Table 2.

Selection criteria.

Selection Criteria	Task Performed
Criterion 1: Emphases on the Title	In this phase, the elimination criteria were based reading the titles and this reduced the results to 86
Criterion 1: Emphases on the Abstract	In this phase the elimination criteria used is based on the abstract in the material. This reduced the results 56
Criterion 2: Emphases on the Paper	This papers that focuses on the objective identified while those that are not focused in this area are eliminated. This reduced the results to 36
Criterion 3: Emphases on publication from related organizations	Paper that are not included in the SCOPUS database but which emphases on measurement metric especially those written by ITU are other relevant standard organization are included as they can't be found in any major databases Majorly the papers added based on the knowledge of the authors. This increased the results to 44