Nowadays, the use of Wireless Sensor Networks (WSN) is gaining popularity especially in dense urban scenarios with a wide range of applications which share the same ISM band of the spectrum frequency, this situation leads to severe congestion problems. Therefore, it is important to define mechanisms that allow the use of their resources in an efficient way maintaining system quality even under harsh interferences. Under these considerations, in this paper a channel assignment management mechanism based on a centralized simulated annealing algorithm, is proposed; this mechanism is a probabilistic technique that optimizes a utility function and selects new communication channels alleviating the channel congestion problem. Furthermore, this study analyses the required WSN channel capacity that maximizes the scenario performance during the assignments of new operating channels to the whole network.