Assignment Questions Flashcards
What are the three basic parts of a communication system
Transmitter, Channel, Receiver
What are the 3 major regions of the atmosphere?
Troposphere, Stratosphere, Ionosphere
Which atmospheric region has relatively little effet on radio waves?
Stratosphere because it has low atmostpheric phenomena and low concentration of ions.
Which layer of the atmosphere does virtually all weather phenomena occur?
Troposphere
Which region of the atmosphere is considered most important for long range communications and why?
Ionosphere due to sky wave transmissions.
What three factors affect the amount of refraction off the ionosphere?
Frequency, ionization, angle of incidence.
Explain the PCM encoding process
Sampling - Signal is sampled at regular intervals
Quantization - each sample is assigned a digital value
Encoding - the quantized values are encoded into digital format
What are 3 types of ARQ
Stop-and-Wait
Go-Back-N
Selective Repeat
Define ARQ
Automatic Repeat Request is an error control and packet recovery method for data transmission.
What is the difference between codes and ciphers?
Codes: Replace entire words with other words or phrases.
Ciphers: Transform individual characters
List 3 ways to defend your system from a brute force attack
Strong encryption algorithm with large bit keys
Rate limiting attempts
Multifactor authentification
List three items you would keep classified to maintain the integrity of your encryption system
-Encryption keys
-Key management process - how they are generated, stored, and distributed
-System architecture - security protocols
Explain the difference between multiplexing and multiple access
Multiplexing - allows users to combine signals for transmission
Multiple access - how multiple users share access to a comms channel
Why would you use manchester encoding?
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.
Why would you use differential manchester encoding?
Ensures synchronization as well. Used where data integrity is most important.
Describe total internal reflection
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.
what are two sources of error in delta modulation?
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.
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
Sample - Quantize - Encode
Decode - Sample and Hold - Smoothing
