Frequency synchronization method for 5G FDD stock mobile phone direct connection satellite

Abstract

The invention discloses a frequency synchronization method for 5G FDD stock mobile phone direct connection satellites. The method mainly solves the problems that mobile phones need to be changed when the mobile phone direct connection satellites are carried out in the prior art, and the beam range is limited by frequency correction. The implementation scheme is as follows: a base station performs integer frequency offset pre-compensation on each SSB in an SSB burst set and a corresponding SIB1; creating different preamble detection windows according to preamble opportunities after the random access is initiated; a base station adjusts frequency domain resource allocation of uplink and downlink signals of random access and service transmission based on a satellite scheduling algorithm, integer frequency offset compensation is carried out on the uplink and downlink signals in a resource lattice offset mode, the uplink and downlink signals are not biased as far as possible in combination with the frequency offset compensation amount of a stock mobile phone, and frequency synchronization in the connection process of the 5G mobile phone and a satellite is completed. According to the method, the limitation on the beam range during frequency synchronization can be reduced, the mobile phone is prevented from being changed, the technical standard of the current stock mobile phone is adapted, and the method can be used for the satellite communication service of the 5G mobile phone.

Description

Technical Field

[0001] The present invention belongs to the field of satellite communication technology, and mainly relates to a frequency synchronization method for an existing 5G mobile phone to directly connect to a satellite under an FDD system, which can be used for satellite communication services of 5G mobile phones. Background Art

[0002] In recent years, with the popularity of smart phones and the rapid development of satellite launch technology, mobile communications are evolving towards satellite-ground integration. Direct mobile phone satellite communications can get rid of geographical restrictions and achieve global coverage. However, due to the high speed and large coverage of satellites, the channel between satellites and mobile terminals has a serious Doppler effect, which affects the normal data transmission between terminals and satellites.

[0003] In order to solve the problem of Doppler frequency shift, the existing technical solution is to make additional modifications to the terminal. For example, a chip that adapts to the satellite system protocol is added to the mobile phone, so that the terminal can obtain ephemeris information and its own position information in real time to compensate for the Doppler frequency shift in satellite-to-ground communication. Currently, Huawei mobile phones + Beidou satellites, Huawei mobile phones + Tiantong satellites, Apple mobile phones + Globalstar, etc. use this method.

[0004] The non-terrestrial network (NTN) project hosted by the 3rd Generation Partnership Project (3GPP) has also carried out a lot of research and standardization work on satellite-to-earth communications. It has now completed the freezing of Rel-17 and Rel-18 standards. It has designed an air interface enhancement protocol and introduced a variety of enhancement technologies, which can effectively solve the large frequency deviation problem in satellite communication scenarios.

[0005] However, all of the above solutions require upgrading or modifying existing terminals or protocols, which will increase the software and hardware development costs of mobile terminals and is not conducive to the expansion of mobile phone direct satellite services. Therefore, it is necessary to explore how to compensate for frequency deviation on the base station side.

[0006] Patent document No. 202310658355.9 proposes a frequency offset compensation method based on the base station side, in which the satellite base station uses the coverage range of the ground beam to determine the ground reference point in real time, and then determines the relative speed of the satellite and the point and the elevation angle of the point to the satellite based on the ground reference point. Then, the Doppler frequency offset compensation value is calculated based on the obtained parameters, and finally the beam signal sent by the satellite base station is compensated for the Doppler frequency offset. Taking the satellite orbit altitude of 780km, carrier frequency of 2.1GHz, subcarrier spacing of 30KHz, beam maximum Doppler frequency shift of ±56KHz, and mobile phone anti-frequency offset capability upper limit of ±15KHz as an example, when the observation elevation angle of the center position of the satellite coverage beam is 60°, the corresponding Doppler frequency shift is +20KHz, and the satellite-borne base station pre-compensates the downlink signal by -20KHz. If the Doppler frequency shift of the downlink channel of UE1 is +7KHz, the residual frequency deviation of the downlink signal after compensation by the base station is -13KHz, which does not exceed 15KHz, then UE1 can complete downlink synchronization; if the Doppler frequency shift of the downlink channel of UE2 is +50KHz, the residual frequency deviation of the downlink signal after compensation by the base station is -30KHz, which exceeds the anti-frequency deviation capability of the mobile phone, so UE2 cannot complete downlink synchronization. It can be seen that this method only performs a single frequency deviation pre-compensation on the downlink signal sent to the beam at the center point of the beam. When the beam range is large, the residual frequency deviation of some terminals may exceed their correction capability and fail to complete frequency synchronization. Summary of the invention

[0007] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and propose a frequency synchronization solution for 5G FDD existing mobile phones directly connected to satellites. When the terminal is not changed and the beam range is only limited by the beam gain, the impact of user differential Doppler frequency shift is reduced so that all existing terminals within the beam range can complete frequency synchronization with the satellite.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] (1) In the downlink direction, the satellite base station periodically sends synchronization signals in the form of synchronization signal block (SSB) burst sets, and divides the Doppler frequency shift into integer frequency offset and fractional frequency offset. The integer frequency offset is compensated by the satellite base station, and the fractional frequency offset is compensated by the existing mobile phones themselves.

[0010] (2) The satellite-borne base station performs different integer frequency offset pre-compensation on each SSB in the SSB burst set and its corresponding system message block SIB1;

[0011] (3) After the signal reaches the terminal, the terminal can decode at least one of the SSBs, and then the terminal continues to compensate for the residual fractional frequency offset;

[0012] (4) All terminals in the beam correctly decode SSB and SIB1 to complete downlink synchronization and obtain preamble opportunities;

[0013] (5) The terminal initiates a random access request to try to establish a connection with the satellite, and performs frequency offset pre-compensation on the sent preamble sequence Msg1 according to the carrier frequency and the fractional frequency offset;

[0014] (6) The base station indicates through SIB1 that different SSB signals correspond to different preamble opportunities, and creates different preamble detection windows according to the preamble opportunities. The base station performs uplink frequency offset compensation according to the downlink integer frequency offset corresponding to each window, so that the preamble sequence received in each preamble detection window is as unbiased as possible;

[0015] (7) The base station performs preamble detection on the signal after frequency offset compensation, obtains the preamble sequence ID and TA for identifying the terminal, and stores the corresponding integer multiple frequency offset in the downlink direction on the base station side;

[0016] (8) The base station adjusts the frequency domain resource allocation of Msg2, Msg3 and Msg4 during each user's random access process based on the integer frequency offset it has saved and the satellite scheduling algorithm, and compensates for the integer frequency offset by means of resource grid offset;

[0017] (9) The base station adjusts the frequency domain resource allocation of the uplink and downlink signals for each user's subsequent service transmission, uses the same compensation method as in (8) to perform integer frequency offset compensation, and combines the frequency offset compensation capability of existing mobile phones to achieve frequency synchronization during the connection between 5G mobile phones and satellites;

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] First, in order to achieve downlink synchronization between existing mobile phones and satellites, the existing technology uses the center point of the beam range as a reference point to pre-compensate the downlink signal. However, when the beam range is large, it is impossible to ensure that all mobile phones complete synchronization, so it is necessary to strictly limit the beam range. The beam range of the present invention is only limited by the beam gain. By compensating different frequency deviation values ​​for different SSB signals in the burst set, all existing mobile phones in the satellite coverage beam can complete downlink synchronization.

[0020] Second, in order to solve the problem of excessive residual frequency deviation of uplink signals in satellite-to-ground communication, the existing technology needs to modify the mobile phone side and try to make the mobile phone compensate for the uplink frequency deviation by itself, which is not compatible with existing mobile phones. However, the present invention makes modifications to the base station side, and compensates for the frequency deviation of the uplink signal by the base station side, which can adapt to the technical standards of existing mobile phones. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart for realizing the present invention;

[0022] Figure 2 It is a schematic diagram of an application scenario of the present invention;

[0023] Figure 3 It is a schematic diagram of the existing downlink synchronization signal frequency deviation compensation;

[0024] Figure 4 A schematic diagram of performing frequency deviation compensation for a downlink synchronization signal in the present invention;

[0025] Figure 5 A schematic diagram of preamble sequence frequency offset compensation in the present invention;

[0026] Figure 6 A schematic diagram of uplink and downlink signal frequency deviation compensation in the random access and service transmission process of the present invention;

[0027] Figure 7 A schematic diagram of a method for frequency offset compensation using resource grid offset in the present invention; DETAILED DESCRIPTION

[0028] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0029] Reference Figure 2 , is the application scenario of the present invention, including base stations, satellites and terminals. The base station duplex mode adopts FDD mode, and the terminal directly connects to the satellite in regeneration forwarding mode, that is, the satellite can perform some or all functions of the base station, can encode and decode the transmission signal, and directly communicate with the mobile phone.

[0030] The first step in establishing a connection between a mobile phone and a base station is the downlink synchronization process. The present invention assumes that the existing mobile phones use the direct sliding cross-correlation algorithm with the worst frequency deviation resistance when decoding the downlink synchronization signal. When the frequency deviation is not greater than 1 / 2Δf, it is considered that the bit error rate is low and can be correctly decoded. Therefore, 1 / 2Δf is regarded as the upper limit of the frequency deviation resistance of the existing mobile phones. When the Doppler frequency shift of the low-orbit satellite and the mobile phone transmission signal exceeds 1 / 2Δf, the existing mobile phones cannot complete the downlink synchronization.

[0031] Utilizing the above scenario, the present invention addresses the problems of the prior art and proposes an uplink and downlink frequency synchronization method that is suitable for existing mobile phones, so that all users in the beam can complete downlink synchronization and random access and perform service transmission when the beam range is only limited by the beam gain.

[0032] Reference Figure 1 , the implementation steps of this example are as follows:

[0033] Step 1: When the base station sends a synchronization signal in the downlink direction, the Doppler frequency shift is divided into integer frequency offset and fractional frequency offset, and different integer frequency offset pre-compensations are performed on the SSB in the SSB burst set and the corresponding SIB1.

[0034] 1.1) The base station calculates the maximum Doppler frequency shift f according to the system subcarrier spacing Δf and the beam d Determine the number of SSBs n SSB :

[0035] n SSB =2m+1, where

[0036] 1.2) Calculate n SSB Frequency deviation value compensated for each SSB

[0037] where i=1,2,…,n SSB ;

[0038] 1.3) The base station pre-compensates the i-th SSB and the corresponding SIB1 The size of the frequency deviation.

[0039] This example is based on f d = ±56KHz, Δf = 30KHz, With the parameters in the prior art, the satellite-borne base station performs frequency offset compensation of -2Δf, -Δf, 0, Δf, and 2Δf on the five SSBs in the burst set before downlink transmission, and obtains the user frequency offset range during downlink transmission, as shown in Table 1.

[0040] Table 1 User frequency deviation range during downlink transmission

[0041]

[0042] Reference Figure 3 The existing technology uses the beam center point as the reference point for frequency offset compensation, which will cause the residual frequency offset of UE2 to be out of the terminal acceptance range, so it cannot be correctly decoded to complete downlink synchronization.

[0043] Reference Figure 4 After this step performs frequency offset compensation on the five SSB signals in the burst set, terminal groups 1-5 can at least find one SSB downlink residual frequency offset within the acceptable range, so the SSB and the corresponding SIB1 can be correctly decoded.

[0044] Step 2: After the downlink signal reaches the terminal, the terminal estimates and compensates for the residual fractional frequency offset of the downlink signal, correctly decodes the SSB to complete downlink synchronization, and then demodulates the system message block SIB1 to obtain the leading opportunity.

[0045] 2.1) The terminal estimates the frequency offset of the downlink signal:

[0046] Existing methods include PN-based autocorrelation method, OFDM pilot sequence-based autocorrelation method, PSS-based direct cross-correlation method, PSS-based segmented cross-correlation method, PSS-based and CP-based joint estimation method, etc. This example uses but is not limited to the PSS-based direct cross-correlation method for frequency offset estimation, and the specific implementation is as follows:

[0047] 2.1.1) Conjugate the signal y(n) received by the terminal with the local PSS sequence s * (n) are multiplied to obtain the sequence c(n):

[0048]

[0049] in s(n) is the time domain PSS signal, f ε is the residual fractional frequency deviation, N is the number of sampling points;

[0050] 2.1.2) Cross-correlate the two sequences before and after c(n) to obtain the sequence

[0051]

[0052] where c * (n) is the conjugated sequence of c(n);

[0053] 2.1.3) According to the sequence The residual fractional frequency deviation f is calculated ε :

[0054]

[0055] 2.2) The terminal performs phase rotation on the received signal y(n) through the baseband processor to compensate for the frequency offset, so that the residual fractional frequency offset f ε is 0;

[0056] 2.3) The terminal demodulates the primary synchronization signal PSS, the secondary synchronization signal SSS and the demodulation reference signal DMRS in the SSB to obtain the radio frame boundary and the physical cell ID to complete downlink synchronization;

[0057] 2.4) The terminal monitors the system information radio network temporary identifier SI-RNTI through the downlink physical control channel PDCCH to demodulate SIB1 on the physical downlink shared channel PDSCH, so that the terminal obtains the preamble opportunity.

[0058] Step 3: The terminal initiates a random access request to establish a connection with the satellite, and performs frequency offset pre-compensation on the sent preamble sequence Msg1.

[0059] 3.1) The terminal initiates a random access request according to the instruction of the radio resource control RRC signaling to try to establish a connection with the satellite;

[0060] 3.2) After the terminal initiates random access, it performs frequency offset pre-compensation on the transmitted preamble sequence Msg1. The calculation formula is:

[0061]

[0062] Among them, f UEU is the terminal pre-compensation amount, f ε represents the downlink frequency offset estimation value, f DC Indicates the downlink carrier frequency, f UC Indicates the uplink carrier frequency.

[0063] Step 4: The base station creates different preamble detection windows according to the preamble opportunities in the SIB1 information, and compensates different frequency offset values ​​for the received preamble signals in different windows.

[0064] Reference Figure 5 , the specific implementation of this step is as follows:

[0065] 4.1) The base station creates different preamble detection windows according to the preamble opportunities in the SIB1 information:

[0066] 4.1.1) After the base station provides the configuration of the random access channel PRACH to the terminal through the broadcast channel, the terminal obtains the starting position of the preamble time slot according to the SIB1 corresponding to the i-th SSB to determine the preamble opportunity τ i ;

[0067] 4.1.2) The base station determines the minimum round-trip delay between the user and the satellite-borne base station within the frequency deviation range through the satellite's ephemeris information. and maximum round trip delay

[0068] 4.1.3) Base station according to and leading opportunity τ i Determine the leading detection window #i, whose starting point is The window length is

[0069] 4.2) The base station calculates the residual frequency offset of the leading sequence in each window and compensates for different frequency offset values:

[0070] 4.2.1) The base station receives the preamble sequence sent by the corresponding user in each preamble detection window and calculates the residual frequency offset f in the preamble sequence Uleft :

[0071]

[0072] Among them, f UEU Indicates the frequency offset compensation of the mobile phone's leading sequence, f U Denote the Doppler frequency shift experienced by the UE’s uplink channel, f Dcom Indicates the frequency offset compensation value of the base station for SSB, f DC Indicates the downlink carrier frequency, f UC Indicates the uplink carrier frequency;

[0073] 4.2.2) The base station receives the residual frequency deviation of the signal in window #i Integer frequency deviation n i Δf and fractional frequency deviation ε i Δf(-0.5<ε<0.5);

[0074] 4.2.3) The base station uses the frequency offset compensation method of resource grid offset to compensate the integer frequency offset n i Δf is used for compensation, that is, when the base station performs resource demapping, the frequency domain extraction position of the leading sequence is -n i The offset of a resource grid;

[0075] 4.2.4) The base station then performs phase rotation on the pilot sequence to compensate for the remaining fractional frequency offset ε i Δf.

[0076] refer to Figure 5 , the base station performs -54KHz frequency offset compensation on the preamble sequence sent by the terminal in the preamble detection window #1 according to the SIB1 information corresponding to the first SSB in the SSB burst set; and performs -27KHz frequency offset compensation on the preamble sequence sent by the terminal in the preamble detection window #2 according to the SIB1 information corresponding to the second SSB. Similarly, the uplink and downlink frequency offset compensation size relationship after each terminal group completes the above process is shown in Table 2.

[0077] Table 2 Uplink and downlink frequency offset compensation relationship table

[0078]

[0079] Step 5: The base station performs preamble detection on the signal after frequency offset compensation, obtains the preamble sequence ID and TA for identifying the terminal, and stores the corresponding downlink integer multiple pre-compensation size on the base station side. and the uplink residual frequency deviation of window #i The integer multiple frequency deviation n i Δf;

[0080] Step 6: The base station performs integer frequency offset compensation for the randomly accessed Msg2, Msg3, Msg4 and the uplink and downlink signals of the service transmission in a resource grid offset manner based on the integer frequency offset it saves and the satellite scheduling algorithm, and combines the frequency offset compensation capability of the mobile phone itself to make the uplink and downlink signals as unbiased as possible.

[0081] Reference Figure 6 and Figure 7 , the specific implementation of this step is as follows:

[0082] 6.1) After completing the first step of random access, Msg1, the base station uses RA-RNTI to send DCI scheduling information to the terminal on the physical downlink control channel PDCCH, and shifts the frequency domain resource position of Msg2 to be sent by im-1 resource grids, that is, Frequency deviation pre-compensation of different sizes;

[0083] 6.2) When the base station generates the uplink grant UL Grant in the Msg2 information in the second step of random access, it offsets the frequency domain resource position of Msg3 by -n i resource grid, that is, -n i Integer multiple frequency offset compensation of Δf;

[0084] 6.3) After receiving the UL Grant in Msg2, the terminal sends Msg3 on the physical uplink shared channel PUSCH through the designated uplink resources to complete the third step of random access, and uses the temporary C-RNTI for identification.

[0085] 6.4) After receiving Msg3 confirming the access request of the terminal, the base station sends DCI on PDCCH to notify the terminal of the resource allocation of the physical downlink shared channel PDSCH, and shifts the frequency domain resource position of Msg4 to be sent by im-1 resource grids, that is, Frequency deviation pre-compensation of different sizes;

[0086] 6.5) After receiving Msg4, the terminal completes random access to the satellite base station, enters the RRC connection state, and allocates a permanent C-RNTI for subsequent service transmission identification;

[0087] 6.6) Before downlink data transmission, the base station sends DCI through PDCCH to notify the terminal of PDSCH resource allocation, and shifts the frequency domain resource position of the downlink signal by im-1 resource grids, that is, Frequency deviation pre-compensation of different sizes;

[0088] 6.7) When the terminal sends uplink data, the base station sends UL Grant to the terminal through PDCCH to indicate the uplink PDSCH resource allocation, and offsets the frequency domain resource position of the uplink signal by -n i resource grid, that is, -ni Integer multiple frequency offset compensation of Δf;

[0089] The present invention can enable a mobile phone to achieve frequency synchronization with a satellite signal transmission process without modifying an existing mobile phone, thereby ensuring that the signal can be correctly decoded during transmission and completing a normal communication process between the mobile phone and the satellite.

[0090] The above description is only a specific example of the present invention and does not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principles of the present invention, it is possible to make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

[0091] It should be noted that the step numbers in the specification and claims of the present invention are only for a clear description of the implementation scheme of the present invention to facilitate understanding, and the sequence of the step numbers is not limited.

Claims

1. A frequency synchronization method for 5G FDD existing mobile phones directly connected to satellites, characterized in that: The steps include: (1) In the downlink direction, the satellite base station periodically sends synchronization signals in the form of synchronization signal block (SSB) burst sets, and divides the Doppler frequency shift into integer frequency offset and fractional frequency offset. The integer frequency offset is compensated by the satellite base station, and the fractional frequency offset is compensated by the existing mobile phones themselves. (2) The satellite-borne base station performs different integer frequency offset pre-compensation on each SSB in the SSB burst set and its corresponding system message block SIB1; (3) After the signal reaches the terminal, the terminal can decode at least one of the SSBs, and then the terminal continues to compensate for the residual fractional frequency offset; (4) All terminals in the beam correctly decode SSB and SIB1 to complete downlink synchronization and obtain preamble opportunities; (5) The terminal initiates a random access request to try to establish a connection with the satellite, and performs frequency offset pre-compensation on the sent preamble sequence Msg1 according to the carrier frequency and the fractional frequency offset; (6) The base station indicates through SIB1 that different SSB signals correspond to different preamble opportunities, and creates different preamble detection windows according to the preamble opportunities. The base station performs uplink frequency offset compensation according to the downlink integer frequency offset corresponding to each window, so that the preamble sequence received in each preamble detection window is as unbiased as possible; (7) The base station performs preamble detection on the signal after frequency offset compensation, obtains the preamble sequence ID and TA for identifying the terminal, and stores the corresponding integer multiple frequency offset in the downlink direction on the base station side; (8) The base station adjusts the frequency domain resource allocation of Msg2, Msg3 and Msg4 during each user's random access process based on the integer frequency offset it has saved and the satellite scheduling algorithm, and compensates for the integer frequency offset by means of resource grid offset; (9) The base station adjusts the frequency domain resource allocation of the uplink and downlink signals for each user's subsequent service transmission, uses the same compensation method as in (8) to perform integer frequency offset compensation, and combines the frequency offset compensation capability of existing mobile phones to achieve frequency synchronization during the connection between 5G mobile phones and satellites.

2. The method according to claim 1, characterized in that: In step (2), the base station performs different integer frequency offset pre-compensation on each SSB in the SSB burst set and its corresponding system message block SIB1, and the implementation steps include the following: (2a) Based on the system subcarrier spacing Δf and the beam maximum Doppler frequency shift f d Calculate the number of SSBs n in each SSB burst set SSB : n SSB =2m+1 in (2b) Compensate different frequency offset values ​​f for different SSBs in each SSB burst set Dcom , the calculation formula for the pre-compensation frequency deviation value of the i-th SSB is as follows: in is the frequency deviation value of the i-th SSB compensation, i=1,2,…,n SSB .

3. The method according to claim 1, characterized in that In step (4), all terminals in the beam correctly decode SSB and SIB1 respectively, and obtain the wireless frame boundary and physical cell ID by detecting the primary synchronization signal PSS, the secondary synchronization signal SSS and the demodulation reference signal DMRS to complete downlink synchronization; then the terminal receives the information carried by SIB1 on the downlink shared physical channel PDSCH, so that the terminal obtains the preamble opportunity.

4. The method according to claim 1, characterized in that In step (5), the terminal performs pre-compensation based on the carrier frequency and the fractional frequency offset, and the formula is as follows: Among them, f UEU is the compensation amount, f ε represents the downlink frequency offset estimation value, f DC Indicates the downlink carrier frequency, f UC Indicates the uplink carrier frequency.

5. The method according to claim 1, characterized in that Step (6) The base station creates different preamble detection windows according to the preamble opportunities, and performs uplink frequency offset compensation according to the downlink integer frequency offset corresponding to each window. The implementation steps include the following: (5a) After the base station provides the configuration of the random access channel PRACH to the terminal through the broadcast channel, the terminal obtains the starting position of the preamble time slot according to the SIB1 corresponding to the i-th SSB to determine the preamble timing τ i ; (5b) The base station determines the minimum round-trip delay between the user and the satellite-borne base station within the frequency deviation range through the satellite's ephemeris information. and maximum round trip delay (5c) Base station according to and leading opportunity τ i Determine the leading detection window #i, whose starting point is The window length is (5d) The base station receives the preamble sequence sent by the corresponding user in each preamble detection window and calculates the uplink residual frequency offset in the preamble sequence in, represents the frequency offset compensation value of the base station at the i-th SSB, f DC Indicates the downlink carrier frequency, f UC Indicates the uplink carrier frequency; (5e) The base station receives the residual frequency deviation of the signal in window #i Integer frequency deviation n i Δf and fractional frequency deviation ε i Δf, and then compensate separately, where the integer multiple frequency deviation n i Δf is compensated by means of resource grid offset.

6. The method according to claim 1, characterized in that In step (8), the base station adjusts the frequency domain resource allocation of Msg2, Msg3 and Msg4 in the random access process of each user based on the integer frequency offset stored and the satellite scheduling algorithm, and performs integer frequency offset compensation in the form of resource grid offset. The implementation steps include the following: (6a) The base station adjusts the Msg2 resource allocation strategy in the second step of random access, that is, when sending DCI to the terminal through PDCCH, the specified Msg2 frequency domain resource position is offset by im-1 resource grids, that is, Frequency deviation pre-compensation of different sizes; (6b) When the base station allocates an uplink grant UL Grant to the terminal through Msg2 in the second step of random access, it adjusts the resource allocation strategy of Msg3 and offsets the frequency domain resource position of the specified Msg3 by -n i resource grid, that is, -n i Integer multiples of Δf are used for post-frequency offset compensation; (6c) The base station adjusts the Msg4 resource allocation strategy in the fourth step of random access. When sending DCI on the PDCCH to notify the terminal of the downlink PDSCH resource allocation, the frequency domain resource position of the Msg4 to be sent is offset by im-1 resource grids, that is, Frequency deviation precompensation of different sizes.

7. The method according to claim 1, characterized in that In step (9), the base station adjusts the frequency domain resource allocation of the uplink and downlink signals for subsequent service transmission of each user, and uses the same compensation method as in (8) to perform integer frequency offset compensation. The implementation steps include the following: (7a) After the terminal and the base station complete random access, a permanent C-RNTI is allocated for subsequent service transmission identification; (7b) Before downlink data transmission, when the base station sends DCI through PDCCH to notify the terminal of downlink PDSCH resource allocation, the downlink signal frequency domain resource position is offset by im-1 resource grids, that is, Frequency deviation pre-compensation of different sizes; (7c) Before uplink data transmission, the base station sends a UL Grant to the terminal via PDCCH to indicate the uplink PDSCH resource allocation, and offsets the frequency domain resource position of the uplink signal by -n i resource grid, that is, -n i The frequency offset is compensated after the integer multiple of Δf.

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