What is Massive MIMO?

[@siddharthabhakta3261]

Only video I found on this subject which gives full engineering details. Just spot on. I loved it.

[@iain_explains]

I'm really glad to hear that you liked the content.

[@prabhatsahoo7535]

Very lucidly explained. Pros and Cons are nicely explained

[@iain_explains]

Thanks. I'm glad you liked it.

[@mandarmoksha]

Big fan of your work Lain... Thank you!

[@iain_explains]

That's great to hear. Glad you like the videos.

[@neelanjanasubinferdous8138]

Respected Sir, Thank You so much for such nice informative videos. Really very helpful.

[@iain_explains]

Thanks. Glad you like them.

[@王大維-w4t]

Thanks a lot! I’ve been waiting for this a while

[@iain_explains]

Glad I could help!

[@plastilinovbly]

Great video!

[@jainpakpoom]

Thank you for this video. All your videos have really been helpful and informative.

[@iain_explains]

I'm so glad!

[@한두혁]

Hello I have a question. In 1:25 you said that carrier freq and bandwidth are proportional & inverse proportionality of optimal radiating size. How can I understand this?

[@iain_explains]

It's complicated. My comment was a generalisation. Generally speaking, the lower frequencies propagate better in terrestrial communication systems, so they are more "in demand". The higher frequencies are less "in demand", and since there are fewer users, it's possible for them each to use wider bandwidths. Also it's harder to design "narrow band" band pass filters at higher carrier frequencies. To understand the relationship between the spacing of the antenna elements and the optimal energy transfer requires electromagnetic antenna theory.

[@한두혁]

@@iain_explains do you have any book recommendation?

[@prisharocks]

Amazing explanation! Well done 👍🏻

[@iain_explains]

Glad you liked it!

[@malini50]

Hi Sir! In Hybrid beam forming when you say x antennas have same theta(phase), how all three will transmit/receive at a time? already the beams are narrow. Please elaborate.

[@omar778]

Thanks

[@unrmaestro]

ty sir

[@pitmaler4439]

In dig. beamforming we have the RF chain after the processing, that's clear. Does that RFchain includes the FFT or IFFT? Or there just converters, filters, amplifiers,....? Thank you.

[@iain_explains]

Just converters, filters, amplifiers,....

[@nelsonmakeketa6188]

Good Stuff thanks you soo much sir had to refresh my knowledge.

[@iain_explains]

Glad to help.

[@joeb9907]

Atmospheric and moisture absorption goes up with frequency. This reduces the coherence bandwidth as well the range. Availability is reduced significantly. The trade becomes cell size reduction which increases the need for smaller cell size and more of them per service area. There is a practical limit as frequency used goes up and it is reached quickly as a function of RF frequency. Increased transmit power and or antenna gain does not overcome this as phase coherence is lost before SNR goes below minimum detectable signal levels. Antenna cross polarization/ depolarization at the antenna also is severly degraded due to droplet size of moisture within the field of regard of the antenna array and each formed beam. Remedies are non trivial. The design trades have to address this above 10 ghz to determine feasible system designs.

[@thijsherbold7996]

This video helped a lot, thanks!

[@iain_explains]

Glad it helped!

[@shahriarsowad9221]

Prof. Is there any particular book you will suggest to learn all the basics of MIMO communication ?

[@iain_explains]

This one is good: B. Clerckx and C. Oestges, "MIMO Wireless Networks: Channels, Techniques and Standards for Multi-Antenna, Multi-User and Multi-Cell Systems"

[@jeewithbanerjee1160]

Please cover reconfigurable intelligent surfaces

[@iain_explains]

Thanks for the suggestion. I've got it on my "to do" list.

[@mopol4400]

Hi doctor first thanks for all these information Mr i have a question witch is favorable propagation is when the channel responses from the base station to user terminals are mutually orthogonal ? what is mutually orthogonal?

[@iain_explains]

Mutually orthogonal means that all users are orthogonal to each other. Basically it means that the H matrix is invertable. This video may help: "What is Multi-User MIMO Communications (MU MIMO)?" kzbin.info/www/bejne/Zp_GeoqindioZ6M

[@wiseshouse8230]

hello sir thanks to your informative videos, but i got a question here, why is in some books they say the massive mimo is the systems focus on adding a much higher number of antennas on the base station,

[@iain_explains]

"Massive MIMO" is a very loose term. It gets used in quite a few situations. Basically any communication system where a large number of antenna elements are used at one or other end of the link (or both) gets called "massive MIMO". And there's no specific definition of "large number".

[@lakshmikandula634]

prof can you please explain how increment in carrier frequency leads to bandwidth increment ?

[@iain_explains]

It depends on what "bandwidth" you are referring to. I'll add this topic to my "to do" list for a future video.

[@lakshmikandula634]

@@iain_explainsthank you sir.

[@bouchibanefatmazohra1485]

It's helpfull..thanks a lot 😊

[@iain_explains]

Glad you found it useful.

[@wumeng8619]

Hi Prof! As MIMO requires rich scattering environment, does it mean that narrower beams from gNB with large N to UE with small M isn’t suitable for high rank transmissions as the effective BFed channel becomes sparse such that there is insufficient scatterers around the UE to decorrelate the channel? (TX correlation is assumed less problematic considering orthogonal beams to transmit multiple layers)

[@iain_explains]

Well, it depends on exactly what you mean by "MIMO". In the early days, "MIMO" was used to describe "spatial multiplexing", but these days it is much more general, and literally refers to any system with multiple transmit and multiple receive antennas (even if the receive antennas are each on a different user, as in MU-MIMO). You might like to watch: "What are Spatial Diversity and Spatial Multiplexing in MIMO?" kzbin.info/www/bejne/g3-kYaukbKqYr7s

[@wumeng8619]

@@iain_explains thanks a lot for your prompt reply! yes I have checked that one (and most of the others of your videos :-)) Here I meant spatial multiplexing for high rank transmission. Considering above dimension of e.g. N=32 and M=2, two beams carrying two layers respectively, would it be problematic with too large N such that the beams get too narrow yielding in the propagation channel too less scatterers around RX and making receive correlation too high for rank2 transmissions? You mentioned less "multi-path diversity", did you mean this increased correlation or frequency selectivity channel coding exploits?

[@iain_explains]

It all depends on the gain of the individual paths and their relative directions. The larger the number of antennas, the more accurately the paths can be resolved, and the more power that gets directed in those specific directions. In terms of the number of data streams (or "layers"), just because you might only have two data streams, doesn't mean you only use two of the available "paths" in the channel. The "effective beams" that get formed for each data stream can be "multi-fingered".

[@TejasGaga]

Respected Sir, Very good video.. very informative....Kindly make one video on Modelling Massive MIMO mathematically as compared to MIMO modelling Like y=Hx+n in case of MIMO.(Request)

[@iain_explains]

Thanks for the suggestion. I'll add it to the list.

[@Oshea73]

wow very nice channel

[@iain_explains]

Thanks and welcome

[@lancecruwys2177]

I'm probably confused here but don't we want reduced multipath diversity as that would cause more distortion the higher it is?

[@iain_explains]

It depends on whether you can use the diversity to your advantage. If you are not using it, then it will look like distortion, and be a problem for you. But if you are doing cleaver signal processing, then you can make use of it, and it's not "distortion". This video might help: "What are Spatial Diversity and Spatial Multiplexing in MIMO?" kzbin.info/www/bejne/g3-kYaukbKqYr7s

[@lancecruwys2177]

@@iain_explains Thank you for all your videos. I find signals and comm theory to be both the most challenging and interesting of the EE field, and your videos have been exceptionally useful. Also it's nice that they're free. Thank you again!

[@iain_explains]

Thanks for your nice comment. I'm so glad that you have found the videos helpful.

[@sabertooth21]

This channel is only for professors i guess coz I'm not able to understand a single term from it😭😭

[@iain_explains]

Well yes, some of the videos do assume a certain level of prior knowledge. But many/most of the videos are intended for beginners/interested people. You might like to check out some of the Playlists on the channel, or go to the following website and take a look at the topics listed in categorised order (from most basic/introductory, to more advanced): iaincollings.com

[@sabertooth21]

@@iain_explains Thank you sir