Robust Radio Communication Protocol

Ok i think im phrasing my issue slightly misleading.

Its not that im having errors and need a robust protocol to handle them, but I would like the protocol to not fall apart on the off chance i do get a dropped byte or error.

My main question is how to a packet system with starting it and ending it. I want a fixed number of bytes in a two way communication, I just don't know what the standard method is for using packets in radio communication.

What i am confused about, and correct me if im wrong, but whatever defines the start of the packet cannot be used in the packet itself...

-Nick