If someone is interested in how random orientation affects the bit-error rate (BER) of optical wireless communications, please see the following paper:

https://ieeexplore.ieee.org/abstract/document/8673906

Tb/s for indoor communications has been confirmed in the papers below via optical links:

https://ieeexplore.ieee.org/abstract/document/9217158

https://ieeexplore.ieee.org/abstract/document/9217368

Mr. Soltani

What is your opinion about optical code division multiple access(OCDMA) as research field?

Dear @Mohanad Alayedi,

I would say it is a quite well-matured subject in the optical fiber which was initiated by the work of Javad Salehi, see the following paper: https://ieeexplore.ieee.org/abstract/document/31181.

It has been considered in optical wireless as well, but maybe there is still some room to improve it. For example, how does it work with consideration of random orientation and mobility?

Please see the following papers for orientation and mobility models in optical wireless:

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8540452

https://ieeexplore.ieee.org/abstract/document/9145333

An OFDM-based optical wireless communication has been studied in the following paper:

https://ieeexplore.ieee.org/abstract/document/8732694

Maybe you can get some ideas from it.

Dear Soltani,

I appreciate you for creating this kind of open discussion.

I have few questions related to VLC as follows.

1) There is a lot of paper available for the implemetation of OFDM in VLC. There are discussions about ACO.DOC, Hybrid OFDM ( for converting complex domain to real and spectral eficiency), and a few more papers about impairments (like PAPR, clipping noise), recently OTFS was also implemented. But I have one question ( in VLC, IM/ DDswitching LED carries information. Will it take all the subcarriers at that particular instant (single LED) like in RF subcarriers maintains orthogonality. Can you explain this to me in this regard?

2) How can we model MIMO channel statistics in VLC ( with reference to your work modeling of Device orientation in LIFI systems and further extension work in measurement-based channel models)? As far as I know, it will be non-trivial, do you have any other suggestions.

Dear Murala Laxmi Naresh Kumar ,

Regarding your first question, yes, there are plenty of papers about OFDM in the optical domain, both optical fiber and optical wireless communications. Each OFDM block includes N subcarriers, where only N/2 -1 of them carry information.

Regarding your second question, there is a published paper that has considered the statistics of the channel including random orientation, in a MIMO system. Yes, it is not straightforward. But if you have any questions regarding this paper, I would be more than happy to help.

Here is the link for that paper:

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8790655

I hope you find this reply helpful.

Dear Omid M Kandelusy,

Actually, the first photophone (Alexander Graham Bell's invention) was based on this idea.

His photophone worked by projecting voice through an instrument toward a mirror. Vibrations in the voice caused oscillations in the shape of the mirror. Bell directed sunlight into the mirror, which captured and projected the mirror's oscillations toward a receiving mirror, where the signals were transformed back into sound at the receiving end of the projection.

This was the first wireless communications device.

I am not sure still anyone using this for indoor or outdoor communication. But one major challenge would be the modulation bandwidth.

A newly published paper on the channel gain modeling of OWC:

A novel realistic and measurement-based channel model for indoor OWC systems where the statistics of the channel gain are derived for the case of randomly oriented stationary and mobile users:

https://ieeexplore.ieee.org/abstract/document/9239914