How is time/duration represented in Matlab?

[Antonio_Magma]

In my OFDM simulation, symbols consists of an array or bits..my guard interval is defined by the number of samples etc...

However, in practical, everything is in time (micros seconds, mili seconds). How do i relate the both of this?

 

[mayyan]

Re: Time in Matlab

I am not sure i underdstand your question but as far as i unserstand when you sample a signal there is where you make the conection. For example if you have a 10 seconds signal and you take 11 samples you sample in a 1 second intervals ( assuming even intervals).

 

[Antonio_Magma]

Re: Time in Matlab

Ok sorry, let me try again...

Lets say i want to design my symbol duration to be lets say 100 us long, and the guard interval is say 25 us long.

How is this duration represented in Matlab?

 

[joinfaisal]

Time in Matlab

I think the duration of guard intervel should be equal to the length of the channel Impulse response.

So let say if you represent your signal by vector let say a = [1 0 1 1 0 0 0 1 1 1 0] and say ur channel is like this h = [1 0.5 0.8] ... so length of ur channel is 3 so you will copy the last 3 bits and will put it in front of ur signal hence called cyclic prefix addition. I simulated ofdm like this long time ago and this is what I remember .. I think it shud be like this.. may be lets have suggestion by others members as well...

 

[Antonio_Magma]

Re: Time in Matlab

Well, thats not my question...

Lets say for your example:

Vector a = [1 0 1 1 0 0 0 1 1 1 0];

My question is, how long is the duration for this vector a? or any other OFDM symbol generated..what would be its time duration? how is it represented in matlab?

 

[bpu]

Time in Matlab

the time duration is not represent in matlab.
for example a = [1 0 1 1 0 0 0 1 1 1 0]; length(a) = 11;
sample time is 1us (for example)
summary: length of a is 11us

you can't say to matlab how to use your physical sample time. but you need to remember, than sample time is xx seconds at this vector. you need it, because you can change the sample time (for example, with the interpolation)

 

[joinfaisal]

Re: Time in Matlab

the time duration is not represent in matlab.
for example a = [1 0 1 1 0 0 0 1 1 1 0]; length(a) = 11;
sample time is 1us (for example)
summary: length of a is 11us

you can't say to matlab how to use your physical sample time. but you need to remember, than sample time is xx seconds at this vector. you need it, because you can change the sample time (for example, with the interpolation)

yeh.. right... that exactly what I meant...

 

[Antonio_Magma]

Time in Matlab

oh ok....i get it...i think..

 

[amraldo]

Re: Time in Matlab

Hello,
Matlab does not have any models of time.
You may build in ur time model by defining a vector for the sampled data & another one for the time.
Or use simulink instead where it uses a continous time model built on differential equations.
Regards,
amraldo.