LTE-Advanced was introduced to meet the world’s demand for faster data delivery and increased coverage. In order to achieve target performance metrics for LTE-Advanced (as defined in the 3GPP's TR 36.9131), both the uplink and downlink require more than 20 MHz of bandwidth to achieve these targets. However, finding sufficient contiguous spectrum is usually not an option for those deploying LTE & LTE-Advanced.
Carrier aggregation enables those high data rates to be met by aggregating multiple Release 8 carriers to support transmission bandwidths of up to 100 MHz. Carrier aggregation permits the LTE radio interface to be configured with up to five "component carriers" of any bandwidth.
This paper provides an overview of carrier aggregation, discusses the impacts of carrier aggregation implementation on relevant protocol layers, and explains the implications of carrier aggregation on mobile device testing.