CN117336133A - Low-complexity OFDM (orthogonal frequency division multiplexing) cyclic prefix removing method and device - Google Patents
Low-complexity OFDM (orthogonal frequency division multiplexing) cyclic prefix removing method and device Download PDFInfo
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- CN117336133A CN117336133A CN202311387901.6A CN202311387901A CN117336133A CN 117336133 A CN117336133 A CN 117336133A CN 202311387901 A CN202311387901 A CN 202311387901A CN 117336133 A CN117336133 A CN 117336133A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2691—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation involving interference determination or cancellation
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Abstract
The invention relates to a low-complexity OFDM cyclic prefix removal method and a device, wherein the method comprises the following steps: acquiring time domain data, wherein the time domain data comprises a cyclic prefix data part and a symbol data part; determining preset sampling points, and copying data parts with the number of the later preset sampling points in the cyclic prefix data parts; placing the copied data part behind the symbol data part to obtain adjusted time domain data; and performing cyclic prefix removal processing on the adjusted time domain data. The invention can omit the operation of time offset recovery, and save the complexity of system realization.
Description
Technical Field
The present invention relates to the field of wireless communications technologies, and in particular, to a method and apparatus for removing cyclic prefix in low complexity OFDM.
Background
In the existing 5G communication protocol, in the LowPHY processing of the receiving end, for the time domain signal, a cyclic prefix portion in the time domain signal needs to be removed, and a symbol portion is reserved for later processing (phase compensation, FFT, etc.), so that FFT windowing is involved.
When the cyclic prefix is removed, if the windowing position is not suitable, channel interference ICI and intersymbol interference ISI (such as a case of CaseIII and CaseIV in fig. 1) are introduced, caseI is an ideal windowing case, and protection windowing is generally performed for insurance, such as CaseII shown in fig. 1, so that only phase rotation is introduced, and channel interference ICI and intersymbol interference ISI are not introduced. This is the current mainstream windowed approach to cyclic prefix removal. In fig. 1, TG is a cyclic prefix length, tsub is the FFT point number; shading τ for cyclic prefix labeling max I.e. the maximum delay spread.
The caseII windowing is performed as follows, a windowing offset rcp is artificially introduced, and then an FFT window of symbol data points is obtained, and since caseII windowing is equivalent to introducing a phase rotation in the frequency domain, delay compensation is required after FFT (if delay compensation is not performed, residual time offset can cause error in time domain interpolation of channel estimation, thereby affecting channel equalization and causing performance impairment).
The delay compensation formula is as follows, k being the subcarrier index within the current symbol.
It can be seen that the prior art scheme performs complex time offset recovery operation after FFT, and generally reduces the operation amountMaking register values for storage, N is introduced FFT The registers store values, thus consuming RAM resources.
Disclosure of Invention
The invention aims to solve the technical problem of providing a low-complexity OFDM cyclic prefix removing method and device, which can save time offset recovery operation and reduce system implementation complexity.
The technical scheme adopted for solving the technical problems is as follows: there is provided a low complexity OFDM cyclic prefix removal method comprising the steps of:
acquiring time domain data, wherein the time domain data comprises a cyclic prefix data part and a symbol data part;
determining preset sampling points, and copying data parts with the number of the later preset sampling points in the cyclic prefix data parts;
placing the copied data part behind the symbol data part to obtain adjusted time domain data;
and performing cyclic prefix removal processing on the adjusted time domain data.
The number of the preset sampling points is the same as the window offset introduced in the cyclic prefix removal process.
After the cyclic prefix removal processing is performed on the adjusted time domain data, the method further comprises the following steps:
performing phase compensation on the time domain data subjected to cyclic prefix removal;
the phase-compensated time domain data is converted into frequency domain data.
The technical scheme adopted for solving the technical problems is as follows: there is provided a low complexity OFDM de-cyclic prefix apparatus comprising:
an acquisition module, configured to acquire time domain data, where the time domain data includes a cyclic prefix data portion and a symbol data portion;
the copying module is used for determining preset sampling points and copying data parts with the number of the later preset sampling points in the cyclic prefix data parts;
an expansion module, configured to place the copied data portion behind the symbol data portion, to obtain adjusted time domain data;
and the processing module is used for carrying out cyclic prefix removal processing on the adjusted time domain data.
The number of the preset sampling points is the same as the window offset introduced in the cyclic prefix removal process.
The low complexity OFDM cyclic prefix removal device further comprises:
the phase compensation module is used for carrying out phase compensation on the time domain data subjected to the cyclic prefix removal treatment;
and the transformation module is used for converting the time domain data after phase compensation into frequency domain data.
Advantageous effects
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects: the invention puts the window offset part in the cyclic prefix behind the symbol data, and the offset part is the duplication of the symbol data, so the present cyclic prefix removing scheme can be adopted, the offset part in the cyclic prefix is reserved, thereby avoiding the interference ICI of channels and the interference ISI between symbols, and meanwhile, the frequency domain phase rotation caused by the time sample point offset does not exist, so the time offset recovery behind FFT is not needed, and the realization complexity of CP removing is greatly reduced.
Drawings
FIG. 1 is a prior art window diagram when cyclic prefix is removed;
fig. 2 is a flowchart of a low complexity OFDM de-cyclic prefix method of a first embodiment of the present invention;
FIG. 3 is a schematic diagram of time domain data processing in a first embodiment of the present invention;
FIG. 4 is a block diagram of a prior art 5GNR LowPHY system;
fig. 5 is a block diagram of a 5GNR LowPHY system employing the first embodiment of the present invention.
Detailed Description
The invention will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. Further, it is understood that various changes and modifications may be made by those skilled in the art after reading the teachings of the present invention, and such equivalents are intended to fall within the scope of the claims appended hereto.
A first embodiment of the present invention relates to a low complexity OFDM cyclic prefix removal method, as shown in fig. 2, comprising the steps of:
step 1, obtaining time domain data, wherein the time domain data comprises a cyclic prefix data part Ncp and a symbol data part Nsymb.
And 2, determining preset sampling points, and copying the data parts with the number of the later preset sampling points in the cyclic prefix data parts. In this step, the number of predetermined sampling points is determined to be the same as the window offset rcp introduced during the cyclic prefix removal process.
And 3, placing the copied data part behind the symbol data part to obtain the adjusted time domain data.
The processing part of the above steps 2 and 3 can be seen in fig. 3, by placing part of the data in the cyclic prefix data portion Ncp behind the symbol data portion Nsymb, i.e. copying the data portion 2 of the number rcp of preset sampling points behind the cyclic prefix data portion Ncp behind the symbol data portion Nsymb 1, since the copied data portion 2 in the cyclic prefix data portion Ncp is itself a copy of the symbol data portion Nsymb 1, the modified time domain data can still use the existing cyclic prefix removal scheme.
And 4, performing cyclic prefix removal processing on the adjusted time domain data, namely performing cyclic prefix removal in a CaseII windowing mode in the background technology of the application.
After the cyclic prefix removal process is completed, phase compensation can be performed on the time domain data after the cyclic prefix removal process, and the time domain data after the phase compensation can be converted into frequency domain data.
Fig. 4 is a block diagram of a 5G NR LowPHY system according to the prior art, and fig. 5 is a block diagram of a 5G NR LowPHY system according to a first embodiment of the present invention. As can be seen from comparison, due to the adoption of the low-complexity CP removal scheme, the time bias recovery operation can be omitted by adopting the architecture scheme of the 5G NR LowPHY system in the embodiment, so that the implementation complexity of the system can be greatly reduced.
It is not difficult to find that the time domain data processing in this embodiment can play a role in protecting windowing, and this way reserves a windowing offset part in the cyclic prefix, so as to avoid channel interference ICI and inter-symbol interference ISI, and meanwhile, there is no frequency domain phase rotation caused by time sample offset, so that time offset recovery is not needed after FFT, and the implementation complexity of CP removal is greatly reduced.
A second embodiment of the present invention relates to a low complexity OFDM cyclic prefix apparatus comprising:
an acquisition module, configured to acquire time domain data, where the time domain data includes a cyclic prefix data portion and a symbol data portion;
the copying module is used for determining preset sampling points and copying data parts with the number of the later preset sampling points in the cyclic prefix data parts;
an expansion module, configured to place the copied data portion behind the symbol data portion, to obtain adjusted time domain data;
and the processing module is used for carrying out cyclic prefix removal processing on the adjusted time domain data.
The number of the preset sampling points is the same as the window offset introduced in the cyclic prefix removal process.
The low complexity OFDM cyclic prefix removal device further comprises:
the phase compensation module is used for carrying out phase compensation on the time domain data subjected to the cyclic prefix removal treatment;
and the transformation module is used for converting the time domain data after phase compensation into frequency domain data.
It will be appreciated by those skilled in the art that the modules or steps of the invention described above may be implemented in a general purpose computing device, they may be concentrated on a single computing device, or distributed across a network of computing devices, they may alternatively be implemented in program code executable by computing devices, so that they may be stored in a storage device for execution by computing devices, and in some cases, the steps shown or described may be performed in a different order than that shown or described herein, or they may be separately fabricated into individual integrated circuit modules, or multiple modules or steps of them may be fabricated into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.
Claims (6)
1. A low complexity OFDM de-cyclic prefix method comprising the steps of:
acquiring time domain data, wherein the time domain data comprises a cyclic prefix data part and a symbol data part;
determining preset sampling points, and copying data parts with the number of the later preset sampling points in the cyclic prefix data parts;
placing the copied data part behind the symbol data part to obtain adjusted time domain data;
and performing cyclic prefix removal processing on the adjusted time domain data.
2. The low complexity OFDM de-cyclic prefix method of claim 1, wherein the number of pre-set sample points is the same as the window offset introduced during the de-cyclic prefix process.
3. The low complexity OFDM de-cyclic prefix method of claim 1, wherein after said performing the de-cyclic prefix processing on the adjusted time domain data, further comprising:
performing phase compensation on the time domain data subjected to cyclic prefix removal;
the phase-compensated time domain data is converted into frequency domain data.
4. A low complexity OFDM de-cyclic prefix apparatus comprising:
an acquisition module, configured to acquire time domain data, where the time domain data includes a cyclic prefix data portion and a symbol data portion; the copying module is used for determining preset sampling points and copying data parts with the number of the later preset sampling points in the cyclic prefix data parts;
an expansion module, configured to place the copied data portion behind the symbol data portion, to obtain adjusted time domain data;
and the processing module is used for carrying out cyclic prefix removal processing on the adjusted time domain data.
5. The low complexity OFDM de-cyclic prefix apparatus of claim 4, wherein the number of pre-set sample points is the same as the window offset introduced during the de-cyclic prefix processing.
6. The low complexity OFDM de-cyclic prefix device of claim 4, further comprising:
the phase compensation module is used for carrying out phase compensation on the time domain data subjected to the cyclic prefix removal treatment;
and the transformation module is used for converting the time domain data after phase compensation into frequency domain data.
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