Random Access Method, Random Access System, Device and Medium for Satellite Communication

Abstract

The present application discloses a random access method, a random access system, a device and a medium for satellite communication. The method includes: determining the total number of user equipments in a user equipment group, and selecting a plurality of pilot patterns from a pilot pattern library; selecting the optimal pilot pattern from the plurality of pilot patterns according to the success rate of each user equipment in the user equipment group accessing the satellite; and each user equipment in the user equipment group sending a pilot signal to the satellite according to the optimal pilot pattern. The present application improves the success rate of user equipments accessing the satellite.

Description

Technical Field

[0001] This application relates to the field of satellite Internet technology, and particularly to a random access method, a random access system, a device, and a medium for satellite communication. Background Art

[0002] The design of traditional satellite uplink access channels is restricted by time-frequency dimensions and may not be able to flexibly cope with different signal propagation conditions and interference situations in a dynamically changing environment. In satellite communication scenarios, the design of existing satellite uplink access channel hopping patterns does not consider using the spatial domain isolation ability provided by satellite beam scheduling. In the face of a high-density user situation, the satellite uplink access channel faces the problem of resource competition, thus affecting the success rate of random access. Summary of the Invention

[0003] In view of this, this application provides a random access method, a random access system, a device, and a medium for satellite communication.

[0004] This application discloses a random access method for satellite communication, which includes:

[0005] Determine the total number of user devices in the user device group, and select a plurality of pilot patterns corresponding to the user device group from the pilot pattern library; each of the pilot patterns is related to the total number of user devices, time, and frequency in the user device group;

[0006] Select the optimal pilot pattern from the plurality of pilot patterns according to the access success rate of each user device in the user device group to the satellite;

[0007] Each user device in the user device group sends a pilot signal to the satellite according to the optimal pilot pattern; the pilot signal is used to indicate a random access request sent by each user device in the user device group to the satellite.

[0008] Further, the method for obtaining the pilot pattern library is:

[0009] Establish a plurality of pilot patterns corresponding to the user device group according to the number of subcarriers, the subcarrier spacing, and the number of pilot signals sent by each user device in the user device group to the satellite each time;

[0010] Collect all the plurality of pilot patterns corresponding to the user device groups to form the pilot pattern library.

[0011] Further, the establishing a plurality of pilot patterns corresponding to the user device group according to the number of subcarriers, the subcarrier spacing, and the number of pilot signals sent by each user device in the user device group to the satellite each time includes:

[0012] Determine the total number of user equipments corresponding to each pilot pattern according to the number of user equipments in each of multiple cells, so as to establish several pilot patterns corresponding to the user equipment group; the multiple cells are within the same wave position in the satellite transmission beam; each pilot pattern is used to provide the time and frequency for all user equipments in the corresponding user equipment group to access the satellite.

[0013] Obtain the several pilot patterns according to the frequency and time for each user equipment in the user equipment group to access the satellite, and a preset frequency hopping rule; the preset frequency hopping rule is associated with different frequency hopping intervals.

[0014] Further, the establishing several pilot patterns corresponding to the user equipment group according to the number of subcarriers, the subcarrier interval, and the number of pilot signals sent by each user equipment in the user equipment group to the satellite each time includes:

[0015] Obtain the number of all user equipments in each wave position according to the number of wave positions within the satellite coverage, the area of each wave position, and the spatial density distribution function corresponding to each wave position.

[0016] Divide each wave position into multiple cells, and obtain the number of user equipments in each cell according to the number of all user equipments in each wave position.

[0017] Determine the number of user equipments corresponding to each pilot pattern according to the number of user equipments in each cell, the total frequency band resources allocated to each cell, the frequency band resources used by each pilot pattern, the total time resources allocated to each cell, and the time resources used by each pilot pattern.

[0018] Further, the method for obtaining the frequency and time for each user equipment in the user equipment group to access the satellite includes:

[0019] Obtain the frequency for each user equipment corresponding to each pilot pattern to access the satellite according to the number of subcarriers and the subcarrier interval.

[0020] Obtain the time for each user equipment corresponding to each pilot pattern to access the satellite according to the number of pilot signals sent by each user equipment corresponding to each pilot pattern to the satellite each time and the time required to send each pilot signal.

[0021] Further, the selecting the optimal pilot pattern from the several pilot patterns according to the access success rate of each user equipment in the user equipment group includes:

[0022] Obtain the access success rate of each user equipment in the user equipment group.

[0023] Select the optimal pilot pattern from the several pilot patterns corresponding to the user equipment group according to the success rate of each user equipment in the user equipment group accessing the satellite.

[0024] Further, obtaining the success rate of each user equipment in the user equipment group accessing the satellite includes:

[0025] Take the signal transmission response between each user equipment in the user equipment group and the satellite as the channel fading;

[0026] According to the channel fading and the signal-to-noise ratio, obtain the false detection rate of the satellite for the signals sent by each user equipment;

[0027] According to the false detection rate of the satellite for the signals sent by each user equipment, obtain the success rate of each user equipment in the user equipment group accessing the satellite.

[0028] Further, selecting the optimal pilot pattern from the several pilot patterns corresponding to the user equipment group according to the success rate of each user equipment in the user equipment group accessing the satellite includes:

[0029] Sum up the success rates of each user equipment in the user equipment group accessing the satellite, and find the maximum value of the summation result to select the optimal pilot pattern from the several pilot patterns corresponding to the user equipment group.

[0030] Further, summing up the success rates of each user equipment in the user equipment group accessing the satellite, and finding the maximum value of the summation result to select the optimal pilot pattern from the several pilot patterns corresponding to the user equipment group includes:

[0031] Sum up the success rates of each user equipment in the user equipment group accessing the satellite, and find the maximum value of the summation result under the premise of meeting the constraint conditions to select the optimal pilot pattern from the several pilot patterns corresponding to the user equipment group; the constraint conditions include the constraints on the number of all user equipment corresponding to each pilot pattern, the success rate of each user equipment corresponding to each pilot pattern accessing the satellite, and the interference between user equipment corresponding to each pilot pattern.

[0032] Further, each user equipment in the user equipment group sends the pilot signal to the satellite according to the optimal pilot pattern, including:

[0033] All user devices in each of the user device groups determine the time and frequency for sending the pilot signal to the satellite according to their corresponding optimal pilot patterns.

[0034] All user devices in each of the user device groups send the pilot signal to the satellite at the determined time and frequency.

[0035] Further, it further includes:

[0036] Input the pilot signals sent by all user devices in the user device group into a sub-band filter for sub-band filtering, and complete filter shaping to generate a baseband waveform.

[0037] After performing correlation processing on the baseband waveform, send it to the satellite; the correlation processing includes digital-to-analog conversion and radio frequency amplification.

[0038] Further, the method for configuring the sub-band filter includes:

[0039] Estimate the detection success rate of UFMC symbols according to the key parameters of the sub-band filter, the signal transmission response, and the signal peak-to-average ratio; the key parameters include type, length, number of sub-bands, and sideband suppression ratio.

[0040] Obtain the UFMC time efficiency according to the ratio of the length of the sub-band filter to the UFMC symbol.

[0041] Obtain the uplink random access channel capacity according to the detection success rate of the UFMC symbols and the UFMC time efficiency.

[0042] Obtain the key parameters of the optimized sub-band filter according to the uplink random access channel capacity.

[0043] Further, the obtaining the key parameters of the optimized sub-band filter according to the uplink random access channel capacity includes:

[0044] Maximize the uplink random access channel capacity under the premise of satisfying the preset constraint conditions to obtain the key parameters of the optimized sub-band filter; the preset constraint conditions include that the Hessian matrix is greater than zero, and the Hessian matrix is determined according to the uplink random access channel capacity.

[0045] Further, the method for obtaining the signal transmission response includes:

[0046] Obtain the signal transmission response according to the path loss, scintillation effect, atmospheric absorption, impulse response function of the transmission delay, transmission delay, Doppler frequency shift, TDL model in small-scale fading, influence of on-board radio frequency devices, and phased array antenna array response between the satellite and the user device.

[0047] The present application also discloses a random access system for satellite communication, which includes:

[0048] A pilot pattern selection module, configured to determine the total number of user equipments in a user equipment group, and select several pilot patterns corresponding to the user equipment group from a pilot pattern library; each of the pilot patterns is related to the total number, time, and frequency of the user equipments in the user equipment group;

[0049] An optimal pilot pattern selection module, configured to select the optimal pilot pattern from the several pilot patterns according to the access success rate of each user equipment in the user equipment group accessing the satellite;

[0050] A pilot signal sending module, configured to enable each user equipment in the user equipment group to send a pilot signal to the satellite according to the optimal pilot pattern; the pilot signal is used to indicate a random access request sent by each user equipment in the user equipment group to the satellite.

[0051] The present application also discloses an electronic device, including a memory and a processor, where the memory stores a computer program, and when the computer program is executed by the processor, the random access method for satellite communication described above is implemented.

[0052] The present application also discloses a computer-readable storage medium, where the computer-readable storage medium includes a computer program or instruction, and when the computer program or instruction runs on a computer, the computer is enabled to execute the random access method for satellite communication described above.

[0053] Due to the adoption of the above technical solution, the present application has the following advantages: in the satellite Internet of Things communication scenario, the random access success rate and resource utilization rate of the satellite uplink access channel are improved. Description of the Drawings

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present application, and those of ordinary skill in the art can also obtain other drawings according to these drawings.

[0055] Figure 1 It is a schematic flowchart of a random access method for satellite communication according to an embodiment of the present application;

[0056] FIG. 2(a) is a schematic diagram of an example of a pilot pattern with 1 user equipment quantity according to an embodiment of the present application;

[0057] Figure 2(b) is a schematic diagram of a pilot pattern example for three user equipment numbers in the embodiment of the present application;

[0058] Figure 3(a) is a schematic diagram of a pilot pattern example for six user equipment numbers in the embodiment of the present application;

[0059] Figure 3(b) is another schematic diagram of a pilot pattern example for six user equipment numbers in the embodiment of the present application;

[0060] Figure 3(c) is another schematic diagram of a pilot pattern example for six user equipment numbers in the embodiment of the present application;

[0061] Figure 4(a) is a schematic diagram of a pilot pattern example of 12 subcarriers for 12 user equipment numbers in the embodiment of the present application;

[0062] Figure 4(b) is a schematic diagram of a pilot pattern example of 36 subcarriers for 12 user equipment numbers in the embodiment of the present application;

[0063] Figure 5 is a curve graph showing the false detection rate of the narrowband physical random access channel in the embodiment of the present application changing with the signal-to-noise ratio;

[0064] Figure 6 is a block diagram of a random access system for satellite communication in the embodiment of the present application;

[0065] Figure 7 is a block diagram of an electronic device in the embodiment of the present application. Detailed implementation manners

[0066] The present application will be further described in conjunction with the accompanying drawings and embodiments. The described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art shall fall within the scope of protection of the embodiments of the present application.

[0067] The technical problem to be solved by this application is to improve the random access success rate and resource utilization rate of the satellite uplink access channel in the satellite Internet of Things communication scenario. During the service cycle of the satellite phased array agile beam, for the ground user equipment under different beams, there are differences and commonalities in their communication elevation angles, signal round-trip delays, Doppler frequency shifts, etc. Moreover, as the satellite moves, the channel conditions gradually change. By using the prior relative position information of the satellite and the receiving wave position, resources are reasonably and differentially allocated, and the spatial domain isolation brought by different beams and cell divisions is utilized to reduce interference and improve the overall time-frequency resource efficiency. In the current Internet of Things communication system, CP-OFDM (Cyclic Prefix Orthogonal Frequency Division Multiplexing) / SC-FDMA (Single-Carrier Frequency-Division Multiple Access) waveforms are generally adopted, and the use of the cyclic prefix seriously affects the time-frequency resource efficiency. As a candidate UFMC (Universal Filtered Multi-Carrier) waveform has certain time-frequency robustness without using the cyclic prefix, effectively improving the resource utilization efficiency. Therefore, how to realize the on-demand automatic adjustment of the sub-band filter parameters for generating the UFMC waveform is the key to solving the inflexible and low-efficiency utilization of the time-frequency resources of the satellite uplink access channel. The key problems are as follows:

[0068] (1)Design of the NPRACH (Narrowband Physical Random Access Channel) hopping pattern based on the satellite communication scenario: The NPRACH hopping pattern specified by the current 3GPP (3rd Generation Partnership Project) protocol distinguishes different random access user equipment through time-frequency resource division. In the satellite communication scenario, the isolation of different user equipment in the spatial domain can be achieved through different beam and cell divisions. Reasonably utilizing the characteristics of this scenario to construct a space-time-frequency hopping pattern is the key to improving the overall time-frequency resource efficiency.

[0069] (2)High-efficiency UFMC waveform with adaptive adjustment: For the currently widely used CP-OFDM waveform, since its cyclic prefix (CP) does not transmit additional effective information, there is room for improvement in signal utilization efficiency. As a candidate waveform for 5G, UFMC has a certain improvement in the utilization efficiency of time resources because it does not use CP. At the same time, under different filter parameter configurations, the anti-time-frequency offset ability of the UFMC waveform varies. Adjusting the UFMC filter parameter configuration in a timely manner according to different communication conditions is the key to efficiently realizing the inherent anti-interference ability of the UFMC waveform.

[0070] In view of the above technical problems, refer to Figure 1 , an embodiment of the present application provides a random access method for satellite communication, which includes:

[0071] Step 101, determine the total number of user devices in the user device group, and select several pilot patterns corresponding to the user device group from the pilot pattern library; each pilot pattern is related to the total number of user devices, time, and frequency in the user device group.

[0072] Each user device group consists of several user devices, and each user device group corresponds to several pilot patterns.

[0073] In an embodiment of the present application, the method for obtaining the pilot pattern library is: according to the number of subcarriers, subcarrier spacing, and the number of pilot signals sent by each user device in the user device group to the satellite each time, establish several pilot patterns corresponding to the user device group; the several pilot patterns corresponding to all user device groups together form the pilot pattern library.

[0074] In an embodiment of the present application, establishing several pilot patterns corresponding to the user device group according to the number of subcarriers, subcarrier spacing, and the number of pilot signals sent by each user device in the user device group to the satellite each time includes:

[0075] Determine the total number of user equipments corresponding to each pilot pattern according to the number of user equipments in each of multiple cells, so as to establish several pilot patterns corresponding to the user equipment groups; the multiple cells are located within the same wave position in the satellite transmission beam; each pilot pattern is used to provide the time and frequency for all user equipments in its corresponding user equipment group to access the satellite; obtain several pilot patterns according to the access frequency and time of each user equipment in the user equipment group to the satellite and a preset frequency hopping rule; the preset frequency hopping rule is associated with different frequency hopping intervals. Among them, several pilot patterns are designed for each user equipment group respectively, and each pilot pattern in the several pilot patterns is used to indicate the time and frequency for all user equipments in the user equipment group it serves (corresponds to) to access the satellite. Since the number of users in each cell is different in actual situations, corresponding pilot patterns are established for different application scenarios (different user equipment groups) respectively, so as to provide a reference for the user equipments in all cells that need to be served to access the satellite.

[0076] In an embodiment of the present application, several pilot patterns corresponding to the user equipment group are established according to the number of subcarriers, the subcarrier interval, and the number of pilot signals sent by each user equipment in the user equipment group to the satellite each time, including:

[0077] Obtain the number of all user equipments in each wave position according to the number of wave positions within the satellite coverage, the area of each wave position, and the spatial density distribution function corresponding to each wave position; divide each wave position into multiple cells, and obtain the number of user equipments in each cell according to the number of all user equipments in each wave position; determine the number of user equipments corresponding to each pilot pattern according to the number of user equipments in each cell, the total frequency band resources allocated to each cell, the frequency band resources used by each pilot pattern, the total time resources allocated to each cell, and the time resources used by each pilot pattern.

[0078] Specifically, based on the geographical distribution data of global user devices, the original data provided by authoritative data sources (such as ITU (International Telecommunication Union), GSMA (Global System for Mobile Communications Association), or IoT Analytics, etc.) can be combined, and GIS (Geographic Information System) can be used for data processing and spatial analysis to calculate the user device density per unit area globally and represent it as a spatial density distribution function. Specifically, first, obtain the geographical distribution information of user devices through authoritative data sources, including the number of devices and spatial locations in each region. Subsequently, with the help of GIS tools, divide the Earth's surface into multiple spatial units through geostatistical methods (such as grid division or Thiessen polygons), and calculate the device density of each unit. On this basis, introduce a statistical model, such as KDE (Kernel Density Estimation), to convert the discrete device location data into a continuous spatial density distribution, and finally form a global spatial density distribution function, denoted as 。

[0079] Suppose there are a total of assigned wave positions in the satellite Internet system, and the area of the th wave position is . Multiply it by the spatial density distribution function corresponding to the th wave position, and the number of user devices within the th wave position can be obtained.

[0080]

[0081] Divide the th wave position into cells. For simplicity of description, here it is assumed that the number of user devices in the cells within the th wave position is the same, denoted as . Then:

[0082]

[0083] Denote the number of devices served by each pilot pattern as . From the number of devices within the cell, the total frequency band resources assigned to the cell, and the frequency band resources (bandwidth) used by each pilot pattern 、The total time resources allocated to the cell 、The time resources used by each pilot pattern It is calculated, and the calculation formula is:

[0084]

[0085] Wherein, It is obtained from the upper-layer resource scheduling information, Referring to the current protocol, it is generally set to 45 kHz.

[0086] In an embodiment of the present application, a method for obtaining the frequency and time at which each user equipment in a user equipment group accesses a satellite includes:

[0087] According to the number of subcarriers and the subcarrier spacing, obtain the frequency at which each user equipment corresponding to each pilot pattern accesses the satellite; according to the number of pilot signals sent by each user equipment corresponding to each pilot pattern to the satellite each time and the time required to send each pilot signal, obtain the time at which each user equipment corresponding to each pilot pattern accesses the satellite.

[0088] Specifically, on the uplink from the user equipment to the satellite, multiple groups of different pilot signals are designed. Each group of pilot signals needs to set the frequency point, time interval, frequency interval, and the distribution of each frequency point of each group of pilot signals. Exemplarily, referring to Fig. 2(a), an embodiment of the present application gives a pilot pattern with 1 user equipment. The t on the abscissa represents time, the f on the ordinate represents frequency. The width of each rectangle represents the carrier spacing, the length of each rectangle is equal to 1 symbol duration, and the number of rectangles in each row on the time axis is equal to the number of symbols. Each colored rectangle indicates that the user equipment can send a pilot signal within the time and frequency corresponding to the colored rectangle. Each colored rectangle corresponds to one user equipment. In Fig. 2(a), in the direction of increasing time, the first colored rectangle to the fourth colored rectangle are a group, representing that the user equipment continuously sends 4 pilot signals to the satellite each time. Each time, a pilot signal is sent through one symbol, and the time duration for sending one pilot signal is the symbol duration in Table 1.

[0089] In the case of a small number of devices (not exceeding 12) in Fig. 2(a) and Fig. 2(b), a pilot pattern occupying 12 subcarriers can be designed, and the specific parameters are shown in Table 1.

[0090] Table 1 Pilot pattern parameters (12 subcarriers)

[0091]

[0092] Combined with Figure 2(a), the frequency hopping interval in Table 1 is 1→6→1 (a kind of frequency hopping rule). 1→6→1 means that the intervals between each group of transmitted pilot signals are 1 frequency interval, 6 frequency intervals, and 1 frequency interval in sequence. 1 frequency interval is equal to 1 subcarrier interval. The bandwidth in Table 1 refers to the bandwidth of the entire pilot pattern, which is equal to the subcarrier interval multiplied by the number of subcarriers. The frequency hopping period is the symbol duration multiplied by the number of symbols. 1 subcarrier interval corresponds to 1 subcarrier, that is, the number of subcarrier intervals is equal to the number of subcarriers.

[0093] It should be noted that for the relevant explanations of Figure 2(b), Figure 3(a), Figure 3(b), Figure 3(c), Figure 4(a), Figure 4(b), and Table 3, reference can be made to the above introduction of Figure 2(a) and Table 1.

[0094] In terms of specific design, taking the case of 1 user equipment quantity in Figure 2(a), that is, the total quantity of user equipment in the user equipment group is 1 as an example, its specific configuration is shown in Table 2:

[0095] Table 2 A pilot pattern example configuration in the case of 1 equipment quantity

[0096]

[0097] The frequency point serial number in Table 2 represents the serial number of each colored rectangle in the vertical direction from top to bottom (frequency from high to low). Time refers to the serial number of the colored rectangle in the horizontal axis direction from left to right. The frequency point hopping refers to the relative change between adjacent different frequency point serial number values. Example, the method for obtaining the relative frequency 3.75kHz corresponding to the frequency point serial number 1: Based on the relative frequency 7.5kHz of the frequency point 2, add the product of the frequency point hopping (-1) and the width of one colored rectangle (subcarrier interval 3.75kHz).

[0098] In the case of a large number of user equipments, when using a pilot pattern occupying 12 subcarriers as shown in Figure 4(a), there will be a certain congestion risk. Pilot patterns occupying 36 subcarriers (Figure 4(b)) or more subcarriers can be used. The specific parameters of the 36 - subcarrier pilot pattern are shown in Table 3.

[0099] Table 3 Pilot pattern parameters (36 subcarriers)

[0100]

[0101] In summary, according to the examples given in FIGS. 2(a), 2(b), 3(a), 3(b), 3(c), 4(a), and 4(b) above, different pilot patterns are designed for different user equipment groups, and a pilot pattern library with three-dimensional constraints of "equipment quantity - time - frequency" is established. The pilot pattern library consists of pilot patterns corresponding to different user equipment groups.

[0102] The embodiment of the present application makes full use of the advantage of spatial domain isolation provided by satellite phased array hopping beams in the satellite communication scenario, constructs a three-dimensional space-time-frequency hopping pattern, reduces the interference of user equipment between different beams and different cells, and makes full use of system resources; and adjusts the pilot pattern allocation according to the real-time information of user equipment random access, improving the success rate of user equipment accessing the satellite.

[0103] Step 102: Select the optimal pilot pattern from several pilot patterns according to the success rate of each user equipment in the user equipment group accessing the satellite.

[0104] In an embodiment of the present application, selecting the optimal pilot pattern from several pilot patterns according to the success rate of each user equipment in the user equipment group accessing the satellite includes: obtaining the success rate of each user equipment in the user equipment group accessing the satellite; and selecting the optimal pilot pattern from several pilot patterns corresponding to the user equipment group according to the success rate of each user equipment in the user equipment group accessing the satellite.

[0105] In an embodiment of the present application, obtaining the success rate of each user equipment in the user equipment group accessing the satellite includes: using the signal transmission response between each user equipment in the user equipment group and the satellite as channel fading; obtaining the false detection rate of the signal sent by each user equipment received by the satellite according to the channel fading and the signal-to-noise ratio; and obtaining the success rate of each user equipment in the user equipment group accessing the satellite according to the false detection rate of the signal sent by each user equipment received by the satellite.

[0106] In an embodiment of the present application, selecting the optimal pilot pattern from several pilot patterns corresponding to the user equipment group according to the success rate of each user equipment in the user equipment group accessing the satellite includes: summing up the success rates of each user equipment in the user equipment group accessing the satellite, and obtaining the maximum value of the summation result to select the optimal pilot pattern from several pilot patterns corresponding to the user equipment group.

[0107] In an embodiment of the present application, the success rates of each user device in the user device group accessing the satellite are summed, and the maximum value is obtained from the sum of the results, so as to select the optimal pilot pattern from several pilot patterns corresponding to the user device group, including: summing the success rates of each user device in the user device group accessing the satellite, and obtaining the maximum value from the sum of the results under the premise of meeting the constraint conditions, so as to select the optimal pilot pattern from several pilot patterns corresponding to the user device group; the constraint conditions include the constraints on the total number of all user devices corresponding to each pilot pattern, the success rate of each user device corresponding to each pilot pattern accessing the satellite, and the interference between user devices corresponding to each pilot pattern.

[0108] Specifically, let the total number of user devices in the user device group (i.e., the number of user devices served by each pilot pattern) be When there are pilot patterns, each pilot pattern is denoted as , . Each user device group corresponds to several pilot patterns.

[0109] Taking the number of accessible user devices , the access success rate of a single user device , the interference between user devices , etc. as constraint conditions, the optimal pilot combination corresponding to different user device groups is obtained. Among them, the access success rate of a single user device in the user device group needs to use the signal transmission response as the channel fading, and further solve or obtain the false detection rate of the uplink according to the simulation. According to the link budget formula, the signal-to-noise ratio is obtained from the channel fading; usually, the corresponding relationship between the signal-to-noise ratio and the false detection rate can be obtained according to the simulation, as shown in Figure 5 . The false detection rate of the uplink is obtained from the signal-to-noise ratio.

[0110] The optimal pilot combination is obtained by solving the optimization problem, and the mathematical expression of the optimization problem is as follows:

[0111]

[0112] Among them, is the pilot pattern (the target variable of the optimal solution) when the number of accessible user devices is . is the total number of pilot patterns corresponding to the number of accessible user devices being .

[0113] Constraint conditions:

[0114] a) Constraint on the total number of user devices in the user device group:

[0115]

[0116] b) Single user equipment access success rate constraint in the user equipment group:

[0117]

[0118] c) Interference constraint between user equipments in the user equipment group:

[0119]

[0120] Among them, is the accessible user equipment capacity of the system, is the access success rate of a single user equipment in the user equipment group, is the minimum requirement for the access success rate of a single user equipment in the user equipment group, is the user equipment in the user equipment group is the interference between user equipments suffered by it, is the maximum allowed interference between user equipments. The access success rate of a single user equipment in the user equipment group is the probability that the satellite successfully detects the random access request sent by the user equipment.

[0121] For the above-mentioned optimization problem, the Lagrangian dual method can be used for solution. First, construct the Lagrangian function, combine the optimization problem with the constraint conditions, and introduce the Lagrange multipliers. Then, by solving the dual problem of the Lagrangian function, maximize the Lagrangian function with respect to the optimization variables, and at the same time minimize the value of the dual function with respect to the Lagrange multipliers. Finally, by iteratively adjusting the Lagrange multipliers and combining the KKT (Karush-Kuhn-Tucker) conditions, find the optimal solution or approximate solution of the original problem, that is, obtain the optimal pilot pattern corresponding to all user equipments in the user equipment group.

[0122] Step 103: Each user equipment in the user equipment group sends a pilot signal to the satellite according to the optimal pilot pattern; the pilot signal is used to indicate the random access request sent by each user equipment in the user equipment group to the satellite.

[0123] In an embodiment of the present application, each user equipment in the user equipment group sends a pilot signal to the satellite according to the optimal pilot pattern, including: all user equipments in each user equipment group determine the time and frequency for sending the pilot signal to the satellite according to their corresponding optimal pilot patterns; all user equipments in each user equipment group send the pilot signal to the satellite at the determined time and frequency.

[0124] Embodiments of the present application are directed to the low-earth orbit satellite Internet of Things scenario. By integrating the satellite beam spatial domain isolation capability, a space-time-frequency hopping pattern is constructed to achieve performance improvements such as low latency, high random access success rate, and high-density access.

[0125] Embodiments of the present application further include:

[0126] Input the pilot signals sent by all user devices in the user device group into a subband filter for subband filtering, and complete filtering and shaping to generate a baseband waveform; after performing relevant processing on the baseband waveform, send it to the satellite; the relevant processing includes digital-to-analog conversion and radio frequency amplification.

[0127] In an embodiment of the present application, the method for configuring a subband filter includes: estimating the detection success rate of UFMC symbols according to the key parameters, signal transmission response, and signal peak-to-average ratio of the subband filter; the key parameters include type, length, number of subbands, and sideband suppression ratio; obtaining the UFMC time efficiency according to the ratio of the length of the subband filter to the UFMC symbol; obtaining the uplink random access channel capacity according to the detection success rate of the UFMC symbol and the UFMC time efficiency; obtaining the key parameters of the optimized subband filter according to the uplink random access channel capacity.

[0128] In an embodiment of the present application, obtaining the key parameters of the optimized subband filter according to the uplink random access channel capacity includes: maximizing the uplink random access channel capacity on the premise of satisfying the preset constraint conditions to obtain the key parameters of the optimized subband filter; the preset constraint conditions include that the Hessian matrix is greater than zero, and the Hessian matrix is determined according to the uplink random access channel capacity.

[0129] Specifically, first, according to the signal transmission response , the signal peak-to-average ratio and the key parameters of the subband filter (type , length , number of subbands B, sideband suppression ratio ), estimate the ideal detection success rate of the UFMC symbol:

[0130]

[0131] Among them, is the transmission delay, is the function for calculating the detection success rate;

[0132] Then, according to the ratio of the filter length to the symbol length , calculate the UFMC time efficiency :

[0133]

[0134] At this time, the uplink random access channel capacity C can be expressed as:

[0135]

[0136] Considering the positive definite condition of the Hessian matrix, the optimization of the uplink random access channel capacity is expressed as:

[0137]

[0138]

[0139] Among them, H is the Hessian matrix, is the gradient operator, is constrained by.

[0140] By adjusting the type and length of the subband filter, the number of subbands N, and the sideband rejection ratio , find the best balance between the detection success rate and the time efficiency, so that C reaches the maximum value. The parameters of the subband filter at the best balance point are the subband filter configurations required for the uplink obtained by solving.

[0141] This application embodiment considers the low-earth orbit satellite Internet of Things scenario, and conducts research on the adaptability of 5G / 6G air interface alternative waveforms in the low-earth orbit satellite Internet of Things link according to the optimization suggestions for multi-carrier waveforms in international 5G / 6G. The UFMC waveform without using CP is preferably selected to achieve a waveform design that meets the performance trade-offs of high short data packet transmission efficiency, low out-of-band radiation, and low complexity, as well as the optimal filter design suitable for the massive narrowband access low-earth orbit satellite Internet of Things scenario.

[0142] When the satellite Internet system is working, the user equipment in each wave position needs to select a pilot pattern that conforms to the signal transmission response of its wave position from its corresponding several pilot patterns, then configure the subband filter according to the pilot signal sent by the user equipment to the satellite, and complete the filtering and shaping to finally generate the baseband waveform.

[0143] The specific baseband UFMC waveform signal is expressed as follows:

[0144]

[0145] Among them, k refers to the kth symbol; m refers to the mth subcarrier; refers to the information for distinguishing user equipment of the mth subcarrier in the bth subband, which is determined by step 101; N is the number of points of the inverse Fourier transform; B is the total number of subbands; is the total number of subcarriers in the b-th subband; is the subband filter function of the b-th subband, which is specifically determined according to the type of the filter , length , sideband rejection ratio is determined, and the type of the filter , length and sideband rejection ratio can be calculated from the above embodiments.

[0146] In the embodiments of the present application, the UFMC waveform is selected as a new waveform for adapting to the random access pilot signal of the satellite Internet of Things. By using the advantage of not using a cyclic prefix, the time efficiency of the system is improved. The parameter range of the subband filter corresponding to the UFMC waveform is initially delimited for the Internet of Things frame structure. At the same time, considering the transmission delay, Doppler frequency shift, signal-to-noise ratio, and time efficiency, etc., the most suitable parameters of the subband filter corresponding to the UFMC waveform are determined, and the on-demand automatic adjustment of the UFMC waveform parameter configuration is realized according to the real-time feedback information.

[0147] In the above embodiments of the present application, the method for obtaining the signal transmission response includes: obtaining the signal transmission response according to the path loss, scintillation effect, atmospheric absorption, impulse response function of the transmission delay, transmission delay, Doppler frequency shift, TDL model in small-scale fading, influence of on-board radio frequency devices, and phased array antenna array response between the satellite and the user equipment.

[0148] Specifically, the signal transmission response can be obtained through the following method: according to the satellite orbit information, the satellite motion trajectory is calculated through the satellite Kepler orbit model; the signal transmission response from each position point in the satellite motion trajectory to the position point where the user equipment is located is calculated.

[0149] Specifically, according to the orbit information of the satellite, specifically the six orbital elements (i.e., right ascension of the ascending node, semi-major axis of the orbit, eccentricity of the orbit, argument of perigee, inclination of the orbit, true anomaly), the satellite motion trajectory can be calculated based on the SGP4 (Simplified General Perturbation Model 4) algorithm, which also includes the spatial position and velocity of the satellite at any moment. To calculate the signal transmission response, it is necessary to first determine the position of the satellite and the position point of the user equipment. The position coordinates of the satellite are converted from the Earth-Centered Inertial (ECI) coordinate system to the Earth-Centered, Earth-Fixed (ECEF) coordinate system, forming a coordinate in the ECEF coordinate system. The position point where the user equipment is located can be obtained after positioning by the global satellite navigation system built in the user equipment. On this basis, referring to relevant protocols such as ITU-R P.618, the signal transmission response is designed as follows:

[0150]

[0151] Among them, is the path loss, is the scintillation effect, is the atmospheric absorption, is the impulse response function of the transmission delay, is the transmission delay, is the Doppler frequency shift, is the TDL (tap delay line) model in small-scale fading, is the influence of spaceborne RF devices, is the phased array antenna array response.

[0152] Among them, the transmission delay has the following calculation formula:

[0153]

[0154] Among them, represents the elevation angle of transmission when the user equipment sends a signal to the satellite at time t, represents the speed of light, represents the radius of the earth, represents the satellite orbital altitude.

[0155] See Figure 6 , the embodiment of the present application also provides a random access system for satellite communication, which includes:

[0156] A pilot pattern selection module, configured to determine the total number of user equipments in a user equipment group, and select a plurality of pilot patterns corresponding to the user equipment group from a pilot pattern library; each of the pilot patterns is related to the total number, time, and frequency of the user equipments in the user equipment group;

[0157] An optimal pilot pattern selection module, configured to select the optimal pilot pattern from the plurality of pilot patterns according to the access success rate of each user equipment in the user equipment group to the satellite;

[0158] A pilot signal sending module, configured to enable each user equipment in the user equipment group to send the pilot signal to the satellite according to the optimal pilot pattern; the pilot signal is used to indicate a random access request sent by each user equipment in the user equipment group to the satellite.

[0159] See Figure 7 , the embodiment of the present application also provides an electronic device, including a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, it implements the random access method for satellite communication described in the above embodiment.

[0160] The embodiment of the present application also provides a computer-readable storage medium, which includes a computer program or instruction. When the computer program or instruction runs on a computer, it causes the computer to execute the random access method for satellite communication described in the above embodiment.

[0161] It should be noted that in various embodiments of the present application, the magnitudes of the serial numbers of the above processes do not mean the sequence of execution. The execution sequence of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0162] Those skilled in the art should clearly understand that for the convenience and brevity of description, the specific working processes of the random access system for satellite communication, the electronic device, and the computer-readable storage medium described in the above embodiments can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein.

[0163] Those of ordinary skill in the art can understand that all or part of the steps for implementing the above embodiments can be completed by hardware, or can be completed by a program instructing relevant hardware. The program can be stored in a computer-readable storage medium. The storage medium mentioned above can be a read-only memory, a magnetic disk, an optical disc, etc.

[0164] The above are only optional embodiments of the present application, which are only used to illustrate the technical solutions of the present application and not to limit them. Any modifications, equivalent replacements, improvements, etc. made to the specific implementation manners of the present application within the spirit and scope of the present application should be covered by the protection scope of the present application.

Claims

1. A random access method for satellite communication, characterized in that: include: Determine the total number of user equipments in the user equipment group, and select a number of pilot patterns corresponding to the user equipment group from a pilot pattern library; Each of the pilot patterns is related to the total number, time and frequency of user equipment in the user equipment group; The pilot pattern is established according to the total number of user equipments corresponding to each pilot pattern, and the total number of user equipments corresponding to each pilot pattern is determined according to the number of user equipments in each of the multiple cells; the multiple cells are located in the same wave position in the satellite transmission beam; each pilot pattern is used to provide time and frequency for all user equipments in the user equipment group corresponding to it to access the satellite; Selecting an optimal pilot pattern from the plurality of pilot patterns according to a success rate of each user equipment in the user equipment group accessing the satellite; Each user equipment in the user equipment group sends a pilot signal to the satellite according to the optimal pilot pattern; the pilot signal is used to indicate a random access request sent by each user equipment in the user equipment group to the satellite.

2. The random access method for satellite communication according to claim 1, characterized in that: Also includes: The pilot pattern library is formed by combining a plurality of pilot patterns corresponding to all the user equipment groups.

3. The random access method for satellite communication according to claim 2, characterized in that: Also includes: Obtaining the plurality of pilot patterns according to the frequency and time at which each user equipment in the user equipment group accesses the satellite and a preset frequency hopping rule; The preset frequency hopping rule is associated with different frequency hopping intervals.

4. The random access method for satellite communication according to claim 3, characterized in that: Determining the number of user equipments corresponding to each of the pilot patterns includes: According to the number of wave positions within the satellite coverage, the area of ​​each wave position, and the spatial density distribution function corresponding to each wave position, the number of all user equipment in each wave position is obtained; Divide each of the wave positions into a plurality of cells, and obtain the number of user equipment in each cell according to the number of all user equipment in each of the wave positions; The number of user devices corresponding to each pilot pattern is determined according to the number of user devices in each cell, the total frequency band resources allocated to each cell, the frequency band resources used by each pilot pattern, the total time resources allocated to each cell, and the time resources used by each pilot pattern.

5. The random access method for satellite communication according to claim 3, characterized in that: The method for acquiring the frequency and time at which each user equipment in the user equipment group accesses the satellite comprises: According to the number of subcarriers and the subcarrier spacing, obtaining a frequency at which each user equipment corresponding to each pilot pattern accesses the satellite; The time for each user equipment corresponding to each pilot pattern to access the satellite is obtained according to the number of pilot signals sent to the satellite by each user equipment corresponding to each pilot pattern and the time required to send each pilot signal.

6. The random access method for satellite communication according to claim 1, characterized in that: The selecting the best pilot pattern from the plurality of pilot patterns according to the success rate of each user equipment in the user equipment group accessing the satellite comprises: Obtaining a success rate of each user equipment in the user equipment group accessing a satellite; According to the success rate of each user equipment in the user equipment group accessing the satellite, an optimal pilot pattern is selected from the plurality of pilot patterns corresponding to the user equipment group.

7. The random access method for satellite communication according to claim 6, characterized in that: The obtaining the success rate of each user equipment in the user equipment group accessing the satellite includes: taking a signal transmission response between each user equipment in the user equipment group and the satellite as channel fading; Obtaining, according to the channel fading and the signal-to-noise ratio, an error detection rate of the satellite for the signal sent by each of the user equipments; The success rate of each user equipment in the user equipment group accessing the satellite is obtained according to the false detection rate of the signal sent by each user equipment received by the satellite.

8. The random access method for satellite communication according to claim 6, characterized in that: The selecting the best pilot pattern from the plurality of pilot patterns corresponding to the user equipment group according to the success rate of each user equipment in the user equipment group accessing the satellite comprises: The success rate of each user equipment in the user equipment group accessing the satellite is summed, and the maximum value of the summed result is obtained to select the best pilot pattern from the several pilot patterns corresponding to the user equipment group.

9. The random access method for satellite communication according to claim 8, characterized in that: The step of summing up the success rate of each user equipment in the user equipment group accessing the satellite and maximizing the summed result to select the best pilot pattern from the plurality of pilot patterns corresponding to the user equipment group includes: The success rate of each user equipment in the user equipment group accessing the satellite is summed, and the maximum value of the summation result is obtained under the premise of satisfying the constraint conditions, so as to select the optimal pilot pattern from the several pilot patterns corresponding to the user equipment group; the constraint conditions include constraints on the number of all user equipment corresponding to each pilot pattern, the success rate of each user equipment corresponding to each pilot pattern accessing the satellite, and the interference between the user equipment corresponding to each pilot pattern.

10. The random access method for satellite communication according to claim 1, characterized in that: Each user equipment in the user equipment group sends the pilot signal to the satellite according to the optimal pilot pattern, including: All user equipments in each user equipment group determine the time and frequency of sending the pilot signal to the satellite according to the corresponding optimal pilot pattern; All user equipments in each of the user equipment groups transmit the pilot signal to the satellite within the determined time and frequency.

11. The random access method for satellite communication according to any one of claims 1 to 10, characterized in that: Also includes: Inputting the pilot signal sent by all user equipments in the user equipment group to the satellite into a sub-band filter for sub-band filtering, completing filtering and shaping, and generating a baseband waveform; The baseband waveform is sent to the satellite after being processed by correlation; the correlation processing includes digital-to-analog conversion and radio frequency amplification.

12. The random access method for satellite communication according to claim 11, characterized in that: The method for configuring the sub-band filter comprises: Estimate the detection success rate of the UFMC symbol according to the key parameters of the subband filter, the signal transmission response and the signal peak-to-average ratio; the key parameters include type, length, number of subbands and sideband suppression ratio; Obtaining a UFMC time efficiency according to a ratio of a length of the subband filter to the UFMC symbol; Obtaining an uplink random access channel capacity according to the detection success rate of the UFMC symbol and the UFMC time efficiency; According to the uplink random access channel capacity, key parameters of the optimized subband filter are obtained.

13. The random access method for satellite communication according to claim 12, characterized in that: The step of obtaining the optimized key parameters of the subband filter according to the uplink random access channel capacity includes: Under the premise of satisfying preset constraints, the uplink random access channel capacity is maximized to obtain the optimized key parameters of the subband filter; the preset constraints include that the Hessian matrix is ​​greater than zero, and the Hessian matrix is ​​determined according to the uplink random access channel capacity.

14. The random access method for satellite communication according to claim 7 or 12, characterized in that: The method for obtaining the signal transmission response comprises: The signal transmission response is obtained according to the path loss between the satellite and the user equipment, the scintillation effect, the atmospheric absorption, the impulse response function of the transmission delay, the transmission delay, the Doppler frequency shift, the TDL model in the small-scale fading, the influence of the onboard radio frequency device, and the phased array antenna array response.

15. A random access system for satellite communication, characterized in that: include: A pilot pattern selection module, used to determine the total number of user equipments in a user equipment group, and select a number of pilot patterns corresponding to the user equipment group from a pilot pattern library; Each of the pilot patterns is related to the total number, time and frequency of user equipment in the user equipment group; The pilot pattern is established according to the total number of user equipments corresponding to each pilot pattern, and the total number of user equipments corresponding to each pilot pattern is determined according to the number of user equipments in each of the multiple cells; the multiple cells are located in the same wave position in the satellite transmission beam; each pilot pattern is used to provide time and frequency for all user equipments in the user equipment group corresponding to it to access the satellite; An optimal pilot pattern selection module, configured to select an optimal pilot pattern from the plurality of pilot patterns according to a success rate of each user equipment in the user equipment group accessing a satellite; A pilot signal sending module, configured for each user equipment in the user equipment group to send a pilot signal to the satellite according to the optimal pilot pattern; The pilot signal is used to indicate a random access request sent by each user equipment in the user equipment group to the satellite.

16. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the computer program is executed by the processor, the random access method for satellite communication according to any one of claims 1 to 14 is implemented.

17. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a computer program or an instruction. When the computer program or the instruction is executed on a computer, the computer is enabled to execute the random access method for satellite communication according to any one of claims 1 to 14.

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