For c(3,1,3), how many output bits per input bit and how many memory stages?

3 outputs, 2 memory stages (s1, s2)

Why are two tail zeros appended?

To flush the registers back to state 00

Short answer

g1=111, g2=101, g3=011. Input 111011 gives output 110 011 100 010 001 011. Including tail zeros: 110 011 100 010 001 011 010 111.

Generate a convolution code for an input bit stream of (111011) using a c(3,1,3) architecture.

A c(3,1,3) convolutional encoder takes 1 input bit and gives 3 output bits (rate 1/3) with constraint length K = 3 (two memory stages s1, s2).

 b --+-->[s1]-->[s2]       out1 = b+s1+s2
     |    |       |        out2 = b+s2
     +----+-------+        out3 = s1+s2   (modulo-2 sums)

t	b	s1 s2	out1	out2	out3	Output
1	1	00	1	1	0	110
2	1	10	0	1	1	011
3	1	11	1	0	0	100
4	0	11	0	1	0	010
5	1	01	0	0	1	001
6	1	10	0	1	1	011
7 tail	0	11	0	1	0	010
8 tail	0	01	1	1	1	111

Row 3 example: b=1, s1=1, s2=1 → out1 = 1⊕1⊕1 = 1, out2 = 1⊕1 = 0, out3 = 1⊕1 = 0.

Coded output (message part): 110 011 100 010 001 011 With the two tail zeros that flush the registers: 110 011 100 010 001 011 010 111.

The state after the 6 message bits is 11 (the last two bits), and the tail returns it to 00.

✓ Answer checked by Claude Sonnet 5.5