Enhanced Carrier Aggregation

Enhanced Carrier Aggregation (eCA) is a 3GPP release 13 enhancement to the carrier aggregation technology to increase the number of aggregated carriers from 5 to up to 32 carriers and dramatically improve the data rate experienced by the end users. This enhancement entails other modifications including transmission of uplink control information on a non-primary carrier (known as secondary PUCCH cell) and other related modifications.

Carrier Aggregation Timeline

The basic carrier aggregation (CA) feature was added to the LTE Release 10 enabling aggregation of up to 5 carriers of the same frame structure. Carrier aggregation was further enhanced in releases 11 and 12 enabling inter-band TDD CA with different UL-DL configurations, CA with multiple UL timing advances and aggregation of carriers with different frame structures.

CA Timeline-02

Carrier Aggregation Beyond 5 Carriers

With the LAA (Licensed-Assisted Access) in horizon during the LTE release 13 standard development, extending the LTE carrier aggregation feature towards capturing the spectrum opportunities of unlicensed spectrum in the 5GHz band created a lot of interest. 3GPP Release 13 introduced the carrier aggregation enhancement beyond 5 carriers and up to 32 carriers.

CA Beyond 5-02

PUCCH on Secondary Cell

In legacy carrier aggregation, the transmission of uplink control information for all the aggregated carriers takes place on a physical uplink control channel (PUCCH) of a primary carrier. The increased number of aggregated carriers leads to overloaded PUCCH of the primary carrier. With the eCA technology, support of PUCCH on a secondary carrier in addition to the primary carrier was introduced.


Primary and Secondary PUCCH Cell Group

With eCA, the carriers used by a wireless device, for the purpose of uplink control information transmission, are grouped into a primary PUCCH group whose control information are transmitted on the PUCCH of the primary carrier and a secondary PUCCH group whose control information are transmitted on the PUCCH of a secondary carrier (called PUCCH secondary carrier).



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