  Wireless standards (e.g., IEEE 802.11af and 802.22) have been developed for
enabling opportunistic access in TV white space (TVWS) using cognitive radio
(CR) technology. When heterogeneous CR networks that are based on different
wireless standards operate in the same TVWS, coexistence issues can potentially
cause major problems. Enabling collaborative coexistence via direct
coordination between heterogeneous CR networks is very challenging, due to
incompatible MAC/PHY designs of coexisting networks, requirement of an
over-the-air common control channel for inter-network communications, and time
synchronization across devices from different networks. Moreover, such a
coexistence scheme would require competing networks or service providers to
exchange sensitive control information that may raise conflict of interest
issues and customer privacy concerns. In this paper, we present an architecture
for enabling collaborative coexistence of heterogeneous CR networks over TVWS,
called Symbiotic Heterogeneous coexistence ARchitecturE (SHARE). Define
"indirect coordination" first before using it. Because coexistence cannot avoid
coordination By mimicking the symbiotic relationships between heterogeneous
organisms in a stable ecosystem, SHARE establishes an indirect coordination
mechanism between heterogeneous CR networks via a mediator system, which avoids
the drawbacks of direct coordination. SHARE includes two spectrum sharing
algorithms whose designs were inspired by well-known models and theories from
theoretical ecology, viz, the interspecific competition model and the ideal
free distribution model.
