CS601 - Data Communication
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Q & A
Short Question & Answers
Q1: What is purpose of distributed processing?
Multiple computers working on a problem can solve a problem faster than a computer working alone.
Q2: What is HDB3?
Alteration of AMI adopted in Europe and Japan. Introduces changes into AMI, every time four consecutive zeros are encountered instead of waiting for eight zeros as in the case of B8ZS.
Q3: Differentiate between the following terms.
Frequency spectrum and bandwidth: Frequency Spectrum: of a signal is the collection of all the component frequencies it contains It is shown using a Frequency domain graph. Bandwidth: of a signal is the width of the frequency spectrum In other words, Bandwidth refers to the range of the component frequencies and Frequency Spectrum refers to the elements within that range.

Bandwidth and throughput: Measurement of how fast data can pass through a point o In other words, if we consider any point in the TX Medium as a wall through which bits pass, then throughput is the number of bits that can pass this wall in second

Bit interval and bit rate: Most digital signals are aperiodic and thus Period and Frequency are not the appropriate terms to describe them.

Bit Interval (seconds): Time required sending one single bit.
Bit Rate (bps): Number of bits sent per second.
Q4: What is the difference between guided and unguided media?
Guided Media are those media that provide a conduit from one device to another. Guided Transmission Media uses a "cabling" system that guides the data signals along a specific path while Unguided Transmission Media consists of a means for the data signals to travel but nothing to guide them along a specific path. It passes through a vacuum; it is independent of a physical pathway.
Q5: Write Commercial advantage and characteristics of token bus.
Other LANs are not suitable for this purpose. Token Bus has no commercial application in data communications. Token Ring allows each station to send one frame per turn. Access method: Token passing.
Q6: What is the difference between FDM and TDM?
FDM-Frequency division multiplexing whereas: In FDM spectrum is divided into frequency whereas in TDM divided into time slot. TDM mean Time division Multiplexing: FDM is used in 1st generation analog system whereas TDM is used in 2nd generation analog system.
Q7: Write the types transmission noise.
Thermal Noise: Due to random originally sent by TX.
Induced Noise: Comes from sources like Motors and Appliances.
Crosstalk: Effect of one wire on another. Impulse Noise: Spike (A signal with high energy in a very short period of time power lines, lightening etc.
Q8: What is power bandwidth?
The power bandwidth of an amplifier is sometimes taken as the frequency range (or, rarely, the upper frequency limit) for which the rated power output of an amplifier can be maintained (without excessive distortion) to at least half of the full rated power. OR Power Bandwidth Frequency band in which 99% of the total power resides.
Q10: What does the CRC generator append to data unit?
Appending it to the end of the data must make the resulting bit sequence exactly divisible by the divisor.
Q11: How much bandwidth for modem is required in case of FSK?
BW required for FSK is equal to the Baud rate of the signal plus the frequency shift. Because of the limitations of voice-grade telephone lines, these modems are restricted to a bandwidth of about 3 kHz.
Q12: What is even parity generator in VRC error detection mechanism?
Even parity generator counts the 1‟s and appends the parity bit (1) to the end.
Q13: What is the difference between angle of incident and angle of reflection?
The difference between them is that Angle of refraction passes from less dense to denser medium whereas angle of incidence passes from more dense to less dense medium.
Q14: What is daisy chaining in 1Base 5 star Lan?
Slower speed in star lan can be increase by the use of DAISY CHAINING.
Q15: What is the responsibility of Application layer?
Enables the user either human or software to access the network It provides user interface and support for the services such as Electronic mail, Remote File access and Transfer, Shared Database Management and other services.
Q16: What is critical angle?
We have a beam of light moving from a more dense to a less dense medium. We gradually increase the angle of incidence measured from vertical axis. As angle of incidence increases, so does the angle of refraction. The angle at which refracted line lies on the horizontal axis is called Critical Angle.
Course Instructor

Mr. Hammad Khalid Khan
M.S Electrical Engineering (Telecommunication) Oklahoma State University USA

Data Communication and Networking by Behrouz A. Forouzan

Data and Computer Communication by William Stallings