Hello all,

I was trying to use the Viterbi decoder in gr-trellis for maximum

likelihood sequence detection of a bit-stuffed data source. Here the

FSM is the bit-stuffing operation. A reference for this is

Meehan, T.; Hicks, J.; Kragh, F., “Maximum Likelihood Sequence

Detection of a Bit-stuffed Data Source,” Communications, 2006. ICC

'06. IEEE International Conference on , vol.4, no.pp.1514-1519, June

2006

For this application the number of branches entering a state is not

the same as the number leaving at a state. The documentation for

gr-trellis states

“In the following we assume that for any state, the number of incoming

transitions is the same as the number of outgoing transitions, ie,

equal to I. All applications of interest have FSMs satisfying this

requirement.”

Before I started digging in to modifying the code (or porting my

existing decoder to the gnuradio framework) I wanted to see if anyone

else was working to support different number of input branches to

output branches.

I think at a minimum the method “fsm::generate_PS_PI()” should check

to verify that the FSM description does in fact have the same number

of incoming branches and outing branches at each state.

If there is interest in making gr-trellis support this type of FSM I

can work on it, else I will probably just port my existing work over.

Please let me know what you think.

Tim