WO2007093522A1

WO2007093522A1 - Method, system and device for transferring information

Info

Publication number: WO2007093522A1
Application number: PCT/EP2007/051103
Authority: WO
Inventors: Josef FRÖHLER; Georg Hein; Thomas Treyer
Original assignee: Nokia Siemens Networks Gmbh & Co. Kg
Priority date: 2006-02-16
Filing date: 2007-02-06
Publication date: 2007-08-23
Also published as: DE102006007308A1

Abstract

The invention relates to a method, a system and a device for transferring information. According to the invention, a traffic load which produces information which is to be transferred is detected, an error correction method for transferring information is selected according to the detection results and the selected error correction method is used during the transfer of information. Said error correction method can be, for example, an interleaving method having a determined interleaving-time.

Description

description

Method, arrangement and device for transmitting information

The invention relates to a method, an arrangement and a device for transmitting information.

In current communication networks, users are increasingly demanding higher data transmission rates. Transmission methods which can also provide high transmission rates in the access networks of a communication network are, for example, methods which operate according to the xDSL method. With the aid of these transmission methods, the operators of communications networks can also offer their customers broadband connections, for example to the Internet, by means of which the subscribers can increasingly and quickly make use of numerous applications or applications. An example of such a data-intensive application, for which high transmission rates are required, is, for example, the transmission of video files via the Internet.

As with all data transmission methods, transmission errors can also occur in xDSL technology. One type of transmission error that occurs is errors in individual characters or bits. These single bit errors can usually be detected and corrected by additionally transmitted error correction information at the receiver. The error correction information contains, for example, hints added by the transmitter as to how the transmitted bit structure must look. On the basis of these instructions, the decoded bit string can be checked in the receiver for a received bit string or string and any erroneous individual bits contained therein corrected. Further types of transmission errors occurring in particular also in xDSL transmission methods are errors in which a whole series of successive bits is lost or transmitted incorrectly. Such errors with a high number of erroneous bits are also referred to as "burst bursts." In order to be able to remedy these types of errors that can not be corrected by conventional error correction methods as far as possible, The so-called "interleaving" procedure was introduced.

In the interleaving method (also referred to as "interleaving"), the data to be transmitted is not transmitted in the original order. Rather, the data to be transmitted is already "nested" in the transmitter prior to transmission.

An example of such interleaving and the principle of interleaving are explained below.

It is assumed that a data packet with a total of 24 bits (including the error correction information) should be transmitted. This data packet is now divided into, for example, 6 blocks of 4 bits each in the interleaving method. The membership of the 24 bits to the individual blocks is represented by the numbers 1 to 6:

Sent data package: "111122223333444455556666"

If this data packet was transmitted in a transmission system without interleaving, then when a burst error occurred (which in this example was corrupted by four consecutive bits), for example, the following data reached the receiver:

Received data packet: "11112222333 455556666" Such an error could not be corrected with conventional error correction methods.

In the interleaving method, the data block described above is now nested before transmission: in this example, first the first bits of a block are transmitted first, then the second bits of a block, etc.

Data block with interleaving: "123456123456123456123456"

If a burst error occurs during a transmission of this data packet (assuming the same error as in the above example without interleaving), the receiver receives the following data packet:

Data packet with burst error: "12345612345 456123456",

however, this is at first reconverted ("deinterleaving") in the receiver by means of the interleaving method, i. placed in the original bit sequence before interleaving by the transmitter. This results in the following data packet in the receiver:

Data packet after de-interleaving: "11_122_233_3444455556_66".

The burst error has now been split into single bit errors in the respective data blocks, which can be remedied with the conventional single bit error error correction techniques to be performed subsequently.

In addition to this advantage for improved error correction, however, the interleaving method also has a disadvantage. Since the data is not transmitted in the original order, more time is required for the complete transmission of a data packet. The data to be transmitted must be in

Stations are cached until there is a sufficient amount of data has accumulated, which are nested can. The time required for this is also known as "interleaving time". The same applies in the receiver: there de-interleaving can only be started when (almost) the entire data packet has been received. For example, in the above example, the first data block ("1111") can not be completely decoded until the last "1" has arrived (in this case the 19th bit).

This additional time required for interleaving increases the so-called "latency" in data transfers. Latency is generally referred to as the period of time which a data packet in a data transmission system requires from the sender to the recipient. It consists, for example, of the transit time in the transmission medium used and of the processing time in active components within the transmission path. In addition, the processing time required in the transmitter and in the receiver is also added to the latency.

This increase in the latency caused by the interleaving has a particularly disadvantageous effect on some time-critical applications. For example, in online computer games, it is desirable to be able to send the data to be transmitted between the subscribers or between the subscriber and the game server with as little delay as possible in order to achieve a more realistic presentation of the game events.

Overall, it can thus be stated that the manner of the interleaving method should depend on the type of service used by the respective subscriber. While better error correction is desirable in video or TV broadcasting over, for example, an xDSL port to avoid conspicuous errors in the transmitted image information, and greater latency can be tolerated by, for example, interleaving, applications such as online games conversely behave as follows: Here shorter latencies are important, but larger bit errors or data packet errors are less detrimental in comparison.

Therefore, current data networks usually have the option of switching off the interleaving method at the request of a subscriber for precisely this subscriber by the operator of the network ("FastPath"). However, a disadvantage of such a solution is inter alia that the interleaving method can only be switched off or switched on as a whole.

The object of the invention is to improve the transmission of information, in particular with regard to the selection and application of an error detection and / or error correction method.

This object is achieved on the basis of a method according to the features of patent claim 1 and of a device and an arrangement according to the features of patent claims 8 and 11.

In the context of the inventive method for transmitting information, transmission characteristics are detected, depending on the detection result, an error detection and / or error correction method for the transmission of the information is selected, and the selected error detection and / or error correction method is used in the transmission of the information.

The essential advantage of the method according to the invention is that a dynamic, service-dependent or application-dependent selection of an error detection and / or error correction method is made possible within the scope of an information transfer.

In the context of recording the transmission characteristics, an up-to-date traffic load caused by the information to be transmitted is advantageously recorded. For example, the traffic load recorded can be deduced from the type of application used.

Advantageously, interleaving methods are used as error detection and / or error correction methods, it being possible for each selectable interleaving method to interleave a different amount of information per interleaving step. Claims 3 and 4 can thereby contribute to error susceptibility and latency a procedure for the transmission of information.

Further advantageous embodiments of the method according to the invention as well as an arrangement and a device for carrying out the method according to the invention can be found in the subclaims.

In the following, the invention will be explained in more detail with the aid of the enclosed drawing (FIG. 1). This represents in the form of a block diagram an arrangement scenario for the connection of several subscribers to a communication network.

In FIG. 1, three subscribers (TN1, TN2, TN3) are connected by means of a respective subscriber line (DSL1, DSL2, DSL2) to a so-called DSLAM ("Digital Subscriber Line Access Multiplexer"), a multiplexer device. About the DSLAM a plurality of subscribers is connected to the parent main network of the communication network. While further switching nodes (aggregation network) are usually arranged in current communication networks between DSLAM and main network, the main network (in this case embodied as an IP network) is shown in FIG. 1 as being directly connected to the DSLAM for simplification. The data transmission between the subscribers (TN1, TN2, TN3) and the DSLAM is carried out, for example, according to the xDSL method.

Furthermore, in FIG. 1 detection means (EM) according to the invention are shown by which the traffic load on the individual subscriber lines (DSLl, DSL2, DSL3) can be determined. These detection means EM can also be implemented as part of the DSLAM and use its properties for measuring traffic loads. On the basis of these means of collection (EM), information about the traffic loads and the active services is passed on to the DSLAM and evaluated. In this, a configuration of the interleaving algorithm or the interleaving depth of interleaving is then dynamically carried out, for example, with the aid of the detected traffic loads.

A configuration of the interleaving algorithm does not mean that the interleaving method can only be switched off and on. Rather, the interleaving according to the invention can additionally be carried out in the most varied ways, i. For example, some parameters of the interleaving algorithm may be changed. For example, the size of the data packets interleaved in an interleaving step can be varied. The longer the data packets to be interleaved in one step, i. the larger the time interval ("interleaving time") that elapses between two interleaving operations, the greater the latency caused by the interleaving. Conversely, with shorter interleaving times, there are also shorter delays in transmitting the data.

In the context of the method according to the invention, the interleaving time can also be set to zero, for example.

As can be seen from the introduction, the error correction rate is greater at higher interleaving times (ie longer data packets to be interleaved) than at shorter interleaving times. As a result of shorter interleaving times, fewer transmission errors are compensated.

It is thus necessary to determine a balance that is individually suitable for each application, the lowest possible error rate and the lowest possible latency. Below are examples of some possible scenarios that show a relationship between current traffic load and corresponding interleaving settings. It is assumed by way of example that the decision algorithm, ie which settings are to be used for the parameters during interleaving, is given by a fixed threshold value (for example with regard to the traffic load). For example, the traffic load (in this case, for example, the current data rate) in the downstream direction (ie towards the subscriber) is recorded at regular intervals (eg every 100 ms). When a threshold value of, for example, 300 kbit / s has been exceeded, the interleaving time is increased from, for example, 4 ms to a value of, for example, 20 ms. If the threshold is undershot again, the interleaving time is reset to 4 ms.

In a first scenario, a participant watching a video stream through its DSL access is considered. In such a case, a consistently high data rate is used from the beginning of the stream to the end of it. Since this exceeds the threshold value of the data rate for video streams, a longer interleaving time is set in the DSLAM. There are fewer transmission errors and packet losses, so the video is of better quality.

If the subscriber (TN1, TN2, TN3) now participates in an online game, for example, the interleaving time changes according to the invention. Since on average a relatively low data rate is customary for online games, the measured data rate is usually below the predetermined threshold value. Thus, the shorter interleaving time is selected and set, the subscriber (TN1, TN2, TN3) receives a data connection with shorter latencies. Another example considers the behavior of the inventive method when surfing a subscriber (TNl, TN2, TN3) on the Internet.

Before the subscriber (TN1, TN2, TN3) opens his Internet browser, there is no load on his DSL line (DSL1, DSL2, DSL3). The interleaving time is therefore set to a short duration.

Subsequently, however, the browser requests data to display an Internet site (e.g., www.siemens.com), and loading such a site can be basically divided into four phases.

In the first phase, various so-called handshake dialogues are processed, such as looking up the IP address of the requested page ("DNS lookup"). Such configuration dialogs do not require a high bandwidth, the traffic load thus remains below the set threshold value. Also, the interleaving time is therefore set to a low value, resulting in a short latency in the data transfer. This in turn ensures a better and faster response through the Internet browser.

In the second phase, small files are downloaded by means of a few so-called TCP sessions (TCP: "Transmission Control Protocol"). For example, these files may be the HTML source code (HTML: "hypertext markup language") of the first page section. Since the TC protocol always starts a transmission with relatively small window sizes, the bandwidth for the download is low. In the second phase, therefore, the threshold for the data rate is not exceeded with a high probability, thus it remains at the short interleaving time.

During the third phase, the information downloaded in phase two is interpreted by the browser to to load objects embedded in the page, such as images or, for example, Java applications. Furthermore, with elaborately designed Internet pages with numerous links to other servers (eg for banner ads) DNS lookups are initiated again and started for these TCP sessions. In this phase too, the browser or the subscriber (TN1, TN2, TN3) profits from short latencies.

The download of the additional items described in Phase Three will then be completed in the fourth phase. Larger objects increase the emerging traffic load on the DSL line. The TC protocol attempts to maximize the bandwidth available on the DSL line. The threshold for the data rate is thus most likely exceeded in this example. According to the invention, therefore, the interleaving time is increased, for example by the DSLAM, which leads to a longer latency, but results in a lower error rate. A fact which is particularly advantageous in the case of the applied TCP: with a lower error rate, that is to say with less erroneous data packets, fewer data packets therefore also have to be sent repeatedly, as is prescribed for incorrect or non-received data packets according to TCP. Overall, a clear time advantage will thus be achieved with the aid of the method according to the invention. The information to be transmitted is transmitted more quickly.

After completing phase four of loading an Internet page, the traffic load on the DSL line drops again, the data rate threshold is undershot, and the interleaving time is again set to a lower value.

It should be noted that various algorithms for setting the parameters of the interleaving method can be used according to the invention. While in the above example If a fixed threshold value was used, a hysteresis method, ie different thresholds for exceeding and underrunning the data rate, can be used as well as an example. Also, instead of a threshold value, a mathematical function representing a dependency of interleaving time to bandwidth can be used.

According to the invention, both upstream, downstream and upstream and downstream rates can be monitored together. Also, the switching back of the interleaving time to a shorter (or higher) value can only be carried out after a certain period of time, that is to say after a certain time interval in which the traffic load is below (or above) a value. The change in the interleaving time could, for example, not be defined as a level but as a ramp.

Claims

claims

1. A method for transmitting information in which transmission characteristics are detected, an error detection and / or error correction method is selected for transmitting the information, and the selected error detection and / or error correction method is used in the transmission of the information, depending on the detection result.

2. The method according to claim 1, characterized in that in the context of the detection of Ubertragungseigenschaften a current, caused by the information to be transmitted traffic load is detected.

3. The method according to claim 1 or 2, characterized in that are used as error detection and / or error correction method interleaving method.

4. The method according to claim 3, characterized in that in each selectable interleaving method a different amount of information is interleaved per interleaving step.

5. The method according to any one of claims 2 to 4, characterized in that the selection of the error detection and / or error correction method is performed on the basis of a predetermined threshold value for the detected traffic load.

6. The method according to any one of claims 2 to 5, characterized in that the selection of the error detection and / or error correction method is performed by means of a hysteresis method posted the detected traffic load.

7. The method according to any one of claims 2 to 4, characterized in that the selection of the error detection and / or Fehlererkorrek- turverfahren based on a dependency between the traffic load and error detection and / or error correction method indicating function and / or table is performed.

8. Arrangement for the transmission of information, with detection means (EM) for detecting transmission characteristics, with selection means for selecting an error detection and / or error correction method for the transmission of the information depending on the detection result and with means for applying the selected error detection and / or or error correction procedure during the transmission of the information.

9. Arrangement according to claim 8, characterized in that the detection means (EM) are designed such that as Ubertragungseigenschaften a current, caused by the information to be transmitted traffic load is detected.

10. An arrangement according to claim 8 or 9, characterized in that the selection means are designed such that as an error detection and / or error correction method, an interleaving method is selected.

Apparatus for transmitting information, comprising detection means (EM) for detecting transmission characteristics, selection means for selecting an error detection and / or error correction method for transmitting the information dependent on the detection result, and means for applying the selected error detection and / or error correction method in the transmission of information.

12. The device according to claim 11, characterized in that the detection means (EM) are configured such that as Ubertragungseigenschaften a current, caused by the information to be transmitted traffic load is detected.