Wirless out of range problem?

Hi all! Current Cable router MR814v2, but it’s out of range at where I wanted to use. Should I deploy another cable router or just a wirless switch? If wirless switch, can I use it wirlessly connect to the current Router or have to connect via RJ45? And the security, is there any securities in the switch that I can set to prevent someone tap into my network? Thanks for you advices!!!