To AND or To OR: How Shall the Fusion Center Rule in Energy-Constrained Cognitive Radio Networks?

Distributed spectrum sensing enhances the detection
reliability of a cognitive radio network. However, this
comes at the price of a higher energy consumption. To solve
this problem, a combined censoring and sleeping scheme is
considered where the cognitive radios switch off their sensing
module with a specific sleeping rate in each sensing period.
The awake cognitive radios send their local decisions to the
fusion center only if it is deemed to be informative. The fusion
center either employs the OR or the AND rule to make the
final decision about the presence or absence of the primary
user. This paper investigates which rule performs better in terms
of energy efficiency under various conditions. The underlying
sensing parameters are derived by minimizing the maximum
average energy consumption per sensor subject to a constraint on
the probabilities of false alarm and detection. This way, it can be
ensured that the spectrum opportunities are utilized efficiently
while the primary users are not interfered with. A case study
based on IEEE 802.15.4/ZigBee is considered for performance
evaluation. It is shown that significant energy savings can be
obtained by employing combined censoring and sleeping.