Politécnica University of Puerto Rico - Hato Rey

Computer Engineering Department

Assignment 1

Christian O. Pérez Pérez – 89536

6. Chapter 6
6.1. Give three examples of information sources other than computers.
 Microphone
 Sensor
 Thermometer or scale or measurement devices
6.3. Why are sine waves fundamental to data communications?

Sine waves are fundamental to input processing because many natural phenomena produce a
signal that corresponds to a sine wave as a function of time.

6.6. When is a wave classified as simple?

Wave are classified simple when they cannot be decomposed further. They cannot be
decomposed any further when the wave is composed of a single sine wave.

6.7. What does Fourier analysis of a composite wave produce?

Fourier analysis helps to decompose a composite signal in multiple simple sine waves.

6.9. What is the analog bandwidth of a signal?

Is the difference between the highest and the lowest frequency of its component.

6.14.What is the bandwidth of a digital signal? Explain.

It is infinite the bandwidth because Fourier analysis of a digital signal produces an infinite set of
sine waves with frequencies that grow to infinity

6.19.When converting an analog signal to digital, what step follows sampling?

Is used to distinguish between physical media such as copper wiring or optical fibers that
provide a specific path and a radio transmission that travels in all directions through free space.
They are informally called wired and wireless but it can be confusing to use these terms.

7.4. What three types of wiring are used to reduce interference form noise?
 Unshielded Pair (UTP)
 Coaxial cable
 Shielded Twisted Pair (STP)
7.12.What is the chief disadvantage of optical fiber as opposed to copper wiring?
 Copper wiring is less expensive.
 Because the ends of an optical fiber must be polished before they can be used, installation
of copper wiring does not require as much special equipment or expertise as optical fiber.
 Copper wires are less likely to break if accidentally pulled or bent.
7.17.List the three types of communications satellites, and give the characteristics of each.
  Low Earth Orbit (LEO) – Has the advantage of low delay, but the disadvantage that form an
observer’s point of view on the earth, the satellite appears to move across the sky.
 Medium Earth Orbit (MEO) – An elliptical (rather than circular) orbit used to provide
communication at the North and South Poles.
 GEO Stationary Earth Orbit (GEO)- Has the advantage that the satellite remains at the fixed
position with respects to a location on the earth’s surface, but the disadvantage of being
farther away.
7.21.What is the relationship between bandwidth, signal levels, and data rate?
For K possible signal levels and bandwidth B the data rate D is:
D=2 B log2K
8. Chapter 8
8.1. List and explain the three main sources of transmission errors.
 Interference - Electromagnetic radiation emitted from devices such as electric motors and
background cosmic radiation cause noise that can disturb radio transmissions and signals
traveling across wires.
 Distortion - All physical systems distort signals. As a pulse travels along an optical fiber, the
pulse disperses. Wires have properties of capacitance and inductance that block signals at
some frequencies while admitting signals at other frequencies. Simply placing a wire near a
large metal object can change the set of frequencies that can pass through the wire.
Similarly, metal objects can block some frequencies of radio waves, while passing others.
 Attenuation - As a signal passes across a medium, the signal becomes weaker. Engineers say
that the signal has been attenuated. Thus, signals on wires or optical fibers become weaker
over long distances, just as a radio signal becomes weaker with distance.
8.2. How do transmission errors effect data?
Transmission errors can cause data errors. The main data errors are:
 Single bit error- This is when only a single bit in a block of bites is changed. This is often
caused by short duration interference
 Burst Error- Multiple bits in a block of bites are changed. Often results form longer-duration
interference.
 Erasure (ambiguity) Error- The signal that arrives at the receiver is ambiguous and does not
clearly correspond to either a logical 1 or a logical 0 (can result from distortion or
interference).
8.14.What are the characteristics of a CRC?
The main characteristic of Cyclic Redundary Code (CRC) are:
 Arbitrary Length Message - As with a checksum, the size of a data word is not fixed, which
means a CRC can be applied to an arbitrary length message.
 Excellent Error Detection - Because the value computed depends on the sequence of bits in
a message, a CRC provides excellent error detection capability.
 Fast Hardware Implementation- Despite its sophisticated mathematical basis, a CRC
computation can be carried out extremely fast by hardware.
9. Chapter 9
9.1. Describe the difference between serial and parallel transmission.
 Serial —
o one bit is sent at a time
 o Slow speed transmission
o Uses fewer physical wires
o Cheaper
o Does not experience timing problem.
 Parallel —
o Multiple bits are sent at the same time.
o Higher speed
o Use more physical wires
o More expensive
o May face timing problems
9.2. What are the advantages of parallel transmission? What is the chief disadvantage?
 Advantages:
o High Throughput. Because it can send N bits at the same time, a parallel interface
can send N bits in the same time it takes a serial interface to send one bit.
o Match To Underlying Hardware. Internally, computer and communication hardware
uses parallel circuitry. Thus, a parallel interface matches the internal hardware well.
 Disadvantages
o Use more physical wires
o May face timing problems
o More expensive
9.4. What is the chief characteristic of asynchronous transmission?
Because it permits a sender to remain idle an arbitrarily long time
between transmissions, an asynchronous transmission mechanism
sends extra information before each transmission that allows a receiver to synchronize with the
signal.
9.8. When two humans hold a conversation, do they use simplex, half-duplex, or full-duplex
transmission?
Full-duplex since it the transmission is in the two directions simultaneously.
10. Chapter 10
10.1.List the three basic types of analog modulation.
 Amplitude Modulation
 Frequency Modulation
 Phase Shift Modulation
10.3.Using Shannon’s Theorem, explain why practical amplitude modulation systems keep the
carrier near maximum strength.
Having the carrier wave at maximum ensures that the signal to noise ratio remains High.
10.4.What is the difference between shift keying and modulation?
Shift keying is used for digital signals and the modulation is used for analog signals. In essence,
shift keying operates similar to analog modulation. Instead of a continuum of possible values,
digital shift keying has a fixed set.
11. Chapter 11
11.2.What are the four basic types of multiplexing?
 Frequency division multiplexing
  Wavelength Divisional Multiplexing
 Time Division Multiplexing
 Code Division Multiplexing
11.3.How does FDM use electromagnetic radiation?
A set of radio stations can transmit electromagnetic signals simultaneously without
interference, provided they each use a separate channel
11.6.Explain how a range of frequencies can be used to increase data rate.
To increase the overall data rate, a sender divides the frequency range of the channel into K
carriers, and sends 1/K of the data over each carrier. In essence, a sender performs frequency
division multiplexing within the channel that has been allocated. Some systems use the term
subchannel allocation to refer to the subdivision.
11.15. Of the four basic multiplexing techniques, is CDM always the best? Explain.
Yeas because CDM uses a mathematical combination of codes that permits multiple senders
to transmit at the same time without interference (values from orthogonal vector spaces can
be combined and separated without interference) . The chief advantages of CDM arise from
the ability to scale with low delay.[ CITATION Com15 \l 1033 ]

Bibliography
Comer, D. E. (2015). Computer Networks and Internets. In D. E. Comer, Computer Networks and
Internets (pp. 127-229). Lafayette: Pearson.