Future networks, especially in the framework of smart cities will be populated with various kinds of equipment accessing wireless communication channels. A much higher device variety will increase spectrum scarcity. Cognitive radio networks will be a key enabling technology in order to cope with the availability of the allocated radio spectrum bands. Cognitive Radio (CR) technology significantly utilizes current static spectrum bands assignment in an opportunistic manner. In this paper, we propose two spectrum opportunity (or spectrum hole) selection schemes; Minimum Collision Technique (MCT) and Maximum Residual Lifetime Technique (MRLT). The proposed techniques are evaluated by average channel utilization, average channel collision and successful secondary transmission bytes over licensed channels in a specific period of time (100s). The numerical results confirm that the MRLT scheme provides higher channel utilization and transmission bytes as well as decreases channel collision compared with the MCT scheme.