What is the difference between MIMO and carrier aggregation?

Modern cellular networks, including 4G LTE and 5G NR, use a range of capabilities to improve data rates for mobile users. MIMO and carrier aggregation are two such capabilities that enhance the overall network capacity, which results in higher data rates. MIMO-Multiple Input Multiple Output improves data rates through smart antenna technology, whereas carrier aggregation achieves its goals by making the best use of available frequency carriers.

MIMO (Multiple Input Multiple Output) combines signals and data streams from multiple antennas to improve signal quality and data rates, whereas Carrier Aggregation (CA) combines multiple frequency carriers (channels) to enhance the bandwidth and data rates. 4G and 5G networks use both techniques.

How do we define carrier aggregation?

Carrier Aggregation, often abbreviated as CA, allows mobile networks to combine multiple frequency carriers into one to increase the channel bandwidth, resulting in higher data rates for users. For example, suppose a mobile operator has two frequency carriers of 10 MHz each within the same base station (eNodeB – eNB). In that case, they can combine the two carriers to increase the overall bandwidth to 20 MHz (10 MHz + 10 MHz). The aggregated carriers can then be assigned to a user device to generate higher data rates for mobile users.

Carrier aggregation in 4G LTE networks

4G LTE networks have flexible carrier bandwidths, and they support the bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. Even though the original LTE networks did not support carrier aggregation, this capability was introduced as part of LTE-Advanced. LTE-Advanced networks allow aggregation of up to five (5) carriers, which means that five carriers can be combined into one to support a single user device. As the maximum bandwidth of an individual channel in LTE is 20 MHz, this essentially means that LTE-Advanced networks can achieve a maximum carrier bandwidth of 100 MHz (20 MHz x 5) through carrier aggregation. LTE-Advanced Pro networks can support carrier aggregation of up to 32 carriers, leading to a maximum bandwidth of 640 MHz (20 MHz x 32). Check out our dedicated post on carrier aggregation for 4GLTE networks to learn more.

MIMO in 4GLTE and 5G NR

MIMO is separate from carrier aggregation, and instead of combining frequency carriers, it utilises the existing frequency and time resources efficiently to improve achievable data rates. While carrier aggregation assigns multiple frequency carriers to user equipment (e.g. a 4G phone), MIMO uses multiple antenna elements at the transmitter to send several parallel data streams to the receiver. The receiver in MIMO is also equipped with multiple antenna elements to receive the data streams. The output for a user device is created by combining the various data streams. That way, each data stream acts as a virtual channel between the base station and the user device. The latest 4G LTE-Advanced networks use a MIMO configuration of 8×8 in the downlink (base station to the mobile device), which means eight antenna elements for transmitting and eight for receiving. The uplink, which is from the mobile device back to the station, uses a lower configuration. 5G New Radio (NR) networks use an enhanced variant of MIMO called Massive MIMO, which is the multi-user flavour of MIMO with tens or even hundreds of antenna elements at the transmitter and receiver.

Conclusion

In conclusion, MIMO-Multiple Input Multiple Output is an antenna technology used by modern wireless networks, including 4G LTE and 5G NR that employs multiple antennas at the transmitter and the receiver to improve data rates for a user device. Carrier aggregation is a separate technology used in 4G LTE and 5G NR networks that combines multiple frequency carriers to increase the overall carrier bandwidth and achievable data rates.

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 some extra support, especially when preparing for a new job, studying a new topic, or maybe just 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.

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