An Efficient Hybrid Pilot design for Channel Estimation in Massive MIMO Systems

In wireless communication systems, the pilot sequences have a significant impact on system performance, in particular, the channel estimation (CE) process. Thereby, this work addresses the CE process in fifth generation (5G) wireless communication systems (i.e., in Massive multiple-input and multiple-output systems) using different pilot designs (i.e., regular pilots (RPs), superimposed pilots (SuPs), and proposed hybrid pilots). In this work, we propose an efficient hybrid pilot design that combines the best features of both pilots (i.e., superimposed and RPs), since users that use RPs at the cell-edge are strongly affected by pilot contamination, whereas users that use SuPs and are close to the BS are strongly influenced by the interference coming from transmitting data and pilot together. Therefore, the hybrid pilot design is proposed to overcome the drawback of both pilot designs. We provide numerical results to assert our theoretical expressions.