CN112929412B - Method, device and storage medium for joint bandwidth allocation and data stream unloading based on MEC single-vehicle single-cell - Google Patents

Method, device and storage medium for joint bandwidth allocation and data stream unloading based on MEC single-vehicle single-cell Download PDF

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CN112929412B
CN112929412B CN202110085210.5A CN202110085210A CN112929412B CN 112929412 B CN112929412 B CN 112929412B CN 202110085210 A CN202110085210 A CN 202110085210A CN 112929412 B CN112929412 B CN 112929412B
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vehicle
edge server
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CN112929412A (en
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张海霞
夏阳
郭帅帅
袁东风
周晓天
薛彤
刘文杰
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Shandong University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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Abstract

The invention relates to a method, a device and a storage medium for joint bandwidth allocation and data flow unloading based on an MEC single-vehicle single-cell, which are characterized in that: when the vehicle leaves the cell and the total data flow is completed in the cell, the lowest time delay t of the total data flow of the vehicle is calculateds(ii) a Because the processed data flow is too large, when the vehicle leaves the cell and the total data flow is not finished in the cell, the edge server solves the problem of buffer area congestion of the edge server and the problem that the data flow of the buffer area of the edge server is not finished when the vehicle is switched between the cells by a method for distributing optimal bandwidth, and the data uploading quantity of the vehicle is maximum. The invention solves the problem of edge server buffer area congestion and the problem that the data stream of the edge server buffer area is not processed completely when the vehicles are switched in the cell. The edge server provides an optimal bandwidth allocation method for the vehicles, the uploaded data volume is reasonably controlled, and the minimum time delay of total vehicle data flow calculation or the maximum uploaded data volume in the cell is realized.

Description

Method, device and storage medium for joint bandwidth allocation and data stream unloading based on MEC single-vehicle single-cell
Technical Field
The invention belongs to the technical field of vehicle networking and edge computing, and relates to a method, equipment and a storage medium for joint bandwidth allocation and data flow unloading based on an MEC single vehicle single cell, which can be used for communication resource allocation and task unloading in vehicle networking edge computing.
Background
The Mobile Edge Computing (MEC) is used as a key technology of 5G, has the characteristics of short distance, high bandwidth, ultralow time delay, geographical position perception and the like, and solves some key technical problems of scenes such as high capacity, low time delay, high reliability and the like in the Internet of vehicles. In the internet of vehicles MEC-based vehicle mobility research, key factors related to task offloading and resource allocation problems include mobility, handover, multi-rate and backhaul links, etc.
When a vehicle user is in a mobility state, handover and task migration between cells are the subject of important research. The continuity of task unloading calculation is guaranteed, the system resources of the edge server are fully utilized, the time delay and the communication cost of a vehicle user are reduced, and the user experience is improved. In the aspect of researching vehicle mobility management, time delay and communication cost are optimized from the aspects of task unloading and resource allocation.
In the aspect of task unloading for researching vehicle mobility, the current research situation of vehicle networking edge computing is to consider the influence of vehicle mobility on task completion delay, energy consumption and total cost of task unloading and resource allocation. A document, Mobility-Aware routing in MEC-Based contextual Wireless Networks, proposes an expected cost analysis model, determines the average total cost of remote task execution by adopting an energy consumption average cost analysis and average task processing delay analysis method, and considers the switching situation of random Mobility of vehicles and the task size possibly occurring in the unloading process. In the second document, considered in a single-cell scene, an effect Mobility-Aware Task Offloading scheme is proposed; in a multi-cell cooperation scene, an unloading scheme based on position is provided. In the two scenarios, the communication and computing resource cost required by task completion and the maximum unloading delay combined optimization are balanced, and the optimal unloading scheme of the task is computed. However, both the first and second documents ignore the problem that too many tasks in a single cell are offloaded, which may result in incomplete tasks in the cell during cell handover, which may result in increased communication backhaul cost and lost tasks during backhaul. The problem of buffer congestion of an edge server is not considered in the current Internet of vehicles edge calculation research, and task loss and performance reduction of an edge server system can be caused by the buffer congestion. In the aspect of calculating the total time delay of the task, the second document mentions that the total time delay of completing the task is the maximum value of the local calculation time delay and the total time delay of unloading the edge server, and the total time delay of completing the task is the minimum only when the local time delay is equal to the total time delay of unloading the edge server. Document three, Joint Task Assignment, Transmission, and Computing Resource Allocation in multilayered Mobile Edge Computing Systems, proposes a multilayered Edge stream system for static users, fully utilizes cloud Edge Computing capability, and alleviates the problem of Edge server buffer congestion. However, the problem of buffer congestion is not completely solved in the document, the optimal bandwidth allocation provided by the edge server is neglected, the uploading task amount is reasonably controlled, and the problem of buffer congestion of the edge server can be avoided.
Disclosure of Invention
Aiming at the problems of edge server buffer congestion caused by excessive task uploading and buffer task incomplete processing during cell switching, the invention provides a method for joint bandwidth allocation and data stream unloading based on an MEC single-vehicle single-cell under a single-vehicle single-cell scene.
The invention also provides a computer device and a storage medium;
the invention researches that in a single-vehicle single-cell scene, a vehicle sends a data stream unloading calculation request to an edge server at a certain position, the edge server is determined to allocate the optimal bandwidth for the vehicle according to the speed, the initial position and the size of the data stream of the vehicle, the limited calculation capacity of a vehicle-mounted unit, the calculation capacity of the edge server, the maximum storage capacity of a buffer area and other factors, the problem of buffer area congestion of the edge server and the problem that the data stream of the buffer area of the edge server is not processed completely when the vehicle cell is switched are solved, and the minimum time delay of the calculation of the total data stream of the vehicle in the cell or the maximum uploading data quantity are realized.
The invention solves the problem of edge server buffer area congestion and the problem that the data stream of the edge server buffer area is not processed completely when the vehicles are switched in the cell. The edge server provides an optimal bandwidth allocation method for the vehicles, the uploaded data volume is reasonably controlled, and the minimum time delay of total vehicle data flow calculation or the maximum uploaded data volume in the cell is realized.
The technical scheme of the invention is as follows:
a method for joint bandwidth allocation and data flow unloading based on an MEC single-vehicle single-cell is characterized in that: when the vehicle leaves the cell and the total data flow is completed in the cell, the lowest time delay t of the total data flow of the vehicle is calculateds(ii) a Because the processed data flow is too large, when the vehicle leaves the cell and the total data flow is not finished in the cell, the edge server solves the problem of buffer area congestion of the edge server and the problem that the data flow of the buffer area of the edge server is not finished when the vehicle is switched between the cells by a method for distributing optimal bandwidth, and the data uploading quantity of the vehicle is maximum.
According to the optimization of the invention, the vehicle i completes the total data stream in the cell, and the lowest total time delay t of the processed vehicle total data stream is calculated according to the method of distributing the optimal bandwidth of the vehicle i by the edge server jsThe method comprises the following steps:
A. according to equation (1), an initial bandwidth b is given0Under the condition of meeting the maximum capacity of the buffer area of the edge server j, the maximum bandwidth b provided by the edge server j for the vehicle i is calculated by adopting a PID algorithmij，bij＝b1The bandwidth b of the vehicle i provided by the edge server j satisfies b ═ b0,b1](ii) a The data volume uploaded by the vehicle i can be reasonably controlled, and the problem of congestion of the buffer area of the edge server j is solved.
Figure BDA0002910551660000031
In the formula (1), N edge servers provide communication, storage and calculation resources for vehicles on a suburb or a highway, M vehicles run in a cell served by an edge server j, j is { 1.·, N }, a certain vehicle i runs at a constant speed in a straight line in the cell served by the edge server j, and i is { 1.·, M }, and a task unloading request is sent to the edge server at a certain position in the cell;
vehicle i is traveling at velocity v in the cell served by edge server jijStraight-line running at a constant speed at a certain initial position aijThe time required for the vehicle i to travel in the cell is t until the vehicle i leaves the cell after starting to transmit the data stream to the edge server j4：
Figure BDA0002910551660000032
When the vehicle leaves the cell, the total data flow is completed in the cell, which means that: t is more than or equal to 0 and less than or equal to t of the vehicle4Completing data flow unloading calculation in a time period;
Pijis the uplink transmission power, h, of vehicle i at edge server jijIs the small-scale fading path loss, N, of vehicle i at edge server j0Is the noise power spectral density of the edge server j receive segment; height of edge server j service is HjRice, horizontal distance to road surface DjRice, diameter of radiation range LCMeter, k is the number of revolutions of the CPU required by each bit, and epsilon refers to the maximum storage capacity of the buffer area;
t1is the moment when the first upload rate equals the computed rate of the edge server, t2Is the moment when the second upload rate equals the calculated rate of the edge server, t3Is the time when the data stream in the buffer of the edge server is processed, tsIs the total time delay for completing the vehicle data flow in the cell, xi is the integral parameter of the uploading rate integral with time, fjIs the number of revolutions per second, R, of the j CPU of the edge serverij(0) Vehicle i upload rate when t is 0;
B. according to the bandwidth b range calculated in the step A, b belongs to [ b ∈ [ ]0,b1]B, under the condition of finishing calculating the data stream of the buffer zone when the vehicle i leaves the cell, bijCalculating the maximum bandwidth b provided by the edge server j for the vehicle i by adopting a PID algorithm to the formula (2)ij，bij＝b2(ii) a The bandwidth b range of the vehicle i provided by the edge server j satisfies b E [ b ∈0,b2],b2∈[b0,b1](ii) a The data flow uploaded by the vehicle i can be reasonably controlled, and the problem that when the vehicle i leaves the cell, the data flow of the buffer area of the edge server is not processed completely is solved.
Figure BDA0002910551660000041
C. And B, calculating a bandwidth B range B epsilon [ B ] meeting the constraint condition according to the step A and the step B0,b2]Considering the factors of the size and initial position of the data stream, the uploading rate when t is 0
Figure BDA0002910551660000042
If vehicle i data stream SiSatisfies SiWhen S is less than or equal to S, the maximum bandwidth b is solved by a PID algorithm adjusting bandwidth method under the condition that no data stream is stored in a j buffer area of the edge serverijSo that the total time delay t of the objective functionsMinimum, i.e. ts＝t1Calculating the total time delay as shown in the formula (3); if vehicle i data stream SiSatisfies SiWhen the bandwidth is larger than S, the bandwidth is adjusted through a PID algorithm, and the maximum bandwidth b is solved under the condition that the data stream stored in the buffer area is not larger than the maximum capacity of the buffer areaijIn the known bandwidth range, the bandwidth method is adjusted through a PID algorithm to solve the optimal bandwidth bijSo that the total time delay t of the objective functionsLowest and satisfies the total delay tsAt t2＜t3≤ts≤t4In the range, formula (3) is as follows:
Figure BDA0002910551660000043
in the formula (3), R (xi) is xi ranging from 0 to tsUpload rate at any time in time, SiIs the size of the data stream that vehicle i needs to compute, in bits. Expanding the uploading rate R (xi) to know, the edge server j provides the optimal bandwidth b of the vehicle iijThe above two problems can be solved and the total task S is calculatediThe lowest delay.
According to the invention, when the vehicle leaves the cell and the total data stream is not completed in the cell, the edge server solves the problem of edge server buffer area congestion and the problem that the data stream of the edge server buffer area is not completed when the vehicle is switched over, and the vehicle data uploading amount is maximum by the method for distributing the optimal bandwidth, and the method comprises the following steps:
D. according to equation (1), an initial bandwidth b is given0Under the condition of meeting the maximum capacity of the buffer area of the edge server j, the maximum bandwidth b provided by the edge server j for the vehicle i is calculated by adopting a PID algorithmij，bij＝b1The bandwidth range of the vehicle i provided at the edge server j satisfies b ═ b0,b1](ii) a The data volume uploaded by the vehicle i can be reasonably controlled, and the problem of congestion of the buffer area of the edge server j is solved.
E. According to the bandwidth b range calculated in the step D, b belongs to [ b ∈ [)0,b1]B, under the condition of finishing calculating the data stream of the buffer zone when the vehicle i leaves the cell, bijCalculating the maximum bandwidth b provided by the edge server j for the vehicle i by adopting a PID algorithm to the formula (2)ij，bij＝b2(ii) a The bandwidth b range of the vehicle i provided by the edge server j satisfies b E [ b ∈0,b2],b2∈[b0,b1](ii) a The data flow uploaded by the vehicle i can be reasonably controlled, and the problem that when the vehicle i leaves the cell, the data flow of the buffer area of the edge server is not processed completely is solved.
F. According to the bandwidth b range which is calculated in the step D and the step E and meets the constraint condition, b belongs to [ b ]0,b2]. Within the known bandwidth range, the optimal bandwidth b is solved by a bandwidth adjusting methodij，bij＝b2According to the time t when the vehicle i runs in the cell of the edge server j, t is t4Solving the maximum data quantity S of the objective functionijAs shown in formula (4):
Figure BDA0002910551660000051
in the formula (4), R (xi) is xi ranging from 0 to tsUpload rate S at any time within timeijIs the amount of data uploaded by vehicle i in cell of edge server j, and the unit is bit. Spreading the uploading rate R (xi) to knowThe edge server j provides the optimal bandwidth b of the vehicle iijThe two problems can be solved, and the vehicle i uploads the maximum data volume S in the cell of the edge server jij。
According to the invention, the following steps are preferably executed before the step A and the step D, and the steps comprise:
a. calculating an initial bandwidth b0: when in use
Figure BDA0002910551660000061
When t is equal to 0, the sum of the values,
Figure BDA0002910551660000062
solving the initial bandwidth b0，b0≤Bj；
a0Refers to the radius of the communication range of the edge server j, i.e.
Figure BDA0002910551660000063
Wherein L isCIs the edge server communication diameter; when in use
Figure BDA0002910551660000064
And when t is 0, Rij(0) The uploading rate of the vehicle i at the nearest position of the edge server j when t is 0;
b. judging the initial position aijAnd
Figure BDA0002910551660000065
in a relation of
Figure BDA0002910551660000066
Then, calculate Rij(0)：
Figure BDA0002910551660000067
Namely at
Figure BDA0002910551660000068
The data uploaded and calculated at the time pointThe sum S of the data streams calculated by the stream-plus-vehicle-mounted terminal is shown as formula (5):
Figure BDA0002910551660000069
c. the sum S of the data streams is compared with the total data stream S of the vehicle iiMaking a comparison, if SiLess than or equal to S, adopting PID algorithm to convert the initial bandwidth b0Substituting equation (6) calculates the difference e:
Figure BDA00029105516600000610
when the difference e is greater than or equal to the set threshold, increasing the initial bandwidth b0The coefficient of increase is c; bandwidth bij＝b0+ce，bij≤BjCalculating
Figure BDA00029105516600000611
To obtain a time point t1，t1The time point when the first uploading rate is equal to the computing rate of the edge server is obtained;
then the new bandwidth b is addedijSubstituting the formula (6), calculating a new difference e, iterating for multiple times until the difference e is smaller than a set threshold value, jumping out of the loop, and obtaining the bandwidth b meeting the minimum total time delay calculated by the total data of the vehicleij(ii) a The data stream has no storage buffer and does not need to be at t2Releasing the computing power after a point in time to process the buffer data stream, t2For the time point when the second upload rate is equal to the calculated rate of the edge server, the lowest total delay is ts＝t1；
If S isiS, enter step A or step D.
According to a preferred embodiment of the invention, an initial bandwidth b is given in step A or step D0And calculating the optimal bandwidth provided by the edge server j for the vehicle i by adopting a PID algorithm: when in use
Figure BDA0002910551660000071
When the step (d) is performed, step (d) is performed
Figure BDA0002910551660000072
If yes, entering the step e;
step d is as follows:
using PID algorithm, the calculation is performed at time t1And t2The memory capacity of the data stream uploading buffer is less than or equal to the maximum buffer memory capacity epsilon:
first, an initial bandwidth b is defined0Substituting into formula
Figure BDA0002910551660000073
To obtain a time point t1And t2；
Then, the initial bandwidth b0Substituting equation (7) to calculate the target value ε and t1And t2Data flow difference value e of the buffer area between:
Figure BDA0002910551660000074
when the difference e is larger than or equal to the set value c, the bandwidth b is adjustedij＝b0+ce，bij≤Bj；
Then the new bandwidth b is addedijSubstituting the formula (7) to recalculate the difference e, iterating for multiple times until the difference e is smaller than the set threshold value, jumping out of the loop, and calculating the optimal bandwidth b meeting the conditionij(ii) a By means of Matlab simulation, considering the influence of different initial positions and vehicle speeds on the bandwidth requirement, the problem of buffer congestion is solved by a bandwidth adjusting method to obtain a simulation diagram, as shown in FIG. 5.
Step e is as follows:
satisfy the requirement of
Figure BDA0002910551660000075
When the condition is met, firstly, the initial bandwidth b0Substituting into formula
Figure BDA0002910551660000076
When derivedIntermediate point t1And t2At the time point t of solution1Is a negative number, take t 10; then, the initial bandwidth b0Substituting equation (8) to calculate the target value ε and t1And t2The data flow difference e of the buffer areas between;
Figure BDA0002910551660000081
when the difference e is larger than or equal to the set value c, the bandwidth b is adjustedij＝b0+ce，bij≤Bj(ii) a Then the new bandwidth b is addedijSubstituting the formula (8) to recalculate the difference e, iterating for multiple times until the difference e is smaller than the set threshold value, jumping out of the loop, and calculating the optimal bandwidth b meeting the conditionij。
Preferably, in step B or E, the optimal bandwidth satisfying time t is calculated by using a PID algorithm to formula (2)3At t2≤t3≤t4Calculating the optimal bandwidth provided by the edge server j for the vehicle i within the range; when in use
Figure BDA0002910551660000082
When the step f is performed, go to step f
Figure BDA0002910551660000083
Entering step g;
step f is as follows:
and the bandwidth is adjusted by adopting a PID algorithm, so that the problem that the data stream of the buffer area is processed when the vehicle leaves the cell is solved:
under the condition of satisfying the above-mentioned solution bandwidth range, firstly, the initial bandwidth b is set0Substituting equation (9) to calculate the time t for finishing processing the buffer3：
Figure BDA0002910551660000084
Then, the target value t is determined4And time t3Difference e, current differenceThe value e is more than or equal to the set value d, and the bandwidth is adjusted
Figure BDA0002910551660000085
Then the new bandwidth is added
Figure BDA0002910551660000086
Substituting equation (9) to calculate the new time t3；
Recalculating the difference e, iterating for multiple times until the difference e is smaller than a set threshold value, jumping out of the loop, and calculating the time t3Bandwidth of
Figure BDA0002910551660000087
To meet the required optimal bandwidth, when time t3＝t4When the vehicle just leaves the cell, the buffer zone is processed, and the bandwidth at the moment
Figure BDA0002910551660000088
Maximum bandwidth to meet the requirements;
step g is as follows:
and the PID algorithm is adopted to adjust the bandwidth, so that the problem of processing the data stream of the buffer area when the vehicle leaves the cell is solved. Under the condition of satisfying the above-mentioned solution bandwidth range, firstly, the initial bandwidth b is set0Substituting equation (10) to calculate the time t for finishing processing the buffer3；
Figure BDA0002910551660000091
Then, the target value t is determined4And time t3When the difference e is larger than or equal to a set value d, adjusting the bandwidth
Figure BDA0002910551660000092
Then the new bandwidth is added
Figure BDA0002910551660000093
Substituting equation (10) to calculate the new time t3；
Recalculating the difference e, multiple iterationsAnd jumping out of the cycle until the difference e is smaller than a set threshold value, and calculating the time t3Bandwidth of
Figure BDA0002910551660000094
To meet the required optimal bandwidth, when time t3＝t4When the vehicle just leaves the cell, the buffer zone is processed, and the bandwidth at the moment
Figure BDA0002910551660000095
To meet the required maximum bandwidth.
A computer arrangement comprising a memory storing a computer program and a processor implementing the steps of a MEC-single cell based joint bandwidth allocation and data flow offloading method when executing the computer program.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the MEC-single-cell based joint bandwidth allocation and data flow offloading method.
The invention has the beneficial effects that:
the invention researches a method for providing optimal bandwidth allocation for vehicles through the edge server under a single-vehicle single-cell scene, reasonably controls the data flow uploaded by the vehicles, and solves the problems of edge server buffer congestion and unprocessed data of the edge server buffer during vehicle cell switching. Two cases are considered depending on the size of the data stream and the limited edge server computing power and the computing power of the vehicle itself. The first case is the case where the total data flow is completed in the cell, where the lowest time delay t of the total data flow of the vehicles can be calculateds. The second case is that the edge server solves the above two problems by allocating the optimal bandwidth and simultaneously maximizes the vehicle data upload amount because the processed data flow is too large and the vehicle does not complete the total data flow when leaving the cell. The invention provides a method for distributing optimal bandwidth by an edge server, which solves the problem of congestion of a buffer area of the edge server, causes data stream loss and reduces the system performance of the edge serverAnd (5) problems are solved. The problem that data streams in a buffer area are not processed completely when a vehicle is subjected to cell switching is solved, so that the cost of return communication is increased and tasks are lost in the return process.
Drawings
FIG. 1 is a schematic diagram of single-vehicle single-cell communication based on MEC in the present invention;
FIG. 2 is a schematic diagram of the calculation of a single vehicle and a single cell based on MEC in the present invention;
FIG. 3(a) is a view showing the driving direction of a vehicle toward an edge server according to the present invention and t1The uploading rate change process greater than 0 influences the situation of data stream stored in the buffer area;
FIG. 3(b) is a view showing that the vehicle of the present invention is driven toward the edge server and t1The uploading rate change process of 0 affects the situation that the data flow is stored in the buffer area;
FIG. 3(c) is a diagram of a vehicle driving off an edge server and t of the present invention1The uploading rate change process of 0 affects the situation that the data flow is stored in the buffer area;
FIG. 4(a) shows the bandwidth allocation method of the present invention having calculated t1～t2The data flow condition of the buffer area with the shaded area is shown schematically;
FIG. 4(b) is the bandwidth allocation method of the present invention, which has been calculated from 0 to t2A schematic diagram of the data flow condition of the buffer area with the shaded area;
FIG. 4(c) is the bandwidth allocation method of the present invention, which has been calculated from 0 to t2A second schematic diagram of the data flow condition of the buffer area in the shaded area;
FIG. 5 is a schematic diagram of the maximum bandwidth that meets the capacity of the buffer calculated by the PID algorithm in the present invention;
FIG. 6(a) is a schematic diagram showing the effect of a vehicle speed of 20m/s and different initial positions on bandwidth allocation in the present invention;
FIG. 6(b) is a schematic diagram showing the effect of a vehicle speed of 25m/s and different initial positions on bandwidth allocation in the present invention.
Detailed Description
The invention is further defined in the following, but not limited to, the figures and examples in the description.
Example 1
A method for joint bandwidth allocation and data flow unloading based on an MEC single-vehicle single-cell is characterized in that: when the vehicle leaves the cell and the total data flow is completed in the cell, the lowest time delay t of the total data flow of the vehicle is calculateds(ii) a Because the processed data flow is too large, when the vehicle leaves the cell and the total data flow is not finished in the cell, the edge server solves the problem of buffer area congestion of the edge server and the problem that the data flow of the buffer area of the edge server is not finished when the vehicle is switched between the cells by a method for distributing optimal bandwidth, and the data uploading quantity of the vehicle is maximum.
Example 2
The method for joint bandwidth allocation and data flow offloading based on MEC single-vehicle single-cell in embodiment 1 is characterized in that:
the vehicle i completes the total data stream in the cell, and the lowest total time delay t for processing the total data stream of the vehicle is calculated according to the method for distributing the optimal bandwidth of the vehicle i by the edge server jsThe method comprises the following steps:
A. according to equation (1), an initial bandwidth b is given0Under the condition of meeting the maximum capacity of the buffer area of the edge server j, the maximum bandwidth b provided by the edge server j for the vehicle i is calculated by adopting a PID algorithmij，bij＝b1The bandwidth b of the vehicle i provided by the edge server j satisfies b ═ b0,b1](ii) a The data volume uploaded by the vehicle i can be reasonably controlled, and the problem of congestion of the buffer area of the edge server j is solved.
Figure BDA0002910551660000111
In the formula (1), N edge servers provide communication, storage and calculation resources for vehicles on a suburb or a highway, M vehicles run in a cell served by an edge server j, j is { 1.·, N }, a certain vehicle i runs at a constant speed in a straight line in the cell served by the edge server j, and i is { 1.·, M }, and a task unloading request is sent to the edge server at a certain position in the cell;
vehicle i is traveling at speed within the cell served by edge server jDegree vijStraight-line running at a constant speed at a certain initial position aijThe time required for the vehicle i to travel in the cell is t until the vehicle i leaves the cell after starting to transmit the data stream to the edge server j4：
Figure BDA0002910551660000112
When the vehicle leaves the cell, the total data flow is completed in the cell, which means that: t is more than or equal to 0 and less than or equal to t of the vehicle4Completing data flow unloading calculation in a time period;
Pijis the uplink transmission power, h, of vehicle i at edge server jijIs the small-scale fading path loss, N, of vehicle i at edge server j0Is the noise power spectral density of the edge server j receive segment; height of edge server j service is HjRice, horizontal distance to road surface DjRice, diameter of radiation range LCMeter, as shown in fig. 1, k is the number of revolutions per bit of the CPU required, and epsilon refers to the maximum storage capacity of the buffer;
as in FIG. 3(a), t1Is the moment when the first upload rate equals the computed rate of the edge server, t2Is the moment when the second upload rate equals the calculated rate of the edge server, t3Is the time when the data stream in the buffer of the edge server is processed, tsIs the total time delay for completing the vehicle data flow in the cell, xi is the integral parameter of the uploading rate integral with time, fjIs the number of revolutions per second, R, of the j CPU of the edge serverij(0) Vehicle i upload rate when t is 0;
B. according to the bandwidth b range calculated in the step A, b belongs to [ b ∈ [ ]0,b1]B, under the condition of finishing calculating the data stream of the buffer zone when the vehicle i leaves the cell, bijCalculating the maximum bandwidth b provided by the edge server j for the vehicle i by adopting a PID algorithm to the formula (2)ij，bij＝b2(ii) a The bandwidth b range of the vehicle i provided by the edge server j satisfies b E [ b ∈0,b2],b2∈[b0,b1](ii) a The data flow uploaded by the vehicle i can be reasonably controlled, and the problem that the data flow of the buffer area of the edge server is not processed when the vehicle i leaves the cell is solvedAnd (4) solving the problem.
Figure BDA0002910551660000121
C. And B, calculating a bandwidth B range B epsilon [ B ] meeting the constraint condition according to the step A and the step B0,b2]Considering the factors such as the size and initial position of the data stream, it can be seen from fig. 3(a) and equation (5) that the upload rate is 0 when t is equal to t
Figure BDA0002910551660000122
As shown in fig. 2, when the first byte arrives at the edge server, it is assumed that the edge server can calculate after receiving the first byte, and therefore, the upload start time is equal to the calculation start time. Because the calculated result is generally small, the return delay is approximately ignored, the queue delay of the buffer area is considered, and the data stream of the buffer area is processed when the vehicle leaves the cell, the total delay of the edge server for processing the data stream is equal to the uploading delay of the vehicle in the cell. If vehicle i data stream SiSatisfies SiWhen S is less than or equal to S, the maximum bandwidth b is solved by a PID algorithm adjusting bandwidth method under the condition that no data stream is stored in a j buffer area of the edge serverijSo that the total time delay t of the objective functionsMinimum, i.e. ts＝t1Calculating the total time delay as shown in the formula (3); if vehicle i data stream SiSatisfies SiWhen the bandwidth is larger than S, the bandwidth is adjusted through a PID algorithm, and the maximum bandwidth b is solved under the condition that the data stream stored in the buffer area is not larger than the maximum capacity of the buffer areaijIn the known bandwidth range, the bandwidth method is adjusted through a PID algorithm to solve the optimal bandwidth bijSo that the total time delay t of the objective functionsLowest and satisfies the total delay tsAt t2＜t3≤ts≤t4In the range, formula (3) is as follows:
Figure BDA0002910551660000131
in the formula (3), the reaction mixture is,r (xi) is xi from 0 to tsUpload rate at any time in time, SiIs the size of the data stream that vehicle i needs to compute, in bits. Expanding the uploading rate R (xi) to know, the edge server j provides the optimal bandwidth b of the vehicle iijThe above two problems can be solved and the total task S is calculatediThe lowest delay.
The reasoning process of equation (1) is as follows:
and the edge server j solves the problem of buffer congestion through a bandwidth allocation method, and when the uploading rate is greater than the calculation rate of the edge server, unprocessed data in unit time are stored in the buffer. There are three cases where the uploading rate change process affects the buffer storage data stream, as shown in fig. 3(a) to 3(c), where the edge server j calculates the rate as:
Figure BDA0002910551660000132
t in FIG. 3(a)1And t2The upload rate at that time is equal to the edge server computation rate, as in fig. 3(b) and 3(c)
Figure BDA0002910551660000133
That is, when t is 0, the uploading rate is greater than the calculation rate, so that the unprocessed data is stored in the buffer area when t is 0, that is, t is t 10. The area of the shaded part in the calculation graph is the storage capacity of the buffer area, and the storage capacity of the buffer area is ensured to be not more than the maximum storage capacity epsilon of the buffer area. t is t4Is that the vehicle i is from a certain initial position a in the edge server j cellijThe time required to start sending a data stream until leaving the cell, wherein,
Figure BDA0002910551660000134
Figure BDA0002910551660000135
k is the number of revolutions per bit required by the CPU.
For the uplink transmission rate R in the above formulaijAnd xi, the edge server j can avoid the problem of buffer congestion through bandwidth allocation, as shown in formula (1).
The reasoning process of equation (2) is as follows:
the edge server j provides bandwidth allocation to solve the problem that the task is not finished when the cell is switched. As shown in fig. 4(a) to 4(c), the edge server j causes t to be a bandwidth allocation method2And t3The area of the shaded portion in between is equal to t1And t2The shaded area therebetween, wherein, fig. 4(a) is the bandwidth allocation method having calculated t1～t2The data flow condition of the buffer area with the shaded area is shown schematically; t in FIGS. 4(b) and 4(c)1＝0、t3The time is the time when the data in the buffer area is processed and is not processed, as long as t is satisfied3≤t4This condition solves the problem of unprocessed data streams in the buffer of the edge server j when the vehicle i leaves the cell. When t is3＝t4And meanwhile, the edge server j allocates the maximum bandwidth for the vehicle i, so that the problems of increase of return communication cost and task loss when the vehicle i runs to the next cell are solved.
Figure BDA0002910551660000141
Simplifying to obtain:
Figure BDA0002910551660000142
for the uplink transmission rate R in the above formulaijAnd xi, the problem that the data stream of the buffer area of the edge server j is not processed completely when the vehicle i leaves the cell is solved by the edge server j through a bandwidth allocation method, as shown in a formula (2).
Example 3
The method for joint bandwidth allocation and data flow offloading based on MEC single-vehicle single-cell in embodiment 1 is characterized in that:
when a vehicle leaves a cell and the total data flow is not completed in the cell, the edge server solves the problem of edge server buffer area congestion and the problem that the data flow of the edge server buffer area is not processed when the vehicle is switched between the cells by a method for distributing optimal bandwidth, and the vehicle data uploading quantity is maximum, and the method comprises the following steps:
D. according to equation (1), an initial bandwidth b is given0Under the condition of meeting the maximum capacity of the buffer area of the edge server j, the maximum bandwidth b provided by the edge server j for the vehicle i is calculated by adopting a PID algorithmij，bij＝b1The bandwidth range of the vehicle i provided at the edge server j satisfies b ═ b0,b1](ii) a The data volume uploaded by the vehicle i can be reasonably controlled, and the problem of congestion of the buffer area of the edge server j is solved.
E. According to the bandwidth b range calculated in the step D, b belongs to [ b ∈ [)0,b1]B, under the condition of finishing calculating the data stream of the buffer zone when the vehicle i leaves the cell, bijCalculating the maximum bandwidth b provided by the edge server j for the vehicle i by adopting a PID algorithm to the formula (2)ij，bij＝b2(ii) a The bandwidth b range of the vehicle i provided by the edge server j satisfies b E [ b ∈0,b2],b2∈[b0,b1](ii) a The data flow uploaded by the vehicle i can be reasonably controlled, and the problem that when the vehicle i leaves the cell, the data flow of the buffer area of the edge server is not processed completely is solved.
F. According to the bandwidth b range which is calculated in the step D and the step E and meets the constraint condition, b belongs to [ b ]0,b2]. Within the known bandwidth range, the optimal bandwidth b is solved by a bandwidth adjusting methodij，bij＝b2According to the time t when the vehicle i runs in the cell of the edge server j, t is t4Solving the maximum data quantity S of the objective functionijAs shown in formula (4):
Figure BDA0002910551660000151
in the formula (4), R (xi) is xi ranging from 0 to tsUpload rate S at any time within timeijIs the amount of data uploaded by vehicle i in cell of edge server j, and the unit is bit. Expanding the uploading rate R (xi) to know, the edge server j provides the optimal bandwidth b of the vehicle iijThe two problems can be solved, and the vehicle i uploads the maximum data volume S in the cell of the edge server jij。
Example 4
The method for joint bandwidth allocation and data flow unloading based on the MEC single-vehicle single-cell in the embodiment 2 or 3 is characterized in that:
the following steps are executed before the step A and the step D, and the steps comprise:
a. calculating an initial bandwidth b0: when in use
Figure BDA0002910551660000161
When t is equal to 0, the sum of the values,
Figure BDA0002910551660000162
solving the initial bandwidth b0，b0≤Bj；
a0Refers to the radius of the communication range of the edge server j, i.e.
Figure BDA0002910551660000163
Wherein L isCIs the edge server communication diameter; when in use
Figure BDA0002910551660000164
And when t is 0, Rij(0) The uploading rate of the vehicle i at the nearest position of the edge server j when t is 0;
b. judging the initial position aijAnd
Figure BDA0002910551660000165
in a relation of
Figure BDA0002910551660000166
Then, calculate Rij(0)：
Figure BDA0002910551660000167
Namely at
Figure BDA0002910551660000168
Then, the sum S of the data stream uploaded and calculated at the time point and the data stream calculated by the vehicle-mounted terminal is as shown in formula (5):
Figure BDA0002910551660000169
c. the sum S of the data streams is compared with the total data stream S of the vehicle iiMaking a comparison, if SiLess than or equal to S, adopting PID algorithm to convert the initial bandwidth b0Substituting equation (6) calculates the difference e:
Figure BDA00029105516600001610
when the difference e is greater than or equal to the set threshold, increasing the initial bandwidth b0The coefficient of increase is c; bandwidth bij＝b0+ce，bij≤BjCalculating
Figure BDA00029105516600001611
To obtain a time point t1，t1The time point when the first uploading rate is equal to the computing rate of the edge server is obtained;
then the new bandwidth b is addedijSubstituting the formula (6), calculating a new difference e, iterating for multiple times until the difference e is smaller than a set threshold value, jumping out of the loop, and obtaining the bandwidth b meeting the minimum total time delay calculated by the total data of the vehicleij(ii) a The data stream has no storage buffer and does not need to be at t2Releasing the computing power after a point in time to process the buffer data stream, t2For the second upload rate being equal to the computed rate of the edge serverThe time point is thus t as the lowest total delays＝t1；
If S isiS, enter step A or step D.
Example 5
The method for joint bandwidth allocation and data flow unloading based on the MEC single-vehicle single-cell in the embodiment 2 or 3 is characterized in that:
in step A or step D, an initial bandwidth b is given0And calculating the optimal bandwidth provided by the edge server j for the vehicle i by adopting a PID algorithm: when in use
Figure BDA0002910551660000171
When the step (d) is performed, step (d) is performed
Figure BDA0002910551660000172
If yes, entering the step e;
step d is as follows:
using PID algorithm, the calculation is performed at time t1And t2The memory capacity of the data stream uploading buffer is less than or equal to the maximum buffer memory capacity epsilon:
first, an initial bandwidth b is defined0Substituting into formula
Figure BDA0002910551660000173
To obtain a time point t1And t2；
Then, the initial bandwidth b0Substituting equation (7) to calculate the target value ε and t1And t2Data flow difference value e of the buffer area between:
Figure BDA0002910551660000174
when the difference e is larger than or equal to the set value c, the bandwidth b is adjustedij＝b0+ce，bij≤Bj；
Then the new bandwidth b is addedijSubstituting the formula (7) to recalculate the difference e, iterating for a plurality of times until the difference e is smaller than the set threshold value, jumping out of the loop,calculating the optimal bandwidth b meeting the conditionij(ii) a By means of Matlab simulation, considering the influence of different initial positions and vehicle speeds on the bandwidth requirement, the problem of buffer congestion is solved by a bandwidth adjusting method to obtain a simulation diagram, as shown in FIG. 5.
Step e is as follows:
satisfy the requirement of
Figure BDA0002910551660000175
When the condition is met, firstly, the initial bandwidth b0Substituting into formula
Figure BDA0002910551660000176
To obtain a time point t1And t2At the time point t of solution1Is a negative number, take t 10; then, the initial bandwidth b0Substituting equation (8) to calculate the target value ε and t1And t2The data flow difference e of the buffer areas between;
Figure BDA0002910551660000181
when the difference e is larger than or equal to the set value c, the bandwidth b is adjustedij＝b0+ce，bij≤Bj(ii) a Then the new bandwidth b is addedijSubstituting the formula (8) to recalculate the difference e, iterating for multiple times until the difference e is smaller than the set threshold value, jumping out of the loop, and calculating the optimal bandwidth b meeting the conditionij. By means of Matlab simulation, considering the influence of different initial positions and vehicle speeds on the bandwidth requirement, the problem of buffer congestion is solved by a bandwidth adjusting method to obtain a simulation diagram, as shown in FIG. 5.
Example 6
The method for joint bandwidth allocation and data flow unloading based on the MEC single-vehicle single-cell in the embodiment 2 or 3 is characterized in that:
in the step B or E, the optimal bandwidth satisfying time t is calculated by adopting a PID algorithm to the formula (2)3At t2≤t3≤t4In-range computing edge server j provides for vehicle iThe optimal bandwidth of (a); when in use
Figure BDA0002910551660000182
When the step f is performed, go to step f
Figure BDA0002910551660000183
Entering step g;
step f is as follows:
and the bandwidth is adjusted by adopting a PID algorithm, so that the problem that the data stream of the buffer area is processed when the vehicle leaves the cell is solved:
under the condition of satisfying the above-mentioned solution bandwidth range, firstly, the initial bandwidth b is set0Substituting equation (9) to calculate the time t for finishing processing the buffer3：
Figure BDA0002910551660000184
Then, the target value t is determined4And time t3When the difference e is larger than or equal to a set value d, adjusting the bandwidth
Figure BDA0002910551660000185
Then the new bandwidth is added
Figure BDA0002910551660000186
Substituting equation (9) to calculate the new time t3；
Recalculating the difference e, iterating for multiple times until the difference e is smaller than a set threshold value, jumping out of the loop, and calculating the time t3Bandwidth of
Figure BDA0002910551660000187
To meet the required optimal bandwidth, when time t3＝t4When the vehicle just leaves the cell, the buffer zone is processed, and the bandwidth at the moment
Figure BDA0002910551660000191
Maximum bandwidth to meet the requirements; bandwidth allocation by Matlab simulation considering different initial positions and vehicle speedsThe simulation graph is obtained by solving the problem that the buffer data is not processed when the vehicle leaves the cell through the bandwidth allocation method, as shown in fig. 6(a) and 6 (b). As can be seen from the simulation diagrams of fig. 6(a) and 6(b), the bandwidth allocation is independent of the speed size, and is only related to the initial position.
Step g is as follows:
and the PID algorithm is adopted to adjust the bandwidth, so that the problem of processing the data stream of the buffer area when the vehicle leaves the cell is solved. Under the condition of satisfying the above-mentioned solution bandwidth range, firstly, the initial bandwidth b is set0Substituting equation (10) to calculate the time t for finishing processing the buffer3；
Figure BDA0002910551660000192
Then, the target value t is determined4And time t3When the difference e is larger than or equal to a set value d, adjusting the bandwidth
Figure BDA0002910551660000193
Then the new bandwidth is added
Figure BDA0002910551660000194
Substituting equation (10) to calculate the new time t3；
Recalculating the difference e, iterating for multiple times until the difference e is smaller than a set threshold value, jumping out of the loop, and calculating the time t3Bandwidth of
Figure BDA0002910551660000195
To meet the required optimal bandwidth, when time t3＝t4When the vehicle just leaves the cell, the buffer zone is processed, and the bandwidth at the moment
Figure BDA0002910551660000196
To meet the required maximum bandwidth. By Matlab simulation, considering the influence of different initial positions and vehicle speeds on bandwidth allocation, a simulation diagram is obtained by solving the problem that data in a buffer area is not processed when a vehicle leaves a cell by a bandwidth allocation method, as shown in FIG. 6(a) And FIG. 6 (b).
Example 7
A computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method for joint bandwidth allocation and data stream offloading based on MEC single-vehicle single-cell according to any of embodiments 1-6 when executing the computer program.
Example 8
A computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of any of the MEC single car cell based joint bandwidth allocation and data stream offloading methods of embodiments 1-6.

Claims (3)

1. A method for joint bandwidth allocation and data flow unloading based on an MEC single-vehicle single-cell is characterized by comprising the following steps: when the vehicle leaves the cell and the total data flow is completed in the cell, the lowest time delay t of the total data flow of the vehicle is calculateds(ii) a When a vehicle leaves a cell and the total data stream is not completed in the cell, the edge server solves the problem of congestion of a buffer area of the edge server and the problem that the data stream of the buffer area of the edge server is not processed when the vehicle is switched between the cells by a method of distributing optimal bandwidth, and the uploading amount of vehicle data is maximum;
the vehicle i completes the total data stream in the cell, and the lowest total time delay t for processing the total data stream of the vehicle is calculated according to the method for distributing the optimal bandwidth of the vehicle i by the edge server jsThe method comprises the following steps:
A. according to equation (1), an initial bandwidth b is given0Under the condition of meeting the maximum capacity of the buffer area of the edge server j, the maximum bandwidth b provided by the edge server j for the vehicle i is calculated by adopting a PID algorithmij，bij＝b1The bandwidth b of the vehicle i provided by the edge server j satisfies b ═ b0,b1]；
Figure FDA0003339611950000011
In the formula (1), N edge servers provide communication, storage and calculation resources for vehicles on a suburb or a highway, M vehicles run in a cell served by an edge server j, j is { 1.·, N }, a certain vehicle i runs at a constant speed in a straight line in the cell served by the edge server j, and i is { 1.·, M }, and a task unloading request is sent to the edge server at a certain position in the cell;
vehicle i is traveling at velocity v in the cell served by edge server jijStraight-line running at a constant speed at a certain initial position aijThe time required for the vehicle i to travel in the cell is t until the vehicle i leaves the cell after starting to transmit the data stream to the edge server j4：
Figure FDA0003339611950000012
When the vehicle leaves the cell, the total data flow is completed in the cell, which means that: t is more than or equal to 0 and less than or equal to t of the vehicle4Completing data flow unloading calculation in a time period;
Pijis the uplink transmission power, h, of vehicle i at edge server jijIs the small-scale fading path loss, N, of vehicle i at edge server j0Is the noise power spectral density of the edge server j receive segment; height of edge server j service is HjRice, horizontal distance to road surface DjRice, diameter of radiation range LCMeter, k is the number of revolutions of the CPU required by each bit, and epsilon refers to the maximum storage capacity of the buffer area;
t1is the moment when the first upload rate equals the computed rate of the edge server, t2Is the moment when the second upload rate equals the calculated rate of the edge server, t3Is the time when the data stream in the buffer of the edge server is processed, tsIs the total time delay for completing the vehicle data flow in the cell, xi is the integral parameter of the uploading rate integral with time, fjIs the number of revolutions per second, R, of the j CPU of the edge serverij(0) Vehicle i upload rate when t is 0;
B. according to the bandwidth b range calculated in the step A, b belongs to [ b ∈ [ ]0,b1]When the vehicle i leaves the cell, the buffer zone is calculatedUnder the condition of data flow, bijCalculating the maximum bandwidth b provided by the edge server j for the vehicle i by adopting a PID algorithm to the formula (2)ij，bij＝b2(ii) a The bandwidth b range of the vehicle i provided by the edge server j satisfies b E [ b ∈0,b2],b2∈[b0,b1]；
Figure FDA0003339611950000021
C. And B, calculating a bandwidth B range B epsilon [ B ] meeting the constraint condition according to the step A and the step B0,b2]If vehicle i data stream SiSatisfies SiWhen S is less than or equal to S, the maximum bandwidth b is solved by a PID algorithm adjusting bandwidth method under the condition that no data stream is stored in a j buffer area of the edge serverijSo that the total time delay t of the objective functionsMinimum, i.e. ts＝t1Calculating the total time delay as shown in the formula (3); if vehicle i data stream SiSatisfies Si>S, adjusting the bandwidth through a PID algorithm, and solving the maximum bandwidth b under the condition that the data stream stored in the buffer area is not greater than the maximum capacity of the buffer areaijIn the known bandwidth range, the bandwidth method is adjusted through a PID algorithm to solve the optimal bandwidth bijSo that the total time delay t of the objective functionsLowest and satisfies the total delay tsAt t2<t3≤ts≤t4In the range, formula (3) is as follows:
Figure FDA0003339611950000031
in the formula (3), R (xi) is xi ranging from 0 to tsUpload rate at any time in time, SiThe size of the data stream to be calculated by the vehicle i is calculated, and the unit is a bit;
when a vehicle leaves a cell and the total data flow is not completed in the cell, the edge server solves the problem of edge server buffer area congestion and the problem that the data flow of the edge server buffer area is not processed when the vehicle is switched between the cells by a method for distributing optimal bandwidth, and the vehicle data uploading quantity is maximum, and the method comprises the following steps:
D. according to equation (1), an initial bandwidth b is given0Under the condition of meeting the maximum capacity of the buffer area of the edge server j, the maximum bandwidth b provided by the edge server j for the vehicle i is calculated by adopting a PID algorithmij，bij＝b1The bandwidth range of the vehicle i provided at the edge server j satisfies b ═ b0,b1]；
E. According to the bandwidth b range calculated in the step D, b belongs to [ b ∈ [)0,b1]B, under the condition of finishing calculating the data stream of the buffer zone when the vehicle i leaves the cell, bijCalculating the maximum bandwidth b provided by the edge server j for the vehicle i by adopting a PID algorithm to the formula (2)ij，bij＝b2(ii) a The bandwidth b range of the vehicle i provided by the edge server j satisfies b E [ b ∈0,b2],b2∈[b0,b1]；
F. According to the bandwidth b range which is calculated in the step D and the step E and meets the constraint condition, b belongs to [ b ]0,b2]In the known bandwidth range, the optimal bandwidth b is solved by a bandwidth adjusting methodij，bij＝b2According to the time t when the vehicle i runs in the cell of the edge server j, t is t4Solving the maximum data quantity S of the objective functionijAs shown in formula (4):
Figure FDA0003339611950000032
in the formula (4), R (xi) is xi ranging from 0 to tsUpload rate S at any time within timeijThe data volume uploaded by the vehicle i in the cell of the edge server j is represented by bits;
the following steps are executed before the step A and the step D, and the steps comprise:
a. calculating an initial bandwidth b0: when in use
Figure FDA0003339611950000041
When t is equal to 0, the sum of the values,
Figure FDA0003339611950000042
solving the initial bandwidth b0，b0≤Bj；
a0Refers to the radius of the communication range of the edge server j, i.e.
Figure FDA0003339611950000043
Wherein L isCIs the edge server communication diameter; when in use
Figure FDA0003339611950000044
And when t is 0, Rij(0) The uploading rate of the vehicle i at the nearest position of the edge server j when t is 0;
b. judging the initial position aijAnd
Figure FDA0003339611950000045
in a relation of
Figure FDA0003339611950000046
Then, calculate Rij(0)：
Figure FDA0003339611950000047
Namely at
Figure FDA0003339611950000048
Then, the sum S of the data stream uploaded and calculated at the time point and the data stream calculated by the vehicle-mounted terminal is as shown in formula (5):
Figure FDA0003339611950000049
c、the sum S of the data streams is compared with the total data stream S of the vehicle iiMaking a comparison, if SiLess than or equal to S, adopting PID algorithm to convert the initial bandwidth b0Substituting equation (6) calculates the difference e:
Figure FDA00033396119500000410
when the difference e is greater than or equal to the set threshold, increasing the initial bandwidth b0The coefficient of increase is c; bandwidth bij＝b0+ce，bij≤BjCalculating
Figure FDA0003339611950000051
To obtain a time point t1，t1The time point when the first uploading rate is equal to the computing rate of the edge server is obtained;
then the new bandwidth b is addedijSubstituting the formula (6), calculating a new difference e, iterating for multiple times until the difference e is smaller than a set threshold value, jumping out of the loop, and obtaining the bandwidth b meeting the minimum total time delay calculated by the total data of the vehicleij(ii) a The data stream has no storage buffer and does not need to be at t2Releasing the computing power after a point in time to process the buffer data stream, t2For the time point when the second upload rate is equal to the calculated rate of the edge server, the lowest total delay is ts＝t1；
If S isi>S, entering the step A or the step D;
in step A or step D, an initial bandwidth b is given0And calculating the optimal bandwidth provided by the edge server j for the vehicle i by adopting a PID algorithm: when in use
Figure FDA0003339611950000052
When the step (d) is performed, step (d) is performed
Figure FDA0003339611950000053
If yes, entering the step e;
step d is as follows:
using PID algorithm, the calculation is performed at time t1And t2The memory capacity of the data stream uploading buffer is less than or equal to the maximum buffer memory capacity epsilon:
first, an initial bandwidth b is defined0Substituting into formula
Figure FDA0003339611950000054
To obtain a time point t1And t2；
Then, the initial bandwidth b0Substituting equation (7) to calculate the target value ε and t1And t2Data flow difference value e of the buffer area between:
Figure FDA0003339611950000055
when the difference e is larger than or equal to the set value c, the bandwidth b is adjustedij＝b0+ce，bij≤Bj；
Then the new bandwidth b is addedijSubstituting the formula (7) to recalculate the difference e, iterating for multiple times until the difference e is smaller than the set threshold value, jumping out of the loop, and calculating the optimal bandwidth b meeting the conditionij；
Step e is as follows:
satisfy the requirement of
Figure FDA0003339611950000056
When the condition is met, firstly, the initial bandwidth b0Substituting into formula
Figure FDA0003339611950000057
To obtain a time point t1And t2At the time point t of solution1Is a negative number, take t10; then, the initial bandwidth b0Substituting equation (8) to calculate the target value ε and t1And t2The data flow difference e of the buffer areas between;
Figure FDA0003339611950000061
when the difference e is larger than or equal to the set value c, the bandwidth b is adjustedij＝b0+ce，bij≤Bj(ii) a Then the new bandwidth b is addedijSubstituting the formula (8) to recalculate the difference e, iterating for multiple times until the difference e is smaller than the set threshold value, jumping out of the loop, and calculating the optimal bandwidth b meeting the conditionij；
In the step B or E, the optimal bandwidth satisfying time t is calculated by adopting a PID algorithm to the formula (2)3At t2≤t3≤t4Calculating the optimal bandwidth provided by the edge server j for the vehicle i within the range; when in use
Figure FDA0003339611950000062
When the step f is performed, go to step f
Figure FDA0003339611950000063
Entering step g;
step f is as follows:
and the bandwidth is adjusted by adopting a PID algorithm, so that the problem that the data stream of the buffer area is processed when the vehicle leaves the cell is solved:
first, an initial bandwidth b is defined0Substituting equation (9) to calculate the time t for finishing processing the buffer3：
Figure FDA0003339611950000064
Then, the target value t is determined4And time t3When the difference e is larger than or equal to a set value d, adjusting the bandwidth
Figure FDA0003339611950000065
bij≤BjThen the new bandwidth is added
Figure FDA0003339611950000066
Substituting equation (9) to calculate the new time t3；
Recalculating the difference e, iterating for multiple times until the difference e is smaller than a set threshold value, jumping out of the loop, and calculating the time t3Bandwidth of
Figure FDA0003339611950000067
To meet the required optimal bandwidth, when time t3＝t4When the vehicle just leaves the cell, the buffer zone is processed, and the bandwidth at the moment
Figure FDA0003339611950000068
Maximum bandwidth to meet the requirements;
step g is as follows:
first, an initial bandwidth b is defined0Substituting equation (10) to calculate the time t for finishing processing the buffer3；
Figure FDA0003339611950000071
Then, the target value t is determined4And time t3When the difference e is larger than or equal to a set value d, adjusting the bandwidth
Figure FDA0003339611950000072
bij≤BjThen the new bandwidth is added
Figure FDA0003339611950000073
Substituting equation (10) to calculate the new time t3；
Recalculating the difference e, iterating for multiple times until the difference e is smaller than a set threshold value, jumping out of the loop, and calculating the time t3Bandwidth of
Figure FDA0003339611950000074
To meet the required optimal bandwidth, when time t3＝t4When the vehicle just leaves the cell, the buffer zone is processed, and the bandwidth at the moment
Figure FDA0003339611950000075
To meet the required maximum bandwidth.
2. A computer arrangement comprising a memory and a processor, the memory storing a computer program, wherein the processor when executing the computer program performs the steps of the MEC-single cell based joint bandwidth allocation and data flow offloading method of claim 1.
3. A computer readable storage medium having stored thereon a computer program, wherein the computer program when executed by a processor implements the steps of the MEC-single cell based joint bandwidth allocation and data flow offloading method of claim 1.
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