一种基于星座图恢复的多进制相位调制信号识别算法

在实际调制过程中,无线电波传输多径及衰落引起的符号间干扰和信号接收端的载波频偏会造成星座图难以识别。针对这一问题,提出了一种基于星座图恢复和卷积神经网络的多进制相位调制信号识别算法。首先,设定相邻采样点距离和相位角的阈值以筛除发生符号间干扰时的采样点,保留剩余的有效采样点并形成聚类组;然后,通过旋转相邻聚类组抵消载波频偏带来的影响,实现星座图的恢复;最后,利用卷积神经网络对星座图进行特征自动提取和调制识别。实验结果表明,对于实测信号,所提算法能够较好地恢复星座图并实现BPSK、QPSK和8PSK的准确识别。最终的识别准确率达到了99.9%,较星座图恢复前提高了24.2%。     

认知无线电中调制识别算法研究

通信信号的调制类型识别对于认知无线电这种智能通信系统具有重要研究意义。利用调制信号的循环谱相关特征,提取了5个特征参数,给出了各个参数随信噪比变化的曲线图。分类器基于RBF神经网络,采用"一类一个网络"结构,并从提高网络识别性能出发,构建了大容量和高质量的网络训练样本,能够扩大识别范围,提高识别精度。基于谱相关特征参数和神经网络分类器的算法能动态识别信号的调制方式,仿真结果验证了该算法在低信噪比下的有效性。     

基于支持向量机的C波段无线电异常信号识别

提出了一种基于支持向量机实现C波段无线电异常信号类型识别的方法.首先,通过对C波段实测异常信号进行统计分析,提取被识别信号的有效频域特征.其次,基于支持向量机分类器结构简单、泛化能力强、可获得全局最优等特点,构建了基于径向基核函数的支持向量机信号识别系统,取得了较高的识别率.最后,Matlab实验结果表明该方法信号识别效率高,在同等条件下优于神经网络.     

基于BP神经网络的通信信号调制体制识别技术

本文研究了基于BP神经网络的通信信号调制体制识别技术。提取了反映信号调制体制差异的特征参数,并从提高收敛速度和正确识别概率出发,构建了最佳的神经网络分类器。实验结果表明,该技术拥有较好的通信信号调制体制识别性能。     

浅析无线电信号识别方法的研究

分类器的选择和特征参数提取两部分是无线电的信号识别的通用方法,本文主要以小波变换为例,对无线电信号的识别方法进行研究,在小波变换中主要通过ASK、FSK和PSK三种信号的变换,提出对以上三种信号识别的方法---小波脊线特征提取,并仿真实验进行证明,最后推出结论：在信噪比较好的条件下采用小波变换识别的方式能够很好的进行信号识别,但是对PSK信号在信噪比不好的情况下很难识别。     

模拟调频系统的单载波干扰压制理论分析

本文针对现阶段利用模拟制式无线电设备进行考试作弊的行为，分析利用单载波信号作为干扰信号在不同信干比和频偏情况下利用锁相环解调的效果，并提出单载波压制的结论。     

基于分段FFT的抑制载波调相信号载波捕获方法研究

针对在低码速率大频偏范围条件下抑制载波调相信号载波捕获困难的问题,提出了一种改进的基于分段FFT载波捕获方法.该方法根据抑制载波调相信号的载波提取特点,采取了分段并行FFT分析、 两级滤波、 相干累积和非相干累积的改进措施,以适应低码速率大频偏范围的载波捕获.对改进的基于分段FFT的抑制载波调相信号载波捕获方法进行了仿...     

基于软件无线电的扩频通信系统同步性的研究

采用现场可编程门阵列FPGA实现软件无线电技术,控制和调整扩频通信系统的同步性能。该系统介绍了用FPGA实现对采样信号正交数字下变频,完成同步搜索和频偏估计,以及纠正载波频偏和调整码元速率,同步跟踪。系统锁定同步信息并跟踪载波频偏变化,进行扩频码的非相干解调和解扩,最后还原出基带信息,实现同步性。     

基于循环自相关的OFDM调制识别方法

针对通信信号的调制识别问题,首先根据通信信号的循环平稳性,提出一种基于循环自相关的OFDM信号和单载波信号的调制识别算法,然后将小波多分辨分析理论与调制信号的瞬时特征以及高阶累积量相结合,提出一种基于小波分解的单载波信号识别方法,在此基础上采用分层结构的神经网络分类器对OFDM,2ASK,4ASK,2PSK,4PSK,8PSK,16QAM这7种调制信号进行识别。仿真结果表明该方法具有良好的分类性能,且对噪声不敏感。     

OFDM-IDMA系统的迭代频偏估计及补偿

针对OFDM IDMA系统中载波频偏(CFO)带来的子载波之间的干扰问题,提出了在各用户具有相同频偏下的联合逐码片(构的信号作为虚拟的训练序列进行频域频偏估计,同时进行相应的时域频偏补偿.理论分析及实验仿真结果表明:基于逐码片迭代检测的近无频偏时的性能CBC)迭代检测的载波同步方法.该方法利用迭代检测中的外信息重OFDM IDMA系统的频偏估计和补偿方法能够使系统性能接     

Effects of Power Amplifier Distortion and Carrier Frequency Offset on the Performance of WLAN System

Due to the efficiency of mitigation multipath delay spread, orthogonal frequency division multiplexing (OFDM) is extensively used in the wireless local area network (WLAN) domain, such as the IEEE 802.11a standard defined by the IEEE 802.11 standardization group and the HIPERLAN/2 defined by the European Telecommunication Standards Institute Project on Broadband Radio Access Networks. OFDM based WLAN system is very sensitive to the power amplifier distortion and the carrier frequency offset. The performance of the OFDM based WLAN system in the presence of the power amplifier distortion and the carrier frequency offset under practical fading channel is researched and analyzed in this paper. A closed form of bit error rate (BER) is derived for the OFDM based WLAN system in the presence of the power amplifier distortion and the carrier frequency offset under practical fading channel. The effects of the power amplifier distortion and the carrier frequency offset on the OFDM based WLAN system performance are comparatively studied by the theoretical method and by the simulation method under practical multipath fading channels. Studies show that the theoretical and simulated results match well.     

基于混沌算法的无线安全认证技术研究

针对无线网络安全威胁。提出了一种基于混沌算法的无线安全认证方案，利用混沌对初始条件的依赖性可以生成混沌序列，以此作为无线用户的身份，这种身份具有惟一性和不可伪造性，并且是可以动态变化的。同时还给出了IEEE802．11无线局域网环境中基于混沌理论的动态认证方案和过程。研究结果表明．该方案具有良好的加密效果，运算量小，抗攻击强，有较高的安全性。     

Secure and efficient scheme for fast initial link setup against key reinstallation attacks in IEEE 802.11ah networks

IEEE 802.11ah is a recently released IEEE standard to specify a wireless communication system with a long‐range, low‐power, and low data transmission rate over smart devices used in Internet of Things (IoT) systems. This new standard belongs to IEEE 802.11 wireless local area networks (WLANs) protocol family. It requires lightweight protocols to support the low‐power and low‐latency features of the IoT devices. On the other hand, an upcoming solution of fast initial link setup (FILS) specified by IEEE 802.11ai standard is a brand‐new approach aiming to establish fast and secure links among devices in WLANs to meet this new demand. It is natural and feasible to apply it to the 802.11ah networks to support massively deployed wireless nodes. However, security concerns on the link connection by the FILS scheme have not been fully eliminated, especially in the authentication process. It has been explored that a type of recently revealed malicious attack, key reinstallation attack (KRA) might be a threat to the FILS authentication. To prevent the success of the KRAs, in this paper, we proposed a secure and efficient FILS (SEF) protocol as the optional substitute of the FILS scheme. The SEF scheme is designed to eradicate potential threats from the KRAs without degrading the network performance.     

AAA architecture for mobile IPv6 based on WLAN

Mobility support for Internet devices is quite important for consumer electronics. The number of the hand‐held devices is growing quickly. However, there are not enough IP addresses for the number of the rapidly growing devices in the All‐IP generation. Internet Protocol version 6 (IPv6) was therefore adopted to solve these problems. Our purposed structure is based on IEEE 802.11. However, IEEE 802.11 has a serious security drawback. Further, from the Internet Service Providers' point of view, accounting is a potential problem. A mechanism combining Mobile IPv6 and AAA based on IEEE 802.11 to overcome these problems is essential. Both Internet Protocol version 4 (IPv4) and IPv6 support IP security (IPsec) when data packets are exchanged across the IP network. IPsec operates at the IP layer. It can support system authentication and authorization, However, it lacks a system accounting function. Therefore ISPs cannot establish correct billing for their services. This is the reason why we chose to combine the wireless network and AAA functions. In this paper, the AAA mechanism is used to protect security, with the architecture having authentication, authorization, and accounting functions. We will discuss the benefits of AAA and state the reason why we choose to combine AAA with the mobility architecture. Copyright © 2004 John Wiley & Sons, Ltd.     

IEEE 802.11i标准与WLAN安全性分析

详细分析了WLAN(无线局域网)的最新安全标准IEEE 802.11i,包括标准体系结构、接入认证和访问控制以及加密机制;同时,分析了该标准的网络认证与授权、密钥生成与管理和数据加密机制;最后指出了WLAN安全领域需要进一步研究的课题及802.11i目前仍存在的问题.     

Wireless LAN security and IEEE 802.11i

This article reviews wireless LAN security with a focus on the evolving new IEEE 802.11i standard. The major security enhancements in encryption and authentication defined by 802.11i are illustrated. In addition, the newly introduced key management in 802.11i is discussed. Because 802.11i incorporates IEEE 802.1X as its authentication enhancement, 802.1X with consideration of roaming users is depicted. Both intrasubnet and intersubnet roaming are illustrated.     

IEEE 802.11 goodput analysis for mixed real-time and data traffic for home networks

Increasingly, wireless networks are being used to provide connection services for devices running applications with very different quality of service requirements. Although this issue has been addressed by the IEEE 802.11e standard, the fact is that most networks deployed in home/office environments nowadays use IEEE 802.11a/b/g standard devices. Unfortunately, administrators often do not set configuration parameters of network devices to maximize resources performance, thus providing poor quality of service. In this paper, two IEEE 802.11a/b/g analytical performance evaluation models for mixed traffic Ad Hoc and infrastructure WLANs are presented, assuming that some network devices are executing single applications, like VoIP, videoIP or network browsing. In our analysis, network devices are grouped according to the expected traffic pattern of the applications they are running. Then, global and individual group goodput are calculated assuming a congested network. Based upon the outcome of this analysis for different settings of the device configuration parameters, it is shown that the performance of a standard home/office IEEE 802.11 wireless network can be significantly improved by choosing appropriate values of these parameters.     

无线局域网安全机制

为了达到与有线网络相同的安全性，IEEE802．11协议在MAC层引入安全机制，提供鉴别和保密服务。其核心是协议定义的WEP（wired equivalent privacy）算法。本文系统地介绍IEEE802．11的安全机制的构成以及认证、加密、和WEP算法，对其安全性能进行分析，指出存在的安全隐患。并对当前关于增强无线局城网安全性的有关方案进行探讨。     

A mutual authentication and privacy mechanism for WLAN security

IEEE 802.11 wireless local area networks (WLAN) has been increasingly deployed in various locations because of the convenience of wireless communication and decreasing costs of the underlying technology. However, the existing security mechanisms in wireless communication are vulnerable to be attacked and seriously threat the data authentication and confidentiality. In this paper, we mainly focus on two issues. First, the vulnerabilities of security protocols specified in IEEE 802.11 and 802.1X standards are analyzed in detail. Second, a new mutual authentication and privacy scheme for WLAN is proposed to address these security issues. The proposed scheme improves the security mechanisms of IEEE 802.11 and 802.1X by providing a mandatory mutual authentication mechanism between mobile station and access point (AP) based on public key infrastructure (PKI), offering data integrity check and improving data confidentiality with symmetric cipher block chain (CBC) encryption. In addition, this scheme also provides some other new security mechanisms, such as dynamic session key negotiation and multicast key notification. Hence, with these new security mechanisms, it should be much more secure than the original security scheme. Copyright © 2006 John Wiley & Sons, Ltd.     

WLAN security processor

A novel wireless local area network (WLAN) security processor is described in this paper. It is designed to offload security encapsulation processing from the host microprocessor in an IEEE 802.11i compliant medium access control layer to a programmable hardware accelerator. The unique design, which comprises dedicated cryptographic instructions and hardware coprocessors, is capable of performing wired equivalent privacy, temporal key integrity protocol, counter mode with cipher block chaining message authentication code protocol, and wireless robust authentication protocol. Existing solutions to wireless security have been implemented on hardware devices and target specific WLAN protocols whereas the programmable security processor proposed in this paper provides support for all WLAN protocols and thus, can offer backwards compatibility as well as future upgrade ability as standards evolve. It provides this additional functionality while still achieving equivalent throughput rates to existing architectures.