I am trying to implement VLC communication using non-coherent source (i.e. LED) using OFDM with direct detection. so my question are following:
Is it possible to use 16QAM-OFDM with direct detection using LED as carrier generator..?
The transmitter and receiver is working fine for back to back connection. I mean the electrical OFDM signal can be demodulated properly using laser and fiber link. But when I use LED source with free space optical channel the BER becomes very high of the order of 0.5 which is far higher than expected.
There might be wrong while assuming the parameters of the LED, FSO channel and PIN Photodetector.
I want to know what are the parameters that are affected and need optimization when the source becomes wide linewidth i.e. non-coherent carrier such as LED with 50 nm linewidth.
Hi Dhiman,
you know, that is a good question you asked. For my point of view, if in the first configuration (setting link: laser+fiber link+photodiode) you have good results with 16QAM OFDM, this means that your channel link is favorable for the bandwidth of your transmitted signal. in the case of the LED and FSO link transmission, as the photodiode is the same, I think that your channel is changed because of the LED bandwidth and the FSO transfer function too. Don't Miss also the emitted powers in both configurations which are not the same for each (fiber link or FSO) behavior.
hope that this will help you.
best,
Hi Sanya,
I agree with you, further i decreased the bit rate to 100 Mbps which was 62 Gbps in previous case. So, am trying to find the solution for these parameters as you mentioned.
I would guess most likely the limitation is in time constant of the LED
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