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ECEN 310 - Communications Engineering
Tutorial 5
1) The local average power delay profile in a particular environment is found to be
2
X
10−6
−6
δ
t
−
n10
P (τ ) =
n2 + 1
n=0
a)
b)
c)
d)
Sketch the power delay profile of the channel in dBm?
What is the average power in dBm?
What is the rms delay spread of the channel?
If 256 QAM modulation having a bit rate of 2 Mbps is applied to the channel, will the signal
undergo flat or frequency selective fading? Assume a raised cosine pulse with 100% excess
bandwidth. Explain your answer.
e) Over what bandwidth will the channel appear to have constant gain? Give your answer for
both 50% and 90% correlation.
solution:
2
3
2) A transmitter provides 15 W to an antenna having 12 dB gain. The receiver antenna has a gain of 3
dB and the receiver bandwidth is 30 kHz. If the receiver system noise figure is 8 dB and the carrier
frequency is 1800 MHz, find the maximum Tx-Rx separation that will ensure a SNR of 20 dB is
provided 95% of the time. Assume n=4, σ = 8 dB and d0 =1 km.
Solution:
4
5
3) Four received power measurements were taken at distances of 100 m, 200 m, 1 km, and 2 km from
a transmitter. The measured values at these distances are −0 dBm, −25 dBm, −35 dBm, and −38
dBm, respectively. It is assumed that the path loss for these measurements follows the model
d
¯
¯
+ Xσ
Pr (d)[dBm] = Pr (d) + Xσ = Pr (d0 ) − 10n log
d0
where d0 = 100 m.
a) Find the minimum mean square error (MMSE) estimate for the path loss exponent, n.
b) Calculate the standard deviation of shadowing about the mean value.
c) Estimate the received power at d = 2 km using the resulting model.
d) Predict the likelihood that the received signal level at 2 km will be greater than 35 dBm.
Express your answer as a Q-function.
Solution:
6
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4) For the power delay profiles in Figure below, estimate the 90% correlation and 50% correlation
coherence bandwidths.
Solution:
file:///C:/Users/dmochopa/Desktop/getfile%20(1).gif
18-Sep-12