COMPUTER NETWORKS & DATA COMMUNICATION – II CE-414

ASSIGNMENT # 2

 (DATA & SIGNALS)

Due Date: 23rd February, 2009

Question 1: If a binary signal is sent over a 4 kHz telephone channel whose signal to noise ratio is 30 dB, what is the maximum achievable data rate?

Question 2: What signal to noise ratio is needed to put an T1 carrier on a 100 kHz line? For the data rate of an T1 signal consult a reference.

Question 3: It is desired to send a sequence of computer screen images over an optical fiber. The screen is 800 X 600 pixels using 256 colors. There are 30 screen images per second. How much bandwidth is needed to transmit this signal using binary signaling?

Question 4: How long does it take to transmit an 8 inch by 10 inch image by facsimile over an ISDN B channel? The facsimile digitizes the image into 400 pixels per inch and assigns 2 bits per pixel. For the data rate of an ISDN consult a reference.

Question 5: Television channels are 6 MHz wide. How many bits/sec can be sent if 8 level digital signals are used? Assume a noiseless channel.

Question 6: Given a channel with an intended capacity of 25 Mbps. The bandwidth of the channel is 4 MHz. What signal to noise ratio is required in order to achieve this capacity?

Question 7: Suppose that a digitized television picture is to be transmitted from a source that uses a matrix of 1600 by 1200 picture elements (pixels), where each pixel represents one of 65,536 colors. Assume that 30 pictures (frames) are sent per second.

(a) Find the data rate R of the source in bits per second.

(b) Assume that the picture is to be transmitted over a 10 MHz channel with channel capacity equal to the data rate required for the signal. If M-ary signaling is to be used to accommodate the video signal on the channel what smallest value of M is required?

Question 8: Is Nyquist Theorem true for optical fiber, or only for copper wire?

Question 9:

(a) Imagine a Signal travels through a transmission medium and its power is reduced to half. Calculate the attenuation (loss of power) in dB?

(b) Imagine a Signal travels through an amplifier and its power is increased 10 times. Calculate the amplification (gain of power) in dB?

(c) We can calculate the theoretical highest bit rate of a regular telephone line. A telephone line normally has a bandwidth of 3000Hz (300Hz to 3300Hz). The Signal-to-Noise ratio is usually 35dB. For this channel calculate the highest bit rate? If we want to send data faster than this, what can we do?

Question 10:We measure the performance of a telephone line (4KHz of bandwidth). when the signal is 20V, the noise is 6mV. what is the maximum data rate supported by this telephone line?

Question 11: What is the total delay (latency) for a frame of 10 million bits that is being sent on a link with 15 routers each having a queuing time of 2µs and the processing time of 1µs. the length of the link is 3000Km. The speed of the light inside the link is 2x10m/s. The link has a bandwidth of 6 Mbps. Which component of the total delay is dominant? Which one is negligible?

Question 12: A TV channel has a bandwidth of 6MHz? if we send a digital signal using one channel, what are the data rates if we once harmonic, three harmonics, and five harmonics?

Question 13: An non-periodic composite signal contains frequencies from 10 to 40 KHz. The peak amplitude is 12V for the lowest and the highest signals and is 30V for the 20Khz signal. Assuming that the amplitudes change gradually from the minimum to the maximum, draw frequency spectrum.

Question 14:what is the bandwidth of a signal that can be decomposed into five sine waves with frequencies at 0, 30, 40, 120, and 300Hz? All peak amplitudes are the same. Draw the bandwidth.

Question 15: The light of the sun takes approximately eight minutes to reach the earth. What is the distance between the sun and the earth?