In the present contribution, we propose a novel opportunistic ambient
backscatter communication (ABC) framework for radio frequency (RF)-powered
cognitive radio (CR) networks. This framework considers opportunistic spectrum
sensing integrated with ABC and harvest-then-transmit (HTT) operation
strategies. Novel analytic expressions are derived for the average throughput,
the average energy consumption and the energy efficiency in the considered set
up. These expressions are represented in closed-form and have a tractable
algebraic representation which renders them convenient to handle both
analytically and numerically. In addition, we formulate an optimization problem
to maximize the energy efficiency of the CR system operating in mixed ABC −
and HTT − modes, for a given set of constraints including primary
interference and imperfect spectrum sensing constraints. Capitalizing on this,
we determine the optimal set of parameters which in turn comprise the optimal
detection threshold, the optimal degree of trade-off between the CR system
operating in the ABC − and HTT − modes and the optimal data transmission
time. Extensive results from respective computer simulations are also presented
for corroborating the corresponding analytic results and to demonstrate the
performance gain of the proposed model in terms of energy efficiency
