Mobile edge computing (MEC) provides a new computing paradigm that can overcome the inability of the traditional cloud computing paradigm to ensure low service latency by pushing computing power and resources to the n...
详细信息
Mobile edge computing (MEC) provides a new computing paradigm that can overcome the inability of the traditional cloud computing paradigm to ensure low service latency by pushing computing power and resources to the network edge. Many studies have attempted to formulate edge data caching strategies for app vendors to optimize caching performance by caching the right data on the right edge servers. However, existing edge data caching approaches have unfortunately ignored fairness, which is an important issue from the app vendor's perspective. In general, an app vendor needs to cache data on edge servers to serve its users with insignificant latency differences at a minimum caching cost. In this paper, we make the first attempt to tackle the fair edge data caching (FEDC) problem. Specifically, we formulate the FEDC problem as a constraint optimization problem (COP) and prove its $\mathcal {NP}$NP-hardness. An optimal approach named FEDC-OPT is proposed to find optimal solutions to small-scale FEDC problems with integer programming technique. In addition, an approximate algorithm named FEDC-APX is proposed to find approximate solutions in large-scale FEDC problems. The performance of the proposed approaches is analyzed theoretically, and evaluated experimentally on a widely-used real-world data set against four representative approaches. The experimental results show that the proposed approaches can solve the FEDC problem efficiently and effectively.
We consider a classic machine scheduling problem under resource constraints. Given m parallel identical machines and a collection of additional but renewable resources, each task requires both a machine and one partic...
详细信息
We consider a classic machine scheduling problem under resource constraints. Given m parallel identical machines and a collection of additional but renewable resources, each task requires both a machine and one particular resource at any time of its processing. The goal is to allocate the machines and resources to the tasks so as to minimize the makespan, that is, the maximum completion time of all tasks. Because of NP-hardness of the problem, we design a three-stage combinatorial algorithm with performance ratio 2m+2/m+3 that improves the best prior ratio for m >= 3 machines and ties with that for m = 2 machines.
In the paper, we design an adaptive algorithm for non-submodular set function maximization over a single matroid constraint. We measure the deviation of the set function from fully submodular with the help of the gene...
详细信息
In the paper, we design an adaptive algorithm for non-submodular set function maximization over a single matroid constraint. We measure the deviation of the set function from fully submodular with the help of the generic submodularity ratio gamma. The adaptivity quantifies the information theoretic complexity of oracle optimization for parallel computations. We propose a new approximation algorithm based on the continuous greedy approach and prove that the algorithm could obtain a fractional solution with approximation ratio (1 - e(-gamma 2) - O(epsilon)) in O(log n log(k/gamma epsilon)/epsilon(-2) log n log(1/gamma) - epsilon(-1) log(1-epsilon)) then use the contention resolution schemes to convert the fractional solution to a discrete one with gamma (1 - e(-1))(1 - e(-gamma 2) - O(epsilon))-approximation.
Exploiting drones as flying base stations to assist the terrestrial cellular networks or replace them is promising in 5G and beyond. One of the challenging problems is optimally deploying multiple drones to achieve co...
详细信息
Exploiting drones as flying base stations to assist the terrestrial cellular networks or replace them is promising in 5G and beyond. One of the challenging problems is optimally deploying multiple drones to achieve coverage for the ground users. Usually, the goal is to find the minimum number of drones and their placement when all users are served. In this work, we consider a more realistic scenario. We focus on the situation where the number of drones is given in advance, and this number is significantly smaller than the number required to cover all ground users. This assumption is reasonable in emergency cases or battlefields where the number of ground users (for example, soldiers or firefighters) is much larger than the number of drones. Additionally, we consider the case when the ground users have a rank, interpreted as weight, and we aim to deploy drones' swarm such that the sum of the weights of the ground users covered by the swarm is maximized while the drones in the swarm are connected (without involving a third party entity that provides connectivity in the swarm). Our solution significantly improves currently best known approximation ratio for the problem from 1/144 to 1/28.
Recently, adopting UAVs equipped with the edge computing platform to provide computing service has been considered as a promising approach for resource-limited devices in mobile edge computing (MEC). Unfortunately, th...
详细信息
Recently, adopting UAVs equipped with the edge computing platform to provide computing service has been considered as a promising approach for resource-limited devices in mobile edge computing (MEC). Unfortunately, the limited resources (e.g., energy, computing and communication) of the UAV may significantly restrict its service capability, which means it has to selectively provide task offloading service to achieve the maximal benefit. In this article, aiming at optimizing the overall benefit of the UAV in a single dispatch, we propose an approximate Benefit Maximizing Task Offloading (BMTO) algorithm, which jointly considers the trajectory scheduling of the UAV and the offloading strategy of tasks. Specially, the flight path of the UAV is decomposed into several hover sites, which are selected by a benefit-cost approach. And the offloading sequence of tasks is arranged to maximize the benefit of the UAV through a surrogate function, which is proved to be a nonnegative monotone submodular function. Thus we transform the original problem into a submodular maximization problem and theoretically prove that BMTO owns an approximation ratio of 1/2 (1 - 1/e) . Simulation results show that our proposed algorithm outperforms the benchmark algorithms in terms of total benefit as well as energy efficiency ratio.
Smart transportation shall address utility waste, traffic congestion, and air pollution problems with least human intervention in future smart cities. To realize the sustainable operation of smart transportation, we l...
详细信息
Smart transportation shall address utility waste, traffic congestion, and air pollution problems with least human intervention in future smart cities. To realize the sustainable operation of smart transportation, we leverage solar-harvesting charging stations and rooftops to power electric autonomous vehicles(AVs) solely via design. With a fixed budget, our framework first optimizes the locations of charging stations based on historical spatial-temporal solar energy distribution and usage patterns, achieving (2+e) factor to the optimal. Then a stochastic algorithm is proposed to update the locations online to adapt to any shift in the distribution. Based on the deployment, a strategy is developed to assign energy requests in order to minimize their traveling distance to stations while not depleting their energy storage. Equipped with extra harvesting capability, we also optimize route planning to achieve a reasonable balance between energy consumed and harvested en-route. As a promising application, utility optimization of shared electric AVs is discussed, and (2k+1)-approx algorithm is proposed to manage $k$k vehicles simultaneously. Our extensive simulations demonstrate the algorithm can approach the optimal solution within 10-15% approximation error, improve the operating range of vehicles by up to 2-3 times, and improve the utility by more than 50% compared to other competitive strategies.
In this paper, we propose some new semidefinite relaxations for a class of nonconvex complex quadratic programming problems, which widely appear in the areas of signal processing and power system. By deriving new vali...
详细信息
In this paper, we propose some new semidefinite relaxations for a class of nonconvex complex quadratic programming problems, which widely appear in the areas of signal processing and power system. By deriving new valid constraints to the matrix variables in the lifted space, we derive some enhanced semidefinite relaxations of the complex quadratic programming problems. Then, we compare the proposed semidefinite relaxations with existing ones, and show that the newly proposed semidefinite relaxations could be strictly tighter than the previous ones. Moreover, the proposed semidefinite relaxations can be applied to more general cases of complex quadratic programming problems, whereas the previous ones are only designed for special cases. Numerical results indicate that the proposed semidefinite relaxations not only provide tighter relaxation bounds, but also improve some existing approximation algorithms by finding better sub-optimal solutions.
This paper studies single vehicle scheduling problems with two agents on a line-shaped network. Each of two agents has some customers that are situated at some vertices on the network. A vehicle has to start from upsi...
详细信息
This paper studies single vehicle scheduling problems with two agents on a line-shaped network. Each of two agents has some customers that are situated at some vertices on the network. A vehicle has to start from upsilon(0) to serve all customers. The objective is to schedule the customers to minimize C-max(A) + theta C-max(B), where C-max(X) is the latest completion time of the customers for agent X and X is an element of{A,B}. We first propose a polynomial time algorithm for the problem without release time. Next, the problem with release time is proved to be NP-hard despite of a network with only two vertices. Then, we present a 3+root 5/2 -approximation algorithm. Finally, numerical experiments are carried out to verify the approximation algorithm is effective.
Recently, adopting mobile-edge computing (MEC) to accommodate the compute-intensive and delay-sensitive tasks from mobile devices has gained increasing attention from the research community. In contrast to a cloud-cen...
详细信息
Recently, adopting mobile-edge computing (MEC) to accommodate the compute-intensive and delay-sensitive tasks from mobile devices has gained increasing attention from the research community. In contrast to a cloud-centric scheme, deploying servers at the network edge offers the advantage of delivering faster and more efficient services. However, pioneering works primarily focus on a homogeneous server deployment strategy, which distributes the same quantity of servers among a specific number of selected locations. In this work, we aim to lay the theoretical foundation for budget-constrained profits maximization (BCPM) problem, which is a coupled problem of server deployment and task scheduling. Subsequently, a two-step optimization method is proposed. Through seeking the maximum matches in the constructed bipartite graph, a task scheduling algorithm is first designed to maximize the profits under the server deployment. Then, two approximation algorithms with provable approximation ratios are exploited to perform nearly optimal deployment of servers in a homogeneous and heterogeneous manner, respectively. Extensive simulations with real-world data set and system settings are conducted. The results show that the proposed algorithms can achieve at least a 10.54% increase in total profits and the average processing delay of tasks can be shortened by about 17%.
DENSEST k-SUBGRAPH is the problem to find a vertex subset S of size k such that the number of edges in the subgraph induced by S is maximized. In this paper, we show that DENSEST k-SUBGRAPH is fixed parameter tractabl...
详细信息
DENSEST k-SUBGRAPH is the problem to find a vertex subset S of size k such that the number of edges in the subgraph induced by S is maximized. In this paper, we show that DENSEST k-SUBGRAPH is fixed parameter tractable when parameterized by neighborhood diversity, block deletion number, distance-hereditary deletion number, and cograph deletion number, respectively. Furthermore, we give a 2-approximation 2(tc(G)/2)n(O(1))-time algorithm where tc(G) is the twin cover number of an input graph G.
暂无评论