# A Review on Millimeter-Wave Hybrid Beamforming for Wireless Intelligent Transport Systems
## 2 Literature Review  
Hybrid beamforming represents a hybridization of analog and digital beamforming techniques, offering a balance between the cost-effective analog approaches and the high-performance but complex digital solutions. In the realm of millimeter-wave wireless communications, where massive MIMO systems with large antenna arrays are prevalent, hybrid beamforming plays a pivotal role in optimizing beamforming efficiency while mitigating the inherent challenges of high-frequency propagation. Various algorithmic strategies and techniques have been proposed in the literature to address the complexities and limitations of hybrid beamforming in millimeter-wave systems [12]. Performance metrics in hybrid beamforming evaluation encompass a wide array of parameters, including spectral efficiency, signal-to-noise ratio, energy consumption, interference mitigation, system capacity, and overall communication quality. These metrics serve as benchmarks to assess the effectiveness and efficiency of different hybrid beamforming algorithms. Characterizing the characteristics of hybrid beamforming techniques involves understanding the interplay between analog and digital processing elements, the beamforming structure, the number of RF chains, the selection of beamforming vectors, and the optimization criteria utilized in the design process. Limitations of hybrid beamforming include hardware complexity, cost considerations, calibration challenges, and the trade-offs between analog and digital signal processing components [13]. Performance evaluations of hybrid beamforming algorithms provide insights into their practical applicability and effectiveness in real-world millimeter-wave communication  
Figure 3: Organization of the systematic review. scenarios. Evaluations often involve simulations, experimental validations, and comparative analyses against benchmark algorithms or conventional beamforming methods. By quantitatively assessing key performance indicators such as achievable data rates, system throughput, error rates, and computational complexity, researchers can gain valuable insights into the strengths and weaknesses of different hybrid beamforming approaches. Furthermore, performance evaluations help in benchmarking the proposed algorithms against state-of-the-art techniques, showcasing their advancements, optimizations, and potential for practical implementation in millimeter-wave communication systems [14]. The systematic review on millimeter-wave hybrid beamforming for wireless communications aims to provide a comprehensive overview of the algorithmic techniques, performance metrics, characteristics, limitations, and performance evaluations associated with hybrid beamforming approaches. By synthesizing and analyzing the findings from a diverse range of research studies, this review seeks to contribute to the understanding of the current landscape of hybrid beamforming in millimeter-wave systems, identifying emerging trends, challenges, and opportunities for future research and development in this critical area of wireless communication technology. Table 1 provides a literature review of the algorithms/techniques used in hybrid beamforming along with performance metrics, characteristics, limitations, as well as performance evaluations. \begin{table}
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**S. No.