Dynamic spectrum access (DSA) is one way to utilize and efficiently manage the frequency spectrum for wireless communications. One of DSA's implementation at the physical and medium access and controls layers through cognitive radio (CR). CR and other DSA methods at those layers offer better solutions for reaching and interconnecting users or things, especially those in the rural areas, including unconnected internet-of-things (IoT) devices. This work aims to survey current technologies and standards for DSA. In particular, the comparisons are those of unutilized bands that were allocated for television broadcasting, which is known as television white space (TVWS). The paper provides an overview of TVWS, its elements, different architecture depending on the chosen application, and to show potential gaps for future techniques and technologies for TVWS systems and research.

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Wireless multipath propagation causes different paths taken by the signal due to interacting objects present in the environment producing multipath components (MPCs). Cluster-based channel models characterize the wireless channel, and different approaches are utilized to cluster the MPCs. Data mining requires different techniques such as visualization to extract important information and find patterns and clusters in the data. A Graphical User Interface (GUI) is developed in this paper to aid the visualization and the manual clustering of MPCs using t-distributed Stochastic Neighborhood Embedding (t-SNE) and Uniform Manifold Approximation and Projection (UMAP). The clustering results of Simultaneous Clustering and Model Selection (SCAMS) are used in this paper. The datasets are embedded into low-dimensional projection and are manually re-clustered. The manual clustering was performed visually and interactively, which achieves a higher Jaccard membership index with a low value of 0.3368, a median of 0.4697, and a high value of 0.8884 for all the datasets.

As the world advances into 5G networks, significant scientific research accomplishments are being conducted for a communication system that could further enhance the current limit of data transmission capacity. Currently, the communication systems with the highest data rate are optical fiber systems. Due to the recent advancement of coherent optical fiber communications by exploiting time, wavelength, phase, amplitude, polarization, and space, optical engineering can break the petabit barrier data rate. Thus, coherent optical fiber communications is a hot topic due to its very high data rate that could be applied or a requirement in 5G and big data analytics. This paper focuses on a comparative survey of the current applied fundamental techniques in fiber communication channels. These fundamental techniques that could be further studied and exploited to increase the bandwidth performance, decrease the error rate and energy consumption are coding, multiplexing, and equalization. At the end of this paper, a comparative result is discussed to explain the difference among the current techniques in the literature for the optical engineering community to improve collective coding, multiplexing, and equalization in coherent fiber systems.

While there is a scarcity in the spectrum available for allocation, their utilization is low. Except for the overcrowded cellular network bands, there is a very low occupancy in a significant amount of the spectrum all the time [7,8]. For example, according to [4], the

A television white space (TVWS) is an unused spectrum band in the TV broadcasting band. This unused band of frequency in TV channels can be used for different applications that benefit the people. TVWS, with its accompanying communications technologies, has promising uses and advantages in wireless systems. TVWS can replace or co-exist with other communications systems. However, gauging the technological transitions for the adoption of the TVWS system is sometimes overlooked. This paper developed a set of questions that could gauge and evaluate the level of adoption and implementation of a country's TVWS communications based on Davis's proposed technological transition architecture framework. The technological assessment developed in this paper leads to a better understanding of the niche, regime, and landscape considerations in implementing TVWS systems.