扩频技术:历史、现状及发展

从军事抗干扰通信和个人通信业务对频谱分配的要求回顾了扩频技术的历史,并着重从直接序列扩频系统的码捕获和多用户检测两方面讨论扩频技术的研究现状。在第四代移动通信系统的发展背景下,结合超宽带、多载波调制以及软件无线电等新技术讨论扩频技术的发展趋势。最后,给出研究过程中得出的结论。     

一种低功耗软件无线电信号处理平台

介绍一种应用于软件无线电的数字信号处理平台,通过对平台设计架构、硬件实现方案及软件可配置功能的阐述,提出了GMSK和CPM两种无线通信波形软件实现方案。该平台采用OMAP+FPGA的架构,具有通用性好、扩展性强等特点,适合于高性能、低功耗的应用场合,可广泛应用于在无线通信、导航定位、图像处理等数字信号处理领域。     

An Approach to T&E of Military SDR Platforms and Waveforms: the LANCERS Lab

Software Defined Radio (SDR) is currently one of the main topics of interest in military communications, as well as in civil ones. Since 2002, the Italian Ministry of Defense (MoD) has identified the SDR technology as a strategic capability. In this respect, Italy has become part of the major multinational programs related to military SDR and waveforms, such as ESSOR (European Secure Software Radio) and COALWNW (COALition Wideband Networking Waveform). In addition, the Italian national SDR program (SDR-N) aims at developing a complete family of SDR products, part of which are already available for fielding. In order to develop a governmental capability of Test and Evaluation (T&E) for future SDR, minimizing the risks related to the fielding of this new technology, a dedicated laboratory, called LANCERS lab, has been established in the premises of CSSN ITE (Centro Supporto e Sperimentazione Navale Istituto per le Telecomunicazioni e lElettronica), a research center of the Italian Navy. LANCERS lab gathers the expertise of military technical personnel and University researchers, to provide a twofold capability: developing T&E strategies and procedures for the new tactical communications based on SDR and maintaining knowledge about the state of the art of SDR, fostering new research and development. In this paper we describe the LANCERS lab in all the following aspects: plan of development, organization, current activities, and future perspectives.     

未来移动通信系统及其关键技术

文中介绍了未来移动通信系统的特点和网络架构。讨论了未来移动通信物理层的正交频分复用技术（OFDM）、多入多出系统（MIMO）、认知无线电技术、软件无线电技术以及自适应调制与编码技术等传输的关键技术以及相应的网络结构和协议。最后对未来移动通信系统的发展进行了一定的展望,即未来移动通信系统应该具有高教据率、高频谱利用率、低发射功率、灵活业务支撑能力等特点。     

Implementation of Reconfigurable Transceiver using GNU Radio and HackRF One

Relying on the past technology radio reception through hardware needs front end tuning which in turn internally changes the frequency of the capacitor. Thus the conventional radio can capture the required frequency by tuning manually. As the technology advances the wireless technology shown the light of cognition through which real time data transmission and reception are implemented using reconfigurable radio i.e., Software Defined Radio (SDR) whose physical layer functions are mainly or fully defined by software. In this paper, HackRFOne (Software defined Radio SDR) is tuned to the required radio frequency by employing GNU Radio Companion and Gqrx (spectrum viewer), where both GNU Radio and Gqrx are an open ended software. Cognitive Radio have revealed that by varying the software, the hardware adjustment is possible only within a fraction of the time. However, this requires more knowledge on signal processing blocks so that adjusting certain parameters like gain and frequency of filter can be made in the receiver side. The goal of this paper is to focus on the signal processing blocks which plays vital role in implementing the transmitter / receiver for reconfigurable wireless communication system.

     

超高速跳频通信系统的实现及抗干扰性能

跳频通信是军事通信领域中的一种重要的抗干扰手段,该文对超高速跳频通信系统实验平台的实现及其抗干扰性能作了介绍。该实验平台工作在VHF/UHF频段,跳频带宽51.2MHz,跳频速率为每秒十万跳,数据传输速率最高可达96kbps,在工作频点被干扰60％情况下,系统仍然可以保持通信,具有极强的抗截获能力和抗干扰能力。实验台的构成遵循了软件定义无线电思想,采用了数字直接频率合成器来实现跳频信号的调制和解调。利用超外差原理以及高精度模数转换,各种信号处理算法及工作参数均可在软件中调整。最后,文章分析了超高速跳频通信体制带来的抗干扰性能,并给出实验结果。     

基于软件无线电的FM正交调制器的实现

基于软件无线电(SDR)的思想,介绍了一种新型FM调制方法———正交调制,并利用Xilinx的高级系统级FPGA仿真工具System Generator for DSP对这种正交调制方法进行建模、仿真。实验结果表明,用正交调制的方法可以方便地实现FM调制。用数字方法为实现FM调频广播或超短波FM电台提供新的解决方案。     

OFDM系统中ICI自消除算法研究

OFDM系统对频率偏移极为敏感,频率偏移将导致子载波之间失去正交性,于是产生子载波干扰（ICI）,从而降低系统性能。通过对有效抑制ICI的方法—ICI自消除算法进行研究,分析了ICI自消除算法对OFDM系统的影响。在软件无线电（GNU Radio）平台上搭建该系统,并在实际环境中运行。研究结果表明：与传统OFDM系统相比,ICI自消除算法使OFDM系统的误码率得到改善。     

数据驱动的开放动态频谱接入系统构建方法

在认知无线电(CR)背景下,动态频谱接入已成为提高无线网络频谱利用率的重要途径。基于全球移动通信系统-铁路(GSM-R)系统中采集的细粒度频谱监测数据,提出一种数据驱动的深度学习方法,建模频谱模式,并建立一套动态频谱接入访问框架。采用一种深度频谱生成模型指导频谱分配;设计一种综合递归序列表征与场景特征嵌入的深度网络,建模和预测短时频谱占用情况,并由此提出一种动态信道接入策略。进一步,利用软件无线电(SDR)平台实现一套跳频系统,并将其与动态频谱接入策略进行集成。使用真实的历史频谱数据评估该系统的数据吞吐能力,测试结果表明,所提方法及构建的跳频系统能有效提高机会通信能力,高效利用频谱资源。该频谱接入框架及SDR系统实现具有较强的通用性,易于集成到不同场景和频段的系统中。     

基于软件通信体系结构的OFDM波形实现

探讨了软件定义无线电开放的软件通信体系结构(SCA),实现了其核心框架,在此基础上给出了OFDM波形应用的开发过程,这些都为以后其他波形应用的开发提供了基础。     

手持短波软件电台系统与结构解决方案

针对用户对背负式短波数字化抗干扰电台的体积缩小要求,提出了一种采用软件无线电(SDR,Software Defined Radio)技术,通过对中射频全数字化最终形式,设计了一款手持短波软件电台。主要研究了短波数字化抗干扰电台到手持短波软件电台的体系与结构解决方案,解决了手持短波软件电台体系框架建设与结构体积压缩及电磁兼容等问题。实现了手持短波软件电台系统与结构小型化方案,并对系统和结构进行了研究、分析、试制、总结,最终达到了实际使用和开发产品应用目的。     

Implementation of an SDR system using an MPI-based GPU cluster for WiMAX and LTE

This paper presents an implementation of a 2?×?2 Multi-Input Multi-Output Software Defined Radio (SDR) Base Station system using a Message Passing Interface (MPI)-based Graphic Processing Unit (GPU) cluster as its modem processor for a high-speed data processing. Recently, GPUs have been widely researched especially for SDR systems because of their capability for exploiting parallel processing using a large number of Arithmetic Logic Units. MPI-based GPU clusters have been adopted in order to further increase performance capability. From our experimental results, it has been found that the implemented system consisting of three GPU nodes can enhance the modem speed by more than 2.5 times compared to a single GPU system. A dual-mode Mobile Device (MD) prototype supporting Worldwide Interoperability for Microwave Access and Long Term Evolution communications systems is implemented. In our design, one of the two waveforms can automatically be selected by the MD itself using a dual-mode controller that determines the reconfiguration of the MD modem depending on the received signal quality.     

软件无线电体系结构研究

软件无线电设备是未来十年电信产业朝着基于IP的网络、在一个混合层次结构的自组网络环境下提供全球无缝无线接入的关键。主要介绍了软件无线电的体系结构、微处理器的选择和软件结构。     

软件无线电信道处理的DSP实现

本文重点研究了软件无线电(Software Defined Radio,SDR)中不同信道的处理技术,其技术关键在于构建不同频段的数字滤波器进行不同信道信息的接收处理.在建立软件无线电信道模型的基础上,利用MATLAB实现了多阶FIR滤波器的设计,并将算法移植到DSP软件设计当中,在DSP的集成开发环境CCS下对FIR滤波进行了仿真,仿真结果达到了SDR的信道处理要求.     

基于软件无线电的数字调制信号自识别的研究

软件无线电的基本思想是构造一个具有开放性、标准化、模块化的通用硬件平台,通过软件编程来实现无线电台的各种功能。调制方式的多样化必然导致无线电台的多模式化。调制方式多样化的存在,就必须要具备自动识别各种调制方式的方法,所以,信号调制方式的自动识别是软件无线电中必须具备的功能之一。决策理论具有结构简单,识别种类多的优点,这也是本文采用决策理论的主要原因。最后仿真验证了决策理论是非常有效的。     

软件无线电：总体设计思路和数字硬件选择探讨

This paper reviews the requirements for Software Defined Radio (SDR) systems for high-speed wireless applications and compares how well the different technology choices available- from ASICs, FPGAs to digital signal processors (DSPs) and general purpose processors (GPPs) - meet them.     

SDR——未来无线通信设备的基本概念

根据国际上的最新进展,本文对软件定义无线电（SDR）进行讨论和介绍。SDR是一个新的概念和体系,它是一个可重编程的可重构的,能支持多种无线通信体制和标准的无线通信设备。本文介绍了美国对SDR设备的要求,此技术为产品开发、制造商、运营商及最终用户带来了好处,以及SDR所面临的挑战。显然,在几年内,SDR技术将广泛使用于新一代通信产品的设计中,基于SDR的无线通信设备将成为市场中的主要部分。     

Design and rapid prototyping of SCA-compliant public safety P25 waveform and P25?CFM3TR?CVoIP bridge

Establishing radio communication between military commanders, soldiers and law enforcement officers is an important enabling capability to facilitate interoperability. The Joint Tactical Radio System (JTRS) program is enabling communications within the military by implementing different military radio waveforms on software defined radio (SDR) platforms. It is logical to include a Project 25 (P25) public safety waveform in the JTRS waveform portfolio. This paper describes the rapid development of a P25 waveform on a surrogate JTRS SDR platform. The development process and methodology, which starts from a platform agnostic executable waveform model in Matlab, through an intermediate implementation using open tools on generic platforms, to the final platform-specific implementation, is introduced and discussed. This paper shows that adopting this methodology can speed up waveform development and porting. Furthermore, this paper presents the design and implementation of a three way voice bridge among P25, the future multiband multiwaveform modular tactical radio (FM3TR), and voice over Internet Protocol (VoIP), with software communication architecture (SCA) compliant implementation for both the P25 and FM3TR waveforms. This paper shows that critical issues such as interoperability can be tackled efficiently by leveraging SDR and SCA.     

Denial of Service Prevention for 5G

5G wireless mobile communication is expected to include a large number of advanced technologies in order to further increase bandwidth, Quality of Service (QoS), improve usability and security, decrease delays and cost of service. Software Defined Radio (SDR) will be the platform for advanced terminals. Our focus is security and especially prevention of Denial of Service (DoS) attacks which we believe will become more common in commercial networks through increasing availability of easy programmable SDRs. We propose a secret version of Adaptive Frequency Hopping, as a possible 5G technology in combination with others, with QoS estimation by means of physical layer parameters. The QoS parameter chosen is Bit Error Rate (BER) and this we use for blacklisting frequencies that we assume are under DoS attack. Our experimental results on BER estimation show this to be a promising approach.