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Distributed Data Collection System (DDCS) followed by Section four on setting up for evaluating DDCS.
Conclusions and future work are described in the section five of this paper.
2. Data Transmission Scheme
GPRS being an ETSI (European Telecommunications Standard Institute) standard for data transmission
uses GSM (Global System for Mobile Communications) network (Chen et al., 2002) and provides an
―always-on‖ connection, where the resources are consumed only when the data packets are actually
transmitted (Brasche, and Walke, 1997). To a globally distributed traffic company, employing this
technology as their data transmission scheme is useful as it provides all time connectivity while the only
charges incurred are when the data is transmitted or received with a minimal on-line charge (McKitterick
and Dowling, 2003). It becomes very expensive to utilise a data scheme which charges based on time
connectivity (e.g. GSM) rather than amount of data transmitted or received.
Some of the advantages identified from the literature of GPRS scheme includes; improved utilization of
radio resources, offering volume-based billing, higher data transfer rates, shorter access times, and
simplification of the access to the packet data networks (Brasche, and Walke, 1997, Bettstetter et al.,
1999). These led to the selection of GPRS data scheme for transmitting vehicle traffic data packets from
multiple remote sites to in-stations.r.
3. Software Architecture
DDCS is an integrated Software for collecting, formatting, sorting and then storing the vehicle traffic data
from multiple remote sites. It can either exist as a complete Software toolset in a single in-station
collecting data from single/multiple site(s), or a distributed Software toolset installed at various instations
(globally) collecting data from single/multiple site(s). DDCS has been designed using the Unified
Modelling Language (UML) (Booch et al., 1999) to specify the requirements capture and the architecture
of the system. It has been developed to execute on a Microsoft Windows .NET platform as a set of
business objects that communicate with each other using the Web services technology (Schall et al.,
2006).
UML is a graphical language for visualising, specifying, constructing and documenting the artefacts of a
Software-intensive system (Booch et al., 1999). In this study, it allowed to cover the conceptual things
such as business processes and system functions. Furthermore, it also provided the coverage of concrete
things, such as classes written in a specific object-oriented programming environment (.NET framework),
database schemas and reusable Software components. DDCS architecture is such that, it supports the
system being suitably distributed across a network where required for data collection. The gathered
vehicle data within the DDCS can be further broadcasted to other locations (example PDA, Mobile
Phones) via internet based technologies such as web services (Schall et al., 2006). Web services can also
be used to analyse and monitor vehicle data collected by DDCS from globally distributed multiple servers
(Casati et al., 2003).
DDCS is constructed from a container Multi Document Interface (MDI) shell environment using the
.NET Asynchronous Socket technology for effective handling of multiple connections from multiple sites
all at once, all within one process / thread. As shown in fig1, DDCS scales very well as it allows
thousands of concurrent connections i.e. only thousands of nonblocking socket objects (Welsh et al.,
2001) are used, and not thousands of threads / processes. When a new site makes a GPRS connection to
an in-station, the DDCS Server (within that in-station) raises a socket event (i.e. worker socket) from the
thread pool. The responsibility is transferred to the worker socket which in turn has to make sure that the
data gets collected, formatted, sorted and then stored in a particular user-described location. Once all or
some of the vehicle data from a site (for example Site 1) is collected, an appropriate location is
automatically selected by DDCS to store all the data from the Site 1. Under no circumstances, is the data
Proceedings of IEDC 2010, 1-3 July, 2010
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