Carrier (or channel) aggregation, which is part of the 3GPP Release 10, represents a highly effective way to dramatically increase the transmission bandwidth as LTE-Advanced is adopted. This process makes it possible for multiple conventional LTE component carriers on the PHY layer, as opposed to single carriers, to be used together to ramp up supported data rates, reduce latency and enhance spectrum efficiency.
The upshot is that mobile operators can leverage carrier aggregation in order to provide a more comprehensive range of data-intensive multimedia applications, with full backward compatibility with existing hardware being maintained and no additional costs needing to be incurred.
To achieve the desired boost in data transfer, an increase in the total transmission bandwidth compared to what can be taken care of by a single LTE component carrier is called for. The objective is to attain throughput rates of 1Gbps across the downlink and 500Mbps across the uplink by using the compounded capacity of up to five 20MHz wide component carriers at once. Trials carried out in Southeast Asia are already managing to surpass this figure.
Operators will be able to benefit from dynamic load balancing of mobile traffic over these carriers. Asymmetric operation will be required, with more carriers potentially needed in one direction than in the other.
Carrier aggregation permits greater operational agility when it comes to allocating available spectrum as the required bandwidth can be cobbled together using a number of different component carriers. It facilitates better distribution of RF coverage, as the presence of additional carriers will allow a bolstering of data rates at the heart of the cell. In addition, it means that poor coverage at the perimeter of cell can be improved.
The allocation of the spectrum can be either contiguous (with no frequency gaps between them) or non-contiguous (with gaps of several hundred kHz permissible). Contiguous is obviously the simplest form of carrier aggregation. Non-contiguous carrier aggregation can be done through the use of carriers all located in the same frequency band or in several different bands.