Looking from here it seems you're still using an older DOCSIS 2.0 modem that isn't compatible with the speeds you're subscribed to. I'd suggest looking into upgrading to a newer DOCSIS 3.0 modem will will also give you a free speed increase.
I am in 70506 zip code. I experience dropped internet or extremely slow internet EVERY evening. I had a field tech come to my house who changed a coax junction and checked the signal strength, which he said was okay. He suggested that it must be my modem/ gateway, which was on the Cox approved list and less than a year old. Against my better judgement, I purchased a new modem and separate router, resgistered it with Cox, and I am STILL getting drops and slowdowns. My most recent was logging in to this page. I live on a dead end road. I suspect that Cox is either jimmying with the bandwidth or the lines can't handle the traffic. I'm out several bucks for a failed diagnosis. I'd really like an explanation as to what is going on because it is a regular and predictable occurrence.
I'm in zip code 93013 and mine drops every few minutes too. Its hard to get anything done. I bought the Netflix 6300 router from Cox. It happens on my laptop and on my cell phone. I unplug the router and plug it back in to get it back online if its off for a few minutes.
I am not tech savvy at all, so please go easy on me.