The fifth-generation (5G) mobile networks use a range of technologies to provide a much better experience to customers than the earlier 4G LTE networks. MIMO – Multiple Input Multiple Output is an antenna technology that is used in 4G LTE networks, but its enhanced version, Massive MIMO, is an essential building block in the 5G New Radio (NR) networks.
Massive MIMO in 5G NR networks is an advanced antenna technology that enhances spectral efficiency, network capacity, coverage and achievable data rates. Massive MIMO uses a large number of antenna elements within the transmitter and receiver antenna panels to support multiple users simultaneously.
If you are familiar with the standard MIMO in 4G LTE networks, the adjective “Massive” can only make you think one thing – a really big MIMO. While there is no specific definition of exactly what constitutes “Massive” in Massive MIMO, the MIMO technology in 5G NR networks employs much larger antenna arrays than 4G LTE networks.
How “Massive” is 5G Massive MIMO?
The number of antenna layers in 5G Massive MIMO can be a lot higher than the MIMO in 4G LTE. It employs tens or even hundreds of antenna elements within a single antenna panel. A 64 x 64 Massive MIMO antenna configuration is already used by some 5G network vendors but 256 x 256 is also possible.
The MIMO technology is not new, and it already plays an important role in 4G LTE networks as well as modern Wi-Fi networks. However, Massive MIMO is a new enhancement that was introduced in 5G New Radio (NR) networks. The two key aspects of MIMO technology that differentiate Massive MIMO from standard MIMO are the number of antenna elements and the multi-user capability within the antenna arrays. The most advanced LTE network, LTE Advanced Pro, uses a maximum MIMO configuration of 8 x 8 which means eight antenna elements for transmission and eight for the reception. With Massive MIMO, this antenna configuration gets a lot bigger and 64 x 64 is already possible in 5G base stations from key network vendors. However, an antenna configuration of 256 x 256 is also possible. While the number of antenna elements certainly is key for Massive MIMO, the other aspect that differentiates it from standard MIMO is the multi-user capability that allows it to support multiple user devices simultaneously.
How does massive MIMO work in 5G networks?
The fundamental concept of Massive MIMO in 5G NR networks is the same as that for standard MIMO in 4G LTE networks.
Massive MIMO employs a large number of antenna elements within a single antenna panel of a 5G base station and uses spatial multiplexing, diversity and beamforming to increase network capacity, throughput and radio link quality. The additional capacity is used to serve multiple simultaneous users.
The transmitter and receiver diversity, spatial multiplexing and beamforming provide the foundation for improving signal reliability and data throughput whilst reducing interference. The additional MIMO enhancement in 5G comes from the sheer volume of antenna elements employed by Massive MIMO and the multi-user application of the antenna elements.
Transmitter and receiver diversity
Diversity is when multiple antennas are deployed at the transmitter or the receiver end to reduce the impact of signal fading. A radio signal can take many paths to travel between a transmitter and receiver. Some paths are without any obstructions, e.g. high-rise buildings, but other paths may have obstacles in the way. As a result, the different versions of the signal travelling through the various paths may fade at different rates. Diversity exploits this nature of the signal by introducing multiple antennas to capture the different versions of the signal so that they can be combined to improve the overall signal quality. The use of diversity at the receiving end is not new in mobile communications, but MIMO introduces multiple antennas both at the transmitter and the receiver. Massive MIMO in 5G networks takes the number of antennas to a whole new level. For example, a 5G Massive MIMO system with a 64 x 64 downlink configuration means 64 antenna elements at the base station (cellular tower) and 64 antenna elements at the receiving end (mobile phone’s receiver). Diversity makes the signal more robust by improving the reliability of the radio link. However, it does not improve the radio channel capacity, so the data rate or throughput is not impacted by diversity.
Spatial multiplexing and multi-user support
Spatial multiplexing is one of the most important features in MIMO systems used for improving the efficiency of the frequency channel. This improvement in spectral efficiency leads to higher overall capacity and, therefore, higher data rates. In Massive MIMO, a large number of antenna elements are separated physically in space with the ability to transmit and receive different data streams simultaneously. The overall data stream intended for a specific user can be sent over multiple individual data streams. At the receiving end, these data streams are picked up by an array of receiving antenna elements to put the various individual data streams back together as a single data stream. This process improves the data rates for an individual user. But Massive MIMO does not stop here and utilises its multi-user capability to handle data streams for many users simultaneously.
Three-dimensional (3D) beamforming
Beamforming is an advanced antenna technology that is employed by MIMO systems. It takes place when the signal transmission through multiple antenna elements is targeted in a particular direction instead of broadcasting the signal in all directions. Beamforming makes efficient use of the available transmission power to point the different beams of the signal in the desired direction. In Massive MIMO, beamforming is three-dimensional (3D beamforming), so the beams can be horizontal and vertical to improve the data rates for all users, even if they are in high-rise buildings. Beamforming extends the range of the signal by shaping the transmission such that the desired beam gets most of the transmission power to become longer whilst suppressing the other beams that are in the non-desired direction.
Benefits of Massive MIMO – Why 5G networks use Massive MIMO
Massive MIMO efficiently utilises the radio network resources to improve network capacity, leading to higher throughput and multi-user support. It uses the beamforming technique to focus the transmission power in specific directions which extends the network coverage whilst minimising interference.
Massive MIMO is one of the key enablers for the New Radio (NR) technology used in 5G networks. It improves the radio network capacity as well as the network coverage. The benefits of Massive MIMO include spectral efficiency, higher throughput, lower interference and extended range.
Spectral efficiency
Massive MIMO employs spatial multiplexing, which efficiently uses frequency and time resources to improve network capacity and, therefore, the bit rates. The different signal paths created by multiple antennas in Massive MIMO are used as sub-channels for sending and receiving data streams for multiple users.
Higher throughput
The use of multiple data streams through spatial multiplexing allows a user device to get higher overall bit rates. In addition, due to the large number of antenna elements in Massive MIMO, a lot of additional capacity is created, enabling higher throughput for multiple users simultaneously.
Lower interference
The beamforming technique provides targeted transmission of the radio signal, which makes the signal more robust in a specific direction. That way, the main beam in the desired direction becomes the strongest, and the side beams (side lobes) become weaker, which minimises any potential interference between the beams.
Extended range
Massive MIMO has three-dimensional beamforming (3D beamforming), which creates horizontal and vertical beams of the signal so that it can reach people in different ranges (distance) and heights (e.g. high-rise buildings). The beamforming technology also extends the network coverage by channelling the transmission power in a targeted direction to improve the range.
Conclusion
Massive MIMO stands for Massive Multiple Input Multiple Output, and it is an antenna technology used by 5G NR networks to improve the spectral efficiency, data rates, coverage range and capacity of 5G networks. Massive MIMO employs a large number of antenna elements (generally higher than ten) in a single antenna to support multiple user devices simultaneously.
Here are some helpful downloads
Thank you for reading this post. I hope it helped you in developing a better understanding of cellular networks. Sometimes, we need extra support, especially when preparing for a new job, studying a new topic, or buying a new phone. Whatever you are trying to do, here are some downloads that can help you:
Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy, which explains the network nodes, e.g., BTS, MSC, GGSN etc.
Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and the challenges considering how quickly the industry evolves. The bigger picture comes from experience, which is why I’ve carefully put together a few slides to get you started in no time. So if you work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on the product overview and product roadmap.
