A multiple benefit

In the age of 5G, we no longer think twice of downloading a file — even when our cellular connection is at one or two bars — or video chatting or streaming blockbuster movies. Performing such activities is as smooth as streaming music. 5G NR (New Radio) massive MIMO (Multiple Input Multiple Output) technology is one of the major keys to unlocking these 5G user experiences.

While it involves multiple technologies, MIMO can essentially be boiled down to this single principle: a wireless network that allows the transmitting and receiving of more than one data signal simultaneously over the same radio channel. Standard MIMO networks tend to use two or four antennas. Massive MIMO is a MIMO system with an especially high number of antennas. The advantage of a MIMO network over a regular one is that it can multiply the capacity of a wireless connection without requiring more spectrum.

Massive MIMO expands beyond the legacy systems by adding a much higher number of antennas on the base station. The “massive” number of antennas helps focus energy, which brings drastic improvements in throughput and efficiency. Along with the increased number of antennas, both the network and mobile devices implement more complex designs to coordinate MIMO operations.

MIMO systems capitalize on three key concepts: spatial diversity, spatial multiplexing, and beamforming. Spatial diversity aims at improving the reliability of the system by sending the same data across different propagation, or spatial, paths.

Spatial diversity evolves into a more complex concept, which is ‘spatial multiplexing’. Now, not only are the diverse experiences of the over-air-channel utilized for performance improvements, but multiple messages can be transmitted simultaneously without interfering with one another since they are separated in space.

Beamforming is another key wireless technique that utilizes advanced antenna technologies on both mobile devices and networks’ base stations to focus a wireless signal in a specific direction, rather than broadcasting to a wide area.

Beam steering is achieved by changing the phase of the input signal on all radiating elements. Phase shifting allows the signal to be targeted at a specific receiver. An antenna can employ radiating elements with a common frequency to steer a single beam in a specific direction. Different frequency beams can also be steered in different directions to serve different users. The direction a signal is sent in is calculated dynamically by the base station as the endpoint moves, effectively tracking the user.

With the massive number of antenna elements in a massive MIMO system, beamforming becomes ‘3D Beamforming’. 3D Beamforming creates horizontal and vertical beams toward users, increasing data rates (and capacity) for all users — even those located in the top floors of high-rise buildings.

MIMO technology also allows multiple users to share the same network resources, simultaneously. Multi-User MIMO or 'MU-MIMO' allows messages for different users to travel securely along the same data pipelines, then be sorted to individual users when the data arrives at their mobile devices. Serving multiple users with same transmission increases capacity and allows for better utilization of resources. That adds up to the ability to download or stream with an improved experience for the user even in a crowded area.

The primary benefits of massive MIMO to the network and end users can be summed up as: increased network capacity, improved coverage and user experience.

Network capacity is defined as the total data volume that can be served to a user and the maximum number of users that can be served with a certain level of expected service. Massive MIMO contributes to increased capacity first by enabling 5G NR deployment in the higher frequency range in Sub-6 GHz (e.g., 3.5 GHz); and second by employing MU-MIMO where multiple users are served with the same time and frequency resources.

With massive MIMO, users enjoy a more uniform experience across the network, even at the cell’s edge – so users can expect high data rate service almost everywhere. Moreover, 3D beamforming enables dynamic coverage required for moving users (e.g., users traveling in cars or connected cars) and adjusts the coverage to suit user location, even in locations that have relatively weak network coverage.

Since 5G massive MIMO implementation is on mmWave frequencies, the antennas required are small and easy to install and maintain. Because massive MIMO, beamforming, and beam steering represent such significant changes in how 5G NR devices connect across sub-6 GHz and mmWave operating bands, validating the device quality of experience and performance on the network becomes even more critical.

Massive MIMO is just one example of the many breakthrough inventions we have brought forth from decades of research and development to unlock 5G for the mobile industry and beyond, and transform how we compute, connect and communicate.