Carrier aggregation framework in 3GPP LTE-advanced [WiMAX/LTE Update]

Carrier aggregation is one of the most distinct features of 4G systems including LTEAdvanced, which is being standardized in 3GPP as part of LTE Release 10. This feature allows scalable expansion of effective bandwidth delivered to a user terminal through concurrent utilization of radio resources across multiple carriers. These carriers may be of different bandwidths, and may be in the same or different bands to provide maximum flexibility in utilizing the scarce radio spectrum available to operators. Support for this feature requires enhancement to the LTE Release 8/9 PHY, MAC, and RRC layers while ensuring that LTE Release 10 maintains backward compatibility to LTE Release 8/9. This article provides an overview of carrier aggregation use cases and the framework, and their impact on LTE Release 8/9 protocol layers.