Which BER do we evaluate when checking system performance?

[saeddawoud]

hello
when evaluating the performance of a digital communication system, are we evaluate the the BER at the output of the detector or BER at the output of the channel encoder??
Regards

 

[amihomo]

System Performane

I think BER at the output of the decision block is used as a performance measure.
but at the same time we can talk about the performance of the channel encoder and calculate the error rate at the output of the channel decoder.

 

[changfa]

Re: System Performane

This is really up to your needs.

If you focus on uncoded systems, you just look at the BER out of detector. For example, when you design a space-time code and want to see how much diversity the code can achieve, you look at uncoded BER.

If you study certain kind of channel code, Turbo code, LDPC, etc., you need to know how close your code is close to some limit, say the Shannon limit. Now you need to look at coded BER.

In practical systems, all are coded. However, in practice, at the receiver we have no access to the BER (otherwise you know the transmitting message already) and we usually measure the block error rate (BLER) through checking CRC code.

 

[albakri77]

Please i want know which kind of detector give us min. probability of error in communication system .and thanks