Blind time sequence error detection method and system suitable for low signal-to-noise ratio, and storage medium

Blind timing error detection method, system and storage medium technology field suitable for low signal-to-noise ratio

[0001] The present invention relates to the technical field of blind timing error detection, and more specifically, to a blind timing error detection method, system and storage medium suitable for low signal-to-noise ratio.

Background technique

[0002] Orthogonal Frequency Division Multiplexing (OFDM) is developed from MCM (Multi-Carrier Modulation). OFDM technology is one of the realization methods of multi-carrier transmission schemes. Its modulation and demodulation are realized based on IFFT and FFT respectively. It is a multi-carrier transmission scheme with the lowest implementation complexity and the most widely used. The main idea of OFDM is: divide the channel into several orthogonal sub-channels, convert high-speed data signals into parallel low-speed sub-data streams, and modulate them for transmission on each sub-channel. Orthogonal signals can be separated by using related technologies at the receiving end, which can reduce mutual interference (ISI) between sub-channels. The signal bandwidth on each sub-channel is smaller than the relevant bandwidth of the channel. Therefore, each sub-channel can be regarded as flat fading. The cyclic prefix CP is added to eliminate the inter-symbol crosstalk. Moreover, due to the bandwidth of each sub-channel With only a small part of the original channel bandwidth, channel equalization becomes relatively easy.

[0003] Due to the advantages of OFDM technology, it is widely used in various communication systems, such as LTE, WLAN, PLC, and so on. However, due to the sampling deviation (SFO) in the actual communication system, the orthogonality of each sub-carrier is destroyed, and ICI (Inter-Channel Interference) interference will be introduced at the receiving end, which will also cause corresponding Distortion in the amplitude and phase of the sub-carrier reduces the quality of communication. Therefore, the receiving end must estimate and compensate the SFO accordingly to ensure the quality of communication.

[0004] At present, SFO extracts the timing error of each OFDM symbol mainly by piloting and using the phase difference of the two OFDM symbols before and after to estimate the corresponding sampling deviation, and then feedback to the previous compensation loop for corresponding correction. . However, this method will inevitably reduce the rate due to the insertion of the pilot frequency. Secondly, because the two OFDM symbols before and after the differential operation are used, if the signal-to-noise ratio environment is low, it will inevitably introduce large noise, so the estimation error will be very large. This method is generally only suitable for environments with better channel conditions. In the power line environment, due to the large noise, the performance of the timing error is greatly deteriorated, which leads to the failure of the entire loop to converge to the expected value.

Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a blind timing error detection method, system and storage medium suitable for low signal-to-noise ratio in view of the above-mentioned defects of the prior art.

[0006] The technical solution adopted by the present invention to solve its technical problems is: according to the first aspect of the present invention, a blind timing error detection method suitable for low signal-to-noise ratio is provided, which includes the steps:

[0007] Perform frequency domain equalization on each subcarrier of each OFDM symbol to eliminate the influence of channel phase;

[0008] A timing error detection module is used to make a decision on each sub-carrier of each OFDM symbol to eliminate the influence of the information phase;

[0009] Perform an estimation operation on each subcarrier of each OFDM symbol to extract the timing error em.

[0010] Preferably, each of the OFDM symbols includes a plurality of different subcarriers, and it is assumed that the mth OFDM symbol

The subcarrier data of the kth subcarrier is ym(k), and the channel coefficient of the kth subcarrier is hk;

[0011] The frequency domain equalization performed on each subcarrier of each OFDM symbol to eliminate the influence of the channel phase is specifically:

[0012] Perform frequency domain equalization on the sub-carriers of each OFMD symbol to obtain sub-carrier data xm (k);

[0013] Preferably, the frequency domain equalization is performed on the subcarriers of each OFMD symbol, and the subcarrier data Xm(k) after the frequency domain equalization is:

[0014] x_m(k) =y_m(k)/hk .

[0015] Preferably, the use of a timing error detection module to make a decision on each subcarrier of each OFDM symbol to eliminate the influence of the information phase specifically includes the steps:

[0016] For each of the subcarrier data xm(k), a decision mechanism is used to eliminate the influence of the information phase to obtain phm(k);

[0017] The Early-late method is used to obtain Ye (k) and Yi (k) by taking values before and after each of the phm (k) respectively.

[0018] Preferably, the use of a decision mechanism for each of the sub-carrier data to eliminate the influence of the information phase to obtain phm (k) is specifically:

[0019] A decision mechanism is adopted for each of the subcarrier data Xm (k) after the frequency domain equalization to obtain the corresponding dm (k), and then the influence of the channel phase is eliminated to obtain the phm (k):

[0020] dm (k) = fun (x_m (k)) (2)

[0021] phm (k) = Xm (k) /dm (k) (3)

[0022] Wherein, the fun () is a decision mechanism.

[0023] Preferably, the EarlyTate method is used to take values before and after each of the phm (k) to obtain Ye (k) and

Yi(k), specifically:

[0024] Y_e (k) =phm(k) · e^-j2ltk8/N

[0025] Yi (k) =phm(k) · e^j2ltk8/N (4)。

[0026] Preferably, the operation is performed on each subcarrier of each OFDM symbol to extract the timing error em, and the specific formula of the timing error em is:

[0027]/= ^Rc-%)

[0028] Preferably, before the step of performing frequency domain equalization on each sub-carrier of each OFDM symbol to eliminate the influence of the channel phase, the method further includes:

[0029] receiving at least one OFDM symbol;

[0030] After the step of performing an estimation operation on each subcarrier of each OFDM symbol to extract a timing error em, the method further includes:

[0031] The timing error em is sent to the loop filter.

[0032] According to another aspect of the present invention, there is also provided a blind timing error detection system suitable for low signal-to-noise ratio. The blind timing error detection system suitable for low signal-to-noise ratio includes:

[0033] one or more processors;

[0034] The memory is used to store one or more computer programs, and the one or more processors are used to execute the one or more computer programs stored in the memory, so that the one or more processors execute the above The described blind timing error detection method suitable for low signal-to-noise ratio.

[0035] According to another aspect of the present invention, a computer-readable storage medium is also provided, and the storage medium stores

There is a computer program that, when executed, realizes the blind timing error detection method suitable for low signal-to-noise ratio as described above.

[0036] The implementation of the present invention is suitable for a low signal-to-noise ratio blind timing error detection method and technical solution of the system, which has the following advantages or beneficial effects: the present invention focuses on the timing error detection module, which mainly uses the timing error detection technology to eliminate the information phase And extract the timing error, so that only one OFDM symbol needs to be estimated; and the use of the decision mechanism avoids the use of pilots, which can increase the communication rate; then use the Early-late idea to extract the corresponding timing error and send it Loop filter; suitable for power line environment with very low signal-to-noise ratio, and the effect is very good.

Description of the drawings

[0037] In order to more clearly describe the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings that need to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative work, other drawings can be obtained based on these drawings. In the drawings:

[0038] FIG. 1 is a general flowchart of the estimation and compensation of sampling deviation in the OFMD communication system;

[0039] FIG. 2 is a flowchart of an embodiment of a blind timing error detection method suitable for low signal-to-noise ratio of the present invention.

Detailed ways

[0040] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the various exemplary implementation examples to be described below will refer to the corresponding drawings, which constitute a part of the exemplary embodiments, which describe Various exemplary embodiments that may be used to implement the present invention, unless otherwise indicated, the same numbers in different drawings indicate the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present disclosure. It should be understood that they are only examples of devices and methods that are consistent with some aspects disclosed in the present invention as detailed in the appended claims, and other embodiments may be used, or the embodiments listed herein may be carried out. Structural and functional modifications will not depart from the scope and essence of the present invention. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from obstructing the description of the present invention.

[0041] In order to illustrate the technical solution of the present invention, the following is described by specific embodiments.

[0042] Embodiment One:

[0043] In general communication modules and devices, in the baseband of the receiving end, due to the ADC sampling clock deviation (SFO), there is generally a timing error detection module (Timing Error Detector, TED) (TED for short) in the baseband. Module).

[0044] As shown in Figure 1, the figure describes the general flow chart of the estimation and compensation of sampling deviation (SFO) in the OFMD communication system; the INTERP module refers to the time domain interpolation module, which adjusts the input signal according to the current NCO value Sampling deviation to compensate the timing error derived from the estimation calculation; FFT module means to convert the OFDM signal in the time domain to the frequency domain to obtain the received data ym(k) of each subcarrier; the FEQ module means to convert the current OFDM symbol Frequency domain equalization is performed on each sub-carrier of, and xm(k) is obtained, thereby eliminating the influence of channel phase; TED module refers to the signal after the current frequency domain equalization, making a decision to eliminate the influence of information phase, and at the same time performing timing error The LF module (loop filter) refers to the loop filter, which further filters the timing error derived from the TED estimation operation to eliminate the influence of high-frequency noise; the NCO module is an exponentially controlled oscillator, which is adjusted according to the signal from LF The influence of sampling deviation.

[0045] The focus of the present invention is the timing error detection module, which mainly uses coherent detection technology to eliminate information phase

The impact of the bit and extract the timing error, so that only one OFDM symbol needs to be estimated; and the use of the decision mechanism to avoid the use of pilots, which can increase the communication rate; then use the EarlyTate idea to extract the corresponding timing error, and send it to the loop Path filter; the present invention is suitable for power line environment with very low signal-to-noise ratio.

[0046] As shown in FIG. 2, the present invention provides an embodiment of a blind timing error detection method suitable for low signal-to-noise ratio, including the steps:

[0047] S10. Receive at least one OFDM symbol;

[0048] S20. Perform frequency domain equalization on each subcarrier of each OFDM symbol to eliminate the influence of channel phase;

[0049] S30. Use the timing error detection module to make a decision on each subcarrier of each OFDM symbol to eliminate the influence of the information phase; specifically, use the timing error detection module to equalize each subcarrier of each OFDM symbol in the frequency domain After the signal is judged to eliminate the influence of the information phase;

[0050] S40. Perform an estimation operation on each subcarrier of each OFDM symbol to extract the timing error em;

[0051] S50. Send the timing error em into a loop filter. Specifically, the timing error em (timing error) is sent to a loop filter (Loop Filter or loop filter), and the timing error is made more accurate through long-term statistics.

[0052] In this embodiment, each OFDM symbol may include a plurality of different subcarriers, assuming that the subcarrier data of the kth subcarrier of the mth OFDM symbol is ym(k), the channel coefficient of the kth subcarrier For hk, the number of OFDM symbols is different in different systems and can be any value.

[0053] S20. Perform frequency domain equalization on each subcarrier of each OFDM symbol to eliminate the influence of the channel phase.

[0054] Specifically, frequency domain equalization is performed on the subcarriers of each OFMD symbol to obtain subcarrier data xm(k); specifically, the frequency domain equalization is performed on the subcarriers of each OFMD symbol, and the subcarriers after frequency domain equalization are The carrier data xm(k) is: [0055] x_m(k) =y_m(k)/hk .

[0056] S30. The use of the timing error detection module to determine each subcarrier of each OFDM symbol to eliminate the influence of the information phase specifically includes the following steps:

[0057] S31. A decision mechanism is adopted for each subcarrier data Xm(k) to eliminate the influence of the information phase to obtain phm(k). Specifically, a decision is adopted for each subcarrier data Xm(k) after frequency domain equalization. The mechanism obtains the corresponding dm (k), and then eliminates the influence of the information phase to obtain Phm(k):

[0058] dm (k) = fun (x_m (k)) (2)

[0059] phm (k) = Xm (k) /dm (k) (3)

[0060] Wherein, the judgment mechanism does not have a direct formula, and the abstract formula of the judgment mechanism is fun (), and fun () is a judgment mechanism, that is, a direct-decided mechanism.

[0061] S32. Use the Early-late method to obtain Ye (k) and Yi (k) by taking values before and after each phm (k) respectively.

[0062] Specifically, the use of the EarlyTate method to obtain Ye (k) and Yi (k) respectively before and after each phm (k) is specifically as follows:

[0063]

Y_e(k) = ph_rll(k)-eY_l(k) = ph_m(k)-e^J2^ ⑷。

[0064] S40. Perform an estimation operation on each subcarrier of each OFDM symbol to extract the timing error em, and the specific formula of the timing error em is:

[0065] "Zhu Jie and a m) * .

[0066] The focus of the present invention is the TED module, which mainly uses timing error detection technology to eliminate the influence of the channel, so that only one OFDM symbol needs to be estimated; and the use of a decision mechanism avoids the use of pilots, which can increase the communication rate; reuse The EarlyTate idea extracts the corresponding timing error, which is suitable for power line environment such as low signal-to-noise ratio environment. [0067] The second embodiment:

[0068] The present invention also provides an embodiment of a blind timing error detection system suitable for low signal-to-noise ratio, including one or more processors and memories; wherein, the memory is used to store one or more computer programs, so The one or more processors are used to execute one or more computer programs stored in the memory, so that the processors execute the steps of the embodiment of the blind timing error detection method suitable for low signal-to-noise ratio described in the first embodiment.

[0069] Embodiment Three:

[0070] The present invention also provides a computer-readable storage medium. Those of ordinary skill in the art can understand that all or part of the steps in the foregoing method embodiments can be implemented by computer program-related hardware. The aforementioned computer program may be stored in a computer-readable storage medium, and the storage medium stores the computer program. When the computer program is executed (such as a processor), it executes the low signal-to-noise ratio described in the first embodiment. The above-mentioned storage medium includes: ROM, RAM, magnetic disk or optical disc, etc., which can store program code. [0071] After reading the content described in this article, those skilled in the art should understand that the various features described in this article can be implemented by methods, data processing systems, or computer program products. Therefore, these features can be expressed without using hardware, all using software, or using a combination of hardware and software. In addition, the above-mentioned features can also be expressed in the form of a computer program product stored on one or more computer-readable storage media containing computer-readable program code segments or instructions, which are stored in the storage Medium. The readable storage medium is configured to store various types of data to support operations on the device. The readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof. Such as static hard disk, random access memory (SRAM), electrically erasable Programmable Read Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Read Only Memory (PROM), Read Only Memory (ROM), Optical Storage Device, Magnetic Storage Device, Flash Memory, Disk Or CD and/or a combination of the above devices.

[0072] The above are only preferred embodiments of the present invention. Those skilled in the art know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific conditions and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application belong to the protection scope of the present invention.