In the case of inter-band carrier aggregation the component carriers will experience different pathloss, which increases with increasing frequency. The different serving cells may have different coverage.ĭifferent component carriers can be planned to provide different coverage, i.e. Carrier Aggregation Primary and Secondary serving cells.Įach component carrier corresponds to a serving cell. The SCCs are added and removed as required, while the PCC is only changed at handover.įigure 3. The other component carriers are all referred to as Secondary component carriers (DL and UL SCC), serving the Secondary serving cells, see figure 3. In idle mode the UE listens to system information on the DL PCC. It is also on the DL PCC that the UE receives NAS information, such as security parameters. The RRC connection is only handled by one cell, the Primary serving cell, served by the Primary component carrier (DL and UL PCC). The coverage of the serving cells may differ, for example due to that CCs on different frequency bands will experience different pathloss, see figure 3. When carrier aggregation is used there are a number of serving cells, one for each component carrier. For example, in R12 configurations for UL inter-band CA configuration will be introduced. In later releases more configurations will be added. Also for inter-band CA there will only be ONE UL CC, i.e. Note also that for both R10 and R11 any UL CC will have the same bandwidth as the corresponding DL CC. The maximum aggregated bandwidth is still 40 MHz and maximum number of CC is 2.
In R11 a large number of additional CA configurations are defined, see table 2. In R10 three CA configurations are defined, see table 1. CA configuration: indicates a combination of E-UTRA operating band(s) and CA bandwidth class(es), to exemplify the configuration CA_1C indicates intra-band contiguous CA on E-UTRA operating band 1 and CA bandwidth class C, CA_1A_1A, indicates intra-band non-contiguous CA on band 1 with a one CC on each side of the intra-band gap, finally CA_1A-5B indicates inter-band CA, on operating band 1 with bandwidth class A and operating band 5 with bandwidth class B.In R10 and R11 three classes are defined:Ĭlass A: ATBC ≤ 100, maximum number of CC = 1Ĭlass B: ATBC ≤ 100, maximum number of CC = 2Ĭlass C: 100 < ATBC ≤ 200, maximum number of CC = 2 CA bandwidth class: indicates a combination of maximum ATBC and maximum number of CCs.Aggregated Transmission Bandwidth Configuration (ATBC): total number of aggregated physical resource blocks (PRB).To specify different CA combinations some new definitions are used: For non-contiguous cases the CCs are separated by one, or more, frequency gap(s).įor practical reasons CA is initially specified for only a few combinations of E-UTRA operating bands and number of CCs. The spacing between the centre frequencies of two contiguous CCs is Nx300 kHz, N=integer. Carrier Aggregation Intra-band and inter-band aggregation alternatives. the component carriers belong to the same operating frequency band, but have a gap, or gaps, in between, or it could be inter-band, in which case the component carriers belong to different operating frequency bands, see figure 2.įigure 2. For non-contiguous allocation it could either be intra-band, i.e. This might not always be possible, due to operator frequency allocation scenarios. The easiest way to arrange aggregation would be to use contiguous component carriers within the same operating frequency band (as defined for LTE), so called intra-band contiguous. For TDD the number of CCs as well as the bandwidths of each CC will normally be the same for DL and UL. The individual component carriers can also be of different bandwidths. However, the number of UL component carriers is always equal to or lower than the number of DL component carriers. In FDD the number of aggregated carriers can be different in DL and UL, see figure 1. The component carrier can have a bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz and a maximum of five component carriers can be aggregated, hence the maximum aggregated bandwidth is 100 MHz. The CCs can be of different bandwidths.Įach aggregated carrier is referred to as a component carrier, CC. Carrier Aggregation (FDD) The LTE-Advanced UE can be allocated DL and UL resources on the aggregated resource consisting of two or more Component Carriers (CC), the R8/R9 UEs can be allocated resources on any ONE of the CCs.