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Vol.5 No.4 December, 2009
Research Articles
Optimal Channel Selection for Real-Time
Multimedia Uplink Transmissions in Ambulances
(271-386)
Ana Goulart,
Wei Zhan, and Robert
Arnold
Through wireless internet access, ambulances
take advantage of the widespread cellular coverage in rural and urban
areas to transfer audio, video, and vital signs to the emergency room.
In the current implementation adopted by the DREAMSTM
ambulances, a designated channel is selected randomly. It is used to
transmit high priority data, such as vital signs and audio. The
remaining channels are used for video transmission. Whenever the
communication system in the ambulance detects a certain threshold of
packet losses in the designated channel, the communication system
randomly switches the high priority data to another wireless channel.
However, the designated channel selection process does not necessarily
select the best available channel. The objective of this paper is to
optimize this process through proportional-integral-derivative (PID)
control and optimization with feedback. For each channel, an objective
function is calculated. It includes a derivative term for fast response
and an integration term for detection of small but consistent
differences between channels, in addition to the proportional term.
Using a causal real-time optimization algorithm, the maximum objective
function is continuously selected. Thus, the proposed optimal channel
selection algorithm enables the ambulance’s communication system to
intelligently shift the load to better quality channels without detailed
information about the channels. The proposed algorithm combines key
performance metrics (i.e., reliability and effective transmission rate),
which can be calibrated with different weights. Using data from
simulation and experiments in commercial cellular networks, we compare
the performance of the ambulance with and without the algorithm to show
dramatic improvements in the reliability and throughput of the
ambulance’s uplink transmissions.
Situated Interaction and
Cognition in the Wild, Wild World:
Unleashing the Power of Users as Innovators
(287-300)
Hanna Risku,
Eva Mayr ,and Michael Smuc
Taking the user into account in the design of
multimedia and mobile applications is now common and accepted. However,
aside from the verbal recognition of the importance of the role of users
and the implementation of usability and human factors, their
consequences have not systematically changed product development and
design practices. Usability research and testing play a minor role in
comparison to technical possibilities, process management and economic
considerations in the development phase. Therefore, we take a closer
look at the user and the human cognitive and interactive capabilities
according to today’s Cognitive Science approaches like Situated
Cognition. What effect would it have if we took the Situated, Embodied
Cognition view seriously? Would it really make a difference in design
and development practices? And would it make a difference to the
implementation of other cognitive approaches like the Symbol
Manipulation (Information Processing) or Connectionist (Parallel
Distributed Cognition) views that might play a background role in
guiding professional practices? This paper draws parallels between the
development of Cognitive Science and the fields of Human Computer
Interaction and Usability and puts forward the claim that a serious
consideration of current thinking and knowledge regarding the
situatedness and embodiment of human cognition fundamentally changes our
assumptions and actions regarding the role of schemes, situations,
intentions and functions, tools and environments, and the role of
cooperation in the design of mobile and multimedia applications.
Effective Video Streaming using Mesh P2P with MDC over MANETs
(301-316)
Nadian N. Qadri, Antonio Liotta, Muhammad Altaf, Martin Fleury,
and Mohammed Ghanbari
Peer-to-Peer (P2P)
streaming and Mobile Ad hoc Networks (MANETs) have turned out to be two
of the most active research areas for pervasive computing. These areas
were developed independently of each other with the result that there is
insufficient verification of whether the P2P distribution paradigm and
specifically P2P real-time video streaming would work on MANETs. In this
paper, we demonstrate that mesh-based P2P streaming together with
Multiple Description Coding (MDC) over MANETs effectively provides
real-time video streaming. MDC, a promising video coding technique, is
emerging as an alternative way to improve video quality for both P2P
over an internet and for MANET applications. This paper shows that
mesh-based P2P when combined with MDC results in improvement in
delivered video quality making it acceptable for ad hoc networks. For
that purpose, the GloMoSim simulator was modified to support mesh-based
P2P and MDC. This kind of video streaming will be useful for many ad hoc
applications such as search and rescue applications, military
applications, inter-vehicular communication, and video conferencing.
A
Hierarchical Network Design Solution for Mobile IPv6
(317-332)
Vilmos Simon,
László Bokor, and Sandor Imre
Over the past years a number of IP
micro-mobility protocols have been proposed as an extension or
complement of Mobile IP. Although the development of these protocols has
generated considerable interest in industry and academia, none of them
have been widely deployed. The main reason of this lack of real-life
usage of micro-mobility proposals is that the RFCs or drafts of these
protocols do not address the problems regarding the realization of the
micro-mobility structures in detail during the procedures of network
design. This shortage is true in case of Hierarchical Mobile IP as well
(RFC 4140), which is one of the most significant micro-mobility
solutions aiming to reduce the signaling delay and the number of
signaling messages of Mobile IP. In order to provide guidelines for
network designers we propose a new a hierarchical network design
algorithm (HIENDA) based on the structure given by a Location Area
planning algorithm, aligned with a MAP allocation algorithm in
Hierarchical Mobile IPv6 to optimize the mobility management in Mobil IP
networks. HIENDA considers the topology constraints, and takes the
available mobility pattern and Access Router handover rate information
as input, and finds a near optimal hierarchical structure for which the
total signaling cost will be minimal. From the simulation results the
conclusion could be drawn that HIENDA outperforms the other existing
hierarchy optimizing solutions in the term of Location Update Cost, at
the same time keeping the Packet Delivery Cost on a low level.
Analysis of Temporal
Evolution of Social Networks (333-350)
Khaled Mahdi,
Maytham Safar and Hisham Farahat
The article presents an analysis of dynamic social network where words,
nodes and edges appear and disappear through time. We study a popular
virtual social network in the internet, known as Paltalk. We analyze the
exact and approximated cyclic entropy variation with time with the
purpose to establish the robustness of the network. In addition, we
study the effect of weighed links on the analysis of such graphs.
On Context-Sensitive
Usability Evaluation in Mobile HCI (351-370)
Karin A.
Hummel, Thomas Grill, and Andrea Hess
In
usability evaluations, experiments are often conducted in closed
laboratory situations to avoid disturbing influences. Due to
non-realistic usage assumptions, this approach has important
shortcomings when mobile Human Computer Interactions (m-HCIs) have to be
evaluated. On the other hand, field studies allow to perform experiments
close to real-world conditions, but potentially introduce influences
caused by the environment, which have not been fully investigated so
far. With this work, we contribute to distinguishing application
shortcomings from environmental disturbances which both potentially
cause decreased user performance. Our approach is based on monitoring
environmental conditions during the usability experiment, such as light,
acceleration, sound, temperature, and humidity, and relating them to
user actions. Therefore, a mobile context-framework has been developed
based on a Wireless Sensor Network (WSN) carried together with a mobile
PC. We present results of a small study (seven persons) in the lab which
pointed at increased delays and error rates of user interactions under
induced environmental disturbances. Hereby, we demonstrate the potential
of environmental monitoring for understanding user performance.
Additionally, we present novel results of a usability study carried out
in the field where we tested 19 persons under varying environmental
conditions. The results showed that error rate and delay are influenced
by environmental parameters, but in a more complex way than expected
a-priori.
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