how can I boost my apple watch signal to my I-phone without cellular or wifi

I forgot to mention, I understand that the Apple watch SE communicates with the I-phone via bluetooth. The home doesn't have internet or wifi. We only have cellular on the phone and not the Watch. Trying to see if there is a bluetooth wireless booster or maybe we can use a wireless router without an internet connection so the watch can communicate with the I-phone when it is more than 50 to 60 feet away.

I have a Cisco Linksys E2500 wireless router that we no longer use. I powering it up, I put my two iPhones on air plane mode, connected them to wifi on the newly connected Linksys that has no internet connection and tried to communicate iPhone to iPhone via text message through the wifi mode and it didn't work :(.