dcs important

Date of Exam:

COMPUTER SCIENCE ENGINEERING

SRI SAI ADITYA INSTITUTE OF SCIENCE AND TECHNOLOGY

DATA COMMUNICATIONS SYSTEMS

II MID EXAMINATION

UNIT V

1.      Explain about caller ID in telephone system.

2.      Interpret the following hex code for a caller ID message (Start and stop bits are not included in the hex codes)

04 12 31 31 32 37 31 35 35 37 33 31 35 37 33 36 31 30 35 33 XX

3.      What is a telephone set? Describe in detail with a neat sketch about various functional components of a standard telephone set?

4.      What is the difference between dB and dBm? Determine power levels in dBm for signal levels of 10mW and 0.5mW?

5.       Compare the operation of cordless telephone and standard telephone?

UNIT VI

1.      What is the digital cellular system? List its advantages?

2.      What is N-AMPS cellular telephone system? Explain its operation.

3.      What are the three primary subsystems of GSM? Explain in detail the GSM system architecture.

4.      Briefly explain the architecture of GSM?

5.      What is meant by false-handoff? What are the four types of handoffs possible with N-AMPS?

UNIT VII

1.      Explain the terms: bits per second, baud, probability of error, bit error rate with an example each.

2.      What is modem? Compare synchronous and asynchronous modems. Explain the four types of modem operational modes.

3.      What is POSTNET? What is POSTNET bar code? Determine the check character for the POSTNET nine-digit ZIP+4 numbers: 13424-7654.

4.      What is modem synchronization? What are its functions? Compare cable modems and standard voice band modems.

5.      What is hamming code? For a 12-bit data string of: 101100010010, determine the number of Hamming bits required, arbitrarily place the hamming bits into the data string, determine the logic condition of each hamming bit, assume an arbitrary single-bit transmission error and prove that the hamming will successfully detect the error.

UNIT VIII

1.      What is a data link protocol? List and describe in detail the three data link protocol functions.

2.      What is the difference between synchronous and non synchronous data link protocols? Explain with a neat frame format how the XMODEM protocol works.

3.      What is an invert on zero encoding? Obtain non return to zero inverted (NRZI) encoding to the data stream.  100111001010100010111000111

4.      Explain about (i) Character and bit oriented data link protocols.

         (ii) Data transmission modes

5.      What is SDLC? Describe in detail the various fields of the SDLC frame format.