CN111194037B - Airship deployment method and system based on stable airship ground coverage - Google Patents
Airship deployment method and system based on stable airship ground coverage Download PDFInfo
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Abstract
The invention discloses an airship deployment method and system based on stable airship ground coverage, belonging to the technical field of wireless mobile communication and comprising the following steps: s1: determining the deployment height of the airship; s2: classifying users; s3: judging the uncovered user set; s4: searching for an edge user; s5: adjusting the position of the airship so that more boundary users are covered; adjusting the position of the airship so that more interior users are covered; s7: updating the set of airship locations and the set of uncovered users. Aiming at the ship-ground communication scene of the space communication network, the invention minimizes the number of airships and optimizes the position of the airships to deploy the airships on the basis of ensuring that all target area users can be covered, meeting the call drop rate of the users in the hot spot area and guaranteeing the link quality of the users in the hot spot area.
Description
Technical Field
The invention relates to the technical field of wireless mobile communication, in particular to an airship deployment method and system based on stable airship ground coverage.
Background
The air base station is a powerful supplement of the ground mobile communication network, and can be applied to scenes which cannot be covered by the ground mobile communication network, such as non-land areas, emergency communication scenes and the like.
The airship as air base station can overcome the demerits of ground mobile communication system and satellite communication system, bear payload in certain scale, stay in the air in certain height from ground for long time and provide various fixed and mobile services to ground user. In order to enable an airship communication system to better provide communication service, the stability of an airship-ground communication link is of great importance, and from the perspective of space deployment of an airship, a deployment scheme can be studied to ensure that any user in a target area can normally communicate, and the number of airships is minimized, so that the network cost is reduced, and the benefit of the airship is maximized.
At present, the existing literature lacks research on airship deployment strategies, and more research is performed on LAP (Low-availability airborne platforms) and UAV (unmanned Aerial vehicle), and as the airship, the LAP and the UAV serve as air base stations in modern communication systems, the deployment methods have certain signal processing capabilities, approximately similar deployment heights and extremely strong similarities, the deployment methods of the LAP and the UAV have certain reference significance for airship deployment.
An analysis method is proposed in the journal of COMMUNICATIONS of the international institute of electrical and electronics engineers (IIEEE WIRELESS COMMUNICATIONS options, vol.3, No.6, demober 2014) to optimize the height of the LAP to provide the maximum LAP-to-ground communication network radio coverage, and a closed formula for predicting the probability of geometric line-of-sight between the LAP and a ground receiver is proposed, on the basis of which the analysis yields the optimal deployment height based on the tolerable maximum path loss and the urban environment statistical parameters. However, the method only obtains the relationship between the deployment height of a single LAP and the size of the coverage range of the air-ground link, and does not solve the problem of optimal deployment of multiple airships in a situation that a user area is large and multiple airships are needed to cover.
A distributed seamless coverage of multiple UAV air base stations is also mentioned in the journal of COMMUNICATIONS problems of the international institute of electrical and electronics engineers (IEEE COMMUNICATIONS LETTERS, vol.21, No.3, MARCH 2017). This article proposes a polynomial time continuous mbs (mobile Base stations) layout algorithm. However, the method only considers the full coverage of the target area, does not consider the problem that the communication requirement is large due to the fact that a hot spot area scene possibly exists, and cannot ensure the stability of user communication in the hot spot area. Therefore, an airship deployment method and system based on stable airship coverage are provided.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method aims at the ship-ground communication scene of a space communication network, and performs airship deployment by minimizing the number of airships and optimizing the positions of the airships on the basis of ensuring that all target area users can be covered, meeting the call drop rate of the users in the hot spot area and ensuring the link quality of the users in the hot spot area.
The invention solves the technical problems through the following technical scheme, and the invention comprises the following steps:
s1: determining airship deployment height
Analyzing the relation between the airship coverage height and the radius to obtain the airship deployment height under the conditions of determining the environmental constant and accepting the maximum road loss;
s2: classifying users
Dividing users into users in a hot spot area and users in a non-hot spot area according to a known user set, the position of each user in the user set, a user distribution area range and a hot spot area range, and initializing an uncovered user set, an airship set and an airship number;
s3: determining a set of uncovered users
Judging whether the uncovered user set is empty, if so, ending the deployment process, and outputting the airship set and each airship position set, otherwise, continuing the following steps;
s4: finding edge users
If the current deployment is the first airship, after the boundary users are found and arranged anticlockwise, storing all the boundary users in an array of bouns, and taking the initial point in the bouns as u0；
If the current deployment is the non-head airship, after the boundary users are found, arranging the new boundary users on the tail of the launch array according to the anticlockwise direction, and taking the first user of the current array as a new u-shaped user0；
S5: adjusting the position of the airship so that more boundary users are covered
Definition PprioAnd PsecRespectively, u is an covered user set and a user set needing to be covered0Incorporation of PprioAnd the rest users in the round are taken into PsecThen, the Cover function is called:
[v,Pprio]＝Cover(v,Pprio,Psec)
by Psec＝Uu\ { bound } update PsecThen pass { bound } - \ PprioAnd updating the round array.
S6: adjusting the position of the airship so that more interior users are covered
The boundary user set P that must be covered is obtained from step S5prioAdjusting the position of the airship again by calling the Cover function in S5 so that more interior users are covered;
s7: updating a set of airship locations and a set of uncovered users
Let the position of the mth airship be equal to the updated position v obtained in step S6, i.e.:
vm＝v；
will PprioNeutralization of vmA distance of rhAll users within and at rnhExcluding the users in the non-hotspot area from the uncovered user set, and dividing PprioNeutralization of vmA distance of rnhThe users in the hot spot areas are marked as the users in the non-hot spot areas again;
adding the newly deployed airship into the airship set, and adding 1 to the serial number m of the airship;
and returning to the step S3 again to judge whether the uncovered user set is empty or not until the deployment process is finished, obtaining the minimum number of airship sets and the position sets of the corresponding airships, and repeatedly and iteratively judging whether the uncovered user set is empty or not, so that the full coverage of the users and the stability of user communication are ensured.
Preferably, in step S1, in the ship-ground channel, the existence probability of the line-of-sight link (LoS) is:
where a and b are constants that depend on the environment, h is the height of the airship, and r is the distance between the point of projection of the airship on the ground and the ground user.
Preferably, the path loss of the line-of-sight link (LoS) and the non-line-of-sight link (NLoS) is respectively expressed as follows:
wherein f iscIs the carrier frequency, d is the distance between the airship and the ground user, c is the speed of light, ηLoSAnd ηNLoSThe extra loss, η, caused by shadow fading under LoS link and NLoS link conditions, respectivelyLoSAnd ηNLoSIs correlated with the numerical environment of (c).
Preferably, the average path loss of the ship-ground link is expressed as follows:
PL＝PLoS×LLoS+PNLoS×LNLoS
substituting the path loss expression of the LoS link, the path loss expression of the NLoS link and the existence probability expression of the line-of-sight link into the formula to obtain:
wherein the content of the first and second substances,
A＝ηLoS-ηNLoS
B＝20log(4πfc/c)+ηNLoS
in the context of white gaussian noise, the user received signal-to-noise ratio can be expressed as:
SNR(h,r)＝Pt-Pn-PL(h,r)
wherein, PtAnd PnThe minimum receiving signal-to-noise ratio requirement of a user can be converted into the maximum path loss acceptable by the user, and when the signal-to-noise ratio requirement of the user is known, the height h of the airship and the corresponding maximum coverage range can be obtained.
Preferably, in the step S2, the known user set is denoted as U, and the position of each user in the user set is denoted as wkInitializing the uncovered user set UuThe following were used:
Uu＝U
initializing airship set M as follows:
the initialization airship number m is as follows:
m＝1。
preferably, in the step S4, the boundary user is found through a convex hull algorithm.
Preferably, in the step S5, the specific operation process of the Cover function includes the following steps:
s51: judging whether the user set needing to be covered is empty or not; if yes, the operation of the Cover function is ended, the optimized airship position set and the user set needing to be covered are returned, and the users which can be covered are recorded;
otherwise, executing the following steps;
s52: judgment of PprioIf all the users are users in non-hotspot areas, the P is selectedsecNeutral and current PprioThe user distance exceeds 2rnhIs excluded from PsecA 1 is to PsecNeutral and current PprioThe user distance is less than rnhIs excluded from PsecAnd incorporate Pprio；
If the user in the hot spot area is included, the P is addedsecNeutral and current PprioThe user distance exceeds 2rhIs excluded from PsecA 1 is to PsecNeutral and current PprioThe user distance is less than rhIs excluded from PsecAnd incorporate Pprio；
S53: will PsecThe users in (b) are ranked according to the distance v, and whether the users can be covered is determined in this order, if the user closest to v can be covered, v is updated by the airship position obtained in step S3, and P is updatedprioAnd PsecUpdating is also carried out, and if the user closest to v cannot be covered, the Cover function is quitted.
Preferably, in step S53, when the user closest to v is the hotspot area user, the hotspot area user is associated with PprioUsing 1-center algorithm to find the position and radius of the smallest circle covering them, and rhMaking comparison, if r is less than or equal to rhThen the user can be covered, otherwise it cannot be covered;
when the user nearest to v is the user in the non-hotspot area, the user is matched with PprioAll non-hotspot region users in the system use the 1-center algorithm to find the position and radius of the smallest circle covering the non-hotspot region users, and the position and radius of the smallest circle and rnhMaking comparison, if r is less than or equal to rnhThen the user can be covered, otherwise it cannot be covered; after initial deployment of the airship and user determination of coverage, use of the 1-center algorithm is performedThe optimization operation of the Cover function enables the deployment position of the airship to be optimized and adjusted, more edges and internal users to be covered, the goal of minimum number of finally deployed airships is achieved, and the deployment cost is minimized.
The invention also provides an airship deployment system based on stable airship ground coverage, which comprises:
the deployment height determining module is used for analyzing the relation between the airship coverage height and the radius to obtain the airship deployment height under the conditions of determining the environmental constant and accepting the maximum road loss;
the user classification module is used for classifying users into hot spot region users and non-hot spot region users according to a known user set, the position of each user in the user set, a user distribution region range and a hot spot region range, and initializing an uncovered user set, an airship set and an airship number;
the judging module is used for judging whether the uncovered user set is empty or not, if so, the deployment process is ended, the airship set and the airship position sets are output, and if not, the following steps are continued;
the edge user searching module is used for searching the boundary users and storing all the boundary users in an array;
a first position adjustment module for adjusting the position of the airship such that more boundary users are covered;
a second position adjustment module for adjusting the position of the airship so that more interior users are covered;
the position updating module is used for updating the airship position set and the uncovered user set;
the central processing module is used for sending instructions to other modules to complete related actions;
the deployment height determining module, the user classifying module, the judging module, the edge user searching module, the first position adjusting module, the second position adjusting module and the position updating module are all electrically connected with the central processing module.
Compared with the prior art, the invention has the following advantages: the airship deployment method and the airship deployment system based on stable airship coverage firstly determine the deployment height of the airship according to the tolerable maximum road loss and other indexes, then deploy the airship from edge users by using a convex hull algorithm, gradually draw the airship towards the center of an area anticlockwise, comprehensively consider the user call drop rate index, repeatedly and iteratively judge whether an uncovered user set is empty or not, and ensure the full coverage of users and the stability of user communication; after the airship is initially deployed and the user is determined to be covered, optimization operation of the Cover function using the 1-center algorithm is performed, so that the deployment position of the airship is optimally adjusted, more edge and internal users are covered, the aim of minimizing the number of finally deployed airships is achieved, the deployment cost is minimized, and the airship is worthy of popularization and use.
Drawings
Fig. 1 is a model diagram of an airship deployment method based on stable coverage of a airship in a second embodiment of the invention;
fig. 2 is a diagram of the relationship between the airship height H and the coverage radius R under the condition of determining the road loss in the second embodiment of the invention;
FIG. 3 is a flowchart of an airship deployment method according to a second embodiment of the invention;
FIG. 4 is a flow chart of a Cover function in the airship deploying method according to the second embodiment of the present invention;
fig. 5 is an airship deployment simulation diagram under the determined parameters in the second embodiment of the invention.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
Example one
The embodiment provides a technical scheme: an airship deployment method based on stable airship ground coverage comprises the following steps:
s1: determining airship deployment height
Analyzing the relation between the airship coverage height and the radius to obtain the airship deployment height under the conditions of determining the environmental constant and accepting the maximum road loss;
s2: classifying users
Dividing users into users in a hot spot area and users in a non-hot spot area according to a known user set, the position of each user in the user set, a user distribution area range and a hot spot area range, and initializing an uncovered user set, an airship set and an airship number;
s3: determining a set of uncovered users
Judging whether the uncovered user set is empty, if so, ending the deployment process, and outputting the airship set and each airship position set, otherwise, continuing the following steps;
s4: finding edge users
If the current deployment is the first airship, after the boundary users are found, the boundary users are arranged in a counterclockwise mode; all boundary users are stored in an array bound, and the starting point in the bound is used as u0(ii) a In the method of the embodiment, the airship deployment direction is counterclockwise from outside to inside, so that the boundary users are arranged counterclockwise; if the airship is deployed from outside to inside clockwise, the boundary users are arranged clockwise;
if the current deployment is the non-head airship, after the boundary users are found, arranging the new boundary users on the tail of the launch array according to the anticlockwise direction, and taking the first user of the current array as a new u-shaped user0；
S5: adjusting the position of the airship so that more boundary users are covered
Definition PprioAnd PsecRespectively, u is an covered user set and a user set needing to be covered0Incorporation of PprioAnd the rest users in the round are taken into PsecThen, the Cover function is called:
[v,Pprio]＝Cover(v,Pprio,Psec)
by Psec＝Uu\ { bound } update PsecThen pass { bound } - \ PprioAnd updating the round array.
S6: adjusting the position of the airship so that more interior users are covered
From the step ofS5 obtaining boundary user set P that must be coveredprioAdjusting the position of the airship again by calling the Cover function in S5 so that more interior users are covered;
s7: updating a set of airship locations and a set of uncovered users
Let the position of the mth airship be equal to the updated position v obtained in step S6, i.e.:
vm＝v；
will PprioNeutralization of vmA distance of rhAll users within and at rnhExcluding the users in the non-hotspot area from the uncovered user set, and dividing PprioNeutralization of vmA distance of rnhThe users in the hot spot areas are marked as the users in the non-hot spot areas again;
adding the newly deployed airship into the airship set, and adding 1 to the serial number m of the airship;
and returning to the step S3 again to judge whether the uncovered user set is empty or not until the deployment process is finished, obtaining the minimum number of airship sets and the position sets of the corresponding airships, and repeatedly and iteratively judging whether the uncovered user set is empty or not, so that the full coverage of the users and the stability of user communication are ensured.
Specifically, in step S1, in the boat-ground channel, the existence probability of the line-of-sight link (LoS) is:
where a and b are constants that depend on the environment, h is the height of the airship, and r is the distance between the point of projection of the airship on the ground and the ground user.
Specifically, the path loss of the line-of-sight link (LoS) and the non-line-of-sight link (NLoS) is respectively expressed as follows:
wherein f iscIs the carrier frequency, d is the distance between the airship and the ground user, c is the speed of light, ηLoSAnd ηNLoSThe extra loss, η, caused by shadow fading under LoS link and NLoS link conditions, respectivelyLoSAnd ηNLoSIs correlated with the numerical environment of (c).
Specifically, the average path loss of the ship-ground link is expressed as follows:
PL＝PLoS×LLoS+PNLoS×LNLoS
substituting the path loss expression of the LoS link, the path loss expression of the NLoS link and the existence probability expression of the line-of-sight link into the formula to obtain:
wherein the content of the first and second substances,
A＝ηLoS-ηNLoS
B＝20log(4πfc/c)+ηNLoS
in the context of white gaussian noise, the user received signal-to-noise ratio can be expressed as:
SNR(h,r)＝Pt-Pn-PL(h,r)
wherein, PtAnd PnThe minimum receiving signal-to-noise ratio requirement of a user can be converted into the maximum path loss acceptable by the user, and when the signal-to-noise ratio requirement of the user is known, the height h of the airship and the corresponding maximum coverage range can be obtained.
Specifically, in the step S2, the known user set is denoted as U, and the position of each user in the user set is denoted as wkInitializing the uncovered user set UuThe following were used:
Uu＝U
initializing airship set M as follows:
the initialization airship number m is as follows:
m＝1。
specifically, in step S4, the complexity of finding the boundary user through the convex hull algorithm is low, and the algorithm requirement can be met, which is more suitable.
Specifically, in the step S5, the specific operation process of the Cover function includes the following steps:
s51: judging whether the user set needing to be covered is empty or not; if yes, the operation of the Cover function is ended, the optimized airship position set and the user set needing to be covered are returned, and the users which can be covered are recorded;
otherwise, executing the following steps;
s52: judgment of PprioIf all the users are users in non-hotspot areas, the P is selectedsecNeutral and current PprioThe user distance exceeds 2rnhIs excluded from PsecA 1 is to PsecNeutral and current PprioThe user distance is less than rnhIs excluded from PsecAnd incorporate Pprio；
If the user in the hot spot area is included, the P is addedsecNeutral and current PprioThe user distance exceeds 2rhIs excluded from PsecA 1 is to PsecNeutral and current PprioThe user distance is less than rhIs excluded from PsecAnd incorporate Pprio；
S53: will PsecThe users in (b) are ranked according to the distance v, and whether the users can be covered is determined in this order, if the user closest to v can be covered, v is updated by the airship position obtained in step S3, and P is updatedprioAnd PsecUpdating is also carried out, and if the user closest to v cannot be covered, the Cover function is quitted.
In particular, the method comprises the following steps of,in step S53, when the user closest to v is the hotspot area user, the user is associated with PprioUsing 1-center algorithm to find the position and radius of the smallest circle covering them, and rhMaking comparison, if r is less than or equal to rhThen the user can be covered, otherwise it cannot be covered;
when the user nearest to v is the user in the non-hotspot area, the user is matched with PprioAll non-hotspot region users in the system use the 1-center algorithm to find the position and radius of the smallest circle covering the non-hotspot region users, and the position and radius of the smallest circle and rnhMaking comparison, if r is less than or equal to rnhThen the user can be covered, otherwise it cannot be covered; after the airship is initially deployed and the user is determined to be covered, optimization operation of the Cover function using the 1-center algorithm is performed, so that the deployment position of the airship is optimally adjusted, more edge and interior users are covered, the aim of minimizing the number of finally deployed airships is achieved, and the deployment cost is minimized.
The present embodiment also provides an airship deployment system based on stable coverage of an airship ground, including:
the deployment height determining module is used for analyzing the relation between the airship coverage height and the radius to obtain the airship deployment height under the conditions of determining the environmental constant and accepting the maximum road loss;
the user classification module is used for classifying users into hot spot region users and non-hot spot region users according to a known user set, the position of each user in the user set, a user distribution region range and a hot spot region range, and initializing an uncovered user set, an airship set and an airship number;
the judging module is used for judging whether the uncovered user set is empty or not, if so, the deployment process is ended, the airship set and the airship position sets are output, and if not, the following steps are continued;
the edge user searching module is used for searching the boundary users and storing all the boundary users in an array;
a first position adjustment module for adjusting the position of the airship such that more boundary users are covered;
a second position adjustment module for adjusting the position of the airship so that more interior users are covered;
the position updating module is used for updating the airship position set and the uncovered user set;
the central processing module is used for sending instructions to other modules to complete related actions;
the deployment height determining module, the user classifying module, the judging module, the edge user searching module, the first position adjusting module, the second position adjusting module and the position updating module are all electrically connected with the central processing module.
Example two
As shown in fig. 1 to 5, in the present embodiment, in a ground communication scene composed of users in a hot spot area and users in a non-hot spot area, the height of an airship is required to be 20 to 25km, the distance between airships is required to be 20 to 400km, environmental constants a and b for the environment are respectively 9.61 and 0.16, extra losses caused by shadow fading and the like in the case of an LoS link and an NLoS link are respectively 1dB and 20dB, and a carrier frequency is 40 GHz.
The environmental parameters are related to the following three urban environmental statistical parameters, which are respectively:
α: representing the ratio (dimensionless) of the area of the construction land to the total area of the land;
beta: represents the average number of buildings per unit area (buildings/km 2);
γ: a scale parameter representing the distribution of building heights described according to the rayleigh probability density function:
f(H)＝(H/γ2)exp(-H2/2γ2) Where H is the building height in meters.
The LOS probability can be obtained according to several parameters, and the related S curve is fitted, and a and b are related fitting parameters
Number, related to LoS probability.
Specific parameter settings are shown in table 1. The airship deployment scheme is obtained through airship deployment method simulation, and the performance of the airship deployment method provided by the invention is examined from two aspects of the number of deployed airships and the call drop rate of users.
TABLE 1 concrete parameter settings table
The embodiment sequentially executes the following operation steps according to an airship deployment method:
the first step is as follows: and analyzing the relation between the deployment height and the coverage radius of the airship to obtain the deployment height of the airship under the conditions of determining the environmental constant and accepting the maximum road loss. According to the example condition parameters: environment constants of 9.61 and 0.16, tolerable maximum path loss RlossExtra loss η due to shadow fading, etc. in case of 157dB, LoS linkLoS1dB, extra loss η caused by shadow fading in case of NLoS link, etcNLoS20dB, carrier frequency fc＝40GHz。
Can be based on:
wherein the content of the first and second substances,
A＝ηLoS-ηNLoS (2)
B＝20log(4πfc/c)+ηNLoS (3)
the relationship between the analyzed airship deployment height and the coverage radius is shown in fig. 2, and the optimal deployment height of the airship at this time can be obtained from the graph as 25 km.
The second step is that: knowing the position w of the set of users U, each user k ∈ UkUser distribution area range (x)min，xmax，ymin，ymax) Different small areas of the user in the whole area can be obtainedThe density of the user distribution is greater than a threshold value, the density is a hot spot area, the users belonging to the area are hot spot area users, the density is less than a threshold value, the density is a non-hot spot area, and the users belonging to the area are non-hot spot area users;
and initializes the uncovered user set Uu：
Uu＝U (4)
Initializing an airship set M:
and finally, initializing an airship number m:
m＝1。 (6)
the third step: judging whether to use
Namely judging whether the uncovered user set is empty or not; if the airship is empty, ending the method flow, and outputting the airship set and the airship position sets; if not, the following steps are continued.
The fourth step: searching for an edge user; if the first airship is deployed, finding boundary users through a convex hull algorithm, storing the users in an array of boots according to anticlockwise arrangement, and taking the starting point in each boot as u0；
If the first airship is not deployed, the boundary users are still searched through the convex hull algorithm, the new boundary users are arranged at the tail of the launch array according to the original sequence, and the first user of the current array is taken as a new u0。
The fifth step: the airship is positioned so that as many boundary users as possible are covered (preventing the situation where a single boundary user requires a single airship to be covered). Definition PprioAnd PsecRespectively, a set of covered users and a set of users that need to be covered. Will u0Incorporation of PprioAnd bring other users in the roundPsecThen, the Cover function is called:
[v,Pprio]＝Cover(v,Pprio,Psec) (7)
by passing
Psec＝Uu\{boun} (8)
To update PsecThen pass through
{boun}＝{boun}\Pprio (9)
To update the round array.
And a sixth step: after the last step, a boundary user set P which must be covered is obtainedprioAt this point, the Cover function is called again:
[v,Pprio]＝Cover(v,Pprio,Psec) (10)
to adjust the position of the airship so that as many interior users as possible are covered.
The seventh step: first let the position of the mth airship be equal to the position v updated after the sixth operation, i.e.:
vm＝v (11)
then P is putprioNeutralization of vmA distance of rhAll users within and at rnhUser exclusion of U from non-hotspot area withinuAnd is combined with PprioNeutralization of vmA distance of rnhThe users in the hot spot areas are marked as the users in the non-hot spot areas again. And adding the newly deployed airship into the airship set M, namely:
M＝M∪{m} (12)
and finally, adding 1 to the serial number m of the airship:
m＝m+1， (13)
and returning to the step three again to judge whether the uncovered user set is empty or not until the flow is finished, and obtaining the minimum number of airship sets and the position sets of the corresponding airships.
As shown in fig. 1, the model diagram of the airship deployment method based on stable airship coverage in this embodiment is shown, where ground users are divided into users in a hot spot area and users in a non-hot spot area, and the model diagram shows that the airship is deployed as little as possible above the user area to achieve full coverage of the user and meet communication requirements of all users, and in order to ensure stability of user communication, the dropped call rate of the user in the hot spot area is lower than a certain threshold.
As shown in fig. 2, when the parameters are set to a 9.61 and b 0.16, η is used to determine the relationship between the airship height H and the coverage radius R in the case of road lossLoS＝1dB，ηNLoS＝20dB，fcAt 40GHz, the maximum path loss R acceptable to the user is assumed, respectivelylossUnder the conditions of 155dB, 155dB and 157dB, the relation between the height H of the airship and the coverage radius R is obtained, namely the corresponding maximum coverage range of the height of the airship under the height, so that the maximum tolerable path loss is determined to be RlossAnd when the height is 157dB, the deployment height of the airship is 25km, and the requirement of 20-25 km of the flying height of the airship is met.
As shown in fig. 3, a flowchart of an airship deployment method is shown, in which a first step of specific operation steps determines a deployment height of an airship, and then main specific operations from a second step to a seventh step are shown in the flowchart, and after the flow operation is performed. The least number of deployed airship sets and the location sets of each airship are obtained.
As shown in fig. 4, the flowchart of the Cover function in the airship deploying method relates to the need of performing relevant operations through the Cover function in the fifth step and the sixth step in the specific operation steps of the airship deploying, and is a flowchart of the Cover function, after the operations of the flowchart, the deployment position of the airship can be optimally adjusted, more boundaries and internal users are covered, and the adjusted airship position and the covered user set are returned.
As shown in fig. 5, for an airship deployment simulation diagram under certain parameters, according to the airship height requirement of 20-25 km, the distance between airships of 20-400 km, the environmental constants a and b of 9.61 and 0.16, respectively, and the extra loss caused by shadow fading and the like under LoS link and NLoS link conditions of 1dB and 20dB, respectivelydB, carrier frequency of 40GHz, drop call rate requirement index epsilon of 0.99, and tolerable maximum path loss RlossIs 157 dB. After the airship deployment method and the corresponding operation of the Cover function, the graph is obtained, the airship deployment height is determined to be 25km, wherein black hollow dots represent users in non-hot-spot areas, black small solid dots represent users in hot-spot areas, gray large solid dots represent the airship, black large circles represent the coverage range of the airship when the maximum coverage radius is larger, and concentric circles and small circles of the black large circles represent the coverage range meeting the stable coverage radius of the airship at the probability of 0.99.
In summary, in the airship deployment methods and systems based on stable coverage of the airship in the two groups of embodiments, the deployment height of the airship is determined according to the tolerable maximum road loss and other indexes, then the airship deployment is performed from the edge users by using the convex hull algorithm, the airship gradually approaches the center of the area anticlockwise, the drop call rate index of the user is considered comprehensively, and repeated iteration is performed to judge whether the uncovered user set is empty, so that the full coverage of the user and the stability of user communication are ensured; after the airship is initially deployed and the user is determined to be covered, optimization operation of the Cover function using the 1-center algorithm is performed, so that the deployment position of the airship is optimally adjusted, more edge and internal users are covered, the aim of minimizing the number of finally deployed airships is achieved, the deployment cost is minimized, and the airship is worthy of popularization and use.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. An airship deployment method based on stable airship ground coverage is characterized by comprising the following steps:
s1: determining airship deployment height
Analyzing the relation between the airship coverage height and the radius to obtain the airship deployment height under the conditions of determining the environmental constant and accepting the maximum road loss;
s2: classifying users
Dividing users into users in a hot spot area and users in a non-hot spot area according to a known user set, the position of each user in the user set, a user distribution area range and a hot spot area range, and initializing an uncovered user set, an airship set and an airship number;
s3: determining a set of uncovered users
Judging whether the uncovered user set is empty, if so, ending the deployment process, and outputting the airship set and each airship position set, otherwise, continuing the following steps;
s4: finding edge users
If the current deployment is the first airship, after the boundary users are found and arranged anticlockwise, storing all the boundary users in an array of bouns, and taking the initial point in the bouns as u0；
If the current deployment is the non-head airship, after the boundary users are found, arranging the new boundary users on the tail of the launch array according to the anticlockwise direction, and taking the first user of the current array as a new u-shaped user0；
S5: adjusting the position of the airship so that more boundary users are covered
Definition PprioAnd PsecRespectively, u is an covered user set and a user set needing to be covered0Incorporation of PprioAnd the rest users in the round are taken into PsecThen, the Cover function is called:
[v,Pprio]＝Cover(v,Pprio,Psec)
by Psec＝Uu\ { bound } update PsecThen pass { bound } - \ PprioUpdating the round array;
s6: adjusting the position of the airship so that more interior users are covered
The boundary user set P that must be covered is obtained from step S5prioAdjusting the position of the airship again by calling the Cover function in S5 so that more interior users are covered;
s7: updating a set of airship locations and a set of uncovered users
Let the position of the mth airship be equal to the updated position v obtained in step S6, i.e.:
vm＝v；
will PprioNeutralization of vmA distance of rhAll users within and at rnhExcluding the users in the non-hotspot area from the uncovered user set, and dividing PprioNeutralization of vmA distance of rnhThe users in the hot spot areas are marked as the users in the non-hot spot areas again;
adding the newly deployed airship into the airship set, and adding 1 to the serial number m of the airship;
and returning to the step S3 again to judge whether the uncovered user set is empty or not until the deployment process is finished, and obtaining the minimum number of airship sets and the position sets of the corresponding airships.
2. The airship deployment method based on stable coverage of a ship ground according to claim 1, characterized by: in step S1, in the ship-ground channel, the existence probability of the line-of-sight link (LoS) is:
where a and b are constants that depend on the environment, h is the height of the airship, and r is the distance between the point of projection of the airship on the ground and the ground user.
3. The airship deployment method based on stable coverage of a ship ground according to claim 2, characterized by: the path loss of the line-of-sight link (LoS) and the non-line-of-sight link (NLoS) is respectively expressed as follows:
wherein f iscIs the carrier frequency, d is the distance between the airship and the ground user, c is the speed of light, ηLoSAnd ηNLoSThe extra loss, η, caused by shadow fading under LoS link and NLoS link conditions, respectivelyLoSAnd ηNLoSIs correlated with the numerical environment of (c).
4. The airship deployment method for stable coverage based on the airship according to claim 3, characterized by: the average path loss for the ship-ground link is expressed as follows:
PL＝PLoS×LLoS+PNLoS×LNLoS
substituting the path loss expression of the LoS link, the path loss expression of the NLoS link and the existence probability expression of the line-of-sight link into the formula to obtain:
wherein the content of the first and second substances,
A＝ηLoS-ηNLoS
B＝20log(4πfc/c)+ηNLoS
in the context of white gaussian noise, the user received signal-to-noise ratio can be expressed as:
SNR(h,r)＝Pt-Pn-PL(h,r)
wherein, PtAnd PnRespectively, transmit power and average noise power.
5. The airship deployment method based on stable coverage of a ship ground according to claim 4, characterized by: the lowest receiving signal-to-noise ratio requirement of a user is equivalently converted into the maximum path loss acceptable by the user, and when the signal-to-noise ratio requirement of the user is known, the height h of the airship and the corresponding maximum coverage range can be obtained.
6. The airship deployment method based on stable coverage of a ship ground according to claim 1, characterized by: in the step S2, the known user set is denoted as U, and the position of each user in the user set is denoted as wkInitializing the uncovered user set UuThe following were used:
Uu＝U
initializing airship set M as follows:
the initialization airship number m is as follows:
m＝1。
7. the airship deployment method based on stable coverage of a ship ground according to claim 1, characterized by: in step S4, the boundary user is found by the convex hull algorithm.
8. The airship deployment method based on stable coverage of a ship ground according to claim 1, characterized by: in step S5, the specific operation process of the Cover function includes the following steps:
s51: judging whether the user set needing to be covered is empty or not; if yes, the operation of the Cover function is ended, the optimized airship position set and the user set needing to be covered are returned, and the users which can be covered are recorded;
otherwise, executing the following steps;
s52: judgment of PprioIf all the users are users in non-hotspot areas, the P is selectedsecNeutral and current PprioThe user distance exceeds 2rnhIs excluded from PsecA 1 is to PsecNeutral and current PprioThe user distance is less than rnhIs excluded from PsecAnd incorporate Pprio；
If the user in the hot spot area is included, the P is addedsecNeutral and current PprioThe user distance exceeds 2rhIs excluded from PsecA 1 is to PsecNeutral and current PprioThe user distance is less than rhIs excluded from PsecAnd incorporate Pprio；
S53: will PsecThe users in (b) are ranked according to the distance v, and whether the users can be covered is determined in this order, if the user closest to v can be covered, v is updated by the airship position obtained in step S3, and P is updatedprioAnd PsecUpdating is also carried out, and if the user closest to v cannot be covered, the Cover function is quitted.
9. The airship deployment method for stable coverage based on the airship according to claim 8, characterized by: in step S53, when the user closest to v is the hotspot area user, the user is associated with PprioUsing 1-center algorithm to find the position and radius of the smallest circle covering them, and rhMaking comparison, if r is less than or equal to rhThen the user can be covered, otherwise it cannot be covered;
when the user nearest to v is the user in the non-hotspot area, the user is matched with PprioAll non-hotspot region users in the system use the 1-center algorithm to find the position and radius of the smallest circle covering the non-hotspot region users, and the position and radius of the smallest circle and rnhMaking comparison, if r is less than or equal to rnhThen the user may be covered, otherwise it cannot.
10. An airship deployment system based on stable airship ground coverage, wherein the airship deployment method according to any one of claims 1-9 is used for airship deployment work, and the airship deployment system comprises:
the deployment height determining module is used for analyzing the relation between the airship coverage height and the radius to obtain the airship deployment height under the conditions of determining the environmental constant and accepting the maximum road loss;
the user classification module is used for classifying users into hot spot region users and non-hot spot region users according to a known user set, the position of each user in the user set, a user distribution region range and a hot spot region range, and initializing an uncovered user set, an airship set and an airship number;
the judging module is used for judging whether the uncovered user set is empty or not, if so, the deployment process is ended, the airship set and the airship position sets are output, and if not, the following steps are continued;
the edge user searching module is used for searching the boundary users and storing all the boundary users in an array;
a first position adjustment module for adjusting the position of the airship such that more boundary users are covered;
a second position adjustment module for adjusting the position of the airship so that more interior users are covered;
the position updating module is used for updating the airship position set and the uncovered user set;
the central processing module is used for sending instructions to other modules to complete related actions;
the deployment height determining module, the user classifying module, the judging module, the edge user searching module, the first position adjusting module, the second position adjusting module and the position updating module are all electrically connected with the central processing module.
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