What is FD-MIMO LTE 5G | Benefits or Advantages of FD-MIMO

This page covers overview of FD-MIMO features used in LTE and 5G systems. It mentions benefits or advantages of FD-MIMO and drawbacks or disadvantages of FD-MIMO.

What is FD-MIMO?

FD-MIMO stands for Full Dimensional Multiple Input Multiple Output. In FD-MIMO, the signals are transmitted in virtual beam formats so that receivers are powered from all the three dimensions. Hence it is also known as 3D-MIMO. It is supported in 3GPP specifications of LTE up to Rel-14.

Image Courtesy : arxiv.org

As shown it uses 2D array structure which allows large number of antenna elements. These elements are packed in smaller form factors as desired by LTE/5G BS design.

As shown, FD-MIMO uses both horizontal beamforming and vertical beamforming so that beams can be focused anywhere in three dimensional spaces. The technology is implemented for both less than 6 GHz and mmwave frequency bands.

Antenna arrays are arranged in any rectangular form. Antenna array of 8x8 dimension is usually used in LTE. The same antenna array with smaller size can be used in 5G NR system.

Due to advancement in technology, BBU (Baseband Unit) and RRU (Remote Radio Unit) are separately installed. In this architecture, only analog RRU are located at cell site and hence reduces equipments and simplifies network installation. BBU are installed indoors and far away from the outdoor cell site. Both BBU and RRU are interfaced using CPRI/eCPRI interface. Higher order MU-MIMO is also supported by FD-MIMO.

Benefits or advantages of FD-MIMO

Following are the benefits or advantages of FD-MIMO:
➨It supports multiple users on same bandwidth. Hence it increases spectrum efficiency.
➨It reduces interference at the receiver from other overlapping transmissions. This increases power of the signal at the receiver.
➨It significantly improves cellular capacity by 3 to 5 times.
➨Antenna arrays with small factor can be used at cellular towers.
➨Use of AAS in FD-MIMO offers dynamic beam pattern adaptation in three dimensional space.
➨It offers efficient and simple operation & management of the FD-MIMO based system.
➨FD-MIMO antenna array increases average system throughput by 2 to 3 times compare to conventional antenna array.

Drawbacks or disadvantages of FD-MIMO

Following are the drawbacks or disadvantages of FD-MIMO:
➨As number of antenna elemenets increase, the system becomes more complex and requires robust signal processing algorithms at the receiver.
➨It is more expensive compare to conventional MIMO system.

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