Proactive channel gain estimation for coexistence between cognitive and primary users

In cognitive radio systems, the channel gains between primary users (PUs) and cognitive users (CUs) and that between PUs are critical for the coexistence of CUs and PUs. In this paper, we propose a proactive channel gain estimation approach by using the received primary signal for probing, which obtains both kinds of channel gains without information exchange between CUs and PUs. In average, the probing in our proactive approach does not introduce interference to PUs while conventional ones usually do. Simulation results show that the relative estimation errors of the proposed approach are below 0.02 with a proper CU location, where the channels suffer path loss and shadowing, and their gains range from about -120 dB to about -50 dB.