外文翻译：ad_hoc网络的一个简要概述：挑战与研究方向(编辑修改稿)

外文翻译：ad_hoc网络的一个简要概述：挑战与研究方向(编辑修改稿)内容摘要：

gration between the processes of movement, decisionmaking, and working that allow them to modify their actions while taking into account the effects on many different system aspects [12]. Similarly,sensors are often deployed in a way that makes their roles and capabilities redundant, suggesting new ways of bining application knowledge of delivered information with the routing layer [13]. Finally, a problem that overarches all these others is the lack of well defined and widely accepted models for RF path attenuation, mobility, and traffic. These tightly interrelated models are needed for quantifying and paring ad hoc system performance to a mon physical processes of refraction, reflection, and scattering of RF radiation is moderately well understood but difficult to quantify in detail when including a large number of plex objects such as foliage, cars, or buildings. In contrast,the pattern of movement of the nodes and the flow of traffic can certainly be easily described in detail, but the dependency on the target application, the lack of existing systems available for study, and the likely interactions between connectivity, movement, and user applications,causes these models to be illdefined. The Future Imagine the following scenarios: a wireless mesh of rooftopmounted ad hoc routers。 an ad hoc work of cars for instant traffic and other information。 sensors and robots forming a multimedia work that allows remote visualization and control。 multiple airborne routers (from tiny robots to blimps) automatically providing connectivity and capacity where needed (., at a football game)。 an ad hoc work of spacecraft around and in transit between the Earth and Mars. These may seem like science fiction, but are in fact ideas pursued seriously by the ad hoc research munity. While only time can tell which of these imagined scenarios will bee real, the above offers a glimpse into both the technological potential and the evolving state of the art. We discuss in this section the forces at play 5 that are likely to shape the future of ad hoc working, and discuss the directions in which it may evolve. To appreciate the role ad hoc works are likely to play in the future, consider this: bandwidthhungry applications and the laws of physics drive wireless architectures away from cellular toward ad hoc. This is because more capacity implies the need for a higher munications bandwidth and better spatial spectral bandwidth is found at higher frequencies,where the propagation is dismal. Further, mobile devices have to be powerthrifty. Propagation,spectral reuse, and energy issues support a shift away from a single long wireless link (as in cellular) to a mesh of short links (as in ad hoc works).That this might be the wave of the future is attested to by burgeoning startups, .,Rooftop Communications (now part of Nokia),Mesh Networks, and Radiant Networks, that use a multihop meshbased39。 39。 architecture in place of conventional 3G architectures. The other main impetus to ad hoc works es from the rapidly improving munications munication devices are getting smaller, cheaper, more sophisticated, and hence more of these technologies for better ad hoc working gives rise to new problems that point to new research. For instance, the use of smart antennas in ad hoc working requires new medium access and neighbor discovery ability to dynamically alter spread spectrum codes, modulation schemes, and waveforms require corresponding innovations at the higher layers. Softwar。