MXPA98003144A - Device and procedure of digital-analog communication - Google Patents

Abstract

A device for communication between a digital adapter (5) connected to a control unit (4) via a digital interface (7), particularly an ISDN interface, and an analog adapter (6) connected to a control unit (3) via an analog interface (8) ). The exchanges (3, 4) are interconnected by means of a telecommunications network (2). The device comprises means (11, 12; 15, 16) for directly attaching the digital adapter and the analog adapter (6). The digital data that comes from the digital adapter (5) is transmitted in digital form to the analog adapter (6) and vice versa, without emulating an analog signal.

Description

DEVICE AND PROCEDURE FOR NUMERICAL-ANALOGUE COMMUNICATION FIELD OF THE INVENTION The present invention relates to a hybrid digital-analog communication device on a telephone channel.

BACKGROUND OF THE INVENTION The growth of the park of installed personal computers and the birth of new telematic services are testimony of the growth potential of the volume of the online communications. While the current situation is satisfactory for the majority of users who themselves connect their internal networks to external services through high-capacity transmission networks or leased lines, the cost of these solutions is very high for small businesses or for individuals. There is the certainty that this situation will evolve and that the need to distribute the services will imply a high transmission capacity to reach, up to the residences of individuals, and will be the origin of a generalized broadband network. But such a network has little chance of being deployed P1191 / 98MX universally before several years have passed, say tens of years. Expecting the possibility of a high capacity network, individuals, schools, small businesses must resort to transmitting their data in the telephone network. For this, they have two possibilities of known technologies. The most widespread solution is to use modems that operate at a capacity of 14.4 Kb / s or 28.8 Kb / s. A more expensive solution is to use the ISDN network, which has two data channels at 64 Kb / s and a signaling channel at 16 Kb / s. However, this second solution is not available everywhere and requires a significant investment on the part of the users, in terms of very high subscriber rates as well as adapted communication devices.

SUMMARY OF THE INVENTION The invention aims to propose a third alternative that uses the advantages of a network, such as for exercising. the ISDN network, and mainly a higher transmission speed of the order of 64 Kb / s, all without creating a greater expense for users in _ Ratio to the cost of the classic solutions that work at 14.4 Kb / s. In view of the foregoing, the invention relates to P1191 / 98MX to a communication device between a numerical adapter linked to a central unit by means of a numerical interface, namely an ISDN type network, and an analog adapter linked to a central unit by means of an analog interface, these exchanges are linked by means of a telecommunications network, characterized in that it comprises means of direct connection between the digital adapter and the analog adapter, the numerical information of the digital adapter is sent to the analog adapter and, in a reciprocal way, in numerical form without emulating an analog signal. According to other characteristics of the invention: the direct connection means comprise, in the direction of transmission that the digital adapter has towards the analog adapter, a digital transmitter located in the digital adapter and capable of transmitting to an analog receiver located in the analog adapter , analogue pulses whose voltage levels represent the information transmitted from the digital adapter to the analog adapter; the direct connection means comprise, in the direction of the transmission that is presented from the analog adapter to the digital adapter, r. analog transmitter located on the analog adapter and capable of transmitting to a digital receiver, located on the P1191 / 98MX numerical adapter, an analog signal in such a way that during its sampling by the analog interface of the control panel, it will be worth a quantification level determined by a numeric information transmitted by the analog adapter to the numerical adapter; the analog receiver comprises an adaptive linear equalizer connected by its input to the output of an analog / digital converter, and connected by its output to the input of an output equalizer attached to the user's equipment, so that the response to the output of the Adaptive linear equalizer is a class IV response; said output equalizer is a decision return equalizer or a Viterbi type equalizer. the transmitter of the analog adapter comprises a line encoder followed by a pre-distortion filter that synthesizes a partial response of class IV; - said means comprise, on the side of the numerical adapter, a selector of n levels, n being principally equal to 64, represented by the shape of an octet, between. = 256 possible quantization levels, said level selector is connected to the input of the user equipment and to the output of a numerical interface; P1191 / 98MX The numerical adapter comprises a line and channel decoder connected by its input to the output of a linear converter that uses a conversion law of type A, and connected by the output to the user's equipment. The invention also relates to a method of direct transmission between an analog adapter and a digital adapter, bidirectionally. In the sense of the transmission that the digital adapter has towards the analog adapter, this method is characterized in that it comprises the following steps: taking a group of bits that come from a source of numerical data, for example a group of 6 bits; select one between n (n = 64) preselected levels among N (mainly N = 256) voltage levels, each level is represented in numerical form by an octet; send successively the octets corresponding to the selection of one between n levels through the digital network towards an analog adapter, so as to produce signals in the analog adapter whose amplitude is practically equal to the levels represented by each octet, the signals correspond successive octets that interfere with each other to produce a resulting analog signal on the analog adapter; P1191 / 98MX equalize said resulting analog signal in order to eliminate the interferences; measure the amplitude of the resulting analog signal and subtract the numeric value from the octet; from the numeric value of the octet reconstitute the group of bits and send them to a receiver of numerical data. The procedure of an analog adapter towards a numerical adapter in a communication system is characterized in that it comprises the steps consisting of: taking a group of bits that come from a data source connected to the communication system; selecting an analog signal having an amplitude corresponding to the numerical value of the group of bits, the signals corresponding to the successive groups that interfere with each other and that have a form such that at the moment in which the analog signal is sampled at the analog interface of the control panel, its value is substantially equal to a quantization level between N predetermined quantization levels, so that after the sampling of the analog signal, an octet appears in the numerical adapter, representing said level of quantification. treat the successive octets? e way to eliminate the interference between the successive signals and P1191 / 98MX recover the value of the bit groups; transmit the numerical value of the groups of bits found on the user's equipment.

BRIEF DESCRIPTION OF THE DRAWINGS OR FIGURES The invention will be better understood by reading the following description by way of non-limiting example, in relation to the attached drawings, in which: Figure 1 represents a schematic of the principle of the device communication performing the invention; Figure 2 represents a graph of the maximum transmission capacity for a quantization law of type A, as a function of the minimum distance between the n selected levels of quantization; Figure 3 represents a diagram of the principle of a numerical adapter adapted to the device according to the invention; Figure 4 shows a diagram of the principle of an analog adapter adapted to the device according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Referring to Figure 1, the general architecture of a device is represented therein.

P1191 / 98MX communication 1 using a public switched network 2 for transmissions between two exchanges 3, 4 connected respectively, of a first side, to a numerical adapter 5 by a numerical interface 7, and on the other side, to an adapter 6 called analog, that is to say connected by a simple classical telephone interface 8. A numerical server 9, which is for example a host server of high speed applications, is connected to the digital exchange 3 by a line 7 and a numerical adapter 5 of the server 9. The terminal 35 is, namely, in the form of a personal computer connected to the analog adapter 6. The adapter and a telephone 10 are connected by the simple telephone line 8 to the central station 4. Under the analogue line 8 the analogue information passes: the voice of the user of the telephone 10 or the numerical information emitted by the analogue adapter 6 or directed to it. Thanks to this architecture, which is known in the case where the analog adapter is a classical modem, it is possible to call a classical analog line 8 from a server 9, and in a reciprocal manner. This possibility is already used to transmit the word c data. When the digital signal coming from a digital adapter 5 arrives, after its transport per the network 2, P1191 / 98MX just to the telephone exchange 4, the octets of the digital signal are transformed by an integrated numeric / analog converter to the central 4, in the voltage levels, and thus with a sampling frequency that is normally 8000 times per second. This numerical / analog conversion (N / A) takes place following a conversion law, for example the "A" law in Europe, or the "μ" law in other parts of the world. In another direction, that is to say in the sense of the analog adapter 6 to the digital adapter 5, the analog voltage received by the control unit 4 is digitized by a sampler and represented by octets. These octets, after transport on the network 2, are transmitted to the digital adapter 5. Overall, a connection as described above allows a digital adapter 5 to communicate with an analog adapter 6. Traditionally, the digital adapter 5 sends a sequence of octets that, after a transformation using a law above, corresponds to a voice or word signal, or to a classic modem signal. Then, this signal is normally treated in the case of telephony, and is transmitted directly to the listener of the telephone combination 10. Similarly, the analog adapter 6 is traditionally made up of a modem. The reverse operations are carried out in the other direction P1191 / 98MX transmission. The invention proposes a method for transmission between an analog adapter 6 and a numerical adapter 5, and a corresponding device. The principle of the invention is explained together with Figure 2, which represents the compromise that exists between the transmission speed (in ilobits / seconds on the scale of the ordinates) and the resistance to noise. If you want to transmit at 64 Kb / s, all 256 quantization levels possible from eight bits (2 - 256) must be used. On the other hand, for a transmission subject to a Gaussian noise, the probability of error during transmission depends on the minimum distance dmn (in the abscissa of Figure 2) between two adjacent levels of the quantization scale and this relationship is represented in Figure 2 for a type A conversion law. It is surprisingly stated that by increasing the minimum distance dm? n between levels 2 to 4, half of the quantization levels are not lost, but only 33 levels of 256 The result is similarly that a transmission of approximately 48 Kb / s is possible using only 64 separate quantization levels at a distance dm? N = 128. The stages of the two-way transmission procedure are, therefore, , the following when P1191 / 98MX analog signals are quantified in relation to n = 64 levels, allowing a capacity of 48 Kb / s. For the method of transmitting a digital adapter to an analog adapter, the steps of the method comprise the following steps: - taking from a group of bits that come from a source of numerical data, for example a group of 6 bits; - select from n (ie n = 64) preselected levels among N (namely N = 256) voltage levels, each level is represented under the numerical form of one octet transmitted 8000 times per second; - send successively the octets corresponding to the selection of n levels through the digital network towards an analog adapter, in order to produce signals in the analog adapter whose amplitude is substantially equal to the levels represented by each octet, the signals correspond to successive octets that interfere with each other to produce a resulting analog signal on the analog adapter; - equalizing said resulting analog signals in order to eliminate the interferences; - measure the amplitude of the resulting analog signal and tell it the numerical value of the octet; - from the numerical value of the octet, reconstitute the group of bits and send them to a receiver of P1191 / 98MX numerical data. The method of transmitting an analog adapter to a digital adapter in a communication system comprises the steps consisting of: taking 8000 times per second a group of bits that come from a data source connected to the communication system; - selecting an analog signal having an amplitude corresponding to the numerical value of the group of bits, the signals corresponding to the successive groups interfere with each other, and has a form such that at the moment where the analog signal is sampled at the analog interface from the central 4 its value is substantially equal to a quantization level between N predetermined quantization levels, so that after sampling the analog signal, an octet appears in the numerical adapter representing said quantization level; - treat the octets successively in order to eliminate the transfer between successive levels and recover the value of the groups of bits; - transmitting the numerical value of the bit groups recovered in the computer of the numeric terminal user 9. In summary, the transmission procedure does not P1191 / 98MX tries to reconstruct an analog signal for transmission on the line to the analog adapter. In contrast, the octets representing the numerical information are directly transformed into voltage levels, as illustrated by the corresponding device in the upper part of Figure 3, which refers to the transmission part of the digital adapter 5. example, to communicate at 48 Kb / s, the digital adapter 5 transforms the bits received from the user into groups of 6 bits representative of voltage levels (either 26 = 64 possibilities), sent 8000 times per second, and which represent one between the 256 levels of the conversion law. The 64 levels used in this form and in this example are selected so as to be separated from each other as much as possible to provide greater resistance to noise. This separation is called the minimum distance dm? N in the following. The interest of this approach is to eliminate the quantization noise introduced by the conversion law. It should be noted that it can also be visualized in a known manner, using the grid-coded modulation to obtain a higher noise resistance. For interfacing with the interface 7, the numerical adapter 5 mainly comprises an upper part (above the horizontal interrupted path) P1191 / 98MX constituted by a digital transmitter 11, and a lower part 12 constituted by a digital receiver. The input of the digital transmitter 11 is powered by a source of numerical data, such as by the server 9 (Figure 1). The input of the transmitter 11 that sees pass the octets representing the numerical information issued from the server 9, is connected, through a buffer 13 in case of a capacity adaptation is necessary, to the input of a novel selector 14, whose output constitutes the input of the digital transmitter 11 of the digital adapter 5. This output of the digital transmitter 5 is connected, through the network 2, to the input of the receiving portion of the analog adapter 6, which is represented in the upper part. of Figure 4, the transmitting art of the analog adapter 6 is represented by the lower part of Figure 4. The receiver 15 of the analog adapter 6 receives, at its input (in the upper part of Figure 4), a series of pulses analogs whose voltage level represents the information transmitted by the numerical adapter of Figure 3. The presence of the filter in the telephone exchange 4 causes inter-pulse interference successive Therefore, it is difficult to find and measure their levels. The analog receiver 15 of the invention, which is illustrated in the upper part of Figure 4, is composed of P1191 / 98 X two main parts: an adaptable numerical linear filter 17 that "equalizes" the signal, transforms the distorted impulse that comes from the network through a filter 18 and of an analog / numerical converter 19, and a well controlled impulse that does not introduce interference more than in two successive even (or odd) levels. More precisely, the output Yn of the equalizer filter 17 at time n is given by the expression: ^ n = ^ n ~ n-2 where Xn refers to the levels sent by the digital adapter 5. This equalizer system is in itself same known as a "partial class IV response". The invention makes it possible to apply such a response to a situation of direct communication between a digital adapter 5 and an analog adapter 6. To avoid the propagation of error in the receiver, the use of a differential code in 14 is recommended, as it is known. Furthermore, if the linear equalizer filter 17 must be adaptable, its selection is within the skill of the person skilled in the art. Er. this point, it is necessary to eliminate the interference between symbols that are expressed by the relation Yn = Xn - X "_ 2- For this, two common techniques are usable: P1191 / 98MX decision return equalization (DFE) and the Viterbi algorithm, represented by the functional block 20. The levels Xn produced by the telephone exchange 4 are not always equal to their nominal levels provided by the law of quantification. The analog receiver 15 must, therefore, emit the real value of Xn, and these real values must be used in the decision return equalizer, or the Viterbi equalizer 20. The estimate can be made using one of the variations of the algorithm of least squares, implemented in a functional block 21. It should be noted that the actual values of Xn must also be used in an echo canceller 22 of the numerical adapter (Figure 3). For this, the numerical adapter 5 can also proceed to an estimation of real values with the help of a functional block similar to block 21 of FIG. 4, or use corresponding control information transmitted by the analog adapter 6. The corresponding connections do not they are represented in the Figures to facilitate their compression. In the other data transmission direction, ie from the analog adapter 6 to the digital adapter 5, the transmitter 16 of the analog adapter illustrated in the lower part of Figure 4 uses the clock 23 of the terminal 6, which has recovered in its receiving section 15.

P1191 / 98MX The objective of the transmission part 16 of the analog adapter 6 is to produce an analog signal which, during sampling, will be worth one of the levels of the law of quantification, the level in question is determined by the numerical information transmitted by the numerical adapter 5. The invention provides that the impulse response between the analog adapter 6 and the central 4 is measured by the digital adapter 5, and communicated to the analog adapter 6 by control messages. Based on these measurements, the analog adapter 6 synthesizes a numerical filter 24 so that the total response (line 8 + filter) is at the level of a partial response of class IV. This technique is called "pre-distortion". The filter 24 also has an accessory role, which is to produce a signal at a rate of 16 kHz, namely from an input of 8 kHz that comes from the analog adapter 6 to facilitate the design of the analog filter 25 that follows to the N / A converter 26, which produces an analog signal from a digital signal. Thanks to the use of the pre-distortion filter 24, the equation Yn = Xn - Xn_2 is of applicable level where Yn designates the signal in the control unit 4 at this time and Xn designates the output level of the analog transmitter 16. It is necessary that Yn corresponds to one of the P1191 / 98MX levels of the law of quantification S to reduce the influence of noise. Consequently, the following relationship should be verified: Xn = Xn_2 + Sj If precautions are not taken, by following this relationship can lead to values too large for Xn. Several techniques, known as "line coding" are available to solve this problem, for example in the form of a line coder 27. At this point, the person skilled in the art will be able to easily select one in particular. The analog adapter must also eliminate its own echo, in the same way as the digital adapter 5. The techniques for this are well known and such an instrumentation appears in Figure 4, in the form of an echo filter 22. In the 4, the signal Yn (in this case corrupted by noise) is quantized and encoded in an octet that is transmitted to the receiving part 12 of the digital adapter 5, illustrated below Figure 3. There, the octets are transformed into linear levels by the linear conversion block 28 (using for example the conversion law A), and the echo of the signal emitted by the digital transmitter 11 is subtracted at 29, as shown in Figure 3. The resulting signal is treated P1191 / 98MX then by a Viterbi type algorithm in the functional block 30, or by a decision return system, and the output of the block 30 is transmitted, possibly through a buffer 31, to the user of the numerical adapter 5. As shown in Figure 3, the error signal (difference between the received signal and the ideal signal) in block 30 of the Viterbi algorithm or the decision return system is used to adapt to the echo canceller 22 and to estimate the error due to a poor synthesis of the pre-distortion filter 24 in the analog adapter 6. The correction information (coded to a low capacity) is multiplexed in the level selector 14 with the information coming from the user, connected to the input of the digital adapter 5 (service channel), and it is transmitted to the analog adapter 6. It is used in the analog adapter to adapt the pre-distortion filter 24. As shown in Figure 4, the error signal in block 20 corresponds to the Viterbi algorithm or the decision return system is used by adaptation algorithms 34 to adjust the echo filter 22 ', the adaptive linear equalizer 17 and the local clock 23. It is evident that as in the communications of P1191 / 98MX classic modem, recognition and learning sequences should be exchanged when communication is established. This is used to initialize clocks and adaptable filters. We must also foresee that one or another of the telephone exchanges 3, 4, can use either the law A or the law μ, or adapt accordingly. From the above it is that the invention achieves its objectives and allows joining a number line with an analog line to send directly and inexpensively the numerical information, without having to emulate an analog signal. This allows transmissions at a speed substantially equal to that of a numerical line at a relatively high capacity, all with the use of a normal telephone line, for transmission.

P1191 / 98 X

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. Communication device between a numerical adapter linked to a central unit by means of an interface number, namely the ISDN type, and an analog adapter linked to a central unit by means of an analog interface, said exchanges are linked by means of a telecommunications network, characterized in that it comprises means of direct connection between the digital adapter and the analog adapter , the numeric information of the numerical adapter is sent to the analog adapter and, reciprocally, directly in numerical form without emulating an analog signal. Communication device according to claim 1, characterized in that the direct connection means comprise, in the transmission direction of the digital adapter towards the analog adapter, a digital transmitter located in the digital adapter and capable of transmitting to a receiver Analog analogue located on the analog adapter, analog pulses whose voltage levels represent the information transmitted from the numerical adapter to the analog adapter. P1191 / 98 X 3. Communication device according to claim 1 or 2, characterized in that the direct connection means comprise, in the direction of transmission that the analog adapter has to the digital adapter, an analog transmitter located in the analog adapter and capable of transmitting to a digital receiver , located in the numerical adapter, an analog signal such that during its sampling by the analog interface of the control panel, a quantization level determined by a numerical information transmitted by the analog adapter to the numerical adapter will be valid. Communication device according to claim 2 or 3, characterized in that the analog receiver comprises an adaptive linear equalizer connected by its input to the output of an analog / digital converter, and connected by its output to the input of a connected output equalizer. to the user's equipment, so that the response at the output of the adaptive linear equalizer is a class IV response. Communication device according to claim 4, characterized in that the output equalizer is a decision return equalizer or a Viterbi-type equalizer. 6. Communication device according to claim 2, characterized in that the transmitter of the P1191 / 98MX analog adapter comprises a line encoder followed by a pre-distortion filter that synthesizes a partial class IV response. 7. Communication device according to claim 1, characterized in that said means comprise, on one side of the numerical adapter, a n-level selector, where n is practically equal to 64, represented in the form of octets, between N = 256 levels of possible quantification, said level selector is connected to the input of the user equipment and to the output of a numerical interface. Communication device according to claim 7, characterized in that the digital adapter comprises a line and channel decoder connected by its input to the digital interface output of the digital adapter, said line and channel decoder is connected by its output to the user's team. 9. Procedure for transmitting a digital adapter to an analog adapter in a digital communication network, characterized in that it comprises the steps of: taking a group of bits that come from a source of numerical data, for example a group of 6 bits; select one among n (n 64) levels P1191 / 98MX preselected between N (namely N = 256) voltage levels, each level is represented numerically by one octet; successively send the octets corresponding to the selection of one between n levels through the digital network towards an analog adapter, so as to produce in the analog adapter levels whose amplitude is practically equal to the levels represented by each octet, the signals that correspond to successive octets interfere with each other to produce an analog signal resulting in the analog adapter; equalizing said resulting analog signals in order to eliminate the interferences; measure the amplitude of the resulting analog signal and deduce the numerical value of the octet; from the numerical value of the octet, reconstitute the group of bits and send it to a receiver of numerical data. 10. Procedure for transmitting an analog adapter to a digital adapter in a communication system, characterized in that it comprises the steps consisting of: taking a group of bits that come from a data source connected to the communication system; select an analog signal that has a P1191 / 98MX amplitude corresponding to the numerical value of the group of bits, the signals corresponding to the successive groups interfere with each other and have a form such that at the moment in which the analog signal is sampled at the analog interface of the exchange, its value is substantially equal to a quantization level between N predetermined quantization levels, so that after sampling of the analog signal, an octet appears in the numerical adapter representing the quantization level; treat the successive octets in order to eliminate the transfer between successive levels and recover the value of the groups of bits; transmit the numerical value of the bit groups retrieved on the user's equipment. P1191 / 98MX