CN109391575B - Time domain signal preprocessing method and device, readable storage medium and receiver - Google Patents
Time domain signal preprocessing method and device, readable storage medium and receiver Download PDFInfo
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Abstract
A time domain signal preprocessing method and device, a readable storage medium and a receiver are provided, wherein the method comprises the following steps: performing analog-to-digital conversion on a received signal to obtain a digital signal, wherein the received signal comprises a cyclic prefix and data, and the digital signal comprises a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate; before the digital signal is downsampled by using a second sampling rate, discarding a part of a first sampling point of a cyclic prefix according to the proportion of the first sampling rate to the second sampling rate; utilizing a second sampling rate to carry out down-sampling on the discarded digital signal, and removing a second sampling point obtained by down-sampling the cyclic prefix at the second sampling rate; and performing time-frequency transformation on the signal without the cyclic prefix to obtain frequency domain data. The technical scheme of the invention can realize the integral point sampling of the CP on the premise of saving the power consumption of the system and ensure the accuracy of data receiving.
Description
Technical Field
The present invention relates to the field of communications, and in particular, to a time domain signal preprocessing method and apparatus, a readable storage medium, and a receiver.
Background
To address the limited capacity of cellular networks, the 3rd Generation Partnership Project (3 GPP) organization introduced a cellular-based Narrowband Internet of things (NB-Iot) technology in Release13 (Release13) of the communication standard. Meanwhile, in order to ensure compatibility with the existing Long Term Evolution (LTE) system and ensure that physical layer characteristics are basically consistent, the system bandwidth of the NB-Iot is 180 KHz. According to the Nyquist sampling rate theorem, the sampling rate of the NB-Iot system can be greatly reduced, so that the power consumption of the system is saved.
In the prior art, in a conventional LTE network, a minimum integer sampling rate of a Cyclic Prefix (CP) is 1.92MHz (megahertz). Under a sampling rate of 1.92MHz, the CP length of symbol 0 corresponding to each slot (slot) is 10 samples, and the other symbols are 9 samples. In NB-Iot, when the sampling rate is lower than 1.92MHz with the decrease of the sampling rate, the number of CP sampling points is non-integer, and the non-integer sampling problem of CP needs to be considered and processed, which may cause that the initial phases of the frequency domain signals of each symbol may not be aligned, and channel estimation may not be performed. To ensure integer point sampling of the CP, one approach is to keep the lowest sampling rate at the digital front-end at 1.92MHz, and the other approach is to add a digital up-sampling mechanism before the CP is removed.
However, if the integer sampling points of the CP are guaranteed by the above method, the sampling rate cannot be lower than 1.92MHz before the CP is removed, and the system power consumption is increased.
Disclosure of Invention
The invention solves the technical problem of how to realize the integral point sampling of the CP on the premise of saving the system power consumption and ensure the accuracy of data receiving.
In order to solve the above technical problem, an embodiment of the present invention provides a time domain signal preprocessing method, where the time domain signal preprocessing method includes: performing analog-to-digital conversion on a received signal to obtain a digital signal, wherein the received signal comprises a cyclic prefix and data, and the digital signal comprises a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate; discarding a portion of a first sample point of the cyclic prefix according to a ratio of the first sample rate to a second sample rate before downsampling the digital signal using the second sample rate; utilizing the second sampling rate to carry out down-sampling on the digital signal after the dropping operation, and removing a second sampling point obtained by the down-sampling of the cyclic prefix at the second sampling rate; and performing time-frequency transformation on the signal without the cyclic prefix to obtain frequency domain data.
Optionally, the discarding a part of the first sample point of the cyclic prefix according to the ratio of the first sample rate to the second sample rate includes: dropping a portion of the first sampling points of the cyclic prefix prior to filtering the digital signal such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
Optionally, the discarding a part of the first sample point of the cyclic prefix according to the ratio of the first sample rate to the second sample rate includes: after filtering the digital signal, dropping a portion of the first sampling points of the cyclic prefix such that the number of first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
Optionally, the number of second sampling points of the cyclic prefix is an integer.
Optionally, the performing time-frequency transform on the signal without the cyclic prefix includes: and performing FFT (fast Fourier transform) on a second sampling point obtained by sampling the data at the second sampling rate.
Optionally, before downsampling the digital signal by using the second sampling rate, discarding a part of the first sampling point of the cyclic prefix according to a ratio of the first sampling rate to the second sampling rate includes: and before the digital signal is subjected to the last downsampling by using the second sampling rate, discarding a part of the first sampling point of the cyclic prefix according to the ratio of the first sampling rate to the second sampling rate.
The embodiment of the invention also discloses a time domain signal preprocessing device which is used for the receiver, and the time domain signal preprocessing device comprises: the digital signal processing device comprises a conversion module, a processing module and a processing module, wherein the conversion module is suitable for carrying out analog-to-digital conversion on a received signal to obtain a digital signal, the received signal comprises a cyclic prefix and data, and the digital signal comprises a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate; a preprocessing module adapted to discard a portion of a first sample point of the cyclic prefix according to a ratio of the first sample rate to a second sample rate before downsampling the digital signal using the second sample rate; the removal module is suitable for utilizing the second sampling rate to carry out down-sampling on the digital signal after the removal operation and removing a second sampling point obtained by the down-sampling of the cyclic prefix at the second sampling rate; and the time-frequency transformation module is suitable for performing time-frequency transformation on the signal without the cyclic prefix so as to obtain frequency domain data.
Optionally, the preprocessing module includes: a first pre-processing unit adapted to drop a portion of the first sampling points of the cyclic prefix before filtering the digital signal, such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
Optionally, the preprocessing module includes: a second preprocessing unit adapted to drop a portion of the first sampling points of the cyclic prefix after filtering the digital signal, such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
Optionally, the number of second sampling points of the cyclic prefix is an integer.
Optionally, the time-frequency transform module performs FFT on a second sampling point obtained by sampling the data at the second sampling rate.
Optionally, before the digital signal is downsampled for the last time by using the second sampling rate, the preprocessing module discards a part of the first sampling point of the cyclic prefix according to a ratio of the first sampling rate to the second sampling rate.
The embodiment of the invention also discloses a readable storage medium, wherein computer instructions are stored on the readable storage medium, and the computer instructions execute the steps of the time domain signal preprocessing method when running.
The embodiment of the invention also discloses a receiver which comprises a memory and a processor, wherein the memory is stored with computer instructions capable of running on the processor, and the processor executes the steps of the time domain signal preprocessing method when running the computer instructions.
The embodiment of the invention also discloses another time domain signal preprocessing method, which comprises the following steps: performing analog-to-digital conversion on a received signal to obtain a digital signal, wherein the received signal comprises a cyclic prefix and data, and the digital signal comprises a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate; before the digital signal is downsampled by using a second sampling rate, removing a part of a second sampling point of the cyclic prefix under the second sampling rate according to the proportion of the first sampling rate and the second sampling rate to obtain a signal with the cyclic prefix removed, wherein the second sampling rate is smaller than the first sampling rate; and performing time-frequency transformation and phase compensation on the signal without the cyclic prefix to obtain frequency domain data.
Optionally, after filtering the digital signal, removing a portion of a second sampling point of the cyclic prefix at a second sampling rate according to a ratio of the second sampling rate to the first sampling rate includes: and after filtering the digital signal and performing downsampling by using the second sampling rate, removing integer sampling points of second sampling points of the cyclic prefix at the second sampling rate, wherein the numerical values of the integer sampling points are obtained by calculating the number of the first sampling points of the cyclic prefix and the proportion.
Optionally, the performing FFT on the signal from which the cyclic prefix is removed includes: and carrying out phase compensation on the frequency domain data by utilizing the value of the non-integer sampling point of the second sampling point of the cyclic prefix.
Optionally, the performing phase compensation on the frequency domain data by using the value of the non-integer sampling point of the second sampling point of the cyclic prefix includes calculating a phase compensation factor by using the value of the non-integer sampling point, so as to perform phase compensation on the frequency domain data.
Optionally, the phase compensation factor is calculated by using the following formula:
where i is a complex factor, K is a subcarrier index, fsFor the purpose of the second sampling rate, the first sampling rate,
for the end position of the cyclic prefix at the second sampling rate,
n is a symbol number, and n is a symbol number,
represents the time length, T, corresponding to the cyclic prefix of the symbol jsIs the sample duration at the first sample rate.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
the technical scheme of the invention carries out analog-to-digital conversion on a received signal to obtain a digital signal, wherein the received signal comprises a cyclic prefix and data, and the digital signal comprises a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate; discarding a portion of a first sample point of the cyclic prefix according to a ratio of the first sample rate to a second sample rate before downsampling the digital signal using the second sample rate; utilizing the second sampling rate to carry out down-sampling on the digital signal after the dropping operation, and removing a second sampling point obtained by the down-sampling of the cyclic prefix at the second sampling rate; and performing time-frequency transformation on the signal without the cyclic prefix to obtain frequency domain data. According to the technical scheme, a part of the first sampling points of the cyclic prefix is discarded according to the proportion of the first sampling rate to the second sampling rate, so that after the digital signal is downsampled by using the second sampling rate, the number of the obtained second sampling points is an integer, all the second sampling points of the cyclic prefix can be removed, the frequency domain data obtained through time-frequency conversion is guaranteed to be the data part of the digital signal, and the accuracy of data receiving is guaranteed. Furthermore, the second sampling rate can meet the Nyquist sampling theorem through the technical scheme of the invention, and a smaller sampling rate can be adopted before the cyclic prefix is removed, so that the clock frequency of the digital front end is greatly reduced, and the power consumption of the receiver is reduced.
Further, the discarding a portion of the first sample point of the cyclic prefix according to the ratio of the first sample rate to the second sample rate comprises: dropping a portion of the first sampling points of the cyclic prefix prior to filtering the digital signal such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio. The technical scheme of the invention can reduce the coupling complexity of the hardware part of the digital filtering operation and the subsequent downsampling operation by discarding a part of the first sampling point of the cyclic prefix before the digital filtering, thereby realizing the simplicity and the easy implementation of the data receiving system on the basis of ensuring the accuracy of data receiving.
Further, the discarding a portion of the first sample point of the cyclic prefix according to the ratio of the first sample rate to the second sample rate comprises: after filtering the digital signal, dropping a portion of the first sampling points of the cyclic prefix such that the number of first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio. According to the technical scheme, part of the first sampling point of the cyclic prefix is lost after digital filtering, so that all the first sampling points of the cyclic prefix can be fully utilized in the digital filtering part, intersymbol Interference (ISI) of signals is reduced, and the accuracy of data receiving is further ensured.
Drawings
FIG. 1 is a flow chart of a time domain signal preprocessing method according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a time domain signal preprocessing apparatus according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a receiver according to an embodiment of the present invention.
Detailed Description
As described in the background art, if the integer sampling points of the CP are guaranteed by the above method, the sampling rate cannot be lower than 1.92MHz before the CP is removed, and the power consumption of the system is increased.
According to the technical scheme, a part of the first sampling points of the cyclic prefix is discarded according to the proportion of the first sampling rate to the second sampling rate, so that after the digital signal is downsampled by using the second sampling rate, the number of the obtained second sampling points is an integer, all the second sampling points of the cyclic prefix can be removed, the frequency domain data obtained through time-frequency conversion is guaranteed to be the data part of the digital signal, and the accuracy of data receiving is guaranteed. Furthermore, the second sampling rate can meet the Nyquist sampling theorem through the technical scheme of the invention, and a smaller sampling rate can be adopted before the cyclic prefix is removed, so that the clock frequency of the digital front end is greatly reduced, and the power consumption of the receiver is reduced.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Fig. 1 is a flowchart of a time-domain signal preprocessing method according to an embodiment of the present invention.
The time domain signal preprocessing method shown in fig. 1 may be applied to a receiver, and the time domain signal preprocessing method may include the steps of:
step S101: performing analog-to-digital conversion on a received signal to obtain a digital signal, wherein the received signal comprises a cyclic prefix and data, and the digital signal comprises a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate;
step S102: discarding a portion of a first sample point of the cyclic prefix according to a ratio of the first sample rate to a second sample rate before downsampling the digital signal using the second sample rate;
step S103: utilizing the second sampling rate to carry out down-sampling on the digital signal after the dropping operation, and removing a second sampling point obtained by the down-sampling of the cyclic prefix at the second sampling rate;
step S104: and performing time-frequency transformation on the signal without the cyclic prefix to obtain frequency domain data.
In an implementation, the receiver receives an analog signal, so in step S101, the received signal may be subjected to analog-to-digital conversion. The analog signal includes a Cyclic Prefix (CP) and data (data); the analog-to-digital conversion operation is equivalent to the sampling operation, so that the first sampling point of the cyclic prefix at the first sampling rate and the first sampling point of the data at the first sampling rate can be obtained through step S101. The analog signal is sampled by adopting the first sampling rate, so that the number of first sampling points of the cyclic prefix under the first sampling rate can be ensured to be an integer.
Specifically, the first sampling rate is N × 1.92MHz, where N is a positive integer. For example, in the LTE system, the single carrier has a maximum bandwidth of 20M, and the first sampling rate is 30.72 MHz.
It should be understood by those skilled in the art that the cyclic prefix may be a normal cyclic prefix (normal cyclic prefix) or an Extended cyclic prefix (Extended cyclic prefix).
In a specific implementation, when a Narrowband Internet of things (NB-Iot) technology is used, a system bandwidth of a signal is narrowed, for example, 180KHz may be used. In this case, a lower sampling rate may be employed to reduce receiver power consumption. That is, after step S101, the digital signal may also be downsampled using the second sampling rate. However, in order to ensure that the number of second sampling points of the cyclic prefix at the second sampling rate is an integer, a part of the first sampling points of the cyclic prefix may be discarded according to the ratio of the first sampling rate to the second sampling rate through step S102.
Specifically, the first sampling rate and the second sampling rate may be expressed by a sampling frequency or a sampling time. For example, if the sampling frequency is fs, the sampling time Ts is 1/fs. Specifically, the second sampling rate may be a frequency of 240KHz, 480KHz, or the like.
Further, in step S103, after the digital signal after the dropping operation is down-sampled at the second sampling rate, the number of second sampling points of the cyclic prefix at the second sampling rate is an integer. The second sampling point obtained by the cyclic prefix sampled at the second sampling rate can be removed, so that the purpose of removing all cyclic prefixes in the digital signal is achieved. Through step S103, the obtained digital signal includes only the data (data) portion.
Furthermore, in step S104, the signal without the cyclic prefix is subjected to time-frequency transformation to obtain frequency domain data, so that the subsequent steps further process the frequency domain data. For example, channel estimation, interpolation filtering, and the like are performed on the frequency domain data.
According to the embodiment of the invention, a part of the first sampling points of the cyclic prefix is discarded according to the proportion of the first sampling rate and the second sampling rate, so that after the digital signal is downsampled by using the second sampling rate, the number of the obtained second sampling points is an integer, all the second sampling points of the cyclic prefix can be removed, the frequency domain data obtained through time-frequency conversion is ensured to be the data part of the digital signal, and the accuracy of data receiving is ensured. Furthermore, the second sampling rate can meet the Nyquist sampling theorem through the technical scheme of the invention, and a smaller sampling rate can be adopted before the cyclic prefix is removed, so that the clock frequency of the digital front end is greatly reduced, and the power consumption of the receiver is reduced.
Preferably, the number of second sampling points of the cyclic prefix is an integer.
In this embodiment, after a part of the first sampling point of the cyclic prefix is discarded according to the ratio of the second sampling rate to the first sampling rate, the number of the second sampling points of the cyclic prefix is an integer. For example, at a first sampling rate of 30.72MHz, the first number of sample points of the cyclic prefix is 160; when the second sampling rate is 480KHz, the ratio of the first sampling rate to the second sampling rate is 64; the first number of sample points 160 does not divide the ratio by 64, so that a portion of the first sample points, namely 32 first sample points, need to be discarded; the remaining 128 first sample points may be divided by the ratio of 64, i.e., the second number of sample points for the cyclic prefix at the second sampling rate is 2 (i.e., the ratio of 128 to the ratio of 64).
In another preferred embodiment of the present invention, when the sampling rate before sampling by using the second sampling rate is greater than 1.92MHz, the sampling rate is first down-sampled to 1.92MHz to serve as the first sampling rate. And discarding a part of the first sampling point of the cyclic prefix according to the ratio of the first sampling rate to the second sampling rate.
For example, at a first sampling rate of 1.92MHz, the first number of sample points of the cyclic prefix is 10; when the second sampling rate is 480KHz, the ratio of the first sampling rate to the second sampling rate is 4; the number of the first sampling points 10 cannot divide the ratio by 4, so that a part of the first sampling points needs to be discarded, namely 2 first sampling points are discarded; the remaining 8 first samples may be divided by the ratio of 4, i.e., the second number of samples of the cyclic prefix at the second sampling rate is 2 (i.e., the ratio of 8 to the ratio of 4).
Preferably, step S102 may include the steps of: dropping a portion of the first sampling points of the cyclic prefix prior to filtering the digital signal such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
The embodiment of the invention can reduce the coupling complexity of the hardware part of the digital filtering operation and the subsequent downsampling operation by discarding a part of the first sampling point of the cyclic prefix before the digital filtering, thereby realizing the simplicity and the easy implementation of the data receiving system on the basis of ensuring the accuracy of data receiving.
Preferably, step S102 may include the steps of: after filtering the digital signal, dropping a portion of the first sampling points of the cyclic prefix such that the number of first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
The embodiment of the invention can make full use of all the first sampling points of the cyclic prefix in the digital filtering part by discarding part of the first sampling points of the cyclic prefix after the digital filtering, reduce the Inter Symbol Interference (ISI) of the signal and further ensure the accuracy of data receiving.
Preferably, step S104 may include the steps of: and performing Fast Fourier Transform (FFT) on a second sampling point obtained by sampling the data at the second sampling rate.
Preferably, step S102 may include the steps of: and before the digital signal is subjected to the last downsampling by using the second sampling rate, discarding a part of the first sampling point of the cyclic prefix according to the ratio of the first sampling rate to the second sampling rate.
In this embodiment, the down-sampling operation may be performed several times during the process from the time the receiver receives the signal to the time the receiver obtains the frequency domain data. In order to achieve the purpose of completely removing the cyclic prefix, it is only required to ensure that the number of sampling points of the cyclic prefix after the last downsampling operation is an integer. That is, discarding a portion of the first sample point of the cyclic prefix is performed prior to the last downsampling.
For example, 4 downsampling operations are performed in the preprocessing process of the signal, after the 3rd sampling, the first sampling point of the cyclic prefix is obtained, and before the 4 th sampling, a part of the first sampling point of the cyclic prefix is discarded.
Fig. 2 is a schematic structural diagram of a time domain signal preprocessing apparatus according to an embodiment of the present invention.
The time domain signal preprocessing apparatus 20 shown in fig. 2 may be used in a receiver, and the time domain signal preprocessing apparatus 20 may include a transform module 201, a preprocessing module 202, a removal module 203, and a time-frequency transform module 204.
The conversion module 201 is adapted to perform analog-to-digital conversion on a received signal to obtain a digital signal, where the received signal includes a cyclic prefix and data, and the digital signal includes a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate;
the preprocessing module 202 is adapted to discard a portion of the first sample point of the cyclic prefix according to a ratio of the first sample rate to the second sample rate before downsampling the digital signal with the second sample rate;
the removing module 203 is adapted to perform downsampling on the digital signal after the discarding operation by using the second sampling rate, and remove a second sampling point obtained by downsampling the cyclic prefix at the second sampling rate;
the time-frequency transform module 204 is adapted to perform time-frequency transform on the signal without the cyclic prefix to obtain frequency domain data.
According to the embodiment of the invention, a part of the first sampling points of the cyclic prefix is discarded according to the proportion of the first sampling rate and the second sampling rate, so that after the digital signal is downsampled by using the second sampling rate, the number of the obtained second sampling points is an integer, all the second sampling points of the cyclic prefix can be removed, the frequency domain data obtained through time-frequency conversion is ensured to be the data part of the digital signal, and the accuracy of data receiving is ensured. Furthermore, the second sampling rate can meet the Nyquist sampling theorem through the technical scheme of the invention, and a smaller sampling rate can be adopted before the cyclic prefix is removed, so that the clock frequency of the digital front end is greatly reduced, and the power consumption of the receiver is reduced.
Preferably, the pre-processing module 202 may comprise a first pre-processing unit 2021, the first pre-processing unit 2021 being adapted to drop a portion of the first sampling points of the cyclic prefix before filtering the digital signal, such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
Preferably, the pre-processing module 202 may comprise a second pre-processing unit 2022, the second pre-processing unit 2022 being adapted to drop a portion of the first sampling points of the cyclic prefix after filtering the digital signal, such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
Preferably, the time-frequency transform module 204 performs FFT on a second sampling point obtained by sampling the data at the second sampling rate.
Preferably, the preprocessing module 202 discards a portion of the first sample point of the cyclic prefix according to a ratio of the first sample rate to the second sample rate before the digital signal is last downsampled using the second sample rate.
For more details of the operation principle and the operation mode of the time domain signal preprocessing device 20, reference may be made to the description of the embodiment shown in fig. 1, and details are not repeated here.
Fig. 3 is a schematic structural diagram of a receiver according to an embodiment of the present invention.
As shown in fig. 3, the general structure of the system receiver based on Orthogonal Frequency Division Multiplexing (OFDM) is as follows,
the radio frequency receiver 301 receives an analog signal. An Analog-to-Digital Converter (ADC) 302 converts an Analog signal into a Digital signal at a sampling rate Fs ═ X × 1.92 MHz. A Numerically Controlled Oscillator (NCO) 303 receives the converted digital signal and generates corresponding quadrature sine and cosine samples.
In a specific application scenario, the sampling rate needs to be reduced to 1.92MHz, so that X-fold down-sampling of the digital signal can be realized by configuring the digital filter chain 304 to achieve a sampling rate of 1.92 MHz.
In one embodiment of the present invention, the receiver may further include a missing sample module 311, a digital filter 312, a down-sampling module 313, a CP removing module 314, and an FFT module 315. After the first sampling rate reaches 1.92MHz, the sample loss module 311 loses a portion of the first sample point according to a ratio of the first sampling rate to the second sampling rate. After the remaining digital signals have passed through the digital filter 312, they are down-sampled by the down-sampling module 313 to a second sampling rate Fs of 480 KHz. The CP removing module 314 removes the second sample point of the cyclic prefix, and the second sample point of the remaining data is transmitted to the FFT module 315 to be converted into frequency domain data.
In another embodiment of the present invention, the receiver may further include a digital filter 316, a missing samples module 317, a down-sampling module 318, a CP removal module 319, and an FFT module 320. Unlike the previous embodiment, the missing sample module 317 is located at the subsequent step of the digital filter 316, i.e. the digital filter 316 performs digital filtering first, and the missing sample module 317 performs the missing sample operation.
In yet another embodiment of the present invention, the receiver may further include a digital filter 305, a down-sampling module 306, a de-CP module 307, an FFT module 308, and a phase compensation module 309. In this embodiment, after the first sampling rate reaches 1.92MHz, the digital signal passes through the digital filter 305, and the down-sampling module 306 down-samples the digital signal to reach the second sampling rate Fs of 480 KHz. The CP removing module 307 removes the second sample point of the cyclic prefix, and the remaining second sample point is transmitted to the FFT module 308 to be converted into frequency domain data. In this embodiment, after passing through the downsampling module 306, the number of the second sampling points of the cyclic prefix is a non-integer, for example, at a sampling rate of 1.92MHz, the number of the first sampling points of the cyclic prefix is 10, and after passing through the downsampling module 306, the number of the second sampling points of the cyclic prefix is 2.5. At this time, the CP removing module 307 can only remove 2 second sampling points of the cyclic prefix, and 0.5 sampling points remain; after passing through the FFT module 308, the initial phase of the frequency domain signal of each symbol is not aligned, and therefore, the phase compensation module 309 is required to compensate the initial phase of the frequency domain signal so that the initial phase of the frequency domain signal of each symbol is aligned.
In a specific implementation, the phase compensation module 309 may calculate the phase compensation factor by using the following formula:
where i is a complex factor, K is a subcarrier index, fsFor the purpose of the second sampling rate, the first sampling rate,
for the end position of the cyclic prefix at the second sampling rate,
n is a symbol number, and n is a symbol number,
represents the time length, T, corresponding to the cyclic prefix of the symbol jsIs the sample duration at the first sample rate. And multiplying the phase compensation factor by the frequency domain signal to obtain a final frequency domain signal for channel estimation.
It should be noted that, as shown in fig. 3, the modules shown by reference numerals 1, 2 and 3 may be alternatively configured in the receiver, but not necessarily all configured in the receiver.
The embodiment of the invention also discloses a readable storage medium, on which computer instructions are stored, and when the computer instructions are executed, the steps of the time domain signal preprocessing method shown in fig. 1 can be executed. The storage medium may include ROM, RAM, magnetic or optical disks, etc.
The embodiment of the invention also discloses a receiver which can comprise a memory and a processor, wherein the memory stores computer instructions capable of running on the processor. The processor, when executing the computer instructions, may perform the steps of the time domain signal pre-processing method shown in fig. 1.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (14)
1. A time domain signal preprocessing method for a receiver, comprising:
performing analog-to-digital conversion on a received signal to obtain a digital signal, wherein the received signal comprises a cyclic prefix and data, and the digital signal comprises a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate; before the digital signal is downsampled by using a second sampling rate, part of a first sampling point of the cyclic prefix is discarded according to the proportion of the first sampling rate and the second sampling rate, so that the number of the first sampling points of the cyclic prefix after the discarding operation is integral multiple of the proportion;
utilizing the second sampling rate to carry out down-sampling on the digital signal after the dropping operation, and removing a second sampling point obtained by the down-sampling of the cyclic prefix at the second sampling rate;
and performing time-frequency transformation on the signal without the cyclic prefix to obtain frequency domain data.
2. The method of time-domain signal pre-processing of claim 1, wherein discarding a portion of a first sample point of the cyclic prefix according to a ratio of the first sample rate to the second sample rate comprises:
dropping a portion of the first sampling points of the cyclic prefix prior to filtering the digital signal such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
3. The method of time-domain signal pre-processing of claim 1, wherein discarding a portion of a first sample point of the cyclic prefix according to a ratio of the first sample rate to the second sample rate comprises:
after filtering the digital signal, dropping a portion of the first sampling points of the cyclic prefix such that the number of first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
4. The method of time-domain signal pre-processing according to claim 1, wherein the number of second sampling points of the cyclic prefix is an integer.
5. The time-domain signal preprocessing method according to claim 1, wherein said performing time-frequency transform on the cyclic prefix removed signal comprises:
and performing FFT (fast Fourier transform) on a second sampling point obtained by sampling the data at the second sampling rate.
6. The method of time-domain signal pre-processing of claim 1, wherein discarding a portion of a first sample point of the cyclic prefix according to a ratio of the first sample rate to the second sample rate prior to down-sampling the digital signal with the second sample rate comprises:
and before the digital signal is subjected to the last downsampling by using the second sampling rate, discarding a part of the first sampling point of the cyclic prefix according to the ratio of the first sampling rate to the second sampling rate.
7. A time domain signal preprocessing apparatus for a receiver, comprising:
the digital signal processing device comprises a conversion module, a processing module and a processing module, wherein the conversion module is suitable for carrying out analog-to-digital conversion on a received signal to obtain a digital signal, the received signal comprises a cyclic prefix and data, and the digital signal comprises a first sampling point obtained by sampling the cyclic prefix at a first sampling rate and a first sampling point obtained by sampling the data at the first sampling rate;
the preprocessing module is suitable for discarding a part of the first sampling points of the cyclic prefix according to the proportion of the first sampling rate and the second sampling rate before the digital signal is downsampled by using the second sampling rate, so that the number of the first sampling points of the cyclic prefix after discarding operation is integral multiple of the proportion;
the removal module is suitable for utilizing the second sampling rate to carry out down-sampling on the digital signal after the removal operation and removing a second sampling point obtained by the down-sampling of the cyclic prefix at the second sampling rate; and the time-frequency transformation module is suitable for performing time-frequency transformation on the signal without the cyclic prefix so as to obtain frequency domain data.
8. The time-domain signal pre-processing apparatus of claim 7, wherein the pre-processing module comprises:
a first pre-processing unit adapted to drop a portion of the first sampling points of the cyclic prefix before filtering the digital signal, such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
9. The time-domain signal pre-processing apparatus of claim 7, wherein the pre-processing module comprises:
a second preprocessing unit adapted to drop a portion of the first sampling points of the cyclic prefix after filtering the digital signal, such that the number of the first sampling points of the cyclic prefix after dropping is an integer multiple of the ratio.
10. The time-domain signal preprocessing apparatus of claim 7, wherein the number of second sampling points of the cyclic prefix is an integer.
11. The apparatus of claim 7, wherein the time-frequency transform module performs an FFT on a second sample point obtained by sampling the data at the second sampling rate.
12. The time-domain signal pre-processing apparatus of claim 7, wherein the pre-processing module discards a portion of the first sample point of the cyclic prefix according to a ratio of the first sample rate to the second sample rate before a last downsampling of the digital signal using the second sample rate.
13. A readable storage medium having stored thereon computer instructions, wherein the computer instructions are executable to perform the steps of the time domain signal pre-processing method according to any one of claims 1 to 6.
14. A receiver comprising a memory and a processor, the memory having stored thereon computer instructions executable on the processor, wherein the processor, when executing the computer instructions, performs the steps of the time domain signal pre-processing method of any one of claims 1 to 6.
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| US9313078B1 (en) * | 2015-04-09 | 2016-04-12 | Xilinx, Inc. | Pulse cancellation crest factor reduction with a low sampling rate |
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