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Abstract
Wireless sensor 美国留学生信息技术论文 networks are built upon a shared medium that makes it easy for adversaries to conduct radio interference, or jamming, attacks that effectively cause denial of service of either transmission or reception functionalities. These attacks can easily be accomplished by an adversary by either bypassing MAC-layer protocols or emitting a radio signal targeted at jamming a particular channel. In this article we survey different jamming attacks that may be employed against a sensor network. In order to cope with the problem of jamming, we discuss a two-phase strategy involving the diagnosis of the attack, followed by a suitable defense strategy. We highlight the challenges associated with detecting jamming. To cope with jamming, we propose two different but complementary approaches. One approaches to simply retreat from the interferer, which may be accomplished by either spectral evasion (channel surfing) or spatial evasion (spatial retreats). The second approach aims to compete more actively with the interferer by adjusting resources, such as power levels and communication coding, to achieve communication in the presence of the jammer.

Securing sensor networks is a challenging task due tithe limited resources associated with low-cost sensor hardware. The combination of the commodity nature of wireless technologies and an increasingly sophisticated user base means that adversaries are able to easily gain access to communications between sensor devices by purchasing their own device and running it in a monitor mode. Conventional cryptographic security mechanisms are being translated to the sensor domain in order to defend against attacks like packet injection and spoofing networklevelcontrol information. However, in spite of the progress being made to apply network security in the sensor realm, sensor networks will remain vulnerable to attacks that target their use of the wireless medium.
The wireless medium allows for radio interference attacks that target communications. Unlike traditional denial of service attacks, which are concerned with filling user domain and kernel domain buffers, jamming attacks exploit the shared nature of the wireless medium in order to prevent devices from communicating or receiving. Such attacks on the physical (PHY) layer have been known by the communications and radar community for some time, and there are numerous texts, such as [1, 2], which discuss the issues associated with these attacks. Typically, in the context of traditional communication systems, the objective of the jammer into denies the reception of communications at the receiver using as little power as possible. In these systems jamming is usually addressed through spreading techniques, whereby resilience to interference is achieved by transmitting information using a bandwidth much larger than its required minimum bandwidth. Often, this spreading is also used to achieve multiple access, as in code-division multiple access (CDMA) cellular systems

With the exception of some military systems, most commodity Sensor and wireless networks do not employ sufficiently strong spreading techniques to survive jamming or to achieve multiple accesses. Instead, for reasons of cost, systems like the Berkeley MICA2, the Sigsbee (e.g., MICAZ), and even 802.11 are based on a carri本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。