Software Defined Radio and OFDM

applications of ofdm in sdr

I am planning to perform a research on OFDM which is widely used in Software Defined Radio. Nevertheless i am confuse on which part of OFDM or SDR i should concentrate on as there are a few of OFDM disadvantages (wikipedia) but there are also a lot of solution to it. I am curious to know which direction i should go.

I have the following idea in mind:
Building an algorithm for Intercarrier interference reduction/mitigation/avoidance/detection.
Analyzing the system performance between different OFDM technique (W-OFDM etc)

p/s i am interesting to do some research on MAC layer.
Hope someone can help me up.

Please advice.
Sincerely,
Allysonsim

software defined radios in ofdm

Hi, If I were you I would look at CSS (Chirp Spread Spectrum) Technology, it is much more robust and offers the same throughput does not have linearity problems etc..

software efined radio ofdm

Paul,

Thanks for the suggestion. I will look into it as soon as possible and will let you know the feedback alright

how to do ofdm on software radio

I don't know why you suggest CSS over OFDM for software defined radio although it has so many advantages and there are a lot of research are still on on this topic. Meaning there's a way to improve the technology.

Advantages of OFDM
* Can easily adapt to severe channel conditions without complex equalization
* Robust against narrow-band co-channel interference
* Robust against Intersymbol interference (ISI) and fading caused by multipath propagation
* High spectral efficiency
* Efficient implementation using FFT
* Low sensitivity to time synchronization errors
* Tuned sub-channel receiver filters are not required (unlike conventional FDM)
* Facilitates Single Frequency Networks, i.e. transmitter macrodiversity.

I did some study and get to know that there are some advantage of CSS which are the linearity, the doppler immunity, robust and so on...

But i am still confuse if i should choose this as a title for my research.. like "the implemenation of CSS in software defined radio" is it so?

Please advice.

ofdm software defined radio

Advantages of CSS
* NO equalization needed
* Immume against narrow-band co-channel interference
* Immume against multipath propagation
* Immume against doppler
* High energy efficient (specially good for mobile applications)
* Efficient implementation using dispersive SAW filter
* Low sensitivity to time synchronization errors

* Uses PA's in Saturated mode, most efficient operation !.

will the css reduces the multipaths

yeah.. you are right..
I will work more on that and will definitely update you with my progress..

thanks a lot dude....

ofdm energy efficiency

Because of past project work in both domains I understand that there are some shortcomings of OFDM as specified in standards but also interesting new solutions. CSS could be used as an modulation extension of OFDM. Or say it in other words; a chirp signal is a OFDM symbol. So you can preserve the equalisation efficiency and get some further improvements.

To my understanding OFDM works good in high S/N links conditions. But below 3dB other techniques should be applied. The PA efficiency or distortion robustness is only a continuous extension of multicarrier QPSK/BPSK on the scale of tradeoff Bit/s/Hz versus linearity.


Advantages of CSS
* NO equalization needed
wrong!! multipath reduce S/N, multifinger equalizer required for best perfomance
* Immume against narrow-band co-channel interference
only by the processing gain, adaptive OFDM could be infinite better or at least by windowing filter rolloff
* Immume against multipath propagation
wrong!! I think the meaning is narrow band fading, yes every broadband improves here and does not need excessive links margins
* Immume against doppler
very high, true, translate into timing difference, could important in >100GHz om systems
* High energy efficient (specially good for mobile applications)
true
* Efficient implementation using dispersive SAW filter
yes but programmability is lost, digital submicron implementation would outperform also energy efficiency
* Low sensitivity to time synchronization errors
OFDM also

* Uses PA's in Saturated mode, most efficient operation !.
But OFDM have a trade scale 64QAM-3/4 need more linearity than QPSK-1/2