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What Advances Have We Seen in Massive MIMO, and What’s Next?

May 17. 2021

  • Chanakya Bandyopadhyay

    Director, RAN Technology Solutions, Networks Business, Samsung Electronics America

 

Mobile Data traffics are expected to increase annually by 25.2%1 between 2020 and 2027. With such an increase in data traffics, mobile operators cannot solely rely on conventional radios to carry that much traffics. To address the issue effectively, a powerful radio is required. It is called Massive Multi-Input Multi-Output (MIMO) radio. Massive MIMO has been playing a critical role in 4G and 5G networks for many years, and expected to increase its influence even more. Let us look at where Massive MIMO came from and where it is going.

 

Before Massive MIMO, there was MIMO. In 1993, two researchers proposed the use of spatial multiplexing, a wireless protocol to send multiple streams of data between transmitters and receivers to enhance throughput or functionality. This laid the foundation for MIMO. In 2010, industry experts start to write about Massive MIMO (though some of them originally called it ‘large-scale antennas systems’).

 

The word “Massive” in “Massive MIMO” does not refer to the physical size of the antenna, but to the number of elements. As the frequency is increased, there is a reduction in the spacing between the antenna elements, thus shrinking the size of the antenna.

 

Massive MIMO radio has many small antennas, which are used to serve multiple devices simultaneously. These tightly located antennas generate narrow beams which can be precisely focused. These tight beams strengthen the received power and reduce interference, increasing throughput significantly.

 

Here are some of the advances made in Massive MIMO:

 

 

Transmit and Receive 

 

MIMO antennas are designated by the number of transmit and receive antennas used. 2T2R, for example, refers to a system with two antennas for transmitting and two antennas for receiving data, doubling capacity, or 4T4R, which refers to four of each, quadrupling capacity. 4T2R refers to four transmit antennas with only two receiving.

 

The most common Massive MIMO antenna sizes today are 32T32R and 64T64R. Although larger is generally better, larger can mean heavier and more demanding of power, so there are tradeoffs.

Beamforming 

 

Beamforming is a method to point several antennas towards the same device, rather than having the signal propagate in all directions, as is typical. This results in higher throughput and reliability. With 4G and 5G, three-dimensional (3-D) beamforming can direct both horizontal and vertical beams at the user, greatly improving capacity. Coverage across the cell is also more reliable, even to the edge. 

SU-MIMO and MU-MIMO 

 

There are different flavors of MIMO as well: single-user (SU), and multi-user (MU). With SU-MIMO, all the transmit antennas are aimed at a single receiver (though with multiple antennas), increasing its capacity. However, if there are multiple receivers, each must wait in turn to be the recipient, in a round-robin fashion. With MU-MIMO, multiple antennas can focus on multiple receivers, increasing capacity for more than one receiver. Massive MIMO is essentially MU-MIMO with a sufficiently high number of antennas 

What’s Coming Next?

 

In 2018, Samsung shipped its first 64T64R Massive MIMO for a U.S. operator. Dell’Oro estimates global Massive MIMO investments over $10 billion in 2020.

 

The future for Massive MIMO is bright. It has gone from being a theory in 2010 to widespread deployment in less than ten years. Carriers are interested in deploying 5G Massive MIMO. Moreover, for millimeter wave (mmWave) frequency, Massive MIMO could lead to the widespread usage of 128T128R and 256T256R, effectively resolving data hot spots, including shopping malls, sports stadiums, air ports and etc.

 

Advances in software for Massive MIMO will also increase network throughput. Earlier this year, Samsung announced Mobility Enhancer, based on AI, which provides a beamforming improvement of up to 30 percent. To find out more about Samsung’s Massive MIMO, please see our White Paper: Massive MIMO for New Radio.

1 Global Industry Analysts (2021), "Global Mobile Data Traffic Industry" 

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