RFMicrowave Massive MIMO vs. mmWave MIMO: Key Differences Explained
This article breaks down the differences between Microwave Massive MIMO (M-MIMO) and mmWave (Millimeter wave) MIMO. Let’s dive into a side-by-side comparison.
Key Specification Comparison
Here’s a table outlining the key differences in specifications between the two technologies:
| Specifications | Microwave Massive MIMO | mmWave MIMO |
|---|---|---|
| Bandwidth | 20 to 50 MHz | > 500 MHz |
| Number of antennas at Base Station (BS) | 32 to 64 | 64 to 256 |
| Number of antennas at Mobile Station (MS) | 1 to 4 | 4 to 12 |
| Beamforming type | Digital | Analog |
| Number of users supported | About 10 | About 4 |
| Cell size | Micro or Macro | Pico |
| Small scale fading | More AS and clusters, correlated with higher rank | Fewer AS and clusters, correlated with lower rank esp. in LOS |
| Large scale fading | distant dependent pathloss, shadowing | distant dependent with random blockage model |
| Penetration Loss | Some | Usually Higher |
| Channel Sparsity | Less | More |
| Spatial correlation | Less | More |
| Orientation | Less | More |
| Network Deployment | installed in low BS density areas | installed in high BS density areas |
Deep Dive into the Differences
Let’s explore some of these differences in more detail:
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Bandwidth: mmWave operates on significantly larger bandwidths (greater than 500 MHz) compared to Microwave Massive MIMO (20 to 50 MHz). This higher bandwidth is what allows mmWave to deliver much faster data rates.
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Antenna Count: While both technologies utilize a large number of antennas, mmWave MIMO generally employs even more antennas at both the base station (64-256) and the mobile station (4-12) compared to Microwave Massive MIMO (32-64 at the base station and 1-4 at the mobile station). This allows for more focused beamforming.
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Beamforming: Microwave Massive MIMO typically uses digital beamforming, while mmWave MIMO often utilizes analog beamforming. Hybrid beamforming is also common in mmWave systems, combining the benefits of both digital and analog approaches. Digital beamforming offers more flexibility and precision, but can be more computationally intensive.
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Cell Size and Deployment: Microwave Massive MIMO is well-suited for micro or macro cell deployments, often in areas with lower base station density. mmWave, due to its higher frequencies and greater path loss, is typically deployed in pico cells with a higher density of base stations.
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Fading Characteristics: The small-scale fading characteristics differ. Microwave Massive MIMO tends to have more angular spread (AS) and clusters, leading to higher rank correlation. mmWave, especially in line-of-sight (LOS) scenarios, has fewer AS and clusters, correlating with lower rank.
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Penetration Loss: mmWave signals suffer from significantly higher penetration loss compared to microwave signals. This means they have a harder time passing through walls and other obstacles, contributing to the need for higher base station density.
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Channel Sparsity, Spatial Correlation, and Orientation: mmWave channels exhibit greater sparsity, spatial correlation, and sensitivity to orientation compared to Microwave Massive MIMO. These factors need to be carefully considered in system design and deployment.
In essence, Microwave Massive MIMO is a good solution for improving capacity and coverage in existing cellular networks, while mmWave MIMO is geared towards ultra-high-speed data delivery in densely populated areas where its shorter range and higher penetration loss can be managed through dense network deployments.
