成都市城市交通与城市空间结构整体优化研究

成都市目前日益拥挤的城市交通和单中心摊大饼式扩展的城市空间结构与实现城市可持续发展的目标背道而驰。城市交通与城市空间结构存在着复杂的相互影响、相互反馈关系,因此不能撇开一方而孤立地谈另一方的优化。本文主张以总结成都市城市交通与城市空间结构的历史演变规律为突破口,分析导致城市交通与城市空间结构不健康发展的根本原因,从而提出成都市城市交通与城市空间结构整体优化的策略。     

Queuing analysis of shared-buffer switches with control scheme under bursty traffic

Shared-buffer switches have many advantages such as relatively low cell loss rate and good buffer utilization, and they are increasingly favoured in recent VLSI switch designs for ATM. However, their performance degrades dramatically under nonuniform traffic due to the monopolization of the buffer by some favoured cells. To overcome this, restricted types of sharing and hot-spot pushout (HSPO) have been proposed, and the latter has been shown by simulation to perform better in all situations. In this paper we develop an analytical model for performance evaluation of a shared-buffer asynchronous transfer mode (ATM) switch with HSPO under bursty traffic. This analytical model is an improved version of the first model ever developed for this purpose. We balance the relative queues to approximate the effects of pushout, while keeping only four state-variables, and our model gives a good agreement with simulation, for calculating throughput and cell loss.     

浅析公路桥头跳车原因与解决措施

从地基土质、台背填料压缩、刚柔突变几方面分析了桥头跳车产生的原因，并从地基处理、路基处理、路面处理三方面提出了解决桥头跳车的措施，以确保行车顺畅，保证行车安全性。     

Stability of traffic patterns in broadband networks

The control of telephony traffic is the task of network management and routing algorithms. In this paper, a study of two trunk groups carrying telephony traffic is used to show that instabilities can arise if there is a delay in getting feedback information for a network controller. The network controller seeks to balance the traffic in the two trunk groups, which may represent two paths from a source to a destination. An analysis shows how factors such as holding time, controller gain and feedback delay influence stability. Simulation of a two service case is also carried out to show that the same instabilities can arise.     

Traffic Measurement for Traffic Engineering in IP/MPLS Based Telecom Core Networks

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A distributed laxity-based priority scheduling scheme for time-sensitive traffic in mobile ad hoc networks

Characteristics of Mobile Ad hoc Networks such as shared broadcast channel, bandwidth and battery power limitations, highly dynamic topology, and location dependent errors, make provisioning of quality of service (QoS) in such networks very difficult. The Medium Access Control (MAC) layer plays a very important role as far as QoS is concerned. The MAC layer is responsible for selecting the next packet to be transmitted and the timing of its transmission. We have proposed a new MAC layer protocol that includes a laxity-based priority scheduling scheme and an associated back-off scheme, for supporting time-sensitive traffic. In the proposed scheduling scheme, we select the next packet to be transmitted, based on its priority value which takes into consideration the uniform laxity budget of the packet, the current packet delivery ratio of the flow to which the packet belongs, and the packet delivery ratio desired by the user. The back-off mechanism devised by us grants a node access to the channel, based on the rank of its highest priority packet in comparison to other such packets queued at nodes in the neighborhood of the current node. We have studied the performance of our protocol that combines a packet scheduling scheme and a channel access scheme through simulation experiments, and the simulation results show that our protocol exhibits a significant improvement in packet delivery ratio under bounded end-to-end delay requirements, compared to the existing 802.11 DCF and the Distributed Priority Scheduling scheme proposed recently in [ACM Wireless Networks Journal 8 (5) (2002) 455–466; Proceedings of ACM MOBICOM '01, July 2001, pp. 200–209].     

THE RELATIONS BETWEEN MODEL PARAMETERS AND CERTAIN PHENOMENA IN TRAFFIC FLOW

Based on the dimensionless dynamic model of traffic flow, the model parameters were compared with numerically simulating solutions, and the effects of the former on the latter was investigated. Some relations between the parameters were obtained. Investigation several idealized results from dimensionless dynamic model of traffic flow were concluded.     

交通视频监控系统中TMS320DM642与嵌入式PC/104+模块的通信

描述了TI公司媒体处理器TMS320DM642HPI的主要特点，介绍了PCI桥接器PCI2040的结构原理，提出了通过PCI2040实现TMS320DM642与PC／104＋模块进行通信的设计方案。本方案充分利用PCI总线的高数据吞吐能力和DSP的HPI接口功能，可在DSP和PC／104＋模块之间实现较高的数据传输率，实现了PC／104＋实时读／写DSP任意片内存储单元的内容。最后给出交通视频监控系统的设计方案，详细说明了通信过程的软件编程。     

A Wireless LAN Bridging Solution Based on Campus Network

This paper presents a creative wireless LAN (WLAN) bridging solution, concentrating on the overall realization of a well designed interconnection. This solution integrates effective traffic insulation, intended access control, and required address translation without interfering with the vested interest of internet service provider (ISP). The specific solution can be widely applied on the campus-dorm (off campus)-ISP internetworking mode, where it is hard to implement wired link between campus network and dorm network in terms of cost and existing environmental constraints.