Pico-eNB Tx Power Optimization for Multiband HetNets with MCS Incorporating 1024-QAM

The use of high carrier frequencies having wide bandwidth is expected to achieve high data rates in fifth-generation mobile systems and beyond. In heterogeneous networks (HetNets) that combine with macrocells and picocells in the same coverage area, picocells operating with high carrier frequencies are typically overlaid on macrocells using low carrier frequencies. A key technology for increasing data rates includes higher-order modulations such as the 256- and 1024-quadrature amplitude modulation (QAM). In this research, using a modulation and coding scheme (MCS) that incorporates 256- and 1024-QAM, we investigate the optimal transmission (Tx) power of a pico-evolved node B (eNB) for multiband HetNets combined with a macro-eNB using a carrier frequency of 2 GHz and pico-eNB having a wider signal bandwidth using 4.5 GHz. Under the assumption that the signal bandwidth of the pico-eNB is 10 times wider than that of the macro-eNB, we clarify the average and 5-percentile user throughput as a function of Tx power of the pico-eNB using system-level computer simulations. Based on these results, we confirm that the Tx power of the pico-eNB of 37 dBm can provide the best performance when the Tx antenna height is 10 m and the number of pico-eNB is four per macro-sector. Furthermore, it is shown that the use rate of both 256- and 1024-QAM in the downlink MCS reaches 11% when the Tx power is 37 dBm. This study will provide a remarkably effective solution for deciding the optimal Tx power of pico-eNB in multiband HetNets.