LTE Advanced: 3GPP Solution for IMT-Advanced

14.2 Multicarrier Evolution

The most straightforward way of increasing the data rates is to use more bandwidth. Dual cell (dual carrier) HSDPA (DC-HSDPA) in Release 8 uses two adjacent carriers in downlink to push the data rates up twofold. DC-HSDPA networks were widely launched during 2011. The bandwidth can be further increased to 20 MHz in Release 10 by using four carriers and even to 40 MHz in Release 11 with eight carriers. The uplink dual cell was included in Release 9 specifications. The multicarrier evolution is illustrated in Figure 14.1.

Figure 14.1 Multicarrier evolution.

Operators have deployed multiple carriers in their networks almost from the very beginning of WCDMA for capacity reasons. Harnessing the already-deployed multicarrier infrastructure to delivering data to one user is a cost-efficient way for increasing the system peak data rates. The spectrum utilization is also significantly improved because it is possible to efficiently balance the loading between carriers and reduce the probability that some carriers don't see any loading while some other carriers are fully utilized due to a momentary high-data rate download. Multicarrier links also enable frequency domain scheduling, providing system gains even if all carriers in the system are fully utilized. Notably the system benefits of improved spectrum utilization, more dynamic load balancing and frequency ...