WO2007039393A2

WO2007039393A2 - Method for minimizing spectral interference during packet-switched data transmission

Info

Publication number: WO2007039393A2
Application number: PCT/EP2006/066111
Authority: WO
Inventors: Walter Klausberger; Werner Kozek
Original assignee: Nokia Siemens Networks Gmbh & Co. Kg
Priority date: 2005-09-30
Filing date: 2006-09-07
Publication date: 2007-04-12
Also published as: EP1935155A1; CN101300799A; DE102005046969A1

Description

description

Method for minimizing spectral interference in packet-oriented data transmission

The invention relates to a method for minimizing spectral interference in packet-oriented data transmission, the data being transmitted on transmission paths comprising a multiplicity of data channels.

In modern broadband access methods, such as e.g. Asymmetry Digital Subscriber Line ADSL, Wireless LAN, etc. are used for access to packet-oriented networks, e.g. the Internet, in which data is sent in the form of data packets, as in traditional remote data transmission, such as data transmission. Voice telephony via circuit-switched connections different physical transmission paths used. Such transmission paths are, for example, copper double wires of a conventional subscriber line system for so-called digital subscriber line (xDSL), coaxial cable

Television cable networks, fiber optic systems for wired data transmission or radio transmission methods, e.g. Wireless LAN, Universial Mobile Telecommunications System UMTS in the mobile radio area or satellite transmission technology for wireless data transmission.

Most of these transmission paths include a plurality of data channels, which are understood as established point-to-point connection and are suitable for the transmission of data over spatial or temporal distance. For transfer, these data are usually converted to electromagnetic signal patterns using suitable physical quantities such as e.g. Voltage, frequency or magnetic field strength, etc. are used to disseminate the information.

In addition to the interference generated by electronic components, connections, etc., the data transmission in one Data channel also influenced by the user data transmission in adjacent data channels of a Ubertragungsweges disturbing. Since payload data are usually forwarded in the form of electromagnetic signal patterns, so-called spectral interferences between data channels, which, for example, are logically and physically assigned to a network node-except in the case of fiber optic systems-can occur for the other media used for the transmission paths.

Under the spectral interference is usually the

Superposition of waves - in telecommunications, e.g. of electromagnetic waves as a function of a distribution of the frequencies or wavelengths in the signals understood. In the case of interference, a so-called constructive interference in which the superimposing waves mutually reinforce one another and a so-called destructive interference in which the superimposed waves mutually evaporate or even extinguish. Thus, interference from the spectral interference in the transmission of user data in the individual data channels such. Crosstalk - i. the coupling of an electromagnetic signal to an adjacent data channel during wireline transmission, bit errors - i. In the transmission of digital data, incorrect values are caused in individual memory cells, the so-called bits, of a data packet, etc.

In the modern broadband access methods such as ADSL or wireless LAN, etc. interference due to spectral interference especially with the use of some Internet applications such as so-called online games, a fast loading of large amounts of data, video streaming, etc., as it In these applications, there is a large fluctuation in the amount of data sent over the data channels. This often sudden appearance of heavy traffic on a data channel is also known as bursty traffic. Since the spectral interference between individual data channels represents a classic problem in telecommunications in the transmission of user data, measures are already known with which interference due to spectral interference during data transmission can be reduced.

For wired transmission with e.g. Copper double wires, for example, by so-called stranding or so-called shielding of the cable wires, the interference can be reduced by the spectral interference, the reduction of interference only between the individual transmission paths such. a cable core comes into effect.

In wireless transmission methods such as wireless LAN so-called directional antennas can be used, of which the electromagnetic energy is preferably emitted in certain directions. However, stray fields emitted in the other directions can still influence or disturb other data channels.

In addition to the physical measures for the reduction of spectral interferences, so-called multiple access methods can be used to reduce interference by spectral interference. In the case of wireless transmission, such methods are, for example, the methods used in mobile communications: frequency division multiple access FDMA or time division multiple access TDMA.

As an FDMA method, an access method to a

Data channel of a plurality of available data channels, wherein the data channels are generated by dividing the available bandwidth into individual frequency bands, which can be temporarily assigned to a transmitter. To spectral interference between the

To reduce frequency bands, small, unused protective bands - so-called guard bands - are inserted between the frequency bands. That has however to As a consequence, the overall bandwidth available for data transmission is reduced.

In the TDMA method, the data of different transmitters are transmitted in certain time sections - the so-called time slots - whereby each transmitter is provided with the full bandwidth of the transmission path for transmitting its data during the time slot assigned to it. Between the time slots are still the so-called Guard Times or guard times inserted, which are not for the

Data transmission to be used. In the TDMA method, a distinction can still be made between a synchronous and an asynchronous TDMA method. With the synchronous TDMA method, each transmitter is assigned a fixed time slot for data transmission, whereby the corresponding time slot remains unused if no data is sent by a transmitter. The capacity of the Ubertragungsweges is not optimally utilized. In the asynchronous TDMA method, the time slots of non-active stations are shared by the other stations. However, this method has the disadvantage that the data packets of active stations must be equipped with additional information for the receiver side, which on the one hand, the data packets to be transmitted itself and on the other hand, the cost of the correct assignment of the data packets on the receiver side are greater.

Another multiple access method used, for example, in the field of computer networks in the use of so-called Ethernet is the Carrier Sense Multiple Access / Collision Detection (CSMA / CD) method. In this method, the equal access is regulated to a common Ubertragungsweg several connected network nodes, being checked by a sendwilligen network node by so-called listening, whether the transmission path is free. Also during the transmission of data is overheard, so that a so-called collision - that is the equilateral transmission of signals of different network nodes and the superimposition of these signals - can be detected immediately. If a collision is registered by a sending network node, the data transmission is terminated by it and all other network nodes are informed about the collision by sending a special identifier. In this way, CSMA / CD responds to occurring collisions or superpositions of signals and prevents them from being repeated. A disadvantage of CSMA / CD, however, is that the number of network nodes connected to the Ubertragungsweg should be low or in many network nodes, the existing bandwidth is used only ineffective because of a larger number of collisions.

Another e.g. In the case of ADSL2, the measure used to reduce spectral interferences is the so-called power cutback. In this case, the spectral interference is reduced by regulating the transmission power in the data transmission as a function of the so-called signal-to-noise ratio SNR. The SNR indicates a ratio of a disturbance signal to a useful signal from which the data to be transmitted are contained. For power-cutback, however, during data transmission, the SNR of each data channel must be checked to then immediately adjust the data transmission rate and transmit power as the SNR on one of the channels being used gets worse. The

Verification of the SNR of each data channel, which must be carried out continuously during the data verification, is performed by a terminal on the subscriber side (e.g., an ADSL modem) along with a switch of the telecommunications network - a so-called digital one

Subscriber Line Access Multiplexer DSLAM - in the handshake method, ie by synchronization using an acknowledgment signal performed, making power-cutback is a relatively complex method for reducing spectral interference.

The present invention is therefore based on the object to provide a method by which said Disadvantages overcome and of which a simple and effective approach for reducing the spectral interference in wired and wireless transmission of packet-oriented data is offered.

The solution to this problem is inventively by a method of the type mentioned, by which the data channels used for the transmission of user data are evaluated, derived on the basis of this evaluation in the way signal patterns and sent over the unused data channels, so that a power density spectrum for the entire Transmission path is optimized.

The main aspect of the proposed solution according to the invention is that this solution can be easily applied to both wired and wireless data transmission with physically any structure of spectral interference. In addition, there are no restrictions with regard to the modulation methods used for data transmission. The optimal signal pattern used for the reduction of the spectral interference is determined with the aid of the power density spectrum for the entire transmission path, wherein the power density spectrum indicates the amplitude with which the individual frequencies are contained in a considered spectrum of the total electromagnetic signal transported over the transmission path. Of course, this total signal comprises both the useful signals which are important for the data transmission and the interference signals resulting from the spectral interference. The optimum power density spectrum for a transmission path is achieved when the proportion of interference signal amplitudes is as low as possible. From the optimal signal pattern, which is sent according to the inventive method on the unused data channels, therefore, a kind of filtering effect is generated. It is advantageous if the signal patterns for optimizing the power density spectrum in a test system are determined with the aid of semi-stochastic methods, since thus the active mode of a transmission path or system is not impaired by the complex determination of the optimum signal pattern. In the semi-stochastic method, signal patterns are first randomly generated, and then those signal patterns are registered for which an optimal power density spectrum is achieved. These signal patterns are then further refined, thereby finding, in a relatively rapid manner, optimal signal patterns for the reduction of spectral interference.

It is favorable if the signal patterns for optimizing the power density spectrum in a test facility are determined with the aid of analytical methods, since the use of a test facility enables the optimal signal patterns to be determined independently of the active operation and thereby impair the data transmission during the active operation of the transmission path or system is first evaluated in the analytical method, the power density spectrum of the entire transmission path and then derived from the optimal signal pattern. The signal pattern can therefore be adapted exactly to the requirements of the Ubertragungsweges.

The invention will be explained in more detail below by way of example with reference to the attached figure.

The figure shows the schematic sequence of the inventive method for reducing the spectral interference, wherein the determination of the optimal signal pattern in a test facility by means of a semi-stochastic method.

After a first start step 1, in a second step 2, the conditions present in a data transmission on a transmission path with a multiplicity of data channels are transferred to a test system in which the Operation of the actual transmission path to be readjusted, transmitted and thus simulated the transmission of user data in the data channels over this transmission path in the test facility. In a third step 3, the transmission of user data in the data channels of

Transmission path evaluated and performed a first measurement of the power density spectrum of the entire Ubertragungsweges in this data transmission using a power meter present in the test facility.

In a fourth step 4, a signal pattern is generated in the test facility by the existing Digital Signal Processor by a random generator. In a fifth step 5, this signal pattern is sent via the transmission path in addition to the user data in the data channels that are unused in the user data transmission. In a sixth step 6, the effective effect of the signal pattern is evaluated by a further measurement of the power density spectrum of the entire transmission path.

In a seventh step 7, it is checked whether the power density spectrum has improved compared with the first measurement of the power density spectrum in the third step 3. This means that it is analyzed whether the amplitudes of the frequencies of the disturbing signals have been reduced by the use of the signal pattern.

If no improvement has been achieved, steps 4 to 6 of the method according to the invention are repeated until an improvement in the direction of the optimum power density spectrum can be ascertained in the seventh step 7.

If an improvement of the power density spectrum is detected by the use of a signal pattern in the seventh step 7, this signal pattern is registered in an eighth step 8. The signal pattern can then be further improved in a ninth step 9 in order to continue the power density spectrum of the entire transmission path to optimize. This means that the registered signal pattern is adapted by analysis to the power density spectrum determined in the first measurement in order to further improve the signal-to-noise ratio SNR. In a tenth step 10, the signal pattern determined in the test installation is then stored on the active system and can now be used to reduce the spectral interference on the transmission path in active operation.

Most are used for effective reduction of the spectral

Interference not only single but multiple signal patterns used, which can be determined by the use of a test facility in a simple manner. By using the test equipment, it is also possible to filter out from a relatively large number of signal patterns those which optimize the power density spectrum of a transmission path and thus reduce the spectral interference.

Claims

claims

1. A method for minimizing spectral interference in packet-oriented data transmission over a Ubertragungsweg with a plurality of data channels, characterized in that the data channels used for the transmission of user data are evaluated, that derived therefrom in the way signal patterns and sent over the unused data channels, so that a power density spectrum is optimized for the entire transmission path.

2. Method according to claim 1, characterized in that the signal patterns for optimizing the power density spectrum are determined in a test facility with the aid of semi-stochastic methods.

3. The method according to claim 1, characterized in that the signal pattern for optimizing the power density spectrum are determined in a test facility using analytical methods.