BCA 3040– DATA COMMUNICATION

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Assignment

PROGRAM	BCA(SPRING 2015)
SEMESTER	3
SUBJECT CODE & NAME	BCA 3040– DATA COMMUNICATION
CREDIT	4
BK ID	B1644
MAX.MARKS	60

1. What is modulation? Explain why modulation is required?

Answer : Modulation is the addition of information (or the signal) to an electronic or optical signal carrier. Modulation can be applied to direct current (mainly by turning it on and off), to alternating current, and to optical signals.

Amplitude modulation (AM

Frequency modulation (FM),

Phase modulation (PM), in which the natural flow of the alternating current waveform is delayed temporarily

Modem Modulation and Demodulation

A computer with an online or Internet connection that connects over a regular analog phone line includes a modem.

Need for modulation

The aim of digital modulation is to transfer a digital bit stream over an analog bandpass channel, for example over the public switched telephone network

2. Write short note on:

1. Ground Wave Propagation

Answer : Ground Wave propagation is a method of radio frequency propagation that uses the area between the surface of the earth and the ionosphere for transmission.

2. Sky Wave Propagation

Answer : Sky wave propagation: The sky waves have frequency range between 2MHz to 30MHz.

Some important terms which are used more frequently in sky wave propagation are given below:

1.            Maximum Usable frequency

2.            Critical frequency

3.            Skip distance

4.            Fading

3. Briefly explain Nyquist theorem with mathematical representation.

Answer : The Nyquist–Shannon sampling theorem, which has been named after Harry Nyquist and Claude Shannon, is a fundamental result in the field of information theory,

4. What is Time-division multiplexing (TDM)? Explain.

Answer : TDM is a common form of sending multiple signals or streams of information on a carrier at the same time in the form of a single

Benefits and shortcomings of TDM

The relative simplicity and low cost of TDM hardware devices makes it possible to build cost-effective networks of widely varying node count, geographic extent, capacity, and speed.

Examples of TDM based services

Public telephone networks

T1 - The T-carrier system is entirely digital, using pulse code modulation and time division multiplexing.

5. Write short note on:

1. Least-Cost Algorithms

Answer : In practice, the majority of Internet routing methods are based on least-cost algorithms. In such algorithms, a link cost is proportional to the links's current traffic load.

2. Dijkstra’s Algorithm

Answer : Dijkstra's algorithm, conceived by computer scientist Edsger Dijkstra in 1956 and published in 1959,^[1][2] is a graph search algorithm that solves the single-source shortest path problem for a graph with non-negative edge path costs, producing ashortest path tree

6. What are the requirements of Wirelesses LAN? Explain briefly

Answer : A wireless LAN must meet the same sort of requirements typical of any LAN, including high capacity, ability to cover short distances, full connectivity among attached stations, and broadcast capability. In addition, a number of requirements are specific to the wireless LAN environment. The following are among the most important requirements for wireless LANs:

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