Number Of Network Hops Research Articles

Blockchain in IoT Systems: End-to-End Delay Evaluation

Providing security and privacy for the Internet of Things (IoT) applications while ensuring a minimum level of performance requirements is an open research challenge. Recently, blockchain offers a promising solution to overcome the current peer-to-peer networks limitations. In the context of IoT, Byzantine fault tolerance (BFT)-based consensus protocols are used due to the energy efficiency advantage over other consensus protocols. The consensus process in BFT is done by electing a group of authenticated nodes. The elected nodes will be responsible for ensuring the data blocks’ integrity through defining a total order on the blocks and preventing the concurrently appended blocks from containing conflicting data. However, the blockchain consensus layer contributes the most performance overhead. Therefore, a performance study needs to be conducted especially for the IoT applications that are subject to maximum delay constraints. In this paper, we obtain a mathematical expression to calculate the end-to-end delay with different network configurations, i.e., number of network hops and replica machines. We validate the proposed analytical model with simulation. Our results show that the unique characteristics of IoT traffic have an undeniable impact on the end-to-end delay requirement.

Characterization of Substation Process Bus Network Delays

This paper presents the characterization of network delays in an IEC61850 process bus substation area network, both through theoretical analysis and simulations. Several design targets were defined considering the recommendations of standards and good design practices: number of network hops, total network delay, probability of the delay being exceeded, link load, network topology and availability. An analytical delay estimation methodology is proposed, considering both the steady-state traffic and traffic resulting from a breaker failure event. A complete substation is taken as an example for characterizing the network delays, considering a star network topology. Simulations allow to obtain the cumulative distribution functions and percentile values of network delays. Results show a good agreement between the simulation and the analytical analysis. While the delay is best characterized statistically through simulation, finding the maximum network delay through simulations can be very time consuming, making the analytical analysis more suitable.

Stochastic Optimization of Cognitive Networks

In this paper, we aim to propose a stochastic joint optimization method that allows the minimization of the energy consumption of the spectrum sensing of a multi-hop secondary network subject to constraints on the detection performance and the number of network hops, in a tradeoff between the overall probability of missed detection and false alarm, and the energy consumption. The optimal closed-form solution of the optimization problem is computed by means of two approaches: 1) worst case and 2) stochastic approach. Both theoretical analysis and numerical results show that the proposed method allows reducing the energy consumption, by showing its effectiveness with different data fusion rules. Particularly, the optimal solution outperforms the existing ones in terms of computational complexity, and of energy consumption specially for a number of hops greater than 4. The proposed technique has been finally proven in several environments that characterize different primary operative scenarios, such as wireless metropolitan area networks and satellite communications in the presence of interference with very low signal-to-noise ratio.

UNISM: Unified Scheduling and Mapping for General Networks on Chip

Task scheduling and core mapping have a significant impact on the overall performance of network on chip (NOC). In this paper, a unified task scheduling and core mapping algorithm called UNISM is proposed for different NOC architectures including regular mesh, irregular mesh and custom networks. First, a unified model combining scheduling and mapping is introduced using mixed integer linear programming (MILP). Then, a novel graph model is proposed to consider the network irregularity and estimate communication energy and latency, since the number of network hops is not accurate enough for irregular mesh and custom networks. To make the MILP-based UNISM scalable, a heuristic is employed to speed up our method. Compared with two previous state-of-the-art works, experimental results show that more than 15% and 11.5% improvement on the execution time is achieved with similar energy consumption on average for regular mesh NOC. For irregular and custom NOC, the improvement is 27.3% and 14.5% on the execution time with 24.3% and 18.5% lower energy. Moreover, our method is scalable for large benchmarks in terms of runtime.

Transatlantic Touch: A Study of Haptic Collaboration over Long Distance

The extent to which the addition of haptic communication between human users in a shared virtual environment (SVE) contributes to the shared experience of the users has not received much attention in the literature. In this paper we describe a demonstration of and an experimental study on haptic interaction between two users over a network of significant physical distance and a number of network hops. A number of techniques to mitigate instability of the haptic interactions induced by network latency are presented. An experiment to evaluate the use of haptics in a collaborative situation mediated by a networked virtual environment is examined. The experimental subjects were to cooperate in lifting a virtual box together under one of four conditions in a between-groups design. Questionnaires were used to report the ease with which they could perform the task and the subjective levels of presence and copresence experienced. This extends earlier work by the authors to consider the possibility of haptic collaboration under real network conditions with a number of improvements. Using the technology described in this paper, transatlantic touch was successfully demonstrated between the Touch Lab at Massachusetts Institute of Technology, USA and Virtual Environments and Computer Graphics (VECG) lab at University College London (UCL), UK in 2002. It was also presented at the Internet II demonstration meeting in 2002 between University of Southern California and the Massachusetts Institute of Technology.