Efficient discovery and effective sharing of spectrum opportunities are the most challenging issues in a multi-channel cognitive radio network (CRN) with multiple secondary users (SUs). Distributed opportunistic spectrum access scheme based on sequential channel-sensing in decentralized CRN (cognitive radio network). Different from the traditional spectrum sensing scheme, the scheme proposed allows a secondary users to sense many channels one by one sequentially in a slot. Opportunistic Spectrum Access Based on Sequential Channel-Sensing in Decentralized CRN. Simulated annealing (SA) is a probabilistic technique for approximating the global optimum of a given function. Specifically, it is a metaheuristic for approximate global optimization in a large search space. It is often used when the search space is discrete. The SA heuristic considers some neighbouring states of the current states, and probabilistically decides between moving the system to states and staying in states. These probabilities ultimately lead the system to move to states of lower energy. This approach jointly addresses when to perform sensing, which channels to sense, in what order and how long to scan each channel.