Effective Carrier Aggregation on the LTE-Advanced Systems

The initial release of LTE provided extensive support for deployment in spectrum allocations of various characteristics, with bandwidth ranging roughly from 1.3 MHz up to 20 MHz in both paired and unpaired bands. In LTE release 10 the transmission bandwidth can be further extended by means of so-called Carrier Aggregation (CA), where multiple component carriers are aggregated and jointly used for transmission to/from a single terminal. There are up to five component carriers, possibly each of different bandwidth, which can be aggregated, allowing for transmission bandwidth up to 100 MHz backwards compatibility where, each component carrier (CC) uses the release-8 structure. Hence, to a release-8/9 terminal, each CC will appear as an LTE release-8 carrier, while a carrieraggregation capable terminal can exploit the total aggregated bandwidth, enabling higher data rates. In general case, a different number of component carriers can be aggregated for the downlink and uplink. Therefore, this paper highlights the carrier aggregation which supports the inter-band aggregation contiguous component carriers, intra-band aggregation non-contiguous component carriers and inter-band aggregation. This paper also presents the enhancement of LTE spectrum flexibility through carrier aggregation, further extension of multi-antenna transmission and provision of improvements in the area of inter-cell interference coordination in heterogeneous network deployments.