Deck 17: Wireless Transmission Techniques

Question 1

In a MIMO scheme the transmitter employs a single antenna.

Answer 1

False

Question 2

A disadvantage of MU-MIMO is that the available capacity cannot be shared to meet time-varying demands.

Answer 2

False

Question 3

With __________ the same data is coded and transmitted through multiple antennas.

A)spatial multiplexing
B)CDMA
C)spatial diversity
D)SC-FDMA

Answer 3

C

Question 4

MIMO exploits the space dimension to improve wireless systems in terms of _________.

A)range
B)capacity
C)reliability
D)all of the above

Question 5

________ is used on the downlink channel to enable the base station to transmit different data streams to multiple users over the same frequency band.

A)OFDM
B)SC-FDMA
C)MIMO-BC
D)all of the above

Question 6

MIMO-MAC systems outperform point-to-point MIMO.

Question 7

__________ is when a source data stream is divided among the transmitting antennas.

A)SC-FDMA
B)Spatial multiplexing
C)OFDM
D)None of the above

Question 8

Orthogonal Frequency-Division Multiple Access employs multiple closely spaced subcarriers.

Question 9

MU-MIMO techniques are used in both Wi-Fi and 4G cellular networks.

Question 10

In a multipath scenario where each receiving antenna would experience a different interference environment,there is a high probability that if one antenna is suffering a high level of fading, another antenna has sufficient signal level.

Question 11

In OFDM all of the subcarriers are dedicated to a single data source.

Question 12

Subchannelization is not useful for battery-powered devices.

Question 13

Diverse multipath fading offers multiple views of the transmitted data at the receiver,thus increasing robustness.

Question 14

MIMO systems are characterized by the number of antennas at each end of the wireless channel.

Question 15

Together,MIMO and OFDM technologies are the cornerstone of emerging broadband wireless networks.

Question 16

________ is used on the uplink channel to provide multiple access to subscriber stations.

A)MIMO-MAC
B)MIMO-MU
C)MIMO-DS
D)MIMO-BC

Question 17

The IFFT operation has the effect of ensuring that the subcarriers do not interfere with each other.

Question 18

Spread spectrum is an important form of encoding for wireless communications.

Question 19

Spatial diversity can be used when transmitting conditions are favorable and for relatively short distances compared to spatial multiplexing.

Question 20

OFDM cannot overcome intersymbol interference in a multipath environment.

Question 21

The relationship among the subcarriers in the OFDM scheme is referred to as ________ .

A)modulation
B)subchannels
C)orthogonality
D)spread spectrum

Question 22

There are two applications of MU-MIMO: Uplink--Multiple Access Channel,MAC and __________.

Question 23

_________ antenna architecture has become a key technology in evolving high-speed wireless networks,including IEEE 802.11 Wi-Fi LANs and WiMAX.

Question 24

One prominent advantage of _______ over OFDMA is the lower peak-to-average power ration of the transmit waveform,which benefit the mobile user in terms of battery life and power efficiency.

A)PAPR
B)IFFT
C)FMDA
D)SC-FDMA

Question 25

________ defines subchannels that can be allocated to subscriber stations depending on their channel conditions and data requirements.

Question 26

For the IEEE 802.11a LAN standard,the OFDM scheme consists of a set of ______ subcarriers with a base frequency of 0.3125 MHz.

Question 27

_______ is a multiplexing technique used with spread spectrum.

Question 28

The two types of MIMO transmission schemes are spatial diversity and __________ .

Question 29

With ________ it is possible to simultaneously transmit either from or to different users by allocating the subcarriers during any one-time interval to multiple users.

A)OFDMA
B)SC-FDMA
C)SC-TDMA
D)all of the above

Question 30

Like OFDM,_______ employs multiple closely spaced subcarriers,but the subcarriers are divided into groups of subcarriers.

A)CDMA
B)IFFT
C)QPSK
D)OFDMA

Question 31

With __________ ,each bit in the original signal is represented by multiple bits in the transmitted signal,using a spreading code.

A)IFFT
B)DSSS
C)CDMA
D)FHSS

Question 32

__________ extends the basic MIMO concept to multiple endpoints,each with multiple antennas.

Question 33

FFT is a family of algorithms that form a special case of the __________ ,which refers to any algorithm that generates a quantized Fourier transform of a time-domain function.

A)DFT
B)IFT
C)IFFT
D)QPSK

Question 34

The ________ is an algorithm that converts a set of uniformly spaced data points from the time domain to the frequency domain.

Question 35

OFDMA subcarriers are divided into groups and each group is named a ______ .

A)chip
B)hop
C)subchannel
D)SCG

Question 36

_________ is a common modulation scheme used with OFDM.

A)QPSK
B)FFT
C)IFFT
D)ISI

Question 37

Subchannels are further grouped into ________,which can be allocated to wireless users.

A)links
B)chips
C)signals
D)bursts

Question 38

The ________ scheme uses advance digital signal processing techniques to distribute the data over multiple carriers at precise frequencies.

A)SC-FDMA
B)OFDM
C)OFDMA
D)CDMA

Question 39

The ________ reverses the FFT operation.

Question 40

_________,also called multicarrier modulation,uses multiple carrier signals at different frequencies,sending some of the bits on each channel.

Question 41

The essential idea of the ________ technique is to spread the information signal over a wider bandwidth to make jamming and interception more difficult.

Question 42

The signal processing for OFDM involves two functions known as fast Fourier transform and ______________ .

Question 43

The first type of spread spectrum developed is known as _________ .

Question 44

The earliest applications of ________ were military,where it was used for its immunity to jamming.

Question 45

SC-FDMA performs a _______ prior to the IFFT operation,which spreads the data symbols over all the subcarriers carrying information and produces a virtual single-carrier structure.