Numerous IoT devices in wireless network interact and cooperate with each other to achieve diverse intelligent services. Such devices use static channel for wireless transmission, making the whole network vulnerable to eavesdroppers. This raises a need for means to allow secure data transmission/reception between IoT routing nodes. The concept of antenna diversity is used to enhance secrecy capacity by expanding the channel bandwidth trying to confuse attackers. Therefore, an efficient solution is considered by using multiband signal transmitter circuit to enable frequency-manipulation between connected devices. In this paper, we conducted security evaluation based on optimal relay selection protocols to maximize the channel secrecy capacity and improve data transmission. This approach uses channel sensing metric to manipulate the transmission characteristics between legitimate users via changing the operating frequency and bandwidth. Results showed a massive improvement in physical layer security against eavesdropping attack when using reconfigurable frequency bands.