An Overview of Pilot Contamination & Energy Efficiency in Massive MIMO Systems

The increasingly scarce spectrum resources and the rapid growth of the energy consumption set frontward higher requirements on the next-generation wireless communication system known as the 5G system. In wireless communication, this upcoming emerging large-scale MIMO technology became a very hot subject as it scales up conventional MIMO technology by order of immensity in contrast with the present state of the art. As a key technology of 5G, the large-scale MIMO system will increase the spectrum quality and power efficiency significantly just by constituting the large antenna arrays in the BS. Compared to multi-user antennas built for LTE mobile communication system that permits only eight antennas on a BS, the new upcoming technology Massive MIMO offers unlimited antennas opening a new direction for research in the field of wireless communication. Each base station with hundreds of antennas needs precise information of CSI. The CSI information for massive MIMO is vital to improve energy efficiency and to reduce pilot contamination caused by limited orthogonal pilots and inter-cell interference to improve system stability and performance. This latter explicates pilot contamination and energy efficiency by specifying an extensive survey. To make the system more efficient and expedient, this paper suggests some useful key points for future research.