CN112702703B - Delay tolerant call service request method of multi-hop air base station cooperation - Google Patents

Delay tolerant call service request method of multi-hop air base station cooperation Download PDF

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CN112702703B
CN112702703B CN202011419405.0A CN202011419405A CN112702703B CN 112702703 B CN112702703 B CN 112702703B CN 202011419405 A CN202011419405 A CN 202011419405A CN 112702703 B CN112702703 B CN 112702703B
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base station
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aerial
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CN112702703A (en
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胡熖智
余刚
马大玮
田田
洪利腾
黄伟
施志勇
李立甫
杨舒洵
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Army Engineering University of PLA
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W4/00Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/12Messaging; Mailboxes; Announcements
    • H04W4/14Short messaging services, e.g. short message services [SMS] or unstructured supplementary service data [USSD]
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/14Relay systems
    • H04B7/15Active relay systems
    • H04B7/185Space-based or airborne stations; Stations for satellite systems
    • H04B7/18502Airborne stations
    • H04B7/18504Aircraft used as relay or high altitude atmospheric platform
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W16/00Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/18Network planning tools
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W24/00Supervisory, monitoring or testing arrangements
    • H04W24/02Arrangements for optimising operational condition
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W24/00Supervisory, monitoring or testing arrangements
    • H04W24/06Testing, supervising or monitoring using simulated traffic
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W28/00Network traffic management; Network resource management
    • H04W28/02Traffic management, e.g. flow control or congestion control
    • H04W28/10Flow control between communication endpoints
    • H04W28/14Flow control between communication endpoints using intermediate storage
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W4/00Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30Services specially adapted for particular environments, situations or purposes
    • H04W4/40Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
    • H04W4/46Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for vehicle-to-vehicle communication [V2V]
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W84/00Network topologies
    • H04W84/18Self-organising networks, e.g. ad-hoc networks or sensor networks

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Abstract

A delay tolerant call service request method of multi-hop air base station cooperation comprises the following steps: step 1: determining initial positions by a plurality of aerial base stations; step 2: initiator G1To the called party G2Initiating a call service request; and step 3: the aerial base station processes the call request in the coverage area of a single base station; and 4, step 4: the air base station processes the call request in the coverage range of the cross base station; and 5: the air base station group processes the call request with delay tolerance; step 6: an aerial base station deployment position movement decision; and 7: the air base station activates a call service link; and 8: the air base station is adjusted to the position covering the most ground terminals; and step 9: and (4) concurrent call service handling in the moving process of the air base station. The defects that in the prior art, the aerial base station cannot realize full coverage of all ground terminals, so that the call service cannot be realized among partial ground terminals through aerial base station nodes, and the success rate of the call service among the ground terminals is reduced are effectively overcome.

Description

Delay tolerant call service request method of multi-hop air base station cooperation
Technical Field
The invention relates to the technical field of service request, in particular to a delay tolerant call service request method of multi-hop air base station cooperation.
Background
Compared with manned aircraft, the unmanned aerial vehicle has the advantages of small volume, low cost, convenient use, low requirement on the operation environment, strong battlefield viability and the like. As the unmanned aircraft has important significance for future air battles, the development work of the unmanned aircraft is carried out in all major military countries in the world, and along with the continuous maturation and popularization of the current unmanned aircraft technology, an aerial base station (generally adopting a line-of-sight communication frequency band, such as 300 Mhz-3000 Ghz) taking the unmanned aircraft as a platform has obvious advantages in a communication coverage range relative to a ground relay node (ground base station), and meanwhile, the unmanned aircraft has the advantages of quick moving capability, simple deployment and strong maneuvering flexibility, is widely applied to various fields, and particularly forms a certain application scale in the field of emergency communication.
In a communication network in which the aerial base station is an aerial relay node, possibly due to overlarge ground terminal distribution region or limited temporary aerial base station deployment quantity, full coverage of all ground terminals cannot be realized, so that call service cannot be realized among partial ground terminals through the aerial base station node, and the success rate of the call service among the ground terminals is reduced.
Disclosure of Invention
In order to solve the problems, the invention provides a delay tolerant call service request method of multi-hop air base station cooperation, which effectively overcomes the defects that the air base station in the prior art can not realize full coverage on all ground terminals, so that the call service can not be realized among partial ground terminals through air base station nodes, and the success rate of the call service among the ground terminals is reduced.
In order to overcome the defects in the prior art, the invention provides a solution of a delay tolerant call service request method of multi-hop air base station cooperation, which comprises the following steps:
a delay tolerant call service request method of multi-hop air base station cooperation comprises the following steps:
step 1: determining initial positions by a plurality of aerial base stations;
further, the method for determining the initial position by the plurality of aerial base stations comprises the following steps: setting the number of aerial base stations as m and the number of ground terminals as n, wherein m and n are positive integers, firstly, the aerial base stations should determine the initial positions of deployment, and when all ground terminals in an area cannot be covered, the aerial base station group should enable the number of covered terminals to be the largest, thereby constructing a coverage optimization model and enabling k to be ki(i ═ 1, 2.. n) denotes an air base station UjGround terminal GiIf k is a coverage relationiJ (j ═ 1, 2.. m), this indicates a ground terminal GiIn the air base station UjAnd access the base station if k i0 denotes a ground terminal GiOutside the coverage area of all airborne base stations, assume an airborne base station UjHas an initial position of (x)j,yj) Ground terminal GiIs in the position of (a)i,bi) Then the optimization model of the terminal covered by the air base station group most is shown as formula (1):
Figure BDA0002821618450000021
s.t.
Figure BDA0002821618450000022
wherein | | (x)j,yj)-(ai,bi) I | represents the initial position (x)j,yj) The Euclidean distance between two points is optimized and solved by adopting nonlinear constraintThe solution method obtains the optimal position (x) of the air base station groupj,yj) J is 1, 2. Aerial base station UjThe initial position should be located at the optimal position (x)j,yj)。
Step 2: initiator G1To the called party G2Initiating a call service request;
further, the initiator G1To the called party G2The method for initiating the call service request comprises the following steps:
the initiator G1Sending a call request message, wherein the message format comprises the following elements:
message type, source terminal ID, destination terminal ID, message sequence number SN and time-limited counter T for controlling message bufferH(ii) a The message type is the type of the call request message, the message serial number SN distinguishes different times of call request services, the source terminal ID and the destination terminal ID are respectively the calling party mandy and the called party number of the call service, and the time-limited counter T for controlling the message cacheHSetting a delay tolerance degree according to a calling request of a calling party; when the initiator sends a message, the initiator also starts a local timer, and the timing time T of the local timer is exceededSConsidering the service termination, TSIs slightly larger than TH
When the local timer is overtime or receives the service termination message sent by the air base station, the initiator considers that the service request fails.
And step 3: the aerial base station processes the call request in the coverage area of a single base station;
further, the method for processing the call request in the coverage area of the single base station by the aerial base station comprises the following steps:
setting an airborne base station U1Receiving an initiator G1After the call request message is sent, the called party ID is identified from the call request message, which is forwarded to the called party G2Receiving the called party G when in time2After the call response message is replied to, this indicates the calling party G1And the called party G2Are all in the air base station U1Within the coverage area of the base station U in the air1The called party G is called again2Forwards the call response message to the calling party G1Calling party G1To aerial base station U1Sending a call confirmation message, the air base station completes the connection of the calling party G1Aerial base station and called party G2Call service link G of1-U1-G2And (4) establishing.
And 4, step 4: the air base station processes the call request in the coverage range of the cross base station;
further, the method for processing the call request in the coverage area of the cross base station by the air base station comprises the following steps:
the aerial base station U1Receiving a calling party G1After the call request message is sent, the called party ID is identified from the message, and the message is forwarded to the called party G2Not receiving called party G immediately2When a call response message is returned, this indicates the called party G2Off-air base station U1Within the coverage of (c); if the air base station U1With other air base stations, air base stations U, in communication therewith1Forwarding the call request message in the coverage area of all air base stations connected with it, if called party G2Within the connected air base station group, real-time response is made, i.e. calling party G is connected1Aerial base station U1Aerial base station U2And the called party G2Call service link G of1-U1-U2-G2And (4) establishing.
And 5: the air base station group processes the call request with delay tolerance;
further, the air base station group processes delay tolerant call requests, comprising:
the aerial base station U1Receiving a calling party G1After the call request message is sent, returning to the sequence to execute the step 3 and the step 4, if the call service link can not be immediately established in response to the call request, executing the delay tolerant call request to establish the service link:
step 5-1: if the calling party G1In the air base station U1OfIn-the-air base station U1The called party G is obtained by inquiring other air base stations through Beidou short messages and ad hoc network links2In the air base station U2But an airborne base station U1And an aerial base station U2The ad hoc network link is disconnected, calling party G1After the transmitted call request message reaches the air base station, the message can not be forwarded to the called party G immediately2Calling party G1The calling party U can not obtain the call response immediately1Caching the call request message;
step 5-2: if the calling party G1In the air base station U1Within the coverage area of the base station U in the air1The called party G is obtained by inquiring other base stations through Beidou short messages and Ad hoc network links2Out of coverage of the air base station group, calling party G1After the sent call request message arrives at the air base station, the message can not be forwarded to the called party G2 instantly, and the calling party G1If the call response can not be obtained immediately, the air base station U1Caching the call request message;
step 5-3: if the calling party G1Out of the coverage area of the air base station, the calling request message of the calling party G1 reaches the air base station U in the form of a Beidou short messageaAerial base station UaThen, other base stations are inquired to obtain the called party G through the Beidou short message form and the Ad hoc network link2In the air base station U2Within the coverage area of (2), then the aerial base station UaCaching the call request message;
step 5-4: if the calling party G1Out of coverage of the airborne base station, calling party G1The call request message reaches an aerial base station U in the form of Beidou short messageaAerial base station UaThen, other base stations are inquired to obtain the called party G through the Beidou short message form and the Ad hoc network link2If the mobile station is not in the coverage area of the air base station group, the air base station UaThe call request message is buffered.
Step 6: an aerial base station deployment position movement decision;
further, the method for making the aerial base station deployment position movement decision comprises the following steps:
step 6-1: for step 5-1, the airborne base station U1According to the source terminal ID and the destination terminal ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And the called party G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station U1The number of base stations in the air in a communication area can be obtained, and the specific processing flow is as follows:
step 6-1-1: if m is 2, and | | (a)1,b1)-(a2,b2) If the | is more than R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) If the | is less than or equal to R +2R, the air base station executes a position moving strategy;
setting two air base stations U1And an aerial base station U2Respectively by position (x)1,y1) And (x)2,y2) Moving straight to horizontal position point (x)1′,y1') and (x)2′,y2') and according to equation (2):
min{max{||(x1,y1)-(x1′,y1′)||,||(x2,y2)-(x2′,y2′)||}} (2)
s.t.
Figure BDA0002821618450000061
solving (x) in conjunction with non-linear constraint-based optimization algorithms1′,y1') and (x)2′,y2'), let d ═ min { max { | (x)1,y1)-(x1′,y1′)||,||(x2,y2)-(x2′,y2') | | } if
Figure BDA0002821618450000062
The air base station suspends the operationService request; if it is
Figure BDA0002821618450000063
The aerial base station will adjust the horizontal position deployment to move along a straight line to (x)1′,y1') and (x)2′,y2′);
Step 6-1-2: if m >2, and | | (a)1,b1)-(a2,b2) R +2R is less than or equal to | |, then covering the calling party G1And the called party G2Aerial base station U1And an aerial base station U2Executing the operation of step 6-1-1;
and wherein if
Figure BDA0002821618450000064
Continuing to execute subsequent operation without stopping the service request; if (a)1,b1)-(a2,b2) If the | | is more than 2R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) R +2R is less than or equal to | |
Figure BDA0002821618450000065
Or R +2R < | | (a)1,b1)-(a2,b2) If | | | is less than or equal to 2R +2R, then the aerial base station U1From removing aerial base station U1And an aerial base station U2Selecting one idle base station from other base stations and recording as an air base station U3Three airborne base stations implement a mobility strategy;
setting three airborne base stations, i.e. airborne base stations U1Aerial base station U2And an aerial base station U3Respectively by position (x)1,y1)、(x2,y2) And (x)3,y3) Moving straight to horizontal position point (x)1′,y1′)、(x2′,y2') and (x)3′,y3') and according to equation (3):
min{max{||(x1,y1)-(x1′,y1′)||,||(x2,y2)-(x2′,y2′)||,||(x3,y3)-(x3′,y3′)||}} (3)
s.t.
Figure BDA0002821618450000071
solving (x) in conjunction with non-linear constraint-based optimization algorithms1′,y1′)、(x2′,y2') and (x)3′,y3'), let d ═ min { max { | (x)1,y1)-(x1′,y1′)||,||(x2,y2)-(x2′,y2′)||,||(x3,y3)-(x3′,y3') | | } if
Figure BDA0002821618450000072
The air base station stops the service request; if it is
Figure BDA0002821618450000073
The aerial base station will adjust the horizontal position deployment to move along a straight line to (x)1′,y1′)、(x2′,y2') and (x)3′,y3′);
Step 6-2: for step 5-2, the airborne base station U1According to the source end ID and the destination end ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And the called party G2The horizontal position coordinates are respectively (a)1,b1) And (a)2,b2) Simultaneous air base station U1The number of base stations in the air in a communication area can be obtained, and the specific processing flow is as follows:
step 6-2-1: if (a)1,b1)-(a2,b2) When | | < 2R, then the aerial base station U1Executing the position moving strategy and setting the air base station U1From the horizontal position (x)1,y1) Moving straight to horizontal position point (x)1′,y1') and according to equation (4):
min||(x1,y1)-(x1′,y1′)|| (4)
s.t.
Figure BDA0002821618450000081
solving (x) in conjunction with non-linear constraint-based optimization algorithms1′,y1'), let d | | (x)1,y1)-(x1′,y1') | | if
Figure BDA0002821618450000082
The aerial base station will adjust the horizontal position deployment to move along a straight line to (x)1′,y1′);
Step 6-2-2: if m is 2, except for the airborne base station U1Another aerial base station as U2Next, it is performed with reference to step 6-1-1;
step 6-2-3: if m is more than 2, the aerial base station U1Distance called party G is scheduled and selected through an ad hoc network link or in a Beidou short message mode2Nearest and idle aerial base station as aerial base station U2Next, it is performed with reference to step 6-1-2;
step 6-3: for step 5-3, the airborne base station UaAccording to the source end ID and the destination end ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And called G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station UaThe number of base stations in the air in a communication area can be obtained, and the processing flow is as follows:
step 6-3-1: first of all by covering the called party G2Aerial base station U2Is performed with reference to step 6-2-1;
step 6-3-2: if m is 2, except for the airborne base station U2Another aerial base station is used as U1Next, it is performed with reference to step 6-1-1;
step 6-3-3: if m is more than 2, the aerial base station UaScheduling an air base station through an ad hoc network link or in a Beidou short message mode, wherein the selection principle is that the distance from a calling party G is1Nearest and idle aerial base station as U1Or according to the principle, the aerial base station UaItself as an aerial base station U1Next, it is performed with reference to step 6-1-2;
step 6-4: for step 5-4, the airborne base station UaAccording to the source terminal ID and the destination terminal ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And called G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station UaThe number of base stations in the air in a communication area can be obtained, and the processing flow is as follows:
step 6-4-1: aerial base station UaThe air base station is scheduled and selected through an ad hoc network link or in a Beidou short message mode, and the principle is that the calling party G is reached1And the called party G2The idle aerial base station with the shortest distance sum or U is selected according to the principleaSelf, the execution is carried out with reference to the step 6-2-1;
step 6-4-2: if m is 2, G is distance from the calling party1The near aerial base station is used as an aerial base station U1From the called party G2The nearest aerial base station is taken as an aerial base station U2Next, with reference to step 6-1-1;
step 6-4-3: if m is more than 2, the aerial base station UaThe air base station is scheduled and selected through an ad hoc network link or in a Beidou short message mode, and the principle is that the calling party G is reached1And the called party G2Two idle aerial base stations with the distance sum being sequentially nearest are used as aerial base stations U1And an aerial base station U2Wherein is distant from the calling party G1The nearest aerial base station is taken as an aerial base station U1From the called party G2The nearest aerial base station is taken as an aerial base station U2Or according to the principle, the aerial base station UaItself as an aerial base station U1Or aerial base station U2Is connected to nextIs performed with reference to step 6-1-2.
And 7: the air base station activates a call service link;
further, the method for activating the call service link by the air base station comprises the following steps: moving the base station group to the estimated position and calling party G1Forwards the call request message to the called party G2Receiving the called party G2After the call response message, forwards it to the calling party G1Receiving the calling party G1After the call confirmation message, the service link is activated; in which the called party G cannot be normally received2Call response message and calling party G1When the call confirmation message is received, the service request is terminated.
And 8: the air base station is adjusted to the position covering the most ground terminals;
further, the method for adjusting the air base station to the position covering the most ground terminals comprises the following steps:
end calling party G1And the called party G2After the inter-call service, the mobile air base station group carries out local optimized coverage on the ground terminals which are not within the coverage radius of other air base stations according to the position distribution of the current ground terminals and the positions of other air base stations, namely, the ground terminals cover the maximum number of ground terminals and linearly move to the estimated position, wherein the solution model is executed according to the step 1.
And step 9: handling concurrent call service in the moving process of the air base station;
further, the method for handling concurrent call service during the moving process of the air base station includes:
the air base station processes the concurrent call service in the parking state and executes the concurrent call service according to the normal flow of the existing air base station, if other concurrent call service requests are sent in the moving process, the air base station supplements the call service
The charging treatment method comprises the following steps:
step 9-1: preferentially ensuring real-time request call service: if the instant response is obtained when the call request message is forwarded, which indicates that both sides of the newly added call service are in the coverage range of the base station, then the priority isFirstly, ensuring the normal operation of the service of the real-time request call, namely, the moving direction is not changed, but when the signals of two parties or one party of the newly added real-time request call are about to be lower than the receiving threshold, stopping moving to maintain the current position until the service is ended, and counting the time consumed by the calling party G1To the called party G2The calling party G should be terminated directly by delaying the call request, resulting in a timeout1To the called party G2Then, the service request is carried out in step 7;
step 9-2: if other new call service requests are simultaneously sent and it is difficult to realize that the new request call should be brought into the subsequent service queue of the air base station in real time, the buffer memory is carried out and the buffer memory timing is started, and the calling party G is processed1To the called party G2In between, the subsequent delay tolerant call requests are processed in a first-in-first-out queue, resulting in the overtime request to be cleared or terminated from the queue.
The invention has the beneficial effects that:
aiming at the situation that the networking communication coverage of a plurality of air base stations is insufficient, how to realize the call service between uncovered ground terminals and meet the emergency communication requirement between partial ground terminals is realized, the invention combines the characteristics of quick movement of the air base stations and flexible change of network topology, reforms the precondition requirement of the traditional call service on link communication and the application characteristic of 'one call and one connection', and provides a delay tolerant call service request method with cooperation of a plurality of base stations.
Drawings
FIG. 1 is a schematic diagram of the present invention for building a coverage optimization model.
Fig. 2 is a schematic diagram of elements in a message format of the present invention.
FIG. 3 is a schematic diagram of an air base station U of the present invention instantly establishing a call service link G1-U-G2Schematic representation of (a).
FIG. 4 is a diagram of the present invention for establishing a call via an airborne base station U1 and an airborne base station U2Caller service link G1-U1-U2-G2Schematic representation of (a).
Fig. 5 is a diagram illustrating the movement of a base station in m-2 space-time according to the present invention.
FIG. 6 is a diagram illustrating the movement of a base station in m >2 space-time according to the present invention.
FIG. 7 is an air base station U of the present invention1Schematic representation of the movement.
Fig. 8 is a flow chart of the delay tolerant call service request method of multi-hop over-the-air base station cooperation of the present invention.
Detailed Description
The invention will be further described with reference to the following figures and examples.
In the present invention, it should have:
1. the air base station node should include a call service control message buffer unit. The format of the call control message sent should include: message type, source terminal ID, destination terminal ID, message sequence number SN, time-limited counter T for controlling message buffer of messageHThe message types include types of a call request message, a call response message, and a call confirmation message. T isHIs determined by the call service originating terminal according to the maximum tolerated delay, in seconds. The maximum tolerable delay is determined according to the expected value of the communication service connection time of the user, and is usually set by the user according to the personal demand condition. For example, the maximum tolerable delay tolerance of the user is 50S, which means that the user desires to be switched on within 50 seconds, and if the maximum tolerable delay tolerance exceeds 50S, the service is abandoned.
2. The air base station and the ground terminals integrate the functions of Beidou positioning and short message, the air base station can acquire the position information of other air base stations and the position information of all the ground terminals, and if n ground terminals are provided, the positions are (a)i,bi) I is 1,2, …, n. Wherein n is the number of ground terminals, i is the number of ground terminals, (a)i,bi) Ground exact coordinates for ground terminals, aiLongitude coordinates which are ground-precise coordinates of the ground terminal, biLatitude coordinates which are accurate coordinates of the ground terminal.
3. The air base station is raised to a certain height according to the terrain of a region to realize the sight distance coverage of most regions, the reference radius of the horizontal coverage range of the ground terminal is R, the average moving speed is v, and in order to provide a certain redundancy, the reference radius of the horizontal coverage range is recommended to be set with a conservative R value.
4. The air base station integrates an ad hoc network link, the maximum communication radius is r, a plurality of air base stations are supported to form a relay network which is interconnected and communicated, and a calling service link is relayed by one or more air base stations from a ground terminal to another ground terminal.
5. According to the time delay requirement of call service transmission, the information carrying the call of the sending terminal reaches the receiving terminal of the opposite side through 4 hops (namely 3 air base station relays) at most.
6. Different air base stations use different frequencies, and the networking among different base stations can avoid wireless interference.
7. The ground terminal is switched between different base stations in a cross-zone way, according to the receiving threshold criterion, the switching can not happen even if the signal intensity of the original receiving base station is lower than the signal intensity of the adjacent base station, and the adjacent base station meeting the requirements is selected to be accessed only if the signal intensity of the original receiving base station is lower than the receiving threshold (exceeds the coverage range of the original receiving base station).
8. Judging whether the terminal is in the coverage area of a certain air base station or not is realized according to the request and confirmation of the message, which is actually accurate and should be adopted as much as possible under the implementation condition; and coverage optimization and movement decision, which is to judge whether the deployment position covers the ground terminal or not, are judged according to the line-of-sight transmission distance, which is theoretically accurate and may have certain errors in engineering.
9. The air base station movement decision estimation in the process of processing the delay tolerant call service request is a simpler nonlinear constraint optimization problem, and the processing time is ignored.
As shown in fig. 1-8, a method for requesting a delay tolerant call service in multi-hop air base station cooperation includes:
step 1: determining initial positions by a plurality of aerial base stations;
the plurality of aerial base stationsA method of determining an initial position, comprising: setting the number of aerial base stations as m and the number of ground terminals as n, wherein m and n are positive integers, firstly, the aerial base stations should determine the initial positions of deployment, and when all ground terminals in an area cannot be covered, the aerial base station group should enable the number of covered terminals to be the largest, thereby constructing a coverage optimization model and enabling k to be ki(i ═ 1, 2.. n) denotes an air base station UjGround terminal GiJ is the number of the air base station, i is the number of the ground terminal, if kiJ (j ═ 1, 2.. m), this indicates a ground terminal GiIn the air base station UjAnd access the base station if ki0 denotes a ground terminal GiOutside the coverage area of all airborne base stations, assume an airborne base station UjHas an initial position of (x)j,yj) Ground terminal GiIs in the position of (a)i,bi),(xj,yj) Is an aerial base station UjWhere j is the number of the aerial base station, xjIs an aerial base station UjOf ground exact coordinates, yjIs an aerial base station UjThe ground accurate coordinates of the vehicle.
Then, as shown in fig. 1, the optimization model of the air base station group covering the most terminals is shown in formula (1):
Figure BDA0002821618450000141
s.t.
Figure BDA0002821618450000142
wherein | | (x)j,yj)-(ai,bi) I represents an aerial base station UjInitial position (x)j,yj) Dough kneading terminal GiPosition (a) ofi,bi) The optimal position of the air base station group can be obtained by adopting a nonlinear constraint optimization solving method for the Euclidean distance between two points(xj,yj) J is 1, 2. Aerial base station UjThe initial position should be located at the optimal position (x)j,yj). The nonlinear constraint optimization solution method can be a heuristic algorithm. The air base station group is composed of all air base stations. (a)i,bi) For ground terminal GiI is the ground terminal number, aiFor ground terminal GiLongitude coordinates of ground exact coordinates, biFor ground terminal GiThe ground accurate coordinates of the vehicle. (x)j,yj) Is an aerial base station UjWhere j is the number of the aerial base station, xjIs an aerial base station UjOf ground exact coordinates, yjIs an aerial base station UjThe ground accurate coordinates of the vehicle.
Step 2: initiator G1To the called party G2Initiating a call service request; initiator G1And the called party G2Are all ground terminals.
The initiator G1To the called party G2The method for initiating the call service request comprises the following steps:
the initiator G1Sending a call request message, wherein the message format comprises the following elements:
message type, source terminal ID, destination terminal ID, message sequence number SN and time-limited counter T for controlling message bufferH(ii) a The message type is the type of the call request message, the message serial number SN distinguishes the call request service of different times, the source terminal ID and the target terminal ID are the calling party number and the called party number of the call service of the time respectively, and the time-limited counter T for controlling the message cacheHSetting a delay tolerance degree according to a calling request of a calling party; when the initiator sends a message, the initiator also starts a local timer, and the timing time T of the local timer is exceededSConsidering the service termination, wherein the time delay of the transmission and processing process is considered, TSIs slightly larger than TH
When the local timer is overtime or receives the service termination message sent by the air base station, the initiator considers that the service request fails.
And step 3: the aerial base station processes the call request in the coverage area of a single base station;
the method for processing the call request in the coverage area of the single base station by the air base station comprises the following steps:
setting an airborne base station U1Receiving an initiator G1After the call request message is sent, the called party ID is identified from the call request message, which is forwarded to the called party G2Receiving the called party G when in time2After the call response message is replied to, this indicates the calling party G1And the called party G2Are all in the air base station U1Within the coverage area of the base station U in the air1The called party G is called again2Forwards the call response message to the calling party G1Calling party G1To aerial base station U1When the call confirmation message is sent, the air base station completes the connection of the calling party G as shown in figure 31Aerial base station and called party G2Call service link G of1-U1-G2And (4) establishing.
And 4, step 4: the air base station processes the call request in the coverage range of the cross base station;
the method for processing the call request in the coverage area of the cross base station by the air base station comprises the following steps:
the aerial base station U1Receiving a calling party G1After the call request message is sent, the called party ID is identified from the message, and the message is forwarded to the called party G2Not receiving called party G immediately2When a call response message is returned, this indicates the called party G2Off-air base station U1Within the coverage of (c); if the air base station U1With other air base stations, air base stations U, in communication therewith1Forwarding the call request message in the coverage area of all air base stations connected with it, if called party G2Within the connected air base station group, i.e. in real time, the called party G is shown in figure 42In the air base station U2In-coverage and air base station U1And an aerial base station U2Connected via an ad hoc network link, the called party G2To aerial base station U2Sending a call response message and forwarding the call response message to an air base station U1Finally forwarded to the calling party G1Calling party G1Answering the call confirmation message, i.e. connecting the calling party G1Aerial base station U1Aerial base station U2And the called party G2Call service link G of1-U1-U2-G2And (4) establishing.
And 5: the air base station group processes the call request with delay tolerance;
the group of air base stations processing delay tolerant call requests, comprising:
the aerial base station U1Receiving a calling party G1After the call request message is sent, returning to the sequence to execute the step 3 and the step 4, if the call service link can not be immediately established in response to the call request, executing the delay tolerant call request to establish the service link:
step 5-1: if the calling party G1In the air base station U1Within the coverage area of the base station U in the air1The called party G is obtained by inquiring other air base stations through Beidou short messages and ad hoc network links2In the air base station U2But an airborne base station U1And an aerial base station U2The ad hoc network link is disconnected, calling party G1After the transmitted call request message reaches the air base station, the message can not be forwarded to the called party G immediately2Calling party G1The calling party U can not obtain the call response immediately1Caching the call request message;
step 5-2: if the calling party G1In the air base station U1Within the coverage area of the base station U in the air1The called party G is obtained by inquiring other base stations through Beidou short messages and Ad hoc network links2Out of coverage of the air base station group, calling party G1After the sent call request message arrives at the air base station, the message can not be forwarded to the called party G2 instantly, and the calling party G1If the call response can not be obtained immediately, the air base station U1Caching the call requestA message;
step 5-3: if the calling party G1Out of the coverage area of the air base station, the calling request message of the calling party G1 reaches the air base station U in the form of a Beidou short messageaAerial base station UaThen, other base stations are inquired to obtain the called party G through the Beidou short message form and the Ad hoc network link2In the air base station U2Within the coverage area of the base station U in the airaOr may be the aerial base station U2Then aerial base station UaCaching the call request message; the Beidou short message form can adopt the record selection of the nearest access aerial base station, and also can preset a certain base station in advance as the base station for selecting the Beidou short message access when the base station is not in the coverage range.
Step 5-4: if the calling party G1Out of coverage of the airborne base station, calling party G1The call request message reaches an aerial base station U in the form of Beidou short messageaAerial base station UaThen, other base stations are inquired to obtain the called party G through the Beidou short message form and the Ad hoc network link2If the mobile station is not in the coverage area of the air base station group, the air base station UaThe call request message is buffered.
Step 6: an aerial base station deployment position movement decision;
the method for the aerial base station deployment position movement decision comprises the following steps:
step 6-1: for step 5-1, the airborne base station U1According to the source terminal ID and the destination terminal ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And the called party G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station U1The number of base stations in the air in a communication area can be obtained, and the specific processing flow is as follows: called party G2To the destination terminal, calling party G1Is the source terminal. (a)1,b1) And (a)2,b2) Respectively ground terminal calling party G1And the called party G2The horizontal position coordinates of (a). a is1、a2As corresponding longitude coordinates, b1、b2Corresponding latitude coordinates.
Step 6-1-1: if m is 2, and | | (a)1,b1)-(a2,b2) If the | is more than R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) If the | is less than or equal to R +2R, the air base station executes a position moving strategy;
wherein R is the effective communication distance between the air base stations, and R is the conservative value of the horizontal coverage range of the air base station to the ground terminal, i.e. the minimum value of the coverage range taken under the condition of ensuring the effectiveness of the coverage range of the air base station and having a certain redundancy.
Setting two air base stations U1And an aerial base station U2Respectively by position (x)1,y1) And (x)2,y2) Moving straight to horizontal position point (x)1′,y1') and (x)2′,y2′),(x1,y1) And (x)2,y2) Initial position coordinates, x, of the airborne base station U1 and the airborne base station U2, respectively1、x2Is the corresponding longitude coordinate, y1、y2Corresponding latitude coordinates. (x)1′,y1') and (x)2′,y2') position coordinates, x, of the first time the airborne base station U1 and the airborne base station U2 have moved as required1' and x2' is the corresponding longitudinal coordinate, y1′、y2' is the corresponding latitude coordinate. And according to formula (2):
min{max{||(x1,y1)-(x1′,y1′)||,||(x2,y2)-(x2′,y2′)||}} (2)
s.t.
Figure BDA0002821618450000191
solving (x) in conjunction with non-linear constraint-based optimization algorithms1′,y1') and (x)2′,y2'), let d ═ min { max { | (x)1,y1)-(x1′,y1′)||,||(x2,y2)-(x2′,y2') | | } if
Figure BDA0002821618450000192
The air base station stops the service request; if it is
Figure BDA0002821618450000193
d is an air base station U1 and an air base station U2
The maximum value of the linear distance (shortest movement) values between the initial position and the position after the first movement is shown as v, the average moving speed of the unmanned aerial vehicle and THA time limited counter value buffered for the control message. The formula means that the maximum value of the moving process time of the air base station cannot exceed the value of a time-limited counter (user delay tolerance), and moving beyond the value is meaningless.
As shown in fig. 5, the air base station will adjust the horizontal position to deploy, move to (x) along a straight line1′,y1') and (x)2′,y2′);
Step 6-1-2: if m >2, and | | (a)1,b1)-(a2,b2) R +2R is less than or equal to | |, then covering the calling party G1And the called party G2Aerial base station U1And an aerial base station U2Executing the operation of step 6-1-1;
and wherein if
Figure BDA0002821618450000201
Continuing to execute subsequent operation without stopping the service request; if (a)1,b1)-(a2,b2) If the | | is more than 2R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) R +2R is less than or equal to | |
Figure BDA0002821618450000202
Or R +2R < | | (a)1,b1)-(a2,b2) If | | | is less than or equal to 2R +2R, then the aerial base station U1From removing aerial base station U1And an aerial base station U2Selecting one idle base station from other base stations and recording as an air base station U3Three airborne base stations implement a mobility strategy; the selected one may be to an airborne base station U1And an aerial base station U2And if no idle base station is available, the idle base station with the minimum distance sum is added into the queue to delay the selection after waiting for the idle base station.
Three air base stations, namely an air base station U1, an air base station U2 and an air base station U3 are respectively set to be composed of positions (x)1,y1)、(x2,y2) And (x)3,y3) Moving straight to horizontal position point (x)1′,y1′)、(x2′,y2') and (x)3′,y3') and according to equation (3):
min{max{||(x1,y1)-(x1′,y1′)||,||(x2,y2)-(x2′,y2′)||,||(x3,y3)-(x3′,y3′)||}} (3)
s.t.
Figure BDA0002821618450000203
solving (x) in conjunction with non-linear constraint-based optimization algorithms1′,y1′)、(x2′,y2') and (x)3′,y3'), let d ═ min { max { | (x)1,y1)-(x1′,y1′)||,||(x2,y2)-(x2′,y2′)||,||(x3,y3)-(x3′,y3') | | } if
Figure BDA0002821618450000204
The air base station stops the service request; if it is
Figure BDA0002821618450000205
As shown in fig. 6, the air base station will adjust the horizontal position to deploy, move to (x) along a straight line1′,y1′)、(x2′,y2') and (x)3′,y3') to a host; when m is 2, 2 air base stations are illustrated, and each air base station is an air base station U1The other is an air base station U2If (a)1,b1)-(a2,b2) If the | is more than R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) If | | < R +2R, the air base station executes the position moving strategy, so that the ground terminal G1And G2Respectively in an aerial base station U1And U2And an aerial base station U1And U2And if the communication requirement is met, judging the condition according to the moving position distance, and judging whether the position moving adjustment requirement is met.
Step 6-2: for step 5-2, the airborne base station U1According to the source end ID and the destination end ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And the called party G2The horizontal position coordinates are respectively (a)1,b1) And (a)2,b2) Simultaneous air base station U1The number of base stations in the air in a communication area can be obtained, and the specific processing flow is as follows:
step 6-2-1: if (a)1,b1)-(a2,b2) When | | < 2R, then the aerial base station U1Executing the position moving strategy and setting the air base station U1From the horizontal position (x)1,y1) Moving straight to horizontal position point (x)1′,y1') and according to equation (4):
min||(x1,y1)-(x1′,y1′)|| (4)
s.t.
Figure BDA0002821618450000211
solving (x) in conjunction with non-linear constraint-based optimization algorithms1′,y1'), let d | | (x)1,y1)-(x1′,y1') | | if
Figure BDA0002821618450000212
As shown in fig. 7, the air base station will adjust the horizontal position to deploy, move to (x) along a straight line1′,y1′);
Step 6-2-2: if m is 2, except for the airborne base station U1Another aerial base station as U2Next, it is performed with reference to step 6-1-1; when m is 2, 2 air base stations are illustrated, and each air base station is an air base station U1The other is an air base station U2If (a)1,b1)-(a2,b2) If the | is more than R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) If | | < R +2R, the air base station executes the position moving strategy, so that the ground terminal G1And G2Respectively in an aerial base station U1And U2And an aerial base station U1And U2And if the communication requirement is met, judging the condition according to the moving position distance, and judging whether the position movement is met.
Step 6-2-3: if m is more than 2, the aerial base station U1Distance called party G is scheduled and selected through an ad hoc network link or in a Beidou short message mode2Nearest and idle aerial base station as aerial base station U2Next, it is performed with reference to step 6-1-2; when m is more than 2, at least 3 air base stations are shown, and are respectively air base stations U1In addition, air base station U1Dispatching and selecting distance called party terminal G through ad hoc network link or in the form of Beidou short message2Nearest and idle aerial base station as aerial base station U2If G is found by positioning calculation1And G2The distance between the terminal positions satisfies | (a)1,b1)-(a2,b2) If the | | is less than or equal to R +2R, executing according to the step 6-1-1; if | | (a1,b1)-(a2,b2) If the distance is greater than 2R +2R, the air base station stops the service request, and 3 air base stations with too large distance cannot meet the information communication requirement; if (a)1,b1)-(a2,b2) R +2R is less than or equal to | |
Figure BDA0002821618450000221
Or R +2R < | | (a)1,b1)-(a2,b2) If | | | is less than or equal to 2R +2R, then the aerial base station U1From removing aerial base station U1And an aerial base station U2Selecting one idle base station from other base stations and recording as an air base station U3Said selected airborne base station U3May be to an airborne base station U1And an aerial base station U2The idle air base station with the minimum distance sum executes the position moving strategy so that the ground terminal G1And G2Respectively in an aerial base station U1And U2Within the coverage of, empty base station U3Then as the base station U1And U2And the communicated intermediate transfer base station judges the condition according to the moving position distance and judges whether the position moving adjustment requirement is met.
Step 6-3: for step 5-3, the airborne base station UaAccording to the source end ID and the destination end ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And called G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station UaThe number of base stations in the air in a communication area can be obtained, and the processing flow is as follows:
step 6-3-1: first of all by covering the called party G2Aerial base station U2Is performed with reference to step 6-2-1; aerial base station U2Obtaining calling party terminal G through Beidou positioning function1And the called party G2The coordinate position of (a) is obtained by calculation1,b1)-(a2,b2) If | | < 2R, then indicate the aerial base station U2Can simultaneously cover 2 ground terminals, then calculate the optimal position movementStrategy, if the shortest distance d of the moving base station in the air can satisfy d | | (x)1,y1)-(x1′,y1′)||,
Figure BDA0002821618450000231
The location movement policy is executed.
Step 6-3-2: if m is 2, except for the airborne base station U2Another aerial base station is used as U1Next, it is performed with reference to step 6-1-1;
step 6-3-3: if m is more than 2, the aerial base station UaScheduling selection principle as a distance calling party G through an ad hoc network link or in a form of Beidou short message1Nearest and idle aerial base station as U1Or according to the principle, the aerial base station UaItself as an aerial base station U1Next, it is performed with reference to step 6-1-2; when m is more than 2, at least 3 air base stations are shown, and are respectively air base stations U2In addition, air base station UaDispatching and selecting distance calling and called party terminal G through ad hoc network link or in the form of Beidou short message1Nearest and idle aerial base station as aerial base station U1And possibly UaSelf-off terminal G1Nearest and idle, UaIs namely U1If G is found by positioning calculation1And G2The distance between the terminal positions satisfies | (a)1,b1)-(a2,b2) If the | | is less than or equal to R +2R, executing according to the step 6-1-1; if (a)1,b1)-(a2,b2) If the distance is greater than 2R +2R, the air base station stops the service request, and 3 air base stations with too large distance cannot meet the information communication requirement; if (a)1,b1)-(a2,b2) When | | < R +2R and 2 aerial base stations move
Figure BDA0002821618450000232
Or R +2R < | | (a)1,b1)-(a2,b2) If | | | is less than or equal to 2R +2R, then the aerial base station U2From removing aerial base station U1And an aerial base station U2Selecting one idle base station from other base stations, and recording asAerial base station U3Said selected airborne base station U3May be to an airborne base station U1And an aerial base station U2The idle air base station with the minimum distance sum executes the position moving strategy so that the ground terminal G1And G2Respectively in an aerial base station U1And U2Within the coverage of, empty base station U3Then as the base station U1And U2And the communicated intermediate transfer base station judges the condition according to the moving position distance and judges whether the position moving adjustment requirement is met.
Step 6-4: for step 5-4, the airborne base station UaAccording to the source end ID and the destination end ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And called G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station UaThe number of base stations in the air in a communication area can be obtained, and the processing flow is as follows:
step 6-4-1: aerial base station UaThe air base station is scheduled and selected through an ad hoc network link or in a Beidou short message mode, and the principle is that the calling party G is reached1And the called party G2The idle aerial base station with the shortest distance sum or U is selected according to the principleaBy itself, to refer to the reference step 6-2-1 execution; aerial base station UaThe air base station U is scheduled and selected through an ad hoc network link or in a Beidou short message mode, and the principle is that the calling party G is reached1And the called party G2The distance sum is nearest and idle, and the aerial base station U acquires the calling party terminal G through the Beidou positioning function1And the called party G2The coordinate position of (a) is obtained by calculation1,b1)-(a2,b2) If | | is less than or equal to 2R, it indicates that the air base station U can simultaneously cover 2 ground terminals, then an optimal position movement strategy is calculated, and if the shortest distance d of the air base station movement can satisfy d | (x |)1,y1)-(x1′,y1′)||,
Figure BDA0002821618450000241
The location movement policy is executed. Here UaI.e. possibly that satisfactory airborne base station U.
Step 6-4-2: if m is 2, G is distance from the calling party1The near aerial base station is used as an aerial base station U1From the called party G2The nearest aerial base station is taken as an aerial base station U2Next, with reference to step 6-1-1; when m is 2, 2 air base stations are illustrated, and the distance G from the calling party can be determined through Beidou positioning1The near aerial base station is used as an aerial base station U1From the called party G2The nearest aerial base station is taken as an aerial base station U2Terminal G1And terminal G2Distance (a)1,b1)-(a2,b2) If the | is more than R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) If | | < R +2R, the air base station executes the position moving strategy, so that the ground terminal G1And G2Respectively in an aerial base station U1And U2And an aerial base station U1And U2And if the communication requirement is met, judging the condition according to the moving position distance, and judging whether the position moving adjustment requirement is met.
Step 6-4-3: if m is more than 2, the aerial base station UaScheduling selection principle to calling party G through ad hoc network link or in the form of Beidou short message1And the called party G2Two idle aerial base stations with the distance sum being sequentially nearest are used as aerial base stations U1And an aerial base station U2Wherein is distant from the calling party G1The nearest aerial base station is taken as an aerial base station U1From the called party G2The nearest aerial base station is taken as an aerial base station U2Or according to the principle, the aerial base station UaItself as an aerial base station U1Or aerial base station U2And is next performed with reference to step 6-1-2. When m is more than 2, at least 3 air base stations are shown, and are respectively a distance calling party terminal G1Nearest airborne base station U1Distance called party terminal G2Nearest airborne base station U2(Here, UaMay itself be U1Or U2) If G is found by positioning calculation1And G2The distance between the terminal positions satisfies | (a)1,b1)-(a2,b2) If the | | is less than or equal to R +2R, executing according to the step 6-1-1; if (a)1,b1)-(a2,b2) If the distance is greater than 2R +2R, the air base station stops the service request, and 3 air base stations with too large distance cannot meet the information communication requirement; if (a)1,b1)-(a2,b2) When | | < R +2R and only 2 base stations move, the method makes | | | < R +2R
Figure BDA0002821618450000251
Or R +2R < | | (a)1,b1)-(a2,b2) If | | < 2R +2R, then from aerial base station U1And U2Selecting one idle base station from other base stations and recording as an air base station U3Said selected airborne base station U3May be to an airborne base station U1And an aerial base station U2The idle air base station with the minimum distance sum executes the position moving strategy so that the ground terminal G1And G2Respectively in an aerial base station U1And U2Within the coverage of, empty base station U3Then as the base station U1And U2And the communicated intermediate transfer base station judges the condition according to the moving position distance and judges whether the position moving adjustment requirement is met.
And 7: the air base station activates a call service link;
the method for activating the call service link by the air base station comprises the following steps: in each case, the calling party G is moved to the estimated location by the air base station group1Forwards the call request message to the called party G2Receiving the called party G2After the call response message, forwards it to the calling party G1Receiving the calling party G1After the call confirmation message is received, the service link (which may be a single base station relay, a two base station relay or a three base station relay network) is activated; in which the called party G cannot be normally received2Call response message and calling party G1Of the call acknowledgement messageAnd the service request is terminated.
And 8: the air base station is adjusted to the position covering the most ground terminals;
the method for adjusting the air base station to the position covering the most ground terminals comprises the following steps:
end calling party G1And the called party G2After the inter-call service, the mobile air base station group carries out local optimized coverage on the ground terminals which are not within the coverage radius of other air base stations according to the position distribution of the current ground terminals and the positions of other air base stations, namely, the ground terminals cover the maximum number of ground terminals and linearly move to the estimated position, wherein the solution model is executed according to the step 1. Referring to step 1, after the air base station completes the current service, the air base station group should make the number of covered terminals the maximum, and the position adjustment is performed according to the calculation strategy of the model formula (1).
And step 9: handling concurrent call service in the moving process of the air base station;
the method for handling the concurrent call service in the moving process of the air base station comprises the following steps:
the air base station processes the concurrent call service in the parking state and executes the processing according to the normal flow of the existing air base station, and if other call service requests are concurrent in the moving process, the supplementary processing method comprises the following steps:
step 9-1: preferentially ensuring real-time request call service: since the delay tolerant call service request method is a supplement to the normal service, the normal real-time request call service should be satisfied preferentially. If an instant response is obtained when the call request message is forwarded, indicating that both parties of the newly-added call service are in the coverage range of the base station, preferentially ensuring that the service of the real-time request call is normally carried out, namely the moving direction is unchanged, but when the signal of both parties or one party of the newly-added real-time request call is about to be lower than a receiving threshold, stopping moving to maintain the current position until the service is finished, counting the consumed time into the call request delay from a calling party G1 to a called party G2, causing overtime, directly terminating the service request from the calling party G1 to the called party G2, and then turning to the step 7 for execution; reception threshold meaning: in information communication, the minimum value of signal transmission and reception between both communication parties set for ensuring communication quality is lower than the minimum value, and normal communication cannot be performed. For example, the receiving threshold is 50dB, and a signal strength higher than 50dB indicates normal communication, and a signal strength lower than 50dB indicates poor signal and normal communication is impossible.
Step 9-2: if other new call service requests are simultaneously sent and it is difficult to realize that the new request call should be brought into the subsequent service queue of the air base station in time, buffer and start buffer timing are carried out, the call request from the calling party G1 to the called party G2 is processed, and then the subsequent delay tolerant call request is processed according to the first-in first-out queue, so that the overtime service request is cleared from the queue or terminated.
The present invention has been described in the foregoing by way of examples, and it will be understood by those skilled in the art that the present disclosure is not limited to the examples described above, and various changes, modifications and substitutions can be made without departing from the scope of the present invention.

Claims (3)

1. A method for requesting a delay tolerant call service in multi-hop cooperation with an air base station is characterized by comprising the following steps:
step 1: determining initial positions by a plurality of aerial base stations;
step 2: initiator G1To the called party G2Initiating a call service request;
and step 3: the aerial base station processes the call request in the coverage area of a single base station;
and 4, step 4: the air base station processes the call request in the coverage range of the cross base station;
and 5: the air base station group processes the call request with delay tolerance;
step 6: an aerial base station deployment position movement decision;
and 7: the air base station activates a call service link;
and 8: the air base station is adjusted to the position covering the most ground terminals;
and step 9: handling concurrent call service in the moving process of the air base station;
the initiator G1To the called party G2The method for initiating the call service request comprises the following steps:
the initiator G1Sending a call request message, wherein the message format comprises the following elements:
message type, source terminal ID, destination terminal ID, message sequence number SN and time-limited counter T for controlling message bufferH(ii) a The message type is the type of the call request message, the message serial number SN distinguishes the call request service of different times, the source terminal ID and the target terminal ID are the calling party number and the called party number of the call service of the time respectively, and the time-limited counter T for controlling the message cacheHSetting a delay tolerance degree according to a calling request of a calling party; when the initiator sends a message, the initiator also starts a local timer, and the timing time T of the local timer is exceededSConsidering the service termination, TSGreater than TH
The initiator considers that the service request fails when the local timer is overtime or receives a service termination message sent by the air base station;
the method for processing the call request in the coverage area of the single base station by the air base station comprises the following steps:
setting an airborne base station U1Receiving an initiator G1After the call request message is sent, the called party ID is identified from the call request message, which is forwarded to the called party G2Receiving the called party G when in time2After the call response message is replied to, this indicates the calling party G1And the called party G2Are all in the air base station U1Within the coverage area of the base station U in the air1The called party G is called again2Forwards the call response message to the calling party G1Calling party G1To aerial base station U1Sending a call confirmation message, the air base station completes the connection of the calling party G1Aerial base station and called party G2Call service link G of1-U1-G2Establishing;
the method for processing the call request in the coverage area of the cross base station by the air base station comprises the following steps:
the aerial base station U1Receive masterCaller G1After the call request message is sent, the called party ID is identified from the message, and the message is forwarded to the called party G2Not receiving called party G immediately2When a call response message is returned, this indicates the called party G2Off-air base station U1Within the coverage of (c); if the air base station U1With other air base stations, air base stations U, in communication therewith1Forwarding the call request message in the coverage area of all air base stations connected with it, if called party G2Within the connected air base station group, real-time response is made, i.e. calling party G is connected1Aerial base station U1Aerial base station U2And the called party G2Call service link G of1-U1-U2-G2Establishing;
the group of air base stations processing delay tolerant call requests, comprising:
the aerial base station U1Receiving a calling party G1After the call request message is sent, returning to the sequence to execute the step 3 and the step 4, if the call service link can not be immediately established in response to the call request, executing the delay tolerant call request to establish the service link:
step 5-1: if the calling party G1In the air base station U1Within the coverage area of the base station U in the air1The called party G is obtained by inquiring other air base stations through Beidou short messages and ad hoc network links2In the air base station U2But an airborne base station U1And an aerial base station U2The ad hoc network link is disconnected, calling party G1After the transmitted call request message reaches the air base station, the message can not be forwarded to the called party G immediately2Calling party G1The calling party U can not obtain the call response immediately1Caching the call request message;
step 5-2: if the calling party G1In the air base station U1Within the coverage area of the base station U in the air1The called party G is obtained by inquiring other base stations through Beidou short messages and Ad hoc network links2Out of coverage of the air base station group, calling party G1Sending a callAfter the request message arrives at the air base station, the request message can not be forwarded to the called party G immediately2Calling party G1If the call response can not be obtained immediately, the air base station U1Caching the call request message;
step 5-3: if the calling party G1Out of coverage of the airborne base station, calling party G1The call request message reaches an aerial base station U in the form of Beidou short messageaAerial base station UaThen, the called party G is obtained by inquiring other base stations through the Beidou short message and the Ad hoc network link2In the air base station U2Within the coverage area of (2), then the aerial base station UaCaching the call request message;
step 5-4: if the calling party G1Out of coverage of the airborne base station, calling party G1The call request message reaches an aerial base station U in the form of Beidou short messageaAerial base station UaThen, other base stations are inquired by the Beidou short message form and the Ad hoc network link to acquire the called party G2If the mobile station is not in the coverage area of the air base station group, the air base station UaCaching the call request message;
the method for the aerial base station deployment position movement decision comprises the following steps:
step 6-1: for step 5-1, the airborne base station U1According to the source terminal ID and the destination terminal ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And the called party G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station U1The number of base stations in the air in a communication area can be obtained, and the specific processing flow is as follows:
step 6-1-1: if m is 2, and | | (a)1,b1)-(a2,b2) If the | is more than R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) If the | is less than or equal to R +2R, the air base station executes a position moving strategy; m is the number of aerial base stations, R is the reference radius of the aerial base stations to the horizontal coverage range of the ground terminal, v is the unmanned planeThe average moving speed, r is the maximum communication distance between the base stations in the air;
setting two air base stations U1And an aerial base station U2Respectively by position (x)1,y1) And (x)2,y2) Straight line to horizontal position point (x'1,y′1) And (x'2,y′2) And according to formula (2):
min{max{||(x1,y1)-(x′1,y′1)||,||(x2,y2)-(x′2,y′2)||}} (2)
s.t.
Figure FDA0003517757800000041
solving for (x 'in combination with a non-linear constraint based optimization algorithm'1,y′1) And (x'2,y′2) Let d be min { max { | (x)1,y1)-(x′1,y′1)||,||(x2,y2)-(x′2,y′2) If | }, if
Figure FDA0003517757800000042
The air base station stops the service request; if it is
Figure FDA0003517757800000043
The aerial base station will adjust the horizontal position deployment, moving in a straight line to (x'1,y′1) And (x'2,y′2);
Step 6-1-2: if m >2, and | | (a)1,b1)-(a2,b2) R +2R is less than or equal to | |, then covering the calling party G1And the called party G2Aerial base station U1And an aerial base station U2Executing the operation of step 6-1-1;
and wherein if
Figure FDA0003517757800000044
Continuing to execute subsequent operation without stopping the service request; if (a)1,b1)-(a2,b2) If the | | is more than 2R +2R, the air base station stops the service request; if (a)1,b1)-(a2,b2) R +2R is less than or equal to | |
Figure FDA0003517757800000051
Or R +2R < | | (a)1,b1)-(a2,b2) If | | | is less than or equal to 2R +2R, then the aerial base station U1From removing aerial base station U1And an aerial base station U2Selecting one idle base station from other base stations and recording as an air base station U3Three airborne base stations implement a mobility strategy;
three air base stations, namely an air base station U1, an air base station U2 and an air base station U3 are respectively set to be composed of positions (x)1,y1)、(x2,y2) And (x)3,y3) Straight line to horizontal position point (x'1,y′1)、(x′2,y′2) And (x'3,y′3) And according to formula (3):
min{max{||(x1,y1)-(x′1,y1′)||,||(x2,y2)-(x′2,y′2)||,||(x3,y3)-(x′3,y′3)||}} (3)
s.t.
Figure FDA0003517757800000052
solving for (x 'in combination with a non-linear constraint based optimization algorithm'1,y′1)、(x′2,y′2) And (x'3,y′3) Let d be min { max { | (x)1,y1)-(x′1,y′1)||,||(x2,y2)-(x′2,y′2)||,||(x3,y3)-(x′3,y′3) If | }, if
Figure FDA0003517757800000053
The air base station stops the service request; if it is
Figure FDA0003517757800000054
The aerial base station will adjust the horizontal position deployment, moving in a straight line to (x'1,y′1)、(x′2,y′2) And (x'3,y′3);
Step 6-2: for step 5-2, the airborne base station U1According to the source end ID and the destination end ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And the called party G2The horizontal position coordinates are respectively (a)1,b1) And (a)2,b2) Simultaneous air base station U1The number of base stations in the air in a communication area can be obtained, and the specific processing flow is as follows:
step 6-2-1: if (a)1,b1)-(a2,b2) When | | < 2R, then the aerial base station U1Executing the position moving strategy and setting the air base station U1From the horizontal position (x)1,y1) Straight line to horizontal position point (x'1,y′1) And according to equation (4):
min||(x1,y1)-(x′1,y′1)|| (4)
s.t.
Figure FDA0003517757800000061
solving for (x 'in combination with a non-linear constraint based optimization algorithm'1,y1'), let d | | (x)1,y1)-(x′1,y′1) If
Figure FDA0003517757800000062
The aerial base station will adjust the horizontal position deployment, moving in a straight line to (x'1,y′1);
Step 6-2-2: if m is 2, except for the airborne base station U1Another aerial base station as U2Next, it is performed with reference to step 6-1-1;
step 6-2-3: if m is more than 2, the aerial base station U1Distance called party G is scheduled and selected through an ad hoc network link or in a Beidou short message mode2Nearest and idle aerial base station as aerial base station U2Next, it is performed with reference to step 6-1-2;
step 6-3: for step 5-3, the airborne base station UaAccording to the source end ID and the destination end ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And called G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station UaThe number of base stations in the air in a communication area can be obtained, and the processing flow is as follows:
step 6-3-1: first of all by covering the called party G2Aerial base station U2Is performed with reference to step 6-2-1;
step 6-3-2: if m is 2, except for the airborne base station U2Another aerial base station is used as U1Next, it is performed with reference to step 6-1-1;
step 6-3-3: if m is more than 2, the aerial base station UaScheduling selection principle as a distance calling party G through an ad hoc network link or in a form of Beidou short message1Nearest and idle aerial base station as U1Or according to the principle, the aerial base station UaItself as an aerial base station U1Next, it is performed with reference to step 6-1-2;
step 6-4: for step 5-4, the airborne base station UaAccording to the source end ID and the destination end ID in the call request message, the position of the corresponding ground terminal is inquired from the position information base, and the calling party G is recorded1And called G2Has horizontal position coordinates of (a)1,b1) And (a)2,b2) Simultaneous air base station UaThe number of base stations in the air in a communication area can be obtained, and the processing flow is as follows:
step 6-4-1: aerial base station UaThe air base station is scheduled and selected through an ad hoc network link or in a Beidou short message mode, and the principle is that the calling party G is reached1And the called party G2The idle aerial base station with the shortest distance sum or U is selected according to the principleaSelf, the execution is carried out with reference to the step 6-2-1;
step 6-4-2: if m is 2, G is distance from the calling party1The near aerial base station is used as an aerial base station U1From the called party G2The nearest aerial base station is taken as an aerial base station U2Next, with reference to step 6-1-1;
step 6-4-3: if m is more than 2, the aerial base station UaThe air base station is scheduled and selected through an ad hoc network link or in a Beidou short message mode, and the principle is that the calling party G is reached1And the called party G2Two idle aerial base stations with the distance sum being sequentially nearest are used as aerial base stations U1And an aerial base station U2Wherein is distant from the calling party G1The nearest aerial base station is taken as an aerial base station U1From the called party G2The nearest aerial base station is taken as an aerial base station U2Or according to the principle, the aerial base station UaItself as an aerial base station U1Or aerial base station U2And is next performed with reference to step 6-1-2.
2. The method for requesting a delay tolerant call service in multi-hop cooperation with an air base station according to claim 1, wherein the method for adjusting the air base station to the position covering the most ground terminals comprises:
end calling party G1And the called party G2After the inter-call service, the air base station group participating in the movement carries out local optimal coverage on the ground terminals which are not within the coverage radius of other air base stations according to the position distribution of the current ground terminals and the positions of other air base stations, namely, the ground terminals cover the maximum number of ground terminals and move to the estimated position in a straight line, wherein the calculation is carried outThe solution model is performed with reference to step 1.
3. The method for requesting delay tolerant call traffic in multi-hop cooperative air base station according to claim 1, wherein the method for handling concurrent call traffic during the moving process of the air base station comprises:
the air base station processes the concurrent call service in the parking state and executes the processing according to the normal flow of the existing air base station, and if other call service requests are concurrent in the moving process, the supplementary processing method comprises the following steps:
step 9-1: preferentially ensuring real-time request call service: if an instant response is obtained when the call request message is forwarded, which indicates that both sides of the newly added call service are in the coverage range of the base station, the service of the real-time request call is preferentially ensured to be normally carried out, namely the moving direction is not changed, but when the signals of both sides or one side of the newly added real-time request call are about to be lower than a receiving threshold, the movement is stopped to maintain the current position until the service is ended, and the consumed time is counted into the calling party G1To the called party G2The calling party G should be terminated directly by delaying the call request, resulting in a timeout1To the called party G2Then, the service request is carried out in step 7;
step 9-2: if other new call service requests are simultaneously sent and it is difficult to realize that the new request call should be brought into the subsequent service queue of the air base station in real time, the buffer memory is carried out and the buffer memory timing is started, and the calling party G is processed1To the called party G2In between, the subsequent delay tolerant call requests are processed in a first-in-first-out queue, resulting in the overtime request to be cleared or terminated from the queue.
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