representation of a fixed telephone terminal according to the invention;

FIG. 3 is a schematic representation of a telephone installation in which the fixed telephone terminals are connected to a grouping unit through elementary digital transmission lines at reduced speed according to the invention;

- Figure 4 is a schematic representation of the structure of the binary data transmitted by the elementary transmission lines according to the invention;

- Figures 5A and 5B are schematic representations of the structure of binary data transmitted by the main transmission lines according to the invention;

- Figure 6 is a schematic representation of an installation of Figure 3 supplemented by a radio frequency branch according to the invention;

- Figure 7 is a schematic representation of the essential elements of a terminal according to the invention; and

- Figure 8 is a schematic representation of an autonomous telephone set according to the invention.

In FIG. 1, the architecture of the telephone installation according to the invention is articulated around fixed connection and management means MFG having direct connection means AD to the telephone communication network PSTN for the circulation of voice information between the plurality of fixed telephone terminals TT-i individualized in TT-1 to TT-3 and the fixed means of connection and management MFG. The whole number has a value here between 1 and 3, by way of explanation but not limitation.

According to the invention, there is provided a plurality of elementary transmission lines LE-i at reduced speed individualized in LE-1 to LE-3, and each arranged between a fixed telephone terminal TT-i and the fixed means of connection and MFG management.

Each elementary transmission line LE-i is capable of carrying at least one elementary voice channel BE-i and one elementary signaling channel DE-i according to a predetermined alternating bidirectional time elementary framing which will be described in more detail below. after (figure 4).

According to the fixed means of connection and management MFG, it is provided according to the invention:

- A plurality of elementary line interfaces management side 10-i respectively with a LE-i silenced transmission line;

a plurality of coding / decoding means of elementary frames on the management side 20-i, connected respectively to an elementary line interface 10-i. These coding / decoding means 20-i are each capable of performing a bidirectional conversion of frames in order to restore and vice versa receive the elementary voice channels BE-i and signaling signals DE-i;

- Multiplexing / demultiplexing means 30 on the management side connected between the plurality of coding / decoding means of elementary frames 20-i and the direct connection means AD. These multiplexing / demultiplexing means 30 are capable of operating bidirectionally a multiplexing / demultiplexing between the plurality of elementary voice channels BE-i and one elementary multiplex voice channel BME to allow the exchange of voice information between the means of direct connection AD and the plurality of coding / decoding means of elementary frames 20-i; and

- elementary processing means on the management side 40 connected to the plurality of frame coding / decoding means 20-i to receive the elementary signaling channels DE-i originating from the plurality of coding / decoding means 20-i. These elementary processing means 40 are capable of maintaining a dialogue between the plurality of telephone terminals TT-i and the fixed connection and management means MFG for controlling access to the telephone communication network and supervising telephone communications.

In practice, the elementary processing means on the management side 40 are connected to a digital communication medium RTD, for example of packet operation, such as the TRANSPAC network (registered trademark).

Preferably, on the RTD digital signaling channels are connected other components of the fixed connection and management means such as those relating to the management of databases (not shown), or even the authorization center (not shown). ) which manages for all fixed telephone terminals the authorizations of users to access the PSTN telephone communication network.

Those skilled in the art will understand that with such an architecture, in particular thanks to the permanent signaling links between the terminals and the fixed connection and management means, the management and control of telephone communications can be deported to the fixed means of connection and management and their peripherals, which simplifies the components of fixed telephone terminals and promotes the creation and development of telephone services for users. Referring now to Figure 2 which schematically illustrates the structure of a fixed telephone terminal according to the invention.

A fixed TT-i telephone terminal according to the invention includes:

- an elementary line interface on the terminal side ILT with an elementary transmission line LE-i;

- means of coding / decoding frames on the CTT terminal side connected to the elementary line interface on the terminal side ILT, and suitable for performing a bidirectional conversion of frames TRI and TR2 which will be described in more detail below (FIG. 4) , to restore and vice versa receive the elementary voice and signaling channels BE-i and DE-i;

- CPT speech coding / decoding means connected to the frame coding / decoding means and suitable for performing bidirectional speech conversion to decode the elementary voice channel BE-i into speech and conversely coding the speech into a voice channel BE-i elementary; and

- UTD data processing means connected to the CTT terminal side frame coding / decoding means and capable of performing data processing to decode an elementary signaling channel DE-i into data and conversely encode the data into a signaling channel elementary DE-i.

It should be noted that the elementary digital transmission line LE-i consists of a simple pair of telephone wires.

For example, the CPT speech coding / decoding means operate according to the CCITT standard No G721 in the form of ADPCM coding for "Adaptive Differential Puise Coding Modulation" or MICDA for "Pulse Modulation Adaptive Differential "and at a useful bit rate of 32 Kbits per second.

For example, the CPT speech coding / decoding means are sold under the reference MC145540 by the company MOTOROLA (USA).

The input El of the speech coding / decoding means CPT can receive the signals emanating from a microphone (not shown) while the output SI can be connected to a listener (not shown).

The data processing means UTD supply the frame coding / decoding means on the terminal side CTT with signaling signals DE-i.

The input E2 of the data processing means UTD can receive data originating, for example, from a payment card reader (not shown), in the case where the terminal TT is a payphone with payment cards.

The input E3 of the data processing means UTD can receive data emanating from a keyboard (not shown) and the output S2 can deliver information for a display (not shown).

The fixed terminal can be a simple or advanced telephone set (with an identification card reader for example) or even a public phone.

The invention also finds an advantageous application in the case where the fixed terminals are connected through at least one intermediate grouping unit placed between the fixed terminal and the fixed connection and management means, and at a distance from the fixed connection means and management and fixed terminals.

In Figure 3, there is shown such an installation. This installation revolves around a UR-1 regrouping unit associated with a plurality of fixed telephone terminals, for example three as shown in FIG. 3.

As will be seen in more detail below, the installation advantageously comprises a plurality of UR-j regrouping units with j integer having a value for example varying from 1 to 30.

An UR-j grouping unit such as the UR-1 unit includes:

a plurality of elementary line interfaces on the unit side 110-i connected respectively with an elementary transmission line LE-i described with reference to FIG. 1;

a plurality of coding / decoding means of elementary frames on the unit side 120-i connected respectively to an elementary line interface on the unit side 110-i, and capable of each performing a bidirectional conversion of the frames TRI and TR2 to restore and reciprocally receive the channels BE-i and DE-i elementary voice and signaling;

- at least one main transmission line LP-j capable of carrying at least one main voice channel BP-j consisting of elementary voice channels BE-i and one main signaling channel DP-j consisting of elementary signaling channels DE-i according to a predetermined bidirectional time screening TR3 and TR4 which will be described in more detail below (FIG. 5);

- a main line interface on the 150-j unit side with the LP-j main transmission line;

main multiplexing / demultiplexing means on the unit side 130-j capable of operating bidirectionally a multiplexing / demultiplexing between, on the one hand, the plurality of elementary voice and signaling channels BE-i and DE-i, and on the other hand an elementary multiplex voice channel BME-j and an elementary multiplex signaling channel DME-j; and

- means for coding / decoding TRI and TR2 frames on the unit side 140-j connected between the multiplexing / demulti¬ plexing means on the unit side 130-j and the main line interface 150-1, and suitable for performing bidirectional frame conversion TRI and TR2 and ensure a correspondence on the one hand between the signaling information contained in the elementary multiplex signaling channel DME-j and in the main signaling channel DP-j, and on the other hand between the voice information contained in the elementary multiplex voice channel BME-j and in the main voice channel BP-j, to allow the exchange of voice and signaling information between the different elementary transmission lines LE-i and the main transmission line LP- j.

As in the installation described above, the installation according to FIG. 3 further comprises fixed connection and management means MFGU which have direct connection means AD to the telephone communication network that PSTN for the circulation of information of voice between the fixed telephone terminals and the fixed means of connection and management MFGU.

According to the invention, these fixed means of connection and management MFGU comprise:

- at least one main line interface on the management side 200-j with the main transmission line LP-j;

means for coding / decoding the main TR3 and TR4 frames on the management side 210-j connected to the main line interface 200-j and suitable for performing a bidirectional conversion of the frames TR3 and TR4 to restore and vice versa receive the voice channels and main signaling BP-j and DP-j; - main processing means on the management side 230 connected to the coding / decoding of main frames on the management side 210-j to receive the main signaling channel DP-j and suitable for maintaining a dialogue with the grouping unit UR-j by the main signaling channel DP-j to control access to the telephone communication network and supervise telephone communications.

Advantageously, the installation comprises several grouping units UR-j and several main transmission lines LP-j each connected between a grouping unit and the fixed connection and management means MFGU.

As a result, the fixed connection and management means MFGU further include:

- a plurality of main line interfaces 200-j management side each connected to a main transmission line

LP-j;

a plurality of coding / decoding means of main frames on the management side 210-j, each connected to a main line interface 200-j; and

- main multiplexing / demultiplexing means on the management side 220 connected between the plurality of coding / decoding means of main frames on the management side 210-j, and the direct connection means AD, and suitable for operating bidirectionally a multiplexing / demultiplexing between the plurality of main voice channels BP-j and a main multiplex voice channel BPM, to allow the exchange of voice information between the direct connection means AD and the plurality of main frame coding / decoding means management side 210-j . In practice, the main processing means on the management side 230 are connected to the digital communication medium RTD described with reference to FIG. 1.

The advantageous properties of the installation result from fixed telephone terminals which are very simple, using only a reduced speed and having no means of managing telephone services.

They also result from elementary digital links capable of simultaneously transmitting an elementary voice channel originating from or intended for a fixed telephone terminal.

Furthermore, the grouping units which here perform a simple multiplexing / demultiplexing of the voice and elementary signaling channels originating from or intended for telephone terminals contribute to the solution according to the invention.

In addition, it should be noted that the main transmission lines connecting the grouping units and the fixed connection and management means are digital multiplexed / demultiplexed links which are suitable for carrying the elementary voice and signaling channels emanating from or at destination of telephone terminals.

Finally, the elementary and main links which are permanent between the terminals and the fixed means of connection and management via the grouping units make it possible to supervise in real time the telephone communications established from the terminals.

Advantageously, in order to keep a simple technical solution making it possible to achieve the objective of reduced cost and far-reaching, the Applicant has retained, for elementary links, an alternating digital transmission also known as ping pong in which the time is shared between a transmission period and a reception period. In addition, the bit rate of the elementary digital transmission line LE-i is chosen to be reduced compared to the conventional rate in order to achieve the objectives mentioned above.

Thus, according to the invention, there is a useful elementary bit rate broken down as follows: 32 Kbits for speech and 2 Kbits for signaling, that is to say supervision data.

However, taking into account the fact that, as seen above, a duplex transmission is chosen, the useful elementary bit rate is brought to at least 2 x (32 + 2), that is to say 68 Kbits per second.

Preferably, to leave the dead times necessary for the transmission / reception switching, it is planned to adopt a raw elementary bit rate of the order of 72 Kbits per second.

Advantageously, this raw elementary bit rate of 72 Kbits per second uses a transmission frequency of 36 KHz taking into account the chosen coding method, for example NRZ.

It should be noted that this maximum frequency is compatible with the range objective which is for example greater than 4 km.

In Figure 4, there is shown the structure of the signals conveyed by the elementary transmission line LE-i according to the invention.

This structure is broken down into a first frame TRI for the transmission of the terminal and a second frame TR2 for the reception of the terminal.

The first TRI frame relating to the transmission of the terminal comprises 72 bits for a period of 1 millisecond, and the second reception frame TR2 also includes from the terminal 72 bits for a period of 1 millisecond.

The TRI frame is broken down into 2 head guard bits GE1 and GE2, 4 signaling bits SE1 to SE4, 64 bits PE1 to PE64 for speech coding, and 2 tail guard bits GE3 and GE4.

The frame TR2 is broken down into 2 head guard bits GR1 and GR2, 4 signaling bits SRI to SR4, 64 bits PR1 to PR64 for speech coding, and 2 tail guard bits GR3 and GR4. For example, the speech bits consist of 16 samples of 4 bits each.

Preferably, the signaling bits SE1 to SE4 and SRI to SR4 form an 8-byte message. This message can be coded to define the different types of information exchanged between the fixed connection and management means MFG or MFGU and the TT-i terminal.

Each message can include a code relating to the periodic transmission control.

According to the principle of synchronization of exchanges between each terminal and the fixed connection and management means (FIG. 1) MFG or between each terminal and the UR-j grouping units (FIG. 3), the coding / decoding means of elementary frames on the management side 20-i or on the unit side 120-i are masters for the synchronization of the frame and the bits.

With regard to the synchronization of the frame, the means 20-i or 120-i permanently emit a pattern which is decoded by the terminal TT-i and allows this terminal to recover the synchronization of the transmission / reception alternation.

For example, the pattern is a particular coding registered in the frame TR2 which contains in the set of 68 bits of useful information, a binary profile allowing initialization ser the exchange and give a transmission synchronization reference.

With regard to bit synchronization, the synchronization pattern transmitted by means 20-i or 120-i allows the reception clock of the terminal TT-i to be set at the start of each exchange.

During communication, bit synchronization is maintained thanks to existing binary transitions.

It should be noted that the coding used ensures a sufficient rate of binary transitions in the messages for good bit synchronization on reception.

It should also be noted that the structure of the messages is free, that is to say that it can include synchronization codes but also messages making it possible to establish a connection, to supervise it, to break it, as well as application messages allowing the transmission of data between the TT-i terminal and the fixed MFG or MFGU management means, for example messages linked to the telephone application, access security or payment.

FIGS. 5A and 5B show the structure of the signals conveyed by a main transmission line LP-j according to the invention comprising the alternating frames TR3 and TR4.

The main bit rate of the main line LP-j is advantageously of the order of 2 x 144 Kbits useful per second, i.e. 2 x 160 Kbits gross per second, since these lines are subdivided into four main subchannels specific to each convey the voice and signaling information at the same bit rate, for example 2 × 36 raw bits per second.

More precisely, the structure of the signals on a main line breaks down into a first frame TR3 for the transmission of fixed connection and management means and a second frame TR4 for the reception of fixed connection and management means.

The frames TR3 and TR4 each include 160 bits for a period of 1 millisecond.

The frame TR3 is broken down into 16 control bits individualized in CEI to CE16, four main voice sub-channels individualized in SBEl to SBE4 each comprising 32 bits and four main signaling sub-channels individualized in SDE1 to SDE4 each comprising 4 bits.

The frame TR4 relating to reception has a structure identical to that of the frame TR3.

As a variant, the frames TR3 and TR4 are conveyed simultaneously by the main links, for example according to a technique known as "echo cancellation" (not shown). In this variant, the instantaneous bit rate is half less than in alternation.

As for the bit rate of the BPM link between the main multiplexing / demultiplexing means on the management side 220 and the direct connection means AD, it is advantageously of the order of 2 megabits per second, in the case of MIC 30 links standard tracks.

In this case, the direct connection means AD advantageously comprise speed conversion means (not shown) compatible with the voice speed used on the telephone channels of the PSTN network.

In Figure 6, there is shown an installation comprising a wire branch and a radio frequency branch.

The wire branch is that described with reference to FIGS. 3 to 5. It essentially comprises a plurality of fixed telephone terminals TT-i, a grouping unit UR-j, a plurality of elementary wired transmission lines at reduced speed LE-i between the plurality of terminals and the grouping unit, fixed means of connection and management MFGU with the PSTN telephone communication network and the RTD data transmission network, and a wired main transmission line LP-j between the UR-j unit and the MFGU means.

The radiofrequency branch according to the invention comprises a plurality of autonomous telephone sets PA-k with radiofrequency transmission / reception which will be described in more detail below, k is here an integer whose value varies between 1 and k.

According to the invention, at least one fixed terminal BFR-m is provided with m integer varying between 1 and m.

The essential means of the fixed terminal are described in the French Patent Application filed in the name of the Applicant on October 22, 1991 under No. 91 13033. As necessary, for the description of the radiofrequency branch, reference is made to this Patent Application.

In practice, in accordance with Figure 7, the BFR-m terminal includes:

a radiofrequency transmission / reception interface on the terminal side IR1 to IR4 capable of operating according to a plurality of radiofrequency channels capable of each carrying at least one radiofrequency elementary voice channel BBl to BB4 and one radiofrequency elementary signaling channel DB1 to DB4 according to a predetermined elementary time screening, to allow the exchange of voice and signaling information with the autonomous telephone sets PA-k;

* an ILB terminal-side line interface with a main LP-m transmission line, the other end of which is connected to the fixed connection and management means MFGU and which is capable of carrying at least one voice channel main and a main signaling channel according to a predetermined bidirectional main time framing; and

* terminal side processing means comprising:. multiplexing / demultiplexing means on the terminal side MUXB capable of operating bidirectionally a multiplexing / demultiplexing between, on the one hand, the plurality of elementary radiofrequency voice channels BB1 to BB4 and of elementary radiofrequency signaling channels DB1 to DB4 and, d on the other hand, a multiplex voice channel and a multiplex signaling channel;

. frame coding / decoding means on the terminal side MCDB connected between the multiplexing / demultiplexing means on the terminal side MUXB and the line interface on the terminal side ILB, and suitable for performing bidirectional frame conversion and ensuring correspondence, on the one hand between the signaling information contained in the multiplex signaling channel and in the main signaling channel, and on the other hand, between the voice information contained in the multiplexed voice channel and in the main voice channel, for allow the exchange of voice and signaling information between the main transmission line LP-m and the different radiofrequency channels allocated to the different autonomous telephone sets PA-k in telephone communication with the telephone communication network;

. the main processing means on the management side 230 described with reference to FIG. 3 being able to maintain a dialogue with the fixed terminal BFR-m via the main signaling channel to manage the allocation of the radio frequency channels and control the communications telephone calls.

Preferably, the radio frequency links are at reduced speed between the terminal and the fixed terminal.

The advantageous properties of such an installation result from the characteristics already mentioned above such as: - the telephone terminals and the autonomous stations are very simple and do not have means of management of the telephone service;

- the elementary radiofrequency links allow the simultaneous transmission of an elementary radiofrequency voice channel and an elementary radiofrequency signaling channel;

- the radiofrequency terminals carry out a simple radioelectric transformation as well as a multiplexing / demultiplexing of the elementary radiofrequency channels in a manner similar to those of the grouping units;

- the multiplexed digital links between the grouping unit or the radio frequency terminal and the fixed connection and management means carry the main voice and signaling channels; and

- the connection and management means supervise in real time, thanks to the permanent signaling links with the terminals and / or units and the terminals, the allocation of the radiofrequency channels and the telephone communications established from said terminals.

FIG. 8 shows the structure of an autonomous telephone set, for example of the public phone type.

The architecture of the PA-k stand-alone station is similar to that of a wired digital connection telephone terminal described with reference to FIG. 2; It is only distinguished from it by the fact that the radiofrequency transmission / reception module replaces the line interface.

Each PA-k autonomous radio transmission / reception telephone set includes:

- a radio frequency transmit / receive interface on the IRP station; means for coding / decoding elementary frames on the CTT station side connected to the radiofrequency transmission / reception interface on the station side, and suitable for performing bidirectional frame conversion to restore and reciprocally receive the radiofrequency elementary voice channels;

- CPT coding / decoding means of speech connected to the coding / decoding means of elementary frames on the station side and suitable for carrying out a bidirectional conversion of speech to decode the radiofrequency elementary voice channel into speech and conversely coding speech into a radio frequency elementary voice channel; and

- UTD data processing means on the station side connected to the coding / decoding means of elementary frames on the station side and suitable for carrying out data processing for coding data into an elementary radio frequency signaling channel and conversely decoding a signaling channel - elementary radio frequency data.

In practice, the radiofrequency transmission / reception interface includes a COA antenna coupler, a frequency change element CHF and a modulator for transmission and a demodulator for reception.

The CAF frequency change element is suitable for changing radiofrequency frequencies into working frequencies.

For example, the radiofrequency frequencies are of the order of 800 to 900 MHz, while the working frequencies are of the order of 1 MHz.

For example, since the autonomous station Pa-2 is a payphone, the UTD means receive information from a payment card reader or the like LEC. In the case of terminals with low telephone traffic, it is not necessary to assign a radio frequency circuit to each terminal permanently.

Advantageously, a reduced number of radiofrequency channels n can ensure the flow of traffic from N terminals, the allocation of the radiofrequency channels being effected dynamically by the terminals at the request of the terminals.

In the case of terminals used on average at 10% of the time, and for 100 terminals, good quality of service is offered by using approximately 30 radiofrequency channels.

This solution offered according to the invention by the radio frequency link makes it possible to significantly reduce the number (and therefore the cost) of terminals and fixed means of connection and management.

Claims

1. Telephone installation characterized in that it comprises:

- a plurality of fixed telephone terminals (TT-i);

- a telephone communication network (PSTN);

- fixed connection and management means (MFG) having direct connection means (AD) to the telephone communication network (PSTN) for the circulation of voice information between the telephone terminals (TT-i) and the fixed means of connection and management (MFG);

- a plurality of elementary transmission lines (LE-i) each arranged between a fixed telephone terminal (TT-i) and the fixed connection and management means (MFG), each elementary transmission line being capable of carrying at least one elementary voice channel (BE-i) and an elementary signaling channel (DE-i) according to a bidirectional time elementary framing in alternating predetermined and at reduced rate;

fixed connection and management means (MFG) comprising:

* a plurality of elementary line interfaces on the management side (10-i) respectively with an elementary transmission line (LE-i);

* a plurality of coding / decoding means of elementary frames on the management side (20-i) connected respectively to an elementary line interface on the management side (LE-i), and capable of each performing a bidirectional frame conversion to restore and reciprocally receive the basic voice and signaling channels (BE-i, DE-i); * elementary multiplexing / demultiplexing means on the management side (30) connected between the plurality of coding / decoding means of elementary frames on the management side (20-i) and the direct connection means (AD), and suitable for operating bidirectionally multiplexing / demultiplexing between the plurality of elementary voice channels (BE-i) and an elementary multiplex voice channel (BME) to allow the exchange of voice information between the direct connection means and the plurality of coding / decoding means elementary frames on the management side (20-i), and

* elementary processing means on the management side (140) connected to the plurality of coding / decoding means of elementary frames on the management side (20-i) to receive the elementary signaling channels (DE-i) and suitable for maintaining a dialogue between the plurality of telephone terminals (TT-i) and the fixed connection and management means (MFG) to control access to the telephone communication network and supervise telephone communications.

2. Telephone installation, characterized in that it comprises:

- a plurality of fixed telephone terminals (TT-i);

- a telephone communication network (PSTN);

- at least one grouping unit (UR-j);

- a plurality of elementary transmission lines (LE-i) each disposed between a fixed telephone terminal (TT-i) and the grouping unit (UR), each elementary transmission line (LE-i) being capable of conveying to the minus an elementary voice channel (BE-i) and an elementary signaling channel (DE-i) according to a predetermined half-duplex time elementary framing at a reduced rate;

the grouping unit (UR-j) comprising: * a plurality of elementary line interfaces on the unit side (110-i) respectively with an elementary transmission line (LE-i);

* a plurality of encoding / decoding means of elementary frames on the unit side (120-i) connected respectively to an elementary line interface on the unit side (110-i), and suitable for each performing a bidirectional frame conversion to restore and vice versa basic voice and signaling channels (BE-i and DE-i);

* at least one main transmission line (LP-j) capable of carrying at least one main voice channel (BP-j) consisting of elementary voice channels (BE-i) and one main signaling channel (DP-j) consisting of elementary signaling channels (DE-i) according to a predetermined bidirectional main time framing;

* at least one main line interface on the unit side (150-j) with the main transmission line (LP-j);

* main multiplexing / demultiplexing means on the unit side (130-j) suitable for operating bidirectionally a multiplexing / demultiplexing between on the one hand the plurality of elementary voice and signaling channels (BE-i and DE-i) and on the other hand, elementary multiplex voice and signaling channels (BME-j and DME-j);

* means for coding / decoding main frames on the unit side (140-j) connected between the main multiplexing / demul¬ tlexing means on the unit side (130-j) and the main line interface on the unit side (150-j), and their own to carry out a bidirectional conversion of frames and ensure a correspondence on the one hand between the signaling information contained in the elementary multiplex signaling channel (DME-j) and in the main signaling channel (DP-j) , and on the other hand between the voice information contained in the elementary multiplex voice channel (BME-j) and in the main voice channel (BP-j), to allow the changes voice and signaling information between the different elementary transmission lines (LE-i) and the main transmission line (LP-j);

- fixed connection and management means (MPGU) having direct connection means (AD) to the telephone communication network (PSTN) for the circulation of voice information between the telephone terminals (TT-i) and the fixed means of connection and management (MFGU),

said fixed connection and management means (MFGU) comprising:

* at least one main line interface on the management side (200-j) with the main transmission line (LP-j);

* means for coding / decoding main frames on the management side (210-j) connected to the interface with this main line (200-j), and suitable for carrying out a bidirectional conversion of frames to restore and vice versa receive the channels of main voice and signaling (BP-j and DP-j);

* main processing means on the management side (230) connected to the coding / decoding means of main frames on the management side (210-j) to receive the main signaling channel (DP-j) and suitable for maintaining a dialogue with the unit grouping (UR-j) by the main signaling channel (DP-j) to control access to the telephone communication network and supervise telephone communications.

3. Installation according to claim 2, characterized in that it comprises a plurality of grouping units (UR-) and a plurality of main transmission lines (LP-j) each connected between a grouping unit (UR-j ) and the fixed connection and management means (MFGU) and in that the fixed connection and management means (MFGU) further comprise: - a plurality of main interfaces on the management side (200-j) each connected to a main transmission line (LP-J);

- a plurality of coding / decoding means of main frames on the management side (210-j) each connected to a main line interface (200-j); and

- main multiplexing / demultiplexing means on the management side (220) connected between the plurality of coding / decoding means of main frames on the management side (210-j) and the direct connection means (AD), and suitable for bi-directionally multiplexing / demultiplexing between the plurality of main voice channels (BP-j) and a main multiplex voice channel (BMP) to allow the exchange of voice information between the direct connection means (AD) and the plurality of coding means / decoding of main frames on the management side (210-j).

4. Installation according to any one of the preceding claims, characterized in that each fixed telephone terminal (TT-i) comprises:

- an elementary line interface on the terminal side (ILT) with an elementary transmission line (LE-i) at reduced speed;

means of coding / decoding of elementary frames on the terminal side (CTT) connected to the elementary line interface on the terminal side (ILT), and suitable for carrying out a bidirectional conversion of frames to restore and reciprocally receive the elementary voice and signaling channels (BE-i and DE-i);

- speech coding / decoding means (CPT) connected to the coding / decoding means of elementary frames on the terminal side and suitable for performing bidirectional conversion of speech to decode the elementary voice channel (BE-i) into speech and conversely, coding the speech into an elementary voice channel (BE-i); and means of data processing on the terminal side (UTD) connected to the means of coding / decoding of elementary frames on the terminal side and suitable for performing data processing to code the data into an elementary signaling channel (DE-i) and conversely, code data into an elementary signaling channel (DE-i).

5. Installation according to any one of the preceding claims, characterized in that the useful bit rate of each elementary transmission line (LE-i) is of the order of 68 Kbits per second with 64 Kbits per second allocated to the channels of elementary voice and 4 Kbits per second allocated to elementary signaling channels.

6. Installation according to any one of claims 2 to 5, characterized in that the useful bit rate of each main transmission line (LP-j) is of the order of 288 Kbits per second with 256 Kbits per second allocated to main voice channels and 32 Kbps assigned to the main signaling channels.

7. Installation according to any one of claims 1 to 6, characterized in that the fixed telephone terminal is a payphone.

8. Installation according to any one of claims 1 to 6, characterized in that the terminal is a simple telephone set.

9. Installation according to any one of claims 1 to 6, characterized in that the terminal is an advanced telephone set, in particular equipped with a card reader ¹ identification.

10. Installation according to one of the preceding claims, characterized in that it further comprises:

- a plurality of autonomous telephone sets (PA-k) with radiofrequency transmission / reception; - at least one fixed terminal (BER-m) comprising:

* a terminal side radiofrequency transmission / reception interface (IR1 to IR4) capable of operating according to a plurality of radiofrequency channels capable of each carrying at least one radiofrequency elementary voice channel (BB1 to BB4) and one radiofrequency elementary signaling channel ( DB1 to DB4) according to a predetermined elementary time framing, to allow the exchange of voice and signaling information with autonomous telephone sets (PA-k);

* a terminal side line interface (ILB) with a main transmission line (LP-m), the other end of which is connected to the fixed connection and management means (MFGU) according to claim 2 and which is capable of carrying at least a main voice channel and a main signaling channel according to a predetermined bidirectional main time framing; and

* terminal side processing means comprising:

. terminal side multiplexing / demultiplexing means (MUXB) capable of operating bidirectionally a multiplexing / demultiplexing between, on the one hand, the plurality of elementary radiofrequency voice channels (BB1 to BB4) and elementary radiofrequency signaling channels (DB1 to DB4) and, on the other hand, a multiplex voice channel and a multiplex signaling channel;

. terminal side frame coding / decoding means (MCDB) connected between the terminal side multiplexing / demultiplexing means (MUXB) and the terminal side line interface (ILB), and suitable for performing bidirectional frame conversion and ensuring a correspondence, on the one hand between the signaling information contained in the multiplex signaling channel and in the main signaling channel, and on the other hand between the voice information contained in the multiplexed voice channel and in the voice channel main, to allow the exchange of voice and signaling information between the main transmission line (LP-m) and the different radio frequency channels allocated to the different autonomous telephone sets (PA-k) and telephone communication with the telephone communication network;

. the main processing means on the management side (230) according to claim 2 being suitable for maintaining a dialogue with the fixed terminal (BFR-m) by the main signaling channel for managing the allocation of the radiofrequency channels and controlling the telephone communications.

11. Installation according to claim 10, characterized in that each autonomous telephone set (PA-k) with radiofrequency transmission / reception comprises:

- a radio transmission / reception interface on the station side (IRP);

means of coding / decoding of elementary frames on the station side (CTT) connected to the radiofrequency transmission / reception interface on the station side, and suitable for carrying out a bidirectional conversion of frames to restore and reciprocally receive the elementary radio frequency voice channels ;

- speech coding / decoding means (CPT) connected to the coding / decoding means of elementary frames on the station side and suitable for carrying out bidirectional speech conversion in order to decode the radio elementary voice channel into speech and conversely coding the speech into an elementary radio frequency voice channel; and

- data processing means on the station side (UTD) connected to the coding / decoding means of elementary frames on the station side and suitable for carrying out data processing for coding data into a radio frequency elementary signaling channel and conversely decoding a channel radio signal and data signaling.

12. Installation according to one of claims 10 and 11, characterized in that the elementary radiofrequency digital links are at reduced rate.

13. Installation according to one of claims 10 to 12, characterized in that the autonomous telephone set (PA-k) is a payphone.