1. Signal will distort if transmitted signal bandwidth is greater than bandwidth of __________
a) Receiver
b) Radio channel
c) Multipath channel
d) Transceiver
Explanation: Received signal will be distorted if transmitted signal bandwidth is greater than bandwidth of multipath channel. But received signal strength will not fade much over a local area
2. What is a measure of the maximum frequency difference for which signals are strongly correlated in amplitude?
a) Coherence bandwidth
b) Narrow bandwidth
c) Incoherent bandwidth
d) Wide bandwidth
Explanation: The bandwidth of the channel can be quantified by the coherence bandwidth. It is related to the specific multipath structure of channel. It is a measure of maximum frequency difference for which signals are strongly correlated in amplitude.
3. The Doppler shift for mobile moving with constant velocity, v is given by _______
a) (v*cos θ)/λ
b) v/λ
c) v*cos θ
d) v*λ
Explanation: Doppler shift is given by (v*cos θ)/λ. This formula relates the Doppler shift to the mobile velocity and spatial angle between the direction of motion of mobile and the direction of arrival of the wave.
4. Doppler shift is positive if mobile is moving away from direction of arrival of the wave.
a) True
b) False
Explanation: Doppler shift is positive if the mobile is moving toward the direction of arrival of the wave, as the apparent received frequency is increased. And if the mobile is moving away from the direction of arrival of the wave, Doppler shift is negative.
5. Small scale variations of a mobile radio signal are directly related to _______
a) Impulse response of mobile radio channel
b) Impulse response of base station
c) Frequency response of antenna
d) Frequency response of base station
Explanation:The small scale variations of a mobile radio signal can be directly related to the impulse response of mobile radio channel. he impulse response is a wideband channel characterization and contains all information necessary to simulate or analyze any type of radio transmission through the channel.
6. Impulse response is a narrowband characterization.
a) True
b) False
Explanation: Impulse response is a wideband channel characterization. It contains all information necessary to simulate or analyse any type of radio transmission through the channel.
7. Mobile radio channel can be modelled as a ______ filter.
a) Non-linear
b) Low-pass
c) Linear
d) Bandpass
Explanation: Mobile radio channel may be modelled as a linear filter with a time varying impulse response. The time variation is due to receiver motion in space. The filtering nature is caused by summation of amplitudes and delays of multiple arriving waves at any instant of time.
8. Impulse response does not play any role in characterization of the channel.
a) True
b) False
Explanation: Impulse response is a useful characterization of channel. It may be used to predict and compare the performance of different mobile communication systems and transmission bandwidth for a particular mobile channel condition
9. Received signal can be expressed as ______ of transmitted signal with channel impulse response.
a) Addition
b) Subtraction
c) Division
d) Convolution
Explanation: The received signal y(t) can be expressed as a convolution of transmitted signal x(t) with impulse response of mobile radio channel. The variable t represents the time variations due to motion and the channel impulse multipath delay for fixed value of t.
10. Discretization of multipath delay axis of impulse response into equal time delay segments is called __________
a) Excess delay bins
b) Delay bins
c) Discrete bins
d) Digital bins
Explanation: It is useful to discretize the multipath delay axis of the impulse response into equal time delay segments called excess delay bins. The technique of quantizing the delay bins determines the time delay resolution of the channel model.