GATE IT 2008 | Question: 18

Question

How many bytes of data can be sent in $15$ seconds over a serial link with baud rate of $9600$ in asynchronous mode with odd parity and two stop bits in the frame?

• A. $10,000$ bytes
• B. $12,000$ bytes
• C. $15,000$ bytes
• D. $27,000$ bytes

Comments

A_i_$_h

baud rate = 2 * bit rate

This is very incorrect.

Baud rate = Number of symbols sent per unit time.

When by "symbol" we mean a "bit", then we say Bit rate = Number of bits sent per unit time.

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Baud Rate = 2 * Bit Rate,

Only in the case where we are using manchestor and differential manchestor encoding.

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For those confused between bit rate and baud rate for serial communications see:
https://gateoverflow.in/1019/gate-cse-2004-question-22?show=10129#a10129

Answer 1

As given 9600 baud rate .

Generally relation between baud rate and bit rate , baud rate = N*bit rate

But here Nothing given , so baud rate = bit rate . 9600 bits / sec

and now we send 1 bytes with others bits parity bit , synchronize bit  etc

For 1 byte send  we will send 12 bits =1 bit for start bit, 8 bits for data, 1 bit for parity, 2 bits for stop bits.

As Here to send 1 byte takes 12 bits . Let replace byte will character word .

So total character sent 9600 bits/sec * 12 bit/character =800 character/sec

In 15 sec it will send 800 character/sec*15 sec = 12000 character .

Now again replace character with byte = 12000 byte .

Answer 2

for 8 bit of data → 12 bit is transmitted

means, for 8 bit → 4 extra bits transmitted

for x bits of data → x/2 extra bits will be transmitted

so, (x+x/2) bits = 15*9600 bits

=> 3x/2= 15*9600

=> x= 96000 bits

=> x= 9600/8 bytes

=> x=12000 bytes

Answer 3

it should be 13090 bytes= 9600x15/11

Comments

Start and stop bits for a byte of data are a must in asynchronous transmission. Therefore, even if start bit isn't mentioned in the question, we must add 1 start bit while calculating. 1(start) + 8(data byte in bits) + 1(parity) + 2(stop bits as per question) = 12 bits per character(i.e 12 bits per byte of 'data')