written 8.5 years ago by | • modified 8.4 years ago |
$e.g \ sequence = { a_1 \ a_1 \ a_2 \ a_1 \ a_3 }$
iv. Solution:
Step 1: Initialization (n=0)
Char X | Probability P (x) | CDF F(x) |
---|---|---|
$a_1$ | 0.6 | 0.6 |
$a_2$ | 0.2 | 0.8 |
$a_3$ | 0.2 | 1 |
$L (0) =0$
$U (0) = 1$
Step 2: $1^{st}$ Symbol in sequence = $a_1$ = X (n=1)
$L (1) = L (0) + [U (0) – L (0)] F (0) = 0 + [1-0] [0] =0$
$U (1) = L (0) + [U (0) – L (0)] F (a_1) = 0 + [1-0] [0.6] =0.6$
$[0, 0.6]$
Step 3: $2^{nd}$ Symbol in sequence = $a_1$ = X (n=2)
$L (2) = L (1) + [U (1) - L (1)] F (a) = 0 + [0.6-0] [0] =0$
$U (2) = L(1) + [U (1) –L (1)] F (a_1) =0 + [0.6-0] [0.6] =0.36$
$[0, 0.36]$
Step 4: $3^{rd}$ Symbol in sequence = $a_2$=X (n=3)
$L (3) = L (2) + [U (2) -L(2)] F (a_1) = 0 +[ 0.36 -0] 0.6 =0.216$
$U (3) = L (3) + [U (2)- L (2)] F (a_2) = 0+ [0.36 -0] 0.8 = 0.288$
$[0.216 , 0.288]$
Step 5: $4^{th}$ Symbol = $a_1$ = X (n=4)
$L (4) = L(3) + [ U(3) - L(3)] F (0) = 0.216$
$U (4) = L(3) + [U (3) - L(3)] F (a_1) = 0.216 + [0.288-0.216] 0.6 =0.2592$
$[0.216 , 0.2592]$
Step 6: $5^{th}$ Symbol = $a_3$ =X (n=5)
$L(5) = L(4) + [ U (4) – L(4)] F (2) = 0.25056$
$U (5) = L (4) + [U (4) – L(4)] F (a_2) = 0.2592$
Step 7: Tag Generation
Tag = = 0.25488
v. Tag ( Fractional decimal number) represents given input of S symbols.
vi. If number of symbols increases in a sequence then it will just affect to resolution of tag but same tag can be represented in fixed number of bits.
vii. Disadvantage:
- The coded tag is sensitive to position symbol in sequence. If position of symbol changes it will result different value of tag.
- Tag cannot be generated / insert sequence.