CN110012039B - ADMM-based task allocation and power control method in Internet of vehicles - Google Patents
ADMM-based task allocation and power control method in Internet of vehicles Download PDFInfo
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Abstract
The invention relates to a mobile edge calculation scheme in a car networking scene, which optimizes the problems of calculation task allocation and transmission power control of user equipment in a car on the premise of meeting the time delay requirement. The energy loss of the equipment under the weighting of the calculation task allocation rate is taken as an objective function, a data transmission model of the user equipment and the edge calculation node is obtained by using a queuing theory method, and the optimization problem is solved through the iteration of nonlinear fractional optimization and an alternative direction multiplier method. In each round of circulation, the outer layer circulation solves the problem of nonlinear fractional programming, the inner layer circulation updates the initial value and the variable until the iteration result meets the set threshold, the task quantity distribution ratio of each user equipment is determined, and the minimized energy consumption is obtained. The technical scheme provided by the invention can effectively reduce the energy consumption of the user equipment, meet the requirement of time delay and improve the computing capacity of the whole network.
Description
Technical Field
The invention relates to a mobile edge computing scheme in the field of wireless communication, in particular to a task allocation and power control method based on ADMM in the Internet of vehicles.
Background
As a typical application of the internet of things in the field of transportation, the internet of vehicles enables ubiquitous information sharing among vehicles with little or no human intervention, which is important for implementing future intelligent transportation systems. On one hand, the Internet of vehicles can stimulate the rapid development of a series of application programs with strict timeliness requirements in the fields of road safety, travel assistance, automatic driving and the like; on the other hand, rich multimedia internet of things applications such as augmented reality, streaming video, and online games are rapidly developing, resulting in extremely large workload data to be cached and processed, which requires a large amount of computing, communication, and storage resources. In a traditional cloud computing model, the position of a cloud server is far away from a demand side, and the capacity of a return path and a backbone network is limited, so that unpredictable delay is caused, and the reliable service quality and experience quality of the internet of things cannot be guaranteed.
And as a rapid task processing method in the internet of things, the vehicle edge computing VEC expands the computing mode from a remote central distribution framework to a distributed edge server. In the internet of vehicles, computing, communication, and storage resources are distributed close to users and are scattered at the edge of the network. The internet of vehicles may be considered as a beneficial complement to traditional cloud computing. Handling lower computational requirements and severely time-limited tasks at the network edge can eliminate excessive network crossing points, which not only reduces computational response time, but also alleviates the signal congestion problem for backhaul links with limited capabilities. Further, the internet of vehicles transfers the work load with excessive energy consumption to the VEC node with higher computing capacity and continuous energy supply, so that the endurance time of user equipment in the vehicle, such as smart phones and wearable equipment with limited battery capacity, is greatly prolonged. With an appropriate task allocation strategy, the energy consumption of local computation is reduced at the cost of increased energy consumption for data transmission, as well as delays caused by data transmission, workload processing on edge servers, and trans-regional.
Therefore, it is an important issue to implement computation task allocation and power control in VEC scenarios. First, it is difficult to determine an optimal task allocation ratio under different delay constraints due to rapid changes in channel conditions and network topology caused by rapid movement of vehicles. While the vehicle may also leave the service area of the roadside unit during data transmission or task processing. Secondly, task allocation variables of different problems are coupled with each other due to the limited computing capacity of the VEC nodes, and from the perspective of energy efficiency, the task allocation ratio must be optimized jointly with power control. Finally, because the work tasks on the user equipment and the VEC nodes vary randomly, a certain optimal utilization scheme of the computing and communication resources cannot be obtained.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a task allocation and power control method based on an ADMM in the internet of vehicles. By using the algorithm of the invention, the tasks to be calculated and the transmission power can be reasonably distributed on the premise of ensuring the time delay limit, and the energy consumption of the user mobile equipment is effectively reduced.
A task allocation and power control method based on an ADMM in the Internet of vehicles comprises the following steps:
1) determining whether data transmission can be completed before the vehicle leaves the roadside unit service area;
2) the energy loss is obtained by optimizing the iterative process of the nonlinear fractional optimization and the alternative direction multiplier methodThe minimum calculation task distribution ratio and transmission power;
3) the server of the roadside unit calculates the distributed tasks and sends the calculated result to the mobile equipment in the vehicle through the roadside unit under the control of the central controller;
slave user equipmentThe distribution ratio of the task amount to the roadside unit m obeys the average arrival rate ofIn the process of determining whether data transmission can be completed before the vehicle leaves the service area of the roadside unit m, the poisson process of (1) further includes:
1) when the vehicle enters the service range of the roadside unit m, the vehicle speed is determinedAnd distance of vehicle from edge of roadside unitDetermining maximum tolerated timeWhen data transmission timeIf the value is less than the predetermined value, data transmission is possible;
2) at data transmission timeAfter the requirement is met, if the execution time of the whole edge calculation process is metNot more than the time when the vehicle leaves the road sectionAccording to a certain task distribution ratioSending the calculation task to a roadside unit;
the above determining process, which distributes the ratio, delay and energy consumption according to the task amount, is composed of a local calculating process and a data transmission and edge calculating process, and further includes:
1) the distributed tasks are firstly transferred to the in-vehicle transponder from the in-vehicle mobile equipment, then the in-vehicle transponder sends the tasks to the roadside unit by using the maximum transmission power, and the whole process is two-hop transmission; the signal-to-noise ratio of two hops is respectively expressed as:
wherein,andrepresenting the transmission power of the mobile device and the transponder, respectivelyAndrepresenting the channel gain from the mobile device to the repeater and from the repeater to the roadside unit, by N0And (3) representing the unilateral power spectral density of Gaussian white noise, and obtaining a two-hop total signal-to-noise ratio:
and then for the transmitted size isWhen the channel bandwidth isTime of flight, transmission timeObtained by the following formula:
2) for locally computed tasks, the time is computed locallyDemand for computing resources by a task to be computedLocal computing capability of mobile deviceOccupation ratio of task to be calculated to CPU resourceAverage arrival rate ofAnd duty ratio distributionAnd (3) deriving:
3) for the tasks calculated by the server distributed to the roadside units, the total arrival rate of the task amount from different mobile devices waiting to be calculated by the serverThe roadside unit m has c identical servers, each having a computing power ofOn the basis of an M/M/c queue model and an Erlang formula, obtaining the average processing time of a calculation task in a roadside unit M:
wherein
Due to the limited processing capacity of the roadside unit m, the tasks to be calculated are waiting in the necessary queue, then processed by the roadside unit m and the results are sent to the user equipmentThe average waiting time at the roadside unit m for each calculation result is therefore:
wherein,for the transmission processing speed of the roadside unit m, since the data length of the calculation result is much smaller than the calculation task, the calculation result is transmitted from the roadside unit m to the user equipmentThe time delay of (2) can be ignored; when preparing to send the calculation result, if the vehicle isHaving moved out of the coverage of the roadside unit m, the calculation will first be sent to the central controller and then forwarded to the vehicleThe roadside unit m' is located; transmission delay in this processAverage latency at the central controllerAnd waiting time at roadside unit mCan be considered asIs constant, so the latency across the zone can be expressed as:
User equipmentShould include locally calculated energy consumption and energy consumption of transmitted data; definition ofFor local computation power, which depends on the inherent characteristics of the CPU and the complexity of the workload, can be considered constant during task execution;
obtaining user equipment by the following formulaEnergy loss of transmitting data to the in-vehicle transponder:
the energy consumption optimization scheme is an ADMM-based calculation task allocation and power control scheme, and aims to minimize m within the service range of a roadside unit mkDefining an optimized set of variables for the overall energy consumption of a vehicleWhereinThe optimization problem is:
s.t.
C1and C2To limit the arrival rate of the workloadAndcannot exceed user equipment respectivelyAnd the processing rate of roadside units m, C3Ensuring that the transmission power does not exceed the maximum transmission power, C, of the user equipment4And C5Delay limits for the data transmission and task calculation processes, respectively, C6Assigning ratios to tasksThe boundary limit of (2);
in P1, because of different user equipmentsAre coupled, so the optimization objective is inseparable; in order to solve the problem, the method further comprises the following steps:
1) introducing a local copy of the optimal resource allocation strategy; using a new set of variables to represent locally optimized variables, definingAndrespectively asAndthe set of local optimization variables is defined asWherein
The suboptimal problem of P1 can be expressed as:
s.t.
2) p2 target function by introducing local variablesCan be separated, and the objective function is decomposed into mKCan beSub-problems that are solved in parallel, these decentralized joint optimization problems can be expressed as:
the objective function P3 remains a non-convex problem, defining the numerator and denominator of P3 as:
whereinAndrespectively representing the optimal local computation task distribution ratio and the power control strategy;
3) obtaining an optimal target value according to a nonlinear fractional optimization problemThe sufficient requirements of (A) are: if and only if equation
It holds that the optimal local optimization variables are obtained by solving the following problemAnd:
thus, the convex optimization problem with P2 can be expressed as:
5) defining an optimal set of variables associated with P5During each iteration of the iterative algorithm of step 2) of claim 1, the following problem is solved:
wherein the optimal solutionObtained in a previous iteration when limiting the conditionWhen satisfied withIs a set of optimal solutions to the sought optimization problem P1;
for an iterative process, a set of lagrange multipliers corresponding to equation P6 is definedDefining the normal ρ to adjust the convergence speed, the augmented lagrange formula of P6 can be expressed as:
the iteration process comprises two layers of loops, wherein an outer loop is a nonlinear fractional optimization problem, and n is used for indicating the iteration times; the inner loop is the update of the original variable and the dual variable, and t is used for indicating the iteration number,
further comprising:
1) distribution ratio to work taskTransmission powerAnd an optimal solutionInitializing and setting a termination condition;
2) updating optimized variable setsGiven the optimal solution for the nth outer loopFurther obtaining the transmission power of each user equipmentLocal variablesAndcan be decomposed into m that can be resolved in parallelKSub-questions; calculating user equipment according toOptimal task distribution ratio obtained at t-th inner loopAnd transmission power
3) UpdatingObtaining the global optimal task distribution ratio at the t +1 th inner circulation according to the following formula
Obtaining the Lagrange multiplier at the t +1 th internal circulation according to the following formula
4) Updating an optimal solutionIn the iteration process of the initial variable and the dual variable of the ADMM, when t tends to be infinitesimal, the convergence conditions of the objective function, the residual convergence and the dual variable convergence are met; obtained when the inner loop of the nth iteration is terminatedAndthe optimal solution for the (n + 1) th iterationObtained according to the following formula:
5) the cycle is terminated; when the nth outer layer cycle is satisfiedThen, the optimal task distribution ratio is obtained by the following formulaOptimum transmission powerAnd an optimal solution
Compared with the closest prior art, the technical scheme provided by the invention has the beneficial effects that:
the invention introduces how to realize a vehicle networking edge calculation method with higher energy efficiency, solves the energy consumption minimization problem through an alternating direction multiplier method and nonlinear fractional optimization, and considers energy consumption including local calculation and data transmission and delay caused by local calculation, data transmission, waiting time at VEC nodes and roadside units and cross-regions. Under the constraint condition of VEC node computing power, a target function in a fractional form and a coupled optimization variable are provided, and an NP problem is formed.
In order to better build a multitask and multi-server computing mode, a queuing theory is introduced. Dynamic transmission models at the user equipment and VEC nodes are derived taking into account queue heterogeneity. And assuming that the workload generated by each user equipment follows a poisson distribution and the service time of any one user equipment and VEC node follows an exponential distribution, the task transmission models at the user equipment and VEC node can be treated as an M/1 queue and an M/c queue, respectively.
Drawings
FIG. 1 is a diagram of a network of vehicles edge computing system provided by the present invention;
FIG. 2 is a graph of normalized energy consumption versus assignment rate for tasks at different powers provided by the present invention;
FIG. 3 is a graph of normalized energy consumption versus transmission power for different task allocation ratios provided by the present invention;
FIG. 4 is a graph of energy consumption versus number of user devices in various algorithms provided by the present invention;
FIG. 5 is a graph of normalized energy consumption versus roadside unit service radius variation at different powers as provided by the present invention;
FIG. 6 is a graph of algorithm convergence versus iteration number provided by the present invention;
fig. 7 is a graph of normalized energy consumption versus task allocation ratio for different numbers of ues according to the present invention.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
The following description and the drawings sufficiently illustrate specific embodiments of the invention to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. The examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in or substituted for those of others. The scope of embodiments of the invention encompasses the full ambit of the claims, as well as all available equivalents of the claims. Embodiments of the invention may be referred to herein, individually or collectively, by the term "invention" merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed.
Example one
The invention simulates the scene of multi-task and multi-server under the scene of Internet of vehicles, and considering the higher moving speed of vehicles, the task to be calculated can not be completely transmitted in the service range of a roadside unit, and the problem of cross-region can also exist when the calculation result is received. By judging whether the tasks can be distributed to the roadside units for calculation and coordinating the distribution ratio and the transmission power of the tasks, the energy consumption of the user equipment can be reduced under the condition of ensuring the time delay requirement. And determining the roadside unit to which the vehicle belongs by regulating and controlling the central controller, and completing the return of the calculation result. It is also desirable to take into account the latency caused by the limited computing and storage capabilities of the wayside units due to the multitasking by multiple users. The system model diagram is shown in fig. 1, and the whole process includes the following contents:
1. and judging whether the data transmission can be completed in the service range of the roadside unit or not. User equipmentThe task distribution ratio allocated to the roadside unit m obeys the average arrival ratio ofPoisson process of vehicle speedMovement at a distance from the edge of the roadside unitTime of day, data transmission timeNeed not be greater thanAnd the total execution time of the whole edge calculation processNot more than the time when the vehicle leaves the road sectionSatisfy the aboveOn condition, at task distribution ratioAnd sending the calculation task to the roadside unit.
2. The time delay in the execution of the arithmetic execution is mainly composed of transmission time, waiting time and calculation time.
1) The calculation task is transmitted from the in-vehicle user equipment to the roadside unit for two-hop transmission. Wherein the signal to noise ratio from the in-vehicle mobile device to the in-vehicle transponder isThe signal-to-noise ratio from the in-vehicle transponder up to the roadside unit isSo that the total signal-to-noise ratio isThe size of the transmitted data packet isChannel bandwidth ofTime of flight, transmission timeObtained by the following formula:
2) in a ratio ofIs locally computed, with a demand for computing resources ofOccupancy of CPU resourcesLocal computing capability of user equipmentThen the local computation time is obtained:
3) in a ratio ofIs assigned to roadside unit computation. The roadside unit is equipped with c equivalent computing capabilities ofThe server of (1). Since there are multiple user equipments transmitting calculation tasks in the service range of a roadside unit m, the total arrival rate isOn the basis of an M/M/c queue model and an Erlang formula, obtaining the average calculation time of a task to be calculated in a roadside unit M:
4) Due to the limited processing power of the roadside units m, the tasks to be computed must wait in a queue. The transmission processing speed of the roadside unit m isThe average waiting time at the roadside unit m for each calculation result is:
5) when preparing to send the calculation result, if the vehicle isHaving moved out of service of the roadside unit m, the calculation will first be sent to the central controller and then forwarded to the vehicleThe roadside unit m' is located. Transmission delay in this processAverage latency at the central controllerAnd waiting time at roadside unit mCan be regarded as a constant, since the data length of the calculation result is far less than the calculation task, the calculation result is from the roadside unit m to the user equipmentThe delay of (2) can be neglected. The latency across a region can therefore be expressed as:
3. in the calculation process, the energy consumption of the user equipment mainly comprises the energy consumption of local calculation and the energy consumption of data transmission.
1) Calculating power locallyGiven the inherent nature of the CPU and the complexity of the workload, which can be considered as constants during task computation, the energy consumption of the local computation is then:
2) user equipmentHas a data transmission power ofThe energy loss of the data sent by the user equipment to the in-vehicle transponder is as follows:
3) during the implementation of the edge calculation, the total energy loss of the user equipment is:
example II,
The optimization algorithm of the invention is divided into two layers of iteration processes, the outer layer of iteration process solves the problem of nonlinear fractional optimization, and the inner layer of iteration process updates the variables. The goal is to minimize m within the service range of the roadside unit mkOverall energy consumption of the vehicle. The problem is expressed as:
s.t.
due to different user equipmentAre coupled, so the optimization objectives are not separable. To solve this problem, a local copy of the optimal resource allocation policy is introduced and local optimization variables are defined, making the objective function separable:
s.t.
the objective function can thus be decomposed into mKA sub-problem that can be solved in parallel, this problem is a non-convex problem. By further mathematical transformation and defining the value of the objective function asThe problem can be translated into a convex optimization problem and can then be optimized in an iterative process. Adding limiting conditionsAt each iteration thereafter, the following problem
Is solved as follows:
when the condition is limitedWhen satisfied, the result is the optimal solution of the optimization problem. By passingSolving the following augmented Lagrange problem to obtain the variables updated by each inner layer iteration and the optimal solution of the outer layer cycle process:
after initializing variables, in the iteration process of dual variables, the optimal solution of the outer loop can be obtained after the conditions of target function convergence, residual convergence and dual variable convergence are met, and the optimal solution of the target function is obtained after the set loop termination condition is metAnd optimal task allocation ratioAnd optimum transmission power
For the present invention, we performed a number of simulation experiments. As shown in fig. 2, withI.e. more tasks are allocated to the edge compute nodes for computation, the energy consumption decreases first and then increases. This is due to the fact thatSmaller, data transmissions consume less energy than the local computation, and then consume more energy than the local computation with the data transmissions. Fig. 3 shows that the transmission rate increases with increasing transmission power, whereas the energy consumed for data transmission increases faster than the transmission rate, thus showing a monotonic increase in transmission energy loss. Figure 4 reflects the impact of the number of user equipments on the energy consumption under three different optimization schemes. FIG. 5 shows that as the roadside unit coverage increases, the energy loss gradually decreases and tends to increaseAnd (4) stabilizing. In the process shown in fig. 6, it is shown that the iteration of the algorithm can be rapidly converged in 6-7 iterations, that is, the optimal solution can be rapidly obtained. Fig. 7 is a relationship between energy consumption and task allocation ratio for different numbers of ues. The results are consistent with the conclusions of fig. 2 and 4.
Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.
Claims (1)
1. A task allocation and power control method based on an ADMM in the Internet of vehicles is characterized by comprising the following steps:
1) determining whether data transmission can be completed before the vehicle leaves the roadside unit service area;
2) the energy loss is obtained by optimizing the iterative process of the nonlinear fractional optimization and the alternative direction multiplier methodThe minimum calculation task distribution ratio and transmission power;
3) the server of the roadside unit calculates the distributed tasks and sends the calculated result to the mobile equipment in the vehicle through the roadside unit under the control of the central controller;
slave user equipmentThe distribution ratio of the task amount to the roadside unit m obeys the average arrival rate ofFurther, in the process of determining whether the data transmission can be completed before the vehicle leaves the service area of the roadside unit m, the process of poissonThe method comprises the following steps:
1.1 vehicle speed when vehicle enters the service area of roadside unit mAnd distance of vehicle from edge of roadside unitDetermining maximum tolerated timeWhen data transmission timeWhen the value is less than the value, data transmission is carried out;
1.2 at data transfer timeAfter the requirement is met, if the execution time of the whole edge calculation process is metNot more than the time when the vehicle leaves the road sectionAccording to a certain task distribution ratioSending the calculation task to a roadside unit;
distributing the ratio according to the task amount, wherein the time delay and the energy consumption are formed by a local calculation process and a data transmission and edge calculation process, and the method further comprises the following steps:
1.21 the distributed task is firstly transferred to the in-vehicle transponder from the in-vehicle mobile device, then the in-vehicle transponder sends the task to the roadside unit by the maximum transmission power, and the whole process is two-hop transmission; the signal-to-noise ratio of two hops is respectively expressed as:
wherein,andrepresenting the transmission power of the mobile device and the transponder, respectivelyAndrepresenting the channel gain from the mobile device to the repeater and from the repeater to the roadside unit, by N0And (3) representing the unilateral power spectral density of Gaussian white noise, and obtaining a two-hop total signal-to-noise ratio:
and then for the transmitted size isWhen the channel bandwidth isTime of flight, transmission timeObtained by the following formula:
1.22 for locally calculated tasks, calculate time locallyDemand for computing resources by a task to be computedLocal computing capability of mobile deviceOccupation ratio of task to be calculated to CPU resourceAverage arrival rate ofAnd duty ratio distributionAnd (3) deriving:
1.23 for the server assigned to the roadside units to perform the calculated tasks, there is a total arrival rate of the amount of tasks from the different mobile devices waiting to be calculated by the serverThe roadside unit m has c identical servers, each having a computing power ofOn the basis of an M/M/c queue model and an Erlang formula, obtaining the average processing time of a calculation task in a roadside unit M:
wherein
Due to the limited processing capacity of the roadside unit m, the tasks to be calculated are waiting in the necessary queue, then processed by the roadside unit m and the results are sent to the user equipmentThe average waiting time at the roadside unit m for each calculation result is therefore:
wherein,for the transmission processing speed of the roadside unit m, since the data length of the calculation result is much smaller than the calculation task, the calculation result is transmitted from the roadside unit m to the user equipmentThe delay of (2) is ignored; when preparing to send the calculation result, if the vehicle isHaving moved out of the coverage of the roadside unit m, the calculation will first be sent to the central controller and then forwarded to the vehicleThe roadside unit m' is located; transmission delay in this processAverage latency at the central controllerAnd waiting time at roadside unit mConsidered constant, the time delay across the region is thus expressed as:
User equipmentShould include locally calculated energy consumption and energy consumption of transmitted data; definition ofFor local calculation of power, dependent on the inherent characteristics of the CPU and the workloadComplexity, treated as a constant during task execution;
obtaining user equipment by the following formulaEnergy loss of transmitting data to the in-vehicle transponder:
the energy consumption optimization scheme is an ADMM-based calculation task allocation and power control scheme, and aims to minimize m within the service range of a roadside unit mkDefining an optimized set of variables for the overall energy consumption of a vehicleWhereinThe optimization problem is:
s.t.
C1and C2To limit the arrival rate of the workloadAndcannot exceed user equipment respectivelyAnd the processing rate of roadside units m, C3Ensuring that the transmission power does not exceed the maximum transmission power, C, of the user equipment4And C5Delay limits for the data transmission and task calculation processes, respectively, C6Assigning ratios to tasksThe boundary limit of (2);
in P1, because of different user equipmentsAre coupled, so the optimization objective is inseparable; in order to solve the problem, the method further comprises the following steps:
2.1 introducing a local copy of the optimal resource allocation strategy; using a new set of variables to represent locally optimized variables, definingAndrespectively asAndthe set of local optimization variables is defined asWherein
The suboptimal problem of P1 is expressed as:
s.t.
2.2P 2 target function by introducing local variablesCan be separated and decomposed into objective functionsmKThese decentralized joint optimization problems are expressed as:
the objective function P3 remains a non-convex problem, defining the numerator and denominator of P3 as:
whereinAndrespectively representing the optimal local computation task distribution ratio and the power control strategy;
2.3 obtaining the optimal target value according to the nonlinear fractional optimization problemThe sufficient requirements of (A) are: if and only if equation
It holds that the optimal local optimization variables are obtained by solving the following problemAnd
thus, the convex optimization problem with P2 is expressed as:
2.5 defining the optimal set of variables associated with P5Step 2) in each iteration process of the iterative algorithm, the following problems are solved:
wherein the optimal solutionObtained in a previous iteration when limiting the conditionWhen satisfied withIs a set of optimal solutions to the sought optimization problem P1;
for an iterative process, define the set of lagrange multipliers μ corresponding to equation P6m={μ1,...,μmk,...,μmKDefining a normal ρ to adjust the convergence speed, the augmented lagrange formula of P6 is expressed as:
the iteration process comprises two layers of loops, wherein an outer loop is a nonlinear fractional optimization problem, and n is used for indicating the iteration times; the inner loop is the update of the original variable and the dual variable, and t is used for indicating the iteration number,
further comprising:
2.51 assignment ratio to work taskTransmission powerAnd an optimal solutionInitializing, setting termination conditions;
2.52 updating optimized variable setsGiven the optimal solution for the nth outer loopFurther obtaining the transmission power of each user equipmentLocal variablesAndis decomposed into m that can be resolved in parallelKSub-questions; calculating user equipment according toOptimal task distribution ratio obtained at t-th inner loopAnd transmission power
2.53 updateObtaining the global optimal task distribution ratio at the t +1 th inner circulation according to the following formula
Obtaining the Lagrange multiplier at the t +1 th internal circulation according to the following formula
2.54 update the optimal solutionIn the iteration process of the initial variable and the dual variable of the ADMM, when t tends to be infinitesimal, the convergence conditions of the objective function, the residual convergence and the dual variable convergence are met; obtained when the inner loop of the nth iteration is terminatedAndthe optimal solution for the (n + 1) th iterationObtained according to the following formula:
2.55 the cycle is terminated; when the nth outer layer cycle is satisfiedThen, the optimal task is obtained by the following formulaDistribution ratioOptimum transmission powerAnd an optimal solution
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