Cognitive Multiple Access Using Soft Sensing and Secondary Channel State Information
The authors consider a random access primary network. At the beginning of each time slot, a number of secondary users sense the channel and make an access decision based on the spectrum sensing outcome and the Channel State Information (CSI). Specifically, the channel is accessed by a secondary transmitter with a probability that depends on both the sensing metric and the gain or Signal-to-Noise-Ratio (SNR) of the channel between the transmitter and its respective receiver. Spectrum sensing operates in a "Soft" mode where the sensing metric is used directly rather than making a binary decision concerning primary activity. They consider backlogged secondary users and primary users with infinite queues.