I'm trying to calculate the probability that a random transmission error goes undetected.
The packet in question is being transmitted over a serial RS-232C interface using 8 data bits, even parity and 1 stop bit. The packet is transfered in ASCII and structured according to the following:
- Frame header (1 character - ASCII STX)
- Telegram ID (3 characters, limited set of valid ID's)
- Data (0 to 64 characters depending on the Telegram ID)
- Checksum (4 characters, hex representation of CCITT CRC16 of Telegram ID + data)
- End of frame (1 charcter - ASCII ETX)
I've been trying to locate some papers etc, that describe the strength of the parity check as well as the CRC16 check but so far no luck.
In my own (pragmatic) mind, I've been thinking of something along the lines of:
Ptotal = Pparity * Pcrc * Pcontent
Pparity is the probability that an error is undetected by the RS-232C parity check
Pcrc is the probability the error is undetected by the CRC16 check
Pcontent is the probability that the error changes the content but is otherwise ok (syntax and semantics)
So what I'm asking for is help to calculate the Pparity and Pcrc.
I'm not necessarily looking for the exacts mathmatical models, but some more "at least better than" models.
Any help, hints, indicators, etc. are greatly appreciated.