CN115002723B - Aviation broadband communication method based on 4G/5G frequency spectrum movement - Google Patents
Aviation broadband communication method based on 4G/5G frequency spectrum movement Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/30—Services specially adapted for particular environments, situations or purposes
- H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
- H04W4/42—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for mass transport vehicles, e.g. buses, trains or aircraft
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
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- 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
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- H04L27/2659—Coarse or integer frequency offset determination and synchronisation
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- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/266—Fine or fractional frequency offset determination and synchronisation
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- H04W72/00—Local resource management
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- H04W72/044—Wireless resource allocation based on the type of the allocated resource
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Abstract
The invention discloses an aviation broadband communication method based on 4G/5G spectrum movement, and relates to the technical field of communication. Firstly, constructing a frequency moving device comprising wireless access equipment, a frequency moving module and a wireless terminal, wherein the wireless access equipment firstly transmits downlink signals and simultaneously transmits reserved synchronous signals to the frequency moving module for detection, and if the wireless access equipment is an FDD system, uplink and downlink frequency moving is directly carried out; if the system is a TDD system, the frequency moving module detects the synchronous signal, completes the accurate synchronization of time, further judges the system frame boundary of the wireless frame, and performs time-frequency deviation correction on the PSS and the SSS by using the cyclic prefix. And then demodulating the downlink signal, determining the frame format, and judging the boundary of the uplink and downlink signals. And finally, controlling uplink and downlink time and receiving and transmitting information according to the boundary of the synchronous signal and the uplink and downlink signal, and completing communication. The invention realizes the conversion between the FDD system and the TDD system, and can communicate in any frequency band without changing the prior equipment.
Description
Technical Field
The invention relates to the technical field of communication, in particular to an aviation broadband communication method based on 4G/5G spectrum movement.
Background
With the rapid increase of civil aviation traffic, the volume of civil aviation communication traffic also rapidly increases, and in order to adapt to rapid development of aviation traffic, the International Civil Aviation Organization (ICAO) has issued 6 th edition of Global Air Navigation Program (GANP), and explicitly proposes a specific implementation route of a modern air navigation system, namely Aviation System Block Upgrade (ASBU). It is noted that the roadmap of future aeronautical communication technologies includes new broadband communication technologies for next-generation satellite communications such as airport AeroMACS, way LDACS, and maritime satellites.
The current practical aviation communication technology still stays in the narrow-band communication era, the existing aviation mobile communication equipment needs to be upgraded, although the terminal capability released on the current market is stronger and the supported frequency bands are more and more, the 4G/5G/wireless local area network (RLAN) equipment and even the 6G technology cannot directly work in the aviation frequency band, and some special frequency bands are not in the standard category of 3GPP, or some frequency band 3GPP prescribes to use an FDD system, and the actual use is a TDD system. However, due to the current situation of the communication industry, there are often cases where the device on the radio access network side can support and there are no available terminals, or where the terminals need very high prices for system customization. The method greatly limits the equipment upgrading of the existing aviation mobile communication network and influences the development of civil aviation communication.
Disclosure of Invention
Aiming at the problems, the invention provides an aviation broadband communication method based on 4G/5G frequency spectrum movement, which realizes the utilization of idle frequency bands at low cost and eliminates the limitation of insufficient terminal capability or no corresponding wireless access equipment.
The aviation broadband communication method based on 4G/5G frequency spectrum movement comprises the following specific steps:
step one, constructing a 4G/5G frequency spectrum moving communication device comprising wireless access equipment, a frequency moving module and a wireless terminal, and carrying out uplink and downlink signal frequency moving;
the wireless access equipment and the wireless terminal are respectively connected with the frequency moving module, and the transmission of wireless signals in the uplink and the downlink is realized through the frequency moving module.
The systems to which the wireless access device is applied are classified into FDD systems and TDD systems.
The frequency moving module comprises a synchronization and frame format detection module, a radio frequency transceiver and a local clock module.
The synchronization and frame format detection module is divided into a synchronization detection module and a frame format detection module and is used for receiving a synchronization signal of a downlink signal;
The local clock module and the synchronization and frame format detection module interact to perform synchronization capture calibration and keep track of the synchronization signals.
The radio frequency transceiver amplifies the received signal under the control of the local clock module and transmits the processed signal.
Step two, the wireless access equipment transmits downlink signals, and simultaneously transmits the synchronous signals of the reserved downlink signals to the synchronous and frame format detection module of the frequency moving module for detection;
step three, judging whether a system applied by the wireless access equipment is an FDD system or a TDD system, if the system is the FDD system, entering a step four, otherwise, entering a step five;
Step four, after the downlink signal and the synchronous signal pass through the synchronous detection module, the uplink signal is obtained and transmitted to the radio frequency transceiver, and the uplink signal and the downlink signal are amplified and transmitted to the wireless terminal to finish the frequency shifting of the uplink signal and the downlink signal;
Step five, the synchronization signals finish the accurate synchronization of the PSS and SSS time of the main synchronization signal and the auxiliary synchronization signal through a frame format detection module;
the specific process is as follows:
first, autocorrelation detection is performed on the front half frame and the rear half frame of one system frame of the synchronization signal, and the position of the primary synchronization signal PSS is found.
Then, based on the position where the primary synchronization signal PSS has been detected, detection is performed at a point where the secondary synchronization signal SSS may appear, detecting the secondary synchronization signal SSS position;
Finally, the time domain position interval based on the primary synchronization signal PSS and the secondary synchronization signal SSS is fixed, and accurate synchronization of time is completed.
Step six, the frame format detection module further judges the boundary of the wireless frame in the signal after time synchronization, keeps the boundary aligned, and utilizes the cyclic prefix CP to perform time-frequency deviation correction on the primary and secondary synchronization signals PSS and SSS;
the frequency offset of the signal is divided into an integer multiple of the frequency offset (IFO) and a fractional multiple of the frequency offset (FFO) and a residual frequency offset.
① Frequency Offset (IFO) of integer multiple
The integral multiple frequency offset estimation is carried out by utilizing the primary synchronization signal PSS, and the correlation function is given by assuming that the received signal is r (n)
Wherein d represents a timing pointer, N represents the number of subcarriers of an OFDM symbol, and L is the CP length;
the integer multiple frequency offset estimate is:
d ml is a point where the cyclic prefix is calculated by sliding correlation for a plurality of OFDM symbols, and then the maximum peak value is obtained, where the point is the starting point of the OFDM symbol.
② Fractional Frequency Offset (FFO)
The PSS signal p (n) is divided into a front section and a rear section, and conjugate multiplication is carried out on the PSS signal p (n) without local deviation, so that two sections of new sequences are obtained, namely decimal frequency offset:
③ Residual frequency offset
And training a local clock, and adjusting and training the residual frequency offset by using a phase-locked loop.
Step seven, demodulating the downlink signals to obtain uplink and downlink time distribution under the TDD system, determining a frame format, judging the boundary of the uplink and downlink signals, and maintaining;
Step eight, utilizing the boundary of the synchronous signal and the uplink and downlink signal of the time-frequency deviation correction to accurately switch the downlink signal transmission and the uplink signal reception of the radio frequency transceiver, and controlling the uplink and downlink time through a local clock when the TDD system works; meanwhile, the information receiving and transmitting can be controlled through a local clock, so that a time division multiplexing mode is achieved, the wireless access equipment applying the FDD system is converted into a TDD system, and communication is completed with another TDD system.
And step nine, the signal transmission process is continuously carried out, so that the stability of the system is ensured, and the system can be timely adjusted when the system is changed.
The invention has the advantages that:
1. According to the aviation broadband communication method based on 4G/5G frequency spectrum movement, the constructed 4G/5G frequency spectrum movement communication device carries out frequency up on signals sent by wireless access equipment, and carries out frequency down on the signals at a receiving end, so that communication is carried out in any frequency band under the condition that the existing equipment is not changed.
2. The invention relates to an aviation broadband communication method based on 4G/5G frequency spectrum movement, which uses a local clock module to train and synchronize, uses a clock to control the signal receiving and transmitting of a radio frequency transmitter, and can be converted into a time division multiplexing (TDD) system for signal transmission for a frequency division multiplexing (FDD) system.
Drawings
FIG. 1 is a schematic diagram illustrating the operation of a 4G/5G spectrum shifting communication device according to the present invention;
FIG. 2 is a schematic diagram showing the module configuration and interaction of the 4G/5G spectrum shift communication device according to the present invention;
FIG. 3 is a flow chart of the method of aviation broadband communication based on 4G/5G spectral shifting of the present invention;
FIG. 4 is a flowchart illustrating the operation of the transmitter according to an embodiment of the present invention;
fig. 5 is a flowchart illustrating the operation of the receiver according to an embodiment of the present invention.
Detailed Description
The invention will be further described with reference to the drawings and specific examples.
The invention provides an aviation broadband communication method based on 4G/5G frequency spectrum movement, which is shown in figure 1, and the principle is that the wireless access equipment or the wireless terminal is not modified, the working frequency bands of the wireless access equipment and the wireless terminal are converted into the frequency band to be used in a frequency movement mode, and then signals are amplified and sent to an air interface for transmission.
The constructed aviation broadband communication device based on 4G/5G frequency spectrum movement, as shown in figure 2, comprises wireless access equipment, a frequency movement module and a wireless terminal; and the wireless access equipment and the wireless terminal realize the signal transmission of the uplink and the downlink through the frequency moving module.
The systems to which the wireless access device is applied are classified into FDD systems and TDD systems.
The frequency moving module comprises a local clock module, a synchronization and frame format detection module and a radio frequency transceiver module. The synchronization and frame format detection module is divided into a synchronization detection module and a frame format detection module.
Synchronization and frame format detection module: the signal of the wireless access device is accessed, and whether the wireless access device is a TDD or FDD system is judged. The frequency moving process of moving the signal from the initial frequency to the required frequency needs to perform bidirectional conversion, and if the signal is a frequency division multiplexing (FDD) system, the signal can be directly moved to the uplink and the downlink. If a Time Division Duplex (TDD) system is used, it is considered that an accurate switching between downlink signal transmission and uplink signal reception is performed in a radio frequency transceiver, and a certain guard interval between uplink and downlink is ensured. For TDD, a good synchronization mechanism is required, and the synchronization and frame format detection module needs to perform synchronization signal detection on the wireless access device. The method comprises the steps of detecting synchronous signals of downlink signals sent by wireless access equipment, judging a wireless frame initial boundary, and then demodulating basic system information to obtain definition of a frame format, namely judging the boundary of the downlink signals and the uplink signals, so that accurate switching of the uplink signals and the downlink signals of a radio frequency transceiver is determined.
A local clock module: for maintaining synchronization with the wireless access device and maintaining uplink and downlink formats of the TDD system. The module needs to interact with the synchronization and frame format detection module to perform synchronization acquisition calibration and keep track of the signals of the wireless access device. Another function is to control the transceiving of the radio frequency transmitter module, thereby realizing the mutual conversion between the FDD system and the TDD system.
A radio frequency transceiver module: and sending the signals after frequency moving under the control of the synchronous clock, amplifying and transmitting.
The data transmission route of the whole device is as follows:
Transmitter side: if the system is an FDD system, the signal is directly carried out after being received from the wireless access terminal, and then the signal is sent out from the radio frequency transmitting module. If the system is a TDD system, after the signal is received from the wireless access terminal, the signal is subjected to two operations at the same time, firstly, the signal is subjected to frequency moving, secondly, the signal enters a synchronous detection module to carry out time-frequency synchronization, then a local clock is trained, and after the two operations are completed, the local clock controls a radio frequency module to transmit according to a time slot format obtained by the time-frequency synchronization of the TDD signal.
A receiver end: if the system is an FDD system, the signal is directly carried out frequency moving after being received from an air interface and then is sent to the wireless terminal. If the TDD system signal is received from the wireless access terminal, the signal is processed by two operations at the same time, firstly, the signal is processed by frequency moving, secondly, the signal is processed by time-frequency synchronization by entering the synchronous detection module, then the local clock is trained, and after the two operations are completed, the local clock controls the processed signal to be sent to the wireless terminal according to the time slot format obtained by the time-frequency synchronization of the TDD signal.
The method for performing aviation broadband communication by using the aviation broadband communication device based on 4G/5G spectrum movement is shown in fig. 3, and specifically comprises the following steps:
Step one, the wireless access equipment transmits downlink signals, and simultaneously transmits the reserved synchronization signals of the downlink signals to the synchronization detection module for detection, if the detection results in that the wireless access equipment adopts an FDD system, the downlink signals are directly transmitted to the radio frequency transceiver module through a feeder line after frequency moving, the uplink signals are amplified by the radio frequency transceiver module and then transmitted to the wireless terminal, and the wireless terminal receives the uplink signals from an air interface to finish frequency moving of the uplink signals and the downlink signals; if the wireless access equipment is detected to be applied to the TDD system, the synchronous signal is further transmitted to a frame format detection module.
Step two, a frame format detection module detects the synchronous signals to finish the accurate synchronization of the PSS and SSS time;
The specific process of synchronous signal detection is as follows:
Firstly, the autocorrelation detection is carried out on the front half frame and the rear half frame of one system frame of the synchronous signal, because the PSS is sent periodically, and the PSS has the same content and the same position in different periods, and the position of the PSS is found through the autocorrelation detection.
Then, due to the fixed positions of the PSS and the SSS, based on the position at which the PSS has been detected, detection is performed at a point at which the SSS may occur, detecting the SSS position;
Finally, the time domain position interval based on PSS and SSS is fixed, and accurate synchronization of time is completed.
Step three, for the synchronous signal which completes the accurate time synchronization, the frame format detection module further judges the system frame boundary of the wireless frame of the synchronous signal, keeps the boundary alignment, and utilizes the Cyclic Prefix (CP) to carry out time-frequency deviation correction on the Primary Synchronous Signal (PSS) and the Secondary Synchronous Signal (SSS);
the frequency offset of the signal is divided into an integer multiple of the frequency offset (IFO) and a fractional multiple of the frequency offset (FFO) and a residual frequency offset.
The CP is to take the end of one OFDM symbol and add it to the symbol, it has good auto-correlation, and uses many OFDM symbols to make sliding correlation calculation to the cyclic prefix, the point of the maximum peak is the starting point of one OFDM symbol, recorded as d ml, then uses the maximum likelihood algorithm to complete the symbol time coarse synchronization and frequency domain decimal frequency offset synchronization of the system.
① Frequency Offset (IFO) of integer multiple
Assuming that the received signal is r (n), its correlation function is
The integer multiple frequency offset estimate is:
② Fractional Frequency Offset (FFO)
The PSS is utilized to carry out integral frequency offset estimation, the received PSS signal p (n) is divided into a front section and a rear section, conjugation multiplication is carried out on the received PSS signal p (n) and a local unbiased PSS signal s (n), two sections of new sequences are obtained, and then decimal frequency offset is obtained, namely
③ Residual frequency offset
In practical cases, after FFO and IFO estimation are completed, some frequency offset still exists, and at this time, a local clock needs to be trained, and a phase-locked loop is used for frequency offset adjustment and training.
Demodulating the downlink signal, reading PBCH (Physical Broadcast Channel ) in the middle of bandwidth to obtain PHICH (Physical hybrid ARQ indicator channel, physical HARQ indication channel) and bandwidth information, demodulating according to the information to obtain a System Information Block (SIB), obtaining uplink and downlink time allocation under the TDD system, determining a frame format, judging the boundary of the uplink and downlink signals, and maintaining;
Step five, utilizing the boundary of the synchronous signal and the uplink and downlink signal of the time-frequency deviation correction to accurately switch the downlink signal transmission and the uplink signal reception of the radio frequency transceiver, and controlling the uplink and downlink time through a local clock when the TDD system works; meanwhile, the information receiving and transmitting can be controlled through a local clock, so that a time division multiplexing mode is achieved, the wireless access equipment applying the FDD system is converted into a TDD system, and communication is completed with another TDD system.
The method for converting FDD system and TDD system with each other comprises the following steps:
FDD system to TDD system:
the FDD system uses two different frequency bands to send and receive data, the conversion of the FDD system into the TDD system requires that the two frequency bands are moved to one frequency band, and the bandwidth of the frequency band is ensured to be twice that of the original frequency band so as to ensure that the data transmission rate is not changed. And setting the time ratio of sending and receiving data, and setting a data buffer area for buffering the data. For example, when the original FDD system receives the data to be received, and the TDD system converted by the original system is in the transmission time period, the device caches the received data until the TDD system is in the reception time, and then processes the data from the cache region.
TDD system to FDD system:
the TDD system transmits and receives data in different time periods, and the TDD system is converted into the FDD system, so that the TDD system needs to be moved to one frequency band for operation when receiving, and the TDD system needs to be moved to another frequency band for operation when transmitting.
In order to ensure that the frequency moving module can work normally, the frequency moving module and the wireless access equipment need to perform time-frequency domain synchronization; the frequency moving module detects the synchronous signal sent by the wireless access equipment, continuously performs time-frequency domain deviation correction on the local clock, and ensures the synchronization of the whole system.
And step six, the signal transmission process is continuously carried out, so that the stability of the system is ensured, and the system can be timely adjusted when the system is changed.
The system is simple, and only needs to process according to the standard signal receiving process, so as to analyze the synchronization and broadcast channels of the wireless system.
The technical scheme is further described below by examples.
Examples
The embodiment is to send a self-defined time-frequency domain synchronization and time slot switching signal on the working frequency band. Firstly, the wireless access device needs to reserve bandwidth for time-frequency domain resources of time-frequency domain synchronization and switching signal transmission, and periodically plays the time-frequency domain resources with a wireless frame length as a period. The frequency moving module periodically detects the signal by taking a radio frame as a unit after being started.
As shown in fig. 4, the signal transmission procedure of the wireless access device is processed as follows:
step 1, initializing time-frequency domain resources which need to be reserved after the system is started, and periodically distributing the resources according to intervals of 10 milliseconds;
Step 2, the equipment performs normal baseband and radio frequency processing;
and step 3, inserting a synchronous signal to be transmitted after the radio frequency treatment is finished, finishing signal transmission, and returning to the step 1 for carrying out the next signal transmission process.
The inserted synchronization signal is immediately adjacent to the cyclic prefix, and at the back of the cyclic prefix, it takes the form of 4 synchronization sequences of length N, the first two of which are identical and the last two of which are opposite in sign. The content of the synchronization signal includes the slot format of the signal and other system information.
The terminal receiving process is similar to the overall processing flow, but because the frame format is carried in the inserted time-frequency domain synchronizing signal, the downlink signal does not need to be further demodulated, the uplink and downlink proportion of a wireless frame can be known only through continuous synchronizing signal detection, and the frame boundary is simpler to realize.
As shown in fig. 5, the specific processing procedure of the terminal is as follows:
step 1, receiving downlink signals of wireless access equipment, wherein a frequency moving module at an equipment end receives the downlink signals from the wireless access equipment through a feeder line, and for a wireless terminal, receiving the downlink signals from an air interface;
step 2, the wireless access device and the wireless terminal detect the synchronous signals, and when the inserted synchronous signals are detected, the specific method is similar to that of checking the SSS and PSS signals, and the initial position of the synchronous signals can be accurately known by utilizing autocorrelation detection because only symbol differences exist in 4 parts of the inserted synchronous signals.
Step 3, in order to enable the system to work stably and reliably, time-frequency domain deviation correction is needed, and the local clock is continuously trained.
The signal synchronization method is as follows:
step 301 assumes that r (n) represents the received time domain signal, and may set a function
Wherein R (m) is the sum of the sampled correlation functions separated by N points, and the function is resetRepresenting the energy sum of the synchronization signal halves.
The timing function isWhen G (m) takes the maximum value, the corresponding m is the optimal timing synchronization.
In step 302, when the frequency offset is determined, it is known that r * (N-d) r (N-d+n) is represented by the transmission signal s (N), and r (N) =s (N-d) e jnf is obtained by taking the above formula
s*(n-d)e-j(n-d)fs(n-d+N)ej(n-d+N)f＝|s(n-d)|2ejNf
Where f is the frequency offset and where,
When R (m) is obtained in step 301, the frequency domain offset of the system is θ=arg [ R (m) ].
Step 303 is that in actual situations, some frequency offset still exists in the system, and at this time, the local clock needs to be trained, and the phase-locked loop is used for frequency offset adjustment and training.
Step 4, after determining the boundary between the synchronous signal and the uplink and downlink signals, the accurate switch of the downlink signal transmission and the uplink signal reception of the radio frequency transceiver can be realized, and when the TDD system works, the local clock is required to control the uplink and downlink time; when the device is expected to convert an FDD system into a TDD system and communicate with another TDD system, a local clock is also needed to control the information receiving and transmitting to achieve a time division multiplexing form.
The process described above in step 5 continues to ensure the stability of the system and to allow for timely adjustment when the system changes.
Claims (4)
1. An aviation broadband communication method based on 4G/5G frequency spectrum movement is characterized by comprising the following specific steps:
step one, constructing a 4G/5G frequency spectrum moving communication device comprising wireless access equipment, a frequency moving module and a wireless terminal, and carrying out uplink and downlink signal frequency moving;
The wireless access equipment and the wireless terminal are respectively connected with the frequency moving module, and the transmission of wireless signals in an uplink and a downlink is realized through the frequency moving module;
Step two, the wireless access equipment transmits downlink signals, and simultaneously transmits the synchronous signals of the reserved downlink signals to the synchronous and frame format detection module of the frequency moving module for detection;
step three, judging whether a system applied by the wireless access equipment is an FDD system or a TDD system, if the system is the FDD system, entering a step four, otherwise, entering a step five;
Step four, after the downlink signal and the synchronous signal pass through the synchronous detection module, the downlink signal obtains an uplink signal through frequency shifting and transmits the uplink signal to the radio frequency transceiver, and the uplink signal and the downlink signal are amplified and transmitted to the wireless terminal to finish frequency shifting of the uplink signal and the downlink signal;
Step five, the synchronization signals finish the accurate synchronization of the PSS and SSS time of the main synchronization signal and the auxiliary synchronization signal through a frame format detection module;
Step six, the frame format detection module further judges the boundary of the wireless frame in the signal after time synchronization, keeps the boundary aligned, and utilizes the cyclic prefix CP to perform time-frequency deviation correction on the primary and secondary synchronization signals PSS and SSS;
The specific process of time-frequency deviation correction is as follows:
The frequency offset of the signal is divided into an integer multiple of frequency offset IFO and a fractional multiple of frequency offset FFO and residual frequency offset;
① Frequency offset IFO of integer multiple
The integral multiple frequency offset estimation is carried out by utilizing the primary synchronization signal PSS, and the correlation function is given by assuming that the received signal is r (n)
Wherein d represents a timing pointer, N represents the number of subcarriers of an OFDM symbol, and L is the CP length;
the integer multiple frequency offset estimate is:
d ml is a point of maximum peak value obtained after sliding correlation calculation is performed on the cyclic prefix by a plurality of OFDM symbols, and the point is a starting point of the OFDM symbols;
② Fractional frequency offset FFO
The PSS signal p (n) is divided into a front section and a rear section, and conjugate multiplication is carried out on the PSS signal p (n) without local deviation, so that two sections of new sequences are obtained, namely decimal frequency offset:
③ Residual frequency offset
Training a local clock, and adjusting and training residual frequency offset by using a phase-locked loop;
step seven, demodulating the downlink signals to obtain uplink and downlink time distribution under the TDD system, determining a frame format, judging the boundary of the uplink and downlink signals, and maintaining;
step eight, utilizing the boundary of the synchronous signal and the uplink and downlink signal of the time-frequency deviation correction to accurately switch the downlink signal transmission and the uplink signal reception of the radio frequency transceiver, and controlling the uplink and downlink time through a local clock when the TDD system works; meanwhile, the information receiving and transmitting can be controlled through a local clock, so that a time division multiplexing mode is achieved, the wireless access equipment applying the FDD system is converted into a TDD system, and the wireless access equipment and another TDD system are communicated;
And step nine, the signal transmission process is continuously carried out, so that the stability of the system is ensured, and the system can be timely adjusted when the system is changed.
2. The method for aviation broadband communication based on 4G/5G spectrum shift according to claim 1, wherein the wireless access device application system is divided into an FDD system and a TDD system.
3. The method for aviation broadband communication based on 4G/5G spectrum shift according to claim 1, wherein the shift module comprises a synchronization and frame format detection module, a radio frequency transceiver and a local clock module;
the synchronization and frame format detection module is divided into a synchronization detection module and a frame format detection module and is used for receiving a synchronization signal of a downlink signal;
the local clock module and the synchronization and frame format detection module interact to carry out synchronization capture calibration and tracking on the synchronization signals;
The radio frequency transceiver amplifies the received signal under the control of the local clock module and transmits the processed signal.
4. The aviation broadband communication method based on 4G/5G spectrum shift according to claim 1, wherein the precise synchronization of the primary and secondary synchronization signals PSS and SSS time is implemented by:
firstly, performing autocorrelation detection on front half frames and rear half frames of a system frame of a synchronous signal to find the position of a main synchronous signal PSS;
Then, based on the position where the primary synchronization signal PSS has been detected, detection is performed at a point where the secondary synchronization signal SSS may appear, detecting the secondary synchronization signal SSS position;
Finally, the time domain position interval based on the primary synchronization signal PSS and the secondary synchronization signal SSS is fixed, and accurate synchronization of time is completed.
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