Secure Backhauling Over Adaptive Parallel MmWave/FSO Link

FSO and MmWave are regarded as complimentary technologies for 5G backhaul links in order to avoid communication interruption in low visibility conditions. This paper secures the communication over two parallel FSO and MmWave links by optimizing the power and rate allocated to each link. The transmitter aims to maximize its transmission rate over the two links while satisfying a constraint on the security of the communication, represented by the secrecy outage probability, and a constraint on its power budget. Results show that transmission over the MmWave link increases when the secrecy requirement is not strict or when the eavesdropper moves farther from the transmitter, or when the fog becomes thick. Results also show that power and rate optimization improves the rates compared to the cases when the transmitter uses the FSO link only or the MmWave link only.