What is the Outage Probability and why we use it?

[saeddawoud]

Hello,

When do we use the "outage probability" as the only performance metric in a communication system?

Thanks in advance

 

[aliazmat]

Re: Outage Probability

when a channel is slow fading, than it is considered as random and hence the capacity

C= log2(1+h.^2 SNR)

is also random , it mean no constant rate is available

in this situation we use outage probability which simply mean what is the probability that a given rate will not be supported because of channel variations

 

[saeddawoud]

Re: Outage Probability

In fact I didn't get it. Can you explain in more details, please.

 

[m_pourfathi]

Re: Outage Probability

In fading channels, the received signal has no constant power which be depending on the channel, can be described by probability models. Thus, signal to noise ratio will also becomes a random variable. and Thus the maximum capacity of the channel becomes a random variable. Outage probability says according to the variable signal to noise ratio at the received end, what is the probability that a rate is not supported due to variable signal to noise raito.

 

[saeddawoud]

Re: Outage Probability

ok fine, I know what outage probability means. But, while I am reading, I noticed some papers use the outage probability as the only performance metric, i.e.: no BER or SER combined with it. The question was: what is the situation(s) we use the outage probability as the only performance metric?

Regards

 

[m_pourfathi]

Re: Outage Probability

They are different aspects of performance metric. BER is the performance of the receiver, but outage probability is a metric for the channel. the latter talks about the capacity or throughput of data that can be transmitted through the channel due to noise and fading assuming to have a low-level margin for signal to noise ratio.
Bit error rate is something else. for a channel with the same outage probability we might have different BERs for two different receivers.

 

[changfa]

Re: Outage Probability

Outage probability is a crude measure of performance. It is defined as the probability when mutual information is less than the given threshold.

The importance of outage probability is that when outage occurs, there is more likely to have decoding failure. In other words, it is a typical error.

 

[azi_hekmat]

Re: Outage Probability

Hi

you say that chanel capacity is random because of fading so we define outage probability . However without fading, noise was a random variable as well. why we did not define outage probability in that situation?

thanks
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