Bandwidth Efficient All-to-All Broadcast on Switched Clusters

Clusters of workstations employ flexible topologies: regular, irregular, and hierarchical topologies have been used in such systems. The flexibility poses challenges for developing efficient collective communication algorithms since the network topology can potentially have a strong impact on the communication performance. In this paper, we consider the all-to-all broadcast operation on clusters with cut-through and store-and-forward switches. We show that near-optimal all-to-all broadcast on a cluster with any topology can be achieved by only using the links in a spanning tree of the topology when the message size is sufficiently large. The result implies that increasing network connectivity beyond the minimum tree connectivity does not improve the performance of the all-to-all broadcast operation when the most efficient topology specific algorithm is used. All-to-all broadcast algorithms that achieve near-optimal performance are developed for clusters with cut-through and clusters with store-and-forward switches. We evaluate the algorithms through experiments and simulations. The empirical results confirm our theoretical finding.     

Theory and implementation of path planning by negotiation for decentralized agents

This paper presents a cooperative decentralized path-planning algorithm for a group of autonomous agents that provides guaranteed collision-free trajectories in real-time. The algorithm is robust with respect to arbitrary delays in the wireless traffic, possible sources being transmission time and error correction. Agents move on reserved areas which are guaranteed not to intersect, therefore ensuring safety. A handshaking procedure guarantees recent information states for the agents. Conflicts between agents are resolved by a cost-based negotiation process. The basic algorithm is augmented by the introduction of waypoints, which increase performance at the cost of additional wireless traffic. An implementation of the algorithm is tested in simulation and successfully applied to a real system of autonomous robots. The results are presented and discussed.     

A power and data front-end IC for biomedical monitoring systems

To enable the evolution towards electronically assisted healthcare, future medical implants require sensors and processing circuitry to inform patient and doctor on the rehabilitation status. An important branch of systems are those where implant strain is monitored through strain gauges. Since batteries inside the human body are avoided as much as possible, a transcutaneous power link is used to wirelessly power the implant. The same RF link provides an elegant way of establishing bi-directional data communication between the external base station and the medical device. This paper describes a front-end IC that manages both power reception and bi-directional data communication. It has a clock generation circuit on board to drive additional digital processing circuits. A new architecture that uses a current driven data demodulation principle is introduced. It is able to detect an AM signal with modulation depth of a mere 4%, which is better than recent similar systems in the field. The IC is fabricated in a solid 0.35 μm HVCMOS technology and consumes only 0.56 mA.     

An efficient hybrid multicast transport protocol for collaborative virtual environment with networked haptic

In recent years, we have witnessed a growing interest in the synchronous collaboration based class of applications. Several techniques for collaborative virtual environments (CVE), haptic, audio and visual environments (C-HAVE) have been designed. However, several challenging issues remain to be resolved before CVE and C-HAVE become a common place. In this paper, we focus on applications that are based on closely coupled and highly synchronized haptic tasks that require a high-level of coordination among the participants. Four main protocols have been designed to resolve the synchronization issues in such environments: the synchronous collaboration transport protocol, the selective reliable transmission protocol, the reliable multicast transport protocol and the scalable reliable multicast. While these four protocols have shown good performance for CVE and C-HAVE class of applications, none of these protocols has been able to meet all of the basic CVE requirements, i.e., scalability, reliability, synchronization, and minimum delay. In this paper, we present a hybrid protocol that is able to satisfy all of the CVE and C-HAVE requirements and discuss its implementation and results in two tele-surgery applications. This work is partially supported by Grants from Canada Research Chair Program, NSERC, OIT/Ontario Distinguished Researcher Award, Early Research Award and ORNEC Research Grant.     

一种交换式以太网拓扑结构的发现算法

首先介绍了目前局域网拓扑发现的主要方法及存在的问题,然后提出一个基于生成树协议 地址转发表的交换式以太网物理拓扑结构的自动发现算法.算法首先利用生成树协议建立起交换机之间的连接关系,在此基础上进一步利用地址转发表建立起交换机与主机的连接关系.该算法 1)能给发现被生成树协议阻塞的连接;2)通过处理连接冲突,能够准确无误的发现网络物理拓扑结构;3)算法开销小,时间复杂度低.文中算法已成功地应用于社区宽带综合业务网络管理系统(CBISNMS)中.     

一种高效嵌入式协议栈缓冲区管理机制

提出一种MYBUF高效嵌入式协议栈两级缓冲区管理机制,该机制基于内存保护模式,具有可配置性,支持静态、动态分配和回收.使用该缓冲区管理机制可使嵌入式TCP/IP协议栈各层之间实现零拷贝数据传递.在基于自主开发的HDTV(High Definition Television)双向系统平台上的测试结果表明,该管理机制完全满足嵌入式系统网络通信的应用需求,是一种高效、简洁、可靠的缓冲区管理机制.不失一般性,本文设计的MYBUF缓冲区管理机制可适用于其它嵌入式网络通信系统.     

一种新的球形解码初始半径确定方法

球形解码(Sphere Decoding, SD)是多输入多输出系统(MIMO)系统中一种非常高效的解码算法.它的初始搜索半径对算法的计算复杂度有很大的影响.提出一种名为 IR-ZF-OSUC的初始搜索半径确定方法.它利用了SD内嵌的QR分解结果来得到初始半径.相比其他类似方法,因半径更为接近最优值,且无需专门的处理步骤,使SD具有更低的计算复杂度.仿真表明,使用IR-ZF-OSUC来确定初始半径的SD相比基于其他策略的SD,在很宽的SNR范围内具有最低的计算复杂度.     

超宽带无线传感器网络MAC协议

超宽带技术凭借其诸多优势成为无线传感器网络物理层的绝佳选择,同时也为无线传感器网络的MAC协议设计带来了挑战。该文介绍了超宽带信号模型,讨论了UWB MAC协议设计中亟待解决的问题,总结和分析了近年来提出的几种典型的UWB MAC协议和有代表性的研究成果,并展望了下一步的研究方向。     

分布式网络流量监测

分析2种现行网络流量监测技术：利用标准的网络管理方法记录IP流量和利用NETFLOW的方法进行流量统计。针对这2种方法的局限性,提出分布式网络流量监测方法。该方法采用Client/Server结构,局域网各个终端参加流量统计,并将结果传送给流量监测服务器。该方法适合大型局域网的流量监测,具有良好硬件适应性,大大降低了流量监测服务器的工作量,提高了网络性能。