CN101534273A - Method, device and system for optimizing transmission speed in DSL system - Google Patents

Abstract

The embodiment of the invention discloses a method, device and system for optimizing the transmission rate in the digital subscriber line (DSL) system. The method includes the following steps: according to the actual attenuation average value of the transmitting frequency point in the handshake phase, selecting the theoretical attenuation average value with the smallest difference with the actual attenuation average value, and using the line length corresponding to the theoretical attenuation average value as The current line length; according to the line length, select the corresponding CE length from the relationship table between cyclically extended CE length and line length. In the embodiment of the present invention, in the absence of time domain equalization, the current line length is estimated according to the actual attenuation average value and the theoretical attenuation average value of the transmitting frequency point in the handshake phase, and the relationship between the preset CE length and line length is obtained from the estimated line length The corresponding CE length is selected in the table, so as to ensure the maximum rate of the system when the system symbol interference is eliminated.

Description

A method, device and system for optimizing transmission rate in DSL system

technical field

The invention relates to the field of network technology, in particular to a method, device and system for optimizing transmission rate in a DSL system.

Background technique

DSL (Digital Subscriber Line, Digital Subscriber Line) technology is a high-speed transmission technology for data transmission through telephone twisted pair, namely UTP (Unshielded Twist Pair, unshielded twisted pair), including ADSL (Asymmetrical Digital Subscriber Line, non Symmetrical Digital Subscriber Line), VDSL (Very-high-bit-rate Digital Subscriber Line, very high-speed digital subscriber line), etc.

The DSL system widely applies DMT (Discrete MultiTone modulation, discrete multi-carrier modulation) technology. Multi-carrier transmission utilizes a large number of orthogonal frequency-divided subcarriers, and each carrier loads a certain fixed bit information and corresponding modulation methods such as 4-QAM (4-Quadrature Amplitude Modulation, 4-Orthogonal Amplitude Modulation), 16-QAM etc., the bit loading of all subcarriers determines the transmission rate of this DMT system. In the DSL system, because the time-domain signal undergoes some linear and nonlinear transformations when passing through the channel, the transmitted signal energy spreads, and these spreads may lead to ISI (Inter Symbol Interference, symbol interference) between adjacent symbols. As a result, the performance of the DMT system is degraded.

In order to solve the problem of symbol interference, in the DMT system, the last CP (Cyclic prefix, cyclic prefix) sampling points of each symbol after the inverse fast Fourier transform are added to each symbol as a cyclic prefix, and removed at the receiving end. These CP sampling points are used to resist the influence of ISI. That is, when the CP length is greater than the channel impulse response length, the signal diffusion energy of the symbol will only leak within the CP length, and removing the CP sampling points at the receiving end eliminates the influence of ISI between adjacent symbols. However, for the entire system, the CP carries useless information. When the length of the CP is very long, although more channel energy diffusion can be tolerated, the transmission rate of the DMT system will decrease at this time, thereby degrading the system performance.

Therefore, the prior art cannot guarantee the maximum transmission rate of the system when eliminating the symbol interference of the DSL system.

Contents of the invention

Embodiments of the present invention provide a method, device and system for optimizing a transmission rate in a DSL system, so as to ensure the maximum transmission rate of the system when eliminating symbol interference in the DSL system.

In order to achieve the above object, an embodiment of the present invention provides a method for optimizing the transmission rate in a DSL system on the one hand, including the following steps: according to the actual attenuation average value of the transmitting frequency point in the handshake phase, select the difference between the actual attenuation average value and the actual attenuation average value The theoretical attenuation average value with the smallest value, and the line length corresponding to the theoretical attenuation average value as the current line length; select the corresponding line length from the CE (Cyclic Extension, cyclic extension) length and line length relationship table according to the line length The CE length.

On the other hand, the embodiment of the present invention also provides a device for optimizing the transmission rate in the DSL system, including: a calculation module, which is used to select the actual attenuation average value according to the actual attenuation average value of the transmitting frequency point in the handshake phase. The theoretical attenuation average value with the smallest difference, and the line length corresponding to the theoretical attenuation average value as the current line length; the selection module is used to select the corresponding line length from the cyclic prefix length and line length relationship table according to the line length The length of the cyclic prefix; the storage module is used to store the CE length and the line length relationship table.

In another aspect, the embodiment of the present invention also provides a digital subscriber line DSL system with optimized transmission rate, including: a data receiving device, a rate optimizing device and a data sending device, the data receiving device is used for receiving data. The rate optimization device is used to optimize the transmission rate of the DSL system. The data sending device is configured to send the data received by the data receiving device according to the transmission rate optimized by the rate optimizing device.

Compared with the prior art, the embodiment of the present invention has the following advantages: the embodiment of the present invention pre-sets the CE length and line length relationship table, and then estimates the current line length according to the actual attenuation average value and the theoretical attenuation average value, and according to the The line length selects the corresponding CE length from the pre-set CE length and line length relationship table to realize the maximization of the transmission rate of the DSL system while eliminating the symbol interference of the DSL system.

Description of drawings

Fig. 1 is the method flowchart of setting CE length and line length relationship table in the embodiment of the present invention;

Fig. 2 is the impulse response simulation figure of the channel in the line length of 500m in the embodiment of the present invention;

Fig. 3 is the method flow chart of the embodiment of the present invention;

4 is a structural diagram of a rate optimization device according to an embodiment of the present invention;

FIG. 5 is a structural diagram of a DSL system with transmission rate optimization according to an embodiment of the present invention.

Detailed ways

The specific embodiment of the present invention is described in detail below in conjunction with accompanying drawing and embodiment:

In the embodiment of the present invention, in the absence of time domain equalization, the current line length is estimated according to the actual attenuation average value and the theoretical attenuation average value, and the corresponding line length is selected from the preset CE length and line length relationship table according to the line length. The CE length is used to maximize the transmission rate of the DSL system while eliminating the symbol interference of the DSL system.

Among them, the process of setting the relationship table between CE length and line length is shown in Figure 1, which specifically includes the following steps:

Step S101, calculating the channel impulse response length under a certain line length according to the line transfer function. For example, the channel impulse response length is calculated by simulation when the line length is 500 m. As shown in Figure 2, it is a simulation diagram of the channel impulse response when the line length is 500m.

Step S102, select the CP length under the line length according to the channel impulse response. For example, after obtaining the channel impulse response length when the line length is 500m, select the CP length. Generally, it is required that CP>=D+1; among them, D is the line length. Then the initial value of the CP length can be set as CP=D+1.

Step S103, calculate the CE length under the line length according to the CP length. According to the formula: CE=CP+CS-BETA, wherein, CS is the length of the cyclic suffix, and BETA is the length of the window. In practice, the CS length has little influence on the CE length and can be set to 0, while the windowed length BETA is generally known, so the corresponding CE length can be calculated according to the CP length.

Step S104, calculating the transmission rate under the line length according to the CE length. First, according to the DMT symbol rate formula: $f_{\mathrm{the\; s}}=\frac{2N*4312.5}{2N+\mathrm{CE}},$ Calculate the symbol rate, where 2N is the sampling point. Then, according to the system transmission rate formula: DataRate=∑bi×f _s , the data rate of the system is calculated. where Σbi is the sum of the bit loads of a DMT symbol.

Step S105, according to the transmission rate, select the CE length corresponding to the transmission rate that meets the preset rate requirement. The transmission rate meeting the preset rate requirement refers to maximizing the transmission rate of the system while ensuring the performance of the system under the corresponding preset line length. If the transmission rate meets the transmission rate of the preset rate requirement, then use the CE length as the CE length under the corresponding line length, otherwise reselect CP (such as setting CP=D+2), and repeat steps S103～S105, Until the CE length corresponding to the maximum transmission rate that meets the preset rate requirement under the line length is selected. In this way, the CE length corresponding to different line lengths can be calculated, and a relationship table between the CE length and the line length can be made, as shown in Table 1.

Table 1

Line length (m) 100 200 300 400 500 600 700 800 900 1000 1100 CE length (m) 3 4 4 5 5 5 5 6 6 6 7 Line length (m) 1200 1300 1500 1800 2000 2300 2500 3000 CE length (m) 6 7 7 8 9 10 10 12

As shown in Figure 3, it is a flow chart of the method of the embodiment of the present invention, which specifically includes the following steps:

Step S301, estimating the current line length according to the actual attenuation average value and the theoretical attenuation average value of the transmitting frequency point in the handshake phase. The actual attenuation average value of the uplink/downlink transmission frequency points of the carrier with the current line length in the handshake phase is obtained through actual measurement and calculation. Because the uplink/downlink transmission frequency point of the carrier in the handshake phase of the current line length is known (as shown in Table 2, the DSL system will select a carrier in the handshake phase, if the carrier is selected, the corresponding uplink/downlink transmission frequency of the carrier point is selected), the theoretical attenuation average value of each uplink and downlink frequency points under different line lengths can be pre-calculated according to the line transfer function. Approximate the actual attenuation average value and the theoretical attenuation average value according to the minimum error method, determine the theoretical attenuation average value with the smallest difference between the actual attenuation average value, and calculate the difference between the actual attenuation average value and the actual attenuation average value The preset line length corresponding to the minimum theoretical attenuation average value is used as the current line length.

Table 2

Step S302: Select the corresponding CE length from the CE length-to-line length relationship table according to the current line length. As shown in Table 1, after the CE length is selected, the transmission rate of the system corresponding to the CE length is maximized.

As shown in Figure 4, it is a device structure diagram of the embodiment of the present invention, including: a calculation module 1, which is used to select the theory with the smallest difference from the actual attenuation average value according to the actual attenuation average value of the transmitting frequency point in the handshake phase The attenuation average value, and the line length corresponding to the theoretical attenuation average value is used as the current line length. The selection module 2 is configured to select the corresponding cyclic prefix length from the relationship table between cyclic prefix length and line length according to the line length. The storage module 3 is used for storing the relationship table between the CE length and the line length.

Wherein, the calculation module 1 further includes: 11 a first acquisition sub-module, configured to acquire the actual attenuation average value of the uplink/downlink transmission frequency points in the handshake phase through measurement and calculation. The second acquisition sub-module 12 is configured to acquire the uplink/downlink transmission frequency points of the handshake phase under the preset different line lengths according to the handshake phase uplink/downlink transmission frequency points and preset different line lengths Theoretical decay average. The comparison sub-module 13 is configured to compare the actual attenuation average value with the theoretical attenuation average value to obtain the theoretical attenuation average value with the smallest difference between the actual attenuation average value and the actual attenuation average value. The confirmation sub-module 14 uses the preset line length corresponding to the theoretical average attenuation with the smallest difference between the actual attenuation average as the current line length.

As shown in FIG. 5 , it is a structural diagram of a DSL system optimized for transmission rate according to an embodiment of the present invention, including: a data receiving device 51 , a rate optimizing device 52 and a data sending device 53 , wherein the data receiving device 51 is used to receive data. The rate optimization device 52 is used to optimize the transmission rate of the DSL system. The data sending device 53 is configured to send the data received by the data receiving device 51 according to the transmission rate optimized by the rate optimizing device 52 .

In the embodiment of the present invention, in the absence of time domain equalization, the current line length is estimated according to the actual attenuation average value and the theoretical attenuation average value, and the corresponding CE is selected from the preset CE length and line length relationship table according to the line length length, so as to ensure the maximum rate of the system when eliminating system symbol interference.

Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be realized by hardware, and of course it can also be realized by means of software plus a necessary general-purpose hardware platform, but the former is better in many cases implementation. Based on this understanding, the essence of the technical solution of the present invention or the part that contributes to the prior art can be embodied in the form of hardware products.

The above disclosures are only a few specific embodiments of the present invention, however, the present invention is not limited thereto, and any changes conceivable by those skilled in the art shall fall within the protection scope of the present invention.

Claims (10)

1, a kind of method for optimizing transmission rate in digital subscriber line DSL system, it is characterized in that, comprising the following steps: According to the actual attenuation average value of the transmitting frequency point in the handshake phase, select the theoretical attenuation average value with the smallest difference from the actual attenuation average value, and use the line length corresponding to the theoretical attenuation average value as the current line length; Select the corresponding CE length from the relationship table between cyclically extended CE length and line length according to the line length. 2. The method for optimizing the transmission rate in a DSL system as claimed in claim 1, characterized in that, according to the actual attenuation average value of the transmitting frequency point in the handshake phase, the theoretical value with the smallest difference between the actual attenuation average value and the actual attenuation average value is selected. Attenuation average value, and the line length corresponding to the theoretical attenuation average value as the current line length, specifically including: Obtain the actual attenuation average value of the uplink/downlink transmission frequency points in the handshake phase through measurement and calculation; According to the uplink/downlink transmission frequency point and the preset different line lengths in the handshake phase, obtain the theoretical attenuation average value of the uplink/downlink transmission frequency point in the handshake phase under the preset different line lengths; Comparing the actual attenuation average value with the theoretical attenuation average value to obtain the theoretical attenuation average value with the smallest difference from the actual attenuation average value; The line length corresponding to the theoretical average attenuation with the smallest difference between the said average attenuation and the actual attenuation average is taken as the current line length. 3. The method for optimizing the transmission rate in the DSL system according to claim 1, characterized in that it comprises: The CE length and line length relationship table is preset. 4. The method for optimizing the transmission rate in a DSL system according to claim 3, wherein said preset relationship table between CE length and line length specifically includes: Calculate the channel impulse response length under different preset line lengths according to the line transfer function; Selecting a CP length under a corresponding preset line length according to the channel impulse response; According to the CP length, the CE length meeting the preset rate requirement under the corresponding preset line length is calculated. 5. The method for optimizing the transmission rate in a DSL system according to claim 4, wherein said calculating the CE length according to the corresponding preset line length according to the CP length and meeting the preset rate requirement specifically includes: calculating the CE length under the corresponding preset line length according to the CP length; calculating a transmission rate under a corresponding preset line length according to the CE length; According to the transmission rate, the CE length corresponding to the preset line length meeting the preset rate requirement is selected. 6. The method for optimizing the transmission rate in a DSL system according to claim 4 or 5, wherein the corresponding preset line length meets the preset rate requirements, specifically: The transmission rate of the system is maximized while ensuring the performance of the system under the corresponding preset line length. 7. A device for optimizing transmission rate in a DSL system, characterized in that it comprises: The calculation module is used to select the theoretical average attenuation with the smallest difference from the actual attenuation average according to the actual attenuation average of the transmitting frequency points in the handshake phase, and use the line length corresponding to the theoretical attenuation average as the current the line length; A selection module, configured to select a corresponding cyclic prefix length from the relationship table between cyclic prefix length and line length according to the line length; The storage module is used to store the relationship table between the cyclically extended CE length and the line length. 8. The device for optimizing the transmission rate in the DSL system according to claim 6, wherein the calculation module comprises: The first obtaining submodule is used to obtain the actual attenuation average value of the uplink/downlink transmission frequency points in the handshake phase through measurement and calculation; The second acquisition sub-module is used to obtain the theory of the uplink/downlink transmission frequency points in the handshake phase under the preset different line lengths according to the handshake phase uplink/downlink transmission frequency points and preset different line lengths decay average; A comparison submodule, configured to compare the actual attenuation average with the theoretical attenuation average to obtain the theoretical attenuation average with the smallest difference from the actual attenuation average; The confirmation sub-module takes the preset line length corresponding to the theoretical average attenuation with the smallest difference between the actual attenuation average as the current line length. 9. A digital subscriber line DSL system with optimized transmission rate, characterized in that it comprises: a data receiving device, a rate optimizing device and a data sending device, The data receiving device is used to receive data; The rate optimization device is used to optimize the transmission rate of the DSL system; The data sending device is configured to send the data received by the data receiving device according to the transmission rate optimized by the rate optimizing device. 10. The DSL system with transmission rate optimization according to claim 9, wherein said rate optimization device comprises: The calculation module is used to select the theoretical average attenuation with the smallest difference from the actual attenuation average according to the actual attenuation average of the transmitting frequency points in the handshake phase, and use the line length corresponding to the theoretical attenuation average as the current the line length; A selection module, configured to select a corresponding cyclic prefix length from the relationship table between cyclic prefix length and line length according to the line length; The storage module is used to store the relationship table between the cyclically extended CE length and the line length.

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