On the Erd{\H{o}}s-Ginzburg-Ziv constant of groups of the form $C_2^r\oplus C_n

Let $G$ be a finite abelian group. The Erd{\H{o}}s-Ginzburg-Ziv constant $\mathsf s(G)$ of $G$ is defined as the smallest integer $l\in \mathbb{N}$ such that every sequence $S$ over $G$ of length $|S|\geq l$ has a zero-sum subsequence $T$ of length $|T|= {\exp}(G)$. The value of this classical invariant for groups with rank at most two is known. But the precise value of $\mathsf s(G)$ for the groups of rank larger than two is difficult to determine. In this paper we pay our attentions to the groups of the form $C_2^{r-1}\oplus C_{2n}$, where $r\geq 3$ and $n\ge 2$. We give a new upper bound of $\mathsf s(C_2^{r-1}\oplus C_{2n})$ for odd integer $n$. For $r\in [3,4]$, we obtain that $\mathsf s(C_2^2\oplus C_{2n})=4n+3$ for $n\ge 2$ and $\mathsf s(C_2^{3}\oplus C_{2n})=4n+5$ for $n\geq 36$.