共查询到20条相似文献,搜索用时 15 毫秒
1.
This article proposes an optimized in-band control channel scheme with channel selection scheduling algorithm and network coding based transmission paradigm in the distributed cognitive radio network (... 相似文献
2.
Topology control for multihop packet radio networks 总被引:1,自引:0,他引:1
A distributed topology-control algorithm has been developed for each node in a packet radio network (PRN) to control its transmitting power and logical neighbors for a reliable high-throughput topology. The algorithm first constructs a planar triangulation from locations of all nodes as a starting topology. Then, the minimum angles of all triangles in the planar triangulation are maximized by means of edge switching to improve connectivity and throughput. The resulting triangulation at this stage, the Delaunay triangulation, can be determined locally at each node. The topology is modified by negotiating among neighbors to satisfy a design requirement on the nodal degree parameter. Simulations show that the final topology is degree-bounded, has a rather regular and uniform structure, and has throughput and reliability that are greater than that of a number of alternative topologies 相似文献
3.
Scheduling algorithms for multihop radio networks 总被引:1,自引:0,他引:1
Algorithms for transmission scheduling in multihop broadcast radio networks are presented. Both link scheduling and broadcast scheduling are considered. In each instance, scheduling algorithms are given that improve upon existing algorithms both theoretically and experimentally. It is shown that tree networks can be scheduled optimally and that arbitrary networks can be scheduled so that the schedule is bounded by a length that is proportional to a function of the network thickness times the optimum. Previous algorithms could guarantee only that the schedules were bounded by a length no worse than the maximum node degree times optimum. Since the thickness is typically several orders of magnitude less than the maximum node degree, the algorithms presented represent a considerable theoretical improvement. Experimentally, a realistic model of a radio network is given and the performance of the new algorithms is studied. These results show that, for both types of scheduling, the new algorithms (experimentally) perform consistently better than earlier methods 相似文献
4.
We analyze the performance of a fully decentralized relay-selection method for the relay-assisted Cognitive Radio (CR) systems.
The method requires no explicit communication among relay, assumes no prior knowledge of geometry. In particular, we assume
that the frequencies chosen by the relay-assisted CR network overlapped with an active primary link. The proposed relay-selection
scheme decreases the outage probability by considering both the channel scenario and the interference to the primary link
compared with the non-cooperative transmission. Benefits of cooperative diversity are increased with the increased number
of relays. 相似文献
5.
Dinesh DatlaAuthor Vitae Haris I. Volos Author VitaeS.M. Hasan Author Vitae Jeffrey H. Reed Author VitaeTamal Bose Author Vitae 《Ad hoc Networks》2012,10(5):845-857
Individual cognitive radio nodes in an ad-hoc cognitive radio network (CRN) have to perform complex data processing operations for several purposes, such as situational awareness and cognitive engine (CE) decision making. In an implementation point of view, each cognitive radio (CR) may not have the computational and power resources to perform these tasks by itself. In this paper, wireless distributed computing (WDC) is presented as a technology that enables multiple resource-constrained nodes to collaborate in computing complex tasks in a distributed manner. This approach has several benefits over the traditional approach of local computing, such as reduced energy and power consumption, reduced burden on the resources of individual nodes, and improved robustness. However, the benefits are negated by the communication overhead involved in WDC. This paper demonstrates the application of WDC to CRNs with the help of an example CE processing task. In addition, the paper analyzes the impact of the wireless environment on WDC scalability in homogeneous and heterogeneous environments. The paper also proposes a workload allocation scheme that utilizes a combination of stochastic optimization and decision-tree search approaches. The results show limitations in the scalability of WDC networks, mainly due to the communication overhead involved in sharing raw data pertaining to delegated computational tasks. 相似文献
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7.
Cognitive radio is a revolutionary technology that promises to alleviate the spectrum shortage problem and to bring about remarkable improvement in spectrum utilization. Spectrum sensing is one of the essential mechanisms of CR and is an active area of research. Although the operational aspects of spectrum sensing are being studied actively, its security aspects have attracted very little attention. In this paper, we discuss security issues that may pose a serious threat to spectrum sensing. Specifically, we focus on two security threats - incumbent emulation and spectrum sensing data falsification - that may wreak havoc in distributed spectrum sensing. We also discuss methods for countering these threats and the technical hurdles that must be overcome to implement such countermeasures. 相似文献
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9.
Slimeni Feten Chtourou Zied Scheers Bart Nir Vincent Le Attia Rabah 《Wireless Networks》2019,25(7):4161-4171
Wireless Networks - This paper deals with the jamming attack which may hinder the cognitive radio from efficiently exploiting the spectrum. We model the problem of channel selection as a Markov... 相似文献
10.
Channel assignment is a challenge for distributed cognitive networks due to spectrum mobility and lack of centralized entity.
We present a dynamic and efficient algorithm via conflict shifting, referred as Shifting-based Channel Assignment (SCA). In
this algorithm, the system was modeled with a conflict graph, and users cannot assign the channels that primary users (legacy
users) and neighbors already occupied. In order to eliminate the conflicts between neighbors efficiently, secondary users
(unlicensed users) try to transfer them through a straight path to the boundary, where conflicts are easier to solve as there
are less neighbors for boundary users. Actions in one shift are executed in slots, and users act in a synchronous and separated
manner. As a result, some of the conflicting channels are avoid from directly abandoned, and for this, utility of the entire
network can be improved. Simulation results show that the proposed algorithm can provide similar utility performance while
obviously reducing the communication cost than bargaining-base algorithms. In small scale networks with low user mobility
(under 20%), it reduces 50% of the communication overhead than the later. 相似文献
11.
Wireless Networks - To achieve energy efficiency is very important for future cognitive radio networks since we need less power consumption and much more transmitted information. In this paper, we... 相似文献
12.
Scheduling broadcasts in multihop radio networks 总被引:1,自引:0,他引:1
A comprehensive study of the problem of scheduling broadcast transmissions in a multihop, mobile packet radio network is provided that is based on throughput optimization subject to freedom from interference. It is shown that the problem is NP complete. A centralized algorithm that runs in polynomial time and results in efficient (maximal) schedules is proposed. A distributed algorithm that achieves the same schedules is then proposed. The algorithm results in a maximal broadcasting zone in every slot 相似文献
13.
Cognitive radio (CR) is a novel and promising spectrum management technique, which aims to cope with the spectrum scarcity problem occurring in unlicensed bands and alleviate the inefficient spectrum utilization of licensed bands. To ensure that the operation of licensed users will not be adversely affected and that the licensed bands can be efficiently utilized by unlicensed users, this paper proposes a cognitive radio MAC protocol called SMC-CR-MAC. When any primary user is detected, the proposed SMC-CR-MAC protocol applies Contiguous Channel Switching and Sender-Receiver Channel Swap rules to cope with the rendezvous, packet collision, and channel congestion problems. Simulation results show that the proposed SMC-CR-MAC protocol can significantly improve the network performance in terms of utilization of licensed bands, standard deviation of traffic load on each channel, and probability of successful rendezvous. 相似文献
14.
In a network deployment, a cognitive radio will have to perform two fundamental tasks. First, each cognitive radio needs to optimize its internal operation, and second, it needs to derive a configuration that will enable and optimize communication with other nodes in the network. This latter requirement, however, relies on knowledge about the other nodes’ current configuration settings, which needs to be incorporated into this decision-making process. Collecting and distributing such global knowledge is, however, a difficult and costly process, which, in the past, has been approached by introducing a centralized control authority, distributed negotiation policies, or a dedicated coordination channel in the network, each resulting in vulnerability and scaling issues. In this paper, we propose an alternative approach to the global configuration of a cognitive radio network that eliminates the need to collect global network state information and, instead, uses local information for its decision making process. This technique is built upon the principles of swarm intelligence, as seen in schools of fish and flocks of birds, and allows for efficient and robust coordination of a cognitive radio network in a variety of tasks. We have implemented a working prototype showing the feasibility of this technique in two simulation environments and in a hardware testbed, and find that a solution based on swarm intelligence is well suited to interoperate in heterogeneous deployment environments with other control algorithms, requires low computational overhead, and scales with the number of nodes and the amount of spectrum, thus making it a versatile control algorithm for many deployment scenarios. 相似文献
15.
当FCC提出传统电视系统和认知无线电网络频谱共享,以增加频谱的利用率时,主要涉及到的问题之_是来自认知无线电网络的干扰不得影响主用户的QoS。在本文中,考虑由低功耗个人/便携设备组成的认知无线电网络与传统电视系统同时运作的情况。本文在保证主用户和认知用户的QoS的情况下,推导出问题的可行性条件,并提出集中式和分布式两种解决方案,最大限度地提高认知用户的能源效率。并且通过仿真表明该方案的有效性。 相似文献
16.
Wireless Networks - Cognitive radio technology provides opportunistic wireless spectrums access for the secondary users (SUs) while primary users (PUs) are dormant. By emergence of a PU in the... 相似文献
17.
Whereas cellular systems have traditionally adopted single‐hop transmissions between the mobile station (MS) and the base station (BS), researchers expect multihop transmission to be utilised in the future. Cellular systems present several challenges, such as channel assignment, which are exacerbated by multimedia service traffic and an increasing number of subscribers. Recently, a clustered multihop cellular network (cMCN) architecture that complements traditional cellular systems has been proposed and studied using fixed channel assignment (FCA). However, the performance of FCA is limited when the traffic pattern varies in a service area. This paper proposes the use of dedicated information ports (DIPs) as clusterheads in cMCN, followed by a multihop dynamic channel assignment (mDCA) scheme. The mDCA works by assigning channels based on information about interference in surrounding cells. Two different channel searching strategies are developed and evaluated. Through computer simulation, we show that the proposed mDCA is able to achieve a significantly improved capacity which is maintained when the number of system channels is increased. Finally, issues regarding the implementation of the mDCA and future work on this topic are discussed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
18.
为了深入研究分布式认知无线电网络的多路径路由问题,阐述了分布式认知无线电网络基本特征以及多路径路由设计面临的问题与挑战。分布式认知无线电网络多路径路由采用多路径并行传输,可有效降低传输时延、增加网络吞吐量与传输可靠性、实现网络负载均衡。根据路由优化目标不同,从吞吐量、带宽、干扰、时延、负载均衡和路由发现六方面对近年来多路径路由协议的主要研究成果进行了分类,然后逐类对多路径路由协议进行了分析和讨论,最后分别从分布式认知无线电网络基本特征的适应性与多路径路由协议特征两个方面进行了比较,并展望了分布式认知无线电网络多路径路由协议需进一步研究的方向。 相似文献
19.
The channel assignment problem involves not only assigning channels or frequencies to each radio cell. but also satisfying frequency constraints given by a compatibility matrix. The proposed parallel algorithm is based on an artificial neural network composed of nm processing elements for an n -cell-m -frequency problem. The algorithm runs not only on a sequential machine but also on a parallel machine with up to a maximum of nm processors. The algorithm was tested by solving eight benchmark problems where the total number of frequencies varied from 100 to 533. The algorithm found the solutions in nearly constant time with nm processors. The simulation results showed that the algorithm found better solutions than the existing algorithm in one out of eight problems 相似文献
20.
Wireless Networks - In cognitive radio networks (CRN), the secondary users need control channels for negotiating communication parameters and exchanging control messages. Previous studies either... 相似文献