一种改进的支持向量机分类器

提出了一种将支持向量机分类和最近邻分类相结合的方法,形成了一种新的分类器.实验结果表明使用支持向量机结合最近邻分类的分类器分类比单独使用支持向量机分类具有更高的分类准确率,同时可以较好地解决应用支持向量机分类时核函数参数的选择问题.     

部分频带干扰对跳频通信系统影响分析

部分频带压制干扰是现有的对跳频通信系统最有效的干扰方式之一。在分析了部分频带干扰对跳频同步和系统误码率影响的基础上,仿真了干扰条件下的同步捕获性能和系统误码率曲线。验证了部分频带压制干扰在覆盖同步频率时能有效降低同步捕获概率,当不覆盖同步频率时也能提高系统误码率,达到破坏敌方通信的目的。     

蓝牙跳频通信系统仿真设计

蓝牙通信技术因建立灵活、成本低、功耗低的特点而得到广泛应用。在介绍蓝牙跳频通信技术原理基础上,建立蓝牙跳频通信系统结构组成框图。应用Simulink对系统进行仿真,解释各模块的作用,列出具体的模块参数设置和参数设置的依据。仿真分析结果表明,蓝牙跳频通信系统的抗干扰性能受信道信噪比影响,因采用分组传输的方式,连续相位调制方式及跳频技术,蓝牙跳频系统具有较强的抗干扰能力。     

慢跳频的伪随机序列

本文基于ＧＦ（２）域上的增广质数序列,提出了一类ＧＦ（Ｐ＾Ｋ）域上的增广质数跳频序列,对其差的游程特性进行了改进,并根据慢跳频系统的要求进行了宽间隔处理。计算机模拟分析表明：宽间隔增广质数跳频序列具有良好的汉明相关特性,是一类优良的跳频序列,适合于慢跳频系统。     

基于差分空时调制的混沌慢跳频系统

提出一种慢跳频系统中基于差分空时调制的混沌保密通信方法。此方案集成了差分空时编码和混沌跳频扩频技术的优点。一方面,在跳频系统中,使用混沌序列代替伪随机(PN)码,增强了抗截获和抗预测的性能;另一方面,通过差分空时调制产生分集增益,降低了多径衰落效应的影响。仿真结果证实了此方案的有效性。     

超宽带高速步进频率信号源的设计

针对现有频率合成方法难以产生同时具备宽频带和高速频率跳变能力信号的问题,提出一种基于直接数字频率合成和直接频率合成技术的混合频率合成方案.介绍了其实现原理、设计方案以及测试结果,最终实现了带宽为1.5 GHz、跳频时间小于50 ns的高速步进频率信号源,该方案实现简单,性能优越.     

MIMO Frequency Hopping Spread Spectrum Multi-Carrier Multiple Access: A Novel Uplink System for B3G Cellular Networks

In this paper, we propose and give the performance of a novel uplink system based on the combination of multi-carrier (MC), code division multiple access (CDMA) and multiple input multiple output (MIMO) techniques. First, we describe the interests of spread-spectrum multi-carrier multiple access (SS-MC-MA) scheme for uplink, especially compared to MC-CDMA. Classically, with SS-MC-MA, each user spreads its data symbols on a specific subset of adjacent or multiplexed subcarriers, to facilitate the channel estimation and reduce complexity at the reception. In order to compensate for the lack of frequency diversity of SS-MC-MA with adjacent subcarriers, we first combine it with an orthogonal space-time block code (STBC) and demonstrate the resulting spatial diversity gain. Then, we propose to allocate the subsets to the different users by applying a frequency hopping pattern (FH). In that case, each user benefits from the frequency diversity linked to the total bandwidth as with the multiplexed subcarriers solution, while keeping the advantages of the adjacent subcarriers solution. The gain provided by the use of the frequency hopping is stressed on. Finally, the performance of this scheme is evaluated over realistic MIMO channel with channel turbo coding for systems offering asymptotic spectrum efficiency of 1, 2, 3 and 4.5 bit/s/Hz. Thus, the efficiency of the novel proposed STBC FH SS-MC-MA system as a very promising multiple access and modulation scheme for the uplink of the future wideband wireless networks is successfully demonstrated.     

A Robust Acquisition Scheme for FH Signal in Adverse Environments

Both partial-band jamming and multi- tone jamming have severe effect on the acquisition of frequency-hopping (FH) signal in adverse environments. In this paper, an anti-jamming FH signal acquisition scheme based on cognitive correlation process is proposed to boost the robustness of acquisition. The main idea of this scheme is to utilize a priori knowledge of FH speed and FH pattern to distinguish jamming signal from received signal. Furthermore, theoretic analysis on detection probability and false probability is given to demonstrate the robust performance of the FH signal acquisition method compared with conventional acquisition scheme without any prior information on FH speed and pattern in adverse environments.     

基于频道跳变的安全特定源组播通信

提出了一种基于组播频道跳变的安全特定源组播通信方案。通过以不定长周期改变特定源组播频道的组地址,解决了阻止恶意主机跟踪、加入特定源组播频道接收组播流量、对组播路由基础设施实施DoS攻击等问题。仿真数据表明,该方案具有较好的可扩展性和易实施性。     

蓝牙技术的快速连接转移模式

由于一个移动设备所属的微微网只有10 m距离,因此就有可能发生频繁的连接转移.连接转移需要移动设备与新的基站之间建立连接,这在频跳系统中是费时的过程,这种状态将引起许多连接的丢失从而影响网络性能.提出了一种新的模式用来改善连接转移的性能.模拟的结果显示,提出的模式显著的减少了连接转移的延时.