Abstract: One of the forms of wireless communications is cognitive radio. It contains transmitter and receiver. It automatically sense the channels to send the data. It has two users’ primary users and secondary users. Licensed spectrum are used by primary user and unlicensed spectrum are used by secondary user. Secondary user has to leave the channel when primary user becomes active. This leads to the problems on congestion, energy, channel bonding, channel switching and channel prediction. In this survey paper different methodologies are studied. Second order kalman filtering channel estimation methods, optimal pilot-Based channel estimation method, effects of unfit channel sensing and evaluation methods, machine learning techniques, based on remaining idle time channel bonding projects, sense and struck problem.

| DOI: 10.17148/IARJSET.2022.9442