CN112019300A - Method for wireless signal transmission of nuclear magnetic resonance imaging equipment - Google Patents
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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 signal; sequentially passing through a first mixer, an analog-to-digital converter and a digital down converter to obtain an MR digital baseband signal; performing interleaving, rate matching and channel coding on the MR digital baseband signals, and mapping the MR digital baseband signals to a wireless channel; after OFDM modulation is carried out on the digital signal, the digital signal is sent to a wireless air interface; the receiver receives signals from a wireless air interface and carries out OFDM demodulation; performing channel decoding, rate de-matching and de-interleaving to restore the MR digital baseband signal; the MR digital baseband signal sequentially passes through the digital up-converter, the digital-to-analog conversion module and the 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 spectrum utilization rate and reliability of the wireless transmission of the nuclear magnetic resonance signals, and simultaneously enable the system to be simpler 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
Usually, the signal transmission of the magnetic resonance apparatus is carried out via a cable connected to a local receiving coil. When scanning a patient, the distance between the cable and the patient is very close due to space constraints. The method not only brings great inconvenience to doctors for placing the coils; moreover, due to the antenna effect of the cable, when the carrier coil transmits power, current can be generated on the cable, which causes discomfort to the patient and can seriously burn the patient. Furthermore, the cost of the system is greatly increased due to the presence of a large number of cables in the coil and inside the patient's bed. In order to solve the problem of the cable antenna effect, the transmission of the magnetic resonance signal is realized in the industry by adopting an optical fiber communication mode, but practice shows that the optical fiber communication scheme still brings inconvenience to a doctor when using a coil; but also brings about a further increase in cost.
Disclosure of Invention
The invention provides a signal wireless transmission method of nuclear magnetic resonance imaging equipment, which can reduce power consumption and cost, obtain better image quality and signal-to-noise ratio, ensure the spectrum utilization rate and reliability of the wireless transmission of nuclear magnetic resonance signals, and simultaneously enable a system to be simpler through the wireless transmission of signals.
The invention adopts the following technical scheme:
a method for wireless signal transmission of a nuclear magnetic resonance imaging device comprises the following steps:
s1, receiving the MR analog signal by the local coil unit;
s2, the MR analog signal sequentially passes through the first mixer, the analog-to-digital converter and the digital down converter to obtain an MR digital baseband signal;
s3, the transmitter interweaves, matches the speed and codes the channel to the MR digital baseband signal, obtains the digital signal and maps to the wireless channel;
s4, after OFDM modulation is carried out on the digital signal by the transmitter, a microwave signal is obtained and sent to the wireless air interface;
s5, the receiver receives the microwave signal from the wireless air interface, OFDM demodulation is carried out, and the digital signal carried by the wireless channel is separated;
s6, the receiver carries out channel decoding, rate de-matching and de-interleaving on the digital signal to restore the MR digital baseband signal;
and S7, the MR digital baseband signal sequentially passes through the digital up-converter, the digital-to-analog conversion module and the second mixer to obtain an MR analog signal corresponding to the local coil unit.
Furthermore, the number of the local coil units is multiple, and the local coil unit array formed by the multiple local coil units receives the MR analog signals; the number of the first frequency mixers, the analog-to-digital converters, the digital down converters, the wireless channels, the digital up converters, the digital-to-analog conversion modules and the second frequency mixers is the same as that of the local coil units.
Further, in step S3, the interleaving of the MR digital baseband signal by the transmitter specifically includes: the interweaving comprises rectangular interweaving and triangular interweaving; when the interleaving is rectangular interleaving, the size of the data buffer is E multiplied by F Bits, the writing of the MR digital baseband signals is performed according to the sequence from left to right first and then from top to bottom, and the reading of the MR digital baseband signals is performed according to the sequence from top to bottom first and then from left to right; when the interleaving is triangular interleaving, the size of the data buffer is
Bits, the writing of the MR digital baseband signals is performed in the order from left to right, then from top to bottom, and the reading of the MR digital baseband signals is performed in the order from top to bottom, then from left to right.
Further, in step S3, the rate matching of the MR digital baseband signal by the transmitter specifically includes: the MR digital baseband signal is retransmitted for a plurality of times to match the actual carrying 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 M multiplied by N Bits and the length of a data frame formed by MR digital baseband signals is M Bits, 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 signals, and after repeating the data frame formed by the MR digital baseband signals for N times, channel coding is carried out and the data frame is mapped to a wireless channel;
when the actual bearing capacity of a physical channel is M multiplied by N + A Bits, and the length of a data frame formed by MR digital baseband signals is M Bits, the actual bearing 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 initial A Bits in the data frame to the tail of a data stream, performing channel coding and mapping to a wireless channel.
Further, in step S3, the channel coding is performed on the MR digital baseband signal by the transmitter, which specifically includes: the transmitter can also transmit real-time control signals, parameter configuration and operation instructions of tuning and detuning required by the local coil; the transmitter adopts LDPC or Turbo channel coding to MR digital baseband signals, and Polar channel coding is adopted to the transmitter to the real-time control signals, parameter configuration and operation instructions of the local coils which need tuning and detuning.
Further, the wireless air interface adopts MIMO technology, the application scale is MIMO X Y, where X represents the number of transmitting antennas, Y represents the number of receiving antennas, the number of transmitting antennas is equal to the number of receiving antennas, and the transmitting antennas and the receiving antennas transmit and receive data at the same time and 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, the first transmitting antenna sends a demodulation reference signal, the second transmitting antenna keeps silent, and the 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, a first transmitting antenna and a second transmitting antenna transmit data at the same frequency, the two transmitting antennas occupy the same frequency spectrum resource, transmit two independent parallel data streams, and multiplex the frequency spectrum resource for 2 times by using a space division multiplexing technology;
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 is LC00 × h00+ LC01 × h10, RX1_ R is LC00 × h01+ LC01 × h11,
solving a system of linear equations with two variables through matrix operation to obtain separated signals LC00 and LC 01;
t4, separate signals LC00 and LC01 correspond to the MR digital baseband signals received by the first and second local coil units, respectively.
Further, in step S6, the channel decoding of the digital signal by the receiver 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; real-time control signals, parameter configuration and operation instructions of tuning and detuning required by the local coil are decoded by adopting Polar channels.
Further, in step S6, the rate de-matching the digital signal by the receiver specifically includes: when the actual bearing 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 demodulation likelihood probability values corresponding to the same Bit in the lengths of the N repeated data frames are superposed to obtain the likelihood probability corresponding to the Bit; when the actual bearing 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 lengths of N repeated data frames are superposed, 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 corresponding to the Bit.
Further, in step S6, the deinterleaving, by the receiver, specifically includes: when the interweaving is rectangular interweaving, the writing of the digital signals is performed according to the sequence from top to bottom and then from left to right, and the reading of the digital signals is performed according to the 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 according to the sequence from top to bottom and then from left to right, and the reading of the MR digital baseband signals is performed according to the sequence from left to right and then from top to bottom.
The invention has the beneficial effects that:
(1) the MIMO technology is a great leap of the development of the wireless communication technology, can break through the limitation of the traditional wireless frequency resource allocation, greatly improves the spectrum efficiency of a wireless communication system, and is a key technology of the future development trend of the wireless communication technology and the 5G standard. The MIMO technology also breaks the traditional wireless communication mode, and it requires the system to use multiple transmitting and receiving antennas, support simultaneous co-frequency to transmit and receive data, and improve the data throughput of unit spectrum resources through the space division multiplexing technology.
(2) By applying interleaving, rate matching and channel coding techniques, the reliability and robustness of wireless transmission can be improved. The interleaving coding can disperse longer burst errors into random errors, and then the channel coding technology for correcting the random errors is used for eliminating the random errors, wherein the greater the interleaving depth is, the greater the dispersion is, and the stronger the burst error resistance is.
(3) Rate matching means that bits on a transmission channel are retransmitted or punctured to match the actual carrying capacity of a physical channel, and the bit rate required by the transmission format of the physical channel is achieved through the mapping method. The invention only allows the MR digital baseband signal to be retransmitted for a plurality of times and not to be punched when the rate is matched, requires the actual bearing capacity of the physical channel to be more than the throughput rate of the MR digital baseband signal to be transmitted, improves the reliability of wireless transmission,
(4) channel coding, also called error control coding, is to add redundant information to original data at the transmitting end, the redundant information is related to the original data, and then at the receiving end, detect and correct the errors generated during transmission according to the correlation, so as to combat the noise interference during wireless transmission. The channel coding technology introduced in the invention can approach the limit of the aroma theorem based on the computing capacity of the current digital signal processor (ARM/DSP/FPGA), and improves the reliability and robustness of wireless transmission.
Drawings
Fig. 1 is a schematic flow chart of a method for wireless signal transmission of an mri 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 diagram illustrating a first method of rate matching according to the present invention.
Fig. 5 is a diagram illustrating a second method of rate matching according to the present invention.
Fig. 6 is a diagram illustrating a first method of channel coding according to the present invention.
Fig. 7 is a diagram illustrating a second method of channel coding according to the present invention.
Fig. 8 is a schematic diagram of an application example MIMO 2 × 2 in the present invention.
Fig. 9 is a diagram of MIMO 3 × 3 as an example of application in the present invention.
Fig. 10 is a diagram illustrating a first method of de-rate matching according to the present invention.
Fig. 11 is a diagram illustrating a second method of de-rate matching in the present invention.
Fig. 12 is a schematic diagram of rectangular deinterleaving in the present invention.
Fig. 13 is a schematic diagram of triangle de-interleaving 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 present invention provides a method for wireless signal transmission of a magnetic resonance imaging apparatus, comprising the following steps:
s1, the local coil units receive the MR analog signals, the number of the local coil units is multiple, and the local coil unit arrays formed by the multiple local coil units receive the MR analog signals.
S2, the MR analog signal sequentially passes through the first mixer, the analog-to-digital converter and the digital down converter to obtain an MR digital baseband signal; the number of the first mixers, the analog-to-digital converters and the digital down converters is the same as that of the local coil units.
S3, the transmitter interweaves, matches the speed and codes the channel to the MR digital baseband signal, obtains the digital signal and maps to the wireless channel; wherein the number of wireless channels is the same as the number of local coil units.
S31, interweaving: this embodiment proposes two interleaving methods: rectangular interleaving and triangular interleaving.
Rectangular interleaving as shown in fig. 2, during interleaving, there is a cache, the size of the data cache is E × F Bits, the original data of the rectangular interleaving is written into the data cache line by line (E row/F column) in the order from left to right, then from top to bottom, then the output of the interleaving process is to read the data from the data cache line by line (E row/F column) in sequence from top to bottom, then from left to right.
Triangle interleaving As shown in FIG. 3, the data buffer size is
Bits, original data interleaved in a triangle are written into a data buffer line by line (E line) in the sequence from left to right first and then from top to bottom, and then the output of the interleaving process is to read the data out of the data buffer line by line (E line) in sequence from top to bottom and then from left to right.
S32, rate matching: in this embodiment, in order to improve reliability of wireless transmission, an actual carrying capacity of a physical channel is greater than a throughput rate of an MR digital baseband signal to be transmitted. At the time of rate matching, the transmitter retransmits the MR digital baseband signal multiple times to match the actual carrying capacity of the physical channel (channel existing according to the objective physics specified by the radio alliance), and by this mapping method, the bit rate required by the physical channel transmission format, i.e., the bit rate required by the corresponding international standard channel transmission format, is achieved.
The first method of rate matching is shown in fig. 4, where the actual carrying capacity (M × N Bits) of the physical channel is exactly equal to the integral multiple (N times) of the length (M Bits) of the data frame, so that the process of rate matching is to repeat the data frame formed by the MR digital baseband signal N times, perform channel coding, and finally map the data frame to the radio channel.
The second method of rate matching is shown in fig. 5, where the actual carrying capacity (M × N + a Bits) of the physical channel is not equal to the integer multiple (N times) of the length (M Bits) of the data frame, and the remainder is a Bits. Therefore, the process of rate matching is to repeat the data frame formed by the MR digital baseband signal N times, add the initial a Bits information in the data frame to the end of the data stream (as the N +1 th repeated data frame), perform channel coding, and finally map to the wireless channel.
The actual carrying capacity of the physical channel is greater than the throughput rate of the MR digital baseband signal to be transmitted, so that a plurality of retransmitted MR digital baseband signals are contained in the received data stream.
S33, channel coding: the transmitter may also transmit real-time control signals, parameter configurations, and operational instructions for tuning and detuning of the local coil as desired.
The first method of channel coding is shown in fig. 6, where the transmitter uses LDPC channel coding for the MR digital baseband signal, and the transmitter uses Polar channel coding for the real-time control signal, parameter configuration, and operation command for tuning and detuning of the local coil.
In fig. 6, M local coil units are supported in total, the MR digital baseband signal is encoded by using an LDPC channel, and the real-time control signal, parameter configuration, and operation instruction for tuning and detuning required for the local coil are encoded by using a Polar channel, then mapped to a corresponding wireless channel, modulated by OFDM, and transmitted to the air interface.
The second method of channel coding is shown in fig. 7, the transmitter uses Turbo channel coding for the MR digital baseband signal, and Polar channel coding is used for the real-time control signal, parameter configuration and operation instruction for tuning and detuning required by the local coil.
In fig. 7, M local coil units are supported in total, the MR digital baseband signal is encoded by a Turbo channel, and the real-time control signal, parameter configuration, and operation instruction for tuning and detuning of the local coil are encoded by a Polar channel, mapped to a corresponding wireless channel, modulated by OFDM, and transmitted to the air interface.
And S4, the transmitter performs OFDM modulation on the digital signal to obtain a microwave signal and sends the microwave signal to the wireless air interface.
In the embodiment, the MIMO technology is applied to the nuclear magnetic resonance signal wireless transmission system, so that space division multiplexing is realized, and the frequency spectrum utilization rate is improved.
The scale supported by this example is: MIMO M × N (where M and N range from 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:
application example MIMO 2X2 as shown in fig. 8, the number of transmit antennas and receive antennas is 2, so in the process of wireless communication, the space division multiplexing technique can multiplex 2 times the unit spectrum resource, and the specific steps are as follows:
t1, channel estimation, wherein DMRS (demodulation reference signal) is transmitted by a TX0, the TX1 keeps silent, and the receiver obtains channel characteristics h00 and h01 through a digital signal processing algorithm; TX1 transmits DMRS (demodulation reference signals), TX0 keeps silent, and a 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, two transmitting antennas occupy the same frequency spectrum resource, two independent parallel data streams are transmitted, and the single frequency spectrum resource can be multiplexed for 2 times by utilizing a space division multiplexing technology.
T3, data reception and separation, where the signal received by the receiving antenna RX0 is RX0_ R, and the signal received by the receiving antenna RX1 is RX1_ R, where RX0_ R is LC00 × h00+ LC01 × h10, and RX1_ R is LC00 × h01+ LC01 × h11 (channel characteristics h00/h01/h10/h11 are known results obtained in step T1).
Solving a system of linear equations of two-dimentional system through matrix operation to obtain separated signals LC00 and LC 01;
t4, and data separation results LC00 and LC01, which correspond to the MR digital baseband signals received by the local coil unit 00 and the local coil unit 01, respectively, are independently transmitted to an image reconstruction system.
The MIMO 2X2 requires that the number of transmitting antennas and receiving antennas is 2, and simultaneously, data is transmitted and received with the same frequency, the same spectrum resource is multiplexed 2 times, and the data throughput rate of the unit spectrum resource is improved by 2 times by the space division multiplexing technology.
Fig. 9 shows an application example MIMO 2X2, where the principle of the example MIMO 3X3 is the same as that of MIMO 2X2, and the number of transmitting antennas and receiving antennas of the system is required to be 3, and data is transmitted and received with the same frequency, the same spectrum resource is multiplexed 3 times, and the data throughput of the unit spectrum resource is improved by 3 times by the space division multiplexing technology.
S5, the receiver receives the microwave signal from the wireless air interface, OFDM demodulation is carried out, and the digital signal carried by the wireless channel is separated.
And S6, the receiver performs channel decoding, rate de-matching and de-interleaving on the digital signal to restore the MR digital baseband signal.
S61, channel decoding:
a first method of channel decoding is shown in fig. 6, in which a transmitter performs LDPC channel coding on an MR digital baseband signal, and a receiver performs LDPC channel decoding on the digital signal; real-time control signals, parameter configuration and operation instructions of tuning and detuning required by the local coil are decoded by adopting Polar channels.
In fig. 6, the receiver receives microwave signals from the air interface, and after OFDM demodulation, separates out digital signals carried by each radio channel, and restores corresponding digital information after decoding MR digital baseband signals by using LDPC channels and decoding real-time control signals, parameter configurations, and operation instructions for tuning and detuning of local coils by using Polar channels.
A second method of channel decoding is shown in fig. 7, in which a transmitter performs Turbo channel coding on MR digital baseband signals, and a receiver performs Turbo channel decoding on the digital signals; real-time control signals, parameter configuration and operation instructions of tuning and detuning required by the local coil are decoded by adopting Polar channels.
In fig. 7, the receiver receives microwave signals from the air interface, performs OFDM demodulation, separates digital signals carried by each radio channel, decodes MR digital baseband signals by using Turbo channels, decodes real-time control signals, parameter configurations, and operation instructions for tuning and detuning of local coils by using Polar channels, and restores corresponding digital information.
S62, rate de-matching: when the receiver is used for 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 actual carrying capacity (M × N Bits) of the physical channel is exactly equal to an integer multiple (N times) of the length (M Bits) of the data frame.
The de-rate matching is to superpose the demodulation likelihood probability values corresponding to the 1 st repeated data frame (Bit 1)/the 2 nd repeated data frame (Bit1) … … and the Nth repeated data frame (Bit1) 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)/the 2 nd repeated data frame (Bit2) … … the Nth repeated data frame (Bit2) are superposed to obtain the 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 frame are superposed to obtain the likelihood probability corresponding to the final data frame Bit M.
The second method of de-rate matching is shown in fig. 11, where the actual carrying capacity (M × N + a Bits) of the physical channel is not equal to the integer multiple (N times) of the length (M Bits) of the data frame, and the remainder is a Bits.
The de-rate matching is to superpose the demodulation likelihood probability values corresponding to the 1 st repeated data frame (Bit 1)/the 2 nd repeated data frame (Bit1) … … nth repeated data frame (Bit1) and the (N +1) th repeated data frame (Bit1) 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)/the 2 nd repeated data frame (Bit2) … … the nth repeated data frame (Bit2), and the N +1 th repeated data frame (Bit2) are superposed to obtain the 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), and the N +1 th repeated data frame (Bit M) are superposed to obtain the likelihood probability corresponding to the final data frame Bit M.
In the (N +1) th repeated data frame, the likelihood probability value of the information codes corresponding to Bit (A +1) to Bit M is zero.
S63, deinterleaving: this embodiment proposes two deinterleaving methods: rectangular deinterleaving and triangular deinterleaving.
Rectangular deinterleave as shown in fig. 12, the size of the data buffer is E × F Bits, the original data of the rectangular deinterleave is written into the data buffer (E row/F column) column by column according to the sequence from top to bottom and then from left to right, and then the output of the deinterleave process is to read the data from the data buffer (E row/F column) row by row sequentially according to the sequence from left to right and then from top to bottom.
Triangle De-interlacing As shown in FIG. 13, the data buffer size is
Bits, the original data of triangle deinterleave is written into the data buffer (E column) column by column according to the sequence from top to bottom, then from left to right, then the output of the deinterleave process is to read the data from the data buffer (E row) row by row in sequence according to the sequence from left to right, then from top to bottom.
The two interleaving and deinterleaving methods described in this embodiment include: the interleaving depth (scale) is larger, that is, the number of rows and columns of the data buffer is larger, the dispersion is larger, the burst error resistance is stronger, but the introduced pipeline processing delay is larger, and in an actual nuclear magnetic resonance system, the interleaving depth and the pipeline processing delay need to be balanced and flexibly configured.
S7, the MR digital baseband signal sequentially passes through the digital up-converter, the digital-to-analog conversion module and the second mixer to obtain an MR analog signal corresponding to the local coil unit; the number of the digital up-converters, the digital-to-analog conversion modules and the second mixers is the same as that of the local coil units.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art; the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; these modifications and substitutions do not cause the essence of the corresponding technical solution to depart from the scope of the technical solution of the embodiments of the present invention, and are intended to be covered by the claims and the specification of the present invention.
Claims (10)
1. A method for wireless signal transmission of a nuclear magnetic resonance imaging device is characterized by comprising the following steps:
s1, receiving the MR analog signal by the local coil unit;
s2, the MR analog signal sequentially passes through the first mixer, the analog-to-digital converter and the digital down converter to obtain an MR digital baseband signal;
s3, the transmitter interweaves, matches the speed and codes the channel to the MR digital baseband signal, obtains the digital signal and maps to the wireless channel;
s4, after OFDM modulation is carried out on the digital signal by the transmitter, a microwave signal is obtained and sent to the wireless air interface;
s5, the receiver receives the microwave signal from the wireless air interface, OFDM demodulation is carried out, and the digital signal carried by the wireless channel is separated;
s6, the receiver carries out channel decoding, rate de-matching and de-interleaving on the digital signal to restore the MR digital baseband signal;
and S7, the MR digital baseband signal sequentially passes through the digital up-converter, the digital-to-analog conversion module and the second mixer to obtain an MR analog signal corresponding to the local coil unit.
2. The method for wireless signal transmission of nuclear magnetic resonance imaging equipment according to claim 1, characterized in that the number of the local coil units is multiple, and the multiple local coil units form a local coil unit array for receiving MR analog signals;
the number of the first frequency mixers, the analog-to-digital converters, the digital down converters, the wireless channels, the digital up converters, the digital-to-analog conversion modules and the second frequency mixers is the same as that of the local coil units.
3. The method according to claim 1, wherein in step S3, the transmitter performs 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, and specifically includes: the interweaving comprises rectangular interweaving and triangular interweaving;
when the interleaving is rectangular interleaving, the size of the data buffer is E multiplied by F Bits, the writing of the MR digital baseband signals is performed according to the sequence from left to right first and then from top to bottom, and the reading of the MR digital baseband signals is performed according to the sequence from top to bottom first and then from left to right;
when the interleaving is triangular interleaving, the size of the data buffer is
The writing of the MR digital baseband signals is performed according to the sequence from left to right and then from top to bottom, and the reading of the MR digital baseband signals is performed according to the sequence from top to bottom and then from left to right.
4. The method according to claim 3, wherein the transmitter rate-matches the MR digital baseband signal, and specifically comprises: the MR digital baseband signal is retransmitted for a plurality of times to match the actual carrying 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 M multiplied by N Bits and the length of a data frame formed by MR digital baseband signals is M Bits, 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 signals, and after repeating the data frame formed by the MR digital baseband signals for N times, channel coding is carried out and the data frame is mapped to a wireless channel;
when the actual bearing capacity of a physical channel is M multiplied by N + A Bits, and the length of a data frame formed by MR digital baseband signals is M Bits, the actual bearing 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 initial A Bits in the data frame to the tail of a data stream, performing channel coding and mapping to a wireless channel.
5. The method according to claim 4, wherein the transmitter performs channel coding on the MR digital baseband signal, and specifically comprises: the transmitter can also transmit real-time control signals, parameter configuration and operation instructions of tuning and detuning required by the local coil;
the transmitter adopts LDPC or Turbo channel coding to MR digital baseband signals, and Polar channel coding is adopted to the transmitter to the real-time control signals, parameter configuration and operation instructions of the local coils which need tuning and detuning.
6. The method according to claim 1, wherein the wireless air interface employs MIMO technology, and the application scale is MIMO X Y, where X represents the number of transmitting antennas, Y represents the number of receiving antennas, the number of transmitting antennas is equal to the number of receiving antennas, and the transmitting antennas and the receiving antennas transmit and receive data at the same time and the same frequency.
7. The method of claim 6, wherein when the number of the transmitting antennas and the number of the receiving antennas are both 2, the wireless transmission comprises the following steps:
t1, the first transmitting antenna sends a demodulation reference signal, the second transmitting antenna keeps silent, and the 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, a first transmitting antenna and a second transmitting antenna transmit data at the same frequency, the two transmitting antennas occupy the same frequency spectrum resource, transmit two independent parallel data streams, and multiplex the frequency spectrum resource for 2 times by using a space division multiplexing technology;
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 is LC00 × h00+ LC01 × h10, RX1_ R is LC00 × h01+ LC01 × h11,
solving a system of linear equations with two variables through matrix operation to obtain separated signals LC00 and LC 01;
t4, separate signals LC00 and LC01 correspond to the MR digital baseband signals received by the first and second local coil units, respectively.
8. The method according to claim 5, wherein the channel decoding of the digital signal by the receiver specifically comprises:
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;
real-time control signals, parameter configuration and operation instructions of tuning and detuning required by the local coil are decoded by adopting Polar channels.
9. The method according to claim 8, wherein the receiver performs de-rate matching on the digital signal, and specifically comprises:
when the actual bearing 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 demodulation likelihood probability values corresponding to the same Bit in the lengths of the N repeated data frames are superposed to obtain the likelihood probability corresponding to the Bit;
when the actual bearing 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 lengths of N repeated data frames are superposed, 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 corresponding to the Bit.
10. The method according to claim 9, wherein the receiver deinterleaves the digital signal, and specifically includes:
when the interweaving is rectangular interweaving, the writing of the digital signals is performed according to the sequence from top to bottom and then from left to right, and the reading of the digital signals is performed according to the 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 according to the sequence from top to bottom and then from left to right, and the reading of the MR digital baseband signals is performed according to the sequence from left to right and then from top to bottom.
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