Sunday, 25 July 2021

5G NR: Beam Management in 5G NR

                                                 

The current status it seems that most of the deployment would be in very high frequency (millimeter wave) and this high frequency deployment would be one of the most important characteristics of 5G (NR).


Mostly by Nature of the wave (by Physics), when we use low and mid-range of frequency, we can transmit a signal in all direction (as in (A)) or relatively wide angles (as in (B)). However, when we use very high frequency, we would not have much choice except using a huge antenna array. As a result of using this kind of huge antenna array, the resulting radiation would be a beam as in (C).






In case of low / mid frequency region without using massive antenna array (as in (A) / (B)), a single transmission would cover a lot of UEs simultaneously. However, when the radiation become beam-shaped as (C), it is very difficult to cover multiple UEs in single transmission unless those multiple UEs are located in very close proximity. To handle this problem, we need a very sophisticated idea of managing/controlling the beam to cover the multiple devices scattered in all directions and the management/control mechanism should be different depending on the situations. All of these collections of idea would fall into the title of "Beam Management" in the specification.

Beam Management/Control for each specific situation will be described with relevant situation Beam Management during Synchronization, Beam Management during Initial Attach, and Beam Management in connected status etc.




As an example, let's think of following case. There is a Base Station with Massive MIMO operating at the very high frequency. There is a UE around the Base Station and you are just about to turning on the UE. Once the UE is turned on, it would start Synchronization process. For this step, the Base Station would transmit the special signal called Synchronization Signal and the signal should be able to reach to every UEs around the base station. However, here comes a serious problem with the base station sending signal in Beam. It is the fact that the signal beam can point to a very narrow area and it cannot cover a very wide area at the same time. Simply put, now you have the following question.






https://www.youtube.com/watch?v=GEx_d0SjvS0
https://www.youtube.com/watch?v=8rMtqRObvvU
https://www.youtube.com/watch?v=38kp5uRrG2s Imp
https://www.youtube.com/watch?v=8rMtqRObvvU&t=89s
http://www.sharetechnote.com/html/5G/5G_Phy_BeamManagement.html

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