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Derya Cavdar H. Birkan Yilmaz Tuna Tugcu Fatih Alagz 《Wireless Communications and Mobile Computing》2012,12(3):277-292
Cognitive radio heralds the next step in the evolution of wireless communications. In this paper, an analytical model for infrastructure based cognitive radio systems is proposed, and its performance is evaluated under bursty traffic scenarios in a multiple cell environment. Performance metrics like probabilities of dropping and blocking for primary and secondary users as well as forced termination and forced frequency handoff for secondary users are investigated, and the analytical model is verified with simulations. In addition to the analytical model, a new resource planning method is proposed to compensate for uneven traffic load distribution. The proposed method considers offered traffic, hop count to the heavily loaded cell, and velocity of mobile users during resource planning and performs better in terms of probability of blocking, dropping, and forced termination. The proposed method is promising in balancing the system performance measures, yet there is room for further improvement for finding a closed formula for the proposed analytical model. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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IP网络性能特征模型分析 总被引:3,自引:0,他引:3
以Internet为代表的IP网络正日益成为一种重要的通信基础设施,但在当前的Internet上支持实时媒体应用仍然是一个难点。为了能够在尽力而为的IP网络上支持多媒体的应用,需要深入地理解网络性能特征。网络性能特征的研究包括对网络进行测量、建模和分析,定量或定性地得出网络的性能指标,从而有效地对网络进行预测、控制和使用。本文对已有的网络性能方面的研究成果进行归纳、总结和验证,得出了IP网络通信平台的基本性能特征模型。 相似文献
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认知无线电中继网络中,认知用户需要成功感知到其所在簇内的主用户频谱空穴后才能成为认知中继节点,且各认知中继节点发射功率受到各自主用户干扰温度限制(ITC)。该文对认知中继节点采用分布式空时编码和解码转发协议时认知用户的中断性能进行了分析;给出了认知用户在干扰温度限制下中断概率的上下界,得出中断概率的上下界在不同干扰温度限下与认知用户归一化数据速率、中继数量和其对主用户检测概率的关系。给出了源节点和频谱感知中继节点在相同干扰温度限下的数值仿真,并对仿真结果进行了分析。 相似文献
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By using spectrum allocation technology of cognitive radio into integrated satellite and terrestrial networks,the satellite communication network can share spectrum with the terrestrial network and improve utilization efficiency of frequency spectrum in the satellite communication system.Firstly,a spectrum resource sharing model in integrated satellite and terrestrial networks was introduced,and the scenery that cognitive satellite downlinks use the vacant spectrum of terrestrial network was analyzed.Then,the interference and signal model was analyzed.Finally,considering different priority types of satellite terrestrial terminals,a spectrum allocation scheme based on priority was proposed,which could ensure the total throughput in satellite downlink communication and increase the throughput of high-priority terrestrial terminals. 相似文献
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Marouane Sebgui Jalal Almhana Slimane Bah Belhaj Elgraini 《Wireless Communications and Mobile Computing》2016,16(15):2238-2252
Dynamic spectrum access policy allows a secondary user (SU) to access a primary user (PU) channel when it is idle. However, the idle state may result from the PU's silent activities, which can be wrongly perceived as an opportunity for the SU to access the channel and lead to “hidden collision” when it effectively tries to access the channel under this condition. At best of our knowledge, this issue has yet to be addressed in the literature. In this paper, we will first define a three‐state model that describes hidden collision conditions, then propose a probabilistic model in which a transient state is added to force the SU to wait a certain period of time before accessing the channel, thereby translating into better protection for the PU. Based on this model and using Carrier Sense Multiple Access/Collision Avoidance protocol, we will evaluate the PU's and SU's throughput and delay with and without transient state as well as the gain in using our approach. Our computation results show a substantial improvement of the PU's throughput from 19.6 to 61.1%. 相似文献
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为了保证认知无线电传感器网络(CRSN)的服务质量(QoS),需精确求解所采用协议的性能边界,为此提出了一种基于随机网络演算(SNC)的QoS性能边界分析方法.以CRSN中的和式增加积式减少(AIMD)拥塞控制机制为评估对象,以通信时延和数据积压为QoS性能指标.根据CR资源传感器的发送速率分布,利用基于矩量母函数(MGF)的随机网络演算推导出AIMD机制的时延和积压边界模型.实验结果表明,不同CRSN场景中的模型计算值都在理论边界范围之内,证明了该边界分析模型具有良好的性能. 相似文献
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A Bayesian network modeling approach for cross media analysis 总被引:1,自引:0,他引:1
Christina Lakka Spiros Nikolopoulos Christos Varytimidis Ioannis Kompatsiaris 《Signal Processing: Image Communication》2011,26(3):175-193
Existing methods for the semantic analysis of multimedia, although effective for single-medium scenarios, are inherently flawed in cases where knowledge is spread over different media types. In this work we implement a cross media analysis scheme that takes advantage of both visual and textual information for detecting high-level concepts. The novel aspect of this scheme is the definition and use of a conceptual space where information originating from heterogeneous media types can be meaningfully combined and facilitate analysis decisions. More specifically, our contribution is on proposing a modeling approach for Bayesian Networks that defines this conceptual space and allows evidence originating from the domain knowledge, the application context and different content modalities to support or disproof a certain hypothesis. Using this scheme we have performed experiments on a set of 162 compound documents taken from the domain of car manufacturing industry and 118 581 video shots taken from the TRECVID2010 competition. The obtained results have shown that the proposed modeling approach exploits the complementary effect of evidence extracted across different media and delivers performance improvements compared to the single-medium cases. Moreover, by comparing the performance of the proposed approach with an approach using Support Vector Machines (SVM), we have verified that in a cross media setting the use of generative rather than discriminative models are more suited, mainly due to their ability to smoothly incorporate explicit knowledge and learn from a few examples. 相似文献
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Web 2.0 has been becoming the new tendency of the Internet development. In order to get better management of web 2.0 network resource and guarantee of service quality, the architecture and the advantages of web 2.0 over Ajax technology is analyzed, and the impact of Ajax on bandwidth performance of web application is discussed. 相似文献
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文章主要讨论了宽带码分多址(WCDMA)网络中无线小区随机接入信道(RACH)的数学建模方法及性能分析.首先介绍了WCDMA的RACH及信息发送方式,然后描述了RACH随机接入过程的时隙ALOHA接入方式,并在此基础上重点分析了RACH数学建模的方法和详细过程,给出了RACH吞吐量的计算公式,最后,对RACH的性能进行了分析. 相似文献
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Data traffic‐based analysis of delay and energy consumption in cognitive radio networks with and without resource reservation 下载免费PDF全文
Mouna Elmachkour Abdellatif Kobbane Essaid Sabir Jalel Ben‐othman Mohammed El koutbi 《International Journal of Communication Systems》2015,28(7):1316-1328
A new opportunistic cross‐layer MAC protocol involving channel allocation and packet scheduling for cognitive radio networks is proposed. Cognitive radio allows secondary users (SUs) to exploit the available portions of the licensed spectrum bands without interfering with primary users. In particular, we consider a cognitive radio system, where SUs are equipped with two transceivers: a control transceiver and a software‐defined radio transceiver. Data traffic characteristics of SUs are considered to ameliorate system performance. So, we propose a mechanism of resource reservation to improve QoS requirements that favors successful SUs to transmit data during x time slots without interfering with primary users. The key novelty of this paper is giving priority for SUs with important data traffic and which frequently solicits data channels to transmit for the remaining time of the ongoing time slot and for the next time slots directly after checking the channel availability. We develop a new analytical model to evaluate delay parameter for two scenarios with and without resource reservation and we then investigate the impact of those scenarios on the energy consumption. We show through simulations that cognitive radio performances increase noticeably with the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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针对LTE系统中多用户下行吞吐量难以预测的问题,从LTE 系统的时域和频域资源出发,结合用户位置、终端类型以及下行MIMO模式等内容,分析了多用户条件下时域和频域调度算法的特点、影响因素和作用过程。并在此基础上建立了多用户下行吞吐量分析和估算模型,进而应用此模型对具体实例进行了预测和分析,从而对多用户性能分析工作起到一定的指导作用。 相似文献
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In order to improve the secrecy performance of communication system and make efficient use of limited spectrum,overlay cognitive radio (OCR) technology was combined with non-orthogonal multiple access (NOMA) technology and the communication model was proposed,in which secondary network realized dynamic switching between assisting primary network communication and secondary network communication by sensing whether the primary user occupied the spectrum or not.Artificial noise (AN) aided technology was used in primary and secondary networks respectively to further improve the secrecy performance of the system.The secrecy performance of the system was studied by deducing the expressions of the primary and secondary network secrecy outage probability and secrecy throughput respectively.The simulation results show that the proposed cognitive cooperative NOMA communication scheme is beneficial in reducing secrecy outage probability and increasing secrecy throughput.Furthermore,the influence of AN power allocation factor on system performance is given. 相似文献
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Fahd Ahmed Khan Kamel Tourki Mohamed‐Slim Alouini Khalid A. Qaraqe 《Wireless Communications and Mobile Computing》2015,15(16):2004-2019
Consider a multi‐user underlay cognitive network where multiple cognitive users concurrently share the spectrum with a primary network with multiple users. The channel between the secondary network is assumed to have independent but not identical Nakagami‐m fading. The interference channel between the secondary users (SUs) and the primary users is assumed to have Rayleigh fading. A power allocation based on the instantaneous channel state information is derived when a peak interference power constraint is imposed on the secondary network in addition to the limited peak transmit power of each SU. The uplink scenario is considered where a single SU is selected for transmission. This opportunistic selection depends on the transmission channel power gain and the interference channel power gain as well as the power allocation policy adopted at the users. Exact closed form expressions for the moment‐generating function, outage performance, symbol error rate performance, and the ergodic capacity are derived. Numerical results corroborate the derived analytical results. The performance is also studied in the asymptotic regimes, and the generalized diversity gain of this scheduling scheme is derived. It is shown that when the interference channel is deeply faded and the peak transmit power constraint is relaxed, the scheduling scheme achieves full diversity and that increasing the number of primary users does not impact the diversity order. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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In this paper, an analytical framework is developed and validated via simulation for statistical estimation of the evolution of the separation between a pair of mobile nodes in an ad hoc network. Simulation results demonstrate that path selection based on minimization of the product of the link statistic significantly outperforms minimum‐hop and fixed threshold‐based ‘path‐stability’ schemes. A hierarchical mobility model integrating the dynamic effects of velocity, group movement and geographic scope is used to generalize the results. Another significant result is the performance enhancements hold in large networks irregardless of the assumptions used for statistical estimation. The effect of merging many independent groups appears to restore independent mobility. Finally, results show that at the highest mobility levels, 90% of the longest surviving paths fail within 60 s. None of the strategies approach this optimal value. This important result suggests that optimal predictive mechanisms alone are insufficient to ensure scalable routing in ad hoc networks. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献