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EE 314 > Quiz 3 > Flashcards

Quiz 3 Flashcards

(53 cards)

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1
Q

Spatial separation

A

allows frequency re-use
- ex: wifi (can see neighbors wifi but not out of SLO)

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2
Q

what allows frequency re-use

A

Polarization separation
TDMA
Orthogonal Waveforms (has to be completely 90 degrees)

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3
Q

achieving high thruput observations

A

more orthogonal degrees of freedom enable more capacity (thruput)

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4
Q

each degree of freedom _________

A

imposes constraints
ex: freq accuracy, guard bands, polarization accuracy, timing accuracy

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5
Q

constraints add _________ and reduce ________

A

to system complexity; flexibility

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6
Q

Central limit thm

A

all the world’s Gaussian, and all constituents merely add up to noise
(gaussian plot/bead thing)

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7
Q

WSS

A

wide sense stationary process

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8
Q

in WSS and PSD, mean and variance are

A

time-independent

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9
Q

in WSS and PSD, autocovariance depends only on

A

lag between t1 and t2

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10
Q

Power Spectral Density describes ___________

A

power distribution with respect to frequency

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11
Q

sample PDFs

A

(on iphone)

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12
Q

what is erf(x)?

A

error function
- the delta function between two limits

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13
Q

what is the Q function?

A

the right tail of the PDF

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14
Q

what is erfc(x)?

A

complementary error function
erfc = 1 - erf
- area under the two tails of zero mean Gaussian PDF

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15
Q

Noise is modeled as AWGN (what is AWGN?)

A

additive white Gaussian noise
- present in all freqs
-

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16
Q

PDF, CDF, and Q functions are most useful for __________

A

calculating probabilities

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17
Q

FSK

A

frequency domain (phase modulation)

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18
Q

BPSK

A

time domain (phase modulation)

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19
Q

Graphs of BPSK, QPSK, 8- 16- 64- ary

A

on ipad

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20
Q

high order modulation is limited by ______

A

SNR

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21
Q

Shannon’s Law

A

C = Blog2(1+SNR)
C: capacity
B: bandwidth
SNR: signal to noise ratio

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22
Q

for Shannon’s law, high bandwidth means high _________

23
Q

log2(M) =

Study These Flashcards
A

log10(M)/log10(2)

24
Q

higher data rates require

Study These Flashcards
A

higher SNR’s

25
constraints of BER
- no weather margin - no implementation margin - JPL typical 2 dB
26
OFDMA
- orthogonal freq division multiplexing - data is spread across all carriers or channels - based on idea that we can have ortho freqs - dont need a guard band
27
what is special about OFDMA?
robust/immune to fading & multipath (time delay)
28
DSSS
- discrete spread spectrum signal - low data rate signal spread over wide-band - inverse to get og signal
29
negative about DSSS
- a lot of bandwidth to spread low data
30
advantages about DSSS
send signals at lower power - doesn't require exquisite timing alignment of TDMA - not susceptible frequency effects of FDMA - guard band
31
CDMA
- code division multiple access - spread spectrum techniques like DSSS - choose orthogonal codes to spread data
32
codes are orthogonal when ______
dot product is zero
33
how to maximize capacity?
maximize SNR or maximize bandwidth or BOTH
34
free space path loss eqn
Lp = (4piR/lambda)^2
35
FSK requires _______ _____ than BPSK to achieve the same BER
greater SNR
36
coherent reception will have ______ signal level than non-coherent
greater - FSK coherent BER curve is lower than FSK non-coherent
37
DPSK is _____
non-coherent
38
DPSK performs a little _____ than coherent BPSK
worse - DPSK curve will be a little higher than BPSK
39
QPSK sends _______ at the _____
two bits; same time - each bit gets half the power
40
QPSK has ___ energy per bit as BPSK
same
41
QPSK and QAM are ______
the same thing
42
advantage of QPSK over BPSK?
QPSK allows you to double the data rate
43
maximizing receiver output SNR in AWGN
leads to minimizing detection error probability
44
error probability depends on
noise probability density function
45
what does BER stand for
bit error rate
46
mega
10^6
47
log(10)
1 dB
48
10log(10)
10 dB
49
10log(2)
3 dB
50
10log(4)
6 dB
51
10log(100)
20 dB
52
10log(1000)
30 dB
53
10log(10000)
40 dB

EE 314 (2 decks)

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