OUTAGE PROBABILITY
In a fading radio channel, it is likely that a transmitted signal will suffer deep fades that can lead
a complete loss of the signal or outage of the signal. The outage probability is a measure of the
quality of the transmission in a mobile radio channel. Outage is said to occur when the received
signal power goes below a certain threshold level [3,4]. It can be calculated as the integral of the
received signal power p(t) as
Pth
Ρout = ∫P(dt)
0
where Pth is the threshold power.
The concept of outage can be demonstrated with MATLAB using the results from the previous
Section. The procedure to find the outage probability is as follows:
1. Calculate the received signal power as given in equation
2. Set a threshold power level for the received signal relative to the average signal power.
3. Count the number of times in the sample interval that the received signal power goes below
this threshold.
4. Using the basic concept of probability, the outage is then calculated by taking the ratio of the
count in step 3 to the total number of samples.
For one received signal, we calculated the outage probabilities for various thresholds, and
compared these values to those calculated analytically. The outage probabilities calculated
analytically and through simulations were found to tally quite well. Fig.6 shows the curves for
the outage probability, calculated analytically and through simulations, for the Rayleigh fading
case. As observed from Table I, the outage probability (averaged over 50 simulations) in a
Rician channel is lower than that in a Rayleigh channel, which can be attributed to the presence
of a line-of-sight path. Moreover, the probability of outage increases as the mobile velocity, or
resulting Doppler shift, increases.
In a fading radio channel, it is likely that a transmitted signal will suffer deep fades that can lead
a complete loss of the signal or outage of the signal. The outage probability is a measure of the
quality of the transmission in a mobile radio channel. Outage is said to occur when the received
signal power goes below a certain threshold level [3,4]. It can be calculated as the integral of the
received signal power p(t) as
Pth
Ρout = ∫P(dt)
0
where Pth is the threshold power.
The concept of outage can be demonstrated with MATLAB using the results from the previous
Section. The procedure to find the outage probability is as follows:
1. Calculate the received signal power as given in equation
2. Set a threshold power level for the received signal relative to the average signal power.
3. Count the number of times in the sample interval that the received signal power goes below
this threshold.
4. Using the basic concept of probability, the outage is then calculated by taking the ratio of the
count in step 3 to the total number of samples.
For one received signal, we calculated the outage probabilities for various thresholds, and
compared these values to those calculated analytically. The outage probabilities calculated
analytically and through simulations were found to tally quite well. Fig.6 shows the curves for
the outage probability, calculated analytically and through simulations, for the Rayleigh fading
case. As observed from Table I, the outage probability (averaged over 50 simulations) in a
Rician channel is lower than that in a Rayleigh channel, which can be attributed to the presence
of a line-of-sight path. Moreover, the probability of outage increases as the mobile velocity, or
resulting Doppler shift, increases.
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