Proposal of cross-carrier precoding for carrier aggregation enhancement

Carrier aggregation (CA) has been adopted in order to ensure wide bandwidth for high-speed data communications in Long-Term Evolution (LTE)-Advanced. In most existing reports related to the CA technique, processing on the physical (PHY) layer is operated per component carrier (CC). This is because the independence of each CC in the PHY layer is assumed to maintain backward compatibility with the LTE system. In this case, the frequency diversity gain will be limited by the bandwidth of each CC. In this paper, we propose an effective precoding operation called cross-carrier precoding (CCP), in which the precoding operation is executed across CCs transmitted on different frequency bands for further enhancement of CA. By applying CCP, the modulated symbols are spread over different frequency bands resulting in a significant frequency diversity gain. The results of numeric computer simulations show that the required SNR for obtaining a PER of 1% is reduced at most by 3.5 dB in the vehicular A model and 2.5 dB in the typical urban model by applying CCP.