The implementation of channel diversity in mobile software radio receivers

A novel channel diversity concept is proposed and demonstrated, which avoids receiving signal deterioration due to multipath fading in mobile receivers. The system is based on coherent superposition of the signals received from several transmitters supplying the same information at different frequencies. Based on a software radio architecture this concept may increase the quality of mobile reception in modern car receivers considerably. Compared with multiantenna-receivers which overcome the multipath fading problem by simultaneously receiving the same program with several antennas, the proposed solution is advantageous, since it requires only a single antenna.     

软件无线电调制解调通用平台的设计与实现

软件无线电被认为是继模拟通信到数字通信、固定通信到移动通信之后无线通信领域的第三次突破。文章在研究软件无线电的基本结构的基础上从信号空间映射的角度对通信信号的调制解调进行了深入的研究，将已调信号表示为N维正交基函数的展开式，根据调制方式确定调制信号到N维信号空间的映射从而完成调制过程；同时引入空间距离的概念，根据调制映射关系，建立起多对一的最优信号检测理论。并且使用MATLAB编制了基于软件无线电结构的通信信号调制解调通用平台软件，实现了对各种调制解调模式的兼容。     

软件无线电实现方案研究

本文提出了一种基于交换网络的软件无线电的硬件平台 ,同时完成了一个实验平台 ,证明了上述思路是可行的。还介绍了在实验平台中所采用的一种高效率的内插算法     

Jitter requirements of the sampling clock in software radio receivers

The effective number of bits of an analog-to-digital converter (ADC) is not only limited by the quantization step inaccuracy but also by sampling time uncertainty. According to a commonly used model, the error caused by timing jitter, integrated over the whole bandwidth, should not be bigger than the quantization noise, for a full swing input signals at the maximum input frequency. This results in unfeasible phase noise requirements for the sampling clock in software radio receivers with direct RF sampling. However, for a radio receiver not the total integrated error is relevant, but only the error signal in the channel bandwidth. This paper explores the clock jitter requirements for a software radio application, using a more realistic model and taking into account the power spectrum of both the input signal and the spectrum of the sampling clock jitter. Using this model, we show that the clock jitter requirements are very similar to reciprocal mixing requirements of superheterodyne receivers.     

基于带通采样软件无线电接收子系统的实现

软件无线电在通信中有着重要的作用,采用中频带通采样数字化结构,通过实例给出了软件无线电接收系统的具体软、硬件设计和实现方式。     

Low power and high-speed implementation of fir filters for software defined radio receivers

The most computationally intensive part of the wideband receiver of a software defined radio (SDR) is the intermediate frequency (IF) processing block. Digital filtering is the main task in IF processing. The computational complexity of finite impulse response (FIR) filters used in the IF processing block is dominated by the number of adders (subtracters) employed in the multipliers. This paper presents a method to implement FIR filters for SDR receivers using minimum number of adders. We use an arithmetic scheme, known as pseudo floating-point (PFP) representation to encode the filter coefficients. By employing a span reduction technique, we show that the filter coefficients can be coded using considerably fewer bits than conventional 24-bit and 16-bit fixed-point filters. Simulation results show that the magnitude responses of the filters coded in PFP meet the attenuation requirements of wireless communication standard specifications. The proposed method offers average reductions of 40% in the number of adders and 80% in the number of full adders needed for the coefficient multipliers over conventional FIR filter implementation methods     

Design and multiplier-less implementation of a class of two-channel PR FIR filterbanks and wavelets with low system delay

A new method for designing two-channel PR FIR filterbanks with low system delay is proposed. It is based on the generalization of the structure previously proposed by Phoong et al. (1995) Such structurally PR filterbanks are parameterized by two functions (/spl beta/(z) and /spl alpha/(z)) that can be chosen as linear-phase FIR or allpass functions to construct FIR/IIR filterbanks with good frequency characteristics. The case of using identical /spl beta/(z) and /spl alpha/(z) was considered by Phoong et al. with the delay parameter M chosen as 2N-1. In this paper, the more general ease of using different nonlinear-phase FIR functions for /spl beta/(z) and /spl alpha/(z) is studied. As the linear-phase constraint is relaxed, the lengths of /spl beta/(z) and /spl alpha/(z) are no longer restricted by the delay parameters of the filterbanks. Hence, higher stopband attenuation can still be achieved at low system delay. The design of the proposed low-delay filterbanks is formulated as a complex polynomial approximation problem, which can be solved by the Remez exchange algorithm or analytic formula with very low complexity. In addition, the orders and delay parameters can be estimated from the given filter specifications using a simple empirical formula. Therefore, low-delay two-channel PR filterbanks with flexible stopband attenuation and cutoff frequencies can be designed using existing filter design algorithms. The generalization of the present approach to the design of a class of wavelet bases associated with these low-delay filterbanks and its multiplier-less implementation using the sum of powers-of-two coefficients are also studied.     

软件无线电的扩频通信接收系统的研究与实现

将扩频技术和软件无线电技术相结合在未来扩频通信的发展中占有重要的地位 ,基于软件无线电的思想 ,给出扩频通信接收系统的硬件平台的具体实现方案 ,并对伪码和载波同步提出具体的软件实现方法。     

Adaptive prediction and cancellation digitization method for wideband multistandard software radio base-station receivers

In this study, a new method for digitizing a combination of different analog signals occupying significantly different bandwidths and having a very high dynamic range is proposed and analyzed. Since it is based upon signal-prediction/cancellation principles, it is referred to as adaptive prediction and cancellation digitization (APCD) method and is applied to various families of signals simultaneously received by a multistandard software radio (SWR) base-station receiver. It is shown theoretically and by means of computer simulations that the APCD method can effectively reduce the high dynamic range of the signals before digitization takes place. Hence, the stringent analog-to-digital-converter (ADC) resolution requirements imposed by the operation of such SWR base-station receivers can be significant relaxed. The signal dynamic-range reduction is achieved by applying appropriate signal processing techniques, e.g., autoregressive (AR) and periodic autoregressive (PAR) prediction. Such techniques allow accurate prediction and subsequent cancellation of high-power narrowband signals present among the composite received analog signal. As these signals usually have cyclostationary statistical characteristics, analysis and performance evaluation of AR and PAR predictors, when used to predict cyclostationary signals, were presented. A new adaptive algorithm for implementing the PAR predictor is also proposed, and its validity is justified by theoretical analysis as well as by various performance evaluation results obtained by means of computer simulations.     

基于软件无线电的OFDM解调模块的设计与实现

针对IEEE802.11a标准中OFDM调制解调原理,结合软件无线电的思想,采用高效率的System Generator软件,对OFDM部分的解调模块进行设计与实现。设计中采用16QAM对数据符号进行调制,可以有效地降低系统误码率。仿真结果表明,所设计的OFDM解调模块具有较高的可靠性。     

一种多功能红外图像播放软件的设计实现

文中针对红外装置采集的信息图形化处理的需求,借鉴视频播放器的设计思路,采用动态链接库、ActiveX技术等模块化设计方法开发了红外图像播放软件。实践表明,该软件在用户界面上通过鼠标控制,可实现连续显示图像、显示单点或范围内像素信息的功能。基于红外信息的特点,该软件还可以通过辅助信息标识出目标位置,并旋转图像以符合惯性坐标系下视角。该软件的开始、暂停、停止和改变播放速度等播放控制功能,以及自动灰度调节、转换位图、转换视频等功能使红外信息处理更加方便,为类似图像处理需求提供了一种功能全面、运行稳定、适应性强的方法。     

The software radio concept

Since early 1980 an exponential blowup of cellular mobile systems has been observed, which has produced, all over the world, the definition of a plethora of analog and digital standards. In 2000 the industrial competition between Asia, Europe, and America promises a very difficult path toward the definition of a unique standard for future mobile systems, although market analyses underline the trading benefits of a common worldwide standard. It is therefore in this field that the software radio concept is emerging as a potential pragmatic solution: a software implementation of the user terminal able to dynamically adapt to the radio environment in which it is, time by time, located. In fact, the term software radio stands for radio functionalities defined by software, meaning the possibility to define by software the typical functionality of a radio interface, usually implemented in TX and RX equipment by dedicated hardware. The presence of the software defining the radio interface necessarily implies the use of DSPs to replace dedicated hardware, to execute, in real time, the necessary software. In this article objectives, advantages, problem areas, and technological challenges of software radio are addressed. In particular, SW radio transceiver architecture, possible SW implementation, and its download are analyzed     

The software radio architecture

As communications technology continues its rapid transition from analog to digital, more functions of contemporary radio systems are implemented in software, leading toward the software radio. This article provides a tutorial review of software radio architectures and technology, highlighting benefits, pitfalls, and lessons learned. This includes a closer look at the canonical functional partitioning of channel coding into antenna, RF, IF, baseband, and bitstream segments. A more detailed look at the estimation of demand for critical resources is key. This leads to a discussion of affordable hardware configurations, the mapping of functions to component hardware, and related software tools. This article then concludes with a brief treatment of the economics and likely future directions of software radio technology     

IP可视会议系统的设计与实现

介绍了一种基于Windows操作系统的桌面IP可视会议系统的设计与实现,并主要描述了IP可视会议系统的组成、工作流程、音频／视频压缩算法以及主要软件模块的实现方法。     

高交互型蜜罐的设计与实现

网络陷阱系统是一项新兴的信息安全技术,在网络信息安全界俗称为蜜罐。它采用的是主动防护的安全策略,目的是在网络上设置一个诱骗环境,吸引黑客的入侵,从而监测黑客的行为,了解他们使用的工具,分析他们的动机。本文研究了蜜罐系统的分类和体系结构,提出了一个高交互型蜜罐系统,并论述该系统采用的关键技术。     

一个VPN应用系统的设计与实现

介绍了一个利用VPN技术实现的网络系统应用实例，充分体现VPN应用系统低成本和安全的特点。简要介绍和比较了当前较为成熟的VPN技术方案的特点，为政府部门和机关团体单位利用公共网络建立自己专用的应用系统起到了抛砖引玉的作用。     

高校学术成果管理系统的设计和实现

针对科研管理信息系统的子系统一学术成果管理系统进行了设计和实现。讨论了C／S模式和B／S模式混合模式使用的优越性，实现了学术成果管理信息系统的输入、修改、查询、统计分析和打印等多项功能，并利用OLE技术调用Excel实现了复杂表格的打印。     

嵌入式组态软件系统的设计

针对后PC时代的到来,个人计算机随之向着掌上嵌入式计算机方向发展,为了适应组态软件在嵌入式环境下运行的问题,提出了采用嵌入式技术开发嵌入式组态软件的方案。本设计首先论述了嵌入式组态软件系统在当今自动化领域的发展及现状,给出了嵌入式组态软件的概念,然后分模块对嵌入式组态软件系统进行了阐述。在本设计中,主要把嵌入式组态软件系统分为以下4个模块：嵌入式接口模块、嵌入式实时数据库模块、嵌入式历史数据库模块、嵌入式图形模块。     

试卷评价软件系统的设计

试卷评价软件系统根据教育测量学原理,以考试数据为样本,采用相应的计算公式对试卷的信度、效度、难度、区分度进行评价,生成试卷质量的评价报告,为教育教学工作者提供有效的评价工具,对于提高教育教学质量,改进教学过程,提高人才培养的质量有很大的益处。     

基于多相滤波器的信道化接收机及其应用研究

本文主要研究了应用多相滤波技术的信道化接收机建模问题。在给定信道频谱划分方案下,推导了基于多相 滤波器的信道化接收机数学模型。并由此模型设计了一个四信道模拟系统。最后用仿真实验结果验证了模型的正确性。