15 research outputs found
Rapid Prototyping for Evaluating Vehicular Communications
[Abstract] This Thesis details the different elements of a rapid prototyping system able to
implement and evaluate vehicular communications fast, according to the continuously
evolving requirements of the industry. The system is basically composed of a testbed
and a channel emulator, which allow evaluating communication transceivers in realistic
vehicular scenarios.
Two different testbeds are introduced: a generic 2x2 system and a vehicular platform.
The former is used to compare and study space-time block coding (STBC) transmissions
at 2.4 GHz over different indoor channels. The latter makes use of software
transceivers whose performance is evaluated when they work under artificial high-speed
Rayleigh-fading scenarios.
To show the capabilities of both platforms, three software transceivers have been
developed following the specifications for the physical layers of the standards IEEE
802.11p, IEEE 802.11a and IEEE 802.16e (Mobile WiMAX). The present work details
the different elements that make up each transceiver and indicates how to connect them
to the rest of the system to perform evaluation measurements.
Finally, single-antenna and multi-antenna performances are measured thanks to the
design and implementation of three FPGA-based channel emulators that are able to
recreate up to seven different vehicular scenarios that include urban canyons, suburban
areas and highways[Resumo] A presente Tese detalla os elementos necesarios para constituir un sistema basado en
prototipado r谩pido capaz de levar a cabo e avaliar comunicaci贸ns vehiculares. O hardware
do sistema est谩 composto b谩sicamente por unha plataforma de probas (testbed)
e un emulador de canal, os cales permiten avaliar o rendemento de transceptores
inartiamicos recreando diferentes escenarios vehiculares.
Inicialmente, este traballo c茅ntrase na descripci贸n do hardware do sistema, detallando
a construcci贸n e proba dunha plataforma multi-antena e un testebed vehicular.
Estos sistemas permitiron, respectivamente, estudar o comportamento de c贸digos STBC
(space-time block codes) en interiores e medir o rendemento de tranceptores software
ao traballar a distintas velocidades vehiculares en canais con desvaecemento Rayleigh.
Tres transceptores software foron creados seguindo as especificaci贸ns das capas
f铆sicas dos est谩ndares IEEE 802.11p, IEEE 802.11a e IEEE 802.16e (Mobile WiMAX).
Este traballo detalla os diferentes componentes de cada transceptor, indicando c贸mo
conectalos ao resto do sistema para realizar a avaliacition do seu rendemento. Dita
avaliaci贸n realizouse coa axuda de tres emuladores de canal basados en tecnolox铆a
FPGA (Field Programmable Gate Array), os cales son capaces de recrear ata sete
escenarios vehiculares distintos, incluindo ca帽贸ns urbanos, zonas suburbanas e autopistas.[Resumen] La presente Tesis detalla los elementos necesarios para constituir un sistema basado
en prototipado rtiapido capaz de llevar a cabo y evaluar comunicaciones vehiculares.
El hardware del sistema est谩 compuesto por una plataforma de pruebas (testbed) y
un emulador de canal, los cuales permiten evaluar el rendimiento de transceptores
inaltiambricos recreando diferentes escenarios vehiculares.
Inicialmente, este trabajo se centra en la descripcition del hardware del sistema,
detallando la construccition y prueba de una plataforma multi-antena y un testebed
vehicular. Estos sistemas han permitido, respectivamente, estudiar el comportamiento
de ctiodigos STBC (space-time block codes) en interiores y medir el rendimiento en
canal con desvanecimiento Rayleigh de tranceptores software a distintas velocidades
vehiculares.
Tres transceptores software han sido creados siguiendo las especificaciones de las
capas f铆sicas de los estandares IEEE 802.11p, IEEE 802.11a e IEEE 802.16e (Mobile
WiMAX). Este trabajo detalla los diferentes componentes de cada transceptor,
indicando ctiomo conectarlos al resto del sistema para realizar la evaluacition de su
rendimiento. Dicha evaluacition se realiztio con la ayuda de tres emuladores de canal
basados en FPGAs (Field Programmable Gate Array), los cuales son capaces de recrear
comunicaciones multi-antena en hasta siete escenarios vehiculares distintos, incluyendo
ca帽ones urbanos, zonas suburbanas y autopistas
Enabling Accurate Cross-Layer PHY/MAC/NET Simulation Studies of Vehicular Communication Networks
Vehicle-to-vehicle and vehicle-to-roadside communications is required for numerous applications that aim at improving traffic safety and efficiency. In this setting, however, gauging system performance through field trials can be very expensive especially when the number of studied vehicles is high. Therefore, many existing studies have been conducted using either network or physical layer simulators; both approaches are problematic. Network simulators typically abstract physical layer details (coding, modulation, radio channels, receiver algorithms, etc.) while physical layer ones do not consider overall network characteristics (topology, network traffic types, and so on). In particular, network simulators view a transmitted frame as an indivisible unit, which leads to several limitations. First, the impact of the vehicular radio channel is typically not reflected in its appropriate context. Further, interference due to frame collisions is not modeled accurately ( if at all) and, finally, the benefits of advanced signal processing techniques, such as interference cancellation, are difficult to assess. To overcome these shortcomings we have integrated a detailed physical layer simulator into the popular NS-3 network simulator. This approach aims to bridge the gap between the physical and network layer perspectives, allow for more accurate channel and physical layer models, and enable studies on cross-layer optimization. In this paper, we exemplify our approach by integrating an IEEE 802.11a and p physical layer simulator with NS-3. Further, we validate the augmented NS-3 simulator against an actual IEEE 802.11 wireless testbed and illustrate the additional value of this integration
Evaluating aggregation protocols for vehicular networks in simulation
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 83-85).Routing for vehicular networks has so far presented special challenges such as high node mobility and velocity, and until now there have been few experiments performed using real data. This thesis uses a dataset of 538 taxicabs driving around the San Francisco Bay Area to gather measurements about connectivity to lay down a framework with which to reason about these networks. Additionally. this thesis describes a simulation framework written in Python to perform rapid evaluation of aggregation protocols as well as simulations where a fraction of the cars are assumed to be internet access points.by Subha Gollakota.M.Eng