Abstract: There is a continuous large number of crashes involving pedestrians in Nevada despite the numerous safety mechanisms currently used at roadway crossings. Hence, additional as well as more effective mechanisms are required to reduce crashes in Las Vegas, in particular, and Nevada in general. A potential mechanism to reduce conflicts between pedestrians and vehicles is a High-intensity Activated crossWalK (HAWK) signal. This study evaluates the effects of such signals at a particular site in Las Vegas. Video data were collected using two cameras, facing the eastbound and westbound traffic. One week of video data before and after the deployment of the signal were collected to capture the behavior of both pedestrians and drivers. T-test analyses of pedestrian waiting time at the curb, curb-to-curb crossing time, total crossing time, jaywalking events, and near-crash events show that the HAWK system provides significant benefits.
Abstract: Long Term Evolution (LTE) is a 4G wireless
broadband technology developed by the Third Generation
Partnership Project (3GPP) release 8, and it's represent the
competitiveness of Universal Mobile Telecommunications System
(UMTS) for the next 10 years and beyond. The concepts for LTE
systems have been introduced in 3GPP release 8, with objective of
high-data-rate, low-latency and packet-optimized radio access
technology. In this paper, performance of different TCP variants
during LTE network investigated. The performance of TCP over
LTE is affected mostly by the links of the wired network and total
bandwidth available at the serving base station. This paper describes
an NS-2 based simulation analysis of TCP-Vegas, TCP-Tahoe, TCPReno,
TCP-Newreno, TCP-SACK, and TCP-FACK, with full
modeling of all traffics of LTE system. The Evaluation of the
network performance with all TCP variants is mainly based on
throughput, average delay and lost packet. The analysis of TCP
performance over LTE ensures that all TCP's have a similar
throughput and the best performance return to TCP-Vegas than other
variants.
Abstract: A study on the performance of TCP Vegas versus
different TCP variants in homogeneous and heterogeneous wired
networks are performed via simulation experiment using network
simulator (ns-2). This performance evaluation prepared a comparison
medium for the performance evaluation of enhanced-TCP Vegas in
wired network and for wireless network. In homogeneous network,
the performance of TCP Tahoe, TCP Reno, TCP NewReno, TCP
Vegas and TCP SACK are analyzed. In heterogeneous network, the
performances of TCP Vegas against TCP variants are analyzed. TCP
Vegas outperforms other TCP variants in homogeneous wired
network. However, TCP Vegas achieves unfair throughput in
heterogeneous wired network.
Abstract: Transmission control protocol (TCP) Vegas detects
network congestion in the early stage and successfully prevents
periodic packet loss that usually occurs in TCP Reno. It has been
demonstrated that TCP Vegas outperforms TCP Reno in many
aspects. However, TCP Vegas suffers several problems that affect its
congestion avoidance mechanism. One of the most important
weaknesses in TCP Vegas is that alpha and beta depend on a good
expected throughput estimate, which as we have seen, depends on a
good minimum RTT estimate. In order to make the system more
robust alpha and beta must be made responsive to network conditions
(they are currently chosen statically). This paper proposes a modified
Vegas algorithm, which can be adjusted to present good performance
compared to other transmission control protocols (TCPs). In order to
do this, we use PSO algorithm to tune alpha and beta. The simulation
results validate the advantages of the proposed algorithm in term of
performance.
Abstract: This paper describes the performance of TCP Vegas
over the wireless IPv6 network. The performance of TCP Vegas is
evaluated using network simulator (ns-2). The simulation experiment
investigates how packet spacing affects the network delay, network
throughput and network efficiency of TCP Vegas. Moreover, we
investigate how the variable FTP packet sizes affect the network
performance. The result of the simulation experiment shows that as
the packet spacing is implements, the network delay is reduces,
network throughput and network efficiency is optimizes. As the FTP
packet sizes increase, the ratio of delay per throughput decreases.
From the result of experiment, we propose the appropriate packet size
in transmitting file transfer protocol application using TCP Vegas
with packet spacing enhancement over wireless IPv6 environment in
ns-2. Additionally, we suggest the appropriate ratio in determining
the appropriate RTT and buffer size in a network.
Abstract: This paper attempts to establish the fact that Multi
State Network Classification is essential for performance
enhancement of Transport protocols over Satellite based Networks. A
model to classify Multi State network condition taking into
consideration both congestion and channel error is evolved. In order
to arrive at such a model an analysis of the impact of congestion and
channel error on RTT values has been carried out using ns2. The
analysis results are also reported in the paper. The inference drawn
from this analysis is used to develop a novel statistical RTT based
model for multi state network classification.
An Adaptive Multi State Proactive Transport Protocol consisting
of Proactive Slow Start, State based Error Recovery, Timeout Action
and Proactive Reduction is proposed which uses the multi state
network state classification model. This paper also confirms through
detail simulation and analysis that a prior knowledge about the
overall characteristics of the network helps in enhancing the
performance of the protocol over satellite channel which is
significantly affected due to channel noise and congestion.
The necessary augmentation of ns2 simulator is done for
simulating the multi state network classification logic. This
simulation has been used in detail evaluation of the protocol under
varied levels of congestion and channel noise. The performance
enhancement of this protocol with reference to established protocols
namely TCP SACK and Vegas has been discussed. The results as
discussed in this paper clearly reveal that the proposed protocol
always outperforms its peers and show a significant improvement in
very high error conditions as envisaged in the design of the protocol.