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
method of adding redundant information to a data stream that allows for identification and correction of errors, and thus reduces or eliminates the need for retransmission
Forward Error Correction (FEC)-
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
______ increases the amount of bandwidth required
(FEC) Forward error correction
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)
