In this letter, we consider a secondary network (SN) in which an ambient
backscatter device (BD) utilizes the secondary transmitter (ST) signal
to communicate its own information to the secondary destination (SD).
Optimizing performance of such networks is complicated by signal
reflections by the BD.Â It is shown in this work how the secondary
transmit power and the reflection coefficient of the BD can both be
jointly optimized using a simple restricted one dimensional search to
satisfy the quality of service (QoS) constraints of SN as well as the
primary network (PN) while maximizing performance of the backscatter
link, which is termed the tertiary network (TN).Â Only statistical
channel knowledge is used for this purpose. It is seen that careful
optimization can improve spectral efficiency. Simulations validate the
derived analytical expressions.