CN110719625B - SSB sending method and device, base station and system - Google Patents
SSB sending method and device, base station and system Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/06—TPC algorithms
- H04W52/14—Separate analysis of uplink or downlink
- H04W52/146—Uplink power control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
- H04W52/241—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
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Abstract
The application provides a method, a device, a base station and a system for sending SSB, comprising the following steps: and in one transmission period of the SSB, only one SSB is transmitted, wherein the transmission power of one SSB is the target transmission power or the preset basic transmission power, and the target transmission power is larger than or equal to the basic transmission power. Therefore, the terminal can assume that the number of SSB of the cell is 1 for detection, SSB combining operation is not needed, the complexity of terminal detection is reduced, the accuracy of detection is improved, and because SSB subcarriers are separated from other subcarriers for DFT-s-OFDM modulation, the peak-to-average ratio of signals is not increased under the condition that only one SSB is transmitted, and the demodulation performance of the terminal is ensured.
Description
Technical Field
The present invention relates to the field of wireless communications, and in particular, to a method and apparatus for sending SSB, a base station, and a system.
Background
In the process of communication between the base station and the terminal, the base station needs to send a downlink synchronization channel to the terminal, and the main function of the downlink synchronization channel is to enable the terminal to acquire frequency and symbol synchronization with the downlink synchronization channel of the cell, acquire the starting position of a downlink same-channel signal frame, and determine the PCI (Physical Cell Identity, physical layer cell identifier) of the cell by detecting the downlink synchronization channel.
The downlink synchronization channel includes: PSS (Primary synchronization signal ) and SSS (Secondary synchronization signal, secondary synchronization signal). Wherein the PSS, SSS and PBCH (Physicalbroadcast channel ) constitute one SSB (SS/PBCH block).
Because the movement speed of the low-orbit satellite is very fast, the terminal can switch a cell within 10s, and the signal-to-noise ratio of the low-orbit satellite channel is very low and is as low as-10 dB, the rationality of the design of the downlink synchronous channel is very important, and the terminal can quickly and correctly perform downlink synchronization under the satellite channel condition while taking the cost into consideration.
In the prior art, in order to ensure the accuracy of SSB detection, a repeated SSB sending method is adopted, so that the terminal needs to perform incoherent combination operation on repeated SSBs and multiple SSB peaks appear, the terminal needs to judge the first SSB position according to the SSB peaks, and the problem of error in judging the first SSB position is likely to appear under the condition of rapid change of channel receiving power caused by low signal-to-noise ratio and rapid movement of satellites.
It can be seen that the existing SSB transmission method increases the complexity of terminal detection and the possibility of error.
Disclosure of Invention
The application provides a method and a device for SSB, a base station and a computer readable storage medium, aiming at solving the problems of reducing the complexity and the error possibility of detecting the SSB by a terminal under the condition of not increasing the overhead.
In order to achieve the above object, the present application provides the following technical solutions:
a method of transmitting a synchronous broadcast block SSB, comprising:
and transmitting one SSB within one transmission period of the SSB, wherein the transmission power of the one SSB is a target transmission power or a preset basic transmission power, the target transmission power is larger than or equal to the basic transmission power, and the SSB subcarriers are separated from other subcarriers for DFT-s-OFDM modulation.
Optionally, before said sending an SSB, the method further comprises:
estimating the downlink average receiving signal-to-noise ratio of the cell;
and under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower than a first threshold value, the transmitting power of the SSB is increased by a preset first value on the basis of the basic transmitting power, and the target transmitting power of the SSB is obtained.
Optionally, the method further comprises:
and reducing the transmitting power of other frequency domain subcarriers so that the transmitting power of the frequency domain subcarriers of a transmitting target time slot is not more than a preset threshold, wherein the target time slot is the time slot where the SSB is positioned, and the other frequency domain subcarriers are frequency domain subcarriers outside the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the transmitting target time slot.
Optionally, the method further comprises:
reducing the code rate of the other frequency domain subcarriers, and/or changing the modulation mode of the other frequency domain subcarriers from a first mode to a second mode;
wherein the demodulation error probability of the first mode is greater than the demodulation error probability of the second mode.
Optionally, the method further comprises:
and the other frequency domain subcarriers are emptied, so that the transmitting power of the frequency domain subcarriers of a transmitting target time slot is not more than a preset threshold value, the target time slot is the time slot where the SSB is positioned, the other frequency domain subcarriers are the first number of frequency domain subcarriers except the frequency domain subcarriers occupied by the SSB in the frequency domain carriers of the transmitting target time slot, and the first number is determined according to the first number.
Optionally, the method further comprises:
and adding indication information in the master information block MIB or the system information block SIB, wherein the indication information is used for indicating the positions of the other frequency domain subcarriers which are nulled.
Optionally, the one SSB occupies the last four OFDM symbols of one slot.
A SSB transmitting apparatus comprising:
and the transmitting unit is used for transmitting one SSB within one transmitting period of the SSB, wherein the transmitting power of the one SSB is a target transmitting power or a preset basic transmitting power, the target transmitting power is larger than or equal to the basic transmitting power, and the SSB subcarrier is separated from other subcarriers for DFT-s-OFDM modulation.
A communication system, comprising:
base stations, satellites, and terminals;
the base station is configured to send one SSB to the satellite within one transmission period of the SSB, where the transmission power of the one SSB is a target transmission power or a preset base transmission power, the target transmission power is greater than or equal to the base transmission power, and the SSB subcarrier is separately DFT-s-OFDM modulated from other subcarriers;
the satellite is used for broadcasting the SSB to the terminal;
the terminal detects and performs primary synchronization signal PSS synchronization, secondary synchronization signal SSS synchronization, and physical broadcast channel PBCH demodulation according to only one SSB per transmission period of the SSBs.
Optionally, the base station is further configured to:
estimating a downlink average received signal-to-noise ratio of a cell before transmitting an SSB to the satellite; and under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower than a first threshold value, the transmitting power of the SSB is increased by a preset first value on the basis of the basic transmitting power, and the target transmitting power of the SSB is obtained.
A base station, comprising: a processor and a memory for storing a program; the processor is configured to run the program to implement the above-mentioned SSB transmission method.
According to the technical scheme, only one SSB is transmitted in one transmission period of the SSB, the transmission power of the one SSB is the target transmission power or the preset basic transmission power, and the target transmission power is greater than or equal to the basic transmission power. Therefore, the terminal can assume that the number of SSB of the cell is 1 for detection, SSB combining operation is not needed, the complexity of terminal detection is reduced, the detection accuracy is improved, and the SSB sub-carrier and other sub-carriers are separated for DFT-s-OFDM modulation, so that the peak-to-average ratio of signals is not increased under the condition that only one SSB is transmitted, and the demodulation performance of the terminal is ensured.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a prior art SSB transmission mode;
FIG. 2 is a graph of a peak detection result at a high signal-to-noise ratio for a prior art SSB of 4;
FIG. 3 is a graph of a peak detection result at a low signal-to-noise ratio for a prior art SSB of 4;
FIG. 4 is a schematic diagram of SSB transmission modes disclosed in an embodiment of the present application;
FIG. 5 (a) is a graph of the peak detection results of SSB detection disclosed in the examples of the present application;
FIG. 5 (b) is another peak detection result graph of SSB detection disclosed in the examples of the present application;
fig. 6 is a flowchart of a method for sending SSB disclosed in an embodiment of the present application;
fig. 7 is a flowchart of another SSB sending method disclosed in an embodiment of the present application;
fig. 8 is a flowchart of another SSB sending method disclosed in an embodiment of the present application;
fig. 9 is a schematic structural diagram of a transmitting device of SSB disclosed in an embodiment of the present application;
fig. 10 is a schematic structural diagram of a base station according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
The SSB sending method provided by the embodiment of the application can be applied to scenes such as satellite communication, broadband, 5G communication and the like.
To facilitate an understanding of the methods provided by the embodiments of the present application, SSB techniques involved in the present application are briefly described first. In SSB, PSS and SSS occupy one OFDM symbol each, and two PBCHs occupy one OFDM (Orthogonal Frequency Division Multiplex, orthogonal frequency division multiplexing) symbol each, that is, one SSB occupies four OFDM symbols in the time domain, and the four OFDM symbols are consecutive symbols. Meanwhile, in the frequency domain, one SSB occupies 20 frequency resource blocks PRB. In a slot where SSB is transmitted, the slot includes 14 consecutive OFDM symbols, and transmitting an SSB needs to occupy 4 consecutive OFDM symbols in the slot and 20 PRBs, and other OFDM symbols occupy other frequency domain subcarriers.
Fig. 1 is an exemplary diagram of an SSB transmission mode in the prior art, in fig. 1, two slots (slots) are set within one transmission period n, and two SSBs are repeatedly transmitted in each slot, that is, SSBs (SSB 1, SSB2, SSB3, and SSB4 in the figure) are repeatedly transmitted for one cell in one period. In the figure, the number "0" in the slot is an OFDM symbol occupied by a reference signal CRS (Cell-specific reference signal ), and the number "7" in the slot is an OFDM symbol occupied by an auxiliary reference signal CRS.
The inventor researches and discovers that, when the terminal is initially accessed, the terminal needs to perform incoherent combination operation on repeated SSB, and multiple SSB peaks appear, the terminal needs to judge the first SSB position according to the SSB peaks, and under the condition of low signal-to-noise ratio and rapid change of channel receiving SINR (Signal to Interference plus Noise Ratio, signal-to-interference-plus-noise ratio) caused by rapid movement of a satellite, error in judging the first SSB position can possibly occur.
Fig. 2 is an exemplary diagram of peak detection results of PSS incoherent combining and detection performed by a terminal in a case where a normal signal-to-noise ratio (for example, snr=8 dB) and a base station repeatedly transmits 4 SSBs in one period. Fig. 3 is an exemplary diagram of the equivalent detection result of PSS incoherent combining and detecting performed by the terminal when the signal-to-noise ratio is low and there is a large frequency offset (e.g., snr= -10 dB), and the base station repeatedly transmits 4 SSBs in one period. In fig. 2 and 3, the horizontal axis represents time and the vertical axis represents power.
The application provides a sending method of SSB, which comprises the following steps: within a transmission period of the SSB, one SSB is transmitted, that is: for one cell, only one SSB is transmitted within one transmission period of the SSB. And, the SSB sub-carriers are DFT-s-OFDM modulated separately from other sub-carriers. After the modulation is completed, each modulated subcarrier is mapped to a corresponding subcarrier position.
The transmitting power of one SSB is target transmitting power or preset basic transmitting power, and the target transmitting power is larger than or equal to the basic transmitting power.
Fig. 4 is a schematic diagram of SSB transmission mode in this embodiment, as shown in fig. 4, one SSB is sent in one period, that is, one slot is set in one period, and the SSB occupies only four consecutive OFDM symbols in one slot. Optionally, in this embodiment, the SSB transmitted each time occupies the last four symbols of a slot, so as to facilitate resource allocation of other downlink channels.
In this embodiment, since the base station transmits one SSB in one period, the terminal configures only the number of SSBs to be 1 in one period, and only one detection is required.
The transmission power of the SSB may be a target transmission power or a preset base transmission power, where the transmission power of the SSB may be the base transmission power when the downlink average received signal-to-noise ratio of the cell is high. The base transmit power may be set according to requirements, and optionally, the base transmit power may be a transmit power value used in transmitting SSBs in the prior art.
Wherein the target transmitting power is set to be larger than the base power, and specifically, the target transmitting power is related to the downlink average receiving signal-to-noise ratio of the cell. The lower the downlink average received signal-to-noise ratio of the cell, the greater the difference between the target transmit power and the base power.
The target transmit power is set to be greater than the base power in order to reduce the influence of noise on SSB detection. The applicant researches the peak detection result diagrams of fig. 2 and 3 obtained by using the SSB transmission mode in the prior art, and discovers that in the case that the number of SSBs repeatedly transmitted by a base station is the same but the signal to noise ratio is different, in the peak detection result of fig. 3, the distribution of peaks is more irregular than that of fig. 2, and thus noise obviously affects the peaks, for example, after the noise is superimposed on the peak position, the peak is raised or lowered, so that the detection difficulty is increased. Therefore, in the present embodiment, when the signal-to-noise ratio is low, the terminal can maintain the accuracy of detection by increasing the transmission power of the SSB.
Fig. 5 (a) and fig. 5 (b) are graphs of peak detection results obtained by the method provided by the embodiment, specifically, fig. 5 (a) is a graph of peak detection results corresponding to an increase of 9dB in SSB transmission power at a signal-to-noise ratio of-10 dB, and fig. 5 (b) is a graph of peak detection results corresponding to an increase of 6dB in SSB transmission power at a signal-to-noise ratio of-10 dB, which shows that the detected peak is prominent and single in the transmission period of SSB when the signal-to-noise ratio is low and the SSB transmission power is properly increased.
In this embodiment, peak detection result graphs are obtained, and compared with peak detection results in fig. 2 and fig. 3, fig. 5 (a) and fig. 5 (b), multiple peaks appear in fig. 2 and fig. 3, so that a terminal needs to determine a first SSB position according to the peaks of the SSBs, and the detection difficulty and the error probability are increased.
Based on the above technical features of the present embodiment, DFT-s-OFDM modulation is performed separately for SSB subcarriers from other subcarriers so as not to increase the peak-to-average ratio of the signal. Also taking fig. 4 as an example, DFT-s-OFDM modulation is performed separately for the last four consecutive OFDM symbols occupied by SSB.
In the method provided by the embodiment of the application, one SSB is sent in one sending period of the SSB, the sending power of only one SSB in one cell is the target sending power or the preset basic sending power, and the target sending power is larger than or equal to the basic sending power. In the technical scheme, in one SSB period, one cell only sends one SSB, so that the terminal can assume that the number of SSBs of the cell is 1 for detection, SSB merging operation is not needed, the complexity of terminal detection is reduced, and the accuracy of detection is improved. And, the DFT-s-OFDM modulation is performed on the SSB sub-carriers separately to reduce the peak-to-average ratio of the transmitted signal.
Fig. 6 is a schematic diagram of another SSB sending method according to an embodiment of the present application, which may include the following steps:
s601, estimating the downlink average receiving signal-to-noise ratio of the cell.
For example, for satellite communications, the downlink average received signal-to-noise ratio of a cell may be calculated based on ephemeris information, and when there are multiple cells under a satellite, the downlink average received signal-to-noise ratio of the cell is calculated for each cell. Ephemeris information, also called ephemeris data (ephemeris data), is a table of satellite orbit parameters, i.e. list data describing the position information and velocity information of the satellite at regular intervals. For the scenarios of broadband and 5G communication, the respective prior art calculations may be employed, which will not be described in detail here.
S602, under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower than a first threshold value, the transmitting power of the SSB is increased by a preset first value on the basis of the basic transmitting power, and the transmitting power of the SSB, namely the target transmitting power, is obtained.
The first threshold is a preset value, and the first preset size can be obtained according to actual measurement. Under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower than a first threshold value, the noise is larger, the detection of the SSB is greatly influenced, and under the condition, the transmitting power of the SSB is improved by a preset first value on the basis of the basic transmitting power. Wherein, the preset first value is equal to: the downlink average received signal-to-noise ratio of the cell is related to the difference of the first threshold, and the lower the downlink average received signal-to-noise ratio of the cell is, the larger the first value is.
It should be noted that, in the case where the downlink average received signal to noise ratio of the cell is not lower than the first threshold, the transmission power of the SSB may be the base transmission power.
S603, transmitting an SSB within a transmission period of the SSB according to the transmission power of the SSB.
After determining the transmission power of the SSB, one SSB is transmitted according to the transmission period of one SSB.
According to the method provided by the embodiment, the transmitting power of the SSB can be dynamically adjusted according to the downlink average receiving signal-to-noise ratio of the cell, so that the SSB is transmitted by adopting higher transmitting power under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower, and therefore, although only one SSB is transmitted, the accuracy of terminal detection is not reduced.
Fig. 7 is a schematic diagram of another SSB sending method according to an embodiment of the present application, which may include the following steps:
s701, estimating the downlink average receiving signal-to-noise ratio of the cell.
S702, under the condition that the downlink average receiving signal-to-noise ratio of a cell is lower than a first threshold value, the transmitting power of one SSB is increased by a preset first value on the basis of the basic transmitting power, and the transmitting power of one SSB, namely the target transmitting power, is obtained.
Specific implementations of S701 to S702 may refer to S601 to S602 of fig. 6.
S703, reducing the transmitting power of other frequency domain subcarriers so that the transmitting power of the frequency domain subcarriers of the transmitting target time slot is not greater than a preset threshold.
The target time slot is a time slot where the SSB is located, and other frequency domain subcarriers are frequency domain subcarriers except the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the transmitting target time slot.
In this embodiment, for example, one slot includes 14 OFDM symbols, and occupies 264 PRBs in total. Wherein, one SSB occupies 4 OFDM symbols and occupies 20 PRBs, the remaining 10 OFDM symbols are occupied by other frequency domain subcarriers, and the other frequency domain subcarriers occupy 244 PRBs.
In this embodiment, optionally, the preset threshold may be a total transmission power of the downlink synchronization signal in the prior art. In order to ensure that the total transmission power is unchanged, under the condition of increasing the transmission power of the SSB, the transmission power of other frequency domain subcarriers is required to be reduced, so that the total cost is not increased compared with the transmission power used in the method in the embodiment.
For example, under the condition of extremely low signal-to-noise ratio (snr= -10 dB), the transmission power of SSB is increased by 9dB, corresponding to that after SSB is increased by 8 times before increase, according to formula (1), the ratio Y of the transmission power after the decrease of other frequency domain subcarriers to the transmission power before decrease is calculated, and the ratio Y is converted into dB value, so that the transmission power of other frequency domain subcarriers is reduced by 3.7dB, and the MCS (Modulation and Coding Scheme, modulation and coding strategy) of PDSCH (Physical Downlink Shared Channel ) is reduced by 1-4 steps.
The formula (1) is: y= (RbNum-X SsbRbNum)/(RbNum-SsbRbNum).
Wherein Y is the ratio of the transmission power after the other frequency domain subcarriers are declined to the transmission power before the other frequency domain subcarriers are declined; x is the ratio of the transmission power after SSB lifting to the transmission power before SSB lifting; rbNum is the total PRB number, in this embodiment rbnum=264; ssbRbNum is the number of PRBs occupied by SSB, and SsbRbNum=20 in this embodiment.
S704, the code rate of other frequency domain subcarriers is reduced, or the modulation mode of the other frequency domain subcarriers is changed from the first mode to the second mode.
After the transmitting power of other frequency domain subcarriers is reduced, in order to ensure the accuracy of terminal detection, the code rate of other frequency domain subcarriers can be further reduced, or the modulation mode of other frequency domain subcarriers can be adjusted, so that the modulation mode is changed from a first mode to a second mode, wherein the demodulation error probability of the first mode is greater than the demodulation error probability of the second mode, and the method is beneficial to increasing the demodulation accuracy of the terminal. Of course, the modulation scheme of the other frequency domain subcarriers may be changed from the first scheme to the second scheme while the code rate of the other frequency domain subcarriers is reduced.
S705, according to the transmission power of the SSB, transmitting one SSB within one transmission period of the SSB.
The implementation process of S705 may refer to the above embodiment, and will not be described herein.
According to the method provided by the embodiment, under the condition of low signal-to-noise ratio, the accuracy of detecting the SSB by the terminal is ensured by improving the transmitting power of the SSB, meanwhile, the transmitting power of other frequency domain subcarriers is reduced, and the transmitting total power of the downlink synchronous signals is kept unchanged, so that compared with the prior art, the transmitting power used by the method is ensured not to be increased in total cost, further, the code rate of other frequency domain subcarriers is reduced, and/or the modulating mode of the other frequency domain subcarriers is adjusted, so that the accuracy of detecting signals on the other frequency domain subcarriers by the terminal is not influenced under the condition of reducing the transmitting power of the other frequency domain subcarriers.
In the existing SSB transmission method, 4 SSBs are transmitted within one transmission period, the number of SSBs transmitted is not dynamically adjusted according to the channel condition of the current cell, and fewer SSBs can not be transmitted for cells with high downlink average receiving signal-to-noise ratio so as to reduce the cost. Compared with the prior art, the method of the embodiment does not increase the total cost of the downlink even though the transmitting power of the SSB is improved, thereby realizing effective control of the cost under the condition of reducing the complexity of detecting the SSB by the terminal and improving the correctness.
Fig. 8 is a schematic diagram of another SSB sending method according to an embodiment of the present application, which may include the following steps:
s801, estimating the downlink average receiving signal-to-noise ratio of the cell.
S802, under the condition that the downlink average receiving signal-to-noise ratio of a cell is lower than a first threshold value, the transmitting power of one SSB is increased by a preset first value on the basis of the basic transmitting power, and the transmitting power of one SSB is obtained.
Specific implementations of S801 to S802 may refer to S601 to S602 of fig. 6.
S803, other frequency domain subcarriers are set to be empty, so that the transmitting power of the frequency domain subcarriers of the transmitting target time slot is not larger than a preset threshold value.
The target time slot is a time slot where the SSB is located, and other frequency domain subcarriers are a first number of frequency domain subcarriers except the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the same OFDM symbol as the SSB in the transmission target time slot, wherein the first number is determined according to a first numerical value. That is, the number of frequency domain subcarriers to be nulled is determined according to the boost value of the transmission power of the SSB, and specifically, the number of frequency domain subcarriers to be nulled can be calculated with reference to the formula (2).
Y＝(X-1)*SSbRbNum*12 (2)
Wherein Y is the number of nulled frequency domain subcarriers; x is the ratio of the transmission power after SSB lifting to the transmission power before SSB lifting; the SSbRbNum is the number of occupied PRBs of the SSB, and optionally, in this embodiment, the number of occupied PRBs of the SSB is 20.
In this embodiment, under the condition that the signal-to-noise ratio is low and the transmission power of the SSB is increased, in order to keep the total transmission power unchanged, other frequency domain subcarriers may be nulled, where the frequency domain subcarriers are nulled such that the frequency domain subcarriers do not transmit channels at the positions of the time slots.
In case of other frequency domain sub-carriers nulling, in order for the terminal to correctly demodulate the SSB, indication information for indicating the location of the nulled frequency domain sub-carriers is added to MIB (Master Information Block ) or SIB (System Information Block, system information block). For example, an indication of the frequency domain subcarrier blanking pattern of the time slot in which the 2bit SSB is located is increased. For example, when the 2bit indication is 0, it indicates that no frequency domain sub-carrier is empty; when the SSB transmitting power is increased by 3dB, corresponding to X=2, the 2bit is indicated as 1, and the number of the nulled subcarriers is 240; when the SSB transmitting power is improved by 6dB and corresponding to X=4, the 2bit is indicated as 2, and the number of the nulled subcarriers is 720; when the SSB transmit power is increased by 9dB, corresponding to x=8, the 2bit indication is 3, indicating that the number of nulled subcarriers is 1680.
S804, according to the transmitting power of the SSB, transmitting one SSB within one transmitting period of the SSB.
After determining the transmitting power of the SSB, transmitting one SSB according to a transmitting period of the SSB, so that the terminal only configures the number of the SSB to be 1, and performs one-time detection, thereby greatly reducing the complexity of terminal detection.
According to the method provided by the embodiment, under the condition of low signal-to-noise ratio, the accuracy of detecting the SSB by the terminal is ensured by improving the transmitting power of the SSB, meanwhile, other frequency domain subcarriers are emptied and the transmitting total power of the downlink signal is kept unchanged, so that the transmitting power used by the method is ensured not to be increased in total cost compared with the prior art, further, under the condition of emptying other frequency domain subcarriers, indication information is added in the MIB or the SIB to indicate the position of the emptied frequency domain subcarriers, and the terminal is ensured to be still capable of demodulating the SSB correctly.
Optionally, the transmission function may be reduced for a part of other subcarriers, so as to ensure that the total transmission power of the frequency domain subcarriers of the transmission target time slot is not greater than a preset threshold.
Corresponding to the above-mentioned method for sending SSB provided in the embodiment of the present application, referring to fig. 9, a schematic structural diagram of a sending device 90 for SSB is further provided in the embodiment of the present invention, where the sending device includes:
a transmitting unit 901, configured to transmit an SSB within a transmission period of the SSB, where a transmission power of the SSB is a target transmission power or a preset base transmission power, and the target transmission power is greater than or equal to the base transmission power, and the SSB subcarrier is separately DFT-s-OFDM modulated with other subcarriers.
An estimating unit 902, configured to estimate a downlink average received signal-to-noise ratio of the cell before the SSB is sent; and under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower than a first threshold value, the transmitting power of one SSB is increased by a preset first value on the basis of the basic transmitting power, and the transmitting power of one SSB is obtained.
The first reducing unit 903 is configured to reduce the transmission power of other frequency domain subcarriers so that the total transmission power of the frequency domain subcarriers of the transmission target time slot is not greater than a preset threshold, where the target time slot is a time slot where the SSB is located, and the other frequency domain subcarriers are frequency domain subcarriers outside the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the transmission target time slot.
A second reducing unit 904, configured to reduce a code rate of other frequency domain subcarriers, and/or change a modulation mode of the other frequency domain subcarriers from a first mode to a second mode; wherein the demodulation error probability of the first mode is greater than the demodulation error probability of the second mode.
The blanking unit 905 is configured to blank other frequency domain subcarriers, so that the total transmission power of the frequency domain subcarriers of the transmission target time slot is not greater than a preset threshold, the target time slot is the time slot in which the SSB is located, the other frequency domain subcarriers are a first number of frequency domain subcarriers except for the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the transmission target time slot, and the first number is determined according to the first value.
When the nulling unit 905 nulls other frequency-domain subcarriers, indication information is added to the MIB or SIB, where the indication information is used to indicate the position of the nulled other frequency-domain subcarriers.
In the SSB transmitting device, only one SSB is transmitted by one cell in one transmission period of the SSB, and the transmitting power of one SSB is the target transmitting power or the preset basic transmitting power, wherein the target transmitting power is greater than or equal to the basic transmitting power. In the technical scheme, in one SSB period, one cell only sends one SSB, so that the terminal can assume that the number of SSBs of the cell is 1 for detection, SSB merging operation is not needed, the complexity of terminal detection is reduced, and the detection accuracy is improved.
The present application also provides a base station 10 comprising: a processor 1001 and a memory 1002, the memory 1002 being configured to store a program, the processor 1001 being configured to execute the program to implement the SSB transmission method described in the above embodiment.
It should be noted that, the base station may be a base station in a ground gateway station in a satellite communication system, or an access network baseband processing unit (BBU).
The application also provides a communication system comprising a base station, a satellite and a terminal. The base station is configured to transmit one SSB to the satellite in one transmission period of the SSB, where the transmission power of the one SSB is a target transmission power or a preset base transmission power, the target transmission power is greater than or equal to the base transmission power, and the SSB subcarrier is separately DFT-s-OFDM modulated from other subcarriers. Satellites are used to broadcast SSBs to terminals. The terminal is configured to detect and perform PSS synchronization, SSS synchronization, and PBCH demodulation with only one SSB per transmission period of the SSB. Specifically, specific processes of detecting and performing PSS synchronization, SSS synchronization, and PBCH demodulation may be referred to in the prior art, and will not be described herein.
Optionally, the base station in the system is further configured to: estimating a downlink average received signal-to-noise ratio of a cell before transmitting an SSB to the satellite; and under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower than a first threshold value, the transmitting power of the SSB is increased by a preset first value on the basis of the basic transmitting power, and the target transmitting power of the SSB is obtained.
Further, in the case of increasing the transmission power of the SSB, the base station is further configured to: and reducing the transmitting power of other frequency domain subcarriers so that the total transmitting power of the frequency domain subcarriers of a transmitting target time slot is not more than a preset threshold, wherein the target time slot is the time slot where the SSB is positioned, and the other frequency domain subcarriers are frequency domain subcarriers outside the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the transmitting target time slot.
Further, the base station is further configured to: reducing the code rate of the other frequency domain subcarriers, and/or changing the modulation mode of the other frequency domain subcarriers from a first mode to a second mode; wherein the demodulation error probability of the first mode is greater than the demodulation error probability of the second mode.
Alternatively, in case of boosting the transmission power of the SSB, the base station is further configured to: and the other frequency domain subcarriers are emptied, so that the total transmitting power of the frequency domain subcarriers of a transmitting target time slot is not more than a preset threshold value, the target time slot is the time slot where the SSB is positioned, the other frequency domain subcarriers are the first number of frequency domain subcarriers except the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the transmitting target time slot, and the first number is determined according to the first value.
Further, the base station is further configured to: and adding indication information in the master information block MIB or the system information block SIB, wherein the indication information is used for indicating the positions of the other frequency domain subcarriers which are nulled.
Optionally, the base station sets the last four OFDM symbols of one slot occupied by the one SSB.
The present application also provides a computer-readable storage medium having instructions stored therein, which when run on a computer, cause the computer to perform the SSB transmission method described in the above embodiments.
The functions described in the methods of the present application, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computing device readable storage medium. Based on such understanding, a portion of the embodiments of the present application that contributes to the prior art or a portion of the technical solution may be embodied in the form of a software product stored in a storage medium, comprising several instructions for causing a computing device (which may be a personal computer, a server, a mobile computing device or a network device, etc.) to perform all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, so that the same or similar parts between the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A transmission method of a synchronous broadcast block SSB, comprising:
and in one transmission period of the SSB, only one SSB is transmitted, wherein the transmission power of the one SSB is target transmission power or preset basic transmission power, the target transmission power is larger than or equal to the basic transmission power, the lower the downlink average receiving signal-to-noise ratio of a cell is, the larger the difference value between the target transmission power and the basic transmission power is, and the SSB subcarrier and other subcarriers are separated for DFT-s-OFDM modulation, so that the DFT-s-OFDM modulation is independently carried out on the SSB subcarrier, and the peak-to-average ratio of a transmission signal is reduced.
2. The method of claim 1, further comprising, prior to said transmitting only one SSB:
estimating the downlink average receiving signal-to-noise ratio of the cell;
and under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower than a first threshold value, the transmitting power of the SSB is increased by a preset first value on the basis of the basic transmitting power, and the target transmitting power of the SSB is obtained.
3. The method as recited in claim 2, further comprising:
and reducing the transmitting power of other frequency domain subcarriers so that the total transmitting power of the frequency domain subcarriers of a transmitting target time slot is not more than a preset threshold, wherein the target time slot is the time slot where the SSB is positioned, and the other frequency domain subcarriers are frequency domain subcarriers outside the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the transmitting target time slot.
4. A method according to claim 3, further comprising:
reducing the code rate of the other frequency domain subcarriers, and/or changing the modulation mode of the other frequency domain subcarriers from a first mode to a second mode;
wherein the demodulation error probability of the first mode is greater than the demodulation error probability of the second mode.
5. The method as recited in claim 2, further comprising:
and the other frequency domain subcarriers are emptied, so that the total transmitting power of the frequency domain subcarriers of a transmitting target time slot is not more than a preset threshold value, the target time slot is the time slot where the SSB is positioned, the other frequency domain subcarriers are the first number of frequency domain subcarriers except the frequency domain subcarriers occupied by the SSB in the frequency domain subcarriers of the transmitting target time slot, and the first number is determined according to the first value.
6. The method as recited in claim 5, further comprising:
and adding indication information in the master information block MIB or the system information block SIB, wherein the indication information is used for indicating the positions of the other frequency domain subcarriers which are nulled.
7. The method of any of claims 1-6, wherein the one SSB occupies the last four OFDM symbols of one slot.
8. A communication system, comprising:
base stations, satellites, and terminals;
the base station is configured to send only one SSB to the satellite within one sending period of the SSB, where the sending power of the one SSB is a target sending power or a preset base sending power, the target sending power is greater than or equal to the base sending power, the lower the downlink average receiving signal-to-noise ratio of a cell is, the greater the difference between the target sending power and the base sending power is, and the SSB subcarrier is separately DFT-s-OFDM modulated with other subcarriers, so as to implement DFT-s-OFDM modulation on the SSB subcarrier alone, and reduce the peak-to-average ratio of a sending signal;
the satellite is used for broadcasting the SSB to the terminal;
the terminal detects and performs primary synchronization signal PSS synchronization, secondary synchronization signal SSS synchronization, and physical broadcast channel PBCH demodulation according to only one SSB per transmission period of the SSBs.
9. The system of claim 8, wherein the base station is further configured to:
estimating a downlink average received signal-to-noise ratio of a cell before transmitting an SSB to the satellite; and under the condition that the downlink average receiving signal-to-noise ratio of the cell is lower than a first threshold value, the transmitting power of the SSB is increased by a preset first value on the basis of the basic transmitting power, and the target transmitting power of the SSB is obtained.
10. A base station, comprising: a processor and a memory for storing a program; the processor is configured to run the program to implement the SSB transmission method of any one of claims 1 to 7.
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