1. Tutorial 3
Wireless and Mobile
Communication
SARDAR VALLABHBHAI NATIONAL INSTITUTE OF TECHNOLOGY
SURAT
2. Question 1
a) Sketch the Power Delay Profile of the channel in
dBm.
b) What is the local average power in dBm?
c) What is the rms delay spread of the channel?
( )=
=0
2
10
6
2
+1
( 10
6
)
3. Question 1 (continued)
d) If 256 QAM modulation having a bit rate of 2 Megabits per
second in applied to the channel, will the modulation
undergo flat or frequency selective fading? Explain your
answer.
e) Over what bandwidth will the channel appear to have
constant gain?
( )=
=0
2
10
6
2
+1
( 106
)
4. Question 2
A local spatial average of a power delay
profile is shown in Figure.
a) Determine the rms delay spread and
mean excess delay for the channel.
b) Determine the maximum excess
delay.
5. Question 2 (continued)
A local spatial average of a power delay profile is
shown in Figure.
c) If the channel is to be used with a
modulation that requires an equalizer
whenever the symbol duration T is less than
10 t determine the maxim RF symbol rate
that can be supported without requiring an
equalizer.
6. Question 2 (continued)
A local spatial average of a power delay
profile is shown in Figure.
d) If a mobile travelling at 30 km/h
receives a signal through the
channel, determine the time over
which the channel appears
stationary. Assume fc =900 MHz.
7. Question 3
What is the delay spread bound max of a 220 MHz radio
system if PT = 1 watt (+ 30 dBm) and PRmin = -90 dBm?
How much is max if sensitivity of the receiver is improved to
PRmin = -100 dBm? Why does increased sensitivity or
increased system gain, Gs = PT PRmin, lead to a higher delay
spread bound?
8. Question 4
Determine the proper spatial sampling interval required to make
small scale propagation measurement which assumes that
consecutive samples are highly correlated in time. How many
samples will be required over 10 m travel distance if Fc = 1900
MHz and v = 50 m/s? How long would it take to make these
measurements, assuming they could be done in real time from a
moving vehicle? What is the Doppler spread BD for the channel?
