Page 237 - From Smart Grid to Internet of Energy

210 From smart grid to internet of energy

based on increasing demand for wireless Internet access over mobile devices
such as notebooks, tablets, e-book readers and smartphones, and this demand
will constantly grow in the future. It is clear that wireless communication appli-
cations not only are being used for personal communication services but also are
being utilized in metering, monitoring and control systems such as advanced
metering infrastructure (AMI), health-monitoring systems, surveillance sys-
tems, traffic controlling systems and so forth. Nonetheless, the spreading of
wireless systems is directly related to allocated spectrum that regulatory agen-
cies have generally organized available spectrum by considering kinds of appli-
cations and services. Especially, the majority of available spectrum has been
authorized to service providers in order to make long-term use possible in a
large geographical area [4, 5]. This allocation task is performed by the regula-
tory authority of each country (i.e., Federal Communications Commission
(FCC) in the United States, Information and Communication Technologies
Authority in the Turkey). Regardless of the situation of data traffic, only allo-
cated spectrum should be exploited by communication systems. On the other
hand, the short-term licensing possibility of spectrum that provides an oppor-
tunity to satisfy transient traffic demand is restricted due to the allocation of
the radio spectrum permanently. Furthermore, a dedicated spectrum may not
be effectively used if there exist very few active users. The Spectrum Task
Force (SPTF) of the FCC [5] has reported that most of the licensed spectrum
bands are either partially or extremely unused at a certain time and in a partic-
ular area. It is also specified in [6] that the use of licensed spectrum may change
from 15% to 85% depending on the time and place.
With respect to the present spectrum allocation procedures, new spectrum
allocation for every wireless services should be performed by considering
unemployed frequencies of the spectrum. A large part of the spectrum below
3 GHz is being assigned for special utilization because of these procedures
[7]. In addition, several reports have clearly indicated that there is an unequal
spectrum utilization [8–10] where both cellular bands and unlicensed bands are
very crowded while the other parts of the spectrum is unemployed. Especially,
when the unlicensed Industrial, Scientific and Medical (ISM) bands are consid-
ered, it is evident that there is an important bandwidth problem for license-free
wireless systems. Therefore, bandwidth wastage, underutilization, and spec-
trum allocation are considered as the main challenges of wireless systems. Since
the allocation scarcity problem is mainly based on the ineffective usage of spec-
trum, this issue can be solved through new approaches, regulations and technol-
ogies [11]. These challenges have encouraged researchers to develop new
methods and systems for wireless communications that are able to present more
reliable, efficient and effective communication platforms.
Cognitive radio (CR) technology intends to overcome these mentioned
problems by employing limited spectrum more efficient without interfering
to other users. CR is an emerging wireless communication technology where
a radio is able to sense and analyze the spectrum, and it can reconfigure its