35,492 research outputs found
Wireless communication, identification and sensing technologies enabling integrated logistics: a study in the harbor environment
In the last decade, integrated logistics has become an important challenge in
the development of wireless communication, identification and sensing
technology, due to the growing complexity of logistics processes and the
increasing demand for adapting systems to new requirements. The advancement of
wireless technology provides a wide range of options for the maritime container
terminals. Electronic devices employed in container terminals reduce the manual
effort, facilitating timely information flow and enhancing control and quality
of service and decision made. In this paper, we examine the technology that can
be used to support integration in harbor's logistics. In the literature, most
systems have been developed to address specific needs of particular harbors,
but a systematic study is missing. The purpose is to provide an overview to the
reader about which technology of integrated logistics can be implemented and
what remains to be addressed in the future
A mosaic of eyes
Autonomous navigation is a traditional research topic in intelligent robotics and vehicles, which requires a robot to perceive its environment through onboard sensors such as cameras or laser scanners, to enable it to drive to its goal. Most research to date has focused on the development of a large and smart brain to gain autonomous capability for robots. There are three fundamental questions to be answered by an autonomous mobile robot: 1) Where am I going? 2) Where am I? and 3) How do I get there? To answer these basic questions, a robot requires a massive spatial memory and considerable computational resources to accomplish perception, localization, path planning, and control. It is not yet possible to deliver the centralized intelligence required for our real-life applications, such as autonomous ground vehicles and wheelchairs in care centers. In fact, most autonomous robots try to mimic how humans navigate, interpreting images taken by cameras and then taking decisions accordingly. They may encounter the following difficulties
On the Benefit of Virtualization: Strategies for Flexible Server Allocation
Virtualization technology facilitates a dynamic, demand-driven allocation and
migration of servers. This paper studies how the flexibility offered by network
virtualization can be used to improve Quality-of-Service parameters such as
latency, while taking into account allocation costs. A generic use case is
considered where both the overall demand issued for a certain service (for
example, an SAP application in the cloud, or a gaming application) as well as
the origins of the requests change over time (e.g., due to time zone effects or
due to user mobility), and we present online and optimal offline strategies to
compute the number and location of the servers implementing this service. These
algorithms also allow us to study the fundamental benefits of dynamic resource
allocation compared to static systems. Our simulation results confirm our
expectations that the gain of flexible server allocation is particularly high
in scenarios with moderate dynamics
Comparative Analysis of Location Management Schemes in Wireless ATM Networks
Mobility is the cornerstone of wireless networks. Supporting mobility
requires some form of tracking to locate mobile terminals within the network. In
the wireline ATM network, the terminal is fixed and the terminal is located by
identifying the terminal and following the routing information provided at each
switch along the path. As terminals become mobile, the path to the mobile becomes
dynamic; the terminal and the path are no longer synonymous. Signalling traffic
incurred in tracking mobile users and delivering enhanced services causes an
additional load in the Wireless ATM (WArM) network. Efficient database and
location management schemes are needed to meet the challenges from high density
and mobility of users, and various service scenarios.
In this thesis the three "natural" Location Management Strategies, i.e.,
Timer-Based, Location Area Based and Movement Based are studied and analysed
for a W ATM network. The model used for depicting user motion and call arrival is
Brownian motion with drift process and Poisson arrival process, respectively. The Timer-Based location management strategy is one in which the user
updates its location periodically after an "optimum" interval of time. This optimum
interval of time is based upon the user's mobility and call arrival characteristics and
is therefore best suited for that particular mobile.
In the Adaptive Location Area Based strategy, the user updates its location
on each LA boundary crossing. The size of the LA changes according to the user' s
mobility characteristics. The objective is to minimise the combined average
signalling cost of both paging and registration for each individual mobile user such
that the overall system-wide signalling cost for location tracking can be minimised
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