With the completion of LTE Release 8, 3GPP started to look into ways to further evolve LTE for the future, in order to build upon the existing LTE technology and to ensure that LTE remains the leading global standard for mobile broadband.
Enhanced performance can in principle be achieved in two ways – by using more radio spectrum, and by using the available spectrum more efficiently.
The main components of LTE-Advanced that are added to LTE in Release 10 are:
Data rates of the order of 1 Gbps might theoretically be achieved using contiguous bandwidths of 40 MHz or more. However, competition for spectrum and fragmentation of the available spectrum makes it unrealistic to expect such large contiguous bandwidths in most cases. LTE-Advanced therefore makes use of carrier aggregation to support such large bandwidths. This also has the advantages of limiting the cost of equipment and enabling much of the technology developed for LTE Release 8 to be reused. Each ‘component carrier’ within an aggregation is designed to be fundamentally similar to an LTE Release 8 carrier so that they can be configured in a backward-compatible way and used by legacy UEs if desired. Up to five component carriers with a bandwidth of up to 20 MHz each can be aggregated in LTE-Advanced to make efficient use of the available spectrum and achieve the desired total bandwidth and peak data rate.
LTE-Advanced can also make use of carrier aggregation to support deployments of heterogeneous networks consisting of a layer of macrocells and a layer of small cells coexisting with at least one carrier being common between them. In such a deployment, transmissions from one cell can interfere strongly with the control channels of another, thus impeding scheduling and signalling. LTE-Advanced supports cross-carrier scheduling to enable control signalling to be transmitted on one component carrier corresponding to data transmissions on another; in this way, control channel interference between macrocells and small cells can be avoided.
The existence of internationally identified common frequency bands is a key factor for significant economies of scale in the development and production of terminals. A key outcome of the WRC-2007 (World Radiocommunication Conference, held in Geneva in 2007), was that a total of 136 MHz of new global spectrum was allocated for use by International Mobile Telecommunication-designated radio technologies:
Other region-specific bands were also allocated:
All new bands identified by the WRC 2007 are valid generically for International Mobile Telecommunication technologies.