Simultaneous Estimation of Primary and Cross-Channel Gains for Underlay Cognitive Radios
Junteng Yao, Ming Jin, Qinghua Guo, Youming Li · IEEE Access · 2018
In underlay cognitive radios, the primary-channel gain from a primary transmitter to a primary receiver (PU-Rx) and the cross-channel gain from a cognitive transmitter (SU-Tx) to the PU-Rx are crucial for the SU-Tx in controlling its transmit power when sharing spectrum with primary users (PUs). However, the non-cooperation between PUs and secondary users (SUs) makes it difficult for the SU-Tx to acquire the primary-channel and cross-channel gains, in particular when the channel reciprocity is not applicable. Most existing works focus on cross-channel gain estimation and are often based on the channel reciprocity. In this paper, we propose a scheme where the SU-Tx relays primary signals and transmits its own signals to the secondary receiverduring the phase of channel gain estimation. Then, an estimation method is developed, which enables the SU-Tx to acquire the primary-channel and cross-channel gainssimultaneously. The performance of the proposed estimator is analyzed. Numerical simulations are provided to validate the theoretical analysis and demonstrate the superior performance of the proposed method compared with state-of-the-art methods.