Detection of Gaussian Signals in Unknown Time-Varying Channels
The detection of signals in noisy channels is an important problem arising in a wide variety of applications such as sonar, radar or spectrum sensing for Cognitive Radio. Although most existing detection rules assume that the channel is time-invariant, such assumption may be unrealistic in many scenarios. For example, in narrowband communications the symbol period can be comparable to the coherence time of the channel. In acoustic communications, such as those for underwater environments, transmissions are affected by large Doppler spreads. Other applications where detectors must operate at very low Signal-to-Noise Ratio (SNR) conditions, e.g. spectrum sensing for Cognitive Radio, require long observation windows within which the channel may change significantly, especially in environments affected by mobility.