## 5 Massive MIMO
### Classification of Applications
#### 5.1.2 Base Station  
For the design of 5G mMIMO base stations, the 2D model is the utmost simple planar mMIMO arrangement is an array of \(N\times M\) configuration of the planar array. The various designs (cylindrical, planner, and circular) significantly affect the mMIMO system performance. As the beam can be adjusted only horizontally, usually the circular or planar array design shows a considerable reduction. Moreover, these designs also fail to increase channel capacity demands. Therefore, it is proposed that 3D massive arrays such as hexagons, cylinders, triangles, etc. arrangements should be adopted [159]. Many 5G base station antenna designs have been investigated in this study [160; 161; 162; 163]. For an indoor MIMO base station, an ultra-wide-band portable multi-element antenna consisting of 121 physical antennas to construct a 484-port is investigated in [164]. This antenna is effectively working on a wide frequency range from 6 to 8.5 GHZ and uses 3D radiation patterns to measure total efficiency of around 70%. It has been observed that 64 QAM can simultaneously be transmitted for a single user with 8 antennas, and 5 Gbps is feasible at 200 MHz. Moreover, a 10 Gbps throughput for multiple users in an outdoor environment is also possible [165]. Another high isolation 32 elements mMIMO antenna with a measured bandwidth of 250 MHz For next generation 5G base stations is investigated in [166]. The decoupling of 32 dB among array elements with a reduced ECC of 0.0001 is observed by this proposed MTM-based method. In [167], an mMIMO antenna system having 288-elements and 72 ports is presented for 5G base stations. A 3-layer configuration with 24-ports on every side of the antenna system. The single port gain of 9.41 dBi and 64% efficiency was measured. It has been observed that increasing the antenna elements significantly increases channel capacity in the mMIMO system. A significant variation in gain patterns also has been experimentally evident from various antenna elements in a finite array. The mutual coupling and edge effect are the main players in the beamforming which is directly dependent on the arrival angle. The key concept of mMIMO is to obtain all the functions of traditional MIMO but over a large scale. The mMIMO is analyzed as an efficient technique for B5G networks with several benefits and features, listed in Table 5 which briefly describes a comparison of various key enabling techniques with mMIMO [168]. The key problem with the deployment of mMIMO is a radio-frequency pattern that increases the difficulty of the symbol detectors can be addressed by combining analog and digital beamforming, called hybrid beamforming structure [169; 170; 171; 172]. In [173], a detection algorithm for perfect mMIMO has been proposed to increase performance and decrease complexity. This paper briefly discusses various mMIMO detection algorithms in detail. Likewise, A practical test at Lund University was conducted utilizing around 100 BS antennas along with up and around 50 field programmable gate arrays. The obtained results show that mMIMO can simultaneously work for a number of users in a static inside/outside environment using a similar frequency and time band [174]. As conventional wireless communications systems are unable to provide the SE's that 5G applications require, the mMIMO is becoming a reality now because it can simultaneously provide in the downlink and uplink direction of B5G due to uplink-downlink duality. In [132], SE is expressed as an outcome of the number of base station antennas \(M\). To achieve the highest SE, the functional subscribers are optimized for each \(M\). As per IMT-Advanced, the performance baseline SE is in the range of 2-3 bit/s/Hz/cell, subject to simulation scenario. The results shown in [175], with \(M=100\) antennas an achievement of 52 bit/s/Hz/cell which is 17\(\times\) to 26\(\times\), and with \(M=400\) antennas an unbelievable 38\(\times\) to 57\(\times\) enhancement over IMT-Advanced. Importantly, the number of active subscribers grows together with the SE.