Let $x$ be a large positive real number and let $q\leq 2$ be a positive integer. It is known that for a positive integer $n,$ there exists a unique sequence $\left\{0\leq n_k\leq q-1\right\}_{k\geq 0}$ such that $$n=\sum_{k\geq 0} n_k q^k.$$ Define the sum of digits of $n$ in basis $q$ by $$S_q(n):=\sum_{k\geq 0} n_k.$$ Is there an asymptotic formula for the following sum $$\sum_{a+b\leq x} \sigma_q(a,b),$$ where $\sigma_q(a,b)$ is the number of carry operations needed when adding $a$ and $b$ in basis $q.$
Many thanks.