Information Technology Reference
In-Depth Information
interfaces to the components at the underlying service delivery layer. The EIMS is
composed of several subsystems that can be grouped in three main classes:
•
QoS/QoE-based service management and multimedia content adaptation;
•
Metadata management and content search; and
•
Multicast, service monitoring, content caching, and content distribution net-
works, specified as enhanced features.
The end-to-end management performed by the EIMS relies on functionality avail-
able in the delivery layer to actually provide QoS/QoE to the end user throughout
the service lifecycle. This middle layer thus comprises all functionalities required
for a proper content delivery, with end-to-end management enabling QoS. An
adapter is the implementation, in hardware or software, of some of this functional-
ity. Fig. 1 shows the main adapters but this is not intended to be exhaustive.
The business layer (bottom) specifies the concerned actors in the end-to-end
QoS/QoE service delivery chain. Each actor relies on the services of one or more
components of the delivery layer. This chapter focuses on the top layer and does
not detail further the other two layers.
2.2 Cross-Layer QoS/QoE Adaptation Concept
The ENTHRONE solution for QoS/QoE support is based on the concept of
MPEG-21-enabled cross-layer adaptation. The idea behind this concept is to per-
form coordinated actions across several levels and layers along the end-to-end
content delivery chain. The concept of MPEG-21-enabled cross-layer adaptation
can be divided in the following three steps:
1.
The
ENTHRONE Cross-Layer Model (EXLM)
: The EXLM provides means
for describing the relationship between QoS/QoE metrics at different levels -
i.e., perceived QoS (PQoS/QoE), application QoS (AppQoS), and network
QoS (NQoS) - and layers - i.e., according to the well-known ISO/OSI refer-
ence model - which may cooperate to improve the ability of applications to
ensure certain objectives, such as QoS/QoE guarantees, power savings, users
preferences, etc. This also includes the definition of optimization criteria.
2.
The
instantiation of the EXLM by utilizing MPEG-21 metadata
: Description
formats (i.e., tools) as specified within MPEG-21 Digital Item Adaptation
(DIA) [9] are used to instantiate the EXLM for a specific use case scenario,
e.g., Video-on-Demand or conversional services. In particular, the Adaptation
QoS (AQoS) description tool is used as the main component to describe the
relationship between constraints, feasible adaptation operations satisfying
these constraints, and associated utilities (qualities) [10]. The Usage
Environment Description (UED) tools are used to describe the context where
Digital Items are consumed in terms of network conditions, terminal capabili-
ties, user preferences, and conversion capabilities. Finally, the Universal
