Abstract— Carrier aggregation (CA) and spatial multiplexing (SM) multiple input multiple output (MIMO) antenna systems are used in the 4G and beyond wireless systems to achieve the desired data rates. This paper investigates the performance of the inter-band CA and SM MIMO in LTE-Advanced and recommends a CA scenario that leads to both efficient use of the MIMO antenna elements and balanced transmit power of the component carriers (CCs). The study is performed in an urban environment considering many eNodeB-UE links at CCs of 800 MHz and 2.6 GHz for different combinations of single and multiple-antenna systems. An urban site-specific 3D ray-tracing tool combined with measured antenna 3D radiation patterns is used to model radio channel of eNodeB-UE links. The simulation results show dependency of the aggregated throughput performance on the number of aggregated spatial streams and cell radius. For enhanced performance, this paper recommends aggregating either 4×4 SM MIMO operating at 800 MHz with 1×1 antenna system operating at 2.6 GHz for a cell radius of 450 m or, alternatively, 4×4 SM MIMO operating at 800 MHz with 2×2 SM MIMO operating at 2.6 GHz for a cell radius of 350 m.