5G Massive MIMO and Beamforming[Analog ,Digital,Hybrid]

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A key part of the 5G NR system relates to the use of Massive MIMO (Multiple Input Multiple Output). The term “Massive MIMO” relates to an antenna array system using a “Massive” amount of antenna elements that can serve multiple users simultaneously. Typically, the number of antenna elements is 128 or 256.


How MIMO can compansate issue in 5G

Fr
So BW is more in 5G for mmWave , so by increasing mimo loss of penetration can be compansated and mimo increment possible in higher frequency as antenna length became smaller
From above formula its clear that Prx is directly proportional to Square of wavelength and Gain of receiver and transmiter .

How MIMO Can increase capacity



From above shannon hartly theorem there are 3 component can impact Capacity 

Increase Channels (MIMO):-Utilizing SM (Spatial Multiplexing) enables multiple streams within the same RB (Resource Block). System requires CSI (Channel State Information)

Increase Bandwidth:-Existing frequency spectrum is already saturated. mmWave is required for greater bandwidth options

Increase S/N:- Since log2 (1+S/N) this has less impact

Beamforming 

Beamforming, as its name suggests is the “forming” of a “beam” of RF energy. Fundamentally, the electromagnetic wave radiation pattern from a system is focused like a beam from a torch (or laser)

Create a beam:- The easiest method to create a beam is to place multiple antennas in an “array”.

As no of antenna elemrnt increased beams becoming narrow

Basic concept of how the electromagnetic waves are reinforced in the main beam direction. This is typically termed the main lobe. It is also worth noting that the spacing between the antenna elements is expressed in wavelengths (λ), with different spacing having a different result



Beamforming is a type of radio frequency (RF) management in which a wireless signal is directed toward a specific receiving device(Rather than sending a signal from a broadcast antenna to be spread in all directions -- how a signal would traditionally be sent ). Beamforming is applied to numerous technologies, including wireless communications, acoustics, radar and sonar

Beamforming uses multiple antennas to send out and direct the same signal toward a single receiving device

Beam-Stearing :- By changing the antenna elements’ phase, a beam can effectively be steered
in image 5 th picture is perfrct example of beam stearing 

Null-stearing:- The concept of “Null Steering” is equally as important as beam steering. This can be illustrated by reviewing the radiation patterns which are sent from an antenna at the same time to four spatially separate devices. The key point relates to the fact that whist the main lobe targets the intended device, the nulls are steered to ensure minimal interference towards other devices.

Below is actual pattern of Beaforming/Beamstearing



Beam Sweeping:- The process of covering a spatial area utilizing a set of beams which are transmitted/received at pre-specified intervals and directions
The 5G NR system defines a SSB (Synchronization Signal Block). This includes NR synchronization signals and a PBCH (Physical Broadcast Channel)
Due to the narrow beams, it is important that the beam sweep covers both the azimuth of the cell’s footprint, as well as the vertical footprint

Beam Measurement:- The evaluation of the quality of the received signal. Either at the gNB or at the device

Beam Determination:-The selection of the suitable beam and is related to the measurements obtained with beam measurement.

Beam Reporting:-The procedure used by the device to send beam quality and beam decision information


Analog BF Uses a single common RF source split among multiple antenna elements. Beam is controlled by adjusting analog phase shifters along the RF path

1. Analog BF (mmW first releases)
2. The weights are applied in the time domain after D/A  conversion.
3. Same weights (beam) for an entire timeslot
4. With 2 polarizations, can do two beams per timeslot
5. Simple but inefficient use of spectrum

Digital BF Each antenna has a dedicated RF signal & path. Phases & amplitudes are digitally controlled by baseband processing 

1. Digital BF (Low and Mid Band products)
2. The weights are applied in the Baseband before D/A conversion
3. Most Flexible and best performance:
4. Different Weights per frequency blocks (PRBs)
5. Different weights in the same frequency block at same time (layers)
6. Possible to transmit to several users  simultaneously in different beams





Hybrid BF Combines aspects of analog & digital beamforming










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