Assignment Questions

Question 1

What are the three basic parts of a communication system

Answer 1

Transmitter, Channel, Receiver

Question 2

What are the 3 major regions of the atmosphere?

Answer 2

Troposphere, Stratosphere, Ionosphere

Question 3

Which atmospheric region has relatively little effet on radio waves?

Answer 3

Stratosphere because it has low atmostpheric phenomena and low concentration of ions.

Question 4

Which layer of the atmosphere does virtually all weather phenomena occur?

Answer 4

Troposphere

Question 5

Which region of the atmosphere is considered most important for long range communications and why?

Answer 5

Ionosphere due to sky wave transmissions.

Question 6

What three factors affect the amount of refraction off the ionosphere?

Answer 6

Frequency, ionization, angle of incidence.

Question 7

Explain the PCM encoding process

Answer 7

Sampling - Signal is sampled at regular intervals
Quantization - each sample is assigned a digital value
Encoding - the quantized values are encoded into digital format

Question 8

What are 3 types of ARQ

Answer 8

Stop-and-Wait
Go-Back-N
Selective Repeat

Question 9

Define ARQ

Answer 9

Automatic Repeat Request is an error control and packet recovery method for data transmission.

Question 10

What is the difference between codes and ciphers?

Answer 10

Codes: Replace entire words with other words or phrases.

Ciphers: Transform individual characters

Question 11

List 3 ways to defend your system from a brute force attack

Answer 11

Strong encryption algorithm with large bit keys
Rate limiting attempts
Multifactor authentification

Question 12

List three items you would keep classified to maintain the integrity of your encryption system

Answer 12

-Encryption keys
-Key management process - how they are generated, stored, and distributed
-System architecture - security protocols

Question 13

Explain the difference between multiplexing and multiple access

Answer 13

Multiplexing - allows users to combine signals for transmission

Multiple access - how multiple users share access to a comms channel

Question 14

Why would you use manchester encoding?

Answer 14

Synchronization because each bit has a transition which helps in clock recover. However, it doubles the bandwidth since each bit is represented by two level transitions.

Used where synchronization is most important.

Question 15

Why would you use differential manchester encoding?

Answer 15

Ensures synchronization as well. Used where data integrity is most important.

Question 16

Describe total internal reflection

Answer 16

occurs when all of the light hitting the interface between the core and outer layer fo a fibre optic cable is reflected back internally to the core. This occurs when the refractive index of the core material is higher than the outer layer and the angle of incidence exceeds the critical angle.

Question 17

what are two sources of error in delta modulation?

Answer 17

Slope overload distortion: The input signal changes too rapdily for the modulator to keep up.

Granular noise: the step size of the modulator is too large relatvie to the variations of the input signal. When the input signal is relatively constant, the output value will oscillate, causing noise.

Question 18

What are is the process for how a PCM system converts an analog signal into a digital data stream then recovers an analog signal at the receiver

Answer 18

Sample - Quantize - Encode

Decode - Sample and Hold - Smoothing