Question

Question 2
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a) Assume you want to send a message consisting of the following bits

     11000101111110100100011100111110

assuming k = 6, how would you send this message using bit insertion? (my way, 
not the standard way)

b) Consider the following bit string

   0000101011111110

How would you send it using 4B/5B?

c) Same as b), but apply NRZI after applying 4B/5B

Answer 1

Q2 a)

Bit Stuffing is done to make our message distinguishable from flag value .This will help us to make sure that data starts and ends at correct places .

Example flag =1000001

Data = 100010000001

Now we send data by attaching flag at the start and end of the data so that receiver gets to know the starting and ending of the actual but if data bits matched with flag bits then it becomes a issue so to avoid that we use bit stuffing so

Flag Data Flag

Data sent will be 1000001 1000100001001 1000001 stuffed 1 after every 4 0's in the data

Similarly when k=6 means we need to stuff a 0 after every 5 1's

Flag here will be ---> 01111110

so Final Data that will be sent is with flag attaches at starting and ending of the data

Flag 1100010111110101001000111001111100 Flag

so we have 2 bit stuffing represented in bold 0.

Q2 b)

4b/5b algorithm  take groups of 4 bits of data and convert them to groups of 5 bits for transmission. The 5 bits are pre-defined for every 4 bit set

Table is

Steps

1 Divide the data into set of 4 bit binary string.

2. For each 4 bit search the table and write corresponding 5 bits set

Given Data

 0000101011111110

Step 1

Binary 4B/5B

0000 11110

1010 10110

1111 11101

1110 11100

So final 4B5B coded data will be

11110101101110111100

Q 2 c)

Non Return to Zero Inverted (NRZI) is a binary encoding method  used in transmission, where a data bit of 1 is positive voltage, and a data bit of 0 is negative voltage.

Whenever data is having a bit there is clock boundary transition i.e +ve to -ve or vice versa and when bit is 0 no transition take place

For above data NRZI after 4B/5B

11110101101110111100