چكيده به لاتين
In recent years, wireless communication systems have been widely investigated. The growing demand for services has brought about an increasing demand for further research in this area. Massive multiple input multiple output (MIMO) technology is one of the key technologies proposed for the fifth generation (5G) of cellular communications networks, which greatly improves spectral efficiency and energy efficiency (EE). Also, by using this technology, one can support a lot of users in the same time-frequency resources.
One of the domains studied in the massive MIMO systems is to investigate the effect of channel aging. Due to the large number of antennas, the presence of small differences in estimated coefficients and real channel coefficients, a distinct loss in system performance is inevitable. Because of importance of the effect of channel aging, many papers have been published where most of them investigate this effect by considering SE and time division duplexing metrics.
In this thesis, first the EE of the frequency division duplexing (FDD) massive MIMO systems is investigated. It is shown that channel aging causes decrease in EE. Then three methods are proposed for decreasing channel aging effect and increasing the EE. The first method uses channel prediction in pilot transmission phase. The second method is the formation of EE optimization problem by considering constraints on effective parameters on EE. The third method is a combination of the two previous methods, in this way, the channel prediction method is used in pilot transmission phase and the optimization problem is formed and solved to obtain optimal values of the effective parameters on EE. The simulation results show that deploying each of the proposed methods causes increasing the EE and reducing the impact of the channel aging.
