Carrier aggregation is a technique used in wireless communication to increase the data rate per user, whereby multiple frequency blocks (called component carriers) are assigned to the same user. The maximum possible data rate per user is increased the more frequency blocks are assigned to a user. The sum data rate of a cell is increased as well because of a better resource utilization. In addition load balancing[is possible with carrier aggregation. Channel selection schemes for CA systems taking into account the optimal values for the training length and power, the number of the probed sub-channels and the feedback threshold such that the sum rate is also important for optimal achievable capacity.
Depending on the positions of the component carriers three cases of carrier aggregation are distinguished:
The case where the component carriers are contiguous in the same frequency band is called intra-band contiguous carrier aggregation.
If the component carriers are in the same frequency band but are separated by a gap the carrier aggregation is called intra-band non-contiguous.
The most complex case is when the component carriers lie in different frequency band. This is called inter-band carrier aggregation applied to heterogeneous networks.
There is no difference between these three cases from a baseband perspective. However, the complexity from an RF point of view is increased in the case inter-band carrier aggregation.
