CN114980139A - Capacity coverage enhancement method for air-ground wireless network access and return integrated system - Google Patents

Capacity coverage enhancement method for air-ground wireless network access and return integrated system Download PDF

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CN114980139A
CN114980139A CN202210572892.7A CN202210572892A CN114980139A CN 114980139 A CN114980139 A CN 114980139A CN 202210572892 A CN202210572892 A CN 202210572892A CN 114980139 A CN114980139 A CN 114980139A
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base station
ground
user
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terrestrial
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刘俊宇
蒋蓉蓉
盛敏
苏郁
李建东
史琰
张亚倩
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Xidian University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/18—Network planning tools
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/309—Measuring or estimating channel quality parameters
    • H04B17/336—Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/391—Modelling the propagation channel
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H04W16/26—Cell enhancers or enhancement, e.g. for tunnels, building shadow
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/02—Arrangements for optimising operational condition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
    • H04W64/003—Locating users or terminals or network equipment for network management purposes, e.g. mobility management locating network equipment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0473—Wireless resource allocation based on the type of the allocated resource the resource being transmission power
    • 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

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Abstract

The invention discloses a capacity coverage enhancement method of an air-ground wireless network access backhaul integrated system, which relates to the technical field of wireless communication and specifically comprises the following steps of establishing the air-ground wireless network access backhaul integrated system; the ground user initiates a request for establishing connection, the ground base station instructs the ground user to measure the signal of the base station, and the ground user reports the measured signal to the ground base station; the ground base station calculates the SINR from the ground user to a specific base station, compares the SINRs to obtain a maximum SINR link, and associates the ground user with the base station of the maximum SINR link; calculating downlink transmitting power of an air base station and a ground base station; and the ground base station calculates the optimal deployment position of the aerial base station by utilizing a particle swarm algorithm according to the channel information. The invention jointly optimizes the ground user association, the base station transmitting power and the aerial base station deployment, and increases the capacity coverage of the system.

Description

Capacity coverage enhancement method for air-ground wireless network access and return integrated system
Technical Field
The invention relates to the technical field of wireless communication, in particular to a capacity coverage enhancement method for an air-ground wireless network access return integrated system.
Background
In the air-ground wireless network scene, the air base station is matched with the ground wireless communication network, and due to the mobility, flexible deployment and low cost of the air base station, the capacity coverage performance of the ground wireless network can be effectively enhanced. Compared with the traditional ground base station, the air base station has the advantages that the air base station can flexibly and dynamically adjust the position of the air base station in three dimensions to meet the ground communication requirement, can avoid obstacles and increase the possibility of establishing a line-of-sight communication link with a ground user, thereby providing a large-capacity connection for the system and enhancing the capacity coverage of the system. Considering the use of an access backhaul integrated network architecture in this scenario, generally, the access backhaul integrated architecture implies a tight interconnection between access and backhaul links, where a ground base station provides access and backhaul connections for a ground user and an air base station, respectively, using the same infrastructure and radio channel resources, however, mutual interference between the access link and backhaul link and limitation of backhaul capacity become major challenges for establishing a communication link in an air-to-ground wireless network access backhaul integrated system.
Meanwhile, the existing ground wireless network coverage method cannot be flexibly deployed, and the ground base station is not supplied enough due to the increasing capacity demand of people, however, the cost for expanding a new ground base station is too high, a large amount of ground resources are occupied, and the aerial base station can flexibly perform network coverage on ground users according to the distribution state of the ground users. The aerial base station is utilized, on the basis of a ground wireless network, the aerial base station extends from a plane to a solid, a layer of wireless access network based on the aerial base station is superposed, network access and communication service are provided for ground users, the problem that ground communication cannot be flexibly covered is solved, and meanwhile the coverage capacity of the system is increased.
Recently, the use of access backhaul integration technology has become a solution to reduce the cost of cellular network deployment, and in this regard, the third generation partnership project introduced access backhaul integration network architecture to allow flexible deployment of the next generation cellular networks. In the article "Bandwidth allocation and downlink analysis in Millimeter Wave Integrated Access and background for 5G", the authors developed an analysis framework for cellular networks supporting an Access Backhaul Integrated network architecture, which can accurately describe the downlink rate coverage probability. In the article "Joint Load Balancing and interference mitigation in 5G Heterogeneous Networks", the authors study the problem of Joint user association and interference management in Heterogeneous Networks, wherein assume that a large number of mimo macro cell base stations are equipped with a large number of antennas covering wireless self-backhaul small cells, and describe the Joint Load Balancing and interference mitigation problem as a network utility maximization problem under wireless backhaul constraints. The access backhaul integrated network architecture can achieve flexible and fast deployment of the next generation cellular network, however, the mutual interference between the access and backhaul links, the small inter-site distance, and the spatial dynamics of user distribution pose a significant challenge to the practical deployment of the access backhaul integrated network. These problems are more effectively solved by using air base stations, which allow to dynamically reconfigure the network architecture according to the coverage and capacity requirements, unlike the basic idea of densely deploying small base stations to approach edge users, since they provide access services to terrestrial users, thus not only improving the coverage but also increasing the capacity of the system.
Patent document "a 5G communication system ground user association, unmanned aerial vehicle deployment and resource allocation method" applied by Chongqing post and telecommunications university, application number: 202110572618.5, application publication number: CN 113285777 a, although this method considers the design of backhaul links of air base stations, it does not consider the constraint condition that backhaul of air base stations is limited, so there is a certain limitation in the actual communication network system design. Patent document "communication method based on cellular communication system assisted by unmanned aerial vehicle" applied by Nanjing post and telecommunications university, application number: 201911058134.8, application publication number: CN 110958616 a, determining the optimal flying height of the air base station by the information of the existing ground base station of the cellular communication system, and deploying the air base station to improve the communication quality of the cellular communication system. In the method, backhaul constraints of the air base stations are not considered, and although the coverage rate of the system is improved, the coverage capacity of the system is not improved significantly.
Based on the above, a capacity coverage enhancement method for an air-ground wireless network access backhaul integrated system is provided to solve the problem of high dynamic deployment of the air base station and the problem of system capacity coverage.
Disclosure of Invention
The invention aims to: aiming at the defects of the prior art, an air-ground wireless network access return integrated system is designed, the ground user association, the base station transmitting power and the air base station deployment are jointly optimized, the problem that flexible coverage cannot be realized in the prior art is solved, and the capacity coverage of the system is increased.
The technical scheme adopted by the invention is as follows:
the invention relates to a capacity coverage enhancement method for an air-ground wireless network access return integrated system, which comprises the following steps:
step 1: establishing an air-ground wireless network access backhaul integrated system, wherein the air-ground wireless network access backhaul integrated system comprises a ground base station, an air base station and ground users, and the positions of the ground users and the air base station are randomly distributed in a designated range;
step 2: the ground user stays in a ground base station coverage area and keeps control surface connection with the ground base station, the ground user initiates a connection establishment request, the ground base station instructs the ground user to measure signals of the base station, and the ground user reports the measured signal measurement result to the ground base station;
and step 3: the ground base station calculates the SINR from the ground user to a specific base station, compares the SINR of each link to obtain the maximum SINR link, and the ground user is associated with the base station with the maximum SINR link, namely the ground user is associated with the air base station or the ground user is associated with the ground base station;
and 4, step 4: calculating downlink transmitting power of an air base station and a ground base station through a convex optimization tool CVX;
and 5: the ground base station calculates the optimal deployment position of the aerial base station by using a particle swarm algorithm according to the channel information;
step 6: updating downlink power allocation of the air base station and the ground base station according to the fixed ground user association;
and 7: and the air base station and the ground user perform user plane data transmission or the ground base station and the ground user perform user plane s data transmission.
Further, in the air-ground wireless network access backhaul integrated system of step 1,
the ground base station is loaded with a base station module and a central control processor, is responsible for data collection and processing of the whole scene, is used as a node for core network communication, performs data transmission with a core network through a large-scale optical fiber, is simultaneously loaded with a multi-antenna system, is responsible for distributing core network data to subordinate air base stations or ground users, and collects and summarizes mobile data of the air base stations and the ground users; the central control processor grasps all channel information and can execute a resource allocation strategy;
the ground base stations and air base stations provide access links to ground users, any ground user being able to communicate with either the ground base station or the air base station.
Further, the specific step of SINR from the ground user to the specific base station in step 3 is:
step 31, modeling a ground user association variable;
specifically, M air base stations and J ground users exist in the system, and the sets of air base stations and ground users are respectively represented as U ═ U 1 ,U 2 ,...,U M And G ═ G 1 ,G 2 ,...,G J }，
The set of base stations is denoted as B ═ U { TBS } - { B ═ U { (TBS } - } ═ B ═ U { (TBS } - } { (TBS } { (B } {) 0 ,B 1 ,...,B I Index 0 in B represents the only terrestrial base station in the system,
the association between the ground base station, the air base station and the ground user is denoted as a ═ a i,j I ∈ B, j ∈ G }, where a i,j 1 represents G j From B i Service, otherwise a i,j ＝0；
Step 32, modeling each channel model, and calculating the SINR received by the ground user;
from terrestrial base station to terrestrial user G i The MISO downlink power gain vector of (a) is:
Figure BDA0003660964760000031
in the formula, ρ t2t Representing the distance d from the ground base station to the ground user 0 Power gain of reference channel at 1m, α t2t Denotes the corresponding path loss exponent, g i CN (0, I) follows Rayleigh fading, | TBS-G i I is from ground base station to ground user G i The distance of (d);
is provided with h b.i And h i,j Respectively representing the signals from terrestrial base station to U i And an aerial base station U i To the ground user G j Channel gain of (p) u2t Indicating the distance d from the airborne base station to the ground 0 Power gain of reference channel at 1m, α u2t Which represents the corresponding path loss exponent of the signal,
ground base station to U i The channel gain formula is:
Figure BDA0003660964760000032
from aerial base station U i To ground user G j The channel gain formula is:
Figure BDA0003660964760000041
from aerial base station U i To an airborne base station U j The channel gain formula of (a) is:
Figure BDA0003660964760000042
wherein CSI represents a self-interference cancellation factor, ρ, between an access link and a backhaul link u2u Indicating the distance d to the sky 0 Power gain of reference channel at 1m, α u2u Representing the corresponding path loss exponent;
the access link and the backhaul link use the same spectrum resources to improve spectrum utilization efficiency. Thus, there is interference between different links. Linear zero-forcing beamforming (LZFBF) for multi-user MISO transmission is used to mitigate inter-cell interference between terrestrial users served by an aerial base station and a terrestrial base station. G TBS Represents the set of terrestrial users served by the terrestrial base station,
Figure BDA0003660964760000043
wherein N is K The ZF precoding vector in the ground base station is denoted by V |, K |, and
Figure BDA0003660964760000044
wherein
Figure BDA0003660964760000045
Is a full rank channel matrix between ground base stations, air base stations and ground users served by the ground base stations, using equal transmit power normalization to K due to high sum rate gain i Normalizing the ZF precoding vector; in particular, the present invention relates to a method for producing,
Figure BDA0003660964760000046
wherein [ V ]] i Is the ith column of the V,
thus, the formula
Figure BDA0003660964760000047
If it does, it indicates that K is if i ≠ j i Will not interfere with K j ，
K i The received signal at (a) is given by the following equation:
Figure BDA0003660964760000048
first term in the above formula
Figure BDA0003660964760000049
Is a transmitted signal, the second term
Figure BDA00036609647600000410
And item III
Figure BDA00036609647600000411
Are each K i Interference with other receivers in an airborne base station, p b,i And x b,i Representing from terrestrial base station to K i And the transmitted data symbols, similarly, p j,k And x j,k Represents a slave U j To G k The power allocation of (a) and the data symbols transmitted,
Figure BDA00036609647600000412
and n i ～CN(0,σ 2 ) Respectively represent and U j Associated set of terrestrial users and received zero mean Additive White Gaussian Noise (AWGN), variance σ 2 At K i Where the second term in the above equation equals zero;
therefore, K i The signal to interference plus noise ratio SINR is given by:
Figure BDA0003660964760000051
the ground base station and the air base station adopt NOMA mode in the downlink, the ground user adopts SIC technology to reduce A i Mutual interference of users, in the downlink of the NOMA system, the SIC decoder decodes the terrestrial user signals in order of increasing terrestrial user channel power gain, which is subtracted from the superimposed signal when the information of the terrestrial user is successfully decoded, and the terrestrial user is not interfered by the subtracted signal but by the remaining terrestrial user signals, so that in a typical NOMA downlink, if h is the sum of the received signals, the interference of the terrestrial user signals is reduced i,j <h i,k ,j,k∈A i Then A is i,j Only receive from A i,k Interference of (A) i The terrestrial users in (1) being numbered in ascending order according to channel strength, i.e.
Figure BDA0003660964760000052
If j is>k, then by applying SIC, A i,j Can decode and subtract A i,k A signal of i,j The received signal at (a) is given by the following equation:
Figure BDA0003660964760000053
first term in the above formula
Figure BDA0003660964760000054
Is a transmission signal, the second term
Figure BDA0003660964760000055
Is A i Interference of other terrestrial users, third term in the above equation
Figure BDA0003660964760000056
And item four
Figure BDA0003660964760000057
Interference from other aerial and terrestrial base stations, respectively, A i,j The received SINR is given by
Figure BDA0003660964760000058
In the above formula, the first and second carbon atoms are,
Figure BDA0003660964760000059
is other aerial base station pair G j The interference of (a) with the other,
Figure BDA00036609647600000510
is a ground base station pair G j Interference of (2);
and step 33, comparing the SINRs of the links to obtain the maximum SINR link, and associating the ground user with the base station of the maximum SINR link.
Further, by A i,j The received SINR formula is used for further obtaining the reachable rate R of the ground user and the air base station i ＝log 2 (1+γ i ),i∈G∪U。
Further, the specific step of the base station associated with the maximum SINR link by the ground user in step 3 is: the ground base station informs the base station with the largest SINR link to establish connection preparation, and after confirming the preparation completion to the ground base station, the base station sends access information to the ground base station; the ground user initiates an access request to the base station of the maximum SINR link and establishes connection with the base station, and the ground base station sends an establishment response to the ground user and forwards the access information to the ground user.
Further, the specific steps of step 5 are:
step 51: initializing the particle swarm velocity and the particle swarm position, the inertia constant, the acceleration constant and the maximum iteration number I of the particle swarm algorithm at the ground base station side max ；
Step 52: calculate the fitness value Θ (W, p) for each particle BH ) Then evaluating theta at the current position of each particle, comparing the theta with the optimal local fitness and the global fitness of the particle swarm, and updating the position of the optimal local target and the position of the global target;
step 53: updating the speed and position of the particle;
step (ii) of54: performing iteration until maximum iteration number I max To solve the optimal deployment position of the aerial base station.
Further, in step 52,
the maximum flying speed of the particles is
Figure BDA0003660964760000061
Where N is the number of particle clusters and M M is the number of airborne base stations, then the velocity matrix for the N particles can be expressed in the kth iteration as
Figure BDA0003660964760000062
Similarly, both the matrix of current positions and the position of the best local target may be used
Figure BDA0003660964760000063
And
Figure BDA0003660964760000064
thus, the location of the best local target of the N particles can be given by the following formula:
Figure BDA0003660964760000065
wherein the position of the optimal local target of the particle is defined in the previous r iterations;
then let
Figure BDA0003660964760000066
Represents the location of the global target and is given by:
Figure BDA0003660964760000067
wherein
Figure BDA0003660964760000068
Is X (k) Is a weighted fitness function, evaluated at the current location of each particleEstimate Θ and compare it to the best local and global fitness of the population of particles, and then use it separately
Figure BDA0003660964760000069
And
Figure BDA00036609647600000610
updating
Figure BDA00036609647600000611
And
Figure BDA00036609647600000612
a value of (d);
thus, the moving speed of the particle at the (k +1) th iteration may be updated as:
Figure BDA0003660964760000071
where w is expressed as an inertia constant for the exploration of the adaptive control optimization process, c 1 And c 2 Indicating the acceleration constant, in particular when c 1 When 0, the search is set to the highest level, when c 2 When 0, the search is also set to the highest level, and finally, R 1 ，
Figure BDA0003660964760000072
Is [0,1 ]]Indicates a hadamard product, and thus, the position of each particle in the (k +1) iteration can be updated according to its position in the k-th iteration and the motion velocity of the (k +1) iteration, where the position of the particle is updated to be:
X (k+1) ＝X (k) +V (k+1) 。
further, in each iteration, the difference between the received and target SINR is calculated as
Figure BDA0003660964760000073
Then consider that the received SINR at the access and direct links is below ε u Ground user set
Figure BDA0003660964760000074
Wherein | upsilon u | represents upsilon u Is equal to, the set of airborne base stations receiving SINR on the backhaul link is below epsilon d Is defined as
Figure BDA0003660964760000075
In the formula
Figure BDA0003660964760000076
Thus, the weighted fitness function may consist of an objective function and a nonlinear inequality constraint, given by:
Figure BDA0003660964760000077
wherein e 1 And e 2 And the penalty parameters are represented and are defined respectively based on the target QoS received by the ground user and the air base station.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. the invention relates to a capacity coverage enhancement method of an air-ground wireless network access return integrated system, which establishes the air-ground wireless network access return integrated system, wherein the system comprises a ground base station and a plurality of air base stations, the ground base station is provided with a large-capacity wired return to a core network, the air base station uses the return of the ground base station, the ground base station uses the same frequency spectrum or wireless channel to provide service for ground users in the coverage range of the ground base station and provides return connection with the air base stations, the air base stations are jointly deployed to provide communication service for the ground users in an area, and the association between the ground users and the base stations, the downlink power distribution of the base stations and the position deployment of the air base stations are jointly optimized by taking the maximization of the ground users and the speed in the system as a target so as to enhance the coverage capacity of the system.
2. The invention relates to a capacity coverage enhancement method for an air-ground wireless network access return integrated system.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments are briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts, and the proportional relationship of each component in the drawings in the present specification does not represent the proportional relationship in the actual material selection design, and is only a schematic diagram of the structure or the position, in which:
FIG. 1 is a system model diagram;
FIG. 2 is a flow chart of information interaction between terminals of the system;
FIG. 3 is a flow chart of a particle group algorithm implementation in the system;
FIG. 4 is a line graph of capacity coverage performance as a function of the number of ground users when the ground users are randomly distributed;
FIG. 5 is a line graph showing the variation of capacity coverage performance with the number of ground users when ground user clusters are distributed;
FIG. 6 is a line graph showing the capacity coverage performance varying with the number of ground base station antennas when the ground users are randomly distributed;
fig. 7 is a line graph showing the capacity coverage performance varying with the number of antennas of the ground base station when the ground user clusters are distributed.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
It should be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
The present invention will be described in detail with reference to the accompanying drawings.
The specific embodiment is as follows:
the invention relates to a capacity coverage enhancement method for an air-ground wireless network access return integrated system, which specifically comprises the following steps:
step 1: establishing an air-ground wireless network access backhaul integrated system, wherein the air-ground wireless network access backhaul integrated system comprises a ground base station, an air base station and ground users, and the positions of the ground users and the air base station are randomly distributed in a designated range;
as shown in fig. 1, the ground base station is responsible for collecting and processing data of the whole scene model, and serves as a node communicating with the core network, and performs data transmission with the core network through a large-scale optical fiber, and meanwhile, carries a multi-antenna system, and is responsible for distributing core network data to a subordinate air base station or a ground user, and collecting and summarizing mobile data of the air base station and the ground user.
In the air-ground wireless access return integrated network, J ground users are randomly distributed, an air base station carries a micro base station system and is responsible for collecting and forwarding ground user data, in the range of multiple base stations consisting of the air base stations, multiple air base stations carry out coordinated multipoint transmission, and the base stations carry out joint processing through shared data so as to eliminate co-channel interference and improve the spectrum efficiency.
Assuming that the ground base station is equipped with a number N of array antennas, all air base stations and ground users are equipped with a single antenna. Any terrestrial user has a communication condition with the base station. The central control processor grasps all channel information and may implement a resource allocation strategy. In addition, all the air base stations in the system can cooperate with each other through data sharing by a backhaul link with limited capacity.
The connection establishment procedure between the ground user and the ground base station and the air base station is shown in fig. 2, and steps 2 to 7 are the connection establishment procedure between the ground user and the ground base station and the air base station.
Step 2: the ground user stays in a ground base station coverage area and keeps control surface connection with the ground base station, the ground user initiates a connection establishment request, the ground base station instructs the ground user to measure signals of the base station, and the ground user reports the measured signal measurement result to the ground base station;
the system assumes that all airborne base stations share the same frequency band for communication during successive periods of time duration, while the base stations use NOMA to provide more access opportunities for each terrestrial user. In the NOMA system, multi-terrestrial user superposition coding is implemented in the transmitter, and SIC is used in the receiver, so that the receiver can recover the required information from the multiplexed signal.
The core idea of the NOMA is to use superposition coding at the transmitting end and SIC at the receiving end, thereby realizing multiple access in the power domain through different power level levels on the same time-frequency resource block. At a sending end, different users on the same subchannel are sent by adopting a power multiplexing technology, and the signal power of different users is distributed according to a related algorithm, so that the signal power of each user reaching a receiving end is different. And the SIC receiver eliminates interference according to the signal power of different users in a certain sequence, realizes correct demodulation and achieves the purpose of distinguishing the users at the same time.
And step 3: the ground base station calculates the SINR from the ground user to a specific base station, compares the SINRs to obtain a maximum SINR link, associates the ground user with the base station with the maximum SINR link, associates the ground user with the air base station or associates the ground user with the ground base station, informs the base station with the maximum SINR link to establish connection preparation, and sends access information to the ground base station after the base station confirms that the preparation is completed to the ground base station; the ground user initiates an access request to the base station with the maximum SINR link and establishes connection with the base station, and the ground base station sends an establishment response to the ground user and forwards the access information to the ground user;
initially, the ground user resides in the ground base station coverage area, and maintains control plane connection with the ground base station, in the system, the ground base station assumes the function of the wireless network control plane, and the air base station receives the wireless resource management of the ground base station and assumes the user plane data processing. When the ground user initiates a connection establishment request, the ground base station indicates the user to perform signal measurement on a specific base station through RRC signaling. The user reports the detected signal measurement result to the ground base station, the ground base station informs the air base station to complete the connection preparation, and the air base station confirms the completion of the preparation to the ground base station and sends the access information to the ground base station. The ground base station sends a setup response to the user and forwards the access information to the user.
There are multiple ground users, each of which can be associated with only one air base station or ground base station, and each of which can be associated with multiple ground users.
The specific steps of the SINR from the ground user to the specific base station in step 3 are as follows:
step 31, modeling a ground user association variable;
specifically, M M air base stations and J J ground users exist in the system, and the system is used for transmitting airThe set of base stations and terrestrial users are denoted U ═ U, respectively 1 ,U 2 ,...,U M And G ═ G 1 ,G 2 ,...,G J }，
The set of base stations is denoted as B ═ U { TBS } - { B ═ U { (TBS } - } ═ B ═ U { (TBS } - } { (TBS } { (B } {) 0 ,B 1 ,...,B I Index 0 in B represents the only terrestrial base station in the system,
the association between the ground base station, the air base station and the ground user is denoted as a ═ a i,j I ∈ B, j ∈ G }, where a i,j 1 represents G j From B i Service, otherwise a i,j ＝0；
Step 32, modeling each channel model, and calculating the SINR received by the ground user;
from terrestrial base station to terrestrial user G i The MISO downlink power gain vector of (a) is:
Figure BDA0003660964760000101
in the formula, ρ t2t Representing the distance d from the ground base station to the ground user 0 Power gain of reference channel at 1m, α t2t Denotes the corresponding path loss exponent, g i CN (0, I) follows Rayleigh fading, | TBS-G i I is from ground base station to ground user G i The distance of (d);
is provided with h b.i And h i,j Respectively representing the signals from terrestrial base station to U i And an aerial base station U i To the ground user G j Channel gain of (p) u2t Indicating the distance d from the airborne base station to the ground 0 Power gain of reference channel at 1m, α u2t Which represents the corresponding path loss exponent for the signal,
ground base station to U i The channel gain formula is:
Figure BDA0003660964760000102
from aerial base station U i To ground user G j The channel gain formula is:
Figure BDA0003660964760000103
from aerial base station U i To an airborne base station U j The channel gain formula of (a) is:
Figure BDA0003660964760000111
wherein CSI represents a self-interference cancellation factor, ρ, between an access link and a backhaul link u2u Indicating the distance d to the sky 0 Power gain of reference channel at 1m, α u2u Representing the corresponding path loss exponent;
the access link and the backhaul link use the same spectrum resources to improve spectrum utilization efficiency. Thus, there is interference between different links. Linear zero-forcing beamforming (LZFBF) for multi-user MISO transmission is used to mitigate inter-cell interference between air base stations and ground users served by ground base stations. Let G TBS Represents the set of terrestrial users served by the terrestrial base station,
Figure BDA0003660964760000112
wherein N is K K |. The ZF precoding vector in the ground base station is denoted by V
Figure BDA0003660964760000113
Wherein
Figure BDA0003660964760000114
Is a full rank channel matrix between ground base stations, air base stations and ground users served by the ground base stations. Using Equal Transmit Power (ETP) normalization for K due to high sum Rate gain i The precoding vectors of (a) are normalized. In particular, v i By
Figure BDA0003660964760000115
Wherein [ V ]] i Is the ith column of V. Thus, the formula
Figure BDA0003660964760000116
This is true. It indicates that K is if i ≠ j i Will not interfere with K j ，
K i The received signal at (a) is given by the following equation:
Figure BDA0003660964760000117
first term in the above formula
Figure BDA0003660964760000118
Is a transmitted signal, the second term
Figure BDA0003660964760000119
And item III
Figure BDA00036609647600001110
Are each K i Interference with other receivers in an airborne base station, p b,i And x b,i Representing from terrestrial base station to K i And the transmitted data symbols, similarly, p j,k And x j,k Represents a slave U j To G k The power allocation of (a) and the data symbols transmitted,
Figure BDA00036609647600001111
and n i ～CN(0,σ 2 ) Respectively represent and U j Associated ground user set and received zero mean Additive White Gaussian Noise (AWGN), variance σ 2 At K i Where the second term in the above equation equals zero;
therefore, K i The signal to interference plus noise ratio SINR is given by:
Figure BDA0003660964760000121
the ground base station and the air base station adopt NOMA mode in the down link, the ground user adopts SIC technology to reduce A i Mutual interference of users, SIC decoder according to ground in NOMA system downlinkThe ascending order of the surface user channel power gain sequentially decodes the surface user signal, which is subtracted from the superimposed signal when the surface user information is successfully decoded, the surface user is not interfered by the subtracted signal, but by the remaining surface user signal, so that in a typical NOMA downlink, if h, the signal is transmitted in the same order as the terrestrial user signal, and the terrestrial user signal is transmitted in the same order as the terrestrial user signal i,j <h i,k ,j,k∈A i Then A is i,j Only receive from A i,k Interference of (A) i The terrestrial users in (1) being numbered in ascending order according to channel strength, i.e.
Figure BDA0003660964760000122
If j is>k, then by applying SIC, A i,j Can decode and subtract A i,k A signal of i,j The received signal at (a) is given by the following equation:
Figure BDA0003660964760000123
first item in the above formula
Figure BDA0003660964760000124
Is a transmission signal, the second term
Figure BDA0003660964760000125
Is A i Interference of other terrestrial users, third term in the above equation
Figure BDA0003660964760000126
And item four
Figure BDA0003660964760000127
Interference from other aerial and terrestrial base stations, respectively, A i,j The received SINR is given by
Figure BDA0003660964760000128
In the above formula, the first and second carbon atoms are,
Figure BDA0003660964760000129
is other aerial base station pair G j The interference of (a) with the other,
Figure BDA00036609647600001210
is a ground base station pair G j Interference of (2); by A i,j The received SINR formula is used for further obtaining the reachable rate R of the ground user and the air base station i ＝log 2 (1+γ i ),i∈G∪U。
And step 33, comparing the SINRs of the links to obtain the maximum SINR link, and associating the ground user with the base station of the maximum SINR link.
Calculating SINR from all ground users to the ground base station, calculating SINR from the ground users to the air base station, comparing SINR in downlink by using NOMA mode between the ground base station and the air base station to obtain the maximum SINR link, and associating the ground users to the base station. Next, downlink access and backhaul power allocations are also initialized with equal power allocations based on the number of terrestrial users associated with each base station, wherein
Figure BDA0003660964760000131
And 4, step 4: calculating downlink transmitting power of an air base station and a ground base station through a convex optimization tool CVX;
and 5: the ground base station calculates the optimal deployment position of the aerial base station by using a particle swarm algorithm according to the channel information, as shown in fig. 3;
specifically, step 51: on the ground base station side, initializing the particle group speed and the particle group position, the inertia constant, the acceleration constant and the maximum iteration number I of the particle group algorithm max ；
Step 52: calculate the fitness value Θ (W, p) for each particle BH ) Then evaluating theta at the current position of each particle, comparing the theta with the optimal local fitness and the global fitness of the particle swarm, and updating the position of the optimal local target and the position of the global target;
in a step 52, the process is repeated,
the maximum flying speed of the particles is
Figure BDA0003660964760000132
Where N is the number of particle groups and M is the number of airborne base stations, then the velocity matrix for the N particles may be represented in the kth iteration as
Figure BDA0003660964760000133
Similarly, both the matrix of current positions and the position of the best local target may be used
Figure BDA0003660964760000134
And
Figure BDA0003660964760000135
thus, the location of the best local target of the N particles can be given by the following formula:
Figure BDA0003660964760000136
wherein the position of the optimal local target for the particle is defined in the previous r iterations;
then let
Figure BDA0003660964760000137
Represents the location of the global target and is given by:
Figure BDA0003660964760000138
wherein
Figure BDA0003660964760000139
Is X (k) Is a weighted fitness function, estimates Θ at the current position of each particle and compares it to the best local and global fitness of the particle population, and then uses it separately
Figure BDA00036609647600001310
And
Figure BDA00036609647600001311
updating
Figure BDA00036609647600001312
And
Figure BDA00036609647600001313
a value of (d);
thus, the moving speed of the particle at the (k +1) th iteration may be updated as:
Figure BDA00036609647600001314
where w is expressed as an inertia constant for the exploration of the adaptive control optimization process, c 1 And c 2 Indicating the acceleration constant, in particular when c 1 When 0, the search is set to the highest level, when c 2 When 0, the search is also set to the highest level, and finally, R 1 ，
Figure BDA0003660964760000141
Is [0,1 ]]Indicates a hadamard product, and thus, the position of each particle in the (k +1) iteration can be updated according to its position in the k-th iteration and the motion velocity of the (k +1) iteration, where the position of the particle is updated to be:
X (k+1) ＝X (k) +V (k+1)
in each iteration, the difference between the received and target SINR is calculated as
Figure BDA0003660964760000142
Then consider that the received SINR at the access and direct links is below ε u Ground user set
Figure BDA0003660964760000143
Wherein | upsilon u | represents upsilon u Of (2) aThe same is true for the air base station group receiving SINR on the backhaul link below ε d Is defined as
Figure BDA0003660964760000144
In the formula
Figure BDA0003660964760000145
Thus, the weighted fitness function may consist of an objective function and a nonlinear inequality constraint, given by:
Figure BDA0003660964760000146
wherein e 1 And e 2 Representing penalty parameters, defined based on target QoS received by ground users and air base stations respectively
Step 53: updating the speed and position of the particle;
step 54: performing iteration until maximum iteration number I max To solve the optimal deployment position of the aerial base station.
Step 6: updating downlink power allocation of the air base station and the ground base station according to the fixed ground user association;
and 7: the air base station and the ground user perform user plane data transmission or the ground base station and the ground user perform user plane transmission.
According to the invention, the deployment position of the aerial base station can be found through a particle swarm algorithm, and the downlink power distribution of the base station is updated according to the fixed ground user association. In the particle swarm algorithm, a particle swarm is moved along a multidimensional search space with a probability mechanism to find a set of feasible solutions, while taking into account the moving speed of the current iteration and the distance between the current position, the position of the optimal local target and the position of the global target.
The invention mainly reflects the enhancement of the coverage capacity on the joint optimization of the association of the ground user and the base station, the downlink power distribution of the base station and the position deployment of the aerial base station, and the joint optimization problem can be defined as:
Figure BDA0003660964760000151
s.t.C1:
Figure BDA0003660964760000152
C2:
Figure BDA0003660964760000153
C3:
Figure BDA0003660964760000154
C4:
Figure BDA0003660964760000155
C5:
Figure BDA0003660964760000156
C6:
Figure BDA0003660964760000157
where eta is a minimum SINR threshold predefined for terrestrial users,
Figure BDA0003660964760000158
and
Figure BDA0003660964760000159
upper limit, set [ w ] of the transmit power of the ground base station and the air base station, respectively min ,w max ]Representing the area where the aerial base station is allowed to be deployed. It can be observed that C1 guarantees QoS for terrestrial users; c2 indicates that the access rate should not be higher than the corresponding backhaul rate; c3 indicates that each ground user can only be served by one air base station or ground base station; c4 and C5 show that the power of the ground base station and the aerial base station can not exceed the maximum transmitting power, C6 defines the flight area of the aerial base station, and the joint problem is NP difficult and has integer variableThere are also continuous variables.
When the location of the airborne base station is deployed given, the ground user association and power allocation sub-PA problem can be written as:
PA:
Figure BDA00036609647600001510
Figure BDA00036609647600001511
Figure BDA00036609647600001512
Figure BDA00036609647600001513
Figure BDA00036609647600001514
Figure BDA00036609647600001515
the base station power allocation problem can be solved at each base station side by a convex optimization tool CVX.
In the PB, mainly finding out the deployment position of an aerial base station, and correspondingly updating the downlink power allocation of the base station under the condition of giving association of a fixed ground user base station; the sub-problem PB is given by:
PB:
Figure BDA0003660964760000161
Figure BDA0003660964760000162
Figure BDA0003660964760000163
Figure BDA0003660964760000164
Figure BDA0003660964760000165
Figure BDA0003660964760000166
the optimization method provided by the invention is compared and analyzed with other methods, and the specific process is as follows:
consider another spatial configuration mode of an airborne base station, in which case the airborne base station is configured as a single DAA, serving terrestrial users spatially distributed in a single hotspot. Unlike distributed air base stations, air base stations in DAA mode do not interfere with each other, but instead consist of a single antenna array to benefit from the potential advantages of DAA. The DAA configuration mode allows the array to be configured as desired. In particular, the design parameters of the DAA are adjusted according to the spatial distribution of the terrestrial users to maximize the overall and rate gains.
The parameters in the specific implementation of the algorithm are set as in table 1,
setting parameters Particle swarm optimization deployment UAVs DAA deployment
Ground base station access link MISO SISO
Ground base station backhaul link MIMO MIMO
Number of base stations in the air 4 4
Number of aerial base station antennas 1 1
Air base station access link NOMA MIMO
Number of antennas of ground base station 32 32
Number of users 25 25
Maximum power of ground base station 46dBm 46dBm
Maximum power of air base station 36dBm 36dBm
Minimum signal-to-noise ratioThreshold value 3dB 3dB
Simulation area 3000×3000m 2 3000×3000m 2
TABLE 1 parameter settings
The present invention jointly optimizes subscriber base station association, downlink power allocation for ground and air base stations, and air base station location deployment, and therefore, this problem is translated into a network and rate maximization problem that is limited by the receive SINR threshold at each ground subscriber, and takes into account the transmit power limitations at each base station. Since the sum-rate maximization problem is non-convex and NP-hard, it is not possible to use a polynomial time algorithm to find the optimal solution of the problem, and a global optimization method can be used to find the global optimal solution.
As shown in fig. 4, 5, 6, and 7, the simulation result is a graph of the system capacity coverage change with an increase in the number of terrestrial users in the system when the terrestrial users are randomly distributed as shown in fig. 4, where the number of antennas of the terrestrial base station is 32, the number of terrestrial users is changed only by changing the number of terrestrial users in steps of 25, and the change range is 25 to 125, and the influence of the change in the number of terrestrial users in the system on the system capacity coverage performance is obtained. With the increase of the number of ground users in the system, the system capacity coverage, namely the system users and the rate, is also increased, and compared with the air base station deployment mode according to the DAA deployment mode, the air base station deployment mode obtained by solving through the proposed algorithm has the capacity coverage performance improved by 72.5% when the number of ground users is 100, and improved by 124.9% when the air base station is not provided. Fig. 5 is a line graph of system capacity coverage change with an increase in the number of ground users in the system when the ground user clusters are distributed, where the number of antennas of the ground base station is 32, only the number of ground users is changed, and the change range is 25 to 125 with 25 steps, so as to obtain the influence of the change in the number of ground users in the system on the system capacity coverage performance. With the increase of the number of ground users in the system, the system capacity coverage, namely the system users and the system rate, are also increased, and compared with the air base station deployment mode according to the DAA deployment mode, the air base station deployment mode obtained by solving through the proposed algorithm has the capacity coverage performance improved by 11.2% when the number of ground users is 100, and improved by 222.2% when no air base station is provided.
Fig. 6 is a line graph showing the number of antennas of the terrestrial base station as 8, 16, 32, 64, 128 in sequence and the number of terrestrial users as 50 in the system as the number of antennas of the terrestrial base station changes according to the change of terrestrial users and the change of rate when the users are randomly distributed. As the number of terrestrial base station antennas increases, the system capacity coverage also increases. Moreover, compared with the aerial base station deployment mode according to DAA, the aerial base station deployment mode obtained by solving through the proposed algorithm has the advantages that when the number of the ground base station antennas is 32, the capacity coverage performance is improved by 83.5%, and compared with the capacity coverage performance of an air-free base station, the capacity coverage performance is improved by 189.8%. Fig. 7 is a line graph showing the number of antennas of the terrestrial base station as 8, 16, 32, 64, 128 in sequence and the number of terrestrial users as 50 in the system as the number of antennas of the terrestrial base station changes according to the change of terrestrial users and the change of speed when the user clusters are distributed. As the number of terrestrial base station antennas increases, system capacity coverage also increases. Moreover, compared with the aerial base station deployment mode obtained by solving through the proposed algorithm according to DAA, when the number of the ground base station antennas is 32, the capacity coverage performance is improved by 11.7%, and compared with the capacity coverage performance of the non-aerial base station, the capacity coverage performance is improved by 322.8%. Because the aerial base station mode deployed according to the proposed algorithm can realize the optimal deployment of the aerial base station according to the information of each channel in the system. It follows that the proposed algorithm can enhance the coverage capacity of the system, and thus is more beneficial to enhance the coverage capability of the system.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be made by those skilled in the art without inventive work within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the claims.

Claims (8)

1. The capacity coverage enhancement method for the air-ground wireless network access return integrated system is characterized by comprising the following steps:
step 1: establishing an air-ground wireless network access backhaul integrated system, wherein the air-ground wireless network access backhaul integrated system comprises a ground base station, an air base station and ground users, and the positions of the ground users and the air base station are randomly distributed in a designated range;
step 2: the ground user stays in a ground base station coverage area and keeps control plane connection with the ground base station, the ground user initiates a connection establishment request, the ground base station instructs the ground user to measure signals of the base station, and the ground user reports the measured signal measurement result to the ground base station;
and step 3: the ground base station calculates the SINR from the ground user to a specific base station, the SINR is compared to obtain a maximum SINR link, and the ground user is associated with the base station with the maximum SINR link, namely the ground user is associated with the air base station or the ground user is associated with the ground base station;
and 4, step 4: calculating downlink transmitting power of an air base station and a ground base station through a convex optimization tool CVX;
and 5: the ground base station calculates the optimal deployment position of the aerial base station by using a particle swarm algorithm according to the channel information;
step 6: updating downlink power allocation of the air base station and the ground base station according to the fixed ground user association;
and 7: and the air base station and the ground user perform user plane data transmission or the ground base station and the ground user perform user plane data transmission.
2. The method according to claim 1, wherein the capacity coverage enhancement method comprises: in the air-ground wireless network access backhaul integrated system of step 1,
the ground base station is loaded with a base station module and a central control processor, is responsible for data collection and processing of the whole scene, is used as a node for core network communication, performs data transmission with a core network through a large-scale optical fiber, is simultaneously loaded with a multi-antenna system, is responsible for distributing core network data to subordinate air base stations or ground users, and collects and summarizes mobile data of the air base stations and the ground users; the central control processor grasps all channel information and can execute a resource allocation strategy;
the ground base stations and air base stations provide access links to ground users, any ground user being able to communicate with either the ground base station or the air base station.
3. The method for enhancing the capacity coverage of the air-to-ground wireless network access backhaul integrated system according to claim 1, wherein the specific steps of the SINR of the ground user to the specific base station in step 3 are as follows:
step 31, modeling a ground user association variable;
specifically, M air base stations and J ground users exist in the system, and the sets of air base stations and ground users are respectively represented as U ═ U 1 ,U 2 ,...,U M And G ═ G 1 ,G 2 ,...,G J }，
The set of base stations is denoted as B ═ U { TBS } - { B ═ U { (TBS } - } ═ B ═ U { (TBS } - } { (TBS } { (B } {) 0 ,B 1 ,...,B I H, index 0 in B indicates the only terrestrial base station in the system,
the association between the ground base station, the air base station and the ground user is denoted as a ═ a i,j I ∈ B, j ∈ G }, where a i,j 1 represents G j From B i Service, otherwise a i,j ＝0；
Step 32, modeling each channel model, and calculating the SINR received by the ground user;
from terrestrial base station to terrestrial user G i The MISO downlink power gain vector of (a) is:
Figure FDA0003660964750000021
in the formula, ρ t2t Representing the distance d from the ground base station to the ground user 0 Power gain of reference channel at 1m, α t2t Denotes the corresponding path loss exponent, g i CN (0, I) follows Rayleigh fading, | TBS-G i I is from ground base station to ground user G i The distance of (d);
is provided with h b.i And h i,j Respectively representing the signals from terrestrial base station to U i And an aerial base station U i To ground user G j Channel gain of (p) u2t Indicating the distance d from the airborne base station to the ground 0 Power gain of reference channel at 1m, α u2t Which represents the corresponding path loss exponent for the signal,
ground base station to U i The channel gain formula is:
Figure FDA0003660964750000022
from aerial base station U i To ground user G j The channel gain formula is:
Figure FDA0003660964750000023
from aerial base station U i To an airborne base station U j The channel gain formula of (a) is:
Figure FDA0003660964750000024
wherein CSI represents a self-interference cancellation factor, ρ, between an access link and a backhaul link u2u Indicating the distance d to the sky 0 Power gain of reference channel at 1m, α u2u Representing the corresponding path loss exponent;
G TBS represents the set of terrestrial users served by the terrestrial base station,
Figure FDA0003660964750000025
wherein N is K ZF pre in terrestrial base station |, K |, ZF preThe code vector being denoted by V
Figure FDA0003660964750000026
Wherein
Figure FDA0003660964750000027
Is a full rank channel matrix between ground base stations, air base stations and ground users served by the ground base stations, using equal transmit power normalization to K due to high sum rate gain i Normalizing the ZF precoding vector; in particular, the present invention relates to a method for producing,
Figure FDA0003660964750000028
wherein [ V ]] i Is the ith column of V,
thus, the formula
Figure FDA0003660964750000029
If true, it indicates that K is not equal to j i Will not interfere with K j ，
K i The received signal at (a) is given by the following equation:
Figure FDA0003660964750000031
first term in the above formula
Figure FDA0003660964750000032
Is a transmission signal, the second term
Figure FDA0003660964750000033
And item III
Figure FDA0003660964750000034
Are each K i Interference with other receivers in an airborne base station, p b,i And x b,i Representing from terrestrial base station to K i And transmitted data symbols, and similarly，p j,k And x j,k Represents a slave U j To G k G k The power allocation of (a) and the data symbols transmitted,
Figure FDA0003660964750000035
and n i ～CN(0,σ 2 ) Respectively represent and U j Associated set of terrestrial users and received zero mean Additive White Gaussian Noise (AWGN), variance σ 2 At K i Where the second term in the above equation equals zero;
therefore, K i The signal to interference plus noise ratio SINR is given by:
Figure FDA0003660964750000036
the ground base station and the air base station adopt NOMA mode in the down link, the ground user adopts SIC technology to reduce A i Mutual interference of users, in the downlink of the NOMA system, the SIC decoder decodes the terrestrial user signals in order of increasing terrestrial user channel power gain, which is subtracted from the superimposed signal when the information of the terrestrial user is successfully decoded, and the terrestrial user is not interfered by the subtracted signal but by the remaining terrestrial user signals, so that in a typical NOMA downlink, if h is the sum of the received signals, the interference of the terrestrial user signals is reduced i,j <h i,k ,j,k∈A i Then A is i,j Only receive from A i,k Interference of (A) i The terrestrial users in (1) being numbered in ascending order according to channel strength, i.e.
Figure FDA0003660964750000037
If j is>k, then by applying SIC, A i,j Can decode and subtract A i,k A signal of i,j The received signal at (a) is given by the following equation:
Figure FDA0003660964750000038
first item in the above formula
Figure FDA0003660964750000041
Is a transmission signal, the second term
Figure FDA0003660964750000042
Is A i Interference of other terrestrial users, third term in the above equation
Figure FDA0003660964750000043
And item four
Figure FDA0003660964750000044
Interference from other aerial and terrestrial base stations, respectively, A i,j The received SINR is given by
Figure FDA0003660964750000045
In the above formula, the first and second carbon atoms are,
Figure FDA0003660964750000046
is other aerial base station pair G j The interference of (a) with the other,
Figure FDA0003660964750000047
is a ground base station pair G j Interference of (2);
and step 33, comparing the SINRs of the links to obtain the maximum SINR link, and associating the ground user with the base station of the maximum SINR link.
4. The method according to claim 3, wherein the capacity coverage enhancement method comprises: by A i,j The received SINR formula is used for further obtaining the reachable rate R of the ground user and the air base station i ＝log 2 (1+γ i ),i∈G∪U。
5. The method according to claim 1, wherein the capacity coverage enhancement method comprises: the specific steps of the base station associated with the maximum SINR link by the ground user in step 3 are as follows: the ground base station informs the base station with the largest SINR link to establish connection preparation, and after confirming the preparation completion to the ground base station, the base station sends access information to the ground base station; the ground user initiates an access request to the base station of the maximum SINR link and establishes connection with the base station, and the ground base station sends an establishment response to the ground user and forwards the access information to the ground user.
6. The method according to claim 1, wherein the specific steps of step 5 are as follows:
step 51: on the ground base station side, initializing the particle group speed and the particle group position, the inertia constant, the acceleration constant and the maximum iteration number I of the particle group algorithm max ；
Step 52: calculate the fitness value Θ (W, p) for each particle BH ) Then evaluating theta at the current position of each particle, comparing the theta with the optimal local fitness and the global fitness of the particle swarm, and updating the position of the optimal local target and the position of the global target;
step 53: updating the speed and position of the particle;
step 54: performing iteration until maximum iteration number I max To solve the optimal deployment position of the aerial base station.
7. The method according to claim 6, wherein the capacity coverage enhancement method comprises: in a step 52, the process is repeated,
the maximum flying speed of the particles is
Figure FDA0003660964750000051
Where N is the number of particle groups and M is the number of airborne base stations, then the velocity matrix of the N particles isIn the k-th iteration can be expressed as
Figure FDA0003660964750000052
Similarly, both the matrix of current positions and the position of the best local target may be used
Figure FDA0003660964750000053
And
Figure FDA0003660964750000054
thus, the location of the best local target of the N particles can be given by the following formula:
Figure FDA0003660964750000055
wherein the position of the optimal local target for the particle is defined in the previous r iterations;
then let
Figure FDA0003660964750000056
Represents the location of the global target and is given by:
Figure FDA0003660964750000057
wherein
Figure FDA0003660964750000058
Is X (k) Is a weighted fitness function, estimates Θ at the current position of each particle and compares it to the best local and global fitness of the particle population, and then uses it separately
Figure FDA0003660964750000059
And
Figure FDA00036609647500000510
updating
Figure FDA00036609647500000511
And
Figure FDA00036609647500000512
a value of (d);
thus, the moving speed of the particle at the (k +1) th iteration may be updated as:
Figure FDA00036609647500000513
where w is expressed as an inertia constant for the exploration of the adaptive control optimization process, c 1 And c 2 Indicating the acceleration constant, in particular when c 1 When 0, the search is set to the highest level, when c 2 When 0, the search is also set to the highest level, and finally, R 1 ，
Figure FDA00036609647500000514
Is [0,1 ]]Indicates a hadamard product, and thus, the position of each particle in the (k +1) iteration can be updated according to its position in the k-th iteration and the motion velocity of the (k +1) iteration, where the position of the particle is updated to be:
X (k+1) ＝X (k) +V (k+1)
8. the method according to claim 7, wherein the capacity coverage enhancement method comprises: in each iteration, the difference between the received and target SINR is calculated as
Figure FDA00036609647500000515
Then consider that the received SINR at the access and direct links is below ε u Ground user set
Figure FDA00036609647500000516
Wherein | upsilon u | represents upsilon u Is equal to, the set of airborne base stations receiving SINR on the backhaul link is below epsilon d Is defined as
Figure FDA00036609647500000517
In the formula
Figure FDA00036609647500000518
Thus, the weighted fitness function may consist of an objective function and a nonlinear inequality constraint, given by:
Figure FDA0003660964750000061
wherein e 1 And e 2 And the penalty parameters are represented and are defined respectively based on the target QoS received by the ground user and the air base station.
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