4,035 research outputs found

    Fast interconnect optimization

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    As the continuous trend of Very Large Scale Integration (VLSI) circuits technology scaling and frequency increases, delay optimization techniques for interconnect are increasingly important for achieving timing closure of high performance designs. For the gigahertz microprocessor and multi-million gate ASIC designs it is crucial to have fast algorithms in the design automation tools for many classical problems in the field to shorten time to market of the VLSI chip. This research presents algorithmic techniques and constructive models for two such problems: (1) Fast buffer insertion for delay optimization, (2) Wire sizing for delay optimization and variation minimization on non-tree networks. For the buffer insertion problem, this dissertation proposes several innovative speedup techniques for different problem formulations and the realistic requirement. For the basic buffer insertion problem, an O(n log2 n) optimal algorithm that runs much faster than the previous classical van GinnekenÂs O(n2) algorithm is proposed, where n is the number of buffer positions. For modern design libraries that contain hundreds of buffers, this research also proposes an optimal algorithm in O(bn2) time for b buffer types, a significant improvement over the previous O(b2n2) algorithm by Lillis, Cheng and Lin. For nets with small numbers of sinks and large numbers of buffer positions, a simple O(mn) optimal algorithm is proposed, where m is the number of sinks. For the buffer insertion with minimum cost problem, the problem is first proved to be NP-complete. Then several optimal and approximation techniques are proposed to further speed up the buffer insertion algorithm with resource control for big industrial designs. For the wire sizing problem, we propose a systematic method to size the wires of general non-tree RC networks. The new method can be used for delay optimization and variation reduction

    Energy-Efficient Boarder Node Medium Access Control Protocol for Wireless Sensor Networks

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    This paper introduces the design, implementation, and performance analysis of the scalable and mobility-aware hybrid protocol named boarder node medium access control (BN-MAC) for wireless sensor networks (WSNs), which leverages the characteristics of scheduled and contention-based MAC protocols. Like contention-based MAC protocols, BN-MAC achieves high channel utilization, network adaptability under heavy traffic and mobility, and low latency and overhead. Like schedule-based MAC protocols, BN-MAC reduces idle listening time, emissions, and collision handling at low cost at one-hop neighbor nodes and achieves high channel utilization under heavy network loads. BN-MAC is particularly designed for region-wise WSNs. Each region is controlled by a boarder node (BN), which is of paramount importance. The BN coordinates with the remaining nodes within and beyond the region. Unlike other hybrid MAC protocols, BN-MAC incorporates three promising models that further reduce the energy consumption, idle listening time, overhearing, and congestion to improve the throughput and reduce the latency. One of the models used with BN-MAC is automatic active and sleep (AAS), which reduces the ideal listening time. When nodes finish their monitoring process, AAS lets them automatically go into the sleep state to avoid the idle listening state. Another model used in BN-MAC is the intelligent decision-making (IDM) model, which helps the nodes sense the nature of the environment. Based on the nature of the environment, the nodes decide whether to use the active or passive mode. This decision power of the nodes further reduces energy consumption because the nodes turn off the radio of the transceiver in the passive mode. The third model is the least-distance smart neighboring search (LDSNS), which determines the shortest efficient path to the one-hop neighbor and also provides cross-layering support to handle the mobility of the nodes. The BN-MAC also incorporates a semi-synchronous feature with a low duty cycle, which is advantageous for reducing the latency and energy consumption for several WSN application areas to improve the throughput. BN-MAC uses a unique window slot size to enhance the contention resolution issue for improved throughput. BN-MAC also prefers to communicate within a one-hop destination using Anycast, which maintains load balancing to maintain network reliability. BN-MAC is introduced with the goal of supporting four major application areas: monitoring and behavioral areas, controlling natural disasters, human-centric applications, and tracking mobility and static home automation devices from remote places. These application areas require a congestion-free mobility-supported MAC protocol to guarantee reliable data delivery. BN-MAC was evaluated using network simulator-2 (ns2) and compared with other hybrid MAC protocols, such as Zebra medium access control (Z-MAC), advertisement-based MAC (A-MAC), Speck-MAC, adaptive duty cycle SMAC (ADC-SMAC), and low-power real-time medium access control (LPR-MAC). The simulation results indicate that BN-MAC is a robust and energy-efficient protocol that outperforms other hybrid MAC protocols in the context of quality of service (QoS) parameters, such as energy consumption, latency, throughput, channel access time, successful delivery rate, coverage efficiency, and average duty cycle.https://doi.org/10.3390/s14030507

    Strategies for dynamic appointment making by container terminals

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    We consider a container terminal that has to make appointments with barges dynamically, in real-time, and partly automatic. The challenge for the terminal is to make appointments with only limited knowledge about future arriving barges, and in the view of uncertainty and disturbances, such as uncertain arrival and handling times, as well as cancellations and no-shows. We illustrate this problem using an innovative implementation project which is currently running in the Port of Rotterdam. This project aims to align barge rotations and terminal quay schedules by means of a multi-agent system. In this\ud paper, we take the perspective of a single terminal that will participate in this planning system, and focus on the decision making capabilities of its intelligent agent. We focus on the question how the terminal operator can optimize, on an operational level, the utilization of its quay resources, while making reliable appointments with barges, i.e., with a guaranteed departure time. We explore two approaches: (i) an analytical approach based on the value of having certain intervals within the schedule and (ii) an approach based on sources of exibility that are naturally available to the terminal. We use simulation to get insight in the benefits of these approaches. We conclude that a major increase in utilization degree could be achieved only by deploying the sources of exibility, without harming the waiting time of barges too much
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