Performance of a relay assisted FSO-UVC HetNet with imperfect channel estimation

Ultraviolet communication (UVC) has significant potential in complex electromagnetic environments due to its non-line-of-sight (NLOS) capability, interception resistance, and low background noise sensitivity. However, its practical deployment is limited by severe path loss. To overcome this limitation, this paper proposes a novel relay-assisted free-space optical (FSO)-UVC heterogeneous network (HetNet), combining the coverage advantage of FSO with the security features of UVC. For the proposed system, a closed-form expression for the probability density function (PDF) of the end-to-end signal-to-noise ratio (SNR) is derived. Based on this result, analytical expressions for outage probability (OP), effective diversity order (EDO), and average bit error rate (ABER) are obtained under channel estimation errors (CEE). The analytical results are validated through Monte Carlo simulations. Numerical results show that system performance degrades significantly as CEE increases, and UVC links have a more pronounced impact on overall performance than FSO links. These findings provide useful insights for the design of robust hybrid optical wireless communication systems.