CN109639614B - System and method for vector magnitude error measurement for NB _ IoT broadcast channel - Google Patents

System and method for vector magnitude error measurement for NB _ IoT broadcast channel Download PDF

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CN109639614B
CN109639614B CN201811466220.8A CN201811466220A CN109639614B CN 109639614 B CN109639614 B CN 109639614B CN 201811466220 A CN201811466220 A CN 201811466220A CN 109639614 B CN109639614 B CN 109639614B
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CN109639614A (en
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王志
陈向民
陈爽
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Transcom Shanghai Technologies Co Ltd
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Shanghai TransCom Instruments Co Ltd
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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
    • H04L27/2657—Carrier synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • 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
    • H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
    • 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
    • H04L27/2668—Details of algorithms
    • H04L27/2669—Details of algorithms characterised by the domain of operation
    • H04L27/2672—Frequency domain
    • 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
    • H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

Abstract

The invention relates to a system for measuring vector magnitude errors aiming at an NB _ IoT broadcast channel, which comprises a signal extraction module, a vector magnitude error measurement module and a vector magnitude error measurement module, wherein the signal extraction module is used for extracting and converting an initial signal; the positioning calibration module is connected with the signal extraction module and used for determining the synchronous position of a wireless frame for the processed data; and the calculation processing module is connected with the positioning calibration module and used for carrying out Fourier transform on the data and calculating the vector amplitude error according to the reference signal and the measurement signal of the narrow-band broadcast channel. The invention also relates to a method for implementing vector magnitude error measurement for NB _ IoT broadcast channels. By adopting the system and the method, the anti-interference capability of signal demodulation is effectively improved by combining the accurate calibration of frequency domain and time domain frequency offset and the efficient phase error calibration, the performance of EVM calculation is improved, and meanwhile, the reference vector is constructed in a judgment mode, so that the complexity of operation is reduced, and the measurement precision of vector amplitude error is improved.

Description

System and method for vector magnitude error measurement for NB _ IoT broadcast channel
Technical Field
The invention relates to the field of mobile communication, in particular to the field of mobile communication base station fault detection, and specifically relates to a system and a method for vector magnitude error measurement aiming at an NB _ IoT broadcast channel.
Background
With the continuous and deep development of NB-IoT technology, the NB-IoT technology is mature, the operators are networked on a large scale, and NB-IoT signal analysis testing equipment is widely concerned by the industry as a key component of the industry chain. As an important guarantee for research and development and production of base stations and terminals, NB-IoT signal analysis and test instruments play an increasingly important role. The NB-IoT signal analysis meter plays an increasingly important role as an important link of base station and terminal research and development production.
For NB-IoT signal analysis, a conventional method usually adopts a primary offset calibration, and an original code stream of a broadcast channel is calibrated in a reference vector constructing manner, which may cause the frequency offset in the signal to be not calibrated to the maximum extent, resulting in inaccurate vector magnitude error calculation; meanwhile, the original code stream is demodulated, and a reference vector is constructed, so that the link of data processing is increased, the complexity is improved, and the operation efficiency is reduced. The invention provides a vector magnitude error measuring method and device of an NB _ IoT broadcast channel, which effectively improve the anti-interference capability of signal demodulation and the performance of EVM (vector magnitude of error) calculation by combining the accurate calibration of frequency domain and time domain frequency offset and the high-efficiency phase error calibration, and simultaneously construct a reference vector in a judging mode, thereby not only reducing the complexity of operation, accelerating the calculation speed and improving the measurement precision of the vector magnitude error.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a system and a method for vector magnitude error measurement aiming at an NB _ IoT broadcast channel, which have the advantages of anti-interference capability, high calculation speed and high measurement precision.
In order to achieve the above object, the system and method for vector magnitude error measurement for NB _ IoT broadcast channel of the present invention are as follows:
the system for measuring the vector magnitude error aiming at the NB _ IoT broadcast channel is mainly characterized by comprising the following steps:
the signal extraction module is used for extracting and converting the initial signal;
the positioning calibration module is connected with the signal extraction module and used for determining the synchronous position of a wireless frame for the processed data;
and the calculation processing module is connected with the positioning calibration module and used for carrying out Fourier transform on the data and calculating the vector amplitude error according to the reference signal and the measurement signal of the narrow-band broadcast channel.
Preferably, the signal extraction module includes:
the signal receiving and processing unit is used for carrying out frequency conversion processing on the received radio frequency signal and carrying out A/D conversion processing;
and the I/Q data extraction unit is connected with the signal receiving and processing unit and is used for extracting the data of 3 wireless frames from the data after A/D sampling.
Preferably, the signal extraction module includes a signal receiving and processing unit and an I/Q data extraction unit, and the positioning calibration module includes:
the wireless frame initial position initial positioning unit is connected with the I/Q data extraction unit and used for generating 11 groups of 128-point time domain signals through a local frequency domain sequence of the narrow-band main synchronizing signal, acquiring a correlation peak and judging the initial position of the wireless frame according to the resource mapping grid;
the integral frequency offset calibration unit is connected with the wireless frame initial position initial positioning unit and used for judging the synchronous position offset according to the narrowband master synchronous signal and calculating the integral frequency offset;
and the radio frame initial position accurate positioning unit is connected with the integer frequency offset calibration unit and used for determining sampling points of the received data after the integer frequency offset is calibrated in the integer frequency offset calibration unit, acquiring correlation values and determining the accurate synchronous position of the radio frame.
Preferably, the positioning calibration module includes a radio frame initial position initial positioning unit, an integer frequency offset calibration unit and a radio frame initial position fine determination unit, and the calculation processing module includes:
a unit for removing the cyclic prefix, which is connected with the unit for accurately positioning the initial position of the wireless frame and is used for removing the cyclic prefix according to the accurate synchronous position of the wireless frame;
the Fourier transform unit is connected with the cyclic prefix removing unit and used for carrying out Fourier transform according to the data from which the cyclic prefix is removed and extracting frequency domain data;
the channel estimation equalization unit is connected with the Fourier transform unit and used for solving the channel impact response in the signal transmission process and reconstructing a reference vector;
and the vector amplitude error calculation unit is connected with the channel estimation equalization unit and used for extracting the complex-valued symbols of the narrow-band broadcast channel to generate a reference broadcast channel to obtain a measurement signal and calculating a vector amplitude error according to the reference signal and the measurement signal of the narrow-band broadcast channel.
Preferably, the calculation processing module calculates the vector magnitude error according to the narrowband broadcast channel reference signal and the measurement signal, specifically:
the vector magnitude error is calculated according to the following equation:
Figure BDA0001889869940000031
EVM is vector amplitude error, meas (d) is measurement vector, ref (d) is reference vector, and d is the number of subcarriers allocated to a radio frame by the narrowband broadcast channel.
Preferably, the length of the sampling point of the radio frame starting position precise bit position is 128 × 11+2 × N, where N is the number of points shifted forward relative to the mapping position.
The method for realizing vector magnitude error measurement aiming at the NB _ IoT broadcast channel based on the system is mainly characterized in that the signal extraction module comprises a signal receiving and processing unit and an I/Q data extraction unit, the positioning and calibration module comprises a wireless frame initial position initial positioning unit, an integer frequency offset calibration unit and a wireless frame initial position precise determination unit, the calculation and processing module comprises a cyclic prefix removing unit, a Fourier transform unit, a channel estimation and equalization unit and a vector magnitude error calculation unit, and the method comprises the following steps:
(1) the signal receiving and processing unit samples by a sampling clock, and the I/Q data extraction unit extracts data of 3 wireless frames;
(2) the wireless frame initial position initial positioning unit generates a time domain signal, acquires a correlation peak and determines a wireless frame initial position;
(3) the integer frequency deviation calibration unit calculates the synchronous position deviation delta d according to the narrow-band main synchronous signal and calculates the integer frequency deviation delta fIn；
(4) The radio frame initial position precise determination bit unit determines an initial position, obtains a correlation value according to narrowband auxiliary synchronization signal time domain data, and determines a precise synchronization position;
(5) calculating decimal frequency deviation delta f according to cyclic prefix and narrow-band auxiliary synchronous signalde；
(6) And removing the cyclic prefix, performing Fourier forward transform to generate a narrowband broadcast channel reference signal, and calculating to obtain a vector amplitude error according to the narrowband broadcast channel reference signal and the measurement signal.
Preferably, the clock rate of the sampling clock in step (1) is 1.92 Mbps.
Preferably, the 3 radio frames in step (1) have a total length of 30ms, and the data length of the radio frame is 57600.
Preferably, the step (2) specifically comprises the following steps:
(2.1) performing inverse Fourier transform on the local frequency domain sequence of the narrowband main synchronous signal to generate 11 groups of 128-point time domain signals;
(2.2) carrying out sliding correlation according to the data received and extracted in the step (1) to obtain a correlation peak and an initial position of a narrow-band main synchronization signal;
and (2.3) determining the initial synchronization position of the wireless frame according to the resource mapping structure of the 3GPP protocol.
Preferably, the initial position of the narrowband primary synchronization signal in step (2.2) is the position of the maximum value of the correlation peak in the received data.
Preferably, the step (3) specifically includes the following steps:
(3.1) carrying out Fourier transform according to 2048 point data of the initial position of the narrow-band main synchronization signal extracted in the step (2), and converting the data into a frequency domain;
(3.2) extracting frequency domain data on one resource block of the narrow-band main synchronizing signal, and calculating a synchronizing position deviation delta d;
(3.3) calculating integer frequency offset of signal Δ f according to sub-carrier bandwidth of NB-IoTIn。
Preferably, the calculating the integer frequency offset of the signal specifically includes:
calculating integral frequency deviation delta f of signal according to the following formulaIn：
ΔfIn＝Δd*15kHz；
Where Δ d is the synchronization position offset, and the sub-carrier bandwidth of NB-IoT is 15 KH.
Preferably, the step (4) specifically includes the following steps:
(4.1) removing the phase offset according to the data extracted by receiving in (1);
(4.2) determining an initial position, and acquiring a correlation value according to the narrowband auxiliary synchronization signal time domain data;
and (4.3) determining the precise synchronous position of the wireless frame according to the 3GPP protocol.
Preferably, the starting position in step (4.2) is the number of points shifted forward from the mapping position, and the length is 128 × 11+2 × N sampling points.
Preferably, the step (6) specifically includes the following steps:
(6.1) the unit for removing cyclic prefix removes cyclic prefix according to the fine synchronization position of the radio frame;
(6.2) the Fourier transform unit performs Fourier transform according to the data without the cyclic prefix and extracts frequency domain data;
(6.3) the vector magnitude error calculation unit extracts the complex value symbol of the narrow-band broadcast channel to generate a reference broadcast channel, obtains a measurement signal, and calculates the vector magnitude error according to the narrow-band broadcast channel reference signal and the measurement signal.
Preferably, the calculating and processing module in step (6.3) calculates the vector magnitude error according to the narrowband broadcast channel reference signal and the measurement signal, specifically:
the vector magnitude error is calculated according to the following equation:
Figure BDA0001889869940000041
EVM is vector amplitude error, meas (d) is measurement vector, ref (d) is reference vector, and d is the number of subcarriers allocated to a radio frame by the narrowband broadcast channel.
By adopting the system and the method for measuring the vector magnitude error aiming at the NB _ IoT broadcast channel, the anti-interference capability of signal demodulation is effectively improved by combining the accurate calibration of frequency domain and time domain frequency deviation and the high-efficiency phase error calibration, the performance of EVM (vector magnitude of error) calculation is improved, and meanwhile, the reference vector is constructed in a judgment mode, so that the complexity of operation is reduced, the calculation speed is accelerated, and the measurement precision of the vector magnitude error is improved. The method can be effectively applied to vector magnitude error index analysis of the NB-IoT signals.
Drawings
Fig. 1 is a schematic block diagram of the system of the present invention for vector magnitude error measurement for NB _ IoT broadcast channels.
FIG. 2 is a diagram of the NPBCH vector magnitude error measurement results of the method of the present invention for implementing vector magnitude error measurement for NB _ IoT broadcast channels.
Detailed Description
In order to more clearly describe the technical contents of the present invention, the following further description is given in conjunction with specific embodiments.
The system for vector magnitude error measurement for NB _ IoT broadcast channels, wherein the system comprises:
the signal extraction module is used for extracting and converting the initial signal;
the positioning calibration module is connected with the signal extraction module and used for determining the synchronous position of a wireless frame for the processed data;
and the calculation processing module is connected with the positioning calibration module and used for carrying out Fourier transform on the data and calculating the vector amplitude error according to the reference signal and the measurement signal of the narrow-band broadcast channel.
Preferably, the signal extraction module includes:
the signal receiving and processing unit is used for carrying out frequency conversion processing on the received radio frequency signal and carrying out A/D conversion processing;
and the I/Q data extraction unit is connected with the signal receiving and processing unit and is used for extracting the data of 3 wireless frames from the data after A/D sampling.
As a preferred embodiment of the present invention, the signal extraction module includes a signal receiving processing unit and an I/Q data extraction unit, and the positioning calibration module includes:
the wireless frame initial position initial positioning unit is connected with the I/Q data extraction unit and used for generating 11 groups of 128-point time domain signals through a local frequency domain sequence of the narrow-band main synchronizing signal, acquiring a correlation peak and judging the initial position of the wireless frame according to the resource mapping grid;
the integral frequency offset calibration unit is connected with the wireless frame initial position initial positioning unit and used for judging the synchronous position offset according to the narrowband master synchronous signal and calculating the integral frequency offset;
and the radio frame initial position accurate positioning unit is connected with the integer frequency offset calibration unit and used for determining sampling points of the received data after the integer frequency offset is calibrated in the integer frequency offset calibration unit, acquiring correlation values and determining the accurate synchronous position of the radio frame.
As a preferred embodiment of the present invention, the positioning calibration module includes a radio frame initial position initial positioning unit, an integer multiple frequency offset calibration unit, and a radio frame initial position fine determination unit, and the calculation processing module includes:
a unit for removing the cyclic prefix, which is connected with the unit for accurately positioning the initial position of the wireless frame and is used for removing the cyclic prefix according to the accurate synchronous position of the wireless frame;
the Fourier transform unit is connected with the cyclic prefix removing unit and used for carrying out Fourier transform according to the data from which the cyclic prefix is removed and extracting frequency domain data;
the channel estimation equalization unit is connected with the Fourier transform unit and used for solving the channel impact response in the signal transmission process and reconstructing a reference vector;
and the vector amplitude error calculation unit is connected with the channel estimation equalization unit and used for extracting the complex-valued symbols of the narrow-band broadcast channel to generate a reference broadcast channel to obtain a measurement signal and calculating a vector amplitude error according to the reference signal and the measurement signal of the narrow-band broadcast channel.
As a preferred embodiment of the present invention, the calculating and processing module calculates a vector magnitude error according to a narrowband broadcast channel reference signal and a measurement signal, specifically:
the vector magnitude error is calculated according to the following equation:
Figure BDA0001889869940000061
EVM is vector amplitude error, meas (d) is measurement vector, ref (d) is reference vector, and d is the number of subcarriers allocated to a radio frame by the narrowband broadcast channel.
In a preferred embodiment of the present invention, the length of the sampling point of the fine positioning unit at the starting position of the wireless frame is 128 × 11+2 × N, where N is the number of points shifted forward relative to the mapping position.
The method for realizing vector magnitude error measurement aiming at the NB _ IoT broadcast channel based on the system is mainly characterized in that the signal extraction module comprises a signal receiving and processing unit and an I/Q data extraction unit, the positioning and calibration module comprises a wireless frame initial position initial positioning unit, an integer frequency offset calibration unit and a wireless frame initial position precise determination unit, the calculation and processing module comprises a cyclic prefix removing unit, a Fourier transform unit, a channel estimation and equalization unit and a vector magnitude error calculation unit, and the method comprises the following steps:
(1) the signal receiving and processing unit samples by a sampling clock, and the I/Q data extraction unit extracts data of 3 wireless frames;
(2) the wireless frame initial position initial positioning unit generates a time domain signal, acquires a correlation peak and determines a wireless frame initial position;
(3) the integer frequency deviation calibration unit calculates the synchronous position deviation delta d according to the narrow-band main synchronous signal and calculates the integer frequency deviation delta fIn；
(4) The radio frame initial position precise determination bit unit determines an initial position, obtains a correlation value according to narrowband auxiliary synchronization signal time domain data, and determines a precise synchronization position;
(5) calculating decimal frequency deviation delta f according to cyclic prefix and narrow-band auxiliary synchronous signalde；
(6) And removing the cyclic prefix, performing Fourier forward transform to generate a narrowband broadcast channel reference signal, and calculating to obtain a vector amplitude error according to the narrowband broadcast channel reference signal and the measurement signal.
As a preferred embodiment of the present invention, the clock rate of the sampling clock in step (1) is 1.92 Mbps.
As a preferred embodiment of the present invention, the 3 radio frames in the step (1) have a total length of 30ms, and the data length of the radio frame is 57600.
As a preferred embodiment of the present invention, the step (2) specifically comprises the following steps:
(2.1) performing inverse Fourier transform on the local frequency domain sequence of the narrowband main synchronous signal to generate 11 groups of 128-point time domain signals;
(2.2) carrying out sliding correlation according to the data received and extracted in the step (1) to obtain a correlation peak and an initial position of a narrow-band main synchronization signal;
and (2.3) determining the initial synchronization position of the wireless frame according to the resource mapping structure of the 3GPP protocol.
As a preferred embodiment of the present invention, the initial position of the narrowband primary synchronization signal in step (2.2) is a position of a maximum value of a correlation peak in the received data.
As a preferred embodiment of the present invention, the step (3) specifically comprises the following steps:
(3.1) carrying out Fourier transform according to 2048 point data of the initial position of the narrow-band main synchronization signal extracted in the step (2), and converting the data into a frequency domain;
(3.2) extracting frequency domain data on one resource block of the narrow-band main synchronizing signal, and calculating a synchronizing position deviation delta d;
(3.3) calculating integer frequency offset of signal Δ f according to sub-carrier bandwidth of NB-IoTIn。
As a preferred embodiment of the present invention, the calculating the integer frequency offset of the signal specifically includes:
calculating integral frequency deviation delta f of signal according to the following formulaIn：
ΔfIn＝Δd×15kHz；
Where Δ d is the synchronization position offset, and the sub-carrier bandwidth of NB-IoT is 15 KH.
As a preferred embodiment of the present invention, the step (4) specifically comprises the following steps:
(4.1) removing the phase offset according to the data extracted by receiving in (1);
(4.2) determining an initial position, and acquiring a correlation value according to the narrowband auxiliary synchronization signal time domain data;
and (4.3) determining the precise synchronous position of the wireless frame according to the 3GPP protocol.
As a preferred embodiment of the present invention, the starting position in the step (4.2) is the number of points shifted forward from the mapping position, and the length is 128 × 11+2 × N sampling points.
As a preferred embodiment of the present invention, the step (6) specifically comprises the following steps:
(6.1) the unit for removing cyclic prefix removes cyclic prefix according to the fine synchronization position of the radio frame;
(6.2) the Fourier transform unit performs Fourier transform according to the data without the cyclic prefix and extracts frequency domain data;
(6.3) the vector magnitude error calculation unit extracts the complex value symbol of the narrow-band broadcast channel to generate a reference broadcast channel, obtains a measurement signal, and calculates the vector magnitude error according to the narrow-band broadcast channel reference signal and the measurement signal.
As a preferred embodiment of the present invention, the calculating and processing module in step (6.3) calculates a vector magnitude error according to the narrowband broadcast channel reference signal and the measurement signal, specifically:
the vector magnitude error is calculated according to the following equation:
Figure BDA0001889869940000081
EVM is vector amplitude error, meas (d) is measurement vector, ref (d) is reference vector, and d is the number of subcarriers allocated to a radio frame by the narrowband broadcast channel.
In the specific implementation manner of the invention, the invention relates to a vector magnitude error measurement method and a vector magnitude error measurement device of an NB _ IoT broadcast channel, which are used in the field of NB _ Iot wireless communication test.
The method comprises the following steps: generating a time domain signal by the local narrowband master synchronization signal frequency domain signal through IFFT (inverse Fourier transform), performing correlation by using the local narrowband master synchronization time domain signal and received data to obtain a correlation peak, and selecting a maximum point of the correlation peak to determine an initial starting position of a wireless frame; extracting narrow-band primary synchronization time domain data, converting the narrow-band primary synchronization time domain data into a frequency domain, and calibrating a frequency offset error of the integral multiple of the sub-carrier bandwidth by using the resource mapping position of a narrow-band primary synchronization signal and the correlation of the frequency domain and a local primary synchronization signal; generating a time domain signal by IFFT (inverse Fourier transform) by utilizing a local narrowband auxiliary synchronous signal frequency domain signal, and performing correlation on the local narrowband auxiliary synchronous time domain signal and received data to obtain a correlation peak so as to determine the accurate synchronous position of a wireless frame; calculating decimal frequency offset by utilizing the correlation between the cyclic prefix and the last part of sampling points on one OFDM symbol, and performing frequency offset calibration; removing CP (cyclic prefix), performing FFT (Fourier transform), extracting NPBCH (narrowband broadcast channel) complex value symbols distributed in a physical resource block, performing hard decision, and generating NPBCH (narrowband broadcast channel) reference signals; comparing the phase offset of the complex value symbol with the phase offset of the reference signal to obtain hardware phase offset, and calibrating the phase offset through phase rotation; and then the EVM is obtained through a measurement signal and a reference signal of NPBCH (narrow-band broadcast channel).
The invention effectively improves the anti-interference capability of signal demodulation and the performance of EVM (vector error magnitude) calculation by accurately positioning the initial position of the wireless frame, combining the accurate calibration of frequency domain and time domain frequency offset and the high-efficiency phase error calibration, and can be widely applied to NB-IoT vector signal analysis equipment.
The method for implementing vector magnitude error measurement for the NB _ Iot broadcast channel based on the above system is shown in fig. 1, and includes the following steps:
(1) in the signal reception processing unit, a sampling clock having a clock rate of 1.92Mbps is used to sample a received signal, and 3 radio frames of 30ms in total are extracted, with a data length of 57600.
(2) And generating a local frequency domain sequence of 121 symbols of the narrowband master synchronization signal, performing Inverse Fast Fourier Transform (IFFT) to generate 11 groups of 128-point time domain signals, performing sliding correlation on the time domain signals and the received data in the step (1) to obtain a correlation peak, and taking the position of the maximum value of the correlation peak in the received data as the initial position of the narrowband master synchronization signal. And judging the initial synchronization position of the wireless frame according to the 3GPP protocol resource mapping structure.
(3) Performing FFT (Fourier transform) by utilizing 2048 point data of the initial position of the extracted narrowband master synchronization signal in the step (2), converting the data into a frequency domain, extracting frequency domain data on one resource block of the narrowband master synchronization signal, correlating the frequency domain data with the local narrowband master synchronization signal data, and calculating the synchronous position deviation delta d, wherein the integral multiple frequency deviation delta f of the received signal can be solved because the sub-carrier bandwidth of NB-IoT is 15KHzIn＝Δd*15KHz。
(4) Multiplying each sample point data of the received data extracted in (1) by exp (-j × k × 2 × π × t)c×ΔfIn) For eliminating phase shift caused by integer multiple frequency shift, wherein j is imaginary unit of complex number; k is a serial number corresponding to the sampling point in the step (1), and k is 0, 1, 2,. and 57599; t is tcThe time interval between adjacent sampling points; Δ fInIs the integer multiple frequency offset calculated in (3).
(5) And (3) mapping the received data subjected to integer-multiple frequency offset calibration in the step (4) according to a 3GPP protocol narrowband auxiliary synchronization signal resource, taking out N points which are shifted forward relative to the mapping position and are used as initial positions, wherein the length of the sampling points is 128 multiplied by 11+2 multiplied by N, correlating the sampling points with 128 multiplied by 11 narrowband auxiliary synchronization signal time domain data of a local designated cell number and obtaining correlation values, wherein the maximum correlation value point is the initial point of the auxiliary synchronization signal, and thus the accurate synchronization position of the wireless frame is determined according to the 3GPP protocol. Where N is 10 or 20 or.. 100, the search range is selected based on signal quality.
(6) And (5) utilizing the accurate synchronization position of the wireless frame signal in the step (5) to take out two frames of received data, and utilizing the autocorrelation of the cyclic prefix in the step (5) and the last part of data of the narrow-band auxiliary synchronization signal to calculate the decimal frequency deviation delta fde。
(7) Multiplying each sample point data of the received data extracted in (6) by exp (-j × k × 2 × π × t)c×ΔfdeFor eliminating phase shift caused by decimal frequency shift, wherein j is imaginary unit of complex number; k is the serial number corresponding to the extraction sampling point in (6), and k is 0, 1, 2,. and 38399; t is tcThe time interval between adjacent sampling points; Δ fdeThe fractional frequency offset calculated in (6).
(8) And (4) removing the data with the phase error in the step (7), removing the cyclic prefix, performing fast Fourier transform, and taking out the complex-value symbol in the allocated resource block of the narrow-band broadcast channel.
(9) And (3) extracting complex value symbols of the narrow-band broadcast channel from the step (8), carrying out hard decision to generate a reference broadcast channel, taking the average value of the amplitude of the complex value symbols extracted from the step (8) as the amplitude value of a reference signal, comparing the phase of each complex value symbol in the step (8) with the phase of the reference signal, taking the average value of phase difference values of all points as a hardware phase offset, subtracting the hardware phase offset from the phase of the complex value symbol to obtain the phase of a measurement signal, obtaining the measurement signal by the phase and the amplitude of the measurement signal, and calculating a vector amplitude error according to the measurement signal and the reference signal.
2. The sampling clock of 1.92Mbps is selected in (1), because only one RB (resource block) of the NB-IOT is provided, the bandwidth is only 180KHz, the data volume of the sampling data can be reduced by adopting the low-rate clock, and the calculation speed is improved;
3. because the narrowband auxiliary synchronizing signal is mapped only on the even radio frames, 3 pieces of radio frame data are extracted in the step (1) so as to ensure that the data of a complete auxiliary synchronizing signal can be extracted from the sampling points.
4. In the step (2), the complex value symbol block after the fast Fourier transform is a matrix with the length of L and the width of f, wherein L is a matrix with the symbol length value of 1, 2., 11; f is the length of the allocated sub-carriers after fast fourier transform.
5. The narrowband broadcast channel data in (8) is a complex sequence with NB-IoT and LTE reference signals removed in each radio frame subframe 0, i.e., 3, 4.
6. The formula for calculating the vector error amplitude according to the narrowband broadcast channel reference signal and the measurement signal in (9) is as follows:
Figure BDA0001889869940000101
EVM is vector amplitude error, meas (d) is measurement vector, ref (d) is reference vector, and d is the number of subcarriers allocated to a radio frame by the narrowband broadcast channel.
7. A signal reception processing unit: the digital signal processing circuit is used for carrying out frequency conversion, filtering and conversion on a received radio frequency signal to an intermediate frequency, carrying out frequency mixing again on the intermediate frequency signal and a local oscillator signal to convert to a zero frequency, and entering an A/D (analog-to-digital converter) to convert to a digital signal.
An I/Q data extraction unit: the method is used for reducing the speed of the data after A/D sampling to 1.92Mbps and extracting the data of 3 wireless frames, and is beneficial to reducing the calculated amount and reducing the complexity of operation.
A wireless frame starting position initial positioning unit: through a local frequency domain sequence of 121 symbols of the narrowband primary synchronization signal, IFFT (inverse fourier transform) generates 11 groups of 128-point time domain signals, performs sliding correlation with received data to obtain a correlation peak, and takes the position of the maximum value of the correlation peak in the received data as the initial position of the narrowband primary synchronization signal. And judging the initial position of the radio frame according to the resource mapping grid.
An integer frequency offset calibration unit: only 11 resource units are mapped in 12 resource units in each symbol according to the narrow-band primary synchronization signal, so that the synchronization position offset is judged through correlation to calculate the integral multiple frequency offset delta fInThen, the data of each sampling point of the received data of the initial positioning unit of the wireless frame starting position is multiplied by exp (-j multiplied by k multiplied by 2 multiplied by pi multiplied by t)c×Δfde) For eliminating the decimal multipleThe frequency offset brings phase offset, k is a serial number corresponding to a sampling point in the I/Q data extraction unit, and k is 0, 1, 2. t is tcThe time interval between adjacent sampling points; Δ fInIs the calculated integer multiple frequency offset.
A precise positioning unit: the method comprises the steps of mapping positions of received data after integer frequency offset calibration in an integer frequency offset calibration unit according to 3GPP protocol narrowband auxiliary synchronous signal resources, taking out N points which are moved forward relative to the mapping positions and are used as initial positions, obtaining sampling points with the length of 128 multiplied by 11+2 multiplied by N, correlating the sampling points with 128 multiplied by 11 narrowband auxiliary synchronous signal time domain data of a local designated cell number and obtaining correlation values, wherein the maximum point of the correlation values is the initial point of an auxiliary synchronous signal, and determining the accurate synchronous position of a wireless frame according to the 3GPP protocol. Where N is 10 or 20 or.. 100, the search range is selected based on signal quality.
And a cyclic prefix removing unit: according to the precise synchronous position of the wireless frame, the cyclic prefix of 10 sampling points is removed from the symbol 0 of each time slot, and the cyclic prefix of 9 sampling points is removed from other symbols.
A Fourier transform unit: the method is used for performing 128-point Fourier transform by using data from which cyclic prefixes are removed to convert time domain data into frequency domain data, performing frequency spectrum shifting, and extracting frequency domain data of one resource block.
Channel estimation/equalization unit: the method is used for solving the channel impact response in the signal transmission process to reconstruct the reference vector.
Vector magnitude error calculation unit: the method is used for extracting complex value symbols of a narrow-band broadcast channel, carrying out hard decision, generating a reference broadcast channel, taking (the average value of the complex value symbol amplitude as the amplitude value of a reference signal, comparing the phase of each complex value symbol extracted by a Fourier transform unit with the phase of the reference signal, taking the average value of phase difference values of all points as a hardware phase offset, subtracting the hardware phase offset from the complex value symbol phase to obtain the phase of a measurement signal, obtaining the measurement signal with the phase and the amplitude of the measurement signal, and calculating a vector amplitude error according to the measurement signal and the reference signal.
By adopting the system and the method for measuring the vector magnitude error aiming at the NB _ IoT broadcast channel, the anti-interference capability of signal demodulation is effectively improved by combining the accurate calibration of frequency domain and time domain frequency deviation and the high-efficiency phase error calibration, the performance of EVM (vector magnitude of error) calculation is improved, and meanwhile, the reference vector is constructed in a judgment mode, so that the complexity of operation is reduced, the calculation speed is accelerated, and the measurement precision of the vector magnitude error is improved. The method can be effectively applied to vector magnitude error index analysis of the NB-IoT signals.
In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims (14)

1. A system for vector magnitude error measurement for NB _ IoT broadcast channels, the system comprising:
the signal extraction module is used for extracting and converting the initial signal;
the positioning calibration module is connected with the signal extraction module and used for determining the synchronous position of a wireless frame for the processed data;
the calculation processing module is connected with the positioning calibration module and used for carrying out Fourier transform on data and calculating a vector amplitude error according to a narrowband broadcast channel reference signal and a measurement signal;
the signal extraction module comprises a signal receiving and processing unit and an I/Q data extraction unit, and the positioning calibration module comprises:
the wireless frame initial position initial positioning unit is connected with the I/Q data extraction unit and used for generating 11 groups of 128-point time domain signals through a local frequency domain sequence of the narrow-band main synchronizing signal, acquiring a correlation peak and judging the initial position of the wireless frame according to the resource mapping grid;
the integral frequency offset calibration unit is connected with the wireless frame initial position initial positioning unit and used for judging the synchronous position offset according to the narrowband master synchronous signal and calculating the integral frequency offset;
the radio frame initial position accurate positioning unit is connected with the integer frequency offset calibration unit and is used for determining sampling points of the received data after the integer frequency offset is calibrated in the integer frequency offset calibration unit, acquiring correlation values and determining the accurate synchronous position of the radio frame;
the positioning calibration module comprises a wireless frame initial position initial positioning unit, an integer frequency offset calibration unit and a wireless frame initial position precise determination unit, and the calculation processing module comprises:
a unit for removing the cyclic prefix, which is connected with the unit for accurately positioning the initial position of the wireless frame and is used for removing the cyclic prefix according to the accurate synchronous position of the wireless frame;
the Fourier transform unit is connected with the cyclic prefix removing unit and used for carrying out Fourier transform according to the data from which the cyclic prefix is removed and extracting frequency domain data;
the channel estimation equalization unit is connected with the Fourier transform unit and used for solving the channel impact response in the signal transmission process and reconstructing a reference vector;
the vector amplitude error calculation unit is connected with the channel estimation equalization unit and used for extracting the complex value symbol of the narrow-band broadcast channel to generate a reference broadcast channel to obtain a measurement signal and calculating a vector amplitude error according to the reference signal and the measurement signal of the narrow-band broadcast channel;
the calculation processing module calculates the vector magnitude error according to the narrowband broadcast channel reference signal and the measurement signal, and specifically comprises:
the vector magnitude error is calculated according to the following equation:
Figure FDA0003100688260000021
EVM is vector amplitude error, meas (d) is measurement vector, ref (d) is reference vector, and d is the number of subcarriers allocated to a radio frame by the narrowband broadcast channel.
2. The system of claim 1, wherein the signal extraction module comprises:
the signal receiving and processing unit is used for carrying out frequency conversion processing on the received radio frequency signal and carrying out A/D conversion processing;
and the I/Q data extraction unit is connected with the signal receiving and processing unit and is used for extracting the data of 3 wireless frames from the data after A/D sampling.
3. The system of claim 1, wherein the length of the sampling point of the radio frame start position fine-determination bit unit is 128 x 11+2 x N, where N is a number of points that are shifted forward relative to the mapping position.
4. A method for implementing vector magnitude error measurement for NB _ IoT broadcast channel based on the system of claim 1, wherein the signal extraction module comprises a signal receiving processing unit and an I/Q data extraction unit, the positioning calibration module comprises a radio frame starting position initial positioning unit, an integer frequency offset calibration unit and a radio frame starting position fine determination unit, the calculation processing module comprises a cyclic prefix removal unit, a fourier transform unit, a channel estimation equalization unit and a vector magnitude error calculation unit, and the method comprises the following steps:
(1) the signal receiving and processing unit samples by a sampling clock, and the I/Q data extraction unit extracts data of 3 wireless frames;
(2) the wireless frame initial position initial positioning unit generates a time domain signal, acquires a correlation peak and determines a wireless frame initial position;
(3) the integer frequency deviation calibration unit calculates the synchronous position deviation delta d according to the narrow-band main synchronous signal and calculates the integer frequency deviation delta fIn；
(4) The radio frame initial position precise determination bit unit determines an initial position, obtains a correlation value according to narrowband auxiliary synchronization signal time domain data, and determines a precise synchronization position;
(5) calculating decimal frequency deviation delta f according to cyclic prefix and narrow-band auxiliary synchronous signalde；
(6) And removing the cyclic prefix, performing Fourier forward transform to generate a narrowband broadcast channel reference signal, and calculating to obtain a vector amplitude error according to the narrowband broadcast channel reference signal and the measurement signal.
5. The method of claim 4, wherein the sampling clock of step (1) has a clock rate of 1.92 Mbps.
6. The method of claim 4, wherein the 3 radio frames in step (1) have a total length of 30ms, and the data length of the radio frame is 57600.
7. The method of claim 4, wherein the step (2) comprises the following steps:
(2.1) performing inverse Fourier transform on the local frequency domain sequence of the narrowband main synchronous signal to generate 11 groups of 128-point time domain signals;
(2.2) performing sliding correlation according to the data received and extracted in the step (1) to obtain correlation peaks and initial positions of the narrowband master synchronization signals;
and (2.3) determining the initial synchronization position of the wireless frame according to the resource mapping structure of the 3GPP protocol.
8. The method of claim 7, wherein the initial position of the narrowband primary synchronization signal in step (2.2) is a position of a maximum correlation peak in the received data.
9. The method of claim 4, wherein the step (3) comprises the following steps:
(3.1) carrying out Fourier transform according to 2048 point data of the initial position of the narrow-band main synchronization signal extracted in the step (2), and converting the data into a frequency domain;
(3.2) extracting frequency domain data on one resource block of the narrow-band main synchronizing signal, and calculating a synchronizing position deviation delta d;
(3.3) calculating integer frequency offset of signal Δ f according to sub-carrier bandwidth of NB-IoTIn。
10. The method of claim 9, wherein the calculating the integer frequency offset of the signal is specifically:
calculating integral frequency deviation delta f of signal according to the following formulaIn：
ΔfIn＝Δd×15kHz；
Where Δ d is the synchronization position offset, and the sub-carrier bandwidth of NB-IoT is 15 KH.
11. The method of claim 4, wherein the step (4) comprises the following steps:
(4.1) removing the phase offset according to the data extracted by the step (1);
(4.2) determining an initial position, and acquiring a correlation value according to the narrowband auxiliary synchronization signal time domain data;
and (4.3) determining the precise synchronous position of the wireless frame according to the 3GPP protocol.
12. The method of claim 11, wherein the starting position in step (4.2) is the number of points shifted forward from the mapping position, and the length is 128 × 11+2 × N sampling points, where N is the number of points shifted forward from the mapping position, and N is 10, 20, or … 100.
13. The method of claim 4, wherein the step (6) comprises the following steps:
(6.1) the unit for removing cyclic prefix removes cyclic prefix according to the fine synchronization position of the radio frame;
(6.2) the Fourier transform unit performs Fourier transform according to the data without the cyclic prefix and extracts frequency domain data;
(6.3) the vector magnitude error calculation unit extracts the complex value symbol of the narrow-band broadcast channel to generate a reference broadcast channel, obtains a measurement signal, and calculates the vector magnitude error according to the narrow-band broadcast channel reference signal and the measurement signal.
14. The method of claim 13, wherein the computation processing module in step (6.3) computes the vector magnitude error from the narrowband broadcast channel reference signal and the measurement signal, specifically:
the vector magnitude error is calculated according to the following equation:
Figure FDA0003100688260000041
EVM is vector amplitude error, meas (d) is measurement vector, ref (d) is reference vector, and d is the number of subcarriers allocated to a radio frame by the narrowband broadcast channel.
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