الفهرس 
Essential Techniques in Massive MIMOOnly 14 pages are availabe for public view
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Abstract
The rapid development of the 5G mobile communication systems requires serving more users with improved performance, and the Massive Multi Input Multi Output (Massive MIMO) aims to achieve these requirements.
Massive MIMO is a crucial technology in the current wireless communication systems. The beamforming is the core technique in massive MIMO systems. This thesis studies the transmit beamforming in the massive MIMO and deduces the orthogonal locations where the users act orthogonal to each other. Based on these orthogonal locations, the thesis tries to enhance the massive MIMO system’s performance by proposing three user selection methods and an orthogonal beamforming technique.
This thesis proposes user selection techniques to reduce the interference effect between the users and enhance the beamforming performance in terms of the system’s Spectral Efficiency (SE). It presents three user selection methods: “Mean Step User selection (MSUS) method, Second Null User selection (SNUS) method, and Interference Threshold User selection (ITUS) method.” The proposed MSUS and SNUS methods depend on the orthogonal locations that are deduced through the system analysis. The proposed ITUS method relies on a certain threshold interference level that can be chosen based on the system requirements to verify an acceptable system performance. The three proposed selection methods improve the performance of the massive MIMO system compared with the ordinary system without a selection method. The proposed user selection methods are also compared with other selection methods, such as Random User selection (RUS), Semi-orthogonal User selection (SUS), and Inter-Channel Interference Based selection (ICIBS) methods. The proposed MSUS, SNUS, and ITUS methods improve the sum spectral efficiency by 75.39%, 92.13%, and 153.71%, respectively, compared to the ordinary case without selection, with 100 antennas at the Base Station (BS) serving 35 users.
The thesis also proposes a beamforming technique that aims to enhance the massive MIMO system performance and increase the number of served users. The proposed beamforming technique is named “Orthogonal Beamforming Technique.” It is based on predefined orthogonal beams, which depend on the deduced orthogonal locations. The proposed technique contains several orthogonal beams, which rely on the massive number of antennas at the BS. These orthogonal beams in the proposed technique can serve more users than the adaptive beamforming technique. The adaptive beamforming can serve approximately M/4 or M/5 users with improved performance. However, the proposed orthogonal technique can serve up to M/2 users, where M represents the number of used antennas at the BS. The thesis demonstrates the assignment process of the orthogonal beams to the users. Also, it proposes solutions to the issues that may arise in the case of multi-users. The performance of the proposed beamforming technique is compared with the adaptive beamforming technique. The simulations illustrate that the proposed technique can provide a SE improvement of about 40% over the adaptive ZF technique. Furthermore, it can support up to twice the number of users compared to adaptive beamforming.