The Need to Simplify Carrier Aggregation Complexity

Visibility to validate performance and troubleshoot carrier aggregation functionality is imperative.


All around the world, mobile service providers are investing heavily to acquire newly allocated and reassigned spectrum licenses with the intent to grow their mobile broadband services and offer the highest bandwidth possible. To maximize their investments, many are looking to carrier aggregation (CA) techniques as a way to ultimately deliver the expected throughput to their end users. CA involves multiple radio channels being joined together to provide greater bandwidth/throughput and equalize uplink and downlink speeds.

CA actually has been around for quite some time, but it’s in the spotlight again because of the growing focus on 5G. Although carrier aggregation can maximize data rates per user, delivering on the promise of high-speed LTE and 5G services, the approach also presents new levels and layers of complexity. Because individual Radio Resource Control (RRC) sessions require support from both the user equipment (UE) and network primary cell (Pcell) and secondary cells (Scells), visibility to validate performance and troubleshoot CA functionality is necessary. With millions of LTE and 5G cells now in the mix, single-call analysis is no longer a viable or cost-effective option. 

What’s Driving the Latest Trend in CA Adoption

There are a number of factors driving the latest CA adoption trend. These include increased data speeds, which allow wireless carriers to combine multiple frequency bands to support high-quality video streaming, online gaming, and other emerging data-intensive applications such as augmented reality, and also for fixed wireless access (FWA) services. Carrier aggregation also affords enhanced network capacity, which allows more users to simultaneously connect to the network without experiencing slowdowns or congestion, even with high-bandwidth applications.

CA can improve coverage and reliability by combining a lower-band carrier for coverage and a higher-band carrier for throughput. Providers will be able to leverage CA to meet growing demands for high-bandwidth services. This approach is ideal for efficient spectrum utilization, enabling carriers to maximize the use of their licensed frequencies. It also is effective for supporting advanced technologies made by 5G high-millimeter bandwidth/low-latency radio bearers, while at the same time letting providers future-proof their offerings, enabling scalable solutions to meet the evolving throughput and latency demands of customers.

Carrier Aggregation Will Be Crucial for Maximizing ROI

As service providers incur the high cost of spectrum acquisition and massive capital expenditures to roll out networks, the need for a meaningful return on investment (ROI) is top of mind. CA offers a viable means of achieving this critical objective. Carrier aggregation’s connectivity allows providers to offer maximum bandwidth and throughput to customers, delivering on the promise of high-speed LTE and 5G services and thereby making the most of investments.

However, managing the new layers of complexity that come with additional technologies and added frequency bands is a relevant concern for service providers. Beyond investments in spectrum acquisition and infrastructure, service providers will also need to focus on controlling additional OpEx costs. This means simplifying the management of CA will be vital to address cost concerns. Compounding the challenge of maximizing carrier aggregation is that there is surprisingly little visibility into how things are working, whether it’s functioning properly and whether it’s delivering the value for which it’s been deployed.

Dual Connectivity Combined with CA Adds Additional Complexity

In some instances, service providers are combining CA with dual connectivity involving 4G and 5G or 5G and 5G. In such cases, rather than having a master cell, the provider has a master cell group or secondary cell group, which means a group of carriers that are being used to deliver the service. This adds a further level of complexity overlaid on the CA.

One of the applications of dual connectivity is to provide fixed-wireless assets where the main connection provides basic connectivity and the high-millimeter frequencies provide the high-capacity access data rate required for a specific application. The challenge of this approach is that when the secondary carrier goes down, all others go down as well, leaving only the primary carrier to deliver the service.

Within this complex radio frequency environment, various challenges arise, such as component carriers interfering with each other and resulting in a reduced data rate. In extreme cases, this interference can even lead to a drop in the secondary component carrier. Compatibility on the device side and on the network side is another concern.

Signal strength is also a concern. With different bands at different frequencies, offering different powers, gains, and patterns such as higher path loss for higher bandwidth and lower loss for lower bandwidths, the result can create an imbalance in signal power between primary and secondary cells. This can end up with the UE not being able to make use of the full capacity of all the component carriers.
The Greater the Complexity, the Greater the Need for Visibility

As briefly outlined here, carrier aggregation comes with enormous complexity, which creates a tremendous need for effective visibility into the network. Service providers need to know if there is any capacity left unused with CA and what issues are generating drops or failures, involving either secondary cells or the primary cell. Ultimately, providers need to fully understand what issues are responsible for generating a poor quality of experience for the end customer.

This means providers need a deep understanding of how CA is operating—from band combination being used, to the handsets and their capabilities and functionality, to the performance of the network itself. Obtaining three-dimensional visibility is essential.

Service providers need to be able to monitor the interactions between the handsets and the cell for every band combination. The best source of information for this is the individual radio sessions provided by the network itself via a standardized transport interface from either the eNodeB or the gNodeB (see figure). Cell trace record (CTR) transport information from eNodeB and gNodeB has proved to be the best source of information by far over time for RAN assurance in general. The problem with this approach is that if you start on a call-by-call layer, you end up with a huge amount of transaction data.

Analytics with cell band and device types.

The best practice is to utilize a combination of analytics with cell band and device types that surface issues and provide enough detail for effective root cause analysis. Such data can be exported and used together with any other data source in a customer data lake for further analysis. Greater efficiency can be achieved by introducing automation. Even with a compact, smart dataset, providers are still potentially looking at data from multiple combinations and millions of cells. Automation can enable optimization of the analysis, empowering providers to crunch this data and surface the issues for smart outcomes.

At the same time, automation allows for the optimization of costly and complex carrier aggregation and dual-connectivity environments. Machine learning and artificial intelligence (AI) algorithms can process a lot of data automatically and deliver actionable business intelligence. Such advanced solutions replace human analysis, which is slow and prone to errors. Automation is key to achieving smart outcomes.

A Smart Solution for Smart Outcomes

NETSCOUT has made it possible to simplify CA complexity. Our RAN Analytics for Carrier Aggregation Performance Analysis addresses the challenges of managing CA effectively. With Kafka export capabilities, stand-alone reporting options, and the enablement of CA-specific metrics for existing RAN solution deployments, mobile operators and RAN engineers have the visibility they need to identify, investigate, and take action on the issues impacting CA performance success and bandwidth utilization efficiencies. Because UE modems provide hundreds of band capabilities, carrier service providers need a clear picture of the availability and per-cell CA utilization in the network. RAN Analytics for Carrier Aggregation provides this view with networkwide utilization and performance metrics, UE capability reports, and the overall status of the radio frequency (RF) environment.

Embracing CA to ensure a better quality of service for end customers can prove to be a competitive advantage. Gaining sufficient visibility to deliver that quality is the key.

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