Deck 10: Modulation Schemes and Access Techniques for Spread Spectrum Systems

Question 1

Which modulation scheme is preferred for direct sequence spread spectrum process?

A)bpsk
B)qpsk
C)bpsk & qpsk
D)none of the mentioned

Answer 1

bpsk & qpsk

Question 2

The processing gain is given as_________  modulation scheme.

A)wss/r
B)r/wss
C)wss/2r
D)r/2wss

Answer 2

wss/r

Question 3

The minimum spacing between consecutive hop positions gives the

A)minimum number of chips necessary
B)maximum number of chips necessary
C)chip rate
D)none of the mentioned

Answer 3

minimum number of chips necessary

Question 4

Which system allows larger processing gain?

A)direct sequence
B)frequency hopping
C)direct sequence & frequency hopping
D)none of the mentioned

Question 5

In which technique is phase coherence hard to maintain?

A)direct sequence
B)frequency hopping
C)direct sequence & frequency hopping
D)none of the mentioned

Question 6

Which type of demodulator is used in the frequency hopping technique?

A)coherent
B)non coherent
C)coherent & non coherent
D)none of the mentioned

Question 7

Robustness gives the inability of a signal to withstand the impairments.

Question 8

Chips are the

A)repeated symbols
B)non repeated symbols
C)smallest length symbols
D)none of the mentioned

Question 9

Slow frequency hopping is

A)several hops per modulation
B)several modulations per hop
C)several symbols per modulation
D)none of the mentioned

Question 10

Fast frequency hopping is

A)several modulations per hop
B)several modulations per symbol
C)several symbols per modulation
D)none of the mentioned

Question 11

Which duration is shorter?

A)hop duration
B)symbol duration
C)chip duration
D)none of the mentioned

Question 12

Frequency division multiple access (FDMA) assigns_________  channels to_________     users.

A)individual, individual
B)many, individual
C)individual, many
D)many, many

Question 13

If the FDMA channel is not in use, it can be used by other users.

Question 14

The bandwidth of FDMA channel is

A)wide
B)narrow
C)large
D)zero

Question 15

Which of the following is not true for FDMA systems as compared to TDMA systems?

A)low complexity
B)lower cell site system cost
C)tight rf filtering
D)narrow bandwidth

Question 16

__________     is undesired RF radiation.

A)intermodulation frequency
B)intermediate frequency
C)instantaneous frequency
D)instrumental frequency

Question 17

__________     is based on FDMA/FDD.

A)gsm
B)w-cdma
C)cordless telephone
D)amps

Question 18

In US AMPS, 416 channels are allocated to various operators with 10 kHz guard band and channel between them is 30 kHz. What is the spectrum allocation given to each operator?

A)12.5 khz
B)30 khz
C)12.5 mhz
D)30 mhz

Question 19

TDMA systems transmit in a continuous way.

Question 20

__________     are utilized to allow synchronization of the receivers between different slots and frames.

A)preamble
B)data
C)guard bits
D)trail bits

Question 21

Which of the following is not true for TDMA?

A)single carrier frequency for single user
B)discontinuous data transmission
C)no requirement of duplexers
D)high transmission rates

Question 22

Because of_________    transmissions in TDMA, the handoff process in_________          

A)continuous, complex
B)continuous, simple
C)discontinuous, complex
D)discontinuous, simple

Question 23

__________     synchronization overhead is required in TDMA due to_________     transmission.

A)high, burst
B)high, continuous
C)low, burst
D)no, burst

Question 24

TDMA allocates a single time per frame to different users.

Question 25

__________       of TDMA system is a measure of the percentage of transmitted data that contains information as opposed to providing overhead for the access scheme.

A)efficiency
B)figure of merit
C)signal to noise ratio
D)mean