A New Frequency Hopping Scheme to Secure the Physical Layer in The Internet of Things (IoT)

In this paper, the conventional frequency hopped spread spectrum (FHSS), uncoordinated frequency hopping (UFH), and the message-driven frequency hopping (MDFH) have been simulated and analyzed for bit error rates against single and multiband disguised jamming attacks. The results confirm the superiority of the MDFH over the FHSS. The MDFH also relaxes the two communicating legitimate node's need for frequency synchronization which increases system complexity. However, those schemes are not feasible for the Internet of Things applications due to the lack of computation capability, size, and energy consumption. Because of that we designed and simulated a new frequency hopping scheme which takes into consideration the IoT node's limitations and at the same time maintains a satisfying bit error rate. The new scheme idea is to build a look-up table of orthogonal frequencies in the transmitter and the receiver. Before any transmission, the transmitter uses the UFH scheme to send a lightweight encrypted key to the receiver; the receiver then uses that key to determine the frequency sequence. After successfully receiving the key the receiver should send back acknowledgment; otherwise, the transmitter must send the key again. There are three benefits of the new scheme. First, it is hard on the jammer and/or the eavesdropper to destroy and/or percept the sequence key due to the encryption and the frequency hopping mechanisms. Second, it is robust against the disguised jamming, which considered the worst. Third, it is very simple and affordable. The three schemes have been simulated and the results show that the proposed scheme has provided a bit error rate close to the MDFH. However, the MDFH fails easily in detecting the strongest signal to predict the legitimate transmitted carrier if the jammer attacks all the filter banks on the receiver side at the same time with a disguised jamming signal. We address this problem in our proposed scheme by waiving the use of the filters.