CN112019300B - Signal wireless transmission method for nuclear magnetic resonance imaging equipment - Google Patents
Signal wireless transmission method for nuclear magnetic resonance imaging equipment Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
- H04L1/0013—Rate matching, e.g. puncturing or repetition of code symbols
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0041—Arrangements at the transmitter end
- H04L1/0042—Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0071—Use of interleaving
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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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention provides a method for wireless signal transmission of nuclear magnetic resonance imaging equipment, which comprises the following steps: the local coil unit receives the MR analog signals; sequentially passing through a first mixer, an analog-to-digital converter and a digital down converter to obtain an MR digital baseband signal; interleaving, rate matching and channel coding are carried out on the MR digital baseband signals, and mapping is carried out on the MR digital baseband signals to a wireless channel; after OFDM modulation is carried out on the digital signals, the digital signals are sent to a wireless air interface; the receiver receives signals from the wireless air interface and performs OFDM demodulation; performing channel decoding, de-rate matching and de-interleaving to restore an MR digital baseband signal; the MR digital baseband signal sequentially passes through a digital up-converter, a digital-to-analog conversion module and a second mixer to obtain an MR analog signal. The method provided by the invention can reduce power consumption and cost, obtain better image quality and signal-to-noise ratio, ensure the frequency spectrum utilization rate and reliability of nuclear magnetic resonance signal wireless transmission, and simultaneously enable the system to be more concise through the wireless transmission of the signals.
Description
Technical Field
The invention relates to the technical field of nuclear magnetic resonance medical imaging equipment, in particular to a method for wireless signal transmission of nuclear magnetic resonance imaging equipment.
Background
Typically, the signal transmission of the magnetic resonance apparatus is via a cable connected to the local receive coil. The distance between the cable and the patient is very short when scanning the patient, due to the limited space. This not only brings great inconvenience to doctors in placing coils; moreover, due to the antenna effect of the cable, when the carrier coil emits power, current is generated on the cable, which causes discomfort to the patient and seriously burns the patient. Furthermore, the cost of the system is also greatly increased due to the large number of cables in the coil and in the patient bed. In order to solve the problem of the cable antenna effect, the transmission of the magnetic resonance signals is realized in an optical fiber communication mode in the industry, but practice shows that the optical fiber communication scheme still brings inconvenience to doctors in using coils; but also a further increase in cost.
Disclosure of Invention
The invention provides a method for wireless transmission of nuclear magnetic resonance imaging equipment signals, which can reduce power consumption and cost, obtain better image quality and signal-to-noise ratio, ensure the frequency spectrum utilization rate and reliability of the wireless transmission of nuclear magnetic resonance signals, and simultaneously ensure that the wireless transmission of the signals can lead a system to be more concise.
The invention adopts the following technical scheme:
a method of wireless transmission of nuclear magnetic resonance imaging equipment signals, comprising:
s1, receiving an MR analog signal by a local coil unit;
s2, after the MR analog signals sequentially pass through a first mixer, an analog-to-digital converter and a digital down converter, MR digital baseband signals are obtained;
s3, the transmitter carries out interleaving, rate matching and channel coding on the MR digital baseband signal to obtain a digital signal and maps the digital signal to a wireless channel;
s4, after OFDM modulation is carried out on the digital signal by the transmitter, a microwave signal is obtained and sent to a wireless air interface;
s5, the receiver receives the microwave signal from the wireless air interface, performs OFDM demodulation and separates out the digital signal carried by the wireless channel;
s6, the receiver performs channel decoding, rate de-matching and de-interleaving on the digital signal to restore an MR digital baseband signal;
s7, the MR digital baseband signals sequentially pass through a digital up-converter, a digital-to-analog conversion module and a second mixer to obtain MR analog signals corresponding to the local coil units.
Further, the number of the local coil units is multiple, and the local coil units form a local coil unit array to receive MR analog signals; the number of the first mixers, the analog-to-digital converter, the digital down converter, the wireless channel, the digital up converter, the digital-to-analog conversion module and the second mixers is the same as the number of the local coil units.
Further, in the step S3, the transmitter interleaves the MR digital baseband signal, which specifically includes: the interleaving comprises rectangular interleaving and triangular interleaving; when the interleaving is rectangular interleaving, the size of the data buffer is E×F Bits, and the MR number isWriting of the word baseband signals is performed in sequence from left to right and then from top to bottom, and reading of the MR digital baseband signals is performed in sequence from top to bottom and then from left to right; when the interleaving is triangle interleaving, the size of the data buffer isBits, the writing of MR digital baseband signals is performed in the order from left to right, and then from top to bottom, and the reading of MR digital baseband signals is performed in the order from top to bottom, and then from left to right.
Further, in the step S3, the transmitter performs rate matching on the MR digital baseband signal, which specifically includes: the MR digital baseband signal is retransmitted for a plurality of times to match the actual bearing capacity of a physical channel, wherein the physical channel is a physical channel of wireless communication, and the physical channel of the wireless communication is one of wireless channels;
when the actual bearing capacity of a physical channel is MxN Bits and the length of a data frame formed by an MR digital baseband signal is Mbits, the actual bearing capacity of the physical channel is equal to N times of the length of the data frame formed by the MR digital baseband signal, and after repeating the data frame formed by the MR digital baseband signal for N times, carrying out channel coding and mapping to a wireless channel;
when the actual carrying capacity of the physical channel is MxN+A Bits and the length of a data frame formed by the MR digital baseband signals is Mbits, the actual carrying capacity of the physical channel is not equal to N times of the length of the data frame formed by the MR digital baseband signals, and the remainder is A Bits, repeating the data frame formed by the MR digital baseband signals for N times, adding the first A Bits in the data frame to the end of a data stream, and then carrying out channel coding and mapping to a wireless channel.
Further, in the step S3, the transmitter performs channel coding on the MR digital baseband signal, which specifically includes: the transmitter can also transmit real-time control signals, parameter configuration and operation instructions for tuning and detuning required by the local coil; the transmitter adopts LDPC or Turbo channel coding to the MR digital baseband signal, and the transmitter adopts Polar channel coding to the real-time control signals, parameter configuration and operation instructions of tuning and detuning required by the local coil.
Further, the wireless air interface adopts a MIMO technology, and the application scale is MIMO X×Y, wherein X represents the number of transmitting antennas, Y represents the number of receiving antennas, the number of the transmitting antennas is equal to the number of the receiving antennas, and the transmitting antennas and the receiving antennas simultaneously transmit and receive data in the same frequency.
Further, when the number of the transmitting antennas and the number of the receiving antennas are both 2, the specific steps of wireless transmission are as follows:
t1, a first transmitting antenna transmits a demodulation reference signal, a second transmitting antenna keeps silent, and a receiver obtains channel characteristics h00 and h01 through a digital signal processing algorithm; the second transmitting antenna transmits demodulation reference signals, the first transmitting antenna keeps silent, and the receiver obtains channel characteristics h10 and h11 through a digital signal processing algorithm;
t2, the first transmitting antenna and the second transmitting antenna simultaneously transmit data in the same frequency, the two transmitting antennas occupy the same frequency spectrum resource, two independent parallel data streams are transmitted, and the space division multiplexing technology is utilized to multiplex the unit frequency spectrum resource for 2 times;
t3, the signal received by the first receiving antenna is rx0_r, the signal received by the second receiving antenna is rx1_r, wherein rx0_r=lc00×h00+lc01×h10, rx1_r=lc00×h01+lc01×h11,
solving a binary once equation set through matrix operation to obtain separated signals LC00 and LC01;
t4, separate signals LC00 and LC01 correspond to MR digital baseband signals received by the first and second local coil units, respectively.
Further, in the step S6, the receiver performs channel decoding on the digital signal, and specifically includes: when the transmitter adopts LDPC channel coding to the MR digital baseband signal, the receiver adopts LDPC channel decoding to the digital signal; when the transmitter adopts Turbo channel coding to the MR digital baseband signal, the receiver adopts Turbo channel decoding to the digital signal; the real-time control signals, parameter configuration and operating instructions for the local coil required tuning and detuning are decoded using Polar channels.
Further, in the step S6, the receiver performs rate de-matching on the digital signal, and specifically includes: when the actual carrying capacity of the physical channel is equal to N times of the length of a data frame formed by the MR digital baseband signals, the likelihood probability values corresponding to the same Bit in the N repeated data frame lengths are overlapped to obtain the likelihood probability of the corresponding Bit; when the actual carrying capacity of the physical channel is not equal to N times of the length of a data frame formed by the MR digital baseband signals, the demodulation likelihood probability values corresponding to the same Bit in the N repeated data frame lengths are overlapped, and the demodulation likelihood probability values corresponding to the same Bit in the (N+1) th data frame are added to obtain the likelihood probability of the corresponding Bit.
Further, in the step S6, the receiver de-interleaves the digital signal, and specifically includes: when the interleaving is rectangular interleaving, writing of digital signals is performed in sequence from top to bottom and then from left to right, and reading of digital signals is performed in sequence from left to right and then from top to bottom; when the interleaving is triangular interleaving, the writing of the digital signals is performed in the order from top to bottom and then from left to right, and the reading of the MR digital baseband signals is performed in the order from left to right and then from top to bottom.
The beneficial effects of the invention are as follows:
(1) By applying the MIMO technology, the space division multiplexing is realized, the spectrum utilization rate can be improved, the international unlicensed frequency band multiple input multiple output of wireless communication is fully utilized, the MIMO technology is a great leap in the development of the wireless communication technology, the limitation of the traditional wireless frequency resource allocation can be broken through, the spectrum efficiency of a wireless communication system is greatly improved, and the method is a key technology of the future development trend and 5G standard of the wireless communication technology. The MIMO technology breaks the conventional wireless communication mode, and requires the system to use multiple transmitting and receiving antennas, support simultaneous co-frequency to transmit and receive data, and improve the data throughput rate of unit spectrum resources through the space division multiplexing technology.
(2) The reliability and the robustness of wireless transmission can be improved by applying interleaving, rate matching and channel coding techniques. The interleaving coding can disperse longer burst errors into random errors, then the channel coding technology for correcting the random errors is used for eliminating the random errors, and the larger the interleaving depth is, the larger the dispersion is, and the stronger the burst error resistance is.
(3) Rate matching refers to the fact that bits on a transport channel are retransmitted or punctured to match the actual carrying capacity of the physical channel, and by this mapping method, the bit rate required by the transport format of the physical channel is achieved. The invention only allows the MR digital baseband signal to be retransmitted for a plurality of times during rate matching, does not allow the MR digital baseband signal to be punched, requires the actual bearing capacity of a physical channel, is larger than the throughput rate of the MR digital baseband signal required to be transmitted, improves the reliability of wireless transmission,
(4) The channel coding technique, also called error control coding, is to add redundant information to the original data at the transmitting end, where the redundant information is related to the original data, and then at the receiving end, detect and correct errors generated in the transmission process according to the correlation, so as to combat noise interference in the wireless transmission process. The channel coding technology introduced in the invention can approach the limit of the aromatic rule based on the computing capability of the current digital signal processor (ARM/DSP/FPGA), and improves the reliability and the robustness of wireless transmission.
Drawings
Fig. 1 is a schematic flow chart of a method for wireless signal transmission of a nuclear magnetic resonance imaging apparatus according to the present invention.
Fig. 2 is a schematic diagram of rectangular interleaving in the present invention.
Fig. 3 is a schematic diagram of triangle interleaving in the present invention.
Fig. 4 is a schematic diagram of a first method of rate matching in the present invention.
Fig. 5 is a schematic diagram of a second method of rate matching in the present invention.
Fig. 6 is a schematic diagram of a first method of channel coding in the present invention.
Fig. 7 is a schematic diagram of a second method of channel coding in the present invention.
Fig. 8 is a schematic diagram of an application example MIMO 2×2 in the present invention.
Fig. 9 is a schematic diagram of an application example MIMO 3×3 in the present invention.
Fig. 10 is a schematic diagram of a first method of de-rate matching in the present invention.
Fig. 11 is a schematic diagram of a second method of de-rate matching in the present invention.
Fig. 12 is a schematic diagram of rectangular deinterlacing in the present invention.
Fig. 13 is a schematic diagram of triangle deinterleaving in the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, the invention provides a method for wireless signal transmission of a nuclear magnetic resonance imaging device, which comprises the following steps:
s1, local coil units receive MR analog signals, the number of the local coil units is multiple, and the local coil units form a local coil unit array to receive the MR analog signals.
S2, after the MR analog signals sequentially pass through a first mixer, an analog-to-digital converter and a digital down converter, MR digital baseband signals are obtained; wherein the number of the first mixers, the analog-to-digital converters and the digital down-converters is the same as the number of the local coil units.
S3, the transmitter carries out interleaving, rate matching and channel coding on the MR digital baseband signal to obtain a digital signal and maps the digital signal to a wireless channel; wherein the number of wireless channels is the same as the number of local coil units.
S31, interweaving: the present embodiment proposes two interleaving methods: rectangular interleaving and triangular interleaving.
As shown in FIG. 2, in the interleaving process, there is a cache memory, the size of the data buffer is E×F Bits, the original data of the rectangular interleaving is written into the data buffer (E row/F column) row by row according to the sequence from left to right and then from top to bottom, and then the output of the interleaving process is to read out the data from the data buffer (E row/F column) row by row according to the sequence from top to bottom and then from left to right.
Triangle interleaving As shown in FIG. 3, the size of the data buffer isThe data is read out from the data buffer (E columns) from column to column according to the sequence from top to bottom, and then the output of the interleaving process is that the data is read out from the data buffer (E columns).
S32, rate matching: in this embodiment, in order to improve the reliability of wireless transmission, the actual carrying capacity of the physical channel is greater than the throughput rate of MR digital baseband signals to be transmitted. The transmitter is re-transmitted multiple times during rate matching to match the actual carrying capacity of the physical channel (the channel that exists in an objective physical manner as specified by the radio alliance), and by this mapping method, the bit rate required by the physical channel transport format, i.e. the bit rate required by the corresponding international standard channel transport format, is achieved.
As shown in fig. 4, the actual carrying capacity (mxn Bits) of the physical channel is exactly equal to an integer multiple (N times) of the data frame length (mxts), so that the rate matching process is to repeat the data frame formed by the MR digital baseband signal N times, then perform channel coding, and finally map to the radio channel.
The second method of rate matching is shown in fig. 5, where the actual carrying capacity (mxn+a Bits) of the physical channel is not equal to an integer multiple (N times) of the data frame length (M Bits), and the remainder is a Bits. The process of rate matching is to repeat the data frame formed by the MR digital baseband signal N times, then add the first a Bits information in the data frame to the end of the data stream (as the n+1st repeated data frame), perform channel coding, and finally map to the wireless channel.
The physical channel has a physical carrying capacity greater than the MR digital baseband signal throughput rate required to be transmitted, and therefore contains multiple retransmitted MR digital baseband signals in the received data stream.
S33, channel coding: the transmitter may also transmit real-time control signals, parameter configurations and operating instructions for the local coil to be tuned and detuned.
The first method of channel coding is shown in fig. 6, where the transmitter uses LDPC channel coding for MR digital baseband signals, and Polar channel coding for real-time control signals, parameter configurations, and operating instructions for the local coil tuning and detuning.
In fig. 6, M local coil units are supported in total, the MR digital baseband signal is encoded by using an LDPC channel, the real-time control signals, parameter configuration and operation instructions for tuning and detuning the local coil are encoded by using Polar channels, then mapped to corresponding wireless channels, and transmitted to an air interface after being modulated by OFDM.
A second method of channel coding is shown in fig. 7, where the transmitter uses Turbo channel coding for MR digital baseband signals, and Polar channel coding for real-time control signals, parameter configuration and operating instructions for tuning and detuning the local coil.
In fig. 7, M local coil units are supported in total, the MR digital baseband signal is encoded by using a Turbo channel, the real-time control signals, parameter configuration and operation instructions for tuning and detuning the local coil are encoded by using a Polar channel, then mapped to corresponding wireless channels, and transmitted to an air interface after being modulated by OFDM.
S4, after OFDM modulation is carried out on the digital signals by the transmitter, microwave signals are obtained and sent to a wireless air interface.
In the embodiment, the MIMO technology is applied to a nuclear magnetic resonance signal wireless transmission system, so that space division multiplexing is realized, and the spectrum utilization rate is improved.
The scale supported by this embodiment is: MIMO mxn (where the range of values of M and N is 1 to 128, respectively), M refers to the number of transmit antennas, N refers to the number of receive antennas, and 2 typical application examples are shown in fig. 6 and 7:
as shown in fig. 8, the MIMO 2X2 application example has the number of transmitting antennas and receiving antennas of 2, so that in the process of wireless communication, the spatial multiplexing technology can multiplex unit spectrum resources 2 times, and the specific steps are as follows:
t1, channel estimation, TX0 transmits DMRS (demodulation reference signal), TX1 keeps silent, and a receiver obtains channel characteristics h00 and h01 through a digital signal processing algorithm; TX1 transmits DMRS (demodulation reference signal), TX0 keeps silent, and the receiver obtains channel characteristics h10 and h11 through a digital signal processing algorithm.
T2, data transmission, TX0 and TX1 transmit data at the same frequency at the same time, two transmitting antennas occupy the same frequency spectrum resource, and transmit two independent parallel data streams, and the unit frequency spectrum resource can be multiplexed for 2 times by using a space division multiplexing technology.
T3, data reception and separation, the signal received by the receiving antenna RX0 is rx0_r, the signal received by the receiving antenna RX1 is rx1_r, wherein rx0_r=lc00×h00+lc01×h10, and rx1_r=lc00×h01+lc01×h11 (channel characteristics h00/h01/h10/h11 are known results obtained in step T1).
Solving a binary once equation set through matrix operation to obtain separated signals LC00 and LC01;
and T4, the results LC00 and LC01 of data separation correspond to the nuclear magnetic resonance MR digital baseband signals received by the local coil unit 00 and the local coil unit 01 respectively and are independently transmitted to an image reconstruction system.
MIMO 2X2 requires that the number of transmitting antennas and receiving antennas is 2, and the same frequency is used for transmitting and receiving data, the same frequency spectrum resource is multiplexed for 2 times, and the data throughput rate of unit frequency spectrum resource is improved by 2 times through a space division multiplexing technology.
As shown in fig. 9, the principle of the example MIMO 3X3 is the same as that of the example MIMO 2X2, the number of transmitting antennas and receiving antennas of the system is required to be 3, the same frequency is used for transmitting and receiving data, the same frequency spectrum resource is multiplexed for 3 times, and the data throughput rate of the unit frequency spectrum resource is improved by 3 times through a space division multiplexing technology.
S5, the receiver receives the microwave signals from the wireless air interface, performs OFDM demodulation and separates out the digital signals carried by the wireless channels.
S6, the receiver performs channel decoding, de-rate matching and de-interleaving on the digital signal to restore the MR digital baseband signal.
S61, channel decoding:
the first method of channel decoding is shown in fig. 6, in which the transmitter uses LDPC channel coding for the MR digital baseband signal, and the receiver uses LDPC channel decoding for the digital signal; the real-time control signals, parameter configuration and operating instructions for the local coil required tuning and detuning are decoded using Polar channels.
In fig. 6, the receiver receives microwave signals from the air interface, performs OFDM demodulation, separates out digital signals carried by each radio channel, decodes MR digital baseband signals by using LDPC channels, and restores corresponding digital information after real-time control signals, parameter configuration and operation instructions for tuning and detuning required by local coils are decoded by using Polar channels.
The second method of channel decoding is shown in fig. 7, in which the transmitter uses Turbo channel coding for MR digital baseband signals, and the receiver uses Turbo channel decoding for digital signals; the real-time control signals, parameter configuration and operating instructions for the local coil required tuning and detuning are decoded using Polar channels.
In fig. 7, the receiver receives microwave signals from the air interface, performs OFDM demodulation, separates out digital signals carried by each radio channel, decodes MR digital baseband signals by using Turbo channels, and restores corresponding digital information after real-time control signals, parameter configuration and operation instructions for tuning and detuning required by the local coil are decoded by using Polar channels.
S62, rate de-matching: when the receiver is in rate de-matching, the input data is a demodulated data stream, and each Bit information code in the demodulated data stream corresponds to 1 likelihood probability value.
The first method of de-rate matching is shown in fig. 10, where the physical channel actual bearer capability (mxn Bits) is exactly equal to an integer multiple (N times) of the data frame length (mxts).
The rate-resolving matching is to superimpose the demodulation likelihood probability value corresponding to the 1 st repeated data frame (Bit 1)/the 2 nd repeated data frame (Bit 1) … … nth repeated data frame (Bit 1) to obtain the likelihood probability corresponding to the final data frame Bit 1; the demodulation likelihood probability values corresponding to the 1 st repeated data frame (Bit 2)/2 nd repeated data frame (Bit 2) … … nth repeated data frame (Bit 2) are overlapped to obtain likelihood probability corresponding to the final data frame Bit 2; the demodulation likelihood probability values corresponding to the 1 st repeated data frame (Bit M)/the 2 nd repeated data frame (Bit M) … … nth repeated data frame (Bit M) of the data frames are superimposed to obtain likelihood probabilities corresponding to the final data frame Bit M.
The second method of de-rate matching is shown in fig. 11, where the physical channel actual bearer capability (mxn+a Bits) is not equal to an integer multiple (N times) of the data frame length (M Bits), and the remainder is a Bits.
The de-rate matching is to superimpose the demodulation likelihood probability value corresponding to the (n+1) th repeated data frame (Bit 1) with the (1) st repeated data frame (Bit 1)/the (2) nd repeated data frame (Bit 1) … … nth repeated data frame (Bit 1) of the data frame to obtain the likelihood probability corresponding to the final data frame Bit 1; the 1 st repeated data frame (Bit 2)/2 nd repeated data frame (Bit 2) … … nth repeated data frame (Bit 2), and the demodulation likelihood probability values corresponding to the (n+1) th repeated data frame (Bit 2) are superimposed to obtain likelihood probabilities corresponding to the final data frame Bit 2; the 1 st repeated data frame (Bit M)/2 nd repeated data frame (Bit M) … … nth repeated data frame (Bit M), and the demodulation likelihood probability values corresponding to the n+1st repeated data frame (Bit M) are superimposed to obtain the likelihood probability corresponding to the final data frame Bit M.
Wherein, in the n+1st repeated data frame, the likelihood probability value is zero for the information codes corresponding to Bit (a+1) to Bit M.
S63, de-interleaving: the present embodiment proposes two de-interleaving methods: rectangular deinterlacing and triangular deinterlacing.
As shown in fig. 12, the size of the data buffer is e×f Bits, and the data buffer (E line/F column) is written into the data buffer column by column in the order from top to bottom, and then from left to right, so that the output of the deinterleaving process is to read out the data from the data buffer column (E line/F column) row by row in the order from left to right, and then from top to bottom.
Triangle deinterleaving as shown in fig. 13, the data buffer size isThe data is read out from the data buffer (E rows) row by row according to the sequence from left to right and from top to bottom.
The two interleaving and de-interleaving methods described in this embodiment include: the greater the depth (scale) of interleaving, that is, the greater the number of rows and columns of the data buffer, the greater the dispersion and the greater the burst error resistance, but the greater the pipeline processing delay introduced, the greater the trade-off and flexible configuration of interleaving depth and pipeline processing delay is required in an actual nuclear magnetic resonance system.
S7, the MR digital baseband signals sequentially pass through a digital up-converter, a digital-to-analog conversion module and a second mixer to obtain MR analog signals corresponding to the local coil units; the number of the digital up-converters, the digital-to-analog conversion modules and the second mixers is the same as the number of the local coil units.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art will understand that; the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced with equivalents; such modifications and substitutions do not depart from the spirit of the invention, and are intended to be included within the scope of the appended claims and description.
Claims (9)
1. A method for wireless transmission of signals from a magnetic resonance imaging apparatus, comprising:
s1, receiving an MR analog signal by a local coil unit; the local coil units are arranged in a plurality, and the local coil units form a local coil unit array to receive MR analog signals;
s2, after the MR analog signals sequentially pass through a first mixer, an analog-to-digital converter and a digital down converter, MR digital baseband signals are obtained;
s3, the transmitter carries out interleaving, rate matching and channel coding on the MR digital baseband signal to obtain a digital signal and maps the digital signal to a wireless channel;
s4, after OFDM modulation is carried out on the digital signal by the transmitter, a microwave signal is obtained and sent to a wireless air interface;
s5, the receiver receives the microwave signal from the wireless air interface, performs OFDM demodulation and separates out the digital signal carried by the wireless channel;
s6, the receiver performs channel decoding, rate de-matching and de-interleaving on the digital signal to restore an MR digital baseband signal;
s7, the MR digital baseband signals sequentially pass through a digital up-converter, a digital-to-analog conversion module and a second mixer to obtain MR analog signals corresponding to the local coil units;
the number of the first mixers, the analog-to-digital converter, the digital down converter, the wireless channel, the digital up converter, the digital-to-analog conversion module and the second mixers is the same as the number of the local coil units.
2. The method according to claim 1, wherein in the step S3, the transmitter interleaves, rate-matches, and channel-encodes the MR digital baseband signal to obtain a digital signal, and maps the digital signal to a wireless channel, and the method specifically comprises: the interleaving comprises rectangular interleaving and triangular interleaving; when the interleaving is rectangular interleaving, the size of the data buffer is E×F Bits, writing of MR digital baseband signals is performed in sequence from left to right and then from top to bottom, and reading of MR digital baseband signals is performed in sequence from top to bottom and then from left to right; when the interleaving is triangular interleaving, the data buffer is written in the order from left to right and then from top to bottom, and the MR digital baseband signal is read out in the order from top to bottom and then from left to right.
3. A method for wireless transmission of signals from a magnetic resonance imaging apparatus according to claim 2, wherein the transmitter rate-matches the MR digital baseband signal, specifically comprising: the MR digital baseband signal is retransmitted for a plurality of times to match the actual bearing capacity of a physical channel, wherein the physical channel is a physical channel of wireless communication, and the physical channel of the wireless communication is one of wireless channels; when the actual bearing capacity of a physical channel is MxN Bits and the length of a data frame formed by an MR digital baseband signal is Mbits, the actual bearing capacity of the physical channel is equal to N times of the length of the data frame formed by the MR digital baseband signal, and after repeating the data frame formed by the MR digital baseband signal for N times, carrying out channel coding and mapping to a wireless channel; when the actual carrying capacity of the physical channel is MxN+A Bits and the length of a data frame formed by the MR digital baseband signals is Mbits, the actual carrying capacity of the physical channel is not equal to N times of the length of the data frame formed by the MR digital baseband signals, and the remainder is A Bits, repeating the data frame formed by the MR digital baseband signals for N times, adding the first A Bits in the data frame to the end of a data stream, and then carrying out channel coding and mapping to a wireless channel.
4. A method for wireless transmission of signals from a magnetic resonance imaging apparatus according to claim 3, wherein the transmitter performs channel coding on the MR digital baseband signals, and in particular comprises: the transmitter also transmits real-time control signals, parameter configuration and operation instructions for tuning and detuning required by the local coil; the transmitter adopts LDPC or Turbo channel coding to the MR digital baseband signal, and the transmitter adopts Polar channel coding to the real-time control signals, parameter configuration and operation instructions of tuning and detuning required by the local coil.
5. A method according to claim 1, wherein the wireless air interface is of MIMO technology, and the application scale is MIMO X Y, where X represents the number of transmitting antennas and Y represents the number of receiving antennas, the number of transmitting antennas being equal to the number of receiving antennas, and the transmitting antennas and the receiving antennas simultaneously transmit and receive data at the same frequency.
6. The method of claim 5, wherein when the number of the transmitting antennas and the number of the receiving antennas are both 2, the specific steps of wireless transmission are as follows:
t1, a first transmitting antenna transmits a demodulation reference signal, a second transmitting antenna keeps silent, and a receiver obtains channel characteristics h00 and h01 through a digital signal processing algorithm; the second transmitting antenna transmits demodulation reference signals, the first transmitting antenna keeps silent, and the receiver obtains channel characteristics h10 and h11 through a digital signal processing algorithm;
t2, the first transmitting antenna and the second transmitting antenna simultaneously transmit data in the same frequency, the two transmitting antennas occupy the same frequency spectrum resource, two independent parallel data streams are transmitted, and the space division multiplexing technology is utilized to multiplex the unit frequency spectrum resource for 2 times;
t3, the signal received by the first receiving antenna is RX0_r, the signal received by the second receiving antenna is RX1_r, wherein RX 0_r=lc00×h00+lc01×h10, and RX 1_r=lc00×h01+lc01×h11, and the binary system of equations is solved by matrix operation, so as to obtain separated signals LC00 and LC01;
t4, separate signals LC00 and LC01 correspond to MR digital baseband signals received by the first and second local coil units, respectively.
7. The method for wireless transmission of signals in a mri apparatus of claim 4, wherein said receiver performs channel decoding of digital signals, comprising:
when the transmitter adopts LDPC channel coding to the MR digital baseband signal, the receiver adopts LDPC channel decoding to the digital signal; when the transmitter adopts Turbo channel coding to the MR digital baseband signal, the receiver adopts Turbo channel decoding to the digital signal; the real-time control signals, parameter configuration and operating instructions for the local coil required tuning and detuning are decoded using Polar channels.
8. The method for wireless transmission of signals in a mri apparatus of claim 7, wherein said receiver performs rate de-matching on the digital signals, comprising:
when the actual carrying capacity of the physical channel is equal to N times of the length of a data frame formed by the MR digital baseband signals, the likelihood probability values corresponding to the same Bit in the N repeated data frame lengths are overlapped to obtain the likelihood probability of the corresponding Bit;
when the actual carrying capacity of the physical channel is not equal to N times of the length of a data frame formed by the MR digital baseband signals, the demodulation likelihood probability values corresponding to the same Bit in the N repeated data frame lengths are overlapped, and the demodulation likelihood probability values corresponding to the same Bit in the (N+1) th data frame are added to obtain the likelihood probability of the corresponding Bit.
9. A method for wireless transmission of signals from a mri apparatus according to claim 8, wherein said receiver de-interleaves the digital signals, comprising: when the interleaving is rectangular interleaving, writing of digital signals is performed in sequence from top to bottom and then from left to right, and reading of digital signals is performed in sequence from left to right and then from top to bottom; when the interleaving is triangular interleaving, the writing of the digital signals is performed in the order from top to bottom and then from left to right, and the reading of the MR digital baseband signals is performed in the order from left to right and then from top to bottom.
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