# What is the unit of a complex AWGN variance? mW or W?

In this paper https://arxiv.org/pdf/1805.08898.pdf ,there is a variance be written as $$\sigma^2_{h,k}=\theta d_k^{- \alpha}$$, $$\sigma^2_{h,k}$$ is the variance of th channel,$$d_k$$ is the distance between the receiver and the transmitter,$$\alpha$$ is the path loss exponent. i have already calculated the $$\sigma^2_{h,k}=\theta d_k^{- \alpha}=0.0018$$,but i am not sure about its unit

I want to ask what is the unit of $$\sigma^2_{h,k}$$? W or mW?