  In cognitive radio, the cooperative spectrum sensing (CSS) plays a key role
in determining the performance of secondary networks. However, there have not
been feasible approaches that can analytically calculate the performance of CSS
with regard to the multi-level quantization. In this paper, we not only show
the cooperative false alarm probability and cooperative detection probability
impacted by quantization, but also formulate them by two closed form
expressions. These two expressions enable the calculation of cooperative false
alarm probability and cooperative detection probability tractable efficiently,
and provide a feasible approach for optimization of sensing performance.
Additionally, to facilitate this calculation, we derive Normal approximation
for evaluating the sensing performance conveniently. Furthermore, two
optimization methods are proposed to achieve the high sensing performance under
quantization.
