DE10136661C1 - Transmitter for data communication system has 2 transmission units supplied with clock signals offset for reducing cross-talk between their transmission signals - Google Patents

Abstract

The transmitter has 2 transmission units, supplying modulated periodic transmission signals (15') to one or more receivers via respective transmission lines, each transmitted bit or bit sequence of a transmission signal having a given amplitude and phase relative to the transmitter clock signal (T'), with a given offset between the clock signals for the 2 transmission units, for reducing cross-talk. Also included are Independent claims for the following: a data communication system; a data communication method.

Description

The invention relates to a transmission device according to Oberbe handle of claim 1, a data communication system with egg ner such a transmission device, and a data transmission method according to the preamble of claim 14.

Data communication systems have i. A. a broadcast or Sen de / receiving device, from which transmission signals to one or more receiving or transmitting / receiving units transmitted, and vice versa. The sending device can z. B. one in an EWSD terminal exchange (EWSD = Elek electronic dialing system) intended electronic construction group that has several modems. On every modem is a subscriber line connected via the because modulated transmission signals z. B. one on one Subscriber end connection provided modem are transmitted (and from the one corresponding to the central office modem Transmission signals are received).

The data communication between the modems (modulator Demodulators) can e.g. B. based on POTS- (Plain Old Tele phone service), ISDN (Integrated Services Digital Network), or xDSL (x Digital Subscriber Line) data transfer pro toolls take place, e.g. B. by means of ADSL data transmission or according to the standards ITU G.992.1 (G.dmt) or ITU G.992.2 (G.lite).

In data communication according to an xDSL protocol several frequency bands (bins) are used, which are above the Frequency bands used for POTS or ISDN data transmission lie. To transmit data in a certain Fre quenzband can e.g. B. a cosine oscillation can be used, whose frequency z. B. in the middle of the corresponding frequency  bands lies. For example, each bit to be transmitted or each bit sequence to be transmitted (e.g. using a phase star) a cosine oscillation of certain ampli tude and phase must be assigned. From the amplitude and phase the respectively received cosine oscillation can be found in the Emp catching unit the respectively transmitted bit or the respectively ü transmitted bit sequence can be determined.

The respective modem sends the cosine vibrations with respect to time from a clock generator generated clock signal.

The clock signal can be decentralized, e.g. H. for each Modem of the central office or each subscriber line generated separately. The about the different participants Signals transmitted via mer lines are then not synchronized based, d. H. cannot be coordinated centrally the.

Alternatively, the different modems of the end operator lungsstelle z. B. via corresponding clock signal lines central system generated by a central clock generator received clock. The transmission signals are then over the various subscriber lines in isochronous manner ü transferred. However, you can choose between over neighboring part signals transmitted subscriber lines relatively high over speech disorders occur.

No. 6,144,695 A describes a data transmission method wrote, of several, indicated at a central station arranged transmitters out via appropriate transmission lines each during certain data transmission frames (frames) each a sequence of modulated, periodic Transmission signals transmitted to several receiving units become. Each bit or bit sequence is to be transmitted a transmission signal of certain amplitude and phase ver shift compared to one of the respective transmission unit  assigned clock assigned. To minimize crosstalk effects hold, it is proposed that the different broadcasting unit th assigned data transmission frames on to convey one another in an aligned manner.

A transmission device is known from US Pat. No. 5,991,311 which from a first and a second transmitter unit corresponding transmission lines modulated, periodic Transmission signals are transmitted. The transfer of the Signals are always related to one for the first and second transmission unit identical, central clock signal nal.

No. 5,887,032 A describes a data transmission method wrote, from several sending units over ent talking transmission lines modulated, periodic Transmit transmission signals to several receiving units and a transmission signal for each bit to be transmitted certain amplitude and phase shift compared to one is assigned to the respective transmission unit associated clock. With Sig received over a certain transmission line nalen becomes - by the transfer of data over the whose lines caused - crosstalk signal ge estimates, and subtracted from the received signals.

The object of the invention is a new type of data transfer method, a new type of data communication system, so like a new type of transmitter for use in one To provide data communication system.

The invention achieves this and other objectives through the Ge subjects of claims 1, 13 and 14. Advantageous further development endings of the invention are specified in the subclaims.  

According to a basic idea of the invention, transmission will be direction provided which a first transmitter unit, for. B. a first modem, and a second transmitter unit, e.g. B. a has a second modem, from which via appropriate Transmission lines modulated, periodic transmission signals to one or more receiving units, e.g. B. more Modems are transmitted, with each bit to be transmitted or bit sequence a transmission signal of a certain amplitude and Phase shift compared to one of the respective transmitters Unit assigned clock is characterized, characterized net that there is a time shift of the first transmission assigned clock to that of the second transmit Unit assigned clock is chosen so that the by Ü crosstalk effects between the transmission lines reduced impairments in the transmission quality be tied.

The time shift is particularly preferred for this purpose between the bars chosen so that from the first broadcast unit transmitted transmission signals orthogonal to that of transmission signals sent to the second transmission unit, or so that the orthogonality between the transfer signals nalen is increased. This leads to a reduction in the Crosstalk between the individual transmission lines caused disturbances - especially if the over transmission lines arranged in a common cable bundle are, d. H. side by side over a relatively large distance be performed lying down. With the invention can thus be achieved that - with the same data transfer rate - the bits error rate is reduced (or - with the same bit error rate - The data transfer rate is increased).

The transmitter is advantageously designed so that the temporal shift of the first transmitter unit assigned th clock compared to that assigned to the second transmitter unit Clock adjustable during the operation of the transmitter is.  

For example, the size of the time shift of the Bars should be chosen depending on whether the first and / or the second transmission unit with one or is connected to the plurality of receiving units or not.

In a further preferred embodiment of the invention the time shift depending on the mo selected transmission power of the respective transmission unit. As a result, the crosstalk influence of individual transmission si gnale estimated on other transmission signals, and z. B. the (orthogonal) distance from less strong transmission si gnalen to a stronger transmission signal accordingly fit, e.g. B. be increased.

The invention is based on several embodiments examples and the accompanying drawing explained. In the drawing shows:

Figure 1 is a schematic representation of a data communication system according to an embodiment of the invention.

FIG. 2 shows a schematic detailed illustration of the terminal exchange shown in FIG. 1;

Fig. 3 is a schematic representation of a phase star used for data transmission;

FIG. 4 shows a bit sequence assignment table used in the phase star shown in FIG. 3;

Fig. 5 is a in the prior art, and a cosine vibration used in the inven tion data communication system for data transmission.

In Fig. 1 a first embodiment of an OF INVENTION to the invention the data communication system 1 is shown.

In this, an end switch 3 (here: an EWSD end switch) is connected to a public or private telephone network 2 (EWSD = electronic digital dialing system).

The central office 4 has a number of modems (modulators / demodulators) 7 a, 7 b, the connection lines 5 a, 5 b, 5 c, 5 d to the corresponding modems provided for subscriber end connections 6 a, 6 b via a plurality of subscribers 8 a, 8 b are connected. As further shown in Fig. 1, a certain number of subscriber lines 5 a, 5 b, 5 c, 5 d are combined to form a cable bundle 4 a, 4 b.

The data communication between the end switching center 3 provided at the central office modems 7 a, 7 b, and the corresponding modems 8 a, 8 b provided at the subscriber end connections 6 a, 6 b can, for. B. by means of an xDSL protocol-based data transmission method (xDSL = xDi gital Subscriber Line).

For xDSL data transmission between the respective end switching center modem 7 a, 7 b and the corresponding subscriber modem 6 a, 6 b (or vice versa) z. B. a DMT process can be used (DMT = discrete multi tone). Here, as will be explained in more detail below, the data to be transmitted are coded in cosine oscillations 15 'of a certain amplitude and phase.

For coding z. B. the phase star 11 shown in FIG. 3 can be used. This has, for example, three concentric circles, each of which is assigned a vibration amplitude A1, A2, A3 of a certain height. On the circles are e.g. B. arranged a total of 16 points, each of which is assigned one of 16 different sequences of 4 bits.

For example, four points a, b, d, e, each lying at an angle ϕ1, ϕ2, ϕ3 or bzw.4 of 45 °, 135 °, 225 ° or 315 ° on the innermost circle assigned to the first amplitude A1, according to the embodiment shown in Fig. 4 assignment Table 12 respectively, the bit sequence "1010", "0101", 1001 "and" 0110 "associated with. in a corresponding way is shown in FIG. 3, four wide reindeer, at corresponding angles φ1, φ2, φ3 or ϕ4 of 45 °, 135 °, 225 ° or 315 ° on the outermost circle assigned to the third amplitude A3 according to the assignment table 12 shown in FIG. 4, the bit sequence "1100", "1111", "0000""or" 0011 "assigned, eg a point c the bit sequence" 1100 "and a point f the bit sequence" 1111 ".

The remaining bit sequences ("1101", "1110", 1000 "," 1011 "," 0100, 0111 "," 0001 "," 0010 ") are assigned to 8 points which lie on the middle circle assigned to the second amplitude A2 , namely at angles ϕ5, ϕ6, ϕ7, ϕ8, ϕ9, ϕ10, ϕ11 and ϕ12 of approx. 20 °, 70 °, 110 °, 160 °, 200 °, 250 °, 290 ° and 340 °. For the transmission of data from the transmitter to the receiver (e.g. from the central office modem 7 a, 7 b to the respective subscriber modem 8 a, 8 b (and vice versa)), a sequence of cosine-shaped oscillations 15 'that lasts for a certain period of time transfer.

Each cosine wave 15 'each denotes a limited hours te the above bit sequences, and supply amplitude via the height of the oscillations A1, A2, A3, and opposite a for example on the phase shift Δφ of the respective vibration in the transmitter (. The terminating exchanges modem 7 a ) and in the receiver (z. B. the subscriber line modem 8 a) synchronized - with respect to a central clock signal T time-shifted - clock signal T '(see below).

The amplitude A1, A2, A3 used in each case corresponds to that amplitude which is assigned to that circle of the phase star 11 shown in FIG. 3, on which the point a, b, c, d, e, f lies, to which the respective transmitting bit sequence is assigned.

In a corresponding manner, the phase shift Δϕ of the respective cosine oscillation is selected such that it corresponds to the above-mentioned angle ϕ1, ϕ2, ϕ3, ϕ4, ϕ5, ϕ6, ϕ7, ϕ8, ϕ9, ϕ10, ϕ11 or ϕ12 of the point assigned to the respective bit sequence to be transmitted tes a, b, c, d, e, f in phase star 11 corresponds.

As shown in Fig. 2, the end office 3 has a plurality of electrical assembly modules 13 a, 13 b (z. B. several more inserted into corresponding slots of the end office 3 ). Corresponding to the number of subscriber lines 5 a, 5 b provided in each case in a cable bundle 4 a, several assembly modules 13 a, 13 b are combined to form an assembly meta module 15 a, 15 b.

Furthermore, the central office 3 has a central clock generator 16 . This delivers the above-mentioned uniform, central clock signal T to each module 13 a, 13 b via a central bus system 17 , in particular via one or more bus system clock lines.

The assembly modules 13 a, 13 b are all constructed in a correspondingly similar manner, as will be explained in more detail below using the example of the first assembly module 13 a: There are several on each assembly module 13 a (e.g. 8 or 16 ) Modems 7 a, 7 b or modem circuits arranged. Each modem 7 a, 7 b is connected to the corresponding subscriber line 5 a via a corresponding connection line 14 provided on the respective module 13 a.

Furthermore, each modem 7 a is connected via a line 18 to a phase shifter 19 (or a clock delay device), which via an internal module bus system 20 (or its clock line) connected to the central bus system 17 or its clock line central clock signal T is supplied. From the respective phase shifter 19 from the respective modem 7 is a according to Figure 5, below a signal derived from the central clock signal T control signal. (Here:... A by a time period .DELTA.t1 .DELTA.t2, opposite the central clock signal T time-shifted clock signal T ') made available. It is thereby achieved that all of each weiligen modem 7 a cosinusoidal output 15 'to a phase shift of Δθ1, Δθ2. , , are shifted in relation to a corresponding cosine oscillation 15 related to the central clock signal T (or respectively by a certain time period Δt1, Δt2,... with respect to the positive edge of the central clock signal T).

For example, with the embodiment shown, the above-mentioned bit string c = encoded in Fig. 5 from the first modem 7 a with respect to the time-shifted clock signal T 'emitted cosine wave 15' through the amplitude A3, and whose phase shift Δφ = 135 ° "1100". Also shown in Figure 5 is a -. The cosine wave 15 'appropriately in relation to the instantaneous central clock signal T wave oscillation Cosi 15 - not used herein.

Referring back to FIG. 2, the central office 3 has a central control device 21 , which is also connected to the central bus system 17 , and via corresponding (control) lines of the central bus system 17 and the corresponding module bus systems 20 with all of them End switch existing phase shifters 19 is in connection. By sending appropriate control signals via the bus system 17 and the corresponding module bus systems 20 may by the central control device 21 from - individually for each phase shifter 19 and each modem 7 a, 7 b - the duration .DELTA.t1 .DELTA.t2. , , can be set by which the clock signals T 'output by the respective phase shifters 19 are shifted in time with respect to the central clock signal T.

The setting of the clock shift periods Δt1, Δt2,. , , can e.g. B. by a technician of the operator of the central office 3 before the actual use of the central office 3 , or during a business interruption Be, z. B. by entering appropriate commands in an input device 22 provided in the control device 21 , z. B. a keyboard. The input device 22 can alternatively, for. B. also be connected via the bus system 17 to the control device 21 .

Alternatively, a software program can be loaded on a storage device, not shown, which, for. B. automatically at startup of the central office 3, the Steuerein device 21 causes appropriate control signals for a setting of the clock shift durations Δt1, Δt2,. , , to be sent to the phase shifters 19 via the bus system 17 and the corresponding module bus systems 20 .

In an alternative embodiment, the various phase shifters 19 have been set in advance (for example, prior to installation in the central office 3 ) so that they have clock shifts of different durations Δt1, Δt2,. , , cause.

The cycle shift periods Δt1, Δt2,. , , relatively short, especially so short that the difference (Δϑ1 - Δϑ2) between the above phase shifts Δϑ1, Δϑ2 of connection lines 5 a, 5 b transmitted via different subscriber lines 5 a, 5 b (e.g. by half) is smaller than the smallest occurring A difference (e.g. Δϕ1 - Δϕ2) between - transmitted via the same subscriber line 5 a, different bit sequences characterizing - cosine oscillations 15 '.

In particular, the clock shift periods Δt1, Δt2,. , , are chosen so that the arranged in the same cable bundle 4 a subscriber lines 5 a from transmitted cosine vibrations 15 'are orthogonal to one another, or their orthogonality is increased compared to conventional processes. This leads to a reduction in interference caused by crosstalk between the individual subscriber lines 5 a running in a cable bundle del a. As a result, the bit error rate can be reduced with the same data transfer rate or the data transfer rate can be increased with the same bit error rate.

In an alternative embodiment, the clock shift duration settings of the phase shifters 19 are automatically changed during the operation of the central office 3 , e.g. B. adaptively depending on the change in one or more operating parameters.

For example, a signal is sent from each modem 7 a, 7 b via the respective module bus system 20 and the central bus system 17 to the central control device 21 , which indicates whether the respective (switching center) modem 7 a, 7 b is currently is connected to the corresponding (subscriber end connection) modem 8 a or not. Alternatively, from each modem 7 a, 7 b just connected, a further signal can be sent to the central control device 21 via the respective module bus system 20 and the central bus system 17 , with which the current modem transmission power is displayed.

The control means are in the control device 21 then 21 stored control software program in response to the above-mentioned operating parameters (number of currently (on a particular cable bundle 4 a, 4 b) modems 7 connected to a through a (not shown) on the storage device, 7 b , Transmit power of the connected modems 7 a, 7 b, etc.) the clock shift periods Δt1, Δt2, each to be used. , , determined. Then, the control device 21 sends corresponding control signals via the bus system 17 and the corresponding module bus systems 20 to the respective phase shifter 19 , and thus the clock displacement periods Δt1, Δt2 caused by these are adjusted or adjusted. As a result, the transmission errors attributable to crosstalk can be further reduced.

Alternatively or additionally, e.g. B. from the (switching center) modems 7 a, 7 b connected (subscriber end connection) modems 8 a, 8 b, feedback about the current transmission quality is given (e.g. by reference data sequences to the respective (subscriber end connection) ) Modem 8 a, 8 b are transmitted, the current bit error rate is determined there, and this is communicated to the respective (switching center) modem 7 a, 7 b). The control software program can then continuously adapt the clock shift periods Δt1, Δt2 used in the course of a “learning process”, and thus further reduce the bit error rate.

LIST OF REFERENCE NUMBERS

1

Data communication system

2

telephone network

3

local exchange

4

a Bundle of cables

4

b Cable bundle

5

a Subscriber line

5

b Subscriber line

5

c Subscriber line

5

d subscriber line

6

a Subscriber end connection

6

b Subscriber end connection

7

a modem

7

b Modem

8th

a modem

8th

b Modem

11

phase star

12

allocation table

13

a module

13

b module

14

connecting line

15

cosine wave

15

'Cosine vibration

15

a meta module

15

b Meta module

16

clock generator

17

bus system

18

management

19

phase shifter

20

Module bus system

21

control device

22

input device

Claims (16)

1. Transmitting device ( 3 ), which has a first transmitting unit ( 7 a), and a second transmitting unit ( 7 b), from which, via corresponding transmission lines ( 5 a, 5 b), modulated periodic transmission signals ( 15 ') to one or several receiving units ( 8 a, 8 b) are transmitted, with each bit or bit sequence (c) to be transmitted a transmission signal ( 15 ') of a certain amplitude (A1) and phase shift (ϕ1) with respect to one of the respective transmission units ( 7 a, 7 b) is assigned to the assigned clock (T '), characterized in that a time shift of the clock (T') assigned to the first transmitter unit ( 7 a) relative to the clock assigned to the second transmitter unit ( 7 b) is selected such that the impairments in the transmission quality caused by crosstalk effects between the transmission lines ( 5 a, 5 b) are reduced. 2. Transmitting device ( 3 ) according to claim 1, in which the time shift between the clocks (T ') is selected such that the transmission signals ( 15 ') transmitted by the first transmitting unit ( 7 a) are orthogonal to that of the second transmitting unit ( 7 b) are transmitted transmission signals, or so that the orthogonality between the transmission signals ( 15 ') is increased. 3. Transmitting device ( 3 ) according to claim 1 or 2, which has a central control device ( 21 ) which, by providing corresponding control signals, the time shift of the clock of the first transmitting unit ( 7 a) assigned (T ') compared to that of the second transmitting unit ( 7 b) causes the associated clock. 4. Sending device ( 3 ) according to one of the preceding claims, which also has a central clock generator ( 16 ) which provides a central system clock (T), and at least one clock delay device ( 19 ), and in which the time shift of the first transmission Unit ( 7 a) associated clock (T ') compared to the clock assigned to the second transmitter unit ( 7 b) is achieved in that the system clock (T) is supplied to the at least one clock delay device ( 19 ) which generates a delayed clock therefrom , which is then fed to the first or second transmitter unit ( 7 a, 7 b). 5. Transmitting device ( 3 ) according to one of the preceding claims, which is designed such that the temporal shift of the first transmitting unit ( 7 a) associated clock (T ') relative to the clock assigned to the second transmitting unit ( 7 b) before start-up the transmission device ( 3 ) is adjustable. 6. Transmitting device ( 3 ) according to one of the preceding claims, which is designed such that the temporal shift of the first transmitting unit ( 7 a) associated clock (T ') compared to the second transmitting unit ( 7 b) assigned clock during the Operation of the transmitter ( 3 ) is adjustable bar. 7. Transmitting device ( 3 ) according to claim 6, in which the time shift is selected depending on whether the first and / or the second transmitting unit ( 7 a, 7 b) just with the one or more receiving units ( 8 a, 8 b) is connected or not. 8. Transmitting device ( 3 ) according to claim 7, in which the time shift is selected as a function of the instantaneous transmitting power of the respective transmitting unit ( 7 a, 7 b). 9.. Transmitting device ( 3 ) according to one of the preceding claims, in which the transmission lines ( 5 a, 5 b) assigned to the first and the second transmitting unit ( 7 a, 7 b) are arranged in the same cable bundle ( 4 a). 10. Transmitting device ( 3 ) according to one of the preceding claims, in which the transmitting units ( 7 a, 7 b) are modems. 11. Transmitting device ( 3 ) according to one of the preceding claims, in which the periodic transmission signals ( 15 ') are cosine or sine waves. 12. Transmitting device ( 3 ) according to one of the preceding claims, in which the time shift is determined by a control device configured to be capable of learning. 13. Data communication system ( 1 ), with at least one receiving unit ( 8 a, 8 b), and with a transmitting device ( 3 ) according to one of claims 1 to 12. 14. Data transmission method, in particular for use in a data communication system according to claim 13, wherein from a first transmission unit ( 7 a) and a second transmission unit ( 7 b) from corresponding transmission lines ( 5 a, 5 b) modulated, periodic transmission signals ( 15 ' ) to one or more receiving units ( 8 a, 8 b) who the, and each bit or bit sequence (c) to be transmitted a transmission signal ( 15 ') of certain amplitude (A1) and phase shift (ϕ1) with respect to one of the respective transmission unit ( 7 a, 7 b) is assigned to the associated clock (T '), characterized in that the method comprises the step:

• - Time shift of the first transmitter unit ( 7 a) assigned clock (T ') relative to the second transmitter unit ( 7 b) assigned clock such that the cross-talk effects between the transmission lines ( 5 a, 5 b) cause adverse effects the transmission quality can be reduced.

15. The method according to claim 14, wherein the temporal shift between the clocks (T ') is selected so that the transmission signals transmitted by the first transmission unit ( 7 a) ( 15 ') orthogonal to that of the second transmission unit ( 7 b ) are transmitted transmission signals, or so that the orthogonality between the transmission signals ( 15 ') is increased. 16. The method of claim 14 or 15, further comprising the steps of:

• - Providing a central system clock (T);
• - Feeding the central system clock (T) to a clock delay device ( 19 ); and
• - Feeding a delayed clock output from the clock delay device ( 19 ) to the first or second transmitter unit ( 7 a, 7 b).