共查询到20条相似文献,搜索用时 734 毫秒
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《Wireless Communications, IEEE Transactions on》2008,7(8):3000-3012
Node cooperation is an emerging and powerful solution that can overcome the limitation of wireless systems as well as improve the capacity of the next generation wireless networks. By forming a virtual antenna array, node cooperation can achieve high antenna and diversity gains by using several partners to relay the transmitted signals. There has been a lot of work on improving the link performance in cooperative networks by using advanced signal processing or power allocation methods among a single source node and its relays. However, the resource allocation among multiple nodes has not received much attention yet. In this paper, we present a unified crosslayer framework for resource allocation in cooperative networks, which considers the physical and network layers jointly and can be applied for any cooperative transmission scheme. It is found that the fairness and energy constraint cannot be satisfied simultaneously if each node uses a fixed set of relays. To solve this problem, a multi-state cooperation methodology is proposed, where the energy is allocated among the nodes state-by-state via a geometric and network decomposition approach. Given the energy allocation, the duration of each state is then optimized so as to maximize the nodes utility. Numerical results will compare the performance of cooperative networks with and without resource allocation for cooperative beamforming and selection relaying. It is shown that without resource allocation, cooperation will result in a poor lifetime of the heavily-used nodes. In contrast, the proposed framework will not only guarantee fairness, but will also provide significant throughput and diversity gain over conventional cooperation schemes. 相似文献
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面向绿色无线通信的基站体系结构 总被引:2,自引:1,他引:1
无线网络的耗能主要来自于基站系统。对无线通信系统中的基站系统结构进行有效地规划和部署,能达到降低能源消耗、实现绿色通信的目的。软件无线电技术的发展为无线基站的绿色演进提供了途径。基于软件无线电技术,文章提出一种可以有效提高通信系统能效、更为绿色环保的基站体系结构,能够更好地实现无线通信系统的绿色演进。 相似文献
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《Wireless Communications, IEEE Transactions on》2009,8(8):3961-3968
In this letter, the average bit-error rate (BER) performance is analyzed for uncoded decode-and-forward (DF) cooperative diversity networks. We consider two typical networks: a single-relay cooperative network with the direct sourcedestination link and a two-relay cooperative network with the direct source-destination link, under dissimilar network settings, i.e., the fading channels of different relay branches may have different variances. We first derive a closed-form approximate average BER expression of binary signallings including noncoherent binary frequency shift keying (BFSK), coherent BFSK, and coherent binary phase shift keying (BPSK), for the singlerelay network. We then generalize our analysis to the two-relay network, and a closed-form approximate average BER expression for binary signallings is derived. We also show that our BER expressions can be considered as generalizations of previously reported results in the literature. Throughout our analysis, only one approximation, so-called the piecewise-linear approximation, is made. Simulation results are in excellent agreement with the theoretical analysis, which validates our proposed BER expressions. 相似文献
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Differential unitary space time modulation (USTM) is identified as one of the best non-coherent technique for future 5th generation mobile networks. Two or more nodes with single antennas cooperate with each other to form a cooperative multiple-input–multiple-output network. In, this paper we examine the use of differential cooperative USTM that avoids channel estimation and also prolong the lifetime of wireless sensor network. Aiming at minimizing the energy consumption per bit we form a differential cooperative energy minimization algorithm by optimally selecting the number of cooperative nodes and finding the route that consumes minimum energy. 相似文献
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Vasileios K. Sakarellos Maria Chortatou Dimitrios Skraparlis Athanasios D. Panagopoulos John D. Kanellopoulos 《Journal of Infrared, Millimeter and Terahertz Waves》2011,32(4):496-505
Extremely high frequency (EHF) bands above 50 GHz have been proposed to be used as backhaul links of modern cellular mobile
networks. They provide interconnectivity between the base stations and the core network. In this paper, we propose the employment
of cooperative techniques in backhaul networks. More specifically, the outage performance analysis of a simple cooperative
diversity system operating at EHF bands is presented. The destination node combines the direct link with the signal received
through a regenerative relay using selection combining. A combined statiform and convective model of rainfall rate for the
rain attenuation prediction is considered. The correlation properties and the joint statistics among the microwave paths are
also calculated. Numerical results present the impact of the geometrical parameters and the climatic conditions on the outage
performance. 相似文献
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无线网状网已经成为无线宽带通信领域的研究热点,但是基于交换技术的无线网状网因为其将整个网络看作是一个IP子网而无法适用于大范围的覆盖。在无线链路中采用协作中继,可以提高无线链路的传输速率及传输可靠性。同时采用基于网络层路由技术的无线网状网技术,可以实现整个无线网状网的频谱效率提升和厂域覆盖。不过,由于标准化、关键技术研究以及产业化推进方面还存在许多问题,使得协作中继技术在无线网状网中的应用面临着巨大挑战。 相似文献
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Qun Yu 《Wireless Personal Communications》2013,73(3):949-966
Cooperative cognitive radio networks are new cognitive radio paradigm. Cooperative communication approaches, such as cooperative spectrum sensing and cooperative spectrum sharing, are playing key roles in the development of cognitive radio networks. To achieve the high performance, a cooperative cognitive communication framework is often used to model various cooperative spectrum sensing or sharing scenarios. However, its implementation faces numerous challenges due to the complexity of mobility and traffic models, the needs of dynamic spectrum access, the heterogeneous requirements from different users, and the distributed structure of the network. Fortunately, cooperative game theory can be used to formulate and model the interactions among licensed and unlicensed users for spectrum sensing and spectrum sharing to efficiently allocate spectrum resource in the highly dynamic and distributed radio environment. In this paper, we first present the cooperative communication technologies and describe their existing challenges, then introduce different game solutions, after that, we discuss several cooperative game strategies, and analyze the associated their applications in cognitive radio networks, at final, some open directions for future research on economic strategies in cooperative communication in cognitive radio networks are proposed. 相似文献
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Capacity bounds for Cooperative diversity 总被引:3,自引:0,他引:3
Host-Madsen A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(4):1522-1544
In a cooperative diversity network, users cooperate to transmit each others' messages; to some extent nodes therefore collectively act as an antenna array and create a virtual or distributed multiple-input multiple-output (MIMO) system. In this paper, upper and lower bounds for the information-theoretic capacity of four-node ad hoc networks with two transmitters and two receivers using cooperative diversity are derived. One of the gains in a true MIMO system is a multiplexing gain in the high signal-to-noise ratio (SNR) regime, an extra factor in front of the log in the capacity expression. It is shown that cooperative diversity gives no such multiplexing gain, but it does give a high SNR additive gain, which is characterized in the paper 相似文献
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Asymptotic performance analysis of amplify-and-forward cooperative networks in a nakagami-m fading environment 总被引:1,自引:0,他引:1
This letter analyzes the performance of repetitionbased cooperative wireless networks using amplify-and forward relaying. The network consists of a source, R parallel relays, and a destination, and the channel coefficients are distributed as independent, non-identical, Nakagami-m. The approximated average symbol error rate (SER) is investigated. For sufficiently large SNR, this letter derives a close-form average SER when m is an integer. The simplicity of the asymptotic results provides valuable insights into the performance of cooperative networks and suggests means of optimizing them. We also use simulation to verify the analytical results. Results show that the derived error rates are tight approximations particularly at medium and high SNR. 相似文献
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Comparative performance analysis of cooperative and multi dual‐hop relay networks using MGF approach
Muhammad Asshad Adnan Kavak Kerem Küük Sajjad Ahmad Khan 《International Journal of Communication Systems》2020,33(15)
In this paper, we analyzed and compared the performance of cooperative diversity systems such as cooperative and multi dual‐hop networks with non‐regenerative relay nodes. The contributions of this study are twofolds. Firstly, analytical expressions of outage probability Pout and average symbol error rate ASER are derived using moment generating function (MGF) analysis of the received SNR with the assumption that the channel experiences Weibull fading and the best relay selection is used. Then, using the analytical results, comparative performance evaluation of cooperative and multi dual‐hop relay networks is done for varying number of relay nodes and different receive diversity schemes such as maximal ratio combining (MRC) and selection combining (SC). The results show that the cooperative relay network has better performance than a multi dual‐hop relay network in terms of Pout and ASER. The results also show that the multi dual‐hop network can achieve the same performance as the cooperative network with the requirement that it needs the deployment of three times more relay nodes. 相似文献
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Complex networks have been widely studied. Recently, many results show that the degree dis-tributions of some large networks follow the form of power-law and these networks possess better robust-ness against random nodes failure. As an effective technology on combating the channel fading, wireless co-operative communication is becoming one of the most important methods to improve the wireless communi-cation performances. In this paper, the complex network models based on cooperative communication and non-cooperative communication are established; and the degree distribution properties for them are studied. The simulation results show that the degree distributions of these networks also follow the form of power-law, which means that the addition of cooperative communication links will not change the property of degree distribution and then these networks will possess better robustness against random nodes failure as well. 相似文献
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In this letter, we use power and rate adaptation to maximize the throughput in cooperative relay networks when limited feedback links to the transmitter nodes exist. We observe that, for a finite rate of feedback, the throughput maximizing outage probability can be relatively high. This suggests using higher rate codes and allowing some outages in an effort to increase the overall network throughput. Our analysis also reveals that the relaying transmission paradigm offers significant throughput gains over direct transmission for any rate of the feedback link. Our work not only demonstrates the power of cooperative coding, but also suggests the importance of network protocols incorporating feedback to allow for throughput maximization 相似文献
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The self-similarity nature of network traffic has been discovered to be a ubiquitous phenomenon in communication networks; meanwhile, heterogeneous wireless cooperative relay networks have received considerable interests in both academia and industry fields. The mechanism of cooperative relay selection is very essential for the design of heterogeneous wireless relay networks. In this paper, based on the self-similar nature of network traffic in heterogeneous wireless cooperative relay network, we propose a new relay selection mechanism called conditional relay selection which can effectively decrease the system outage probability. Compared to conventional relay selection mechanism, the proposed mechanism considers the traffic queue condition of the relay nodes rather than just comparing the signal-to-noise ratio (SNR). Through extensive comparisons with traditional cooperative relay selection mechanisms, the proposed scheme can significantly improve the system outage probability. 相似文献
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Reyhaneh Changiz Hassan Halabian F. Richard Yu Ioannis Lambadaris Helen Tang 《Wireless Communications and Mobile Computing》2014,14(15):1450-1470
In cooperative wireless networks, relay nodes are employed to improve the performance of the network in terms of throughput and reliability. However, the presence of malicious relay nodes in the network may severely degrade the performance of the system. When a relay node behaves maliciously, there exists a possibility that such a node refuses to cooperate when it is selected for cooperation or deliberately drops the received packets. Trust establishment is a mechanism to detect misbehaving nodes in a network. In this paper, we propose a trust establishment method for cooperative wireless networks by using Bayesian framework. In contrast with the previous schemes proposed in wireless networks, this approach takes the channel state information and the relay selection decisions into account to derive a pure trust value for each relay node. The proposed method can be applied to any cooperative system with a general relay selection policy whose decisions in each cooperative transmission are independent of the previous ones. Moreover, it does not impose additional communication overhead on the system as it uses the available information in relay selection procedure. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Cooperative communications have been proposed to exploit the spatial diversity gains inherent in multiuser wireless systems without the need of multiple antennas at each node. This is achieved by having the users relay each others messages and thus forming multiple transmission paths to the destination. In resource constrained networks, such as wireless sensor networks, the advantages of cooperation can be further exploited by optimally allocating the energy and bandwidth resources among users based on the available channel state information (CSI) at each node. In the first part of this article, we provide a tutorial survey on various power allocation strategies for cooperative networks based on different cooperation strategies, optimizing criteria, and CSI assumptions. In the second part, we identify the similarities between cooperative networks and several sensor network applications that utilize collaboration among distributed sensors to achieve the system goal. These applications include decentralized detection/estimation and data gathering. The techniques developed in cooperative communications can be used to solve many sensor network problems 相似文献
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Several scenarios to deliver multimedia streams in wireless multi-hop networks, as in the wireless metropolitan area network (WMAN) environment, are considered and examined. Those scenarios considered in this paper are not new but they are examined in a new environment where the system is benefited from path diversity and cooperative diversity. By simulation, we examine those scenarios in an orthogonal frequency-division multiple access (OFDMA)-based wireless network. The simulation results demonstrate how much path diversity and cooperative diversity improve the performance in average sense. We also discuss open research issues on resource utilization in emerging wireless networks. 相似文献