SEW progress check 2 Flashcards
(64 cards)
decibel (dB
-used to measure signals and communication
a logarithmic unit used to measure signals and communication; express a ratio relative to a reference value on a logarithmic scale
___________turns exponential changes into linear changes
Logarithmic scaling
Linear scales
1, 2, 3, 4, etc
Logarithmic scales
1, 10, 100, etc.
_______compares the level of desired signal to the level of background noise
SNR = Psignal / Pnoise
Signal-to-Noise Ratio (SNR)-
__________ rate at which a transmitted segment of data is received with incorrect bits as compared to the original message.
*increase noise floor = data messed up so increase transmit power
Bit Error Rate (BER)
_________ common means of encoding data to determine if any errors have been introduced to the message through channel noise, interference, or other source
Error Detection
Why choose 1/2 over 7/8
-1/2 costs more bandwidth, but ensures data is able to be corrected by sending the most parity bits, most protected
-7/8 has faster data rates, but is more prone to errors
common nodes in a communication network (such as satellites) must be interconnected with all types of users as flexibility as possible.
Multiple access
_____________ assigned bandwidth is divided into segments
- User operates at the same time, using different frequencies
Frequency Division Multiple Access (FDMA) -
________ allocation of specific time slots for transmission
- User operate on same frequencies, different times
Time Division Multiple Access (TDMA)
_____________ all users transmit signals simultaneously on the multiple access channel
Code Division Multiple Access (CDMA)
_____________ the process of combining signals into a composite baseband to modulate on to a single carrier
Multiplexing
Spread spectrum
a telecommunications technique that transmits a signal over a wider frequency band than the original information
-think Hedy Lamar, she created this, breaks apart signal, spreads it across frequency, Spread spectrummakes it hard to Jam.
_________digital sequence that is intended to resemble a random succession of ones and zeros
Pseudo-random-noise (PRN) spread sequence
Pseudo-random-noise (PRN) spread sequence
-resembles random succession of ones and zeros
-hides signal from adversaries
-allows multiple users to use the same frequencies simultaneously
__________carrier frequency of the transmitted wave changes at regular intervals, based on pseudorandom sequence.
Frequency Hopping Spread Spectrum (FHSS)
__________ uses PRN code sequence to directly modulate the baseband information, allowing the user to operate below the noise floor
Direct Sequence Spread Spectrum (DSSS)
__________combines multiple streams of data into one baseband signal
Multiplexer (MUX)
__________overlays baseband data onto a carrier wave resulting in the creation of the intermediate frequency (IF)
Modulator (MOD)
___________ increase the modulated waveform from the intermediate frequency IF to the transmit radio frequency (RF)
Upconverter (U/C)
_________raise the signal power to the required output level
High Power Amplifier (HPA)
___________ raises the received low-power signal with minimal addition to noise
Low Noise Amplifier (LNA)
____________converts the received RF to the IF frequency
Down Converter
