Beamforming uses phased array antennae systems to focus the wireless signal toward a specific receiver or target instead of an omnidirectional broadcast. Combined with massive multiple input / multiple output (MIMO) antenna technology, beamforming is a key enabler of faster data rates and higher device densities supported by 5G networks compared with 4G technology.
The physical structure needed to implement beamforming is an array of antennas regularly spaced in two dimensions (Figure 1). The direction of the emitted beam is determined by controlling the phases and amplitudes of the signals sent to the individual antennas, resulting in constructive interference in the desired direction and destructive interference in other directions. Some of the benefits of beamforming include:
- Improved signal quality
- Reduced interference
- Increased range
- Reduced power requirements
Figure 1. A 5G beamforming array can have dozens of polarized orthogonally oriented radiating elements like those pictured above. (Image: Altium)
Polarization
Polarization is used to enhance the performance of beamforming by providing more precise control over the direction of the beam and creating a narrower beam with higher signal strength. 5G networks often use dual-polarization beamforming that simultaneously combines horizontal and vertical polarization.
Dual polarization can maintain signal quality even in complex 5G environments that experience fading and signal reflections. The narrower beam further improves power efficiency. Three primary beamforming architectures are used to phase each antenna element: analog, digital, and hybrid, combining analog and digital elements.
Analog beamforming
Analog beamforming is relatively inexpensive and simple to implement. It uses phase shifters to delay signals sent to different antennas, resulting in a phase difference in the emissions from individual antennas. The phase shift and the spacing between antennas determines the beam direction.
Phase shifting can be implemented with static analog beamforming structures or digitally controlled phase shifters. With digitally controlled phase shifters, the digital control for phase shifting can be pre-calibrated and stored in memory for fast and precise beam generation.
Digital beamforming
Digital beamforming supports more complex use cases compared with analog beamforming. It’s achieved using signal processing algorithms that adapt to changing channel conditions in real-time, enabling multiple users to be simultaneously served with dedicated beams.
When implementing digital beamforming, channel conditions are constantly monitored to determine each antenna’s optimal phase and amplitude settings to deliver maximum signal strength to the receiver. Another benefit of digital beamforming is rapidly adjusting the beam to follow a moving receiver. Real-time signal processing requires significant processing power.
In digital beamforming, each antenna is directly connected to a transceiver chain, followed by an ADC/DAC with a high sampling rate and high precision. The hardware cost is a significant challenge, and full digital beamforming has achieved limited commercialization.
Hybrid (digital + analog) beamforming
Hybrid beamforming was developed to address digital beamforming’s cost and complexity challenges while still delivering high performance. A purely digital approach requires a dedicated RF chain for each antenna. In hybrid beamforming, digital beamforming is combined with analog beamforming, with fewer RF chains and analog phase shifters grouped into subarrays.
Hybrid beamforming can be viewed as a three-step process. First, the system uses channel state information (CSI) to determine the optimal beamforming parameters. Next, the signal is digitally precoded based on the CSI to distribute the signal to the appropriate subarrays. Finally, analog phase shifters are applied for each subarray.
Hybrid beamforming balances cost and performance and is more easily scaled than digital beamforming with a large antenna array. As a result, it’s widely used in 5G networks. Compared to purely analog or digital beamforming, hybrid beamforming can also offer better performance in terms of data throughput and signal-to-noise ratio in complex environments.
beamforming
Summary
Beamforming is a key technology in 5G networks. It enables targeted delivery of high data rates to specific users, improves 5G network efficiency, reduces energy consumption, and supports more reliable connectivity. It can be implemented using analog, digital, or hybrid architectures. Hybrid beamforming that combines analog and digital techniques generally offers the best cost/performance tradeoff.
References
5G beamforming: an engineer’s overview, Avnet Abacus
Beamforming: Improving Wireless Communication Quality and Efficiency, Nearity
The Basics of Digital and Analog Beamforming with Phased Arrays, Cadence
The Role of Millimeter-Wave Technologies in 5G/6G Wireless Communications, IEEE Journal of Microwaves
Types of Beamforming and Their Uses in RF PCBs, Northwest Engineering Solutions
What Is Beamforming?, Spiceworks
What is Hybrid Beamforming?, Altium
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