WO2022033028A1 - Système de transmission sans fil de signal multicanal et procédé de commande de distribution de grille de ressources physiques - Google Patents

Système de transmission sans fil de signal multicanal et procédé de commande de distribution de grille de ressources physiques Download PDF

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WO2022033028A1
WO2022033028A1 PCT/CN2021/081071 CN2021081071W WO2022033028A1 WO 2022033028 A1 WO2022033028 A1 WO 2022033028A1 CN 2021081071 W CN2021081071 W CN 2021081071W WO 2022033028 A1 WO2022033028 A1 WO 2022033028A1
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module
local coil
signal
channel
sub
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Chinese (zh)
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杜健军
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深圳市一康云智慧科技有限责任公司
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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
    • 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
    • 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
    • H04L27/2657—Carrier 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
    • H04L27/2662—Symbol synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
    • 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

Definitions

  • the invention relates to the technical field of nuclear magnetic resonance medical imaging equipment, in particular to a multi-channel signal wireless transmission system and a control method for physical resource grid allocation.
  • nuclei can be transformed from a high-energy state to a low-energy state in a non-radiative manner. This process is called relaxation.
  • relaxation There are two types of relaxation: longitudinal relaxation and transverse relaxation.
  • the nuclear magnetic resonance signal receiving system is very important. Its function is to receive the energy released by the relaxation in the form of electromagnetic waves, which is used for the later image reconstruction of the system.
  • International and domestic manufacturers, the current MRI equipment, and the transmission link of the receiving system involve the following processes:
  • Front-end processing of analog signals requires the design of complex and cumbersome circuits to ensure distortion-free transmission (flat amplitude-frequency characteristic curve and fixed phase-frequency characteristic curve group delay) under different gain conditions, resulting in the production cost of MRI equipment Very high, the production efficiency is reduced, and the consistency between individual equipment becomes worse;
  • the connector between the receiving coil and the system needs: special structure and surface distortion-free transmission processing (such as gold plating), and because the connector has many contact points (pins, gold fingers and other contact methods), so High cost and limited service life;
  • the invention provides a multi-channel signal wireless transmission system for a nuclear magnetic resonance medical imaging system, which integrates the software radio SDR idea, extracts its core framework, performs adaptation and optimization; Real-time acquisition, front-end processing, spectrum shifting, virtual ID air interface channel selection, receiver coil tuning and detuning real-time control, etc., to define and implement the full-link architecture. It has the characteristics of high dynamic range, ultra-low distortion transmission, and zero jitter in the receiving link delay time; and the system has a simplified structure, low production cost, and high production efficiency; at the same time, during the operation of the MRI equipment, each coil receives signals. , which supports flexible dynamic synthesis in terms of magnitude and phase.
  • a multi-channel signal wireless transmission system for a nuclear magnetic resonance medical imaging system comprising a transmitter and a receiver, the transmitter comprising a local coil unit, a physical resource grid mapping a unit module, a signal collection module, a synthesis and modulation module, the receiver includes a wireless reception module, a synchronization module, a demodulation module, and an output interface, wherein the physical resource grid mapping unit includes a physical resource grid;
  • the local coil unit collects and transmits signals, wherein the number of the local coil units is multiple, each local coil unit has an ID identification number, the multiple local coil units are randomly combined into multiple groups, and the ID identification number The number is freely allocated by the system;
  • the physical resource grid consists of multiple resource blocks. Each row of resource blocks forms a sub-channel or sub-carrier.
  • the available wireless air interface resources are allocated to the local coil according to the ID number of the local coil unit.
  • the other groups of local coil units release their occupied sub-channels and keep silent;
  • the signal collection module is used to collect the signal collected by the local coil unit
  • the synthesis and modulation module synthesizes the signals collected by the local coil unit, modulates the synthesized signals by orthogonal frequency division multiplexing, and distributes them to the output interface;
  • the physical resource grid mapping unit module maps the modulated signal to the corresponding sub-channel frequency point according to the wireless air interface resources of the local coil unit;
  • a wireless receiving module receiving modulated signals through a wireless air interface, wherein the number of the wireless receiving modules is multiple;
  • the synchronization module performs carrier frequency synchronization and symbol synchronization on the modulated signal received by the output interface
  • the demodulation module adopts orthogonal frequency division multiplexing to demodulate the synchronized modulated signal to obtain the signal carried by each sub-channel;
  • the output interface the signal is transmitted to the image reconstruction system or the magnet room in the form of optical fiber, electrical, digital and analog through the output interface.
  • the rule that the local coil unit occupies the sub-channel is: when the local coil unit is activated, according to the activated local coil unit ID identification number and the wireless spectrum resources currently allowed to be allocated, the sub-channel physical resources are dynamically allocated in combination with the channel quality. to the corresponding local coil unit.
  • the signal collected by the local coil unit is an MR baseband signal
  • the signal collection module includes an analog-to-digital conversion module and a digital down-conversion module
  • the analog-to-digital conversion module converts the MR baseband signal output by the local coil unit from an analog signal to a digital signal
  • the digital down-conversion module digitally down-converts the converted MR digital signal to a digital baseband.
  • the signal collection module is a scan sequence module, and the scan sequence module is used to scan the real-time control signals for tuning and detuning of the local coil.
  • the synthesis and modulation module includes a convergence unit and a modulation unit, or a complex weighted sum unit and a modulation unit; the convergence unit gathers the signals collected by the local coil unit according to the ID identification number and the sub-channel frequency point position, and passes the digital signal together. The method is assigned to the output interface; the complex weighted sum module performs complex weighted sum of the signals collected by the local coil unit, and then assigns it to the output interface.
  • the physical resource grid specifies dedicated sub-channels for demodulation reference signals, phase tracking reference signals, and sounding reference signals, respectively;
  • the remaining sub-channels are used to carry the MR baseband signal of the MRI, the device status indication, the alarm information, and the feedback response signal;
  • the remaining sub-channels are used to carry real-time control signals, parameter configuration, and operation instructions for tuning and detuning of the local coil.
  • the synthesis and modulation module performs serial-parallel transformation, synthesis, and OFDM modulation on the signals collected by the local coil unit through IFFT transformation, and sends them out in the form of superimposed waveforms in the air.
  • the synchronization module includes a carrier frequency synchronization unit and a symbol synchronization unit, and the carrier frequency synchronization unit performs real-time tracking on the center frequency of the phase tracking reference signal transmitted by the transmitter, and the center frequency and the phase tracking reference signal are tracked in real time.
  • the carrier frequency offset is obtained by comparing the ideal values, and the carrier frequency offset is compensated and phase adjusted in real time;
  • the symbol synchronization unit analyzes the starting position of the OFDM symbol data part through the log-likelihood ratio algorithm and the autocorrelation detection algorithm, and realizes Symbol synchronization.
  • the demodulation module performs parallel-serial transformation, separation, and OFDM demodulation on the superimposed waveform in the air through FFT transformation to obtain signals carried by each sub-channel.
  • the present invention also provides a method for controlling dynamic allocation of physical resource grids in a nuclear magnetic resonance medical imaging system, comprising the following steps:
  • step S1 detect whether the local coil unit is activated, if so, go to step S2, if not, continue to detect;
  • step S3 detect whether the spectrum resource has surplus, if yes, then go to step S4, if not, go to step S9;
  • step S4 detect whether the modulation order Qm is the lowest, if not, then go to step S5, if so, go to step S7;
  • the modulation order Qm is reduced, thereby increasing the occupied spectrum resources
  • step S6 detect whether the spectrum resource has surplus, if yes, then return to step S4, if not, then enter step S9;
  • step S7 detect whether the spectrum resource has surplus, if yes, then go to step S8, if not, go to step S9;
  • the present invention extracts the concept of the wireless communication network air interface physical resource grid, and dynamically allocates the available wireless air interface resources to the corresponding local coil units based on the ID identification number.
  • the local coil unit When the local coil unit is activated, it is allowed to Occupy the corresponding sub-channel to transmit the collected signal; when the local coil unit is deactivated, release the corresponding sub-channel occupied by it and keep silent, which can save and allocate wireless spectrum resources, and at the receiving end can be based on ID identification number , sub-channel frequency point position, flexibly realize the function of tracking and selection of the receiving coil channel, freely assign the signal to the corresponding output interface, and avoid the channel characteristic difference and signal distortion and distortion introduced by the use of radio frequency electronic switches.
  • DMRS demodulation reference signal
  • PTRS phase tracking reference signal
  • SRS sounding reference signal
  • the digitized signal adopts the OFDM modulation and demodulation method, the bandwidth utilization rate is high, the spectrums between adjacent sub-channels overlap each other, and the frequency selective fading is small, and the time selective fading is small.
  • FIG. 1 is a block diagram of an uplink according to Embodiment 1 of the present invention.
  • FIG. 2 is a block diagram of a downlink according to Embodiment 2 of the present invention.
  • FIG. 3 is a schematic diagram of the division of a local coil unit and a physical resource grid in Embodiment 1 of the present invention
  • Embodiment 4 is a schematic diagram of two scenarios of grid division of local coil units and physical resources in Embodiment 1 of the present invention
  • Embodiment 1 of the present invention is a schematic diagram of physical resource grid division in Embodiment 1 of the present invention.
  • Embodiment 6 is a flowchart of dynamic allocation of physical resource grids in Embodiment 1 of the present invention.
  • FIG. 7 is a schematic diagram of freely assigning output interfaces in a digital manner in Embodiment 1 of the present invention.
  • Embodiment 8 is a schematic diagram of instantiation of a digital pattern matrix in Embodiment 1 of the present invention.
  • Embodiment 9 is a schematic diagram of OFDM modulation and demodulation in Embodiment 1 of the present invention.
  • FIG. 10 is a schematic diagram of a comparison between traditional frequency division multiplexing and orthogonal frequency division multiplexing in Embodiment 1 of the present invention.
  • FIG. 11 is a schematic diagram of carrier frequency synchronization in Embodiment 1 of the present invention.
  • FIG. 12 is a schematic diagram of an OFDM symbol of an observation window in Embodiment 1 of the present invention.
  • FIG. 13 is a schematic structural diagram of autocorrelation detection in Embodiment 1 of the present invention.
  • FIG. 14 is a waveform diagram of the output signal of the L-point integrator in the first embodiment of the present invention.
  • the present invention provides a multi-channel signal wireless transmission system for a nuclear magnetic resonance medical imaging system, specifically a multi-channel MR signal wireless transmission system based on a wireless communication network 4GLTE/5GNewRadio/WLANWIFI and software-defined radio SDR technology, As shown in Figure 1, the present invention includes a transmitter and a receiver.
  • the uplink is the wireless transmission of MR magnetic resonance signals, from the magnet room (ward) to the image reconstruction system (doctor). side).
  • the transmitter includes a local coil unit, a physical resource grid mapping unit module, an analog-to-digital conversion module, a digital down-conversion module, a synthesis and modulation module, and the receiver includes a wireless receiving module, a synchronization module, a demodulation module, Output interface, where the physical resource grid mapping unit module contains the physical resource grid.
  • the local coil unit collects and transmits MR digital baseband signals, wherein the number of local coil units is multiple (1 to 128), each local coil unit has an ID identification number, and multiple local coil units are randomly combined into multiple groups , the ID identification number is freely assigned by the system.
  • the physical resource grid consists of 1 to 128 resource blocks. Each row of resource blocks forms a sub-channel.
  • the available wireless air interface resources are allocated to the local coil unit according to the ID number of the local coil unit. , and occupy the sub-channel to transmit signals.
  • the other group of local coil units releases the occupied sub-channel and keeps silent.
  • the traditional NMR local coil receiving array requires a receiving coil channel selection module; as the scale of the local coil receiving array increases, the RF electronic switches used in RCCS become larger and larger, and the difference in channel characteristics between different channels becomes more and more obvious. , the whole system becomes bulky, and it takes a lot of energy to compensate for the difference in channel characteristics in the production process; at the same time, the RF electronic switch will also cause distortion and distortion of the MR baseband signal.
  • This embodiment extracts the concept of the wireless communication network air interface physical resource grid, and divides the local coil units into two groups. As shown in FIG. 3, the local coil units 1/2/3/4/7 are a group. When the coil unit No. 1/2/3/4/7 is activated, the image reconstruction system dynamically allocates the corresponding ID number based on the currently available wireless air interface resources (international license-free frequency band: 2.4G to 2.485G). The local coil unit allows it to occupy the corresponding sub-channel (sub-carrier) to transmit the MR digital baseband signal it has collected.
  • the resource grid of the physical layer is composed of resource blocks, of which the local coil unit 01 occupies 2 resource blocks in the frequency domain, and the corresponding frequency band is 2.475G to 2.485G; the local coil unit 02 is in the 3 resource blocks are occupied in the frequency domain, and the corresponding frequency band is 2.46G to 2.475G; the local coil unit 03 occupies 2 resource blocks in the frequency domain, and the corresponding frequency band is 2.45G to 2.46G; the local coil unit 04 is in the frequency domain. It occupies 1 resource block in the frequency domain, and the corresponding frequency band is 2.425G to 2.43G; the local coil unit 07 occupies 5 resource blocks in the frequency domain, and the corresponding frequency band is 2.4G to 2.425G.
  • the resource grid is in the time domain, and each The duration of the resource block is 2.4us.
  • FIG. 10 shows the application of two sets of local coil units in different scenarios. 10 is a group.
  • Scenario 1 When the local coil unit 1/2/3/4/7 is activated, it is allowed to occupy the corresponding sub-channel (sub-carrier) to transmit the MR digital baseband signal it has collected; local coil unit 5/6/ On 8/9/10, the corresponding sub-channel (sub-carrier) occupied by it is released and kept silent.
  • Scenario 2 When the local coil unit No. 5/6/8/9/10 is activated, it is allowed to occupy the corresponding sub-channel (sub-carrier) to transmit the MR digital baseband signal collected by it; the local coil unit 1/2/ No. 3/4/7 releases the corresponding sub-channel (sub-carrier) occupied by it, and keeps silent.
  • the advantage of this is that the existing wireless spectrum resources can be fully utilized.
  • An analog-to-digital conversion module which converts the MR baseband signal output by the local coil unit from an analog signal to a digital signal
  • the digital down-conversion module digitally down-converts the MR digital signal converted into a digital signal to a digital baseband and outputs it to the synthesis and modulation module.
  • the radio frequency electronic switches used in the RCCS at the receiving end are getting larger and larger, the difference in channel characteristics between different channels is becoming more and more obvious, and the whole system becomes cumbersome (if it is necessary to implement M local coil units to The allocation of N output interfaces needs to involve M*N transmission paths), which requires a lot of energy to compensate for the difference in channel characteristics during the production process; at the same time, it is difficult to avoid the MR baseband signal distortion introduced by the RF electronic switch array. and distortion.
  • a synthesis and modulation module is used to synthesize the signals collected by the local coil unit, the synthesized signals are modulated by orthogonal frequency division multiplexing, and distributed to the output interface;
  • the synthesis and modulation module includes a convergence unit and a modulation unit;
  • the aggregation unit aggregates all the digital baseband signals of the activated local coil unit MR received by the wireless air interface, and freely distributes them to the output interface by digital means. If the assignment of M local coil units to N output interfaces is to be realized, it only needs to be flexibly realized through software programs inside the processor FPGA/ARM/DSP, and the physical entity of the RCCS components is no longer involved.
  • the synthesis and modulation module in this embodiment may also include a complex weighted sum unit and a modulation unit, and a digital mode matrix is introduced to convert the After complex weighted summation is performed on the MR baseband signals of different local coil units, they are freely distributed to the corresponding output interfaces.
  • the nuclear magnetic resonance medical imaging device no longer needs the physical entity of the channel selection component of the receiving coil, and no longer involves compensating for differences in RCCS channel characteristics, thereby reducing hardware and production costs.
  • FIG. 8 is a digital pattern matrix 2X2/3X3/4X4 respectively, wherein the digital pattern matrix is N ⁇ N, and the larger N is, the higher the integration degree is.
  • Orthogonal frequency division multiplexing OFDM is a multi-carrier transmission method, which is based on the high abstraction and generalization of wireless communication network 4GLTE/5GNewRadio/WLANWIFI and software-defined radio SDR technology. Compared with single-carrier transmission, the frequency domain is divided into For multiple sub-channels, data is transmitted in parallel using multiple carriers. The adjacent sub-channels overlap each other in spectrum, but the channels are mutually orthogonal, so channel separation and data recovery can still be performed at the receiving end.
  • the wireless communication system of this embodiment can decompose the high-speed serial data stream into several parallel low-speed sub-data streams for simultaneous transmission.
  • the MR digital baseband signals received by multiple local coil unit arrays are carried at the transmitting end, and are respectively mapped to a1, a2...ak sub-channels (sub-carriers), and then implemented by IFFT transformation.
  • the serial-to-parallel conversion and synthesis of multiple sub-carrier signals are then sent out in the form of superimposed waveforms in the air.
  • FIG. 10 is a schematic diagram showing the comparison between traditional frequency division multiplexing and orthogonal frequency division multiplexing.
  • the digitized MR baseband signal through OFDM modulation and demodulation, has the following Advantage:
  • the time-selective fading is small, the duration of the OFDM symbol ⁇ the "coherence time" of the channel, and the channel can be equivalent to a "linear time-invariant" system, reducing the influence of the channel time-selective fading on the wireless transmission system.
  • the physical resource grid mapping unit module maps the MR digital baseband signals to corresponding sub-channel (sub-carrier) frequency points according to the wireless air interface resources of the local coil unit.
  • Figure 5 shows a schematic diagram of the division of the physical resource grid.
  • the physical resource grid diagram on the left of Figure 5 shows that the spectrum resources of the traditional wireless communication network are extremely tight.
  • some bits and pieces such as demodulation reference signal (DMRS), phase tracking reference signal (PTRS), sounding reference signal (SRS) are placed, and the remaining resource blocks are used to transmit valid information.
  • DMRS demodulation reference signal
  • PTRS phase tracking reference signal
  • SRS sounding reference signal
  • special dedicated sub-channels sub-carriers
  • DMRS demodulation reference signals
  • sub-carriers are used to carry MR baseband signals for MRI, device status indication , alarm information, feedback response signal.
  • demodulation reference signal DMRS
  • phase tracking reference signal PTRS
  • SRS sounding reference signal
  • FIG. 6 shows the flow chart of dynamic request and allocation of physical resource grid, and the steps are as follows:
  • step S1 detect whether the local coil unit is activated, if so, go to step S2, if not, continue to detect;
  • step S3 detect whether the spectrum resource has surplus, if yes, then go to step S4, if not, go to step S9;
  • step S4 detect whether the modulation order Qm is the lowest, if not, then go to step S5, if so, go to step S7;
  • the modulation order Qm is reduced, thereby increasing the occupied spectrum resources
  • step S6 detect whether the spectrum resource has surplus, if yes, then return to step S4, if not, then enter step S9;
  • step S7 detect whether the spectrum resource has surplus, if yes, then go to step S8, if not, go to step S9;
  • the basic resource block required for transmitting the MR baseband signal will be allocated first, and it is at the highest modulation order Qm.
  • the channel decoding module It will judge whether there is a bit error, so as to make a corresponding decision (normal scanning/stop scanning); if it is found that there is still a surplus of spectrum resources, the modulation order Qm will be reduced, and the strength of repeated backup and synthesis of multiple subcarriers will be improved.
  • the channel decoding module will judge whether there is a bit error, so as to make a corresponding decision (normal scanning/stop scanning).
  • the wireless receiving module receives the modulated signal through the wireless air interface. As shown in FIG. 7 and FIG. 8 , the number of output interfaces in this embodiment is 16.
  • the synchronization module includes a carrier frequency synchronization unit and a symbol synchronization unit, and performs carrier frequency synchronization and symbol synchronization on the modulated signal received by the output interface.
  • the carrier frequency synchronization unit performs real-time tracking on the center frequency point of the phase tracking reference signal transmitted by the transmitter, so as to realize the frequency offset detection, and compares the center frequency point of the phase tracking reference signal with the ideal value to obtain the carrier frequency offset.
  • the offset is compensated and phase adjusted in real time, so that the receiver is dynamically balanced relative to the carrier frequency of the transmitter.
  • Figure 11 shows a block diagram of carrier frequency synchronization.
  • the transmitter uses a dedicated sub-channel (sub-carrier) to transmit a phase tracking reference signal (PTRS), and the original data obtained by the receiver after sampling is stored in the buffer. Inside, and then perform FFT to track the center frequency of the PTRS signal in real time.
  • PTRS phase tracking reference signal
  • the carrier frequency synchronization unit compares center frequency point of the PTRS signal with the ideal value to obtain the carrier frequency offset.
  • the carrier frequency synchronization unit controls the voltage-controlled oscillator through the output signal, so that the carrier frequency of the receiver is dynamically balanced relative to the transmitter.
  • the symbol synchronization unit analyzes the starting position of the data part of the OFDM symbol through the log-likelihood ratio algorithm and the autocorrelation detection algorithm, and realizes the symbol synchronization.
  • symbol synchronization The purpose of symbol synchronization is that the receiver can correctly analyze and locate the cyclic prefix of each OFDM symbol and the starting position of the modulated data, which is a prerequisite for correct FFT operation and demodulation.
  • Symbol synchronization is performed based on the cyclic prefix.
  • the OFDM system introduces the cyclic prefix as a guard interval.
  • the cyclic prefix repeats the data at the end of the modulation data. Strong correlation, the OFDM symbol synchronization algorithm uses this correlation to locate.
  • This embodiment adopts the maximum likelihood algorithm, proposes a maximum correlation principle algorithm based on energy integration, and adopts the method of averaging multiple OFDM symbols to improve its synchronization performance.
  • the original data obtained by the receiver after sampling by the ADC is stored in the buffer, and the observation window contains M OFDM symbols. 128/256/512/1024/2048/4096/8912/16384/32768, etc.), where an OFDM symbol includes a cyclic prefix and modulation data, the length of the cyclic prefix is L, and the length of the modulation data is N; since the cyclic prefix is The data at the end of the modulated data is repeated, so the structure shown in Figure 13 is used for autocorrelation detection, the original data is delayed by N sampling points, and the data delayed by N sampling points is multiplied by the original data through a length L point integrator
  • the output signal, the output signal (maximum likelihood function) waveform of the L-point integrator is shown in Figure 14, the period is exactly equal to the sum of the length of the cyclic prefix and the modulated data in the OFDM symbol (N+L), the peak value of the maximum likelihood function
  • the time point corresponds to the cyclic prefix of the
  • the demodulation module uses orthogonal frequency division multiplexing to demodulate the synchronized modulated signal to obtain the signal carried by each sub-channel.
  • the serial-to-parallel transformation and separation of the superimposed waveforms in the air can be realized by FFT transformation at the receiving end, and the MR digital baseband signals a1 and a2 carried by each sub-channel (sub-carrier) are obtained respectively. ...ak.
  • the MR digital baseband signal is transmitted to the image reconstruction system in the form of optical fiber, electrical, digital, analog, etc. through the output interface.
  • the transmission link of the system is the downlink.
  • the downlink is the real-time control signal for tuning and detuning required by the MR local coil. Reconstruct the system (doctor side) to the magnet room (ward).
  • the transmitter includes a local coil unit, a physical resource grid mapping unit module, a scanning sequence module, a synthesis and modulation module, and the receiver includes a wireless receiving module, a synchronization module, a demodulation module, and an output interface.
  • the scan sequence module is used to scan the real-time control signals for the desired tuning and detuning of the local coils.
  • the physical resource grid specifies dedicated subchannels for demodulation reference signals, phase tracking reference signals, and sounding reference signals; when the system transmission link is downlink, the remaining subchannels are used for carrying Real-time control signals, parameter configuration, and operating instructions for tuning and detuning of local coils.
  • Output interface the real-time control signal for tuning and detuning of the local coil is transmitted to the magnet room (ward) through the output interface in the form of optical fiber, electrical, digital, analog, etc.
  • Both this embodiment and the first embodiment use the wireless communication private network for transmission, and the specific form adopts the key technologies involved in 4GLTE/5GNR/WLAN, etc., and integrates the protocol standards of 3GPP/IEEE in the field of wireless communication (3GPP4GLTE/5GNR/WLANIEEE802 .11b/a/g/n/ac/ax), apply MIMO, OFDM, channel coding technology and software radio SDR idea, extract its core framework, carry out adaptation and optimization, and closely integrate the multi-channel of current MRI equipment
  • the wireless signal receiving system can simultaneously perform real-time acquisition, front-end processing, spectrum shifting, virtual ID air interface channel selection, receiving coil tuning and detuning real-time control for 1 to 128 channels of NMR signals, and carry out full-link architecture definition and specific accomplish.

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  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

La présente invention concerne un système de transmission sans fil de signal multicanal et un procédé de commande de distribution de réseau de ressources physiques, comprenant un émetteur et un récepteur. L'émetteur comprend des unités de bobine locale, un module d'unité de mise en correspondance de grille de ressources physiques, un module de collecte de signal, un module de synthèse et de modulation, et un module de mise en correspondance, et le récepteur comprend des modules de réception sans fil, un module de synchronisation, un module de démodulation et des interfaces de sortie. Les unités de bobine locale sont utilisées pour acquérir des signaux; le module de collecte de signaux est utilisé pour collecter les signaux; le module de synthèse et de modulation est utilisé pour synthétiser et moduler les signaux acquis; le module de mise en correspondance est utilisé pour mettre en correspondance les signaux modulés; le module de synchronisation est utilisé pour synchroniser les signaux modulés; le module de démodulation est utilisé pour démoduler les signaux synchronisés. Selon le système fourni par la présente invention, l'acquisition en temps réel, le traitement frontal, la fréquence de décalage du spectre de fréquence, la sélection du canal d'interface radio d'ID virtuel, la réception d'un réglage de bobine, la commande en temps réel de déréglage et autre peuvent être réalisés sur des trajets 1-128 de signaux de résonance magnétique nucléaire simultanément, le cadre du système est simplifié, le coût de production est faible, et l'efficacité de production est élevée.
PCT/CN2021/081071 2020-08-14 2021-03-16 Système de transmission sans fil de signal multicanal et procédé de commande de distribution de grille de ressources physiques WO2022033028A1 (fr)

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