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71.
In order to improve the efficiency and fairness of radio resource utilization,a scheme of dynamic cooperative subcarrier and power allocation based on Nash bargaining solution(NBS-DCSPA) is proposed in the uplink of a three-node symmetric cooperative orthogonal frequency division multiple access(OFDMA) system.In the proposed NBS-DCSPA scheme,resource allocation problem is formulated as a two-person subcarrier and power allocation bargaining game(SPABG) to maximize the system utility,under the constraints of each user’s maximal power and minimal rate,while considering the fairness between the two users.Firstly,the equivalent direct channel gain of the relay link is introduced to decide the transmission mode of each subcarrier.Then,all subcarriers can be dynamically allocated to the two users in terms of their selected transmission mode.After that,the adaptive power allocation scheme combined with dynamic subcarrier allocation is optimized according to NBS.Finally,computer simulation is conducted to show the efficiency and fairness performance of the proposed NBS-DCSPA scheme. 相似文献
72.
An open question about the asymptotic
cost of connecting many processors to a
large memory using three dimensions for wiring
is answered, and this result is used
to find the full cost of several
cryptanalytic attacks. In many cases this full
cost is higher than the accepted complexity
of a given algorithm based on the number of processor
steps. The full costs of several
cryptanalytic attacks are determined, including
Shanks method for computing discrete
logarithms in cyclic groups of prime order n,
which requires n1/2+o(1) processor steps, but,
when all factors are taken into account, has full
cost n2/3+o(1). Other attacks analyzed are
factoring with the number field sieve, generic
attacks on block ciphers, attacks on double
and triple encryption, and finding hash collisions.
In many cases parallel collision search
gives a significant asymptotic advantage over
well-known generic attacks. 相似文献
73.
本文研究基于两跳的协作通信系统中的中继选择问题.为了降低中断概率,传统中继选择方案往往需要引入更多的中继节点参与协作传输,导致系统平均吞吐量下降.为解决上述问题,本文提出了一种新的自适应中继选择方案(ARSS),此方案可以结合两跳的链路信道状况,自适应地选择中继节点及其转发协议.仿真结果表明,与其他中继选择方案相比,本... 相似文献
74.
Most of the Radio Frequency IDentification (RFID) authentication protocols, proposed to preserve security and privacy, are analysed to show that they can not provide security against some passive or active attacks. In this paper, the security of two matrix-based protocols, proposed by Karthikeyan and Nesterenko (KN protocol) and Ramachandra et al. (RRS protocol) that conform to Electronic Product Code Class-1 Generation-2 (EPC Class-1 Gen-2) standard, are investigated. Using the linear relationship of multiplication of matrix and vector, we point out that both protocols can not provide scalability, and they are vulnerable to passive impersonation attack. In addition, both protocols are totally insecure if the adversary can compromise one tag to extract the secrets. A modified lightweight matrix-based authentication protocol is presented, which can resist mainly common attacks on an RFID authentication system including eavesdropping, relay attack, desynchronization attack, impersonation attack and tag tracking attack. The new protocol also has the desirable scalability property and can keep secure under compromising attack. 相似文献
75.
Sensing the spectrum in a reliable and efficient manner is crucial to cognitive radio. To combat the channel fading suffered by the single radio, cooperative spectrum sensing is employed, to associate the detection of multiple radios. In this article, the optimization problem of detection efficiency under the constraint of detection probability is investigated, and an algorithm to evaluate the required radio number and sensing time for maximal detection efficiency is presented. To show the effect of cooperation on the detection efficiency, the proposed algorithm is applied to cooperative sensing using the spectral correlation detector under the Rayleigh flat fading channel. 相似文献
76.
有效性分析对合理制订最优网络动态防御策略至关重要.首先利用随机抽样模型从脆弱性变换角度给出入侵成功概率计算公式,用于刻画变换空间、变换周期及脆弱性数量对网络入侵过程的影响;然后针对单、多脆弱性变换两种情况,分别给出相应的入侵成功概率极限定理并予以证明,同时给出两种情况下的最优变换空间计算方法;仿真结果表明,增大单条入侵路径上依次攻击的脆弱性数量、减小变换周期可持续提高网络动态防御有效性,而增大变换空间初始可以提升网络动态防御有效性,但是由于入侵成功概率会随变换空间的持续增大而逐渐收敛,在入侵成功概率收敛时,有效性无法持续提高. 相似文献
77.
XuBaomin LianWeimin 《电子科学学刊(英文版)》2003,20(3):183-188
The research work presented in this paper is based on the concrete background of the Cooperative Graphics Editor(GGE),allowing two or more persons to remotely deit a graphic document simultaneously.A new concurrency control algorithm based on partial order set is presented,which has fast response and less undo-redo operations as there are no lock mechanisms.It is used to solve inconsistency caused by operation on intersecting graphics concurrently.CGE also possesses a mask strategy to solve inconsistency caused by operation on the same graphic concurrently. 相似文献
78.
查打一体化是当前航空相机的一个主要发展方向,其中一项关键技术为扫描像移的动态、高精度补偿.基于面阵探测器的时间延迟积分(TDI)扫描像移补偿方式相比于光机式的像移补偿方式具有天然的优势,然而当前的面阵探测器TDI像移补偿精度是像素级的,进一步提高查打一体化相机分辨率遇到了瓶颈.针对于此本文首先介绍了查打一体化航空相机工作原理,然后针对帧转移CCD的特性建立了电荷行间转移的数学模型与电荷转移像移的调制传递函数模型,在此基础上提出了一种查打一体化航空相机扫描像移的片上补偿方法,采用该方法可将西相位面阵TDI CCD的像移补偿精度提高至1/2φ像元.最后搭建了实验平台并给出了二、三、四相位面阵TDI CCD电荷转移像移对遥感图像质量的影响,同时也证明了提出的方法能够显著提高图像质量. 相似文献
79.
80.