CAREER

职业

• 批准号: 0093349
• 负责人: Muriel Medard
• 金额: $ 25万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-01 至 2006-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0093349&HistoricalAwards=false
• 关键词: CAREER

CCR-0093349ABSTRACTThis project investigates aspects of reliable communications for verydifferent types of network variability.The first part of the project is concerned with capacity and robustness ofnetworks to permanent failures such as removal of a link or node. Theapproach in this project moves away from a pure graph-theoretic approach,based purely on routing, to consider network capacity using an algebraicframework. Capacity is considered as the characterization of the set ofconnections that can be supported by a network in which the nodes are notonly capable of traditional routing functions, but can also performprocessing of the data that arrives to them. Such processing is consideredas a code over the network. Coding is also applied to recovery to maintaincertain connections in a network even after failure of a portion of thenetwork, for instance after the disappearance of a link in the network. Thesecond part of the project considers robustness in channels where fadingvaries over both time and frequency, especially over ultra wide frequencybands. The goal of this part of the project is to establish theoreticalresults that relate capacity, peak power, energy, bandwith and probabilityof error in such a way as to characterize the practical achievableperformance in wide band wireless systems.The first part of this project investigates the reliability of networksunder normal and failure conditions when coding is used to ensurecontinuity of connections. This project shows that traditional methods ofrecovery in networks, such as rerouting, are subsets of network coding andestablishes coding methods to increase the realibility of networks underfailure conditions. Moreover, the projects investigates the issue of networkmanagement, where network management represents the information needed tomodify the behavior of the network, defined as the code of the network, inresponse to failures. The algebraic approach taken in this project allowssome characterization of the fundamental limits of the number of bitsrequired to effect changes on the network code and of the portions of thenetwork that require knowledge of failures. The second part of the projectconsiders capacity of very wide band channels and the applicability ofdifferent types of signals and codes to achieve performance at or near thetheoretical maximum. In particular, it explores to what extent very highpeak power symbols, which are known to achieve capacity in the limit of verylarge bandwidths, are necessary to achieve capacity. The project alsoexplores the ranges of bandwidth in which ultra-wideband results areachievable. This work bridges the theoretical limits of the channel(capacity) with the applicability of the techniques that achieve capacity byproviding an explicit bound to the probability of error in terms of rate,bandwidth and peak power of the signal. Finally, the project consider theapplicability, in the range of moderate to large bandwidths, of traditionalspread spectrum approaches, such as direct-sequence code-division multipleaccess, that perform poorly in the limit of very large bandwidths.

CCR-0093349摘要本项目研究不同类型网络可变性的可靠通信方面，项目的第一部分关注网络对永久故障（如链路或节点的移除）的容量和鲁棒性。在这个项目中的方法从纯粹的图论方法，纯粹基于路由，考虑网络容量使用代数框架。容量被认为是一个网络所能支持的连接集的特征，在这个网络中，节点不仅能够完成传统的路由功能，而且还能够处理到达它们的数据。这种处理被认为是网络上的代码。编码也被应用于恢复，即使在网络的一部分出现故障之后，例如在网络中的链路消失之后，也能保持网络中的某些连接。该项目的第二部分考虑在衰落随时间和频率变化的信道中的鲁棒性，特别是在超宽频带上。本项目的这一部分的目标是建立理论结果，与容量，峰值功率，能量，带宽和错误的概率，在这样一种方式，以表征在宽带无线系统的实际可接受的性能。本项目的第一部分调查的可靠性网络在正常和故障条件下，当使用编码，以确保连接的连续性。该项目表明，传统的网络恢复方法，如重路由，是网络编码的子集，并建立编码方法，以增加网络故障条件下的实时性。此外，这些项目还调查了网络管理问题，其中网络管理代表了修改网络行为所需的信息，定义为网络代码，以应对故障。在这个项目中采取的代数方法允许一些表征的基本限制所需的位数的影响网络代码的变化和部分的thenetwork需要知识的故障。该项目的第二部分考虑了非常宽的频带信道的容量和不同类型的信号和代码的适用性，以达到或接近理论最大值的性能。特别是，它探讨了在多大程度上非常高峰值功率的符号，这是已知的，以实现容量的限制非常大的带宽，是必要的，以实现容量。该项目还探讨了超宽带结果可实现的带宽范围。这项工作的桥梁的理论限制的信道（容量）的技术，实现能力通过提供一个明确的约束的概率错误的速率，带宽和峰值功率的信号的适用性。最后，该项目考虑了传统的扩频方法（如直接序列码分多址）在中到大带宽范围内的适用性，这些方法在非常大的带宽限制下表现不佳。