共查询到17条相似文献,搜索用时 78 毫秒
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机会频谱接入(OSA,Opportunistic Spectrum Access)允许未授权用户在空间域和时域上共享授权频谱,但仅当授权用户没有占用这些频谱时认知用户才能接入。特别地,频谱环境的动态性使MAC协议设计面临着几个重要的问题,即认知用户需要确定何时以什么方式接入哪一个信道发送/接收数据而不影响主用户的通信。从OSA-MAC设计面临的技术挑战出发,对近年来国内外在该方向的研究成果做了总结和分析,并阐述了OSA-MAC设计亟待解决的问题和今后的研究方向。 相似文献
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机会频谱接入(OSA,opportunistic spectrum access)允许未授权用户在空间域和时域上共享授权频谱,但仅当授权用户没有占用这些频谱时认知用户才能接入。另外频谱环境的动态性使MAC协议设计面临着几个重要的问题,即认知用户需要确定何时以什么方式接入哪一个信道发送/接收数据而不影响主用户的通信。从OSA-MAC设计面临的技术挑战出发,对近年来国内外在该方向的研究成果做了总结和分析,并阐述了OSA-MAC设计亟待解决的问题和今后的研究方向。 相似文献
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重复使用一定的TV频段是机会频谱接入的一个典型应用。在认知无线电机会频谱接入中,为了最大化信道的利用,授权用户与认知用户相互协作共同利用信道。文章将授权用户对信道的占用过程模拟为连续时间马尔可夫过程。认知用户在限制其对授权用户的干扰影响条件下,利用等比缩减的策略对信道进行感知,提出一个最优频谱接入策略,提高频谱的利用率。 相似文献
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基于跨层优化的机会频谱接入算 总被引:1,自引:0,他引:1
针对周期性信道感知机会频谱接入系统,首先采用马尔可夫过程对次用户的感知活动进行建模分析,然后结合物理层和MAC层参数提出一个跨层性能指标--有效传输容量,并在最大化有效传输容量准则下提出一种跨层优化机会频谱接入算法,进而分析了机会频谱共享系统可获得的平均有效传输容量.理论分析和仿真结果表明,所提出的跨层优化接入算法性能优于单层优化接入算法,它可以使次用户获得更高的有效传输容量. 相似文献
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认知无线电是一种基于软件无线电的智能通信系统,它能够认知周围环境,并能通过一定的方法相应地改变某些工作参数来实时地适应环境,从而达到提高频谱利用率、缓解频谱资源紧张的目的.授权频段的频谱利用问题是认知无线电实现的关键技术之一.研究了授权频段的两种频谱利用方法:动态频谱接入和基于动态频谱接入模型之一的机会频谱接入. 相似文献
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Yi Liu Shengli Xie Rong Yu Yan Zhang Xi Zhang Chau Yuen 《Wireless Communications and Mobile Computing》2015,15(17):2079-2094
In cognitive vehicular networks (CVNs), spectrum sensing and access are introduced as the promising technologies to fully exploit the underutilized licensed spectrum. Because the sensing ability of a single secondary vehicular user (SVU) is affected by high mobility, dynamic topology, and unreliable wireless environment, collaborative sensing is developed to increase the sensing accuracy and efficiency. Generally, the synchronization is required in the collaborative sensing in CVN. However, it is difficult to keep all SVUs synchronized with others for sensing under the high dynamic network topology, and the sensing overhead of the synchronous cooperative action may be significant. In this paper, we first propose an asynchronous cooperative sensing scheme in which each SVU provides an energy information (EI) that is tagged with location and time information. The sensing decision will be made on account of the EI. Considering the temporal and spatial diversities of each SVU, we assign different weights to each EI and formulate the probabilities of detection and false alarm as the optimization problems to find the optimal weight of each EI. Then, based on the asynchronous sensing, the specifications of the opportunistic spectrum access mechanism are elaborated in both centralized and decentralized CVNs for the sake of practical implementation. We analyze the system performance in terms of achievable throughput and transmission delay. Numerical results show that the proposed scheme is able to achieve substantially higher throughput and lower delay, as compared with existing schemes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Xun Xiao Shucheng Liu Kejie Lu Jianping Wang 《International Journal of Communication Systems》2012,25(7):832-848
Cognitive radio network (CRN) is an emerging technology that can increase the utilization of spectrum underutilized by primary users (PUs). In the literature, most exiting investigations on CRNs have focused on how secondary users (SUs) can coexist harmlessly with the PUs. Despite the importance of such a coexistence issue, it is also crucial to investigate the coexistence of SUs because (i) the PUs usually rarely use the licensed spectrum and (ii) the advantages of CRN will significantly increase the number of SUs in the future. To address this challenging issue, we propose, in this paper, an optimal randomized spectrum access scheme, whose main ideas include the following: (i) an SU shares its sensing results with neighboring SUs and (ii) with the regional sensing results, an SU will access available channels with a non‐uniform probability distribution. We first formulate a multichannel optimal randomized multiple access (MC‐ORMA) problem that aims to maximize the throughput of the CRN; we then develop efficient distributed algorithms to solve the MC‐ORMA problem; we derive the closed‐form value of collision probability for each SU; and finally, we conduct extensive numerical experiments and compare our theoretical analysis with simulation results to demonstrate the advantages of our scheme. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Hanna Bogucka 《Wireless Communications and Mobile Computing》2012,12(5):431-444
In this paper, we consider the Orthogonal Frequency Division Multiple Access (OFDMA)‐based Opportunistic Radio (OR) networks, in which the nodes are able to adopt a subset of subcarriers (SCs) available in the considered network area, as well as the transmission rate and power associated with these SCs either for their uplink or downlink transmission. The idea of our top‐down approach to the efficient and rational spectrum utilization is to allow each node to first optimize the resources acquisition at OSI‐layer 2 (top), where the competition of nodes for available common resources is observed, and then to autonomously optimize the transmission parameters accounting for the radio channel conditions at the physical (down) layer. We assume that the nodes act independently based on their local channel quality information, which contains an error. In these optimization tasks, the efficiency and rationality mechanisms have been introduced in the objective (utility) functions, which reflect the throughput achieved, the network potential to serve multiple nodes, as well as pricing of resources and the power economy. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Xueyuan Jiang Kai‐Kit Wong Yangyang Zhang David J. Edwards 《Wireless Communications and Mobile Computing》2015,15(2):340-353
To utilize spectrum resources more efficiently, dynamic spectrum access attempts to allocate the spectrum to users in an intelligent manner. Uncoordinated sharing with cognitive radio (CR) users is a promising approach for dynamic spectrum access. In the uncoordinated sharing model, CR is an enabling technology that allows the unlicensed or secondary users to opportunistically access the licensed spectrum bands (belonging to the so‐called primary users), without any modifications or updates for the licensed systems. However, because of the limited resources for making spectrum observations, spectrum sensing for CR is bound to have errors and will degrade the grade‐of‐service performance of both primary and secondary users. In this paper, we first propose a new partial spectrum sharing policy, which achieves efficient spectrum sharing between two licensed networks. Then, a Markov chain model is devised to analyze the proposed policy considering the effects of sensing errors. We also construct a cross‐layer design framework, in which the parameters of spectrum sharing policy at the multiple‐access control layer and the spectrum sensing parameters at the physical layer are simultaneously coordinated to maximize the overall throughput of the networks, while satisfying the grade‐of‐service constraints of the users. Numerical results show that the proposed spectrum sharing policy and the cross‐layer design strategy achieve a much higher overall throughput for the two networks. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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In this letter, a modified 802.11‐based opportunistic spectrum access is proposed for single‐channel cognitive radio networks where primary users operate on a slot‐by‐slot basis. In our opportunistic spectrum access, control frames are used to reduce the slot‐boundary impact and achieve channel reservation to improve throughput of secondary users. An absorbing Markov chain model is used to analyze the throughput of secondary users. Simulation results show that the analysis accurately predicts the saturation throughput. 相似文献
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This article proposes a novel dynamic spectrum sharing scheme in distributed multi-band cognitive radio networks. A non-cooperative game has been utilized to model the spectrum sharing among secondary base stations (SBSs). A distributed joint spectrum detection and power allocation algorithm is designed for maximizing the downlink throughput of secondary networks. Simulation results demonstrate that the proposed algorithm converges fast and achieves a better throughput performance than uniform threshold case. Meanwhile, the convergence of algorithm is proved by Nikaido-Isoda (N-I) function method. 相似文献
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Song LiuAuthor Vitae 《Ad hoc Networks》2012,10(5):831-844
Dynamic spectrum access has been proposed as a means to share scarce radio resources, and requires devices to follow protocols that access spectrum resources in a proper, disciplined manner. For a cognitive radio network to achieve this goal, spectrum policies and the ability to enforce them are necessary. Detection of an unauthorized (anomalous) usage is one of the critical issues in spectrum etiquette enforcement. In this paper, we present a network structure for dynamic spectrum access and formulate the anomalous usage detection problem using statistical significance testing. The detection problem investigated considers two cases, namely, the authorized (primary) transmitter is (i) mobile and (ii) fixed. We propose a detection scheme for each case by exploiting the spatial pattern of received signal energy across a network of sensors. Analytical models are formulated when the distribution of the energy measurements is given and, due to the intractability of the general problem, we present an algorithm using machine learning techniques to solve the general case when the statistics of the energy measurements are unknown. Our simulation results show that our approaches can effectively detect unauthorized spectrum usage with a detection probability above 0.9 while keeping the false alarm rate less than 0.1 when only one unauthorized radio is present, and the detection probability is even higher for more unauthorized radios. 相似文献