Dear researchers
It is known that the conventional energy detector are susceptible to noise uncertainty due to the assumption of the noise power. But, does the noise uncertainty has any meaning if we were able (let's say) to measure the noise power of the received signal and then compare it to the total signal power in order to make a decision?
Best,
Actually, target signal usually mixed with the noise as the receiving signal. The real noise power or the real incoming signal power is hard to measure from mixed receive signal.
People want to use historical measurent, which has no target signal, to predict the power of current noise. The hidden assumption behide it is the mean value of the noise is stable. If the noise is unstable, for instance the burst noise from ship, fish school or sonar. The current estimation of noise power based on old measurement may have some mistake.
Another way to measure the noise power from mixed receiving signal (target signal+noise) is add some test frequency in you transmitted signals, which could be used in OFDM based communications. More specifically, when design the transmission signal, the data is carried on each subcarriers. We could leave some subcarrier and let them do not carry any data. When received signals, the noise density could be estimated on the power on these empty carriers, since they do not carry data, and there power is from noise. However, this kind of approach may affected by Doppler spreading and Doppler shift.
To summary, if you could get real noise power, noise uncertainty may not bother you. however, we could not get the noise power in real time, since noise usually mixed with target signal. In this case, model the noise and estimate it with stocastic process would be a good choose.
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