At this article, I’ll start with the beamforming motivation. Then I’ll answer the question What is Beamforming, Next will mention the beamforming types and specially Hybrid Beamforming.
5G goal is achieving higher data rates, lower latency network accesses, and support different use cases. And with higher data rates comes the need for wider bandwidth spectrums.
Today, available bandwidth in the spectrum up through 6 GHz isn’t sufficient to satisfy these requirements. This, in turn, has helped move the target operating frequency bands up into the millimeter-wave range for the next generation of wireless communication systems.
The small wavelengths at these higher frequency bands enable implementations with many more antenna elements per system within very small form factors. However, it also increases the signal-path and propagation challenges associated with operating at these frequencies.
These losses can be reduced with intelligent array design and the use of spatial signal processing techniques, including Beamforming. This type of processing is enabled by large arrays and can be used directly to provide higher link-level gains to overcome path loss and undesirable interference sources.
Beamforming overcomes the path loss issue at Higher Frequency Band.
Beamforming is a process to produce the radiated beam patterns of the antennas by completely building up the processed signals in the direction of the desired terminals and cancelling beams of interfering signals.
But the question, How can Beamforming direct the signal to only the desired terminals?
Beamforming uses multiple antennas to control the direction of the antenna by appropriately weighting the magnitude and phase of individual antenna signals in an array of multiple antennas.
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.
The application of beamforming has the following advantages:
- Enhanced Energy Efficiency: Massive MIMO systems are assisted by beamforming processes to reduce the power consumption of the entire system by computing the optimal quantity of antenna elements that
meet several essential criteria for manipulating energy-efficient massive MIMO systems.
- Improved Spectral Efficiency: Power controlling of the uplink and downlink signals, utilization of the information of the training sequence, and improvement of the signal quality by beamforming antenna elements enable capacity improvements.
- Increased System Security: The concept of beamforming is to steer the transmitted signal toward the intended user; therefore, the receiver will be the only party to recover the wanted signal from the overlay signal.
- Digital Beamformer: where each antenna element has its own corresponding baseband port offers the largest flexibility.However A full digital beamformer with several hundred antenna elements might be infeasible or at best feasible but very power hungry and complex.
So Digital Beamformer is very power consuming.
- Analog Beamformer: one baseband port feeds an analog beamforming network where the beamforming weights are applied either directly on the analog baseband components, at some intermediate frequency, or at RF. However in a multi-user environment this can lead to interference, if pure beam separation is not sufficient.
So Analog Beamformer is not suitable for multi-user environment.
- Hybrid Beamformer: Hybrid beamforming is a technique you can use to partition beamforming between the digital and RF domains. System designers can implement hybrid beamforming to balance flexibility and cost
trade-offs while still fielding a system that meets the required performance parameters.
So Hybrid Beamformer enables a compromise with respect to both complexity and flexibility between analog and full digital beamformer.
Hybrid beamforming designs are developed by combining multiple array elements into subarray modules. A
transmit/receive (T/R) module is dedicated to a subarray in the array and therefore fewer T/R modules
are required in the system.
The number of elements, and the positioning within each subarray, can be selected to ensure system-level performance is met across a range of steering angles.
The Hybrid beamforming type utilizes advantages of both analog beamforming and digital beamforming type. Hence the name hybrid beamforming. Here precoding is applied to both analog domain and digital domains i.e. it employed precoding/beamforming at both radio frequency(RF) and baseband.
Due to this, it has been adopted in millimeter wave radio based next generation mobile networks including 5G.