With intelligent devices taking an important role in our lives, demand for high data rate and system capacity is increasing day by day. The Long Term Evolution (LTE) standard, which is the standard of today's fourth-generation (4G) systems, has been able to meet these demands to a certain extent by using Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO) technology on a network designed from the outset. However, with the extraordinary demand for applications that require more bandwidth, such as very high resolution video applications, the contradiction between capacity requirements and spectrum constraints has become more apparent. It is not possible to meet this demand with existing cellular network technology, which has a very limited bandwidth and a fairly crowded spectrum. Due to the aforementioned bandwidth bottleneck, research has been initiated to provide innovative solutions for 5G cellular communication systems to support the total mobile user network traffic expected to increase 1000 times by 2020 [1]. Millimeter wave (mmW) communication for physical layers of personal Wireless Area Networks (WPAN), Local Area Networks (LAN) and Metropolitan Area Networks (MAN) has already been standardized [2,3] and has a data rate potential of Gbits at the moment, mmW communication has also become a strong candidate for 5G cellular networks.The mmW band is the frequency range defined as 30 GHz -300 GHz (3 GHz to 30 GHz according to some studies). There are several advantages to be gained by using mmW band in 5G cellular networks. The first one of them is that the mmW band provides a wide spectrum. The other is that the communication in this band is short-range one due to the severe path loss, and thus it is possible to reuse the frequency at short distances and hence it is possible to extremely increase the capacity. Another is that very high data rates can be achieved by communicating with antenna arrays consisting of several
ABSTRACTFifth-generation (5G) cellular communication systems aim to obtain a higher data rate, decreased latency time, higher performance even at high mobility speeds, decreased system complexity, lower transmission cost, and an increased system capacity and coverage area. Many of these goals can be achieved because of the studies devoted to the physical layer of 5G cellular networks. In this respect, solutions to the problems of beamforming (steering and precoding or precoding and combining) and channel estimation that are encountered in the physical layer of 5G cellular networks are the key points to achieve the aforementioned goals. Thus, a two-stage beamforming method is proposed in this study. The proposed method is a suboptimal method that minimizes the difference between outputs obtained when fully digital and hybrid beamforming methods are used. The analytical results, which are validated through simulations, demonstrate that the proposed method is an effective solution and, hence, the preferred beamforming approach for 5G millimeter wave band-b...