Massive MIMO or massive multiple-input and multiple-output technology is a subset of multi-user MIMO or MU-MIMO technology that involves using a large number of antennas at the transmitter and receiver ends of a wireless communication system or more specifically, at the base stations of cellular networks to improve and increase network performance.
The multiple antennas in a Massive MIMO system work coherently and adaptively to significantly increase throughput, capacity density, and efficiency in a cellular network. Nevertheless, understanding the specific advantages and applications of Massive MIMO requires understanding its role in cellular network technologies, as well as the working principle and uses of multiple-input and multiple-output or MIMO technologies.
Pros: The Advantages of Massive MIMO Technology
For starters, multiple-input and multiple-output or MIMO is an antenna technology that has become a fundamental element of modern wireless communication standards. Specific sets of MIMO technology collectively represent a method for multiplying the capacity of an access point and implementing multipath signal propagation using multiple antennas.
On the other hand, MU-MIMO is a specific set of MIMO technologies that enables access points such as routers and cellular base stations to send and receive multiple data streams simultaneously, compared to the single-user or SU-MIMO, which works on a first-come, first-serve basis, and thus, cannot send and receive data to multiple users simultaneously.
Massive MIMO fundamentally expands the capabilities of MU-MIMO through the inclusion of a higher number of antennas to bring drastic improvements in network performance. Hence, it has become one of the technological underpinnings of modern wireless cellular networks to include the 4G standard, LTE and LTE Advanced technologies, and 5G technologies.
Placing a large number of antennas allow a particular access point to focus the transmission and reception of electromagnetic signals to specific regions or targeted areas, thus improving throughput, capacity, and efficiency. Note that a Massive MIMO system also coordinates the operation of these antennas through machine learning and algorithm.
Below are the specific benefits and applications of Massive MIMO technology:
1. Increases Network Capacity
Massive MIMO increases the capacity of a particular wireless communication network in two ways. First, it enables the deployment of higher frequencies, such as in the case of Sub-6 5G specification. Second, by employing multi-user MIMO, a cellular base station with Massive MIMO capability can send and receive multiple data streams simultaneously from different users using the same frequency resources.
Note that network capacity is determined by the number or amount of total data a particular network can serve to its end-users, as well as by the maximum number of end-users that can be served based on an expected service level.
2. Enhances Network Coverage
Another advantage of Massive MIMO is that it provides high spectral efficiency through the coordination of multiple antennas using simple processing and without intensive power consumption. When used in a 5G cellular network technology, it allows 10 times more spectral and network efficiency compared to fourth-generation networks. Furthermore, when applied in 4G technology, it improves the deep coverage of fourth-generation networks.
Because next-generation cellular network technologies use electromagnetic radiation with higher frequencies or more specifically, frequencies within the upper limits of radio waves and the range of microwaves, the signals they generate travel a short distance. Hence, enhancing network coverage is critical in modern and future cellular technologies.
3. Complements Beamforming
Beamforming technology works by focusing a signal toward a specific direction, rather than broadcasting in all directions, thus resulting in more direct communication between a transmitter and a receiver, more stable and reliable connectivity, and faster data transmission. As a signal processing technique and traffic-signaling system, this technology depends on advanced antenna technologies on both access points and end-user devices.
The large number of antennas in a Massive MIMO system enables three-dimensional beamforming in which a single beam of signal-bearing electromagnetic radiation travels through vertical and horizontal directions. The process increases data transmission rates further while reaching people in elevated areas such as buildings and those in moving vehicles
4. Enables Next-Gen Technologies
Massive MIMO is an essential component of 5G technology. For example, in Sub-6 5G specification, it allows the utilization of frequencies within the sub-6 GHz range. Moreover, in mmWave 5G specification, this technology increases frequency reach to expand network coverage, optimizes the propagation of signal-bearing electromagnetic radiation, and allows true multi-user wireless communication within a defined area.
However, although it is a key enabling technology for 5G and future cellular network technologies, it has been used for improving and repurposing the capabilities of existing 4G systems, especially LTE Advanced networks. The integration of Massive MIMO in existing 4G networks could improve further network performance.
Cons: The Disadvantages of Massive MIMO Technology
One of the biggest disadvantages of Massive MIMO is the cost associated with its implementation and deployment. The systems are several times more extensive than traditional base station units and antenna technologies. Furthermore, the design of multiple antenna systems for cellular networks is more complex and requires more effort and time during assembly and installation.
Furthermore, using frequency division duplex or FDD results in feedback overhead. This phenomenon transpires when a receiver sends out feedback signals to a transmitter. Increasing the antenna elements results in a further increase in the overhead. Hence, time-division duplex or TDD is more suitable for Massive MIMO implementation.
The placement of multiple antennas in a defined area within a base station means placing hardware components in a smaller space. An entire massive multiple-input and multiple-output system needs advanced components that are capable of delivering their intended level of performance despite their smaller size than their larger counterparts.
Remember that Massive MIMO is not simply about placing and using a large number of antennas. The entire technology also works using artificial intelligence and machine learning to complement frequency management, signal processing techniques, and data transmission. Doing so requires complex processing algorithms that further add to the cost and complexity of designing, implementing, and deploying an entire system.
FURTHER READINGS AND REFERENCES
- Chataut, R. and Akl, R. 2020. “Massive MIMO Systems for 5G and beyond Networks—Overview, Recent Trends, Challenges, and Future Research Direction.” Sensors. 20(10): 2753. DOI: 3390/s20102753
- Larsson, E. G., Edfors, O., Tufvesson, F., and Marzetta, T. L. 2014. “Massive MIMO for Next Generation Wireless Systems.” IEEE Communications Magazine. 52(2): 186-195. DOI: 1109/MCOM.2014.6736761
- Zeng, T. and Ouyang, E. 2020. “Improving Deep Coverage of 4G Network Based on Massive MIMO Beamforming Used in 5G.” IEEJ Transactions on Electrical and Electronic Engineering. 16(1): 78-84. DOI: 1002/tee.23270
