Beamforming Technology

- Overview

The idea of beamforming is to steer the beam to only the desired direction or user. Since energy is not spread in all directions, the transmission range is thus improved by concentrating the beam in one direction.

Beamforming is the ability to adapt the radiation pattern of the antenna array to a particular scenario. It is a technique by which an array of antennas can be steered to transmit radio signals in a specific direction. Rather than simply broadcasting energy/signals in all directions, the antenna arrays that use beamforming, determine the direction of interest and send/receive a stronger beam of signals in that specific direction. 

This technique is widely used in radars and sonar, biomedical, and particularly in communications (telecom, Wi-Fi), specially 5G - Where very high data rates are required and the only way to support this would be to maximize transmit and receive efficiency by using beamforming. In this technique, each antenna element is fed separately with the signal to be transmitted. The phase and amplitude of each signal is then added constructively and destructively in such a way that they concentrate the energy into a narrow beam or lobe. 

- 5G NR: Beamforming and Massive MIMO (mMIMO)

Due to the high propagation loss of the millimeter wavelengths (mmWaves) employed in 5G new radio (5G NR) systems, plus the high bandwidth demands of users, beamforming techniques and massive Multiple Input and Multiple Output (mMIMO) are critical for increasing spectral efficiencies and providing cost-effective, reliable coverage. As the number of mobile users and their demand for data rises, 5G must handle far more traffic at much higher speeds than the base stations that make up today’s cellular networks. Beamforming is one of the burgeoning technologies that will help get us there.  

Terms beamforming and mMIMO are sometimes used interchangeably. One way to put it is that beamforming is used in mMIMO, or beamforming is a subset of mMIMO.  Beamforming essentially “points” an antenna to actively or passively “listen” to a specific area or device and, as a technology, has been around since of the early days of mobile broadband. 

Beginning with 3G, Multiple Input Multiple Output (MIMO) technology allows for data signals to be sent or received over several antennas using the same channel. Fast forward to June 2019 and 3GPP’s Release 15. Improvements in beamforming and beam management (beam switching, recovery and refinement) techniques can now increase coverage and capacity across more control and broadcast channels compared to LTE, with radios of up to 64 or more transceiver and antenna elements. Massive MIMO adds even more capacity without adding more antenna elements, due to the increasing degrees of freedom that is available to an antenna array to modify a transmitted signal – even for multiple users and antennas. 

- Hybrid Beamforming

To optimize signal strength at the mobile device, New Radio (NR) uses a combination of analog and digital beamforming. The idea of beamforming is not new to mobile communications, as LTE networks extensively use digital beamforming today. With 5G, however, the challenges of signal propagation and smaller antenna sizes motivate the use of extensive analog beamforming techniques. Above 24 GHz, analog beamforming of narrower beam widths gives 5G base stations the ability to steer downlink signals more efficiently. The process first involves beam scanning, so the base station can identify the most effective beam location for a specific mobile device. Using this approach, the recipient of the downlink transmission benefits from higher signal strength—particularly by using higher order modulation schemes. However, beamforming ultimately introduces significant test challenges. Not only does each beam need to be characterized and tested but over-the-air measurements are also critical to validate radio performance. 

- Beamforming for 5G and Beyond Millimeter-Wave Systems

Massive MIMO technology will form the foundation of super-fast 5G networks and will utilise beamforming technology, enabling the targeted use of spectrum. Beamforming can help massive MIMO arrays, which are base stations arrayed with dozens or hundreds of individual antennas, to make more efficient use of the spectrum around them. The primary challenge for massive MIMO is to reduce interference while transmitting more information from many more antennas at once. At massive MIMO base stations, signal-processing algorithms plot the best transmission route through the air to each user. Then they can send individual data packets in many different directions, bouncing them off buildings and other objects in a precisely coordinated pattern. By choreographing the packets’ movements and arrival time, beamforming allows many users and antennas on a massive MIMO array to exchange much more information at once. 

"For millimeter waves, which are high-frequency waves expected to play a key role in 5G networks, beamforming is primarily used to address a different set of problems: Cellular signals are easily blocked by objects and tend to weaken over long distances. In this case, beamforming can help by focusing a signal in a concentrated beam that points only in the direction of a user, rather than broadcasting in many directions at once. This approach can strengthen the signal’s chances of arriving intact and reduce interference for everyone else.

- Network (Relay) Beamforming

In the past decade, with the booming research in cooperative relay communication, a new type of beamforming, namely network beamforming (or relay beamforming), has appeared. A network beamformer is implemented neither at the transmitter nor at the receiver but at the intermediate relays to adaptively process signals transmitted via different relay paths. 

In fact, one can view a network beamformer performing simultaneously the task of a receive beamformer and that of a transmit beamformer. Network beamforming is an integrated combination of receive beamforming applied to the signals received at different relays from one or more sources and transmit beamforming applied to the signals sent from different relays to the corresponding destinations. A prominent distinction of network beamforming compared to conventional transmit and receive beamforming is that network beamforming is performed somewhere between the two ends of a channel which connects a source to a destination, instead of at either end. Thus, a virtual kind of channel design of the communication systems is realized via network beamforming. 

Successful network beamforming solutions have shown to provide large data-rates and/or improve link reliability. These advantages offered by network beamforming have presented new challenges to the research community. Research in this area has led to new analytical and optimization tools, which can be beneficial in solving communication problems in general.