Principles of Signal Design Flashcards
What is Occupied Bandwidth?
How much space the signal must physically take up in the frequency domain
“Null-to-Null”
What is Effective Bandwidth?
The Bandwidth actually used for transmitting data
What are Guard Intervals?
Intentional periods where signals do not transmit to prevent interfering with themselves
What are Guard Bands?
Unoccupied spaces between signals to prevent interfering with one another
What is the Roll Off Factor?
The difference in frequency between the effective and occupied bandwidths of a signal
What is Data Rate?
Speed at which raw data (without any added redundancy) is transmitted
What is Total Bit Rate?
Overall speed of all bits being transmitted, including raw data and any additional bits (such as error correction bits)
What is Symbol Rate?
Rate at which symbols are transmitted
What is the purpose of Forward Error Correction (FEC)?
Error detection and error correction
What is Simplex?
System that allows one-way communication from a transmitter to receiver (car radio)
What is Half-Duplex?
Communication system in which each end can transmit and receive, but not simultaneously (walkie-talkie)
What is Full-Duplex?
Each end can transmit and receive simultaneously (cellphone)
What is Time Division Multiplexing (TDM)?
The process of two or more signals physically taking turns on a channel
What is Frequency Division Multiplexing (FDM)?
Assigns non-overlapping frequency ranges to different signals or to each user of a medium
What is Code Division Multiplexing (CDM)?
A data signal is sent over a range of frequencies in an assigned frequency spectrum using a pseudo random spreading code to multiplex the base signal
Signals with different codes are laid over each other. As long as you have the code, you can discern the desired message
How does Multiple Access differ from Multiplexing?
Multiple Access occurs after transmission instead of before transmission
What is Frequency Division Multiple Access (FDMA)?
Users share the same satellite simultaneously, but each user transmits at a single frequency
What is an advantage and disadvantage of FDMA?
Advantage:
Simple, reliable
Disadvantage:
Needs more BW as you add users
What is Time Division Multiple Access (TDMA)?
Users share a single RF channel without interference by allocating different timeslots to each user
What is an advantage and disadvantage of TDMA?
Advantage:
Users enjoy full bandwidth
Disadvantage
Limited timeslots
What is Code Division Multiple Access (CDMA)?
Technique that codes every digital packet it sends with a unique key
What is an advantage and disadvantage of CDMA?
Advantage:
More resistant to jamming and interference than FDMA and TDMA
Disadvantage:
Equipment cost is higher
What does Phase Shift Keying do?
Changes phase of a carrier wave
What three properties of a wave can be changed by Modulation?
Frequency, Phase, and/or Amplitude
What are two advantages of Digital Signals over Analog?
- Compressible
- More resistant to interference and distortion
What advantage do Analog Signals have over Digital?
Easy to propagate
