自动控制文献翻译——摘要：基于IEEE 802.11的WLAN系统已经获得了跨EST在军事和公权力的环境，那里的无线电条件苛刻因故意堵塞明使用。无线电环境是很困难的，商业和民用部署以来，未经许可频段拥挤。为了研究这些问题，我们建立了一个试验台具有控制信号路径来衡量不同的干扰， ING信号的影响，以无线局域网通信。我们用连续的宽带噪声干扰作为比较点，并专注于研究脉冲干扰以及频率扫描果酱明的效果。此外，我们还考虑介质访问控制（MAC ）的干扰。基于这些结果， WLAN系统似乎并不对本测试短噪声干扰脉冲敏感。在较长的脉冲，其影响可见，和较长的数据帧都更容易受到干扰比短。事实上，在一个数据流中即使有少量长帧可以毁掉的性能在整个环节。根据扫频干扰，慢扫描与窄带干扰信号可以是相当有害的无线局域网通信。 MAC果酱明的结果表明，不同设备之间的显著差异表现在：一些设备的空闲信道评估（ CCA ）机制可以通过使用无线局域网般的干扰信号很容易卡住。作为副产品，该研究还揭示了一些解决对策干扰。

关键词 : 脉冲；连续的；音宽带；噪音；干扰；测量；跨层

一、引言

非故意干扰，造成在相同或相邻频段工作的各种无线系统，或如重工机械，可以在民用和商业环境阻碍无线通信。无线电环境中是很困难的特别是在未经许可的工业，科学和医疗（ISM ）频段，其中多数流行的基于IEEE 802.11的无线局域网系统的工作。由于技术的成熟，广泛的利用，能设备，易于部署，而且成本低， WLAN系统都获得了利益也是在军事和公权力的环境，这里的无线电环境可能是由于极其恶劣的被使用故意干扰。不断增长的需求多样化的传播刘先洋，刘晓红化意识在信息作战环境比传统的现场无线电系统重新要求更多容量时使用多媒体可以提供。这些原因提出对各种干扰的情况下站立的WLAN系统的实用性能的利益。在本文中，常见的术语的WLAN被用来指基于IEEE 802.11的无线局域网标准[1]，和IEEE 802.11被简称为802.11。

在公开文献中，存在过多的对中的干扰信号的存在无线电链路的性能的研究。然而，覆盖WLAN系统的研究大多是基于模拟，而少数已发表的测量研究集中在连续干扰波形。我们建立了一个试验台具有控制信号路径来衡量不同的干扰信号的影响，以无线局域网通信。对于这些测试，我们选择了一组不同种类的七个厂家的设备组成。而连续的宽带噪声干扰提供了比较的角度来看，我们专注于研究脉冲干扰和扫频干扰的效果。此外，通过了解WLAN的渠道交流塞斯过程中的薄弱环节，我们认为MAC干扰。

二、相关工作

在文献中，一些研究可以对干扰的WLAN系统具有连续的宽带噪声[2]，或者通过蓝牙产生的信号中找到[3]，紫蜂[4]，或在相同的频带操作的其它无线局域网[5]的设备。然而，文献中讨论了物理（PHY）的干扰和WLAN系统与脉冲和扫频干扰的MAC层不是很广阔。

至少两个先前发表的论文讨论了WLAN网络与脉冲信号的干扰。在[6]中，假设传输是双向的IP语音（ VoIP）的下研究了脉冲干扰的对802.11a/b/g的MAC层的性能和容量的影响。基于模拟的文章是，和一个基本假设是，该干扰脉冲破坏了整个MAC帧，如果脉冲击中的MAC帧。文献[ 7 ]的研究也基于模拟，它侧重于中头米或瑞利衰落下的脉冲干扰铭基于802.11a的链接无线信道的影响。没有发现基于测量的脉冲下，干扰WLAN系统的研究。尽我们所知，研究直接专注于扫频干扰都没有公布在公开此功能的文献。这些研究侧重于窄带连续干扰是最接近这个话题，见[ 2 ]和[ 8 ] - [ 13 ] 。在一般情况下，它可概括，基于正交频分复用（OFDM）的传输模式是对所使用的窄带频率敏感干扰信号，而基于直接序列扩频（DSSS）的模式是不敏感的干扰频率，.......

Abstract

IEEE 802.11 based WLAN systems have gained interest to be used in the military and public authority environments, where the radio conditions can be harsh due to intentional jamming. The radio environment can be difficult also in commercial and civilian deployments since the unlicensed frequency bands are crowded. To study these problems, we built a test bed with a controlled signal path to measure the effects of different interfering signals to WLAN communications. We use continuous wideband noise jamming as the point of comparison, and focus on studying the effect of pulsed jamming and frequency sweep jamming. In addition, we consider also medium access control (MAC) interference. Based on the results, WLAN systems do not seem to be sensitive to the tested short noise jamming pulses. Under longer pulses, the effects are seen, and long data frames are more vulnerable to jamming than short ones. In fact, even a small amount of long frames in a data stream can ruin the performance of the whole link. Under frequency sweep jamming, slow sweeps with narrowband jamming signals can be quite harmful to WLAN communications. The results of MAC jamming show significant variation in performance between the different devices: The clear channel assessment (CCA) mechanism of some devices can be jammed very easily by using WLAN-like jamming signals. As a side product, the study also revealed some countermeasures against jamming. 

I.INTRODUCTION

Unintentional interference, caused by various radio systems operating in the same or adjacent frequency bands or, e.g., heavy industry machinery, can hinder wireless communications in civilian and commercial environments. The radio environment can be difficult especially in the unlicensed industrial, scientific and medical (ISM) frequency bands, where the majority of the popular IEEE 802.11 based WLAN systems operate. Due to the maturity of the technology, wide range of available devices, easy deployment, and low cost, WLAN systems have gained interest also to be used in the military and public authority environments, where the radio environment can be exceedingly harsh due to intentional jamming. The growing demand to use multimedia when disseminating diverse situation awareness information in operational environments requires more capacity than the traditional field radio systems can provide. These reasons raise the interest towards the understanding of practical performance of WLAN systems in various interference scenarios. In this paper, the common term WLAN is used to refer to the IEEE 802.11 based WLAN standards [1], and IEEE 802.11 is referred simply as 802.11.

In the public literature, there exists a plethora of studies on the performance of radio links in the presence of interfering signals. However, the studies covering WLAN systems are mostly simulation based, while the few published measurement studies focus on continuous interfering waveforms. We built a test bed with a controlled signal path to measure the effects of different interfering signals to WLAN communications. For the tests, we chose a set of different kind of devices from seven manufacturers. While the continuous wideband noise jamming provides the point of comparison, we focus on studying the effect of pulsed jamming and frequency sweep jamming. In addition, by knowing the weak points of WLAN channel access procedure, we consider also MAC interference.

The rest of this paper if organized as follows. Section II briefly reviews the related work while Section III introduces the measurement setup used in this study. After that, Section IV presents the measurement results and, finally, Section V contains the conclusions.......