Probability of error versus Probability of bit error

[rvereza]

I dont think you can even decode a bit with SINR = -20 dB.

[pulkit]

I agree with your point, that 0.5 limit does not applies everywhere, that’s I mentioned it is for BSC and if receiver knows all about the nature of the channel. So it more of a theoretical concept.
But if we know BER is let say 0.7, then we can definitely say not all bits are in error.
That’s the meaning of probability.

[RFSpecialist]

So how come ber is just up to 0.5?
You have never seen a ber of 0.8?

[pulkit]

@pulkit

As the number system is binary here , so we have either 0 or 1. For our communication system we mostly assume it as BSC(Binary Symmetric Channel) which means probability of transmitting 0 and 1 is equal and equal to 0.5 (=1/2).
Assume we have to transmit 10(ten) bits all zeros and assume probability of bit error is 0.7, that means I will receive 7 1s and 3 zeros.
In that case , on the receiver we can decide to decode ones as zeros and zeros as ones, that way I will receive 7 zeros and 3 ones and in that case probability of bit error is 0.3.
So this is how probability of bit error is 0 to 0.5.

In this scenario.
But we can’t ensure all these assumptions in practical cellular communication systems.

[RFSpecialist]

There’s too much theory.
We should stay close to real life situations.
And in real life ber goes from 0 to 1 not from 0 to 0.5.

[pulkit]

But how can one understands real life situation without understanding theory?

[Tech_Playon]

When people decide SoC they even consider 0.01 ber.
Where as Radio planner are even ok with 5~10% BER also.

[RFSpecialist]

@pulkit

But how can one understands real life situation without understanding theory?

I don’t know what theory you study with ber max value 0.5
If I transmit 10 bits and all 10 bist are received in error how can you claim that ber is max 0.5?

[pulkit]

I haven’t said ber max value is 0.5 for practical systems, for a case that I mentioned where receiver can be designed to know all about the channel and binary bits are transmitted, that’s the case that I mentioned.

[RFSpecialist]

Your case does not cover all real life situations.
So make a theory that covers all real life situations.

[pulkit]

@RFSpecialist

If I transmit 10 bits and all 10 bist are received in error how can you claim that ber is max 0.5?

Apriori probability of bit error should also be mentioned here.

@RFSpecialist

Your case does not cover all real life situations.

I addressed whatever the doubt was asked.

@RFSpecialist

So make a theory that covers all real life situations.

I haven’t made these theories . Also one theory can not cover all real life problems.

[RFSpecialist]

We both stated our opinion about ber range.

[pulkit]

Indeed, good discussion.
Thanks

[baghdady.youssefrawy]

I agree with @RFSpecialist regarding BSC.
Because I am using LDPC decoder Belief Propagation algorithm and this algorithm used BSC case for that.
So, the process it computes probability of bit error.