Information Technology Reference
In-Depth Information
'Change of InfoStation'
- within the InfoStation paradigm, the connection between the
InfoStations themselves and the user mobile devices is by definition geographically
intermittent. With a number of InfoStations positioned around a University campus, the
users may pass through a number of InfoStation serving areas during the service
session. This transition between InfoStation areas must be completely transparent to the
user, ensuring the user has continuous access to the service;
'Change of InfoStation and user mobile device'
- most complicated scenario whereby the
user may change the device simultaneously with the change of the InfoStation.
To support the third aspect of the context change (different communication type), the
development of an intelligent component (agent) working within the communication layer
(c.f. Figure 4) is envisaged. This component operates with the capability to define and
choose the optimal mode of communication, depending on the current prevailing access
network conditions (e.g. congestion level, number of active users, average data rate
available to each active user, etc.). The user identification and corresponding service
personalisation is subject to a middleware adaptation for use in the particular application
area. In the case of eLearning, the architecture is extended to support the three fundamental
eLearning models - the educational domain model, the user/learner model, and the
pedagogical model [Stoyanov,2005],[ Ganchev,2008c].
3.3 Layered system architecture
The layered system architecture (Figure 4) is a distributed architecture, meaning that its
functional entities are deployed across the different tiers/nodes, i.e. on mobile devices,
InfoStations, and InfoStation Centre. In this architecture the role of the InfoStations is
expanded, enabling them to act (besides the mediation role) as hosts for the local
mLearning services (LmS) and for preparation, adaptation, and conclusive delivery of
global mLearning services (GmS). This way the service provision is efficiently distributed
across the whole architecture. Each of the system network nodes have a different structure
depending on their functioning within the system. However, each node is built upon a
Communication Layer whose main task is to initialize, control and maintain
communications between different nodes. This layer is also concerned with choosing the
most appropriate mode of communication between a mobile device and an InfoStation -
whether that be Bluetooth or WiFi, or indeed as the platform evolves perhaps WiMAX in
the future. The software architecture of the InfoStations and InfoStation Centre includes a
Service Layer on the top. The main task of this layer is to prepare the execution of the
users' service requests, to activate and receive the results of the execution of different
services (local and global).
The InfoStations' middle layer is responsible for the execution of scenarios and control of
user sessions. It is at this layer where the user service requests are mainly processed by
taking into account all contex-aware aspects and applying corresponding adaptive actions.
The middle layer of the InfoStation Centre ensures the needed synchronisation during
particular scenarios (c.f. Section 8). In addition, different business supporting components,
e.g. for user accounting, charging and billing, may operate here.
The software architecture of the user mobile devices contains two other layers:
