Continue to Site

# spectral efficiency calculation from eye diagram

Status
Not open for further replies.

#### seraphin

##### Newbie level 3
how to calculate the spectral efficiency from eye diagram in simulink software?

The spectral efficiency is defined as (information rate/bandwidth) [bit/sec/Hz]
you cannot calculate it from the eye diagram - the eye diagram simply shows you the progression of the transmitted symbols through time.

seraphin

### seraphin

Points: 2
thank u......... is it possible to calculate ber from eye diagram and using that can i analyse the spectral efficiency of the system?????
can u explain in detail pls.....

Well no.

remember the eye diagram is simply a descriptive graphical view of the transmitted symbols through the channel. The calculate the BER you either need to demodulate the received samples y[0],y[1],.. yourself and compare the the given transmitted signal x[0],x[1],... (if you have it).

About the sepctral efficiency - again, this is not a factor you can take from the eye diagram. It is a parameter which for a continuous time channel will be calculated according to
information bit rate/bandwidth.

seraphin

### seraphin

Points: 2
Eye diagram (for baseband transmission) shows how many levels the transmission has and hence the bits/symbol of the system.
If you know the shaping of the transmission,

spectral_efficiency [bits/s/Hz] = symbol_efficiency [bits/symbol] / spectral_occupancy [Hz / (symbol/s)]

For instance, if the eye pattern of a baseband NRZ transmission has 4 levels, you have a symbol_efficiency of 2 bits/symbol; if it would use minimum bandwidth (i.e. strctly limited to 1/(2T)) meaning spectral_occupancy of 0.5 Hz/(symbol/s), then the spectral efficiency would be 1 bits/s/Hz. Other shaping (e.g. raised-cosine with roll-off factor > 0) increases spactral occupancy and decreases spectral efficiency.

Sometimes, the term "eye diagram" is used instead of "constellation diagram" for passband APSK transmission. In this case, the relationships are the same but you must consider the number of points instead of the number of levels, and the fact that the spectrum is two-sided around the carrier.

Regards

Z

seraphin

### seraphin

Points: 2
Well, basically it may be right - just one thing left forgotten:
The spectral efficiency relates to the information bits, therefore if the eye diagram describes a coded system, one has to know the code rate in order to calculate the spectral efficiency in this way.
If the system is uncoded, then the above is true. If it is coded and the code rate is unknown, then the eye diagram simply describes a set of coded symbols.

seraphin

### seraphin

Points: 2
I m working on spectral efficiency analysis of hybrid ocdma/wdma system...... is there any other means of analysing the spectral efficiency??

I don't really know these systems specifically. Maybe there are other means, you have to check literature.

I m working on spectral efficiency analysis of hybrid ocdma/wdma system...... is there any other means of analysing the spectral efficiency??

ocdma/wdma are not my area, but I suppose that the number of users must be taken in consideration, and the coding scheme as well.
I might be very wrong, but I guess that you are interested in the spectral efficiency of the whole system and not of a single user. Right?

Z

Status
Not open for further replies.