17,461 research outputs found
On the Effect of Channel Impairments on VANETs Performance
The primary means of studying the performance of vehicular ad hoc networks (VANETs) are computer simulations. Nowadays, the development of analytical models and the use of hybrid simulations that combine analytical modeling with discrete-event simulation are of great interest due to the significant reduction in computational cost. In this paper, we extend previous work in the area by suggesting an analytical model that includes distance-dependent losses, shadowing and small-scale fading. Closed-form expressions for the packet reception probability and the packet forwarding distance in the absence of simultaneous transmissions are presented. Numerical simulations validate the proposed formulation. The impact of path loss and fading on network throughput is explored. Interesting results that shows the efficacy of the approach are provided. The derived formulation is a useful tool for the modeling and analysis of vehicular communication systems
Network on Chip: a New Approach of QoS Metric Modeling Based on Calculus Theory
A NoC is composed by IP cores (Intellectual Propriety) and switches connected
among themselves by communication channels. End-to-End Delay (EED)
communication is accomplished by the exchange of data among IP cores. Often,
the structure of particular messages is not adequate for the communication
purposes. This leads to the concept of packet switching. In the context of
NoCs, packets are composed by header, payload, and trailer. Packets are divided
into small pieces called Flits. It appears of importance, to meet the required
performance in NoC hardware resources. It should be specified in an earlier
step of the system design. The main attention should be given to the choice of
some network parameters such as the physical buffer size in the node. The EED
and packet loss are some of the critical QoS metrics. Some real-time and
multimedia applications bound up these parameters and require specific hardware
resources and particular management approaches in the NoC switch. A traffic
contract (SLA, Service Level Agreement) specifies the ability of a network or
protocol to give guaranteed performance, throughput or latency bounds based on
mutually agreed measures, usually by prioritizing traffic. A defined Quality of
Service (QoS) may be required for some types of network real time traffic or
multimedia applications. The main goal of this paper is, using the Network on
Chip modeling architecture, to define a QoS metric. We focus on the network
delay bound and packet losses. This approach is based on the Network Calculus
theory, a mathematical model to represent the data flows behavior between IPs
interconnected over NoC. We propose an approach of QoS-metric based on
QoS-parameter prioritization factors for multi applications-service using
calculus model
Modeling, Simulation and Analysis of Video Streaming Errors in Wireless Wideband Access Networks
Analysis of simulated models has become a veritable tool for
investigating network behavioral patterns vis-Ă -vis transmitted content. The
streaming video research domain employs modeling extensively due to availability
of relevant tools. A vast majority of which are presented on the FOSS platform.
The transmission of audio and video streaming services over different media is
becoming ever more popular. This widespread increase is accompanied by the
difficult task of maintaining the QoS of streaming video. The use of very accurate
coding techniques for transmissions over wireless networks alone cannot guarantee
a complete eradication of distortions characteristic of the video signal. A software-
hardware composite system has been developed for investigating the effect of
single bit error and bit packet errors in wideband wireless access systems on the
quality of H.264/AVC standard video streams. Numerical results of the modeling
and analysis of the effect of interference robustness on quality of video streaming
are presented and discussed. Analytic results also suggest that the Markov model
of packetization of error obtained from a real network for streaming video can be
used in the simulations of transmission of video across networks in the hardware-
software complex developed by the authors in a previous work
Characterization of the on-body path Loss at 2.45 GHz and energy efficient WBAN design for dairy cows
Wireless body area networks (WBANs) provide promising applications in the healthcare monitoring of dairy cows. The characterization of the path loss (PL) between on-body nodes constitutes an important step in the deployment of a WBAN. In this paper, the PL between nodes placed on the body of a dairy cow was determined at 2.45 GHz. Finite-difference time domain simulations with two half-wavelength dipoles placed 20 mm above a cow model were performed using a 3-D electromagnetic solver. Measurements were conducted on a live cow to validate the simulation results. Excellent agreement between measurements and simulations was achieved and the obtained PL values as a function of the transmitter-receiver separation were well fitted by a lognormal PL model with a PL exponent of 3.1 and a PL at reference distance ( 10 cm) of 44 dB. As an application, the packet error rate ( PER) and the energy efficiency of different WBAN topologies for dairy cows (i.e., single-hop, multihop, and cooperative networks) were investigated. The analysis results revealed that exploiting multihop and cooperative communication schemes decrease the PER and increase the optimal payload packet size. The analysis results revealed that exploiting multihop and cooperative communication schemes increase the optimal payload packet size and improve the energy efficiency by 30%
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