Page 250 - From Smart Grid to Internet of Energy

222 From smart grid to internet of energy

FIG. 6.8 Mesh network example for the CR systems.

schemes. The CBSs and APs sense and utilize white spaces to communicate
with each other, and they have cognitive potentials in order that white spaces
can be employed to achieve communication demands of CR devices.
An example of wireless mesh network is shown in Fig. 6.8 where the net-
work contains mesh routers constituting the backbone (core) of the network.
Each mesh router can be taken into account as an AP that serves several mobile
users or mesh clients. A mesh client forwards its data traffic to its corresponding
mesh router in order to reach the gateway connected to the Internet. When the
present case of spectrum bands are considered, there may be a great number of
white spaces. Therefore, the capacity of wireless connections among the CR
devices and CBSs/APs may be enormous and the network may support more
data traffic. This network schemes may be efficiently utilized in monitoring
and data collecting applications.

6.4 Spectrum sensing (SS) techniques in CR networks

The SS process is required to determine unoccupied frequencies that can be
opportunistically utilized to serve SUs. As this process consumes power, it is
very important to use effective sensing methods. In addition, the used SS
method should be optimized for battery-powered devices [60]. The SS opera-
tion contains the process of collecting data regarding the unoccupied frequency
bands and active PUs in addition to determination of spectrum holes. Simplified
hardware and/or SS operations with reduced sensing durations are generally uti-
lized in order to provide cost-effective SS methods [49]. In a widespread