# A Review on Methods and Systems for Remote Collaboration
## 2 Methodology  
Our research methodology was organized in three phases: planning the review, conducting the review, and documenting the review. The first step was to define the scope of the review by identifying the answers to the following research questions:  
* \"What kinds of devices are used in remote collaboration?\"
* \"What are the industrial domains making use of remote collaboration infrastructure?\"
* \"What are the technologies used in displaying the information?\"
* \"What are the types of communication cues used in remote collaboration?\"
* \"What can be improved to offer a better user experience?\"  
The second step was to conduct the review by selecting the existing studies in the field, extracting the required content, and synthesizing the data for the last stage of elaborating the review. A total of 230 articles were selected by querying two databases, IEEE [23] and ACM [24], using the following keywords: \"remote collaboration\", \"remote collaboration system\", \"remote video collaboration\", \"remote assistance\", and \"remote guidance\". We chose these two databases because the number of articles that resulted from the queries was significant, and we considered that the content was relevant for our research. Figure 2 shows the dynamics of the \"remote collaboration\" subject in academia and industry. Figure 2 depicts the distribution graph of the relevant articles sorted by database and year. Starting in 2010, a steadily increasing trend can be observed, almost tripling from 11 works (3 in IEEE and 8 in ACM) in 2010 to 31 works (6 in IEEE and 25 in ACM) in 2020. For the keywords \"remote collaboration\" and \"remote intervention\", Google Trends records data starting in 2004 [25]. We observed some overlap during 2004, when the interest was quite high, until early 2005. This interest can be explained by the first preoccupations in remote collaboration using augmented reality. As with each new technology that appears, the interest was high in the first year; afterwards, it decreased but had occasional spikes between 2005 and 2014. Interestingly, in March 2020, a sudden interest could be observed, which coincided with the beginning of the COVID-19 pandemic. From the total of 230 articles found in the two indexed databases, we selected the most relevant ones, excluding the papers focusing on videoconferencing, thus retaining 118 papers pertinent to the subject of remote support. After extracting the most valuable information from the selected articles, we identified three main directions for this review. Accordingly, the content of this survey is arranged on three axes, which correspond to the topics of technologies in the remote assistance sector. The first motif is represented by the electronic devices that serve the remote assistance task. Secondly, we deepened the display technologies embodied in the devices employed, and, finally, we focused on the communication cues as means used by the expert for guiding the remote user to identify objects and follow instructions. We depict in Figure 3 the main topics of this study, which will be addressed in the following sections: existing electronic devices, display technologies, and communication cues. For each of the three aforementioned topics, the information was systematized in a table that identifies the works in a specific scientific field and the different methods/equipment used. Thus, future researchers will be able to more quickly locate the scientific works and the methods/equipment used by different authors for a certain field/task/problem. Readers will be able to focus only on the solutions that apply to their activity, and they will be able to identify the advantages or disadvantages of the various existing/applied solutions from the comparison done in this review. Figure 3: Plan of the review distributed across the three focus areas—electronic devices, display technologies, and communication cues—with the generalization of each topic into sub-topics.