The 5G New Radio (NR) Release 16 builds on the foundation put in place by the Release 15, raising the bar on latency and bandwidth while adding other capabilities. The 5G specification for carrier aggregation (CA) and dual connectivity (DC) will enable increasing data rates for different frequency ranges and operation modes, but how big of an increase are we talking about? Also, are there other updates contributing to the increase in system capacity for 5G?
This article summarizes the content of the latest 3rd Generation Partnership Project (3GPP) standard release, explains key concepts like CA and DC, and with examples, quantifies the data rate increase between Release 15 and 16. You will also obtain a glimpse into the challenges these trends bring to you and your solutions.
Release 16 in a nutshell
Release 16 is a collection of enhancements over Release 15. The release also extends 5G’s reach into new verticals with features like NR unlicensed (NR-U), NR vehicle-to-everything (V2X) sidelink, and support for the industrial Internet of Things (IIoT).
The release increases CA capabilities at frequency range 1 (FR1) that goes from 410 MHz to 7.125 GHz and frequency range 2 (FR2) which covers millimeter-wave (mmWave) frequencies. Release 16 brings many new band combinations in both FR1 and FR2, with mobile network operators refarming bands and increasing the number of services they offer. There are also multiple-input/multiple-output (MIMO) enhancements, including downlink modulation for 256 quadrature amplitude modulation (QAM) at FR2.
Figure 1 provides a summary of the key features of 3GPP Release 16.
Figure 1 The 3GPP Release 16 brings capacity and operational enhancements while extending 5G’s reach into new verticals. Source: Keysight Technologies
The CA and DC concepts
One of the key goals of Release 16 is to increase data rates for different frequency ranges and operation modes. Differentiating CA from DC is important in understanding how Release 16 achieves this goal. Both combine the throughput of multiple component carriers. The difference lies in the base stations the component carriers come from. In the case of CA, the same base station generates the signal from the component carriers. With DC, different base stations generate the signal. This factor impacts the throughput taking shape in the protocol stack, as shown in Figure 2.
Figure 2 Both CA and DL combine the throughput of component carriers, but at different layers in the protocol stack. Source: Keysight Technologies
There are also many flavors of CA and DC. The 4G wireless allows the transmission of a single component carrier and provides CA and DC capabilities. On the other hand, 5G offers the same capabilities in standalone (SA) mode, but depending on the frequency range, there are aspects to take into consideration. In addition, 5G allows the combination of one or multiple component carriers in NR, with one or more component carriers in DC. This capability generates a huge number of potential combinations.
Figure 3 The 4G and 5G technologies provide a range of CA and DC options. Source: Keysight Technologies
In addition, there are differences in frequency spectrum that apply in both CA and DC. Band combinations can be intra-band contiguous, intra-band non-contiguous, or inter-band. Intra-band contiguous means that the different component carriers are together in the spectrum. Intra-band non-contiguous means that there is at least one gap between the component carriers, but they are in the same frequency band. Inter-band means that a component carrier can be in one band and the other ones in a different band.
Figure 4 The CA and DC techniques use three types of band combinations. Source: Keysight Technologies
Lastly, remember that different 5G network architectures use DC. Figure 5 shows the top four options. Option 2 uses the 5G core network (5GC). In non-standalone (NSA) mode, Option 3 uses the evolved packet core (EPC) network. The 4G base station is in charge of the control plane to communicate with the device, but there can be one data plane from LTE and one from NR. In Option 4, the 5GC with the 5G base station handles the control plane.
Figure 5 The 5G technology offers four main architecture options for DC. Source: Keysight Technologies
Quantifying Release 16’s data rate increase
With these key concepts in mind, let’s now focus on the key question of this article: data rate increase. Starting with FR1, the aggregated bandwidth increases from 200 MHz in Release 15 to 300 MHz in Release 16 for intra-band contiguous combinations.
Release 16 also includes uplink and downlink CA for intra-band non-contiguous combinations and adds inter-band DC within FR1 (Release 15 only featured DC between FR1 and FR2).
At FR2, Release 16 increases the frequency separation class from 1.4 GHz to 2.4 GHz for intra-band non-contiguous combinations. The release also adds asymmetric bandwidth on the downlink with a frequency separation class that is contiguous to the symmetric bandwidth and uplink CA.
Release 16 also features downlink CA for FR2 inter-band combinations. This new capability poses a significant challenge, because it requires handling the independent beams coming from the different component carriers.
Overall, Release 16 increases the number of band combinations and their complexity across both FR1 and FR2, but also by combining FR1 and FR2. However, what does that mean in terms of data rates exactly?
Example 1: Intra-band non-contiguous standalone CA FR2
Let’s take the intra-band non-contiguous standalone CA FR2 case with the following conditions:
- 120-kHz sub-carrier spacing
- 400-MHz channel bandwidth per component carrier
- MIMO 2X2 communication
- Time division duplex (TDD) slot format 28 to maximize downlink throughput
In Release 15, the maximum band combination for this case is the CA-n260(3A) band combination. The combination allows for three component carriers in the same frequency band with at least one gap between them. Since Release 15 has a maximum channel bandwidth of 400 MHz, you can achieve a total aggregated bandwidth of 1.2 GHz. A maximum frequency separation class of 1.4 GHz enables a maximum modulation of 64QAM, resulting in a maximum throughput of about 9 Gbps.
With the same conditions, Release 16 can more than double this throughput. The band combination changes to CA-n260(6A), allowing for six component carriers and enabling the total aggregated bandwidth to increase to 2.4 GHz. Using a maximum frequency separation class of 2.4 GHz and 256QAM modulation, system capacity increases drastically to a maximum throughput of 24 Gbps.
Impressive, but FR2 standalone deployments are not common yet and it is challenging for devices to support a maximum bandwidth of 400 MHz. However, even in the non-standalone architecture, the throughput increase in Release 16 is noteworthy.
Example 2: Intra-band non-contiguous NSA DL
Keeping the same sub-carrier spacing—MIMO 2X2, and slot-format configuration as in the previous example, and only changing the channel bandwidth per component carrier to 100 MHz—the maximum throughput in Release 16 is still more than twice that of Release 15.
With these conditions, the band combination becomes DC_2A-n260(4A) for Release 15. This combination allows for four component carriers, translating to a total aggregated bandwidth of 400 MHz. Using the maximum frequency separation class of 1.4 GHz and 64QAM modulation, the maximum throughput only reaches about 3 Gbps.
With Release 16, the band combination becomes DC_2A-n260(8A). This band combinations allows for eight instead of four component carriers, and therefore an achievable aggregated bandwidth of 800 MHz. Using a maximum frequency separation class of 2.4 GHz—instead of 1.4 GHz and 256QAM modulation—the maximum throughput now reaches 8 Gbps.
Release 16 design challenges
Whether for SA or NSA mode, Release 16 increases system capacity drastically. However, complexity also increases exponentially because the number of band combinations is greater, there are more component carriers, and the number of bands is also higher.
At FR1 SA mode, the number of combinations grow for all CA types—intra-band contiguous, intra-band non-contiguous, and inter-band—but especially for inter-band. Inter-band combination is more than 12 times that of Release 15.
In NSA mode, the number of band combinations defined in Release 16 is more than four times the number of band combinations in Release 15, growing from about 900 to more than 4,000 for inter-band combinations. Complexity also grows exponentially with the number of component carriers with up to 6 different bands in the same band combination.
At FR2, the increase is even greater because there is more spectrum available at these frequencies. The number of component carriers that you can combine in NSA mode reaches 17 DL component carriers. There is an increase as well in SA mode with some bands defined in Release 16, which will grow further with Release 17.
Also, there are more band combinations in FR1+FR2 cases. For CA, the number of band combinations is more than 25 times that of Release 15, and the number of component carriers you can aggregate reach up to 10 on the downlink or 9 on the uplink. For NSA, the number of band combinations increases from about 300 to more than 9,000 in Release 16.
This complexity brings new challenges. Engineers will need to handle higher frequencies and higher bandwidths. Filter design and performance optimization becomes more complex with Release 16. Engineers will need to handle multiple component carriers, sometimes in different bands, and the high throughput in the protocol stack. If you are working on FR2 inter-band downlink CA cases, you will need to manage beams independently, and if you are working on MIMO enhancements, you must handle multiple antenna panels.
Solutions to overcome these challenges exist. They cover the entire device workflow and span all test domains—protocol, RF, and performance metrics. Qualcomm and MediaTek, for example, recently used Keysight’s S8701A Protocol R&D Toolset to manage spectrum requirements in 5G CA. You can view a demo video of Qualcomm’s handling of Release 16 in the webinar CA, RF & mmWave Advances with 5G Rel-16.
Jessy Cavazos is part of Keysight’s Industry Solutions Marketing team.
Other articles in this 5G series:
- 3GPP Release 16: What are the key enhancements and new features?
- O-RAN challenges from the overhaul
- O-RAN is transforming 5G network design and component interoperability
- The aspects of 6G that will matter to wireless design engineers
- 5G’s Release 16: The Essentials
- 5G Takes to the Stars
- 5G is coming on-stream, fast
- 5G roll-out: a marathon not a sprint
- Mastering 5G test complexity: a growing concern
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