Cognitive Radio promotes the concept of using unused spectrum to increase available bandwidth. The basic techniques for finding and managing a portion of spectrum are listed below:
Step 1: Find a frequency. Using Adaptive Frequency techniques, a series of frequencies are scanned.
Step 2: Find an unused time slot in between a periodic user. Typically an Adaptive TDMA technique is used to check the availability of the frequency by monitoring it through several cycles. Only measuring the energy in the channel doesn’t give an accurate reading as noise can appear to be a signal.
Step 3: Use spatial techniques to monitor the spectrum -= The two main techniques are - beam steering
and null steering
which changes the main lobe of the radiation pattern to focus in a specific area.
Step 4: Use Adaptive bit loading based on Signal to Noise Ratio to insert a signal into the unused spectrum. OFDM techniques can be used that fit the time-frequency/hole.
Step5: Perform interference suppression and multiuser decomposition.
Adaptive Power Control and Ad-Hoc Networks are important for managing the above steps.