NTT Docomo is proposing a new Advanced C-RAN architecture that uses small "add-on" cells for localized coverage that act in concert with macro cells in HetNet fashion. Deep integration is achieved using carrier aggregation technology, one of the main LTE-Advanced technologies standardized by 3GPP.
Under the Advanced C-RAN architecture, high-capacity base stations utilizing advanced C-RAN architecture will serve as master base stations both for multiple macro cells covering broad areas and for add-on cells in smaller, high-traffic areas. The base stations will accommodate up to 48 macro and add-on cells at launch and even more later. Carrier aggregation will be supported for cells served by the same base station, enabling the flexible deployment of add-on cells. In addition, maximum downlink throughput will be extendible to 3Gbps, as specified by 3GPP standards.
Carrier aggregation is expected to yield 3 Gbps maximum throughput by aggregating multiple carriers of up to 100 MHz of carrier bandwidth.