MIMO stands for Multiple Input Multiple Output. It is a wireless technology used to improve communication performance by employing multiple antennas at both the transmitter and receiver ends of a communication link. The primary benefits of MIMO include increased data throughput and link range without requiring additional bandwidth or increased transmit power.
MIMO technology is a foundational component of modern wireless communication standards, including Wi-Fi (802.11n/ac/ax), 4G LTE, and 5G NR, enabling them to meet the growing demand for higher data rates and more reliable communication in dense user environments.
It achieves these improvements through several key techniques:
Spatial Multiplexing: This technique involves transmitting different data streams simultaneously from multiple antennas. The receiver distinguishes these separate streams using its multiple antennas, effectively increasing the data rate within the same bandwidth.
- Enables parallel transmission of independent data streams.
- Increases throughput without extra spectrum.
- Requires complex signal processing at the receiver.
Beamforming: Beamforming focuses the signal strength in specific directions to improve signal quality and range. It uses the multiple antennas to steer the signal beam towards the intended receiver, enhancing the efficiency of the communication.
- Improves signal-to-noise ratio (SNR) for targeted users.
- Reduces interference to other users.
- Can be implemented using analog, digital, or hybrid techniques.
Diversity: MIMO utilizes the spatial diversity provided by multiple antennas to improve the reliability of the communication. By receiving multiple versions of the signal through different paths, the system can combat fading and interference, enhancing the robustness of the signal.
- Mitigates the effects of multipath fading.
- Improves link reliability and reduces error rates.
- Common diversity techniques include space, time, and frequency diversity.
Spatial Multiplexing Gain: MIMO systems can achieve a linear increase in capacity with the number of transmitting or receiving antennas, under ideal conditions, without additional bandwidth or transmit power.
- Capacity increases proportionally with the number of antennas.
- Most effective in rich scattering environments.
- Requires sufficient separation between antennas to ensure independent signal paths.