用PT2262实现可遥控式电子密码锁

本文设计的电子密码锁具有保密性好、性价比高的特点.根据用户需要的不同,可选择单用户或多用户工作模式.     

用PT2262实现可遥控电子密码锁

本文设计的电子密码锁具有保密性好，性价比高的特点，根据用户需要的不同，可选择单用户或多用户工作模式。     

基于串级控制的密码锁安全性优化

针对目前应用广泛的普通电子密码锁存在的安全性问题,为了提高现有电子密码锁的安全性,作者采用串级控制方法,在键盘与控制器之间引入接口环节,并运用串并转换技术设计了键盘与锁体的接口。然后作者使用51单片机仿真改进后的电子密码锁与普通密码锁进行比较,验证得出经过改进的电子密码锁的安全性有所提高。     

基于人工噪声的多用户MIMO系统加密算法

当多用户MIMO系统中的用户数多于或等于发射端天线数时,现有的基于人工噪声的物理层加密算法会导致合法用户无法正常接收。为提高此时的多用户MIMO系统的安全性,该文提出一种新的基于人工噪声的多用户MIMO系统加密算法。首先,发送端对多个合法用户进行联合处理,建立多用户联合信道状态矩阵;然后,将联合信道状态矩阵进行奇异值分解,并根据最小的奇异值进行预编码,以消除人工噪声对合法用户的影响;最后,提出一种优化功率分配的方案。仿真结果表明,该算法将多用户MIMO系统的保密容量平均增加了0.1 bit/(s?Hz),从而提高多用户MIMO系统的安全性。     

基于AT89C51单片机的电子密码锁系统设计

随着时代的变迁和科技的进步,人们的生活水平日益提高,传统的家庭防盗系统已经存在较多漏洞。相对以往采用的机械锁而言,现行的电子防盗系统具有安全性高、结构简单和服务质量好等优点,极大的满足了用户的日常需求。本文在电子密码锁系统中运用单片机AT89S52,并融合运用了键盘输入模块、显示模块、声音控制模块这三大模块,旨在设计出符合用户需求的电子密码锁系统。     

数字电子密码锁

针对传统的机械锁的各种缺点和重要部门安全性要求,提出一种基于数字电子技术的密码锁核心电路设计方案,通过此方案设计的密码锁电路不但满足安全性要求,也能够适应特殊环境的使用需求。触发式电子密码锁的设计制作主要应用了数字电子技术的编、译码技术,并通过按键实现密码的设置、修改及识别功能。设计电路主要由集成芯片编、解码电路,轻触式按钮及显示电路组成。     

一种新型红外线遥控智能密码锁

现今遥控防盗锁主要采用电磁波的发射与接收电路。由于成本和技术的限制,在很大的程度上限制了其智能的发展,尤其是采取单调的加密方式,不能在密码的分级管理上采取有效的措施。采用这种电磁波收发电子电路,易受电磁干扰,工作可靠性差,安全性很不理想。还有许多密码锁是使用市电,当停电时密码锁无法正常工作,给用户造成许多不便。该实用新型红外线遥控智能密码锁可靠性强,抗电磁干扰,特别其采用主控CPU电路之后,让密码锁更加智能化,更有利于家庭和车辆安全防盗及使用方便。     

基于FPGA的电子密码锁设计

设计并实现了一种基于FPGA的电子密码锁,具有解锁、报警、修改密码、死锁等功能。利用FPGA器件本身具有的并行性和其逻辑电路的本质,实现了高效、可靠的密码锁设计;采用基础电路加模式控制的设计方法,得到了简单稳定且低冗余的电路结构,节省了逻辑资源;提出了一种冗余编码结合掩码加密的硬件加密方法,使得开锁密码在对外部密码存储器读写的过程中难以被泄露,提高了密码锁的安全性。结果表明,设计的电子密码锁具有稳定高效、简单可靠、安全性高等优点。     

一种多功能电子密码锁设计

设计了一种电子密码锁,通过GSM模块与手机通信实现短信开锁、电话短信报警等功能,通过键盘键入密码可以开锁,能够声光报警,提高了密码锁的安全性以及开锁的灵活性。     

基于红外模块的单片机电子密码锁安全性论证

以单片机为主控单元,结合键盘、LCD显示、AT24C02存储、遥控等外围电路,使密码锁能够在接受用户设定的正确密码时开锁,反之报警提示。用户可随时更改开锁密码以提高安全性。设计中遥控功能更是应用广泛的人性化设计     

CMA-based code acquisition scheme for DS-CDMA systems

In direct-sequence code-division multiple access, a code synchronization must take place before the multiuser detector. As the initial synchronization stage, a code acquisition scheme is used to estimate the relative timing phase for the desired transmission within one chip interval. In this paper, a blind code acquisition scheme using adaptive linear filtering based on a linearly constrained constant modulus algorithm (CMA) is proposed. The uncertainty of a desired user's delay is initially discretized and translated into a number of hypotheses. The lock convergence property of CMA is exploited, where the filter at the steady state can lock onto the desired user while nulling all other interfering users (i.e., a decorrelator). For each delay hypothesis, the filter is initialized as the corresponding shifted spreading sequence of the desired user. It is shown that lock convergence always occurs for the correct hypothesis, while all incorrect hypotheses will be hovered around some saddle regions, given sufficiently small step sizes. Then, the correct hypothesis is the one which has the converged filter to yield the maximum lock onto the desired user, or a maximum output energy     

A two-stage CMA-based receiver for blind joint equalization and multiuser detection in high data-rate DS-CDMA systems

The paper deals with the problem of blind mitigation of intersymbol interference (ISI) as well as multiple-access interference (MAI) in asynchronous high data-rate direct-sequence code-division multiple-access systems. A blind adaptive multiuser receiver based on the constant-modulus algorithm (CMA) is proposed, which demodulates each desired user by exploiting only the knowledge of its spreading code, without requiring estimation of the users's channels and timings. In order to overcome the CMA interference capture problem, which arises in a multiuser scenario, a two-stage adaptive receiver is adopted: In the first stage, partial MAI and ISI suppression is blindly achieved by exploiting the desired user signature structure properties; in the second stage, the residual MAI and the ISI are removed by using the CMA, and the information symbols of the desired user are reliably recovered. Theoretical analysis and simulation results show that the first stage is an effective blind adaptive strategy which allows the CMA detector in the second stage to lock on the desired-user symbol, at a particular delay. The proposed blind receiver achieves a significant performance gain in comparison with existing blind methods.     

Optimal linear space-time spreading for multiuser MIMO communications

In this paper, we study the design of linear dispersion (LD) codes for uplink multiuser channels with multiple antennas at the base station and each mobile unit. In the considered scheme, each user employs LD codes to transmit the data, i.e., the transmitted codeword is a linear combination over space and time of certain dispersion matrices with the transmitted symbols. The linear space-time spreading can also be utilized to separate multiple users at the base station. We propose a simulation-based optimization method together with gradient estimation to systematically design the multiuser linear space-time coding under either optimal or suboptimal receivers. We perform the gradient estimation through the score function method. The proposed method can also be applied to design codes under different fading statistics. Simulation results show that under the optimal maximum-likelihood (ML) receiver, the codes obtained by the new algorithm provides roughly the same performance as the low-dimensional spread modulation, as well as the interference-resistant modulation. Moreover, the new codes perform significantly better with suboptimal multiuser receiver structures.     

基于GPRS彩信模块的多功能家庭安防系统

现有家庭安防系统最大的弊端是不能及时的对报警信息进行有效的验证，从而出现误报、错报的问题。为了克服这个问题，采用彩信图片的形式将报警现场的情况及时地反映到用户的手机屏幕上。此外，为了进一步增强系统的防盗安全性，设计了双重电子锁，该锁采用RFID码感应技术和用户开锁时间规律，有效地克服盗贼用万能钥匙开锁的现象。经试验测试达到了预期的效果。     

Noncoherent decorrelative detection for nonorthogonal multipulsemodulation over the multiuser Gaussian channel

This paper introduces the problem of noncoherent detection for nonorthogonal multipulse modulation in the context of the synchronous multiuser Gaussian channel. Each user sends an M-ary information symbol by transmitting one of M possibly nonorthogonal waveforms. Furthermore, the M signals of one user are allowed to be correlated with the signals of all other users. A key idea proposed here is that of a noncoherent decorrelative receiver front end. Like its counterpart in single-pulse modulation, this front end eliminates multiuser interference. It therefore reduces the multiuser detection problem into decoupled single-user problems over equivalent noise-enhanced single-user channels. Each equivalent single-user channel is rather general and can be described as one where the waveforms employed are not only correlated, but are also of unequal energies. Several new results pertaining to the design and analysis of optimum and suboptimum noncoherent detectors for this single-user channel are obtained. In the multiuser channel, these detectors constitute the post-decorrelative processing units for each user     

Analysis and design of interleavers for iterative multiuser receivers in coded CDMA systems

We deal with the design of interleavers in a coded code-division multiple-access (CDMA) scenario, where at the receiver an iterative turbo-like structure to perform multiuser detection is employed. The choice of the interleavers affects both the maximum-likelihood (ML) performance and the impact of the suboptimality of the iterative receiver. First, heuristic criteria of goodness for a set of interleavers, each assigned to a given active user, are introduced and motivated. One of these criteria is based on the intersection between the equivalent codes seen after the interleavers for each user pair. The design rules are valid for any kind of channel code. In particular, when the channel code used by every user is a terminated convolutional code, a very simple design rule, in the subset of congruential interleavers, is specified. The suitability of an interleaver set to iterative decoding is also treated. The analysis leads to a design rule which is shown to have great importance on the performance of a turbo-like receiver. Numerical results assess the validity of the derived design rules by showing that, for iterative multiuser receivers and reasonable block lengths, the suitability to iterative decoding is more important than the performance optimization.     

Orthogonal multiple access over time- and frequency-selective channels

Suppression of multiuser interference (MUI) and mitigation of time- and frequency-selective (doubly selective) channel effects constitute major challenges in the design of third-generation wireless mobile systems. Relying on a basis expansion model (BEM) for doubly selective channels, we develop a channel-independent block spreading scheme that preserves mutual orthogonality among single-cell users at the receiver. This alleviates the need for complex multiuser detection, and enables separation of the desired user by a simple code-matched channel-independent block despreading scheme that is maximum-likelihood (ML) optimal under the BEM plus white Gaussian noise assumption on the channel. In addition, each user achieves the maximum delay-Doppler diversity for Gaussian distributed BEM coefficients. Issues like links with existing multiuser transceivers, existence, user efficiency, special cases, backward compatibility with direct-sequence code-division multiple access (DS-CDMA), and error control coding, are briefly discussed.     

“互联网+”背景下大学课堂学习效率管理产品的研发与应用

本团队研发的产品是“定时锁机盒”及配套APP“CLOSE”,通过将手机锁在锁机盒里的方式,帮助用户摆脱手机依赖,提高工作和学习效率。定时锁机盒运用物联网技术与APP相连接,用户先在APP上设定锁机时长,打开扫码界面后将手机按指定方式放入盒中完成扫码,锁机盒自动锁定,计时完成后锁机盒将自动开启,用户可以取出手机。在物联网技术蓬勃发展的今天,本产品运用实物与软件相结合的技术,聚焦当下热点社会问题,相应政策号召,紧贴大众实际需求,具有广阔的市场和发展前景。     

Joint Frequency-Domain Multiuser Turbo Equalization with Successive Interference Cancellation for Doubly-Selective Fading Channels

A novel multiuser separation and equalization scheme is proposed for single carrier wireless communication systems integrating frequency-domain (FD) multiuser turbo equalization (MUTE) and successive interference cancellation (SIC). The proposed iterative structure consists of multiple layers of detection, and at each layer the user with strongest power is processed by a frequency-domain multiuser equalizer to yield the soft extrinsic information on the coded bits of that user, which is delivered to a channel decoder after deinterleaving. The extrinsic information gleaned by the decoder is fed back to both the current and previous multiuser equalizers for the next iteration as a-priori information. The soft symbols of the current user are evaluated by the a-posteriori information of coded bits provided by the multiuser equalizer, and the interference reconstructed by the current user’s soft symbols is canceled out from the received signals in frequency domain. The interference-canceled signals are fed forward to subsequent layers for detection of other users. The proposed scheme effectively mitigates multiple access interference and intersymbol interference by an iterative (turbo) detection method. Numerical simulation examples demonstrate that the proposed FD MUTE with SIC outperforms the traditional MMSE multiuser equalizer over the severely doubly-selective channels, and the bit-error-rate performance tends to be better with the increase of iterations.     

一种针对基于人工噪声的MU-MISOME保密通信系统的全新优化方案（英文）

This study investigates artificial noise aided Multiuser Multiple-Input Single-Output(MU-MISO) broadcast wiretap system designs in slow fading channel environment. We adopt a beamforming technique with artificial noise to achieve secure multiuser communication and optimize system performance. To overcome the complexity of this model, a novel optimization scheme using semiclosed-form expressions and Monte Carlo method is employed to derive the relationship between transmission parameters and secu...