Automated network management and configuration using Probabilistic Trans-Algorithmic Search

Online configuration of large-scale systems such as networks requires parameter optimization within a limited amount of time, especially when configuration is needed as a response to recover from a failure in the system. To quickly configure such systems in an online manner, we propose a Probabilistic Trans-Algorithmic Search (PTAS) framework which leverages multiple optimization search algorithms in an iterative manner. PTAS applies a search algorithm to determine how to best distribute available experiment budget among multiple optimization search algorithms. It allocates an experiment budget to each available search algorithm and observes its performance on the system-at-hand. PTAS then probabilistically reallocates the experiment budget for the next round proportional to each algorithm’s performance relative to the rest of the algorithms. This “roulette wheel” approach probabilistically favors the more successful algorithm in the next round. Following each round, the PTAS framework “transfers” the best result(s) among the individual algorithms, making our framework a trans-algorithmic one. PTAS thus aims to systematize how to “search for the best search” and hybridize a set of search algorithms to attain a better search. We use three individual search algorithms, i.e., Recursive Random Search (RRS) (Ye and Kalyanaraman, 2004), Simulated Annealing (SA) (Laarhoven and Aarts, 1987), and Genetic Algorithm (GA) (Goldberg, 1989), and compare PTAS against the performance of RRS, GA, and SA. We show the performance of PTAS on well-known benchmark objective functions including scenarios where the objective function changes in the middle of the optimization process. To illustrate applicability of our framework to automated network management, we apply PTAS on the problem of optimizing link weights of an intra-domain routing protocol on three different topologies obtained from the Rocketfuel dataset. We also apply PTAS on the problem of optimizing aggregate throughput of a wireless ad hoc network by tuning datarates of traffic sources. Our experiments show that PTAS successfully picks the best performing algorithm, RRS or GA, and allocates the time wisely. Further, our results show that PTAS’ performance is not transient and steadily improves as more time is available for search.     

Uplink Scheduling in CDMA Packet-Data Systems

Uplink scheduling in wireless systems is gaining importance due to arising uplink intensive data services (ftp, image uploads etc.), which could be hampered by the currently in-built asymmetry in favor of the downlink. In this work, we propose and study algorithms for efficient uplink packet-data scheduling in a CDMA cell. The algorithms attempt to maximize system throughput under transmit power limitations on the mobiles assuming instantaneous knowledge of user queues and channels. However no channel statistics or traffic characterization is necessary. Apart from increasing throughput, the algorithms also improve fairness of service among users, hence reducing chances of buffer overflows for poorly located users. The major observation arising from our analysis is that it is advantageous on the uplink to schedule “strong” users one-at-a-time, and “weak” users in larger groups. This contrasts with the downlink where one-at-a-time transmission for all users has shown to be the preferred mode in much previous work. Based on the optimal schedules, we propose less complex and more practical approximate methods, both of which offer significant performance improvement compared to one-at-a-time transmission, and the widely acclaimed Proportional Fair (PF) algorithm, in simulations. When queue content cannot be fed back, we propose a simple modification of PF, Uplink PF (UPF), that offers similar improvement. Hereafter, we refer to users with low recieved power at the base even when transmitting at peak transmit power as “weak” users, and the strongly recieved users at the base as “strong” users. Krishnan Kumaran is currently a member of the Complex Systems Modeling section in the Corporate Strategic Research of ExxonMobil Corp., Clinton, NJ. Formerly, he was a Member of Technical Staff in the Mathematics of Networks and Systems Research Department at Bell Labs in Murray Hill, NJ, where his research interests were in modeling, analysis and simulation of design, resource management and scheduling issues in telecommunication networks. Lijun Qian is an assistant professor in the Department of Electrical Engineering at Prairie View A&M University. He received his B.S. from Tsinghua University in Beijing, M.S. from Technion-Israel Institute of Technology, and Ph.D. from WINLAB, Rutgers University, all in electrical engineering. Before joining PVAMU, he was a researcher at Networks and Systems Research Department of Bell Labs in Murray Hill, NJ. His major research interests are in wireless communications and networking technologies, especially in radio resource management, protocol design, TCP/RLP optimization and MPLS traffic engineering.     

火工品压药机装配误差的研究

针对军用雷管生产线中压药机结构,分别用极值法和概率法对压药机冲子和雷管的配合精度,进行了装配尺寸链的描述和计算,并对所得的结果进行了比较。     

超媒体系统中的人工智能方法

一、什么是超媒体近年来迅速崛起的多媒体(multimedia)技术,是一种使计算机具有交互式地综合处理和管理文字、图形、图象、声音、视频等多种媒体能力的技术,必将使计算机技术发生一     

I/OIMAGESYSTEM微波中继应用

微波中继的应用非常广泛 ,目前在二维、三维施工中跨越障碍物时 ,一般都使用微波中继站来传输命令和数据。文章就微波中继及I/OIMAGESYSTEM“蛇形排列”先进功能的实际应用进行了详细的阐述 ,同时提出了使用微波中继站应注意的问题。     

常规施工中不容忽视的几个环节

就毛石砌体的拉接处理、现浇混凝土柱、墙拉结筋的留设、砖混结构中构造柱的质量预控等几个环节进行了分析，提出只有在施工中采取必要的措施，才能保证施工质量。     

Choice With Initial and Terminal Link Reinforcement: An Alternative Self-Control Paradigm.

Self-control is demonstrated when a less desirable immediate outcome is chosen to ensure a substantially better future. In a novel animal analogue of this situation, primary reinforcement was delivered in both the initial and terminal links of a concurrent chain schedule. Rats made initial link choices between equal amounts of ethanol-free or ethanol-containing milk. Choosing the ethanol-free reinforcer resulted in delivery of the larger terminal link reinforcer and was thus analogous to self-control. Self-control decreased as the delay between initial and terminal links increased. The results have implications for human choice situations where decisions are made between two immediately available reinforcement alternatives each associated with a different delayed outcome. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fault-aware Communication Mapping for NoCs with Guaranteed Latency

As feature sizes shrink, transient failures of on-chip network links become a critical problem. At the same time, many applications require guarantees on both message arrival probability and response time. We address the problem of transient link failures by means of temporally and spatially redundant transmission of messages, such that designer-imposed message arrival probabilities are guaranteed. Response time minimisation is achieved by a heuristic that statically assigns multiple copies of each message to network links, intelligently combining temporal and spatial redundancy. Concerns regarding energy consumption are addressed in two ways. First, we reduce the total amount of transmitted messages, and, second, we minimise the application response time such that the resulted time slack can be exploited for energy savings through voltage reduction. The advantages of the proposed approach are guaranteed message arrival probability and guaranteed worst case application response time.     

基于TS101型DSP链路口的多通道高精度数据采集电路设计

介绍一种基于数字信号处理器(DSP)TS101链路口的多通道高精度数据采集电路的设计方法,详细阐述利用多个ADS8361型A/D转换器进行数据采集,并经TS101链路口传输数据的FP-GA和DSP设计实现,讨论如何提高A/D转换精度的问题.     

针对混合应用业务的ARQ改进方案

在高速无线通信中,自动请求重传(ARQ)是链路层不可缺少的技术,它通过重传向上层屏蔽无线链路上包的丢失。随着无线网络的发展,无线传输速率不断提高,应用的业务类型也越来越广泛。目前,众多ARQ技术的研究都集中在如何提高该技术的确认效率,以适应更高的传输速率,但鲜有研究着手于如何使ARQ能够更好地应用于混合业务环境。针对混合业务环境下的ARQ改进提出了2种方案,并给出其中1种在实际应用中的改善效果。