Variants of Romanoff's theorem

Let $\mathcal{A}=\{a_n{\}}_{n=1}^{\mathrm{\infty }}$ and $\mathcal{B}=\{b_n{\}}_{n=1}^{\mathrm{\infty }}$ be two sequences of positive integers (not necessarily distinct). Under some restrictions on $\mathcal{A}$ and $\mathcal{B}$, we obtain a lower bound for a number of integers $n$ not exceeding $x$ that can be represented as a sum $n=a_i+b_j$.