CN111953624A

CN111953624A - Echo time delay estimation method and device

Info

Publication number: CN111953624A
Application number: CN201910412911.8A
Authority: CN
Inventors: 李长兴; 李小勇
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2019-05-17
Filing date: 2019-05-17
Publication date: 2020-11-17
Also published as: WO2020233348A1

Abstract

An echo delay estimation method, comprising: acquiring an echo distortion signal; sampling the echo distortion signal, and processing a sampling result by using a known sequence to obtain a processing result; based on the processing results, the echo delay is estimated by peak search. The echo time delay estimation method and device support echo compensation by estimating the echo time delay so as to improve signal transmission performance.

Description

Echo time delay estimation method and device

Technical Field

The present disclosure relates to but not limited to the field of digital signal processing technologies, and in particular, to an echo delay estimation method and apparatus.

Background

One of the main application scenarios of digital microwave communication is wireless backhaul, and with the development of the fourth generation mobile communication technology (4G) and the fifth generation mobile communication technology (5G), the backhaul throughput is required to be higher and higher. At present, in digital microwave communication, there are two main directions for improving throughput: firstly, the Modulation mode is higher and higher, from the former maximum to 256QAM (Quadrature Amplitude Modulation), to the latter 1024QAM, and 4096QAM and 8192QAM which are now reached by the industry's efforts; secondly, the transmission bandwidth is getting larger, and the industry has achieved 112M (megahertz) on the split-type device at present, and is striving towards 224M.

In digital microwave communication, there are many distortions, such as time offset, phase offset, frequency offset, phase noise, power amplifier nonlinear distortion, echo distortion, etc., and meanwhile, scenes such as dual polarization, MIMO (Multiple In Multiple Out, Multiple input Multiple output), etc. are also considered; the existence of the distortion causes a poor system SNR (Signal Noise Ratio), and meanwhile, the digital microwave communication system is required to support an extremely high modulation mode, so that the transmission performance under a high-order modulation mode cannot be guaranteed.

Disclosure of Invention

The application provides an echo time delay estimation method and device, which can estimate echo time delay, thereby supporting echo compensation and improving signal transmission performance.

In one aspect, the present application provides an echo delay estimation method, including: acquiring an echo distortion signal; sampling the echo distortion signal, and processing a sampling result by using a known sequence to obtain a processing result; based on the processing result, the echo time delay is estimated through peak value search.

In another aspect, the present application provides an echo delay estimation device, including: the signal acquisition module is suitable for acquiring an echo distortion signal; the sampling processing module is suitable for sampling the echo distortion signal and processing a sampling result by using a known sequence to obtain a processing result; and the time delay estimation module is suitable for estimating the echo time delay through peak value search based on the processing result.

In another aspect, the present application provides an indoor unit of a digital microwave communication device, including: a signal receiving module, a memory and a processor, the signal receiving module being adapted to obtain an echo distorted signal, the memory being adapted to store a computer program, which when executed by the processor implements the steps of the above-described echo delay estimation method.

In another aspect, the present application further provides a computer-readable storage medium, which stores a computer program, and the computer program, when executed by a processor, implements the steps of the echo delay estimation method.

In the method, an echo distortion signal is acquired, the acquired echo distortion signal is sampled, a sampling result is processed by using a known sequence, and echo time delay is estimated through peak value search based on the processing result. The method and the device can realize the estimation of the echo time delay so as to support the echo compensation, thereby improving the signal transmission performance.

Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the claimed subject matter and are incorporated in and constitute a part of this specification, illustrate embodiments of the subject matter and together with the description serve to explain the principles of the subject matter and not to limit the subject matter.

Fig. 1 is a schematic diagram of echo generation of a split digital microwave communication device;

fig. 2 is a flowchart of an echo delay estimation method according to an embodiment of the present application;

fig. 3 is a diagram illustrating an application example of an echo delay estimation method according to an embodiment of the present application;

FIG. 4 is a schematic diagram of an error signal acquisition in an embodiment of the present application;

FIG. 5 is a schematic diagram illustrating a correlation calculation performed on an error signal in two paths according to an embodiment of the present application;

FIG. 6 is a schematic diagram illustrating a peak location screening process in an embodiment of the present application;

fig. 7 is a diagram of another application example of the echo delay estimation method according to the embodiment of the present application;

fig. 8 is a diagram of another application example of the echo delay estimation method according to the embodiment of the present application;

fig. 9 is a schematic diagram of an echo delay estimation device according to an embodiment of the present application;

fig. 10 is a schematic diagram of an indoor unit of a digital microwave communication device according to an embodiment of the present application.

Detailed Description

Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.

The steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions. Also, while a logical order is shown in the flow diagrams, in some cases, the steps shown or described may be performed in an order different than here.

As shown in fig. 1, a commonly used architecture of a digital microwave communication device is a split architecture, that is, the whole device is divided into two parts: an indoor Unit (IDU) and an outdoor Unit (ODU) connected by an intermediate frequency cable. The length of the intermediate frequency cable between the IDU and the ODU is uncertain, and changes with the change of application scenarios, and the currently applied intermediate frequency cable length is between 0 and 300 meters. Wherein, for microwave communication, the intermediate frequency may refer to a frequency range of 300KHz to 1000 MHz. However, the IDU and ODU are not limited to intermediate frequency cable connections.

At the joint of the intermediate frequency cable, reflections occur at the joint due to the imperfect mating of the connectors. As shown in fig. 1, at a transmitting end, a signal sent by an IDU to an ODU is reflected at an inlet of the ODU, and then a reflected signal reaches an IDU joint to generate a first reflection, the two reflections form a first ECHO (ECHO 1), and the ECHO 1 is sent to the ODU together with a main signal. Similarly, at the receiving end, the signal sent by the ODU to the IDU undergoes a first reflection at the inlet of the IDU, and then the reflected signal undergoes a second reflection at the ODU junction, and these two reflections form a second ECHO (ECHO 2), and ECHO 2 is sent to the IDU together with the main signal. The two echoes have great influence on the application scene of the modulation mode above 512 QAM. Because the requirement of echo cancellation is not considered in the original digital microwave communication system, the highest modulation mode which can be stably operated in an external field can only reach 256QAM at many times, and the transmission performance under a high-order modulation mode cannot be ensured.

Since the energy of the signal is attenuated by about 15 to 20dB per reflection at the if cable junction, each echo between the IDU and ODU is attenuated twice in the split architecture. For the signal transmission from the transmitting end to the receiving end shown in fig. 1, although there is an ECHO after four reflections, the energy is already small, and the influence on the transmission performance is negligible, so that, at the transmitting end or the receiving end, only the ECHO generated by two reflections needs to be considered between the IDU and the ODU, that is, only the influence of ECHO 1 and ECHO 2 on the transmission performance needs to be considered from the transmitting end to the receiving end. And, the signal is attenuated through the if cable, which has a loss of about 3 to 7dB/100m, 2 to 3dB/(20 to 50) m. Generally, the longer the intermediate frequency cable, the greater the attenuation. When the length of the intermediate frequency cable between the IDU and ODU is greater than 100m, the two reflections plus the attenuation of the intermediate frequency cable are substantially above 45dB, so the effect of the echo on the main signal is also negligible. In summary, in the digital microwave communication device under the split architecture, only the echo effect of the intermediate frequency cable length between the IDU and the ODU between 0 and 100m may need to be considered.

The embodiment of the application provides an echo time delay estimation method and device, which can estimate echo time delay, thereby supporting echo compensation and improving signal transmission performance. The echo time delay estimation method provided by the embodiment of the application can be applied to the digital microwave communication equipment with the split type architecture shown in fig. 1, and can meet the performance requirements of echo cancellation in a high-order modulation mode under various application scenes in digital microwave communication.

Fig. 2 is a flowchart of an echo delay estimation method according to an embodiment of the present application. The ECHO delay estimation method provided by this embodiment may be applied to the scenario shown in fig. 1, and is used to estimate the delays of ECHO 1 and ECHO 2 in the IDU of the digital microwave communication device serving as the receiving end, so as to perform ECHO compensation. In fig. 1, in an application scenario of the most common intermediate frequency cable length (15m to 100m) in the external field, after echo compensation is performed, the performance of digital microwave transmission can be improved by about 8dB to the maximum extent, and the requirements of 4096QAM and 8192QAM in the current long intermediate frequency cable can be met.

As shown in fig. 2, the echo delay estimation method provided in this embodiment includes the following steps:

s201, obtaining an echo distortion signal;

s202, sampling the echo distortion signal, and processing a sampling result by using a known sequence to obtain a processing result;

and S203, estimating the echo time delay through peak value search based on the processing result.

In this embodiment, the echo distortion signal obtained in S201 is a signal with echo distortion energy as a dominant component in distortion energy; in other words, in the echo distortion signal acquired in S201, the echo distortion energy is dominant in addition to the main signal energy.

In an exemplary embodiment, S201 may include: eliminating distortion except echo distortion in the received signal; when the SNR stabilizes to a set range (e.g., greater than 35dB) within a set duration after the distortion other than the echo distortion is removed, an echo distortion signal is obtained. For various distortions in the received signal, various distortions except echo distortion can be eliminated by using a corresponding algorithm, and a hard decision is performed after the signal is equalized and converged to obtain an echo distortion signal. The set time length can be determined according to the actual application scene.

In this exemplary embodiment, the echo delay estimation method of this embodiment may further include: and when the distortion except the echo distortion is eliminated and the SNR can not reach the set range within the set time length, exiting the echo time delay estimation. For example, after the distortion except the echo distortion is removed, the SNR is less than 35dB in the set duration, and the echo delay estimation and compensation process may not be performed.

In an exemplary embodiment, the processing the sampling result using the known sequence in S202 may include: and carrying out correlation operation on the sampling result and the known sequence. The correlation operation commonly used in the field of mathematics includes autocorrelation operation and cross-correlation operation, the autocorrelation operation can be used for describing the correlation degree between the values of the same time sequence at any two different moments, and the cross-correlation operation can be used for describing the correlation degree between the values of the two time sequences at any two different moments. In this embodiment, the autocorrelation degrees of the sampling results at different times can be embodied by respectively calculating the correlation degrees between the signals at different times in the sampling results and the same known sequence. The processing result may include a set of correlation values and a corresponding position (e.g., offset frame header position information) of each correlation value. Wherein the larger the correlation value, the higher the degree of correlation.

In an exemplary embodiment, S202 may include: carrying out N times of up-sampling on the echo distortion signal, dividing the up-sampled signal into M paths, and respectively processing the M paths of signals by utilizing a known sequence of the up-sampling N times; n, M are positive integers, and N is greater than or equal to M. Wherein, the M paths of signals can be respectively correlated with the known sequences sampled by N times. For example, N and M may be 2; the 2 times up-sampled signal can be divided into odd and even paths, and then correlation calculation is performed with the up-sampled 2 times known sequence. Wherein, a preamble with a certain symbol length can be selected as the known sequence.

In an exemplary embodiment, S203 may include: determining a maximum peak position and a next largest peak position based on the processing result; and estimating two echo time delays based on the maximum peak position, the second maximum peak position and the signal frame head position. The maximum peak position may include a position of a frame header offset corresponding to the maximum peak, and the second largest peak position may include a position of a frame header offset corresponding to the second largest peak.

In the present exemplary embodiment, determining the maximum peak position and the next largest peak position based on the processing result may include: aiming at the processing result of any physical frame of the echo distortion signal, finding a maximum peak value and a secondary peak value in a peak searching area, and obtaining the appearance position of the maximum peak value and the appearance position of the secondary peak value; determining maximum peak positions and next-largest peak positions respectively based on the appearance positions of the L maximum peaks and the appearance positions of the L next-largest peaks obtained from the processing results of the L physical frames; wherein L is an integer greater than or equal to 1. When L is 1, the position of the maximum peak is the appearance position of the found maximum peak, and the position of the next largest peak is the appearance position of the found next largest peak; when L is larger than 1, the position of the maximum peak is determined according to the appearance positions of the found multiple maximum peaks, and the position of the secondary peak is determined according to the appearance positions of the found multiple secondary peaks.

In the present exemplary embodiment, determining the maximum peak position and the next largest peak position based on the appearance positions of the L maximum peaks and the appearance positions of the L next largest peaks obtained from the processing results of the L physical frames, respectively, includes:

for the appearance positions of the L maximum peaks or the appearance positions of the L next largest peaks, the following processing is performed, respectively: determining one or more appearance positions meeting set conditions as a position group, and counting the peak value appearance times of the position group; respectively comparing the peak occurrence frequency of each position group with a set threshold value, and screening out the position groups of which the peak occurrence frequency is greater than or equal to the set threshold value; calculating an average position of the screened position groups;

or, for the appearance positions of the L maximum peaks or the appearance positions of the L next largest peaks, respectively, the following processing is performed: determining one or more appearance positions meeting set conditions as a position group, and counting the peak value appearance times of the position group; and selecting a position group with the maximum peak occurrence frequency, and calculating the average position of the selected position group.

The final average position calculated for the appearance positions of the L maximum peaks is the maximum peak position, and the final average position calculated for the appearance positions of the L next maximum peaks is the next maximum peak position.

In the exemplary embodiment, after determining the maximum peak position and the second largest peak position, one echo delay may be calculated according to an interval between the maximum peak position and a frame header position of the signal frame, and another echo delay may be calculated according to an interval between the second largest peak position and the frame header position of the signal frame. The embodiment of the application can estimate two echo time delays at the same time.

In an exemplary embodiment, before S201, the echo delay estimation method provided in this embodiment may further include: and when the modulation order of the configured modulation mode is larger than the modulation order of the set modulation mode, switching from the configured modulation mode to the set modulation mode. The setting of the modulation mode may refer to a modulation mode that can ensure that a hard decision is error-free in the presence of an echo. In the digital microwave communication system shown in fig. 1, after the transmitting end and the receiving end are powered on, when the modulation order of the configured modulation scheme is higher than the modulation order of the set modulation scheme, the configured modulation scheme may be switched to the set modulation scheme with a lower modulation order; when the modulation order of the configured modulation scheme is not higher than the modulation order of the set modulation scheme, the configured modulation scheme can be maintained unchanged.

In this exemplary embodiment, after S203, the echo delay estimation method provided in this embodiment may further include: and after the echo time delay compensation is completed according to the estimated echo time delay, switching from the set modulation mode to the configured modulation mode. In other words, only echo delay estimation and compensation are performed under the set modulation scheme.

The echo delay estimation method provided by the present application is exemplified by a plurality of exemplary embodiments. In the following exemplary embodiment, the ECHO delay estimation process in the single polarization case, the dual polarization case and the MIMO case is respectively explained based on ECHO 1 and ECHO 2 existing in the application scenario shown in fig. 1. The IDU and ODU are connected by an intermediate frequency cable, but the application is not limited thereto.

Fig. 3 is a diagram illustrating an application example of the echo delay estimation method according to an embodiment of the present application. The present exemplary embodiment describes an echo delay estimation method of an intermediate frequency cable under a single polarization condition; the preamble with a length of 64 symbols is selected as a known sequence, and according to an application scenario of microwave transmission, the maximum intermediate frequency cable length between the ODU and the IDU is selected to be 300 meters. In this example, given a bandwidth of 56M, a symbol rate of 50M, and a configured modulation scheme of 1024 QAM.

As shown in fig. 3, the implementation process of this embodiment includes:

s301, after the digital microwave communication device is powered on, because the configured modulation mode is 1024QAM, and the modulation order of the configured modulation mode is higher than the modulation order of the set modulation mode (for example, 16QAM), the modulation mode of the digital microwave communication device is switched to 16 QAM. When the modulation order of the configured modulation mode is lower than the modulation order of the set modulation mode, the configured modulation mode can be maintained unchanged; in this step, both the IDU and ODU of the digital microwave communication device need to switch the modulation scheme to 16 QAM.

The following describes a processing procedure of performing echo delay estimation after the IDU of the digital microwave communication device as the receiving end receives a signal.

S302, the receiving end eliminates various distortions except echo distortion by using a corresponding algorithm, and when synchronization and equalization are converged in sequence, the estimated value of SNR is stabilized to be more than 35dB and the jitter range is less than 3dB, an error signal e (namely the echo distortion signal) is obtained.

In this step, as shown in fig. 4, after the IDU at the receiving end receives the signal, the received signal is converted into a digital intermediate frequency signal by the digital intermediate frequency unit, and then processed by the synchronization unit and the equalization unit, and then an error signal e is output by the hard decision unit. The synchronization unit can be used for timing synchronization of signal demodulation decision and carrier and phase synchronization during coherent demodulation; the equalization unit may include signal processing operations to overcome various intersymbol interference. It should be noted that the present application does not limit the specific implementation manners of the digital intermediate frequency unit, the synchronization unit, the equalization unit, and the hard decision unit, as long as the corresponding functions can be achieved.

In this step, the SNR threshold set is 35 dB. Since the echo has a negligible effect on the performance of the digital microwave communication system when the SNR is below 35 dB. Therefore, if the SNR cannot reach the SNR threshold for a long time, exception handling is required, that is, the digital microwave communication device jumps out in time, and estimation and compensation of the echo delay are not performed any more. In this example, when the SNR cannot reach the SNR threshold for a long time, the modulation scheme of the data microwave communication device needs to be switched from 16QAM to 1024QAM, which is configured, and cannot be maintained at 16QAM with a lower modulation order.

S303, upsample the error signal e by 2 times, and then perform correlation calculation with a local known sequence (i.e., a local preamble sequence) which is also upsampled by 2 times.

In this step, as shown in fig. 5, the error signal e is up-sampled by 2 times, and then passes through a half-band filter, and according to the frame header information of the signal given after equalization, the error signal e up-sampled by 2 times is divided into two odd-even paths, and is respectively correlated with the local preamble sequence. The error signal e is up-sampled by 2 times, so that the odd and even paths can be distinguished subsequently. It should be noted that, for each divided path of the up-sampled signal, up-sampling may be performed after each path, and then correlation calculation may be performed. However, this is not limited in this application.

Wherein, since the maximum intermediate frequency cable length in this example is 300 meters, the length of one echo passing through is 2 times of the intermediate frequency cable length, i.e. 600 meters; the propagation speed of signals in the intermediate frequency cable is 2 x 10⁸m/s calculation, the maximum time delay of the echo is 600m/(2 multiplied by 10)⁸M/s) 3000ns, a symbol rate of 50M corresponds to a duration of 20ns per symbol, and thus the number of symbols between peak search regions corresponds to 3000/20-150. Since the adaptive equalization processing in S302 can eliminate the delay within 10 symbols, the delay within 10 symbols does not need to be estimated, and only needs to start from the frame header information given by the equalization, and start from the 11 th symbol after the frame header, perform 140 times of correlation calculation to obtain a group of correlation values (for example, sequentially select a sequence with a length of 64 symbols from the 11+ i th symbol after the frame header, calculate the correlation value between each selected sequence and the local preamble sequence, i is an integer greater than or equal to 0), find out the maximum peak value and the next maximum peak value therefrom, and record the occurrence position of the maximum peak value (for example, the offset frame header position information including the maximum peak value) and the occurrence position of the next maximum peak value (for example, the offset frame header position information including the next maximum peak value).

The above process only calculates the occurrence positions of the primary maximum peak and the secondary maximum peak. Since the presence of noise may cause a large error in a single calculation, a plurality of calculations may be employed to obtain the occurrence positions of a plurality of maximum peaks and second largest peaks, and the accurate maximum peak position and second largest peak position may be estimated based on the occurrence positions of the plurality of maximum peaks and second largest peaks. Illustratively, the appearance positions of the plurality of maximum peaks and the next largest peak may be obtained by 16 times of the above calculation process. However, this is not limited in this application.

It should be noted that, in the process of multiple computations, each computation uses data of a different physical frame. In other words, the correlation calculation can be performed for each of the plurality of physical frames of the error signal e and the local preamble sequence.

And S304, estimating two echo time delays.

In this step, for the occurrence positions of the 16 maximum peaks and the occurrence positions of the 16 minor peaks obtained in this example, the accurate maximum peak position and the accurate minor peak position may be respectively selected according to the flow shown in fig. 6, and then two echo delays may be calculated according to the intervals between the accurate maximum peak position and the accurate minor peak position and the frame header position of the signal frame given by the equalization, which may be denoted as echo delay1 and echo delay2, for example.

As shown in fig. 6, taking the maximum peak as an example, the screening process of the accurate maximum peak position includes:

s601, determining the appearance positions of one or more maximum peak values meeting set conditions as a position group, and counting the peak value appearance times (Num) of the position group; for example, any two occurrence positions where the number of symbols of an interval is less than or equal to a threshold (e.g., three or four) may be determined to belong to one position group;

after grouping, the arrangement of each position group can be obtained as shown in the following table:

position group	Number of peak occurrences
		Pos1	Num1
Pos2	Num2
		……	……

S602, respectively comparing the peak occurrence frequency of each position group with a set threshold value (NumThr), and screening out the position groups of which the peak occurrence frequency is greater than or equal to the set threshold value;

and if the peak value occurrence frequency of a certain position group is smaller than the set threshold value, deleting the position group in the upper table, otherwise, keeping the position group in the upper table.

S603, calculating the average position of the screened position group, namely the accurate maximum peak position.

Fig. 6 is only an exemplary implementation, in other implementations, still taking the maximum peak as an example, after the position groups are divided by S601 and the number of peak occurrences of each position group is counted, one position group with the largest number of peak occurrences may be directly screened, and the average position of the screened position group is calculated to determine as the accurate maximum peak position.

Also, with reference to the determination process of the exact maximum peak position, the exact minor peak position can be obtained based on the appearance positions of a plurality of minor peaks.

It should be noted that, in this example, as shown in fig. 5, when the error signal e after the upsampling is divided into multiple paths, correlation calculation and peak search may be performed on each path of signal, and then a statistical screening process of a maximum peak position and a second maximum peak position is performed according to a peak search result of the multiple paths of signals, and two echo time delays are calculated according to the finally determined maximum peak position and second maximum peak position.

After the maximum peak position and the second largest peak position are determined, two echo time delays can be obtained according to the interval between the maximum peak position and the position of the signal frame header given by the equalization and the interval between the second largest peak position and the position of the signal frame header given by the equalization.

In this example, after S304, after completing the echo delay compensation according to the estimated echo delay, the modulation scheme is switched from 16QAM to 1024 QAM.

Fig. 7 is a diagram of another application example of the echo delay estimation method according to the embodiment of the present application. The present exemplary embodiment explains an echo delay estimation method of an intermediate frequency cable under a dual polarization condition; wherein, a lead code is selected as a known symbol, and the length of the maximum intermediate frequency cable is set to be 300 meters. In this example, given a bandwidth of 112M, a symbol rate of 100M, and a configured modulation scheme of 1024 QAM.

As shown in fig. 7, the implementation process of this embodiment includes:

and S701, after the digital microwave transmission equipment is powered on, because the configured modulation mode is 1024QAM and the modulation order is higher than that of 16QAM (the modulation mode is set), the modulation mode of the digital microwave transmission equipment is switched to 16 QAM. S301 can be referred to for the description of S701, and therefore is not described herein again.

S702, after IDU of digital microwave communication equipment as a receiving end receives a signal, various distortions except echo distortion are eliminated, after frequency sweeping is completed, synchronization and equalization are converged in sequence, an estimated value of SNR is stabilized to be more than 35dB, and a jitter range is less than 3dB, and then an error signal e (namely the echo distortion signal) is obtained.

It should be noted that, in this example, after the digital microwave communication device is powered on, since the balanced slave path needs to be swept under dual polarization, and the time required for sweeping is in the order of seconds, the convergence determination of the balancing needs to be performed after the sweeping is completed.

S703, the error signal e is up-sampled by 2 times, and then correlation calculation is performed with the local known sequence (i.e., the local preamble sequence) which is also up-sampled by 2 times.

In this example, the maximum echo delay of a 300 meter if cable is 3000 ns; given a symbol rate of 100M, the period of each symbol is 10 ns; therefore, the number of symbols corresponding to the peak searching region is 3000/10 ═ 300 symbols, 290 correlation calculations need to be performed starting from the frame header information given by the equalization and starting from the 11 th symbol after the frame header, the maximum peak and the next largest peak are found out from the correlation calculations, and the occurrence positions of the maximum peak and the next largest peak are recorded.

And S704, estimating two echo time delays.

It should be noted that, for the description of each step of the present exemplary embodiment, reference may be made to the description of the exemplary embodiment shown in fig. 3, and therefore, the description is not repeated herein.

Fig. 8 is a diagram of another application example of the echo delay estimation method according to the embodiment of the present application. The present exemplary embodiment describes an echo delay estimation method of an intermediate frequency cable in an MIMO scenario; wherein the preamble is chosen as the known symbol and the maximum if cable length is set to 300 meters. In this example, given a bandwidth of 28M, a symbol rate of 25M, and a configured modulation scheme of QPSK.

In the present exemplary embodiment, since the modulation scheme configured by the digital microwave communication device itself is QPSK (Quadrature Phase Shift Keying), which belongs to a relatively low modulation scheme, it is not necessary to switch the modulation scheme.

As shown in fig. 8, the implementation process of this embodiment includes:

s801, after receiving the signal, the IDU of the digital microwave communication device as the receiving end eliminates various distortions except echo distortion by using a corresponding algorithm, and waits until synchronization and equalization converge in sequence, and the SNR estimated value is stabilized at 35dB or more, and the jitter range is less than 3dB, and then obtains an error signal e (i.e. the above mentioned echo distortion signal).

In the exemplary embodiment, after the digital microwave communication device is powered on, if the balanced slave path needs to be swept in the MIMO scene, and the time required for sweeping is in the order of seconds, the convergence determination of the balance needs to be performed after the sweeping is completed. If the frequency offset of the balanced slave path can be directly calculated in the MIMO scene, frequency sweeping is not needed, and the balanced convergence is judged after the frequency offset calculation of the balanced slave path is finished.

S802, the error signal e is up-sampled by 2 times, and then correlated with the local known sequence which is up-sampled by 2 times.

In this example, the maximum echo delay of the 300-meter intermediate frequency cable is 3000ns, where the given symbol rate is 25M, and the period of each symbol is 40ns, so that the number of symbols corresponding to the peak searching region is 3000/40 ═ 75 symbols, it is necessary to start from the frame header information given by equalization, start from the 11 th symbol after the frame header, perform 65 correlation calculations, find out the maximum peak and the next largest peak from the correlation calculations, and record the occurrence positions of the maximum peak and the next largest peak.

And S804, estimating two echo time delays.

Fig. 9 is a schematic diagram of an echo delay estimation device according to an embodiment of the present application. As shown in fig. 9, the echo delay estimation device provided in this embodiment includes: a signal acquisition module 901, a sampling processing module 902 and a delay estimation module 903; the signal acquiring module 901 is adapted to acquire an echo distortion signal; the sampling processing module 902 is adapted to perform up-sampling on the echo distortion signal and process a sampling result by using a known sequence to obtain a processing result; a delay estimation module 903 adapted to estimate the echo delay by peak search based on the processing result.

In an exemplary embodiment, the delay estimation module 903 may include: a peak position determination unit adapted to determine a maximum peak position and a next largest peak position based on the processing result; and the time delay calculating unit is suitable for estimating two echo time delays based on the determined maximum peak position, the determined second maximum peak position and the signal frame header position.

For the related description of the echo delay estimation device provided in this embodiment, reference may be made to the description of the above method embodiments, and therefore, the description thereof is not repeated herein.

In addition, an IDU of a digital microwave communication device is further provided in an embodiment of the present application, including: a signal receiving module, a memory and a processor, the signal receiving module being adapted to obtain an echo distorted signal, the memory being adapted to store a computer program which, when executed by the processor, performs the steps of the echo delay estimation method described above.

As shown in fig. 10, the IDU 1000 provided in this embodiment may include: signal receiving module 1001, processor 1002 and memory 1003.

In an exemplary embodiment, as shown in fig. 4, the signal receiving module 1001 may include: the device comprises a digital intermediate frequency unit, a synchronization unit, an equalization unit and a hard decision unit; the digital intermediate frequency unit is connected with the synchronization unit, the synchronization unit is connected with the equalization unit, and the equalization unit is connected with the hard decision unit. However, this is not limited in this application.

It should be understood that the processor 1002 may be a Central Processing Unit (CPU), and that the processor 1002 may be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), off-the-shelf programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

Memory 1003 may include both read-only memory and random-access memory, and provides instructions and data to processor 1002. A portion of the memory 1003 may also include non-volatile random access memory. For example, the memory 1003 may also store information of device types.

In implementation, the processing performed by IDU 1000 may be performed by integrated logic circuits in hardware or instructions in software. That is, the steps of the method disclosed in the embodiments of the present disclosure may be implemented by a hardware processor, or implemented by a combination of hardware and software modules in a processor. The software module may be located in a storage medium such as a random access memory, a flash memory, a read only memory, a programmable read only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory 1003, and the processor 1003 reads the information in the memory 1002, and completes the steps of the method in combination with the hardware. To avoid repetition, it is not described in detail here.

In addition, an embodiment of the present application further provides a computer-readable storage medium, which stores a computer program, and the computer program, when executed by a processor, implements the steps of the echo delay estimation method described above.

It will be understood by those of ordinary skill in the art that all or some of the steps of the methods, systems, functional modules/units in the devices disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be performed by several physical components in cooperation. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as is well known to those of ordinary skill in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by a computer. In addition, communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media as known to those skilled in the art.

Claims

1. An echo delay estimation method, comprising:

acquiring an echo distortion signal;

sampling the echo distortion signal, and processing a sampling result by using a known sequence to obtain a processing result;

based on the processing result, the echo time delay is estimated through peak value search.

2. The method of claim 1, wherein estimating an echo delay by peak search based on the processing result comprises:

determining a maximum peak position and a next largest peak position based on the processing result;

and estimating two echo time delays based on the maximum peak position, the secondary maximum peak position and the signal frame header position.

3. The method of claim 2, wherein determining a maximum peak location and a next largest peak location based on the processing results comprises:

aiming at a processing result of any physical frame of the echo distortion signal, finding a maximum peak value and a secondary peak value in a peak searching area, and obtaining the appearance position of the maximum peak value and the appearance position of the secondary peak value;

determining maximum peak positions and next-largest peak positions respectively based on the appearance positions of the L maximum peaks and the appearance positions of the L next-largest peaks obtained from the processing results of the L physical frames; wherein L is an integer greater than or equal to 1.

4. The method according to claim 3, wherein the determining the maximum peak position and the second largest peak position based on the appearance positions of the L maximum peaks and the appearance positions of the L second largest peaks obtained from the processing results of the L physical frames, respectively, comprises:

or, for the appearance positions of the L maximum peaks or the appearance positions of the L next largest peaks, respectively, the following processing is performed: determining one or more appearance positions meeting set conditions as a position group, and counting the peak value appearance times of the position group; and selecting a position group with the maximum occurrence frequency of the peak value, and calculating the average position of the selected position group.

5. The method of claim 1, wherein sampling the echo-distorted signal and processing the samples with a known sequence to obtain a processed result comprises:

carrying out N times of up-sampling on the echo distortion signal, dividing the up-sampled signal into M paths, and respectively processing the M paths of signals by utilizing a known sequence of the up-sampling N times;

n, M are positive integers, and N is greater than or equal to M.

6. The method of claim 1, wherein processing the sampling results using the known sequence comprises: and carrying out correlation operation on the sampling result and the known sequence.

7. The method of claim 1, wherein the acquiring the echo-distorted signal comprises:

eliminating distortion except echo distortion in the received signal;

and after the distortion except the echo distortion is eliminated, stabilizing the SNR to a set range within a set time length, and obtaining an echo distortion signal.

8. The method of claim 7, further comprising:

and when the distortion except the echo distortion is eliminated and the SNR can not reach the set range in the set time length, exiting the echo time delay estimation.

9. The method of any one of claims 1 to 8, wherein prior to said obtaining an echo-distorted signal, the method further comprises:

and when the modulation order of the configured modulation mode is higher than that of the set modulation mode, switching from the configured modulation mode to the set modulation mode.

10. The method of claim 9, wherein after estimating the echo delay by peak search, the method further comprises:

and after the echo delay compensation is completed according to the estimated echo delay, switching from the set modulation mode to the configured modulation mode.

11. An echo delay estimation device, comprising:

the signal acquisition module is suitable for acquiring an echo distortion signal;

the sampling processing module is suitable for sampling the echo distortion signal and processing a sampling result by using a known sequence to obtain a processing result;

and the time delay estimation module is suitable for estimating the echo time delay through peak value search based on the processing result.

12. The apparatus of claim 11, wherein the delay estimation module comprises:

a peak position determination unit adapted to determine a maximum peak position and a next largest peak position based on the processing result;

and the time delay calculating unit is suitable for estimating two echo time delays based on the maximum peak position, the secondary maximum peak position and the signal frame head position.

13. An indoor unit of a digital microwave communication device, comprising: a signal receiving module adapted to acquire an echo distorted signal, a memory adapted to store a computer program which, when executed by the processor, implements the steps of the echo delay estimation method of any of claims 1 to 10.

14. The indoor unit of claim 13, wherein the signal receiving module comprises: the device comprises a digital intermediate frequency unit, a synchronization unit, an equalization unit and a hard decision unit; the digital intermediate frequency unit is connected with the synchronization unit, the synchronization unit is connected with the equalization unit, and the equalization unit is connected with the hard decision unit.

15. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the echo delay estimation method according to one of claims 1 to 10.