Introduction to Mobile Networks and Services

In this video, Professor Emil Björnson gives an overview of the history of wireless communications and mobile networks, and how the technology has been used for different services and applications at different times. Emerging topics such as network slicing and different types of internet-of-things devices are mentioned. The basic physical-layer concepts of digital modulation, signal attenuation, multipath fading, and interference are introduced. The three main ways of improving mobile networks for higher capacity are also covered. Finally, practical challenges regarding standardization and regulation are mentioned.
The slides are available here: github.com/emilbjornson/prese...
The video was produced as a motivation behind the course IK2560 Mobile Networks and Services at the KTH Royal Institute of Technology.
#mobilenetwork #cellular #digitalization #communication #mimo #mobileservices #wireless #5g #iot

[@hassanlaqrabti4036]

Thank you professor, i have started to watch your videos and take them as my course

[@mustang6212]

Thank you so much for this simple and instructive video, keep posting

[@willliu1306]

Thanks for your introduction. Is it possible to have the remaining course video published ?

[@amroayman2552]

Thank you very much

[@Julia-hu4xe]

Thank you for your terrific conent. I have a short question. It is about the SNR. We assume to have a 16QAM transmission. The outmost points in the IQ plane have a higher power than the innermost. The noise is for every symbol the same, I guess. Does that mean that the SNR for the outmost points (symbols) is better than for the inmost points (symbols), because of the different signal-power of the symbols?

[@WirelessFuture]

The SNR is normally computed based on the average power of all constellation points in the IQ plane. The reason is that the thing that matters is how large the distance is between the constellation points, compared to the strength of the noise. A decoding error happens when a transmitted point is moved by the noise so it looks more like another constellation point.
You are right that the instantaneous SNR is higher for the outmost points, but this is not important. It is the minimal distance between constellation points versus the noise standard deviation that truly matters, and it is the same for all points in 16QAM

[@stellatauer761]

Thanks. I saw a diagram of inside of a modern mobile phone. 8 small antennas seem to be common today. Does the smartphones already use the antennas really for beamforming or is there rather a kind of diversity utilization (e.g. switch to the antenna with highest SNR)?
Base station already use beamforming, as far as I know.

[@WirelessFuture]

The last three (?) years of iPhone models have had the statement “5G (sub‑6 GHz and mmWave) with 4x4 MIMO” in the tech specifications. So there are 4 antennas that can be used for spatial multiplexing of up to 4 spatial layers, if the channel is good enough. In poor signaling conditions, it is better to use them for beamforming to increase gain and obtain diversity.
A phone also needs wifi and Bluetooth antennas, so the total number is probably closer to 8, as you said.

[@mahermarwani2601]

Hello Professor, I have been following your videos since I don't remember.
Is it possible to attend your courses while studying at another university?
( I am doing a Ph.D. at École de technologie supérieure ÉTS in Montreal)

[@WirelessFuture]

This video was produced for a Master-level course that is given physically on our campus, so it is not possible for others to attend (and it would like be too easy for you anyway). I might try to organize PhD level course online in the future.

[@manuelbeir576]

Thanks a lot. When we want to determine the power of a signal, we take the square (s(t)^2), according to the formular. Thus, we get the unity V^2, although, the normal unit for (electrical) power is Watt. Isn't there a contradiction? (I cannot find V^2 as official unity for power.) Do you happen to have an answer to that? Thanks.

[@WirelessFuture]

Hi! Is there a particular formula in the presentation that you are referring to?
In general, power is the average energy over time, so you first need to consider an integral of s(t)^2 over time and then divide by the length of the time interval. It is also necessary to convert V^2 to power using the characteristic impedance of the receiver that measures the signal. Here are some more information about this: en.wikipedia.org/wiki/Energy_(signal_processing)

[@manuelbeir576]

@@WirelessFuture No not in that presentation. I was just a general thought. When I read about communication from different sources, I found Watt and V^2, and was confused. Nowhere was a formular which links both units.

[@al_husseinal_torfy8744]

Thank u professor, i have one question outside this video, could you tell me the formula of calculation first null beam width of the None ULA after doing optimization for the amplitude of element Iam working on the numerical part

[@WirelessFuture]

The first null beam width for a ULA is 2*arcsin(lambda/L) ≈ 2*lambda/L where the approximation is good for large arrays. L is the aperture length of the ULA and lambda i the wavelength. You can find a derivation on Page 16 here: www.ece.mcmaster.ca/faculty/nikolova/antenna_dload/current_lectures/L17_Aperture.pdf

[@al_husseinal_torfy8744]

Thank you so much professor for your replying, Is the aperture length mean L=(N*d) where N no. of antenna element??

[@WirelessFuture]

@@al_husseinal_torfy8744 yes