Carrier aggregation is one of the most important features of HSPA+, bringing higher data rates, higher capacity for bursty application, and enhanced broadband experience for all users. Carrier aggregation continues to evolve to support more carriers, more bands, aggregation in the uplink.
Carrier aggregation brings higher data rates, higher capacity for bursty applications such as browsing, and an enhanced broadband experience for all users. HSPA+ commercialized the first step, aggregation across two carriers (aka dual-carrier) back in 2010, as part of Rel. 8. Carrier aggregation has been evolving since then, bringing it to the uplink, more carriers in the downlink, more bands, aggregation with unpaired spectrum and more.
Dual-carrier supporting two carriers in the downlink was introduced in Rel. 8. Ever since its commercial launch in 2010, it has spread rapidly and was deployed in about 160 network worldwide, as of early 2014. Carrier aggregation has evolved strongly to bring across bands and uplink aggregation in Rel. 9, 3 and 4 carriers in Rel. 10, followed by non-contiguous bands, up to 8 carriers and aggregation across cells (called as MultiFlow) in Rel. 11. A special-case called supplemental down link (SDL), enabled by Rel. 9, aggregates unpaired spectrum with the downlink of paired spectrum.
Carrier aggregation not only increases the peak data rates, but also increases date rates for all users, proportional to number of carriers being aggraded, for example, doubled rates for two carriers and quadrupled for four carriers.
The higher data rates of carrier aggregation can also be traded off to offer more capacity for bursty applications (e.g twice or more for two carriers), while maintaining the same user experience, under typical network loading conditions. As evident, when carriers are aggregated, there are more resources, but due to trunking efficiency the overall capacity can be much more than the sum total of the capacity of the individual carriers. The increased capacity will help operators to address bursty smartphone traffic as well as increased use of social media applications, instant messaging and others.
HetNet features such as small cell range expansion that are possible today leverage carrier aggregation. Taking it further, MultiFlow allows users to select the best link from multiple cells. For example, users can aggregate the Range Expansion carrier from the small cell and the primary carrier from the macro so that they benefit from the better capacity of the former and better coverage of the latter. This results in better utilization of small cells, more traffic offload from macros and increase in data rates for all users.
Qualcomm Technologies has introduced chipset solutions that support the strong evolution of HSPA+ carrier aggregation evolution. Our common LTE/HSPA+ platforms solution support aggregation of up to three HSPA+ carriers in the downlink, two carriers in the uplink as well as support aggregation across bands (e.g. 2.1GHz and 900MHz).