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Cognitive radio based smart grid communications Chapter 6 221
FIG. 6.7 Ad hoc (distributed) network example for the CR systems.
scheme of distributed network architecture is depicted in Fig. 6.7. This network
architecture is essentially developed for supporting special-purpose applica-
tions. In addition, the spectrum access decisions that are created depending
on the local information may not be optimum in this type of network architec-
ture. The CR devices can expand their network information by sharing locally
gathered data among themselves, and the devices realize their transactions
depending on these sensed global information. The communication among
the CR devices can be also organized by employing various network protocols
and standards (i.e., Bluetooth, GSM, Wi-Fi, etc.). Different distributed network
architectures may be available and each of them requires specific protocols for
the CR devices. The SUs can continue their communication by using cooper-
ative communication methods over both licensed and unlicensed frequencies
thanks to only one transceiver. It is worth noting that a CR node belongs whole
CR capabilities and has to decide its subsequent actions considering observed
local information in this network architecture.
6.3.3 Mesh architecture
A combination of infrastructure-based and distributed architectures constitutes
the mesh network architecture. A typical mesh network is illustrated in Fig. 6.8.
This architecture authorizes users for both transmitting and receiving data
between CR devices, APs and CBSs.
Each CR device not only behaves as a transmitter but also behaves as a
router to control transmission of data packets. Thus, the CR devices may reach
CBSs and/or APs directly or by employing cooperative communication
methods in multi-hop manner. In addition, CBSs and APs generally operate
as gateways to link the wired and wireless backbone networks together. Hence,
this scheme is more secure and cost-effective than that of the other network