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数字正交FM解调方案门限效应的研究 总被引:1,自引:0,他引:1
介绍了FM解调方案的门限效应。针对传统调频解调方案中的解调门限值高以及降低解调门限的方案难以实现的不足,在研究传统模拟调频解调方案的基础上,分析了数字FM解调方案的门限性能。理论推导证明,数字正交FM解调方案的门限效应低于模拟解调方案。因此,可以采用数字正交解调方案降低其解调门限,而不需采用较难设计和控制的反馈系统,这极大地降低了调频系统实现的复杂度。最后计算机仿真的结果显示,该方案比传统模拟解调方案门限约低2dB。 相似文献
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目前实现DDS函数信号发生器的方式有MCU+DDS芯片方案、DSP+DDS芯片方案、MCU+FPGA方案、RAM+FPGA方案和SOPC方案。本文采用SOPC方案实现DDS函数信号发生器。 相似文献
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Harn和Lin最近提出了一种无单向函数的多重密钥协同认证协议(H—L方案)。Yen和Joye发现H—L方案存在安全性弱点,并提出了一种改进的协议方案(Y—J方案)。而Wu,He和Hsu指出Y—J方案仍然存在安全性问题,是不安全的。进而利用单向杂凑函数给出了新的方案(W—H—H方案),增强了Y—J方案和H—L方案中的交互认证的安全性,但这违背了最初H—L方案不利用单向函数的原则。本文给出了一种新的改进协议方案,不利用单向函数,仍可保证协议的安全性。 相似文献
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分析了隧道群间隙及短隧道GSM-R系统常用的漏缆贯通覆盖方案,指出方案存在的问题,在此基础上提出了天线覆盖优化方案,并在对两种方案进行分析比较的基础上提出了优化设计方案。研究了隧道长度、隧道群间距和GSM-R系统覆盖方案的关系,针对不同类型的隧道群间隙及短隧道提出了GSM-R系统覆盖方案。 相似文献
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基于因子分解和离散对数的动态秘密分享方案 总被引:2,自引:0,他引:2
该文提出了一个安全性基于离散对数与因子分解的动态秘密分享方案.它具有如下优点:(1)系统更新分享的秘密时,无需更新分享的子秘密,即子秘密可重复使用;(2)当系统增删成员时,无需变更其他成员的子秘密;(3)当某个成员的子秘密泄露时,系统只需为该成员重新分配子秘密而不必更改其他成员的子秘密;(4)防止欺诈;(5)通信量较少,工作效率高. 相似文献
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鉴于量子密码在密钥分配方面取得的巨大成功,人们也在尝试利用量子性质来设计其他各类密码协议。匿名认证密钥交换就是一类尚缺乏实用化量子实现途径的密码任务。为此,该文提出一个基于量子不经意密钥传输的量子匿名认证密钥交换协议。它在满足用户匿名性和实现用户与服务器双向认证的前提下,为双方建立了一个安全的会话密钥。该协议的安全性基于量子力学原理,可以对抗量子计算的攻击。此外,该协议中服务器的攻击行为要么无法奏效,要么能够与外部窃听区分开(从而被认定为欺骗),因此服务器通常不敢冒着名誉受损的风险来实施欺骗。 相似文献
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Ryo Takai Shoya Uchida Akihiro Sato Mamiko Inamori Yukitoshi Sanada 《Wireless Personal Communications》2014,77(1):553-569
Overlapped FFT based energy detection has been proposed as a signal detection scheme in dynamic spectrum access. The overlapped FFT scheme increases the number of FFT frames to reduce the variance of squared noise and improve the detection probability. This paper evaluates the performance of the energy detection with overlapped FFT through experiments. In the experiments, different from the assumption in computer simulation of previous researches, a fixed distortion component caused by a direct current offset is observed. It is shown that the overlapped FFT scheme also works effectively under the existence of the fixed distortion. Numerical results obtained through the experiments show that the overlapped FFT scheme improves the detection probability by up to 0.15 with the noise and the fixed distortion component. The variance of the squared noise also reduces with the overlapped FFT scheme as it is expected in theoretical analysis when the fixed distortion is negligible. 相似文献
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A new optical FSK heterodyne detection scheme is proposed and demonstrated. This scheme uses an optical image rejection mixer. The intermediate frequency bandwidth is the same as ASK heterodyne detection while equalling dual filter FSK detection receiver sensitivity.<> 相似文献
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Shoya Uchida Akihiro Sato Mamiko Inamori Yukitoshi Sanada Mohammad Ghavami 《Wireless Personal Communications》2014,79(2):987-1002
Overlapped FFT has been proposed as a signal detection scheme in dynamic spectrum access to reduce the variance of the noise and improve the detection probability. However, the improvement of the detection probability in the conventional overlapped FFT is bounded with the upper limit of the overlap ratio. This paper proposes a new overlapped FFT scheme using additional frames. In the proposed scheme, in addition to the original FFT frames, new frames that consist of multiple subframes with non-continuous samples are constructed and included. It can realize the increase of the number of the FFT frames and the improvement of the detection probability compared with the conventional scheme. Numerical results through computer simulation show that the proposed scheme improves the detection probability by up to 0.07. On indoor channel models the proposed scheme also improves the detection probability. In addition, it is clarified that as the delay spread increases the detection probability reduces due to the correlation between the frames. 相似文献
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Youngmin Kim Pingping Shang Sooyoung Kim Kwonhue Choi 《Wireless Communications and Mobile Computing》2013,13(18):1612-1620
We propose a very simple and efficient soft linear multi‐input multi‐output (MIMO) detection scheme. The detection process is divided into two separate problems. The proposed scheme first detects MIMO symbols using conventional linear detection methods and produces soft bit information using a simple soft demapping method. Next, we refine the soft information by accounting for uneven post‐detection noise variance across MIMO layers. From the simulation result investigated in this paper, we first emphasize that powerful channel coding may suppress the differences of diversity gains among various MIMO detection schemes. This implies that the channel decoding operation may not be transparent to performance gain that resulted from MIMO detection process. The proposed scheme concentrates on accurate estimation of soft post‐MIMO detected information in a very simple manner, rather than concentrating on a complex MIMO detection scheme prior to decoding process. In combination with turbo codes, the proposed scheme produces comparable performance to maximum likelihood detection, even with the simplest scheme such as zero forcing detection, with drastically reduced complexity. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献