Smart macro network enhancements: Carrier aggregation (part 1)

The various macro network enhancements available today offer a cost-efficient and smart approach to capacity increase. To make the most of these investments, however, it is vital to continuously measure the capacity before and after changes have been made – at best with measurement and test solutions that depict capacity and performance from a real end-user perception.

Before exploring the role of mobile network testing in enabling operators to make well-informed decisions about appropriate technologies, this article series explains in 3 parts the various “smart macro network enhancements” by describing the:

• fundamentals of the technological approach
• challenges that operators are facing during capacity enhancement projects
• tools to support operators with these tasks

The hardware-related capacity enhancing features discussed in this series include carrier aggregation (CA), antenna tilt optimization, and 4×4 MIMO.

Carrier aggregation

This post’s focus is on carrier aggregation – without a doubt, today’s most important LTE-Advanced feature. This post has originally be written in LTE times, but the feature itself is as well used in 5G. Nowadays, a base station can allocate one or more 5G carriers plus 2 to 5 LTE carriers to one data transmission in downlink direction to one user / UE. Carrier aggregation is also used to a certain extend in uplink direction, but here the smartphone Tx power / energy (battery consumption) is a limiting factor. The aim is to increase the peak data rate per user significantly. Users may get their data transmitted much faster so that resources are freed up for others.

Apart from this bundle gain, however, carrier aggregation is not a true capacity enhancement feature. As we understand it, capacity enhancement transmits more data over the same amount of air interface resources. With carrier aggregation, the cell capacity is undoubtedly increased, but rather by investing in more spectrum (i.e., more air interface resources).

Carrier aggregation ecosystem

Carrier aggregation is neither a big problem for mobile network testing nor the base station hardware since the hardware is often prepared for bandwidths of a few 100 MHz. The user equipment ecosystem and chipset capabilities defined by the 3GPP standard are also not a limitation anymore compared to the first years of LTE.

Todays smartphone chipsets all support a variety of capabilities in terms of aggregated carriers, MIMO schemes (2×2, 4×4), and modulation and coding schemes such as 64QAM or 256QAM. And all commercial devices use carrier aggregation to achieve high downlink data rates.

Rohde & Schwarz mobile network testing supports all major commercially available smartphones as LTE and 5G test devices (incl. our QualiPoc Android platform), which support all kinds of carrier aggregation combinations.