Wireless Sensor Networks(WSN) are utilized in many fields such as environmental monitoring and military applications. The nodes of WSNs are not rechargeable, so energy conservation in these networks is important. One ...
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Wireless Sensor Networks(WSN) are utilized in many fields such as environmental monitoring and military applications. The nodes of WSNs are not rechargeable, so energy conservation in these networks is important. One of the important issues in these networks is to optimize energy in message broadcasting. Depending on the ability of nodes and antennas, broadcasting is done in two means: directional and omni-directional antennas. There are centralized algorithms to broadcast message in wireless networks either by directional or omni-directional antennas. The problem of minimizing energy in broadcasting and multicasting is Non-polynomial-hard. In this paper, a centralized algorithm is proposed to improve energy and running time of the algorithm by using directional antennas. As evolutionary algorithms by omni-directional antenna are better than heuristic algorithms in terms of the time and the average result;a new approach based on particle swarm optimization (PSO) as an evolutionary algorithm is proposed in this paper. We have also considered and evaluated most of famous evolutionary algorithms such as Simulated Annealing (SA), genetic algorithm (GA), Teaching-Learning-Based Optimization (TLBO), Harmony Search (HS) and Ant Colony Optimization (ACO). The experiment results indicate that the proposed method is effective especially in term of energy conservation. (C) 2017 Elsevier B.V. All rights reserved.
Cellular communication system is the most widely used communication system as commercial purpose. Mobile phones have become much more than mere communication devices. The encouragement for Telecommunication operators ...
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ISBN:
(纸本)9781509016402
Cellular communication system is the most widely used communication system as commercial purpose. Mobile phones have become much more than mere communication devices. The encouragement for Telecommunication operators towards the energy consumption problem is to optimize the utilization of network equipment. Energy consumption of BSs is considerable even when traffic load is low. In our study, we consider UMTS scenario with a simplified traffic model describing. This paper offers a mechanism of energy efficient with dynamically operation depends on traffic load, bit rate and cellular capacity. In this paper, concept of cell zooming by using centralized algorithm is investigated, and simulation result shows that the proposed algorithm can greatly reduces the energy consumption up to 70%, which leads to green cellular network.
Caching popular contents at mobile devices can potentially improve the quality of service for mobile users and relieve traffic burden of base station in cellular networks. In this paper, we jointly consider the resour...
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Caching popular contents at mobile devices can potentially improve the quality of service for mobile users and relieve traffic burden of base station in cellular networks. In this paper, we jointly consider the resource allocation, the cached contents, and the distance between two devices for the optimal device pairing problem in centralized and distributed cases, where the BS is the central controller in the centralized case. The joint optimization problem of device-to-device (D2D) caching with channel allocation is formulated as a weighted four-uniform hypergraph model. The optimal solution for the problem is 4-D maximum weighted matching (4-DMWM), which is NP-hard unfortunately. To approach the 4-DMWM with low-complexity, we adopt the greedy algorithm and the squareIMP algorithm in the centralized case. Moreover, distributed algorithms are also designed for the caching problem in both synchronous and asynchronous cases. The simulation results will illustrate that the squareIMP algorithm can be used to get a better transmission rate with the complexity of O(n(5)), while the greedy algorithm can be used in the case with stringent latency requirement for centralized 4-DMWM problem. The sum rate of distributed asynchronous algorithm is close to the centralized greedy algorithm with the complexity of O(n(2)) for each device. However, the simulation result of the synchronous algorithm is slightly lower than the centralized algorithm, where each device performs O(n(2)) computational operations in each iteration. Therefore, the algorithms proposed in this paper can be used in different cases for solving optimal D2D pairing and channel allocation problem.
In a distributed system, process synchronization is an important agenda. One of the major duties for process synchronization is mutual exclusion. This paper presents a new centralized fault tolerant distributed mutual...
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ISBN:
(纸本)9780889866379
In a distributed system, process synchronization is an important agenda. One of the major duties for process synchronization is mutual exclusion. This paper presents a new centralized fault tolerant distributed mutual exclusion algorithm based on Agrawala and El-Abbadi's algorithm. In new algorithm, once coordinator crashes, algorithm can recover lost data and return the coordinator in earlier situation. Thus fault tolerance will ascend and centralize algorithm's "single point of failure" will be omitted. So based algorithm will be more reliable. The only trade off is consuming some inappreciable time in case of coordinator's crash.
Channel allocation problem is a major task, especially in dense deployments of wireless local area networks (WLANs). In such cases, opportunistic spectrum access (OSA) is considered to be a promising approach to dimin...
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ISBN:
(纸本)9781467384513
Channel allocation problem is a major task, especially in dense deployments of wireless local area networks (WLANs). In such cases, opportunistic spectrum access (OSA) is considered to be a promising approach to diminish congestion of the ISM band in highly dense WLANs scenarios. OSA allows to secondary users, the use of underutilized licensed channels, without affecting legacy users. In this paper, centralized simulated annealing algorithms applied to uncoordinated and congested WLANs deployments are developed. Unlike currents channel assignments mechanisms, several distinguished issues should be addressed for OSA-enabled WLANs: band prioritization and channel bandwidth. On this basis, the development and assessment of centralized simulated annealing algorithms (CSA) that cope with the OSA channel allocation problem and considers channel prioritization and channel bandwidth restrictions, are presented.
We study asynchronous broadcasting in packet radio networks. A radio network is represented by a directed graph, in which one distinguished source node stores a message that needs to be disseminated among all the rema...
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We study asynchronous broadcasting in packet radio networks. A radio network is represented by a directed graph, in which one distinguished source node stores a message that needs to be disseminated among all the remaining nodes. An asynchronous execution of a protocol is a sequence of events, each consisting of simultaneous deliveries of messages. The correctness of protocols is considered for specific adversarial models defined by restrictions on events the adversary may schedule. A protocol specifies how many times the source message is to be retransmitted by each node. The total number of transmissions over all the nodes is called the work of the broadcast protocol;it is used as complexity measure. We study computational problems, to be solved by deterministic centralized algorithms, either to find a broadcast protocol or to verify the correctness of a protocol, for a given network. The amount of work necessary to make a protocol correct may have to be exponential in the size of network. There is a polynomial-time algorithm to find a broadcast protocol for a given network. We show that certain problems about broadcasting protocols for given networks are complete in NP and co-NP complexity classes. (c) 2007 Elsevier B.V. All rights reserved.
This letter introduces a centralized joint power and admission control algorithm for cognitive radio networks. Its novelty lies in the proposed admission metric. Unlike those in existing algorithms, our metric predete...
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This letter introduces a centralized joint power and admission control algorithm for cognitive radio networks. Its novelty lies in the proposed admission metric. Unlike those in existing algorithms, our metric predetermines the admission order of N secondary users which intend to access the network. This allows us to search a group of admitted secondary users with the bisection method. The proposed algorithm is shown by simulation to achieve a comparable performance to existing alorithms, and the computational complexity is reduced from O (N-3) to O(N-2 log(2) N).
Wireless networks are developed under the fashion of wider spectrum utilization (e.g., cognitive radio) and multi-hop communication (e.g., wireless mesh networks). In these paradigms, how to effectively allocate t...
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Wireless networks are developed under the fashion of wider spectrum utilization (e.g., cognitive radio) and multi-hop communication (e.g., wireless mesh networks). In these paradigms, how to effectively allocate the spectrum to different transmission links with minimized mutual interference becomes the key concern. In this paper, we study the throughput optimization via spectrum allocation in cognitive radio networks (CRNs). The previous studies incorporate either the conflict graph or SINR model to characterize the interference relationship. However, the former model neglects the accumulative interference effect and leads to unwanted interference and sub-optimal results, while the work based on the latter model neglects its heavy reliance on the accuracy of estimated RSS (receiving signal strength) among all potential links. Both are inadequate to characterize the complex relationship between interference and throughput. To this end, by considering the feature of CRs, like spectrum diversity and non-continuous OFDM, we propose a measurement-assisted SINR-based cross-layer throughput optimization solution. Our work concerns features in different layers: in the physical layer, we present an efficient RSS estimation algorithm to improve the accuracy of the SINR model; in the upper layer, a flow level SINR-based throughput optimization problem for WMNs is modelled as a mixed integer non-linear programming problem which is proved to be NP-hard. To solve this problem, a centralized (1 -ε)-optimal algorithm and an efficient distributed algorithm are provided. To evaluate the algorithm performance, the real-world traces are used to illustrate the effectiveness of our scheme.
A set of identical, mobile agents is deployed in a weighted network. Each agent has a battery-a power source allowing it to move along network edges. An agent uses its battery proportionally to the distance traveled. ...
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A set of identical, mobile agents is deployed in a weighted network. Each agent has a battery-a power source allowing it to move along network edges. An agent uses its battery proportionally to the distance traveled. We consider two tasks: convergecast, in which at the beginning, each agent has some initial piece of information, and information of all agents has to be collected by some agent;and broadcast in which information of one specified agent has to be made available to all other agents. In both tasks, the agents exchange the currently possessed information when they meet. The objective of this paper is to investigate what is the minimal value of power, initially available to all agents, so that convergecast or broadcast can be achieved. We study this question in the centralized and the distributed settings. In the centralized setting, there is a central monitor that schedules the moves of all agents. In the distributed setting every agent has to perform an algorithm being unaware of the network. In the centralized setting, we give a linear-time algorithm to compute the optimal battery power and the strategy using it, both for convergecast and for broadcast, when agents are on the line. We also show that finding the optimal battery power for convergecast or for broadcast is NP-hard for the class of trees. On the other hand, we give a polynomial algorithm that finds a 2-approximation for convergecast and a 4-approximation for broadcast, for arbitrary *** the distributed setting, we give a 2-competitive algorithm for convergecast in trees and a 4-competitive algorithm for broadcast in trees. The competitive ratio of 2 is proved to be the best for the problem of convergecast, even if we only consider line networks. Indeed, we show that there is no ()-competitive algorithm for convergecast or for broadcast in the class of lines, for any .
The virtualized resource allocation (mapping) algorithm is the core issue of network virtualization technology. Universal and excellent resource allocation algorithms not only provide efficient and reliable network re...
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The virtualized resource allocation (mapping) algorithm is the core issue of network virtualization technology. Universal and excellent resource allocation algorithms not only provide efficient and reliable network resources sharing for systems and users, but also simplify the complexity of resource scheduling and management, improve the utilization of basic resources, balance network load and optimize network performance. Based on the application of wireless sensor network, this paper proposes a wireless sensor network architecture based on cloud computing. The WSN hardware resources are mapped into resources in cloud computing through virtualization technology, and the resource allocation strategy of the network architecture is proposed. The experiment evaluates the performance of the resource allocation strategy. The proposed heuristic algorithm is a distributed algorithm. The complexity of centralized algorithms is high, distributed algorithms can handle problems in parallel, and reduce the time required to get a good solution with limited traffic.
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