# Hybrid Beamforming in Massive MIMO for Next-Generation Communication Technology
## 2 Beamforming  
In massive MIMO, each antenna element is controllable, unlike the conventional array and full dimensional MIMO (FD-MIMO); this controllable character will enable beamforming, which is the soul of 5G and future communication technology, and in this process, radio waves will be concentrated in a narrow angular region which will improve spectral efficiency significantly [4]. Beamforming involves adjusting the magnitude and period of each data signal transmitted from multiple antennas to steer the signal in a specific spatial direction, leveraging the channel state information (CSI) convenient at the sending end. Precoding/beamforming is primarily used to improve the network effectuation by exploiting the CSI. More antennas mean the beam will be narrower, intended to overcome the shortcomings of interference mitigation strategies that cannot successfully battle inter-user interference (IUI) [15]. Beamforming is a process in which a radiation pattern is directed toward a particular region only, creating constructive interference in certain desired angles and destructive interference in undesired angles [16]. It was first demonstrated in 1905 by German scientist [PERSON] by developing a phased array of three antenna elements [17]. The more antennas involved in beamforming, the greater the directionality of the beam, and more power will be directed to the user equipment [18], and the spatial power distribution will be given by the vector sum of fields emitted by the individual antenna elements (also termed as array radiation pattern). Beamforming is also accepted in different fields like Sound Navigation And Ranging (SONAR), Radio Detection And Ranging (RADAR), Acoustics, Seismology, Biomedical, and Wireless Communications. It enhances the function of a communication system by employing the interference rescission concept while using efficient beamforming algorithms. Signal intensity and degree of departure can be altered via beamforming, which also aids in voltage modulation and prudent beam guiding; therefore, beamforming security is increased, as the signal will only be received by the intended receiver [19]. The primary achievement of beamforming is the transmit/receive gain when compared to omnidirectional transmission. Beamforming is divided into three architectural categories: analog, digital, and hybrid. Before moving on to hybrid beamforming, let us first quickly discuss analog and digital beamforming. The simplest method is analog beamforming, which uses a single-phase adjustment in the analog domain. With analog beamforming, the output of a single radio frequency (RF) transceiver is divided into several routes that correspond to the array's antennas. Each signal is put through a phase shifter before getting to the antenna element. Each transmitting component has a phase and amplitude controller that pedals the transmitted signals' phase and amplitude, respectively. Active beamforming antennas also enable the transmitting element to contain a power amplifier, in contrast to passive beamforming antennas, which only include a single high-power amplifier in the RF chain. An analog beam former can only form one beam at a time since it has a single RF chain. Due to minimum hardware and software overhead and minimal energy usage of phase shifters and dampers, this beamforming approach is the simplest, most affordable, and energy-efficient, as shown in Figure 1. It performs significantly less due to lower antenna gain [20; 21]. \begin{table}
\begin{tabular}{l l} \hline \hline
**Category** & **Feature/Application/Challenge** \\ \hline \multicolumn{2}{c}{Key Features} \\ \hline Frequency Range & Sub-THz to THz (100 GHz to 3 THz) \\ \hline Data Rate & Up to 1 Tbps \\ \hline Latency & Less than 1 ms \\ \hline Connection Density & 10 million devices/km\({}^{2}\) \\ \hline Energy Efficiency & 10 times more efficient than 5G \\ \hline Mobility & Up to 1000 km/h \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Features and applications of 6G.