Why MIMO Configurations Are Predominantly in Multiples of 2

MIMO (Multiple Input Multiple Output) techniques have revolutionized wireless communication technology by enhancing system capacity, reliability, and efficiency. Despite the flexibility MIMO provides, it is commonly observed that the configurations are in multiples of 2, such as 2x2, 4x4, and 8x8. But why are there no MIMO schemes such as 3x3 or 5x5?

Hardware Design and Complexity

The predominantly even-numbered configurations of MIMO techniques can be attributed to the simplification of hardware design and complexity. Many radio frequency (RF) components and digital signal processing (DSP) architectures are designed to process binary signals. Using even numbers, such as multiples of 2, significantly simplifies the design and scaling of antennas, transceivers, and associated circuitry.

Channel Capacity and Performance

MIMO systems often perform best with even-numbered antennas due to their alignment with the underlying mathematical principles governing MIMO. Algorithms for beamforming and spatial multiplexing tend to perform optimally in configurations that are powers of two. This results in better channel capacity and performance, which is crucial for achieving the full potential of MIMO technology.

Standardization

Industry standards, such as those for Wi-Fi and cellular technologies, often define MIMO configurations as multiples of 2. This standardization is a driving force behind the widespread adoption and development of MIMO technology. By adhering to these standards, manufacturers ensure compatibility across different devices and systems, leading to a robust and interoperable ecosystem.

Signal Processing Algorithms

Many signal processing techniques used for encoding and decoding MIMO signals are optimized for configurations that are powers of two. This optimization leads to improved performance in terms of throughput, reliability, and computational efficiency. The alignment of hardware and software architectures with these power-of-two configurations ensures that the full benefits of MIMO are realized.

Market Trends and Research

The focus on 2x2, 4x4, and similar configurations has fostered a cycle of research and development, reinforcing their dominance in the market. While 3x3 and 5x5 systems can be and have been studied, they may not have received the same level of attention or optimization in commercial products. The continuing emphasis on these configurations ensures that they remain the de facto standard in MIMO technology.

While configurations such as 3x3 and 5x5 are theoretically possible and can be implemented, the predominance of even-numbered multiples is driven by practical considerations related to design, performance, standardization, and market trends. This ensures that MIMO technology continues to evolve and deliver the maximum benefits to users and manufacturers alike.