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911.
The commonly used models for shadowed fading channels arise by compounding the Nakagami distribution with others such as the
log-normal and gamma distributions. A distribution that is more flexible than the Nakagami distribution is the well known
Weibull distribution. In this paper, we derive a collection of generalized models for shadowed fading channels by compounding
the Weibull distribution with other distributions belong to some fifteen flexible families. We also illustrate the superior
performance of these models over the standard Nakagami models. 相似文献
912.
An improved key distribution mechanism for large-scale hierarchical wireless sensor networks 总被引:3,自引:0,他引:3
Wireless sensor networks are often deployed in hostile environments and operated on an unattended mode. In order to protect the sensitive data and the sensor readings, secret keys should be used to encrypt the exchanged messages between communicating nodes. Due to their expensive energy consumption and hardware requirements, asymmetric key based cryptographies are not suitable for resource-constrained wireless sensors. Several symmetric-key pre-distribution protocols have been investigated recently to establish secure links between sensor nodes, but most of them are not scalable due to their linearly increased communication and key storage overheads. Furthermore, existing protocols cannot provide sufficient security when the number of compromised nodes exceeds a critical value. To address these limitations, we propose an improved key distribution mechanism for large-scale wireless sensor networks. Based on a hierarchical network model and bivariate polynomial-key generation mechanism, our scheme guarantees that two communicating parties can establish a unique pairwise key between them. Compared with existing protocols, our scheme can provide sufficient security no matter how many sensors are compromised. Fixed key storage overhead, full network connectivity, and low communication overhead can also be achieved by the proposed scheme. 相似文献
913.
In this article, a method based on max signal interference noise ratio (SINR) criterion is proposed, to mitigate the interuser interference for downlink multiuser spatial multiplexing multi-input multi-output (MIMO) systems.Unlike the zero forcing (ZF) scheme in which the SNR is decreased when the interference is eliminated completely, max SINR method makes a compromise between noise and interuser interference.When the number of substreams is larger than the difference between the number of base station antennas and the sum of interference mobile station antennas, the ZF is infeasible.An existing coordinated TX-RX block diagonalization (COOR BD) method uses preprocessing at the receiver to cancel the interuser interference.However, it cannot obtain more receive diversity gain because of the preprocessing.Analysis and simulation show that the max SINR scheme has better performance than the ZF method.Moreover, when the ZF is infeasible, the max SINR scheme can obtain more receive diversity gain than COOR BD in the two-user case. 相似文献
914.
Long-range dependence, short-range dependence and marginal distribution are three key statistical features for incoming traffic, which have a serious impact on network performance. This paper respectively, studies their characteristics during traffic shaping at the edge node in synchronous optical packet-switched networks and highlights the functions of the First-Come-First- Service (FCFS) schedule queue for various offered loads and assembly parameters, including normalized timeout and normalized threshold. Simulation results demonstrate that under light-medium load the FCFS schedule queue works as a low pass filter, i.e., the statistical features before and after the FCFS schedule queue is nearly the same and each of the statistical features approximately follows the same trend. Heavy load drives the FCFS schedule queue into an overload or saturation state and the three statistical features all exhibit different behavior. By adjusting the assembly parameters, the deficiency can be modified. 相似文献
915.
916.
车载通信方舱供电系统的设计与应用 总被引:2,自引:0,他引:2
结合工程实例,探讨如何设计高可靠性、安全的车载通信方舱不间断供电系统。由于车载通信方舱供电系统兼顾市电/电站集中供电方式,要确保通信系统稳定可靠、不间断地实施通信指挥,供电系统的设计尤为重要,除了满足一般供电系统的功能外,还应具有良好的机动性、环境适应性以及安全可靠等技术指标要求。文中从供电系统设计原则、设计过程等方面介绍了供电系统的设计方式,并分析了不间断电源的选型和蓄电池容量的选择等问题。 相似文献
917.
WIMAX系统中的多天线技术及应用 总被引:2,自引:0,他引:2
WiMAX(全球互通微波接入)技术近年来发展迅速,逐渐成为宽带无线接入技术的热点之一。WiMAX系统能够实现高于2bps/Hz的频带利用率。为了增加覆盖范围和系统的可靠性,IEEE802.16标准支持Alamouti方案的空时码(STC)、自适应天线(AAS)和多输入多输出(MIMO)技术在内的多天线技术。多天线技术的应用能显著地提高系统容量和频谱利用率,从而大大增强WiMAX技术的竞争力。 相似文献
918.
919.
Bao-Long Liang Ji-Suo Wang Hong-Yi Fan 《International Journal of Theoretical Physics》2007,46(7):1779-1785
Wigner function in phase space has its physical meaning as marginal probability distribution in coordinate space and momentum
space respectively, here we endow the Wigner function with a new physical meaning, i.e., its marginal distributions’ statistical
average for q
2/(2C) and p
2/(2L) are the energy stored in capacity and in inductance of a mesoscopic L-C circuit at finite temperature, respectively.
PACS numbers: 03.65.-w, 73.21.-b 相似文献
920.
Using results for the distribution of perimeters of random polygons arising from random lines in a plane, we obtain new analytic
approximations to the distributions of areas and local line densities for random polygons and compute various limiting properties
of random polygons. Using simulation, we show that the lengths of adjacent sides of polygons generated by random line processes
in the plane are correlated with ρ=0.616±0.001. 相似文献