CN114745764B - Feedback-based Beidou global short message access method - Google Patents
Feedback-based Beidou global short message access method Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000009826 distribution Methods 0.000 claims abstract description 5
- 238000009827 uniform distribution Methods 0.000 claims abstract description 4
- 238000010606 normalization Methods 0.000 claims description 20
- 238000004364 calculation method Methods 0.000 claims description 9
- 230000005251 gamma ray Effects 0.000 claims description 3
- 230000000903 blocking effect Effects 0.000 abstract description 21
- 238000004088 simulation Methods 0.000 description 5
- 230000009123 feedback regulation Effects 0.000 description 3
- 238000012935 Averaging Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W48/00—Access restriction; Network selection; Access point selection
- H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18513—Transmission in a satellite or space-based system
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18519—Operations control, administration or maintenance
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention discloses a Beidou global short message access method based on feedback, which comprises the following specific steps: step one, whether the user access is successful or not, counting the number of all accessed users by the satellite every epoch time length; step two, after the satellite statistics is completed, each satellite carries out weighted data processing on the number of the access users counted in a plurality of historical epoch intervals, and then forms information content as historical statistics access quantity, generates downlink information signals and broadcasts the users; and thirdly, each user terminal randomly generates a random number according to uniform distribution by taking information broadcast by the last epoch satellite as a reference, and selects a corresponding access satellite according to the position of the random number falling on a weight axis so as to realize distribution. Constellation resources are fully used through closed loop feedback, so that the balance degree is improved, and the access blocking rate of users is reduced.
Description
Technical Field
The invention relates to the technical field of satellite navigation, in particular to a Beidou global short message access method based on feedback.
Background
The users of the Beidou global short message are usually under multi-star coverage, and the users face the strategy problem of selecting one of a plurality of visible satellites as an access satellite when the users access the short message. The most commonly used star-choosing strategy at present is the elevation-first strategy. The elevation priority strategy cannot effectively utilize priori knowledge of satellite operation rules, so that partial regional users can access the same satellite in a large amount, and idle resources of other satellites cannot be effectively utilized, access blocking is caused, access probability is reduced, and overall efficiency of the system is also influenced.
The drawbacks of the elevation priority strategy are illustrated in fig. 1. The user group with high elevation angle to the satellite 1 is recorded as in the intersection of the coverage range of the satellite 1 and the coverage range of the satellite 2The user group with high elevation angle to satellite 2 is +.>The user group that does not overlap with other satellite coverage is denoted as lambda 1 And lambda (lambda) 2 Similarly get->λ 3 . Assuming that the users are evenly distributed, the user groups accessing the satellites 1, 2 and 3 are respectively +.>Under the condition that the overlapping area of the satellites 2 and 3 is smaller than that of the satellites 1 and 2, the magnitude relation of the access user quantity of each satellite is satellite 3>Satellite 1>Satellite 2, thus causing imbalance of overall resource allocation of the on-board system, with a corresponding access failure rate of satellite 3>Satellite 1>Satellite 2.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a Beidou global short message access method based on feedback, which fully uses constellation resources through closed loop feedback, improves the balance degree and reduces the access blocking rate of users. Performance simulation of different star selection strategies shows that compared with the conventional common elevation angle priority star selection strategy, the shunt star selection strategy based on feedback adjustment can reduce the blocking rate by more than 2.5% when the user access amount per hour is more than 25 ten thousand times, and simultaneously reduce the standard deviation of the selected times of each star by about 52%, thereby effectively improving the success rate of user access and the utilization rate of on-board resources.
The technical scheme of the invention is as follows: a Beidou global short message access method based on feedback comprises the following specific steps:
step one, when a user short message signal is accessed to a satellite, the satellite needs to capture the user short message signal, and after the user short message signal is successfully captured, the satellite decides whether to track and demodulate or discard the user according to the available number of uplink channels; whether the user access is successful or not, counting the number of all accessed users by the satellite every epoch time length;
step two, after the satellite statistics is completed, each satellite carries out weighted data processing on the number of the access users counted in a plurality of historical epoch intervals, and then forms information content as historical statistics access quantity, generates downlink information signals and broadcasts the users;
the specific method for each satellite to carry out weighted data processing on the number of the access users counted in the historical epoch intervals is as follows:
A. let the forward history epoch set be t= { T from the current time m ,t m-1 ,t m-2 ,t m-3 ,..}, defining a weighted formula as
Wherein t is m Representing a current epoch; l represents the historical epoch number of statistics;satellite S corresponding to representative epoch m-j+1 i Counting the access quantity; />Representing the weighted statistical value of the current moment;
B. weighting the epoch weight data set calculated by equation (1)Defining each element/>Signed variance gamma of (2) i Is that
Wherein: gamma ray i Representing a visible satellite S i Is a signed variance value of n, n representing the number of satellites in view of the user;
the weighted statistical value is converted by a signed variance formula, and the current signed variance value of each satellite can be obtained; when the signed variance value is a negative value, the smaller the value is, the smaller the number of users representing statistical weighting is, and when the users select in the current epoch, the higher the weight is; when the signed variance value is a positive value, the larger the value is, the more the number of users representing statistical weighting is, and the smaller the selection weight is;
C. and (3) carrying out dimensionalization on the data by adopting a maximum value expansion normalization method, wherein the calculation formula is as follows.
Wherein γ= { γ 1 ,γ 2 ,γ 3 ,...,γ n -representing the satellites in view S calculated by equation (2) i Is a signed variance set; n represents the number of satellites in view of the user; sigma is the maximum expansion normalization calculation method coefficient; w (w) svi Representing a visible satellite S i A result obtained after normalization of the weighted statistical value;
maximum value expansion normalized visible star weight set is W sv ＝{w sv1 ,w sv2 ,w sv3 ,...,w svn N is greater than or equal to 1, and the sum of the weight sets is 1;
step three, each user terminal randomly generates a random number between (0, 1) according to uniform distribution by taking information broadcast by the last epoch satellite as a reference, and selects a corresponding access satellite according to the position of the random number falling on a weight axis so as to realize distribution.
Further, in the step two, the global short message adopts the broadcasting of the downlink frame related to the downlink of the B2B.
Further, L represents a statistical history epoch number, and the actual value is taken when the forward history epoch number is less than 5, and 5 is taken when the forward history epoch number is greater than or equal to 5.
Further, the sigma is the maximum expansion normalization calculation method coefficient, and 4 is taken.
Further, the one epoch time length is 25-35s.
The beneficial effects of the invention are as follows: constellation resources are fully used through closed loop feedback, so that the balance degree is improved, and the access blocking rate of users is reduced. Performance simulation of different star selection strategies shows that compared with the conventional common elevation angle priority star selection strategy, the shunt star selection strategy based on feedback adjustment can reduce the blocking rate by more than 2.5% when the user access amount per hour is more than 25 ten thousand times, and simultaneously reduce the standard deviation of the selected times of each star by about 52%, thereby effectively improving the success rate of user access and the utilization rate of on-board resources.
The global short message adopts B2B downlink to broadcast relevant downlink frames, and under the condition of not changing a signal system, independent access user quantity information frames can be set up for counting the access quantity broadcast, so that the resource occupation amount of a downlink channel is very small, and other services are not influenced.
Drawings
FIG. 1 is a schematic diagram of resource imbalance of an on-board system under multi-star coverage;
FIG. 2 is a shunt star selection strategy based on feedback regulation;
FIG. 3 is a shunt star selection strategy weight axis based on feedback adjustment;
FIG. 4 is a graph of user access blocking rate under different star selection policies;
FIG. 5 shows the balance performance index under different star selection strategies;
fig. 6 shows the average selected times of all epochs of each satellite under different satellite selection strategies when the global access frequency is 30 ten thousand times/hour.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
A Beidou global short message access method based on feedback comprises the following steps:
step 1, whether the user access is successful or not, counting the number of all accessed users at regular intervals by the satellite;
step 2, after satellite statistics is completed, weighting operation is carried out on the access quantity after the statistics is completed to form historical statistics access quantity which is used as information content to generate downlink information signals, and broadcasting is carried out on users;
and 3, because the MEO satellite orbit running speed is slower, the user terminal can consider that the user distribution in the next epoch is the same as that of the last epoch in a short time, so that the user can randomly select satellites to a certain extent according to the information broadcast by the satellite in the last epoch as a reference, and the shunting is realized.
Because the user can influence the statistics in the step 1 after the star selection strategy is adjusted, the statistics result in the step 1 can influence the adjustment of the user star selection strategy in the step 3, thereby forming a feedback adjustment system. The purpose of feedback regulation is to perform access balance of each satellite as much as possible under the condition that satellite resources are certain, so that a large number of users can be prevented from intensively selecting the same satellite for access.
The respective steps are described in detail below.
A, counting the number of access users
When the user short message signal is accessed to the satellite, the satellite needs to capture the user short message signal, and after the user short message signal is successfully captured, the satellite decides whether to track and demodulate or discard the user according to the available number of uplink channels. Therefore, whether the user access is successful or not, the satellite can judge how many users access according to the number of the acquired correlation peaks. The relative number of satellite access users may reflect the size of the blocking probability for each satellite for the last epoch.
And after receiving the historical access statistics contained in the downlink information of each satellite, the user terminal calculates the access success rate. Under the condition of limited total resources on the satellites, the final purpose of satellite selection adjustment is to enable the access quantity of each satellite to be similar, namely, the balance of the access quantity of the system is realized.
B historical epoch statistical weighting
When a single epoch is used for feedback input, locality exists, and in order to consider the global property, a user side uses a plurality of satellite historical access statistics weights as statistics values. Since both the user and the satellite are in motion, the earlier the time of the historical epoch, the lower its confidence, the lower the weighting. The length of each epoch is denoted Δt, and this value takes 30s herein. Assume that starting from the current time, the set of forward history epochs is t= { T m ,t m-1 ,t m-2 ,t m-3 ,..}, defining a weighted formula as
Wherein t is m Representing a current epoch; l represents a statistical historical epoch number, herein taken as 5;satellite S corresponding to representative epoch m-j+1 i Counting the access quantity; />Representing the weighted statistics of the current time.
C signed variance calculation
In order to evaluate the resource balance of different satellites, the signed variance is used as a criterion, and the definition is as follows:
weighting the epoch weight data set calculated by equation (1)Defining each elementSigned variance gamma of (2) i Is that
Wherein: gamma ray i Representing a visible satellite S i And n represents the number of satellites in view of the user.
The positive and negative values of the signed variance γ represent the expected direction of deviation of the data element from the data set, and the magnitude thereof represents the degree of deviation. When the gamma sign is negative, it represents a smaller directional deviation from the mean value, and when the sign is positive, it represents a larger directional deviation from the mean value.
D normalization of access weight of each star
The weighted statistical value is converted by a signed variance formula, and the current signed variance value of each satellite can be obtained. When the signed variance value is a negative value, the smaller the value is, the smaller the number of users representing statistical weighting is, and when the users select in the current epoch, the higher the weight is; when the signed variance value is positive, the larger the value, the larger the number of users representing statistical weighting, and the smaller the selection weight.
The weighted statistics obtained for different epochs may be different and therefore the data needs to be dimensionalized. In the method presented herein, there are two goals for data dimensionalization: 1. normalizing the signed variance value to be within the range of [0,1], wherein the smaller the numerical value is, the larger the corresponding dimension is; 2. the signed variance value normalization result cannot appear 0, because under the weight of 0, the user does not select the satellite in the current epoch, so that the satellite in the current epoch is idle and does not accord with the expected balance of each satellite. From the system level, the weight will cause the result of the feedback system to oscillate severely, which deviates greatly from the equilibrium state.
Common dimensionalization methods include normalization, centralization, normalization, averaging, forward normalization, reverse normalization, summation normalization, square sum normalization and the like. None of the above methods meet the dimensionality requirements required herein. The dimensionalization method proposed herein is therefore maximum extension normalization, whose calculation formula is as follows.
Wherein γ= { γ 1 ,γ 2 ,γ 3 ,...,γ n -representing the satellites in view S calculated by equation (2) i Is a signed variance set; n represents the number of satellites in view of the user; sigma is the maximum expansion normalization calculation method coefficient, 4 is taken here; w (w) svi Representing a visible satellite S i And (5) weighting the result obtained after the normalization of the statistic value.
E user shunting star selection
And aiming at the visible satellite of the user, after maximum value expansion normalization is completed on the access statistic value of the visible satellite, random satellite selection of the user is performed according to the weight of the visible satellite. Maximum value expansion normalized visible star weight set is W sv ＝{w sv1 ,w sv2 ,w sv3 ,...,w svn N.gtoreq.1, the sum of the set of weights being 1. The weight axis is shown in fig. 3.
Each user terminal randomly generates a random number between (0, 1) according to uniform distribution, and selects a corresponding access satellite according to the position of the random number falling on a weight axis.
The simulation parameters were set as in table 1.
TABLE 1
Table 1 Simulation parameters
In the standard for judging the performance of the strategy, besides the blocking rate of the user access, a balance index Ba of the on-board channel is defined for measuring the balance performance of the system. The formula is defined as:
wherein: n (N) i For the selected times of satellite i in epoch time, M is the total satelliteNumber, herein 14; λ is the access frequency of the global users, and its physical value corresponds to the global number of user accesses per Δt time on average. The balance performance index Ba is normalized standard deviation, and the smaller the value is, the higher the representative balance is, and the more the on-board resources are balanced.
The user blocking rate results obtained according to the simulation parameters above are shown in fig. 4. The assumption of a theoretical optimal occlusion in fig. 4 is: the user star selection is completely balanced, namely all access users are evenly distributed to all satellites, and the access user quantity and the blocking rate of all satellites are the same, so that the blocking rate of a single star can be used for representing the whole blocking rate, and the blocking rate is calculated by a formula (5).
Where c represents the number of single star channels, λ represents the user access frequency of the star, L represents the user information length, and R represents the user information rate.
It can be seen that the elevation priority strategy behaves similarly in the case of a lower user access (10 tens of thousands of times per hour) than the other two strategies. But as the user access volume increases, the overall access blocking rate of the elevation priority policy begins to rise rapidly. And under the condition that the access quantity of the user quantity is larger (more than or equal to 25 ten thousand times per hour), the shunt star selection strategy based on feedback adjustment is lower than the elevation priority strategy by more than 2.5 percent. However, at higher user volumes, the user volumes increase and the gap between the blocking rate and the theoretical value of each policy also decreases, since at mainly large user volumes, the access blocking rate will be mainly limited by the overall shortage of resources on the satellite. At an access level of 50 ten thousand per hour, the method proposed herein is only 0.48% higher than the theoretical value.
FIG. 5 shows the balance performance index under different star selection strategies. Fig. 5 shows that there is little difference in the balance performance of the star selection strategies at different global user access volumes. Fig. 6 shows the average selected number of all epochs for each satellite at 30 tens of thousands of times per hour for global access, resulting in a larger elevation angle for individual satellites for surface users and a lower elevation angle for individual satellites due to non-uniformity in satellite-to-ground coverage. A large number of users select a few stars in a concentrated way, thus resulting in a high blocking rate. The two split-flow satellite selection strategies reduce the high access satellite weight, and improve the low access satellite weight to balance on-board resources to a certain extent, so that the blocking rate of access is reduced.
Because of the problem of uneven coverage, the split satellite selection strategy with the same weight does not consider that the visibility quantity of the surface users to each satellite is inconsistent, and satellite selection distribution is only carried out according to a hard rule, so that the improvement of the blocking rate and the balance improvement of the on-satellite resources by the strategy are relatively limited. And the shunt star selection strategy based on feedback regulation carries out near-real-time star selection strategy regulation through the feedback access quantity information of the satellites, the variance of the selected times of each star is reduced by about 52%, and better on-satellite resource balance is obtained, so that lower blocking rate is obtained.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (5)
1. A Beidou global short message access method based on feedback is characterized by comprising the following steps: the method comprises the following specific steps:
step one, when a user short message signal is accessed to a satellite, the satellite needs to capture the user short message signal, and after the user short message signal is successfully captured, the satellite decides whether to track and demodulate or discard the user according to the available number of uplink channels; whether the user access is successful or not, counting the number of all accessed users by the satellite every epoch time length;
step two, after the satellite statistics is completed, each satellite carries out weighted data processing on the number of the access users counted in a plurality of historical epoch intervals, and then forms information content as historical statistics access quantity, generates downlink information signals and broadcasts the users;
the specific method for each satellite to carry out weighted data processing on the number of the access users counted in the historical epoch intervals is as follows:
A. let the forward history epoch set be t= { T from the current time m ,t m-1 ,t m-2 ,t m-3 ,..}, defining a weighted formula as
Wherein t is m Representing a current epoch; l represents the historical epoch number of statistics;satellite S corresponding to representative epoch m-j+1 i Counting the access quantity; />Representing the weighted statistical value of the current moment;
B. weighting the epoch weight data set calculated by equation (1)Define each element->Signed variance gamma of (2) i Is that
Wherein: gamma ray i Representing a visible satellite S i Is a signed variance value of n, n representing the number of satellites in view of the user;
the weighted statistical value is converted by a signed variance formula, and the current signed variance value of each satellite can be obtained; when the signed variance value is a negative value, the smaller the value is, the smaller the number of users representing statistical weighting is, and when the users select in the current epoch, the higher the weight is; when the signed variance value is a positive value, the larger the value is, the more the number of users representing statistical weighting is, and the smaller the selection weight is;
C. the maximum value expansion normalization method is adopted to carry out dimensionalization on the data, and the calculation formula is as follows:
wherein γ= { γ 1 ,γ 2 ,γ 3 ,...,γ n -representing the satellites in view S calculated by equation (2) i Is a signed variance set; n represents the number of satellites in view of the user; sigma is the maximum expansion normalization calculation method coefficient; w (w) svi Representing a visible satellite S i A result obtained after normalization of the weighted statistical value;
maximum value expansion normalized visible star weight set is W sv ＝{w sv1 ,w sv2 ,w sv3 ,...,w svn N is greater than or equal to 1, and the sum of the weight sets is 1;
step three, each user terminal randomly generates a random number between (0, 1) according to uniform distribution by taking information broadcast by the last epoch satellite as a reference, and selects a corresponding access satellite according to the position of the random number falling on a weight axis so as to realize distribution.
2. The feedback-based Beidou global short message access method of claim 1 is characterized in that: in the second step, the global short message adopts B2B downlink to broadcast the relevant downlink frame.
3. The feedback-based Beidou global short message access method of claim 1 is characterized in that: and L represents the statistical historical epoch number, the actual value is taken when the forward historical epoch number is smaller than 5, and 5 is taken when the forward historical epoch number is larger than or equal to 5.
4. The feedback-based Beidou global short message access method of claim 1 is characterized in that: and the sigma is the maximum expansion normalization calculation method coefficient, and 4 is taken.
5. The feedback-based Beidou global short message access method of claim 1 is characterized in that: the duration of the one epoch is 25-35s.
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