Massive MIMO for 5G below 6 GHz

[@任志恒-z1u]

This guy is really an expert on 5G

[@SureshChandraMannava]

Excellent lecture on MIMO & 5G

[@bsd1977]

Excellent lecture! Thanks for putting this up online. Much appreciated

[@dpc80]

excelent speeach and presentation in a very clear way!

[@jfma1763]

Regarding the two tiers of network at 3:48 of the video, it seems the beamforming is much more for Hotspot tier by directing the radio wave into one narrow beam than Coverage tier which basically requires a flat or uniform wide beam over a large area. One may say that the formed narrow beam would scan around a large area, then what about simultaneous useage demand from all directions in that large area?

[@WirelessFuture]

JF Ma Each user in the coverage tier only requires that its data signal is received stronged at the location where the user is. That is what beamforming can achieve. In the coverage tier, you can also have very many users so spatial multiplexing of users can be applied. Hence, beamforming is very important in the coverage tier as well.

[@jfma1763]

Hi, thanks for the answer. Do you mean beam scanning to different users by saying spatial multiplexing? Sort of beam hopping? If that is true, it is not the simultaneous coverage I initially asked about. No doubt that with beaming forming you achieve high spectral efficiency, reduce network interference, and network capacity. But on coverage tie, I still don't see it helps. Suppose a football stadium packed with thousands of people, and there is one dedicated base station serving all of them. In order for each person get uninterrupted high speed connection at the same time, would the base station form thousands of beams simultaneously? Furthermore, if each user would get one dedicated beam, interference would be a big problem for two users sit next to each other, because the beam would not be that narrow. Maybe i am missing something here.

[@WirelessFuture]

JF Ma You can make the beams as narrow as you like by deploying more antennas. You need roughly 5 times more antennas than users that you want to serve at the same time. So that would mean 5000 antennas if you want to spatially multiplex 1000 users in a stadium. One thing to bear in mind is that IP traffic is bursty so even if you want to serve 1000 users it is a much smaller number of users that have data to receive at the same millisecond. These things have been studied for 30 years. You can read the free book at massivemimobook.com if you want to understand the details.

[@faraharabian4153]

Great! thanks for all these free perfect videos!

[@luannaabreu731]

Hello Sir, According to the definition of the concept of ERB coverage area (gNodeB) when using narrow beam pointing generated by MIMO antenna in beamforming (BF) mode: Pointing a narrow beam covers, at maximum gain (up to 3 dB below), a relatively small area around the UE reference point (or UE cluster). How, therefore, is the concept of the coverage area of an ERB, and its correlate, the percentage of coverage area (a statistical parameter that considers the effect of log-normal multipath shading and weights its effects in an area around the ERB)? When considering the multi-user MIMO mode, with multiple narrow beams... The coverage area of an ERB would be defined considering all the beams pointed at different points in the surrounding area, or for each beam, is an area or sub-area of coverage defined? In the previous question, the starting point of view was what happens in the vertical plane that contains the ERB and UE antennas. There is also a concern with what happens in the signal distribution in the horizontal plane. In previous generations, a fundamental related concept is the division of the coverage area by sectors, something that was directly related to the beamwidth of the ERB antennas. For example, using 120º beam antennas, 3 antennas covered the 360º that would characterize the entire area. With multiple beams, one can imagine maintaining this concept and expanding the number of sectors. For example, with widths of 10 degrees per beam, horizontally, 36 would be needed to cover the entire area. From the above, I ask: the concept of the coverage sector remains in 5G, adapted to the multiple beams of the antennas MIMO? Given the considerable (apparently) change in planning: do the concepts of coverage area and percentage of coverage area remain essential for planning? What other related concepts came to be used? On 4G, are they already used? Given the complexity of using and coordinating multiple beams: in which scenarios and application conditions, will the MIMO strategy with multiple beams be used? The macro scenario is extreme broadband, communication ultra-reliable, or massive communication for multiple users? Is the environment outdoors, indoors, or both? Is the band sub-6 GHz or millimeter wave? Still on the previous question, in the scenarios foreseen for using MIMO with multiple beams, another question arises. In which of these beamforming scenarios will be “fixed” and in which will it be adaptive (following a cluster of users, with or without the interposition of nulls of the radiation pattern in the directions of other groups considered interference for that cluster)? Finally, considering all the different aspects of previous generations brought by the multi-user (multibeam) MIMO approach of 5G discussed here…. How has the link budget analysis been (or needs to be) adapted to address these aspects? Best Regards!

[@James-ie5em]

So anyone researching this ott technology will not be allowed to comment negatively. Because this tech is so incredibly safe and can never be used to harm people. Why on earth would you not allow comments. Its a discussion that's being avoided. And for good reason.

[@WirelessFuture]

It is perfectly alright to comment negatively, as long as the comment is connected to the video and there is a good tone. As far as I can see, we haven’t removed any comments from you.

[@yasserothman4023]

Does channel hardening hold for correlated fading channels ? When does channel hardening do not hold for massive mimo systems ? @28:10 Sorry but I didn't get how can massive mimo help in the process of user scheduling and resource allocation compared to conventional mimo systems ?

[@WirelessFuture]

Channel hardening is not an “all or nothing” concept, but there is a range between no hardening to a lot of hardening. Correlated fading reduces the channel hardening effect. Maybe 100 antennas with correlated fading achieves the same channel hardening effect as having 30 antennas with entirely uncorrelated fading. Chapter 2 in my book “Massive MIMO networks” explains this in detail: massivemimobook.com When it comes to scheduling: When the channels are equally good on all subcarriers, the need and benefit from scheduling users in time or frequency based on instantaneous channel knowledge disappear. You can schedule users whenever they need service. The only thing that limits how many users you can serve simultaneously is the number of antennas.

[@yasserothman4023]

@@WirelessFuture may I know why does correlation in the first place reduces the channel hardening effect ?

[@WirelessFuture]

@@yasserothman4023 Channel hardening is a type of spatial diversity, where the random fluctuations disappear when you have multiple independent fading variables. If you make an eigenvalue decomposition of the spatial correlation matrix of correlated channel, then you will find that some eigenvalues are large and some are small. The large ones will create channel hardening while the small ones have little or no impact. So with correlated fading, you might have 100 antennas but only 30 dimensions of randomness that is shared between them.

[@yasserothman4023]

@@WirelessFuture Thanks for your feedback may I know how did you generate the plot on the left hand side in MATLAB @26:49 bec I guess what is on the y axis is the average channel gain ?

[@WirelessFuture]

@@yasserothman4023 No, the curve shows the variations in the channel gain for different channel realizations. There is no average being computed. But you can see that the upper curve is almost constant, which is a way to observe channel hardening.

[@graziellebonaldoteixeira4565]

Very powerfull content. Thank you very much.

[@niravpatel3961]

Sir where is MATLAB simulation code for the same results? kindly share link

[@WirelessFuture]

All my simulation code is available at github.com/emilbjornson/ Is there a particular result in this video that you are interested in?

[@MrPuulkit]

In channel hardening, is it only the mean taken for all the channels or any other process?

[@WirelessFuture]

I’m not sure if I understood your question. Channel hardening appears when you take a fading channel with many dimensions (antennas) and apply beamforming that is matched to the channel. The fading variations will then average out thanks to the beamforming and we get an almost constant channel quality.

[@amahbubul85]

@@WirelessFuture So, we cannot achive channel hardenning for schemes as Alamouti as we don't have beamforming gain there? But still we have diversity gain. What if we have very large diversity gain ? Does not the random channel behave like à deterministic one that can be considered as channel hardenning ?

[@WirelessFuture]

@@amahbubul85 It is actually the diversity gain that leads to channel hardening, so it is achievable also with space-time block codes (but the Alamouti code smis limited to two antennas, so other codes are needed).

[@amahbubul85]

@@WirelessFuture thanks. I mentioned Alamouti just as an example of a scheme without array gain

[@sarahcharlotte6681]

Sir one doubt. I am doing my research . I took base paper title as spectral efficiency using Hybrid relay reflecting intelligent surfaces in cell free massive MIMO. What can i do to my research paper?

[@WirelessFuture]

I don’t know what there is to do on that topic. I suggest that you start with figuring out: What is the benefit of adding RIS to a cell-free massive MIMO system and how can you prove that the benefit is substantial? The next question might be: what are the challenges with achieving those benefits in practice?

[@amahbubul85]

Do you please have a pdf of the slides ?

[@WirelessFuture]

Yes, there is a link in the description of the video.

[@James-ie5em]

Are comments moderated?

[@shivakumarnagamangala4230]

Excellent basics..theory...needs detailed calculations for practical usage.

[@WirelessFuture]

Shivakumar Nagamangala The detailed theory can be found in the book Massive MIMO networks massivemimobook.com

[@RenoBlade2]

Hi, nuce Video! I habe a question Left. Is the Naming MIMO Not leading in the wrong direction. You use the more Antennas for beamforming and interference Reduction. Is it possible with digital beamforming to calculat 2 beams with different ways to the mobile?

[@WirelessFuture]

Eduard Walz, MIMO refers to having multiple antennas at the base station that are used to serve multiple users. If a user has more than one antenna and the channel contains multiple paths, you can send two different beams to/from this user.

[@Susheelh]

Thank you for Sharing! Very well explained.

[@subaashkathir415]

Hi, Are you saying digital beam forming will have separate RF path for each antenna? Though flexible, will it not consume more power and extra components?

[@WirelessFuture]

Subaash Kathir Yes, digital beamforming require separate RF chains, otherwise it is not digital. It will indeed consume more power than a single antenna system, but not necessarily more than a hybrid analog-digital system that some people advocate for. The system can become vastly more energy efficient since you spend slightly more power to get a much higher capacity.

[@schigullapally1]

Excellent lecture. Expert analysis.

[@einekleineente1]

Ecellent video. One thing I don't understand: With Massive MIMO we can have a laser like beam to a phone. Okay so far. But what e.g if we have users that sit e.g. in the same class room (of course only during a break) that use their phones? We would then have one laser like beam from the base station to the students in the class room? But that would have a lot of interference per single user? Also what does massive MIMO help for data in the uplink? The users send data with their phones that maybe has 4 TX antennas. But that is not enough to reach the base station then. Or where am I goind wrong?

[@WirelessFuture]

The more antennas the base station have, the more laser-like the beams will be. In practice, the signal beams might be too wide to serve two people that sit right next to each other. But if they are located in different parts of the class room, it can still work out. The signal beams for the two users can be designed to minimize the interference, using a method called zero-forcing precoding. In the uplink, the base station uses its many antennas to separate the signals from the different users. It works equally well as in the downlink. It is like having 100 ears that hear different superpositions of the same signals and then jointly processes their received signals to distinguish between the users.

[@Karlemids]

Good talk thank you have these mmWaves been tested for health issues?

[@WirelessFuture]

Karlemids this talk is not about mmWaves. But, yes, ITU has of course researched these things thoroughly: www.itu.int/en/ITU-T/Workshops-and-Seminars/20171205/Documents/Jafar_Keshvari_v1.pdf

[@Karlemids]

thank you for that link. i understand your talk wasn't specifically about mmWaves - but 5G will be utilizing mmWaves - yes? also there are many other studies that suggest mmWaves can be dangerous to living things. would you like me to post the links for you? thank you.

[@WirelessFuture]

Karlemids, please note that anyone can publish any study these days since there are plenty of pay-to-publish journals. And there is plenty of conspiracy theories floating around. That is why the United Nation’s agency ITU is the one that you should listen to.

[@badriyah43]

@@Karlemids I wouldn't trust the United Nations from there track record

[@NotoriousU87]

Thanks...you made 5G very interesting..

[@Dinhlocvu6666]

This book is quite easy to understand for graduate students. But I have read chapter 5 and do not understand why there is a formula 5.16, can you explain it for me please, thank you very much!

[@Dinhlocvu6666]

Thanks everyone, I've already understood it.

[@gouthamraj1308]

massive mimo means how much antennas are preffered?

[@WirelessFuture]

GOUTHAM RAJ The more antennas the better. At least 64 is usually needed to call it massive. Also check out: ma-mimo.ellintech.se/2016/10/27/how-many-antennas-are-useful/

[@gouthamraj1308]

thank you sir

[@arashmahmoudian]

Excellent lecture!!

[@rakmawa]

how come you yourself didn't use a laser pointer?

[@WirelessFuture]

Rakesh Mawa, the laser pointer is difficult to see in the video recording, while the stick is large and clear.

[@abinetendale2455]

thanks more which is a good presentation!

[@张酱-d4x]

excellent lecture， thanks a lot

[@jatindersinghjudge]

Very well explained

[@a_aliouat]

thats great , thank you

[@pstreicher]

To short to show the pages. I am a slow reader. Liking the presentation though. Keeping me up to date with 5G. Good day, mate!

[@WirelessFuture]

You are most welcome to pause the video to read the slides! 😀

[@ananddr84]

Massive MIMO is SU-MIMO ?

[@WirelessFuture]

No, it is mainly about multiuser MIMO, that is, serving many users at the same time and frequency. One can send 1-2 streams per user, but serve tens of the users simultaneously.

[@ananddr84]

@@WirelessFuture Will 64T64R serve as both SU-MIMO and MU-MIMO ?

[@ananddr84]

@@WirelessFuture I am confused . You have wrote a blog " six difference between MU-MIMO and mMIMO? Now you are telling mMIMO is MU-MIMO. Please help

[@WirelessFuture]

@@ananddr84 The terminology is indeed confusing and I wasn’t the one coming up with it. 😀 The blog post compares “conventional MU-MIMO” with Massive MU-MIMO, where the latter is usually expressed in short form as Massive MIMO.

[@WirelessFuture]

@@ananddr84 There are experiments where it has been used to transmit 16 spatial layers/streams, divided between 8 users (two layers per user). That is massive MU-MIMO. However, if you are the only one requesting data for the moment, then it will reduce to only sending two layers to one device. That would be SU-MIMO. Here is more information about the experiment: ma-mimo.ellintech.se/2020/10/02/reciprocity-based-massive-mimo-in-action/

[@engrabdinasir]

thank you

[@djekyllschannel2862]

can i get your email to communicate

[@WirelessFuture]

You can find it and the presenters website

[@薛文崇]

The unit of the world record should be wrong! Should be 145.6 bit/s/Hz.

[@WirelessFuture]

We wrote 145.6 bit/s/Hz/cell to make the point that it is the total spectral efficiency of all the 22 users in the cell. The average spectral efficiency per user is 145.6/22.

[@薛文崇]

@@WirelessFuture Got it!

[@薛文崇]

One more question. When someone use ***/cell (per cell), I might think there are multiple cells, each one has ***. I think the cell built by the team of Bristol U. is only for experiment, they might not build a second one. In this case, using "145.6 bit/s/Hz of the cell" might be more appropriate.

[@WirelessFuture]

@@薛文崇 Yes, they only measured one cell. Nevertheless, it is the per-cell spectral efficiency that they made a world record for, not the spectral efficiency per user or per country. At @3:04, we introduced the concept of “spectral efficiency per cell” and then we have discussed along the way how to make it large using Massive MIMO. To show that the theoretical numbers are also practically achievable, we present these numbers. Since then, there are also commercial products that achieve high spectral efficiency per cell: ma-mimo.ellintech.se/2020/09/11/even-higher-spectral-efficiency-in-massive-mimo-trials/

[@薛文崇]

Thank you for your reply.

[@wimax802]

totally useless presentation for people with advanced degree

[@WirelessFuture]

Most videos in this channel are indeed made for communication engineering students and people working in that business. But we have a playlist with popular science content: kzbin.info/aero/PLTv48TzNRhaIUPUVvE1PKsks4KfcvThN2

[@wimax802]

dream on, ignorance is pathetic and limits your imagination