Reconfigurable Intelligent Surfaces for Wideband Communications: Challenges and Possible Solutions

[@johnaweiss]

Fantastic explanation.

[@KawakebAstra]

🙏😎💫♥️i’m artist not techno engineer but this is important info ..everyone effected . .

[@nithinbabu4962]

Hi Professor, I have been following your tutorials on RIS and Podcasts! all are really great, helped a lot to bridge the gap between theory and practice, and many thanks to you. I have a doubt regarding the mechanism behind the variation of phases of the impinging signals using the patch element you explained at 19:33 of this video. From the theoretical explanation, we need to delay the impinging signals so as to add them constructively to the receiver; could you please clarify how this delay is achieved by changing the impedance of the reflecting element?

[@WirelessFuture]

The reflection coefficient captures the amplitude and phase change: en.m.wikipedia.org/wiki/Reflection_coefficient There are different ways to implement a varying delay (phase shift). It can be done mechanically by connecting the patch to transmission lines of different lengths, so that the signal needs to travel a different distance in the medium before being reflected. A more attractive way is to vary the impedance, which basically changes the speed of light in the medium. This is also known as the velocity factor: en.m.wikipedia.org/wiki/Velocity_factor

[@nithinbabu4962]

@@WirelessFuture Thanks a lot!

[@bereket4]

Thank you for your brief explanation. in this year I am going to conduct M.Sc. research on communication engineering. what topic would you suggest me?

[@WirelessFuture]

It is hard to give a general recommendation about that. I think the starting point should be what parts of communication engineering that you are good at, so you will get a chance to utilize that. Then it is important to identify a topic where you can get supervision at your university. Finally, it can of course be exciting to look for something that is related to 6G technology. You can have a look at the 6G white papers from Oulu, which cover many different directions: www.oulu.fi/6gflagship/6g-white-papers

[@bereket4]

@@WirelessFuture 🙏🙏

[@sachinkumar-nd3xx]

A very good insightful video on RIS thank you. I have completed my Masters in Communication systems and am looking forward to carry out research in 5g and Beyond , not able to get hold of which topic i should choose. can u please provide any suggestions on the topics

[@WirelessFuture]

Hi Sachin, there are many different research directions that are important for future networks. You can get a sense of it by looking at the following collection of white papers: www.oulu.fi/6gflagship/6g-white-papers As a new researcher, it might be good to pick a topic that isn’t too crowded with other researchers, because then you can spend less time on keeping up with the latest papers and more time on being creative. If you want to work on the RIS topic, I think he wideband case is the most important one to look into.

[@rahulsinghgulia6666]

Hi. Thank you for such a great tutorial on RIS. I would like to know if there is any Github profile for this work, so that we can reproduce these results and analyze the model ourselves.

[@WirelessFuture]

The simulation results can be reproduced using this code: github.com/emilbjornson/SPM_RIS However, the video also presents results from testbed experiments. Those cannot be reproduced numerically, but you can find more details here: arxiv.org/pdf/2103.00534.pdf

[@patrice9480]

Hello, thanks a lot, I have a question. There is a narrowband channel vector between TX/RIS and between RIS/RX but not between TX/RX, why ?

[@WirelessFuture]

Hi! On slide 12, we consider the case where the TX-RIS channel and RIS-RX channel consist of L_h and L_g distinct narrowband paths, respectively. These paths interact to create a wideband channel. We didn’t consider any TX-RX channel in this video, to keep it simple. But it can naturally be added. You can find all the details in the following paper: arxiv.org/pdf/2102.00742.pdf

[@hopemantube1219]

Hi professor, I've been following your tutorials and I'd like to ask about datasets about RIS. I'm currently enrolled in a PhD program and my research interests include the application of deep learning to RIS-assisted UAV communication. However, it is difficult to collect datasets in RIS. I would appreciate some help with creating datasets in RIS.

[@WirelessFuture]

Hi! I’m not aware of so many datasets, but here is one with measurements github.com/RUB-DCS/RIS-S21-Measurement-Dataset There are some datasets that were generated numerically. One example is the Signal Processing Cup 2021 dataset: github.com/emilbjornson/SP_Cup_2021 You can look at paperswithcode.com to see if you find something more.

[@hopemantube1219]

@@WirelessFuture Thank you very much!!

[@nelebauer7864]

Thank you. Interessting. Concerning the phase shift vector on slide 9, Omega. Why is this phase shift vector always given in that form (e to the power of j*Theta)? Why not only a vector with (Theta1, Theta2,...,ThetaN)^T? I think that would be easier. Has it to do with the complex expression?

[@WirelessFuture]

Yes, you can write it as a vector (Theta1, Theta2,...,ThetaN) but each entry must have unit magnitude, so that it doesn't amplify the signal, only incur a phase shift. That is why the solution must be a complex exponential function.

[@captainsam8465]

Thank you so much sir 🌷🌷..

[@saleemalmadrahi1912]

Sir , Can u tell me what is program that simulate the IRS and where can I find explaining about how to simulate it with rich information?? .. I will be thank you forever sir because it is my graduation project 🌷..

[@WirelessFuture]

Specialized programs could be used to simulate the electromagnetic propagation in fine detail, but I believe most researchers write their own simulation software using Matlab or Python. You can find examples on this GitHub page: github.com/emilbjornson?tab=repositories

[@captainsam8465]

@@WirelessFuture thank you sir for your ethicals

[@salehelbusaifi4880]

I need the effect of phase error and area of surface RIS for siso system

[@WirelessFuture]

You can check equation 32 in arxiv.org/pdf/2102.00742.pdf The second row is with optimal phase-shifts and the first row with arbitrary phase shifts, which could be suboptimally selected. The summation along with the physical size of each element determines the surface area.

[@salehelbusaifi4880]

@@WirelessFutureWhere is the Matlab program for this paper?

[@WirelessFuture]

There is no Matlab program. We might release code if/when the paper is published. Right now it is just a preprint.

[@whyzaghub4863]

Sir , please make lecture on under water acoustics

[@njininathanfofeyin7422]

I am a Telecom undergraduate student interested in 6G related Research. I would like to do personal projects in this domain to build my knowledge and skills but I am unsure how to start. How do you recommend I proceed Prof. Emil? Kind regards.

[@WirelessFuture]

To perform meaningful research, you need to have a deep understanding of the state-of-the-art and methods that can be utilized to improve it. As an undergraduate student, I would then focus on learning the theoretical tools (mathematics, programming, communication theory) that underpins the technology, and then practice on applying it at something 6G related in the thesis project. Remember that “all” other 6G researchers have a Master or PhD degree, so you will be at a disadvantage if you try to perform novel research before reaching the same level of knowledge.

[@njininathanfofeyin7422]

@@WirelessFuture I will likely do a Masters degree hereafter. For now, I will dedicate more time on the theoretical tools and foundational knowledge. Thank you.