# Toward QoS Monitoring in IoT Edge Devices Driven Healthcare--A Systematic Literature Review
## 3 The Systematic Review Process
### Search Strategy  
Various reputed research data sources were explored to extract the required results from the well-known digital libraries as enumerated below in Table 2. The research community highly regards IEEE Xplore and ScienceDirect for their relevant material, open access, and variety of publication types. Their availability of search capabilities and citation analysis data in numerous formats is the most significant aspect. Additionally, Google Scholar offers a vast number of search results, some of which even point to high-quality research papers that may not be accessible through other search engines. Each database offers a variety of logical tools that can be used to enhance search terms in an easy and efficient way.  
The research questions were broken down into individual keywords, and an array of alternative spellings and synonyms was built. Furthermore, the query string was composed using Boolean logic operators of AND and OR. Figure 5 below shows the simple and sophisticated (using logical AND/OR operators) query strings, which were used to search the previously mentioned data sources [11].  
The identified keywords were used to search online data sources and databases. It was discovered that longer keyword strings were not helping in determining individual keywords' contributions. Keyword strings were kept under 5 to 6 words unless unavoidable. The below guidelines were followed:  
* Advanced settings of databases were used to restrict search results or relevant papers and considered metadata comprised of TAK (title, abstract, and keywords).
* For every search pass, only the first 100 results were reviewed.
* Mostly recent publications (3 to 5 years old) were considered unless unavoidable.
* If highly important papers were not available because of any restrictions (e.g., paid or members only) then they were searched alternatively, such as on the author's page.
* Reference management application was used to record and manage the references of the papers--web links, books, etc.  
The searched research was selected as per the relevance of formulated research questions. This selection criteria were carried out iteratively. In the first iteration, only titles, abstracts, and keywords of the research were considered, and if required, the introduction and conclusion were also reviewed to determine the paper's relevance with the research  
\begin{table}
\begin{tabular}{l l l} \hline \hline
**S.No.** & **Name** & **Web Link** \\ \hline
1 & IEEE Xplore Digital Library & www.ieeexplore.ieee.org (accessed on 10 January 2023) \\
2 & ScienceDirect & www.sciencedirect.com (accessed on 17 January 2023) \\
3 & Google Scholar & www.scholar.google.com (accessed on 30 January 2023) \\ \hline \hline \end{tabular}
\end{table}
Table 2: List of Data Sources.  
question [12]. Subsequently, the research methodology of the selected papers was reviewed to identify QoS parameters, network layers, technologies, and data sets employed in smart health applications. Moreover, other than relevance, the following inclusion criteria were considered:  
* Research papers published in the last 3 to 5 years;
* Research papers in the English language only;
* Research papers published by academics only.  
Likewise, the following exclusion standards were taken into account:  
* Research published in dissertations, unpublished work, and editorial notes;
* Duplicates and research papers not available in the full text.  
According to the specified search and quality assessment criteria, data were retrieved from the pertinent research papers as shown in Figure 6[13]. Data analysis on QoS enhancement in smart health care applications. Furthermore, pertinent information relating to the research questions was recorded in our SLR.  
Figure 5: The search hierarchy shows the straightforward and mixed search terms that were used to look for the aforementioned data sources (using AND and OR).