Introduction to Communication Systems

Question 1

What are examples of wired communications?

Answer 1

traditional telephone communications and traditional local area network (LAN).

Question 2

What are examples of wireless communications?

Answer 2

Radio and TV broadcast, WiFI, Cellular Network, Satellite Communication, Visible Light Communication.

Question 3

What are the 3 primary components to a satellite communication system?

Answer 3

Earth TRansmitting station, satellite (in geostationary orbit), and Earth Receiving Station.

Question 4

What is the term used to describe a signal being transmitted from the Earth Transmitting station to a satellite?

Answer 4

Uplink

Question 5

What is the term used to describe a signal being transmitted from a Satellite to a Earth Receiving Station?

Answer 5

Downlink

Question 6

What is a Communication System?

Answer 6

Communication involves the transfer of information from one point to another.

Question 7

What are the 3 basic elements to a communication system?

Answer 7

-Transmitter: converts messages into a form suitable for transmission.
-Channel: a physical medium, introduces distortion, noise, and interference.
-Receiver: reconstructs a recognizable form of the message.

Question 8

What does a transmitter do?

Answer 8

It modifies the message signal into a form suitable for transmission over the channel.

Question 9

WHat is the term used to describe the modification of the message signal into a form suitable for a transmission over a channel by a transmitter?

Answer 9

Modulation

Question 10

What are some forms of analog modulation?

Answer 10

AM, FM, PM

Question 11

What are some forms of digital modulation?

Answer 11

ASK, FSK, PSK (SK: shift keying)

Question 12

WHat is the function of a the receiver?

Answer 12

it recovers the original message by demodulation. Recovery may not be exact due to noise/distortion. The resulting degradation is influenced by the type of modulation.

Question 13

Which type of modulation is conceptually more simple?

Answer 13

analog

Question 14

What are the benefits of digital modulation over analog?

Answer 14

more efficient and reliable

Question 15

What is a disadvantage of a digital modulation over analog?

Answer 15

Designs can be more complicated.

Question 16

What is a common goal in a transmitter design?

Answer 16

To make it more energy efficient

Question 17

What is a common goal in a receiver?

Answer 17

How can we reduce noise to properly improve the probability of accurate reception.

Question 18

WHat is modulation?

Answer 18

How we put information of message signal on a carrier signal

Question 19

What is a unavoidable presence in a channel?

Answer 19

noise

Question 20

What is noise?

Answer 20

Its an unwanted waves that disturb communications. The signal is contaminated by noise along the path.

Question 21

What is the term used to describe interference from nearby channels, human made noise, and natural noise?

Answer 21

External noise

Question 22

What is the basic factor that sets limits on communications?

Answer 22

Noise

Question 23

What is a widely used metric to determine the basic factor that creates a limit on communications?

Answer 23

Signal to noise ratio = Signal power / noise power

Question 24

Why is analog communication not ideal compared to digital?

Answer 24

Analog is prone to getting noise distorting the signal.

Question 25

How can we achieve perfect communication with an imperfect communication channel?

Answer 25

Yes, via digital communications.

Question 26

Is there an upper bound on the information capable of being sent under different noise conditions?

Answer 26

Yes, its called channel capacity which is derived by C = B*log2(1 + SNR) in units of piece per second (Hertz).

Question 27

If we increase the transmission rate over a noisy channel, will the error rate increase?

Question 28

Why do we still use analog communications today?

Answer 28

SImplicity. You just need a resistor, inductor, and capacitor to generate a AM transmitter.

Question 29

What are the goals of SNR?

Answer 29

Either Increase the signal power or reduce the noise power to increase the SNR.

Question 30

Who is the father of digital communications?

Answer 30

Claude Shannon

Question 31

WHo wrote "A Mathimatical Theory of Communication", Bell System Technical Journal, vol. 27, pp. 379-423, 623-656, July, October 1948?

Answer 31

Claude Shannon

Question 32

What does Entropy measure?

Answer 32

Information, or uncertainty, and how much information we can achieve over each channel.

Question 33

What is the Channel Capacity Formula?

Question 34

Is reliable information transmission always possible? If it is, what are the conditions?

Answer 34

Yes its always possible if the transmitting rate does not exceed the channel capacity.

Question 35

Who invented the first radio?

Answer 35

Marconi in the 1880s.

Question 36

What are examples of ancient wireless communications?

Answer 36

smoke signals, carrier pigeons.

Question 37

What are characteristics of Wireless AD HOC networks?

Answer 37

The are (1) Decentralized and (2) broadcast Nature. So transmitting nodes are interfering with each other. The performance of a wireless network is highly limited by interference.

Question 38

What are the dimensions to reducing noise in a communication system?

Answer 38

1. Time domain, 2. Frequency domain, 3. Space

Question 39

What is a model the coverage area used for traditional cellular networks called

Answer 39

Hexagon-based cellular networks

Question 40

What is the perfect model shape for a wireless communication system for cellular?

Answer 40

Circle, but its typically not done because its more complicated for doing analysis.

Question 41

When did 1G, 2G, 3G, 4G, and 5G become implemented in cellular communications?

Answer 41

1981, 1992, 2001, 2011, and 2020 (Respectively)

Question 42

What type of communication was implemented with 3G?

Answer 42

CDMA (developed by Qualcom. This code separates the signals, and reduces the noise , and reduces space, so it utilizes the 3 types of technology.

Question 43

What was the major revolution with 4G?

Answer 43

It used multiple antenna technology. It can make spatial transmission more efficient. Sometimes its called MIMO, and this is the differentiating feature of 4G from 5G.

Question 44

What was the innovation of 5G?

Answer 44

It used mmWave, so higher frequency.

Question 45

What is the goal in the development of new cellular communications technolgy?

Answer 45

To find more bandwidth