DE10129324B4 - Method for interoperably operating xDSL modems - Google Patents

Abstract

Data communication system (1) having a transmitting unit (3a) at the location A, of which out over a transmission channel (4) modulated transmission signals (9) are transmitted to a receiving unit (5a) at location B, each one bit to be transmitted or bit string (a) a transmission signal (9) associated with certain amplitude (A1) and phase (φ1) is characterized the transmission unit (3a) has a control device (12, 14), which is designed and furnished in conjunction with the test result obtained by the receiving unit and the configuration the receiving unit an adaptation of the transmitted signals and / or the properties of the transmitting unit to properties of the transmission channel and / or the receiving unit (5a) is caused.

Description

The The invention relates to a data communication system according to the preamble of claim 1, a transmitting and receiving unit for use in such a system, as well as a data transmission method according to the preamble of claim 12.

Data communication systems i.A. a transmitting unit, e.g. one in an EWSD terminal provided first modem, from where modulated transmission signals over a transmission channel to a receiving unit, e.g., to a second, in a subscriber terminal transmitted modem become.

The Data communication between the modems (modulator-demodulators) can e.g. using POTS (Plain Old Telephone Service) or ISDN (Integrated Services Digital Network), and via xDSL (x Digital Subscriber Line), e.g. via ADSL data transmission respectively.

to xDSL data transmission be multiple frequency bands (bins), which are above that for POTS or ISDN data transmission used frequency bands lie. For transmission of data in a particular frequency band can e.g. a cosine (or sinusoidal) vibration whose frequency is e.g. in the center of the corresponding frequency band is located.

For example can be transmitted to anyone Bit or each to be transmitted Bit sequence (e.g., using a phase star) a cosine wave be assigned to certain amplitude and phase. Will this on transmit the receiving unit, can be calculated from the amplitude and phase of each received cosine oscillation determines the respectively transmitted bit sequence in the receiving unit become.

DSL standards, e.g. ITU G.992.1 (G.dmt) or ITU G.992.2 (G.Lite) leave what the Details of the data transmission protocol used in each case during data transmission concerns certain freedoms too. In addition, the DSL standard is not of is adhered to correctly by modem manufacturers. That is why the interoperability be restricted between the modems used.

Out the publication font WO 00/79693 A1 discloses a Hybrit circuit in which an impedance matching is performed on a connecting line.

The Invention has for its object, a novel data transmission method, a novel Data communication system, as well as novel transmitting and receiving units for use in such a system put.

The Invention achieves this and other goals by the objects of claims 1, 10, 11 and 12. Advantageous developments of the invention are in the subclaims specified.

According to one The basic idea of the invention is to provide a data communication system. which has a transmitting unit, from which via a transmission channel modulated transmission signals transmitted to a receiving unit be transferred to each one Bit or bit sequence a transmission signal assigned to certain amplitude and phase, characterized the transmission unit has a control device which is designed in this way and is set up by them to adapt the transferred Signals and / or properties of the transmitting unit to properties the transmission channel and / or the receiving unit is caused.

By automatic adjustment may require manual adjustment of the transmission or receiving unit can be avoided or simplified on site.

in the The following is the invention with reference to several embodiments and the attached drawing explained in more detail. In the drawing shows:

1 a data communication system using the data transmission method of the present invention;

2 a schematic representation of several frequency bands used in the data transmission method according to the invention;

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

3b one at the 3a shown phase star bitmap assignment table used;

4 a schematic representation of a cosine used for data transmission;

5 a schematic representation of another used for data transmission cosine oscillation;

6 a schematic representation of a third used for data transmission cosine oscillation;

7 a schematic detail of the in 1 shown modems, as well as the subscriber line;

8th a schematic representation of a measuring arrangement for determining the impedance of in 1 shown transmission channel;

9 a further, schematic detail of one of in 1 and 7 shown modems;

10 a schematic detail of the in 9 shown digital filter.

In 1 is an example of a data communication system 1 in which the data transmission method according to the invention can be used.

The data communication system 1 has one to a telephone network (here: the public telephone network 2 ) affiliated local exchange 3 (here: an electronic dialing system digital or EWSD). The terminus 3 is over several subscriber lines 4 with multiple subscriber end-user devices 5 connected.

Data communication between the local exchange 3 and the respective subscriber end device 5 (or between the respectively provided there modems (modulator-demodulators) 3a . 5a ) can be done eg by means of POTS (Plain Old Telephone Service) or ISDN (Integrated Services Digital Network), and by means of xDSL (x Digital Subscriber Line), eg by means of ADSL data transmission.

For DSL data transmission according to 2 several frequency bands (bins) 6a . 6b . 6c . 6d used, which are above a frequency f1. The frequency ranges below the frequency f1 (f1 ≅ 25 kHz for POTS or f1 ≅ 130 kHz for ISDN) are used for conventional POTS or ISDN (voice) data transmission.

For DSL data transfer between between the central office modem 3a and the subscriber modem 5a (or vice versa), for example, a DTM method can be used (DTM = discrete multi tone). Here are for each frequency band 6a . 6b . 6c . 6d . 6e Cosine oscillations used, whose frequency, for example, respectively in the middle of the corresponding frequency band 6a . 6b . 6c . 6d . 6e can lie.

For coding the data to be transmitted in a cosine oscillation can according to 3a a phase star 7 be used. This has three concentric circles, each associated with a vibration amplitude A1, A2, A3 of certain height. On the circles a total of 16 points are arranged, each of which is assigned one of 16 different sequences of 4 bits.

For example, four points a, b, d, e are each at an angle φ1, φ2, φ3 and φ4 of 45 °, 135 °, 225 ° and 315 °, respectively, on the innermost circle associated with the first amplitude A1, according to the in 3b shown allocation table 8th in each case assigned the bit sequence "1010", "0101", "1001" or "0110". In a corresponding manner is according to 3a four further points c, f lying at corresponding angles φ1, φ2, φ3 and φ4, respectively, of 45 °, 135 °, 225 ° and 315 °, respectively, on the outermost circle associated with the third amplitude A3 according to FIG 3b shown allocation table 8th each assigned the bit sequence "1100", "1111", "0000" or "0011".

The remaining bit sequences ("1101", "1110", "1000", "1011", "0100", "0111", "0001", "0010") are 8 points assigned to the middle, the second amplitude A2 assigned Are each at angles φ5, φ6, φ7, φ8, φ9, φ10, φ11 and φ12 of about 20 °, 70 °, 110 °, 160 °, 200 °, 250 °, 290 ° and 340, respectively °.

To transfer data from the sender to the receiver (eg from the central office modem 3a to the subscriber modem 5a , and vice versa) becomes a sequence of several cosine oscillations transmitted in succession, each lasting a certain period of time 9 . 10 . 11 (see. 4 . 5 . 6 ) transfer.

In every frequency band 6a . 6b . 6c . 6d . 6e show all used cosine oscillations 9 . 10 . 11 in each case the same, constant, predetermined frequency. Every cosine oscillation 9 . 10 . 11 indicates in each case a specific one of the above-mentioned bit sequences, specifically via the height of the oscillation amplitude A1, A2, A3, and via the phase shift Δφ of the respective oscillation 9 . 10 . 11 in relation to a basic clock synchronously running in the transmitter and in the receiver (or in relation to a pilot tone emitted according to the representation below by the respective transmitter).

The amplitude A1, A2, A3 used in each case corresponds to that amplitude which corresponds to that of the circle in 3a shown phase star 7 is assigned, on which the point a, b, c, d, e, f is located, which is assigned to each bit sequence to be transmitted.

In a corresponding way, the phase shift Δφ of the respective cosine oscillation 9 . 10 . 11 selected such that they correspond to the aforementioned angle φ1, φ2, φ3, φ4, φ5, φ6, φ7, φ8, φ9, φ10, φ11 and φ12 of the point a, b, c, d, e assigned to the respective bit sequence to be transmitted. f in the phase star 7 equivalent.

For example, the in 4 shown cosine oscillation 9 by their amplitude A1, and their phase shift of Δφ = 45 ° which the point a on the phase star 7 associated bit string "1010", which is in 5 shown cosine oscillation 10 by the amplitude A1, and the phase shift of Δφ = 135 °, the bit sequence "1001" assigned to the point d, and the in 6 shown cosine oscillation 11 by the amplitude A3, and the phase shift of Δφ = 135 °, the bit sequence "1100" assigned to the point c.

For example, if a data sequence "101010011100" to the respective receiver, eg to the subscriber modem 5a , can be transmitted from the respective sender, eg from the central office modem 3a , one after the other in the 4 . 5 and 6 shown cosine oscillations 9 . 10 . 11 to be sent out.

In the receiver, the amplitude A1, A2, A3 and phase shift of each received cosine oscillation 9 . 10 . 11 determined, and then - using the in 3a shown phase star 7 - The respectively determined amplitude A1, A2, A3 and phase shift associated bit sequence.

Of the xDSL standard, especially in the present embodiment applied standards ITU G.992.1 (G.dmt) and ITU G.992.2 (G.Lite) Leave what the details of each in the data transfer used data transmission protocol concerns certain freedoms too. It also becomes the xDSL standard not correctly adhered to by all modem manufacturers.

To - eg when using modems 3a . 5a In order to ensure interoperability, and / or to increase the data rate and / or to reduce the bit error rate, the data transmission according to the present invention is automatically transmitted to each other at the start of transmission and / or during the transmission of data modems 3a . 5a , and / or adapted to the prevailing channel characteristics. The adaptation of individual parameters of the data transmission takes place according to 7 under control of each provided in the transmitter and receiver microprocessors 12 . 13 , On these runs in a storage device 14 . 15 of the respective modem 3a . 5a stored data transfer control software program.

The control software program causes, for example, that the predistortion of the respectively transmitting modem 3a . 5a ausgegeneten cosine oscillations 9 . 10 . 11 is adjusted or adjusted.

In the transmission of cosine oscillations 9 . 10 . 11 via the subscriber line 4 it comes to various distortions, eg to (additional unwanted) phase shifts, to different amplitude attenuations, etc. To compensate for the distortions, every cosine oscillation 9 . 10 . 11 according to 4 predistorted emitted, ie with a (slightly) different amplitude (amplitude of the height A1 'instead of the height A1) and phase shift (phase shift Δφ' instead of Δφ), as in undistorted transmission. The receiver sends out a cosine oscillation - predistorted 9 ' Due to the channel distortion, received signals essentially correspond to the signals which the receiver would receive, if-in the case of an undistorted channel-the cosine oscillation 9 would be sent out without predistortion.

In order to determine the respectively optimal predistortion, for example, initiated and controlled by the data transfer control software program, before the actual data transmission (with connected or not connected receiver) and / or at predetermined or freely selectable times during the data transmission by the transmitter several (test) pulses are sent out. The temporal position and the shape of the pulses reflected back to the transmitter can be used in a manner known per se for the different frequency bands 6a . 6b . 6c . 6d . 6e the respective channel properties, in particular the above-mentioned distortions, are determined.

Alternatively, for example, once again initiated and controlled by the data transfer control software program, one or more (test) cosine oscillations may be generated by the transmitter prior to the actual data transmission and / or at predetermined or arbitrary times during data transmission 9 with predetermined, in the respective storage device 14 stored amplitude height A1 and phase shift Δφ are transmitted to the receiver.

In the receiver, the amplitude A1 "and the phase shift Δφ" of the respective received (test) cosine oscillation 9 '' determined, and with a - in the respective memory device 15 stored - expected amplitude A1 _erw and expected phase shift Δφ _erw compared. From the difference between the expected and received amplitude or phase shift, the predistortion to be used by the transmitter can be determined in the receiver (or alternatively in the transmitter) (eg according to the formulas: predistorted amplitude height A1 '= A1 - (A''- A1 _erw ) or predistorted phase shift Δφ' = Δφ - (Δφ '' - Δφ _erw )).

Alternatively or additionally, the respective transmitter - again caused by and controlled by the data transfer control software program - before starting the actual data transmission and / or at predetermined freely selectable times during the data transmission through an impedance matching. For this purpose - as in 8th is shown schematically - from the transmitter, eg from the modem 3a (and / or from the modem 5a ) off for the different frequency bands 6a . 6b . 6c . 6d . 6e or frequencies the impedance Z (f) of the transmission channel (ie the subscriber line 4 if the modem is connected or not connected 5a , in 8th through a black box 16 illustrated). Then (again controlled by the control software program) in dependence on the determined transmission channel impedance Z (f), the impedance Z _i (f) of the transmitter adapted (eg identical as the respectively determined transmission channel impedance Z (f) selected).

Alternatively or additionally, a pilot tone adaptation can be carried out by the respective transmitter-again initiated and controlled by the data transmission control software program-before the actual data transmission and / or at predetermined or freely selectable times during the data transmission:
According to the DSL standard, one or more of the in 2 shown frequency bands 6a . 6b . 6c . 6d transmit one or more pilot tones. The pilot tones are cosine oscillations of a specific, fixed frequency which, in contrast to those in 4 . 5 and 6 shown cosine vibrations 9 . 10 . 11 not for the transmission of the (actual) payload data (here: the bit sequences a, b, c, d, e, f) are used, but for the transmission of additional information, in particular for setting the synchronously running as described above in the transmitter and receiver basic clock used become.

The pilot tones have - in contrast to the above-mentioned user data transmission cosine oscillations 9 . 10 . 11 - a constant amplitude and phase up.

In the aforementioned pilot tone adjustment initiated and controlled by the data transfer control software program, before and / or during the actual data transfer, the phasing of the pilot tone cosine oscillation is related to the payload cosine oscillations 9 . 10 . 11 set.

For example For this purpose, one or more (test) pulses from the respective transmitter sent out, and from the temporal location and / or the form of the Transmitter (back) reflected Pulses in a known per se for the pilot tone frequency the respective Channel properties, in particular phase distortions determined. The pilot tone cosine oscillation will then in the future with a phase shift sent out that's so big that the determined phase distortion is compensated.

Alternatively or additionally - again caused by and controlled by the data transfer control software program - before starting the actual data transmission and / or at predetermined or arbitrary times during the data transmission, a setting of a according to 9 in the respective modem 3a . 5a provided, a regulator 18 and a digital filter 19 having echo compensation device 17 carried out.

That of the respective modem 3a . 5a output signal A is at joints of the subscriber line 4 reflected, resulting in a contribution of the output signal A to the opposite direction ("echo signal"). In order to eliminate the echo signal, the digital filter generates an (estimated) duplicate of the echo signal (signal Y), and this from the respective modem 3a . 5a received input signal B deducted.

As in 10 is shown has the digital filter 19 a number N of filter stages, namely a first filter stage 23 , as well as further filter stages 24 . 25 , Each filter stage comprises a delay element 20 (in alternative embodiments: two delay elements), two multipliers 21 , and an adder 22 (only the first and the last, N-th stage is simpler). The number N of filter stages 23 . 24 . 25 indicates the order of the filter.

The multiplier 21 multiply the respective signals by - from the controller 18 determined - adjustable filter coefficients α ₀ , α ₁ , α ₂ , ..., α _N , β ₁ , β ₂ , ..., β _N. The multiplied signals are then sent to the respective adder 22 , and from there the respective delay element 20 fed.

The regulator 18 For example, it is configured such that it sets the filter coefficients α ₀ , α ₁ , α ₂ ,..., α _N , β ₁ , β ₂ ,..., β _N such that the cross-correlation function of the in 9 shown, from the modem 3a . 5a output signal A, and the input signal B becomes zero.

The higher the order N of in 10 shown filters 19 is, the better the echo signal is compensated. However, with higher filter order, the computing time required to determine the signals increases. According to the invention - caused by and controlled by the data transfer control software program - before the start of the actual data transmission and / or vorbe agreed or arbitrary times during data transmission, the order N and the coefficients of the filter set.

For example, for this purpose by the respective transmitter (modem 3a . 5a ) one or more (test) pulses emitted, and determines the strength of the resulting echo signals. For a relatively strong echo signal, a filter is selected to be relatively high, and for a relatively weak echo signal, a filter of relatively low order is selected.

Alternatively or additionally - again caused by and controlled by the data transfer control software program - determines how many bits per unit time on the respective in before the actual data transfer and / or at predetermined or freely selectable times during data transfer 2 shown frequency band 6a . 6b . 6c . 6d . 6e to be transferred. For this purpose, the quality of the respective transmission channel used is determined before and / or during the data transmission - for the respective frequency. This can be done, for example, by means of - in 4 . 5 . 6 shown cosine oscillations 9 . 10 . 11 corresponding cosine oscillations in addition to the actual user data and reference data from the transmitter to the receiver are transmitted, for example in the form of a sequence of reference data bits. In the storage device 14 . 15 the receiver stores a bit sequence identical to the transmitted reference data sequence. This is compared with the reference data sequence actually received by the transmitter. From the difference between the two bit sequences, the bit error rate, ie the quality of the respectively used transmission channel (ie the frequency band corresponding to the frequency of the respective cosine oscillation) can be determined.

The for the determined respective transmission channels Bit error rates are from the receiver transmitted to the transmitter.

This can then, for example, some or more, particularly severely disturbed frequency bands (eg the in 2 shown second frequency band 6b ) no longer use for data transmission (or previously used for data transmission frequency bands - due to improved transmission channel quality - henceforth for data transmission). The transmitter tells the receiver which frequency bands are used and which ones are not.

Alternatively or additionally, relative frequency bands of relatively low quality can henceforth transmit relatively fewer bits per unit of time, and relatively higher quality frequency bands henceforth transmit relatively more bits per unit of time. For this purpose, for example, the duration of a - each transmitting a bit sequence - cosine oscillation can be reduced or increased, and / or it can be used a different phase star than in 3a shown phase star 7 (For example, a phase star that encodes bit strings that have a higher or lower number of bits than those in 3b shown bit sequences a, b, c, d, e, f, for example, a phase star with a higher or lower number of concentric circles, and / or with a higher or lower number of arranged on a circle points, which (in total) a higher or less number of bit strings is allocated).

alternative or additionally can use over frequency bands relatively low quality henceforth relatively less (or no) parity bits per unit of time, and over frequency bands high quality henceforth relatively more parity bits transmitted per unit of time become.

Of the Sender informs the receiver - before beginning the actual data transmission and / or at predetermined or freely selectable times during the Data transfer - with, on which way (in which frequency bands, with or with how many parity bits, with which phase star, with or without "interleaving", etc.) in each case the bits or bit sequences over the transmitted respective frequency bands become.

These Notifications (as well as appropriate, addressed by the recipient to the sender Messages) are e.g. with the help of provided in the DSL standard transmit free bits (e.g., via in the ADSL overhead channel or in the embedded operation channel Bits).

1

Data communication system

2

telephone network

3

local exchange

4

Subscriber line

5

Subscriber Endanschlußeinrichtung

6a

first frequency band

6b

second frequency band

6c

third frequency band

6d

fourth frequency band

6e

fifth frequency band

7

phase star

8th

allocation table

9

cosine wave

10

cosine wave

11

cosine wave

12

microprocessor

13

microprocessor

14

memory device

15

memory device

16

Blackbox

17

Echo canceller

18

regulator

19

filter

20

delay

21

multipliers

22

adder

23

filter stage

24

filter stage

25

filter stage

26

frequency band

Claims (12)

Data communication system ( 1 ), which is a transmitting unit ( 3a ) at location A, from which via a transmission channel ( 4 ) modulated transmission signals ( 9 ) to a receiving unit ( 5a ) at location B, each bit or bit sequence to be transmitted (a) being a transmission signal ( 9 ) of particular amplitude (A1) and phase (φ1) is characterized in that the transmitting unit ( 3a ) a control device ( 12 . 14 ), which is designed and set up in such a way that, in conjunction with the test result obtained by the receiving unit and the configuration of the receiving unit, an adaptation of the transmitted signals and / or the characteristics of the transmitting unit to characteristics of the transmission channel and / or the receiving unit ( 5a ). Data communication system ( 1 ) according to claim 1, in which the control device ( 12 . 14 ) is configured and arranged to cause the adaptation before and / or during the transmission of payload data. Data communication system ( 1 ) according to one of the preceding claims, in which the control device ( 12 . 14 ) is designed and set up so that an adjustment in the transmitting unit ( 3a ) provided echo compensation device ( 17 ). Data communication system ( 1 ) according to claim 3, wherein the echo compensation device ( 17 ) a digital filter ( 19 ), and in which the control device ( 12 . 14 ) is designed and furnished so that an adjustment of the filter ordinal number (N) is caused by them. Data communication system ( 1 ) according to one of the preceding claims, in which the control device ( 12 . 14 ) is designed and set up so that through it an adaptation of the impedance of the (Zi (f)) of the transmitting unit ( 3a ). Data communication system ( 1 ) according to one of the preceding claims, in which the control device ( 12 . 14 ) is designed and set up so that a predistortion of the transmission signals ( 9 ). Data communication system ( 1 ) according to claim 6, in which the control device ( 12 . 14 ) is designed and set up so that it predistorts the phase and / or the amplitude of the transmission signals ( 9 ). Data communication system ( 1 ) according to one of the preceding claims, in which each transmission signal ( 9 ) using one of several frequency bands ( 6a . 6b ), and in which the control device ( 12 . 14 ) is set up and set up to determine at which data rate data over the different frequency bands ( 6a . 6b ) be transmitted. Data communication system ( 1 ) according to claim 8, in which the control device ( 12 . 14 ) is designed and arranged to specify that certain frequency bands are not used for data transmission. Transmitting unit ( 3a ) which is designed to be used in a data communication system ( 1 ) is usable according to one of claims 1 to 9. Receiving unit ( 5a ) which is designed to be used in a data communication system ( 1 ) is usable according to one of claims 1 to 9. Data transmission method within a data communication system according to the preamble of patent claim 1, characterized in that, in conjunction with a test result obtained by the receiving device and the configuration of the receiving unit, an adaptation of the transmitted signals and / or the characteristics of the transmitting unit to characteristics of the transmission channel and / or the receiving unit ( 5a ).