Digital Signal Processing Reference
In-Depth Information
1.5 The Need for a New Approach
This topic proposes a framework that is able to exploit the flexibility offered by
the disruptive radio hardware and spectrum access paradigms. The main problem
considered is the sharing of wireless spectrum. To intelligently share this spectrum,
terminals need to interact with their actual environment to learn its behavior and
adapt accordingly. As mentioned in Sect.
1.4
, a CR system heavily relies on the
existence of a feedback channel from the environment. Hence, the proposed frame-
work is fully compatible with the CR paradigm. In the Mitola vision it is theo-
retically proposed to learn everything in real time. For practical applications, we
introduce a framework that is able to extract useful information upfront, when de-
signing the system. Consequently, the performance in operation can be improved
greatly. In [18, 19] it is demonstrated that a hybrid Design Time (DT)-Run Time
(RT) framework allows for very efficient operations. In such DT-RT framework,
procedures are developed at DT. At RT, these procedures can be efficiently executed
by monitoring the environment and selecting the appropriate procedure. However,
due to the increasing flexibility of wireless terminals, it is becoming harder to predict
all possible situations. Furthermore, due to the increasing environment dynamics, it
is also becoming harder to model these situations. Our framework should hence be
flexible enough to allow calibration and learning.
We propose an extended DT-RT framework and maintain its efficient operation.
In line with the CR paradigm, the framework is made flexible enough so the terminal
can change its behavior based on interaction with the environment. Feedback-based
learning is enabled in the framework, fully in line with the CR definitions introduced
earlier.
1.6 Radios to Go Smarter and Cognitive
In this topic, we aim to introduce how Software Defined Radios can be conceived
to become smart(er) and cognitive. Indeed the opportunities brought about by the
improved flexibility and degrees of freedom, bring along an increased control com-
plexity. Exploiting this complexity is a challenge, which holds the opportunity to
use scarce resources spectrum and energy in an optimal way. The optimization itself
should work in practical cases and come at minimal overhead.We thereto sketch the
standardization scene, introduce methodological concepts, and discuss the applica-
tion to relevant case studies:
•
Chapter 2
discusses some of the major wireless standards to illustrate how in-
creased flexibility and control is becoming abundant, even within a single wireless
technology. Next to flexibility within standards, focus is on coexistence between
standards and finally cooperation across standards. The latter often requires a
flexibility across standards and increased intelligence. This drives the need for
SDR and finally CR.
