B. Dynamic control channels
In general, control channels are deployed to organize
mobile devices and convey network control information, for
example, identification, synchronization, channel allocations
(restrictions) or network policies. In order to facilitate the
distribution of control channels for cognitive radios the European
Telecommunications Standards Institute Reconfigurable
Radio Systems Technical Committee (ETSI RRS TC) has
recommended two ways forward: 1) out-of-band, where the
control channels are distributed over a globally dedicated
physical channel, 2) in-band, where the control channels are
transported over a specific radio access technology using
a separate or an existing control channel. The former has
the disadvantage of requiring additional spectral resources
and global harmonization. The latter is a viable solution for
systems operating in licensed bands with fixed operational
frequency and high level of coordination, which use whitespaces
only temporally to extend network capacity. However,
for systems that intend to rely solely on whitespaces it poses
some difficulties, as the allocated operational frequency may
change depending on the incumbent user behaviour. Herein,
we propose a reliable solution for an in-band control channel
in whitespaces, which is dynamically deployed depending
on the whitespace availability. The centre frequency of this
control channel is allocated based on the geo-location database
information. Subordinate whitespace devices will acquire this
centre frequency through the detection of a physical layer
signature inserted in the transmitted waveform of the control
channel, as described in the following subsection. Coordination
of control channel allocations among whitespace-operating
devices is achieved through the system of intermittent channel
reservations added to the geo-location database information.