软件无线电的研究现状综述

软件无线电因为它的开放性强,兼容性高,在航空航天,多频段、多用户、多模兼容以及互联系统有着广泛的应用前景;文中简要介绍了软件无线电的背景,着重对其关键技术及研究难点提炼与归纳,最后对软件无线电在军事通信、个人移动通信的应用与发展趋势进行了分析及总结。     

Heterodyne mixing and polarization diversity techniques in radio over fiber system with high sensitivity and dispersion tolerance

We propose and experimentally demonstrate the heterodyne mixing and polarization diversity tech- niques in radio over fiber (ROF) systems with the advantages of high sensitivity and dispersion endurance. The generation of 2.5 Gb/s optical DPSK and PSK signals, fiber propagation and wireless transmission over 15 GHz subcarrier are illustrated with very low sensitivity of -26 and -32 dBm, respectively. Moreover, based on the wireless polarization diversity techniques, we successfully performed the t...     

Some improved results on communication between information systems

To study the communication between information systems, Wang et al. [C. Wang, C. Wu, D. Chen, Q. Hu, C. Wu, Communicating between information systems, Information Sciences 178 (2008) 3228-3239] proposed two concepts of type-1 and type-2 consistent functions. Some properties of such functions and induced relation mappings have been investigated there. In this paper, we provide an improvement of the aforementioned work by disclosing the symmetric relationship between type-1 and type-2 consistent functions. We present more properties of consistent functions and induced relation mappings and improve upon several deficient assertions in the original work. In particular, we unify and extend type-1 and type-2 consistent functions into the so-called neighborhood-consistent functions. This provides a convenient means for studying the communication between information systems based on various neighborhoods.     

基于PIC的激光吉他设计

激光光源作为新一代的能量光源,以其极好的聚光特性,在应用中有着不可比拟的优势。本文介绍了一种基于PIC单片机的激光吉他设计方案,提出了系统构架,阐述了软硬件的实现方式。该设计方案以激光代替传统物质弦,在具备强大娱乐性的同时,也极大便利了操作,提高了演奏准确性。     

A novel Parzen probabilistic neural network based noncoherent detection algorithm for distributed ultra-wideband sensors

Ultra-wideband (UWB) has been widely recommended for significant commercial and military applications. However, the well-derived coherent structures for UWB signal detection are either computationally complex or hardware impractical in the presence of the intensive multipath propagations. In this article, based on the nonparametric Parzen window estimator and the probabilistic neural networks, we suggest a low-complexity and noncoherent UWB detector in the context of distributed wireless sensor networks (WSNs). A novel characteristic spectrum is firstly developed through a sequence of blind signal transforms. Then, from a pattern recognition perspective, four features are extracted from it to fully exploit the inherent property of UWB multipath signals. The established feature space is further mapped into a two-dimensional plane by feature combination in order to simplify algorithm complexity. Consequently, UWB signal detection is formulated to recognize the received patterns in this formed 2-D feature plane. With the excellent capability of fast convergence and parallel implementation, the Parzen Probabilistic Neural Network (PPNN) is introduced to estimate a posteriori probability of the developed patterns. Based on the underlying Bayesian rule of PPNN, the asymptotical optimal decision bound is finally determined in the feature plane. Numerical simulations also validate the advantages of our proposed algorithm.     

Architectural design and FPGA implementation of radix-4 CORDIC processor

A new scaled radix-4 CORDIC architecture that incorporates pipelining and parallelism is presented. The latency of the architecture is n/2 clock cycles and throughput rate is one valid result per n/2 clocks for n bit precision. A 16 bit radix-4 CORDIC architecture is implemented on the available FPGA platform. The corresponding latency of the architecture is eight clock cycles and throughput rate is one valid result per eight clock cycles. The entire scaled architecture operates at 56.96 MHz of clock rate with a power consumption of 380 mW. The speed can be enhanced with the upgraded version of FPGA device. A speed-area optimized processor is obtained through this architecture and is suitable for real time applications.     

T-MPLS网络互通问题分析及解决方案

随着数据流量的不断增长及其高突发性,基于SDH技术的传送网逐渐显示出不可解决的劣势.下一代传送网将被基于分组的传送技术所垄断,T-MPLS是一种新的基于分组传送的技术,目前T-MPLS主要定位在城域传送网络,并逐渐向核心网络部分进行扩张.本文基于ITU-T所定义的T-MPLS框架体系结构,结合已有的基于MPLS技术的组网方式,分析了T-MPLS未来的应用前景,并给出了未来传送网络可行的演进模型.     

指定验证者签名方案的安全性分析

对Kang等人和张学军提出的2个基于身份的指定验证者签名方案(Kang方案和Zhang方案)进行安全性分析,指出在Kang方案中,非指定验证者也可以验证签名的有效性,不能抵抗伪造攻击和授权攻击,Zhang方案也不满足不可伪造性、强壮性和不可授权性。     

基于认证协议的Web单点登录优化设计

针对Kerberos认证协议Web环境中进行单点登录存在的安全隐患,基于Schnorr协议的挑战/响应方式,结合Secure Cookies、HttpSession解决Web环境下HTTP协议的无状态性及服务器间的安全会话。实验结果表明,该方案性能稳健,响应速度快,防攻击力强,具有良好的实用价值和应用前景。     

多服务WiMAX系统的调度与资源分配策略

基于IEEE802.16标准的WiMAX技术已成为宽带无线接入的主要技术,IEEE802.16标准没有规定调度和资源分配策略,网络运营商可以自行选择。根据用户需求并考虑信道条件的影响,提出基于NS2的扩展WiMAX系统级仿真平台,给出一种公平有效的调度与资源分配策略。仿真结果证明该策略可以满足多种服务流的QoS需求并最大化系统吞吐量。