# A Critical Examination of the Beam-Squinting Effect in Broadband Mobile Communication: Review Paper
## 3 Studies Related to the Beam Squint Effects
In order to offer a less-than-ideal answer, on the basis of eigenvalue decomposition, the semidefinite relaxation (SDR) approach was applied. The simulation results showed that, under specific circumstances, the suggested transmission method can effectively reduce beam squint and improve wideband communication systems' throughput performance. In order to demonstrate how the number of antenna elements influences beam squint and how wideband beam squint affects the traditional narrowband models, an analysis of capacity was carried out in [52]. Combining two state-of-the-art cooperative algorithms led  
Figure 10: Point-to-point capacity analysis [49]. to the suggestion of a method for assigning subcarriers to beams. The first methodology determines the optimal beams for allocation in a multi-carrier implementation and determines how much beam squint is present in the system, whereas the second methodology maps data to the appropriate beams. The results of the investigation showed that beam squint significantly affected system capacity. The results also showed that beam squint might be utilized to better manage resources and expand system capacity, as shown in Figure 11.  
The beam squint effect on channel estimation had been analyzed in [53]. In this study the authors clarified that beam squint in an MIMO-OFDM system causes the subcarriers to see distinct angles of the same path and renders the existing channel estimation and precoding algorithms inapplicable. For frequency-division duplex (FDD) mmwave massive MIMO-OFDM systems with hybrid analog/digital precoding, the authors suggested a channel estimation approach that takes the beam squint effect into account. The angle of arrival (AoA) and time delay, which are frequency-insensitive parameters of each uplink channel path, as well as the complex channel gain, which is frequency-sensitive, were extracted using a compressive sensing-based methodology. The reciprocity of these frequency-insensitive parameters in frequency division duplex (FDD) systems allows for a significant simplification of the downlink channel estimating process, using only a small number of pilots to acquire the downlink complex gains and reconstruct the downlink channels. The results of this study showed that the proposed channel estimation scheme can perform better than the other conventional methods under general system configurations in mmwave communication. The authors of [54] developed an off-grid CSS technique to calculate the uplink channel and offered a non-negligible beam squint in the field of channel estimation with beam squint. According to the authors, the direction of arrival (DOA) and the delay parameters might be calculated from the signals received on the uplink channel's pilot subcarriers using a shift-invariant block-iterative gradient technique. The entire set of channels over all subcarriers was then rebuilt using the DOA and delay settings. The outcomes demonstrated that this offered superior outcomes in comparison with previous approaches that neglected to account for beam squint. Figure 11: Improvement of capacity for fc = 73 GHz, BW = 2.5 GHz [52]. The authors in [55] present a unique digital method for correction of beam squint by utilizing Nonlinear Frequency Modulation (NLFM) Tansec waveforms when addressing phase-based phased array antennas. An algorithm was designed that chooses Tansec waveforms with phases that rectify FM-induced phase variations in the necessary transmitted signals phases. Simulations for a typical 77 GHz automobile radar with a 3 GHz BW show that the suggested technique can reduce beam squint. The authors of [56] examined the issue of estimation of channel for mmwave MIMO systems with hybrid beamforming. A beam squint for channel estimation and an asymptotically ideal analog-beam scanning and pilot tone allocation system were developed. The suggested architecture is expanded to include the Uniform Planar Array (UPA) situation that satisfies the channel vectors' asymptotic orthogonality.