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Understanding 5G Beamforming System Architecture

Blog Post created by AlyssaRao Employee on Jul 7, 2016

This post covers the new video on YouTube, How to Understand 5G: Beamforming. In this “How To” video you will learn about some fundamental concepts, functionality, and design applications of three types of multi antenna beamforming architectures at the system level. You will also learn about beamforming techniques being proposed for 5G and how they affect mobile communication performance. As antenna arrays get more sophisticated and increase in operating frequency the use of accurate system modeling and the channel effects are becoming crucial in the design process.

Baseband Beamforming architectures

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Figure 1. Baseband Beamforming System Architecture: Weighting factor Wi is a function of amplitude and phase with i {1..n} as number of antenna paths, precoding and combining are performed in BB.

In the baseband beamforming architecture we get large antenna gain and this enables multi stream, multi user connections with a variety of transmission modes. However, one of the biggest challenges designers face is when the design requires hundreds of antennas, which all need hundreds of power-hungry converters (both analog to digital and digital to analog). This high power requirement will increase hardware complexity and power consumption of the system and makes this architecture impractical for these types of designs. As a result, digital beamforming architecture is mainly used in mobile applications in base station downlink transmitters. It is interesting to note that because of digital beamforming’s high power consumption some of the digital beamforming proposals are for receivers to mitigate uplink inter cell interference.

RF Beamforming architectures

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Figure 2. RF Beamforming Receiver Architecture: Weighting factor Wi is a function of amplitude and phase with i {1..n} as number of antenna paths, precoding and combining are performed in RF.

 

In RF beamforming all the precoding and combining is done in the RF side. Compared to digital beamforming there are implementation advantages in terms of lower power consumption and lower hardware complexity.

Since high performance phase shifters in CMOS introduce phase and amplitude error verses frequency as well as phase variation verses the control voltage, the design of high performance phase shifters in CMOS turns out to be quite challenging. Some of the early 5G prototyping systems in the 63.5 GHZ frequency band has been proposed using RF beamforming architecture.

Hybrid Beamforming architectures

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Figure 3. Hybrid Beamforming System Architecture(Shared Array):
Baseband precoder(FBB) / combiner(WBB) using digital signal processing and RF precoder (FRF) / combiner(WRF) using phase shifter.

 

The hybrid beamforming structure combines the strengths of both analog and digital beamforming systems to reduce overall hardware complexity. In the hybrid structure the precoding and combining is done in both baseband (BB) and RF sections. By reducing the total number of the RF chains and analog to digital and digital to analog converters, hybrid beamforming still gets similar performance to that of digital beamforming, but saves power and complexity. With this structure even though we used a large enough number of antennas, the lossy mmWave channel naturally suppresses multi path interference and reflections.

You can design a real world multi antenna system using Keysight’s 5G simulation library and multi-channel RF models by following this “How To” video.

When designing mixed signal components you have to consider issues such as high sampling rates, quantization error, jitter, and high power consumption. In the antenna arrays at the system level you need a new mmWave channel model that supports multiple antenna paths and bandwidth in order to get a realistic picture of system performance. All of these complex issues can be solved only when you utilize trusted reference algorithmic modeling and innovative simulation methodology. Keysight SystemVue makes it easy to investigate new system architectures and create reliable system proposals and specifications. Also 3D visualization can help you identify and address problem areas that improve system performance at an early stage of your design.

Watch “How to understand 5G beamforming“ and download the workspace at: www.keysight.com/find/eesof-how-to-5g-beamforming now to get a head start with your 5G communication design.

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