# A Critical Examination of the Beam-Squinting Effect in Broadband Mobile Communication: Review Paper
## 4 Studies Related to the Beam Squint Exploitation  
Beam squint is not always a bad thing; the idea of the main beam changing direction with frequency was appealing for many researchers, and some studies even used it to enhance system performance. For instance, in [65], the authors formed many beams using the beam-squinting property of planar arrays using wideband perfect phase shifters instead of an existing hybrid structure. The following steps can be used to describe the work: initially, the authors determined the beam characteristics of the wideband array. Second, they created a coplanar array using the concept of the fractal that can operate across three mmwave frequency bands. The array's phase shifter was then swapped with one based on cells, as shown in Figure 15, which illustrates the steps for the suggested Sierpinski carpet antenna array with three antenna tiers, and in Figure 16, which illustrates the extensions and variations of the three-tier Sierpinski carpet array. Finally, they created the squinting multi-beam algorithm that facilitates multi-user communications on the basis of the beam-squinting property of the wideband array with optimal phase shifters. Under ideal circumstances, the study demonstrated an improvement in system performance (mutual coupling and isotropic elements were assumed). In [66], a joint optimization design based on non-orthogonal multiple access-based satellite-terrestrial integrated network at mmwave was developed for cellular network technology. They developed, in their work, a user pairing scheme, therefore; non-orthogonal multiple access technique was exploited through grouping more than two users in the same cluster. In [67], the authors explained how beam squint can be utilized for user localization. The author's idea was to control the beam squint using time delays and using it for localization. They created a method to regulate the trajectory of these beam squint points by deriving a trajectory equation for near-field beam squint points, as shown in Figure 17. In order for users in various positions to obtain the most power at various subcarriers, beamforming from various subcarriers would purposefully point to various angles and distances. Therefore, using the beam squint effect, one can easily determine the positions of the various users. The efficiency of beam squint in user localization can be shown from the study's findings. In addition, the same authors in [67] applied an advanced technique, called reconfigurable intelligent surface (RIS) [68], which suppressed the beam-squinting effect in broadband mobile communication. We believe that, in the future, there will be a considerable number of studies that, rather of focusing on eliminating beam squint, would instead focus on using it in a certain way in order to accomplish a certain goal. As a direct consequence of this, mmwave communication systems will become simpler and less expensive. Table 2 is a synopsis of the studies that were conducted on beam squint by a number of different people, and it lists the conclusions from that research. We have accomplished all that is within our ability to answer the most pertinent results and remarks, in addition to the several types of methods that were used in these studies. It was found that the tradeoff between the array size and  
Figure 16: Extensions and variations of the three-tier Sierpinski carpet array [65]. Figure 15: A Sierpinski carpet antenna array with three antenna tiers [65]. the reduction of the impacts of beam squint was significantly similar and directly related to the cost and design complexities of the hardware that was employed for these systems. This was found to be the case after it was discovered that these two factors were directly related to each other.