Optical millimeter wave communication system and channel response estimation method thereof

Abstract

The application belongs to the technical field of optical millimeter wave communication, and particularly relates to an optical millimeter wave communication system and a channel response estimation method thereof, which can directly estimate the channel response in the optical millimeter wave communication system. The method first compensates the sampling frequency offset by using a filter equalization mode, then artificially adds a sampling frequency offset with a specific value by using the filter equalization mode, and finally performs cross-correlation synchronization on the transceiving signals and extracts synchronization peaks, wherein any one synchronization peak group is the estimated channel response. Compared with the prior art, the application has the advantages of simple implementation, low complexity, strong flexibility and the like, and since it is implemented in digital signal processing, the flexibility of the system can be greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical millimeter wave communication, in particular to an optical millimeter wave communication system and a channel response estimation method thereof. BACKGROUND

[0002] With the development of technology, the optical millimeter wave communication system can develop and utilize a broad and unused D-band millimeter wave frequency band, which has great prospects for the wireless communication system with increasingly scarce communication frequency bands. The D-band millimeter wave frequency band has a frequency as high as 110 GHz, which has a relatively high bandwidth, and transmitting a signal with a relatively high bandwidth and a relatively high symbol rate becomes a reasonable system setting. However, a relatively high symbol rate requires the system to have sufficient signal recovery capability. However, due to the limitation of physical devices, the channel response of the system usually has great non-ideality, which seriously damages the signal quality. Therefore, if the damage caused by the channel response of the system can be effectively compensated, the high baud rate high-speed millimeter wave wireless transmission system can be guaranteed, and important advantages can be played in future 6G and 7G communications. SUMMARY

[0003] The purpose of the present application is to provide an optical millimeter wave communication system and a channel response estimation method thereof, which is used for a single carrier pulse amplitude modulation signal in an intensity modulation envelope detection optical millimeter wave communication system, and aims to provide an effective, accurate, high sampling rate, and directly obtained system channel response method available at any time.

[0004] The purpose of the present application can be achieved by the following technical solutions:

[0005] A channel response estimation method based on sampling frequency offset is applied to an optical millimeter wave communication system, which compensates and artificially adds the sampling frequency offset in the optical millimeter wave communication system, correlates the transmitted signal and the received signal, and extracts a group of synchronization peaks to estimate the channel response.

[0006] The method comprises the following steps:

[0007] Obtaining a transmitted signal sent by a transmitting end and a received signal received by a receiving end in an optical millimeter wave communication system;

[0008] Compensating and artificially adding the sampling frequency offset of the received signal based on a fourth-order filter to obtain a compensated signal;

[0009] Correlating the transmitted signal and the compensated signal, and extracting a group of synchronization peaks to obtain a channel response estimation value.

[0010] The structure and calculation method of the fourth-order filter are as follows:

[0011]

[0012] wherein a[n] and b[n] are the input and output of the fourth-order filter respectively; c q (i) are fixed coefficients of the filter, determined according to given parameters q and i; m n and μ n is the correction number for the sampling frequency offset sequence, given by the following formula:

[0013] m n = int[(1+Δ)n]

[0014] μ n =(1+Δ)n-m n

[0015] wherein int[] is the integer function; Δ is the given sampling frequency offset value.

[0016] The fourth-order filter is used to sequentially perform sampling frequency offset compensation and artificial addition on the received signal to obtain a compensated signal, and the method comprises the following steps:

[0017] A first sampling frequency offset value is set as a parameter of a first fourth-order filter, a received signal is taken as an input, and an intermediate signal compensated by sampling frequency offset is output by the first fourth-order filter;

[0018] A second sampling frequency offset value is set as a parameter of a second fourth-order filter, the intermediate signal is taken as an input, and a compensated signal artificially added with sampling frequency offset is output by the second fourth-order filter.

[0019] The sending signal and the compensated signal are cross-correlated and synchronized, and one group of synchronization peaks is extracted to obtain a channel response estimation value, and the method comprises the following steps:

[0020] Let the second sampling frequency offset value be Δ2, the sending signal be and the compensated signal be y″[n]; the sending signal is a multi-frame signal composed of a single-frame sending signal x[n] of a length L which is cyclically sent, and the single-frame sending signal wherein d w [n] is a window function of a length L;

[0021] The cross-correlation of the single-frame sending signal x[n] and the compensated signal y″[n] is calculated:

[0022]

[0023] Based on the cross-correlation calculation, a group of synchronization peaks {R yx [0], R yx [1L], R yx [2L], … R yx[kL]}, and the channel response h l (t) is an estimate of the channel response h where k is an integer.

[0024] An optical millimeter wave communication system, comprising a digital signal processing module of a transmitting end, the transmitting end, a wireless transmission link, a receiving end, the transmitting end comprising a digital-to-analog converter, the receiving end comprising an analog-to-digital converter, the system further comprising a sampling frequency offset compensation module, an artificial sampling frequency offset adding module, a cross-correlation synchronization and synchronization peak group extracting module, a channel response estimation module,

[0025] The digital signal processing module of the transmitting end controls the transmitting end to send a transmitting signal, when the transmitting signal is a pulse amplitude modulation signal for normal communication, the transmitting signal is received by the receiving end through the wireless transmission link, and is converted into a digital sequence by the digital-to-analog converter in the receiving end to obtain a receiving signal, the receiving signal is compensated and an artificial sampling frequency offset in the optical millimeter wave communication system is added by the receiving signal in turn through the sampling frequency offset compensation module and the artificial sampling frequency offset adding module to obtain a compensated signal; the cross-correlation synchronization and synchronization peak group extracting module performs cross-correlation synchronization on the transmitting signal and the compensated signal, and extracts a group of synchronization peaks therefrom; the channel response estimation module outputs a channel response estimation value according to the group of synchronization peaks extracted by the cross-correlation synchronization and synchronization peak group extracting module.

[0026] The sampling frequency offset compensation module and the artificial sampling frequency offset adding module are implemented based on a fourth-order filter.

[0027] The structure and calculation method of the fourth-order filter are as follows:

[0028]

[0029] wherein a[n] and b[n] are the input and output of the fourth-order filter respectively; c q (i) is a fixed coefficient of the filter, determined according to given parameters q and i; m n and μ n is a correction serial number for the sampling frequency offset sequence, given by the following formula:

[0030] m n = int[(1+Δ)n]

[0031] μ n = (1+Δ)n-m n

[0032] wherein int[] is an integer function; Δ is a given sampling frequency offset value.

[0033] The sampling frequency offset compensation module performs the following steps: setting a first sampling frequency offset value as a parameter of a first fourth-order filter, taking a received signal as input, and outputting an intermediate signal after sampling frequency offset compensation using the first fourth-order filter;

[0034] The artificial sampling frequency offset module performs the following steps: setting the second sampling frequency offset value as a parameter of a second fourth-order filter, taking the intermediate signal as input, and using the second fourth-order filter to output a compensation signal with the artificial sampling frequency offset.

[0035] The cross-correlation synchronization and synchronization peak group extraction module performs the following steps:

[0036] The second sampling frequency offset value is Δ2, and the transmitted signal is The compensation signal is y″[n]; the sending signal is a multi-frame signal composed of a single-frame transmission signal x[n] of length L sent cyclically, then the single-frame transmission signal Among them, d w [n] is a window function with a length of L;

[0037] Calculate the cross-correlation between the single-frame transmitted signal x[n] and the compensated signal y″[n]:

[0038]

[0039] Extracting synchronous peak groups based on cross-correlation calculation {R yx [0],R yx [1L],R yx [2L],…R yx [kL]}, the synchronization peak group is the channel response h l (t) An estimate of , where k is an integer.

[0040] Compared to existing technologies, this invention innovatively leverages the impairment of sampling frequency offset to estimate channel response, offering greater flexibility, simplicity, and reduced complexity. Implemented within digital signal processing, this invention significantly enhances system flexibility and lays a solid foundation for further increases in the capacity and speed of future optical millimeter-wave communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flow chart of the method of the present invention;

[0042] Figure 2 This is a diagram of the system results of the present invention. DETAILED DESCRIPTION

[0043] The application will be described in detail below with reference to the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0044] Embodiment 1

[0045] The embodiment provides a channel response estimation method based on sampling frequency offset, applied to an optical millimeter wave communication system. The method compensates and artificially adds sampling frequency offset (SFO) caused by an ADC (analog-to-digital converter) and a DAC (digital-to-analog converter) in the optical millimeter wave communication system, performs cross-correlation synchronization on a transceiving signal, extracts a group of synchronization peaks, and estimates a channel response.

[0046] As shown in the method, the method comprises the following steps: Figure 1

[0047] S1, obtaining a sending signal sent by a sending end and a receiving signal received by a receiving end in an optical millimeter wave communication system.

[0048] When the sending signal sent by the sending end is a single-carrier pulse amplitude modulation signal for normal communication, the receiving signal is obtained by converting the receiving signal at the receiving end into a digital sequence through an analog-to-digital converter (ADC).

[0049] S2, sequentially performing sampling frequency offset compensation and artificial addition on the receiving signal based on a fourth-order filter to obtain a compensation signal.

[0050] In the embodiment, the structure and calculation mode of the fourth-order filter are as follows:

[0051]

[0052] Wherein, a[n] and b[n] are the input and output of the fourth-order filter respectively; c q (i) is a fixed coefficient of the filter, determined according to given parameters q and i; m n and μ n are the correction serial number of the sampling frequency offset sequence, given by the following formula:

[0053] m n =int[(1+Δ)n]

[0054] μ n =(1+Δ)n-m n

[0055] Wherein, int[] is an integer function; Δ is a given sampling frequency offset value.

[0056] Table 1 shows the values of the fixed coefficient c q (i) of the filter.​

[0057] Table 1

[0058] q＝0 q＝1 q＝2 q＝3 q＝4 i＝-3 -0.0596 0.1865 -0.0744 -0.0291 -0.0079 i＝-2 0.1732 -0.517 0.1845 0.1171 0.0155 i＝-1 -0.2643 1.074 -0.419 -0.3206 -0.0266 i＝0 0.1408 -1.3808 1.2717 0.923 0.0426 i＝1 0.1408 0.835 -1.9481 -0.0116 0.999 i＝2 -0.2643 -0.0497 1.2137 -0.9299 0.0131 i＝3 0.1732 -0.154 -0.3431 0.3514 -0.0155 i＝4 -0.0596 0.0445 0.132 -0.1351 0.0112

[0059] A first sampling frequency offset value Δ1 is set as a parameter of a first fourth-order filter, and an intermediate signal y'[n] compensated by sampling frequency offset is output by the first fourth-order filter with the received signal y[n] as input, so as to complete compensation of SFO;

[0060] A second sampling frequency offset value Δ2 is set as a parameter of a second fourth-order filter, and a compensation signal y''[n] compensated by artificially added sampling frequency offset is output by the second fourth-order filter with the intermediate signal y'[n] as input, so as to complete artificial addition of SFO.

[0061] S3, cross-correlation synchronization is performed on the transmitted signal and the compensation signal, and a group of synchronization peaks is extracted to obtain a channel response estimation value.

[0062] The transmitted signal is denoted as The compensation signal is y''[n]; wherein the transmitted signal is a multi-frame signal composed of a single-frame transmitted signal x[n] of a length L transmitted in a cycle, and the single-frame transmitted signal is a window function of a length L. w

[0063] The cross-correlation of the single-frame transmitted signal x[n] and the compensation signal y''[n] is calculated:

[0064]

[0065] A group of synchronization peaks {R yx [0], R yx [1L], R yx [2L], … R yx [kL]} is extracted based on the cross-correlation calculation, so as to obtain an estimation of the channel response h l (t) wherein k is an integer.

[0066] Embodiment 2

[0067] The above is the introduction of the method embodiment, and the scheme of the present application is further described through the system embodiment.

[0068] As Figure 2 ​​As shown, the embodiment provides a light-generated millimeter wave communication system, comprising a digital signal processing module of a sending end, the sending end (which comprises a DAC), a wireless transmission link, a receiving end (which comprises an ADC), a sampling frequency offset compensation module, an artificial sampling frequency offset adding module, a cross-correlation synchronization and synchronization peak group extracting module, a channel response estimation module,

[0069] The digital signal processing module of the sending end controls the sending end to send a sending signal, when the sending signal is a pulse amplitude modulation signal for normal communication, the sending signal is received by the receiving end through the wireless transmission link, and is converted into a digital sequence by the digital-to-analog converter in the receiving end to obtain a receiving signal, the receiving signal is compensated by the sampling frequency offset compensation module and the artificial sampling frequency offset adding module in turn, and the sampling frequency offset in the light-generated millimeter wave communication system is artificially added to obtain a compensated signal; the cross-correlation synchronization and synchronization peak group extracting module performs cross-correlation synchronization on the sending signal and the compensated signal, and extracts a synchronization peak group; and the channel response estimation module outputs a channel response estimation value according to the synchronization peak group extracted by the cross-correlation synchronization and synchronization peak group extracting module.

[0070] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the described modules can refer to the corresponding process in the foregoing method embodiments, which will not be described herein.

[0071] In addition, in another embodiment, the system can further comprise other DSPs of the receiving end, which further process the signal response estimation value output by the channel response estimation module to recover the original signal or perform other signal processing operations.

[0072] The present application first compensates the sampling frequency offset by using the filter equalization method, then artificially adds a sampling frequency offset of a specific value by using the filter equalization method, and finally performs cross-correlation synchronization on the sending signal and the receiving signal and extracts a synchronization peak, wherein any one synchronization peak group is the estimated channel response, which is simple, low in complexity and high in flexibility. Since it is realized in digital signal processing, the flexibility of the system can be greatly improved.

[0073] The foregoing describes in detail the preferred embodiments of the present application. It should be understood that those skilled in the art can make many modifications and changes without creative labor according to the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiments by those skilled in the art on the basis of the prior art according to the concept of the present application shall be within the protection scope defined by the claims.

Claims

1. A channel response estimation method based on sampling frequency offset, applied to optical millimeter wave communication system, characterized in that: This method compensates for and artificially adds sampling frequency offset in optical millimeter wave communication systems, performs cross-correlation synchronization on the transmit and receive signals, and extracts a group of synchronization peaks to estimate the channel response. The method comprises the following steps: Acquire a transmission signal sent by a transmitting end and a reception signal received by a receiving end in a photogenerated millimeter wave communication system; Based on the fourth-order filter, the sampling frequency offset compensation and artificial addition are performed on the received signal in sequence to obtain the compensated signal; The transmitted signal and the compensation signal are cross-correlated and synchronized, and a group of synchronization peaks are extracted to obtain a channel response estimation value.

2. The channel response estimation method based on sampling frequency offset according to claim 1, characterized in that: The structure and calculation method of the fourth-order filter are as follows: in, and are the input and output of the fourth-order filter respectively; is the fixed coefficient of the filter, according to the given parameters q and i Sure; and is the correction number for the sampling frequency offset sequence and is given by the following formula: in, is the rounding function; is the given sampling frequency offset value.

3. The channel response estimation method based on sampling frequency offset according to claim 1, characterized in that: The fourth-order filter is used to sequentially perform sampling frequency offset compensation and artificial addition on the received signal to obtain a compensated signal, specifically: Setting a first sampling frequency offset value as a parameter of a first fourth-order filter, taking the received signal as input, and using the first fourth-order filter to output an intermediate signal that has been compensated for the sampling frequency offset; The second sampling frequency offset value is set as a parameter of a second fourth-order filter, the intermediate signal is used as input, and the second fourth-order filter is used to output a compensation signal with an artificially added sampling frequency offset.

4. The channel response estimation method based on sampling frequency offset according to claim 3, characterized in that: The cross-correlation synchronization of the transmission signal and the compensation signal, and the extraction of a group of synchronization peaks to obtain the channel response estimation value are specifically: The second sampling frequency offset value is , the signal sent is , the compensation signal is ; The sending signal The length sent by the loop is L Single frame transmission signal If the multi-frame signal is composed of a single frame, the signal is sent ,in, The length is L Window function of Calculate the single frame transmission signal and compensation signal The cross-correlation of: Extracting synchronous peak groups based on cross-correlation calculation , and get the channel response middle An estimate of , where k is an integer.

5. A light-generated millimeter wave communication system, comprising a digital signal processing module at a transmitting end, a transmitting end, a wireless transmission link, and a receiving end, wherein the transmitting end includes a digital-to-analog converter and the receiving end includes an analog-to-digital converter, characterized in that: The system also includes a sampling frequency offset compensation module, an artificial sampling frequency offset addition module, a cross-correlation synchronization and synchronization peak group extraction module, and a channel response estimation module. The digital signal processing module of the transmitting end controls the transmitting end to send a transmitting signal. When the transmitting signal is a pulse amplitude modulation signal for normal communication, it is received by the receiving end through a wireless transmission link and converted into a digital sequence by a digital-to-analog converter in the receiving end to obtain a receiving signal. The receiving signal is sequentially compensated by a sampling frequency offset compensation module and an artificially added sampling frequency offset module, and the sampling frequency offset in the optical millimeter wave communication system is artificially added to obtain a compensated signal. The cross-correlation synchronization and synchronization peak group extraction module performs cross-correlation synchronization on the transmitting signal and the compensation signal, and extracts a group of synchronization peaks therefrom. The channel response estimation module outputs a channel response estimation value based on the synchronization peak group extracted by the cross-correlation synchronization and synchronization peak group extraction module. The sampling frequency offset compensation module and the artificial sampling frequency offset addition module are implemented based on a fourth-order filter.

6. The optically generated millimeter wave communication system according to claim 5, characterized in that: The structure and calculation method of the fourth-order filter are as follows: in, and are the input and output of the fourth-order filter respectively; is the fixed coefficient of the filter, according to the given parameters q and i Sure; and is the correction number for the sampling frequency offset sequence and is given by the following formula: in, is the rounding function; is the given sampling frequency offset value.

7. The optically generated millimeter wave communication system according to claim 5, characterized in that: The sampling frequency offset compensation module performs the following steps: setting a first sampling frequency offset value as a parameter of a first fourth-order filter, taking a received signal as input, and outputting an intermediate signal after sampling frequency offset compensation using the first fourth-order filter; The artificial sampling frequency offset module performs the following steps: setting the second sampling frequency offset value as a parameter of a second fourth-order filter, taking the intermediate signal as input, and using the second fourth-order filter to output a compensation signal with the artificial sampling frequency offset.

8. The optically generated millimeter wave communication system according to claim 5, characterized in that: The cross-correlation synchronization and synchronization peak group extraction module performs the following steps: The second sampling frequency offset value is , the signal sent is , the compensation signal is ; The sending signal The length sent by the loop is L Single frame transmission signal If the multi-frame signal is composed of a single frame, the signal is sent ,in, The length is L Window function of Calculate the single frame transmission signal and compensation signal The cross-correlation of: Extracting synchronous peak groups based on cross-correlation calculation , the synchronization peak group is the channel response middle An estimate of , where k is an integer.

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