短波自适应跳频通信抗干扰技术研究

针对军事无线通信抗干扰和保密性需求，给出了自适应跳频通信系统模型。采用双态信道模型，深入分析了自适应跳频系统的抗干扰性能。分别在部分频带噪声干扰和多音干扰下，对常规跳频系统和自适应跳频系统性能进行了仿真，结果表明自适应跳频系统对上述两种干扰有较好的抗干扰性能。     

短波全数字自适应跳频通信

自适应跳频方式和短波通信的结合是现代短波通信系统的特点。由于采用了数字信号处理技术、自适应跳频技术和直接数字式频率合成技术,所以短波自适应跳频通信系统具有良好的抗干扰性能,被广泛应用于军事通信中。 一、短波全数字自适应跳频通信系统 在短波单边带通信系统数字化的基础上,增加自适应跳频控制器和跳频调制解调器的数字化电路部分,就形成了短波全数字自适应跳频通信系统。 短波全数字自适应跳频通信系统主要由声码器、编码／解码器、自适应跳频控制器、调制解调器和单边带收／发信机等组成。其中,自适应跳频控制器确定系统…     

SFH CDMA系统神经网络跳频方法

文章针对采用自适应跳频的DS／AFHCDMA系统的特点，在多目标优化的基础上采用神经网络方法实现自适应跳频地址编码，从而克服了系统在用户数量较大时跳频算法复杂性带来的实时性问题。结果表明，利用神经网络方式进行自适应跳频编码是有效、可行的方法。     

自适应跳频卫星通信系统的设计与实现

鉴于自适应跳频系统的良好抗干扰性能,提出了一种自适应跳频卫星通信系统的设计方案。在简要介绍自适应跳频技术基本原理的基础上,叙述了自适应跳频通信系统的结构和通信过程,重点讨论了自适应跳频卫星通信系统的设计模型、同步方式、频率集更新算法和抗干扰性能,最后,给出了自适应跳频卫星通信抗干扰终端设备的基本实现过程。     

基于自适应数字波束形成的跳频干扰抑制研究

本文主要研究了基于自适应数字波束形成（ＤＢＦ）的卫星通信地面跳频接收系统的抗博物邮采用将ＤＢＦ与跳频相结合的方式来抑制跳频快速跟踪干扰和宽带阻塞干扰,对干扰抑制性能进行了分析及仿真其仿真结果与分析是一致的。     

基于光纤光栅编解码和修正素数跳频码的一种光码分多址系统方案研究

在素数跳频码（PHCs）的基础上，研究了修正素数跳频码（MPHCs）的构造方法和性能，提出了基于光纤布拉格光栅（FBG）编解码实现修正素数跳频码这种二维地址码的光码分多址（OCDMA）系统方案。并通过对素数跳频码和修正素数跳频码这两种码字误码性能的分析，得到以下结论：对于相同的素数P，当系统误码率（BER）B≤10^-9，P≥37时，修正素数跳频码所容纳的最大用户数大于素数跳频码；在光纤布拉格光栅阵列上修正素数跳频码所需要的编码光栅数相对素数跳频码减少（P一1）／2个，从而降低了光纤布拉格光栅阵列的制作难度。     

基于跳频扩时光正交码的光码分多址系统性能分析

提出了一种基于光正交码（OOC）的跳频方案，与OOC系统相比，采用该跳频码字的光码分多址（OCDMA）系统的可容纳用户数目得到了极大提高，并且多用户干扰（MAI）大大降低，从而系统整体性能得到提高。同时提出了使用该跳频码的多比特传输光码分多址系统方案，该方案利用了跳频码字数目的充裕性，使得系统传输速率成倍提高。     

基于Matlab软件的蓝牙跳频改进算法

介绍了蓝牙跳频系统对跳频序列的要求,并且提出了一种改进的自适应跳频方案。基于C语言和MATLAB工具对原跳频系统和改进后系统分别进行了性能分析,仿真结果表明,本文提出的改进方案大大提高了系统的抗干扰能力。     

自适应跳频通信系统抗干扰性能分析

部分频带噪声干扰和多音干扰对常规跳频通信系统危害较大,自适应跳频系统能够改善跳频通信系统的抗干扰性能。基于自适应理论,对两个系统的抗干扰性能进行了仿真和比较,结果表明,自适应跳频通信系统对抗这两种干扰性能较强,适用于军事通信和其它易受人为干扰的通信领域。     

MFSK/FFH系统多用户能力分析与仿真

MFSK/FFH系统特指采用快速跳频（FFH）技术和多进制频移键控（MFSK）非相干解调技术的系统,主要研究MFSK/FFH通信系统的多用户能力,并把它与差分跳频技术DFH的组网能力进行对比分析。通过分析MFSK/FFH通信系统的性能,给出了MFSK/FFH通信系统和差分跳频系统的比特差错率公式,为了公平对比MFSK/FFH网络和差分跳频网的组网能力,采用多用户频带利用率这个参数,理论和仿真表明,采用特定的检测方法,MFSK/FFH系统的多用户能力比差分跳频系统的好。     

MC DS/SFH-CDMA systems for overlay systems

We introduce the slow frequency hopping (SFH) technique to the multicarrier (MC) code-division multiple-access (CDMA) systems for overlay situations. Using lower chip rate, which results in a narrower spectrum for each carrier and hopping the signal in frequency, the MC direct sequence (DS)/SFH system achieves better performance than the MC DS CDMA system in most cases, especially when the bandwidth of the narrowband interference (NBI) is narrower than one subchannel. It also exhibits a stable performance against the variations of the NBI location and bandwidth. When there is no NBI, the two systems perform approximately the same. The evaluation is performed over a frequency selective Rayleigh fading channel, with both Gaussian approximation and Monte Carlo simulation     

Performance analysis of a hybrid DS/SFH CDMA system usinganalytical and measured pico cellular channels

This paper presents the throughput and delay analysis of a packet-switched code division multiple access (CDMA) network based on the hybrid direct sequence (DS)/slow frequency hopping (SFH) spread-spectrum multiple access (SS MA) technique with Q-, B-, and D-PSK modulation using analytical and measured pico cellular channels. The performance of the hybrid DS/SFH, DS, and SFH multiple access techniques have been compared in a pico cellular personal communications network (PCN) environment. Multipath and multiple access interference are considered. The performance is evaluated for a given delay spread and a fixed bandwidth. The effects of forward error correction (FEC) coding and diversity techniques, such as selection diversity and maximal ratio combining on the performance, are also investigated     

随机M进制正交码混合DS—SFH CDMA扩频通信系统性能分析

本文研究了随机ＭＦ是制正交码混合ＤＳ－ＳＦＨ扩频码分多址信号经过多径瑞利频率非选择性衰落信道，在非相干ＲＡＫＥ接收机中采用最大输出信噪比选择或最大输出选择接收时系统的性能；给出了两种分集接收情况下差错概率表示式。数值计算研究了分集数，Ｍ值，多用户干扰对系统性能的影响，并且对这两种分集接收情况下系统性能进行了比较。     

Multicarrier DS/SFH-CDMA systems

Multicarrier direct-sequence/slow-frequency-hopping (MC DS/SFH) code-division multiple-access (CDMA) systems are proposed, in which multiple carriers are modulated by the same DS waveform and hopped in frequency according to a random hopping pattern. The receiver dehops the received signal with the same pattern, provides RAKE receivers for each carrier, and combines the outputs with a maximal ratio combiner (MRC). The performance of the proposed system is investigated over a frequency-selective Rayleigh-fading channel and compared to that of the MC DS-CDMA systems. It is shown that for the same diversity order, the MC DS/SFH-CDMA systems are superior in reducing multiple-access interference (MAI) while preserving the good capability of narrowband interference suppression, when the system parameters are selected properly.     

用于光码分多址系统中的跳频地址码研究

研究了光正交码,EQC码和素数码与频率相结合构成的单跳频及多跳频二维地址码,并对它们的容量与采用波分复用系统时的容量进行了比较,得到了比采用跳频地址码容量更大的结论。     

Performance of group ordered successive interference cancellation for multiuser detection in GSTBC SFH/MC DS‐CDMA system

In this paper, we present a novel group space‐time block coding slow frequency‐hopping multicarrier direct‐sequence code division multiple access (GSTBC SFH/MC DS‐CDMA) system over frequency selective fading channels. The proposed scheme greatly improves the bandwidth‐efficient through assigning the users employing the same frequency‐hopping (FH) pattern. Moreover, the users employing the same FH pattern are assigned into different virtual groups, in which the users are assigned to the different spreading codes, while the users are assigned to the same spreading code in the same virtual group. Then, a novel group detection scheme that we denote by group ordered successive interference cancellation (GOSIC) is presented to suppress the interference between the different virtual groups. Our proposed scheme consists of ordering group at the receiver side in order to maximize the overall system performance, and carrying BLAST‐STBC (LSTBC) detection for the users in the same virtual group. We define and derive the optimal group order based on the post group signal to interference plus noise ratio (PGSINR). We also propose another suboptimal group order in order to overcome the complexity issues. Finally, we compare the performance of our proposed GOSIC with conventional group successive interference cancellation (GSIC), conventional STBC multiuser detection (MUD), and LSTBC‐MUD, and show that significant improvement is introduced. Finally, it is shown that the proposed scheme is robust to the imperfect channel estimation. Copyright © 2006 John Wiley & Sons, Ltd.     

Optimal SIR for an hybrid cellular DS/SFH CDMA system

A hybrid direct‐sequence/slow frequency hopping code‐division multiple‐access (DS/SFH CDMA) system operating in a Rayleigh fading environment is described and its spectral efficiency is estimated in terms of the theoretically achievable average channel capacity (in the sense of information theory) per user. The analysis covers the operation over a broadcast cellular time‐varying link and leads to a simple novel closed‐form expression for the optimal average spread signal‐to‐interference power ratio (SIR) received by each user based on the maximization of the achieved spectral efficiency. Copyright © 2007 John Wiley & Sons, Ltd.     

Slow frequency-hopping multicarrier DS-CDMA for transmission overNakagami multipath fading channels

A novel multiple access scheme based on slow frequency hopping multicarrier direct-sequence code division multiple access (SFH/MC DS-CDMA) is proposed and investigated, which can be rendered compatible with the existing second-generation narrowband CDMA and third-generation wideband CDMA systems. The frequency hopping patterns are controlled by a set of constant-weight codes. Consequently, multirate communications can be implemented by selecting the corresponding sets of constant-weight codes having the required weights controlling the SFH patterns invoked. Two FH schemes, namely random and uniform FH, are considered and their advantages as well as disadvantages are investigated. We assume that the system operates in a multipath fading environment and a RAKE receiver structure with maximum ratio combining (MRC) is used for demodulation. The system's performance is evaluated over the range of multipath Nakagami (1960) fading channels, under the assumption that the receiver has all explicit knowledge of the associated frequency-hopping (FH) patterns invoked. Furthermore, the performance of the SFH/MC DS-CDMA system is compared to that of the conventional single-carrier (SC) DS-CDMA system and that of the conventional MC DS-CDMA system, under the assumptions of constant system bandwidth and of constant transmitted signal power     

Spectral efficiency for a hybrid DS/FH code-divisionmultiple-access system in cellular mobile radio

The spectral efficiency of a hybrid cellular direct-sequence/frequency hopping code-division muItiple-access (DS/FH-CDMA) system operating in a Rayleigh-fading environment is examined. In this work, spectral efficiency is evaluated in terms of the theoretically achievable channel capacity (in the Shannon sense) per user, on the condition that this is estimated in an average sense. The analysis covers the downlink assuming a static model of operation and a direct-sequence/slow-frequency hopping (DS/SFH) as well as a direct-sequence/fast-frequency hopping (DS/FFH) scheme. As it is shown, the spectral efficiency of cellular DS/FFH-CDMA operating in a Rayleigh-fading environment is greater than that of broad-band DS- and DS/SFH-CDMA systems operating under normalized conditions. This is justified by the combination of path-diversity reception as achieved by conventional coherent RAKE receivers and the frequency diversity that is inherently present in FFH transmission