# A Review on Methods and Systems for Remote Collaboration
## 7 Conclusions  
From the remote collaboration systems presented above, several issues linked to the devices and video cameras can be specified:  
* Using fixed cameras can reduce the field of view for the remote specialist and make it difficult to determine where the local user is looking. * Head-mounted cameras (HMCs), besides being uncomfortable for the wearer, restrict the field of view for the helper, who can only see what the worker is seeing. On the other hand, HMCs allow the worker to use their hands to perform tasks. * Handheld devices limit a local user's ability to use both hands freely, but the research shows that they are a good option when working on static tasks. * Head-mounted devices proved to be suitable for dynamic tasks but need stabilization techniques for captured video because the images are shaky, and viewers become dizzy. * An independent view for the remote participant improves the viewer's confidence significantly, and verbal communication is reduced used during the collaboration. * Smartphone applications used in remote collaboration still have limited performance because of the heavy use of networks when streaming video. * No published works were found on the extent to which more experts from different geographically distant locations can offer collaborative assistance for a machine/process, etc. When comparing the visual display methods, mixed reality proved to be very useful for tasks that needed complex design instructions and decreased time and mental effort. Reconstructing 3D scenes is challenging because they often have to be dynamically updated, requiring higher processing power. Regarding communication cues, pointing was the best method to use when a user wished to be quick and precise when indicating an object. Annotation cues such as sketches proved to be useful, providing spatial information when manipulating objects. Hand gestures could express more information, such as pointing, emotion, appreciation, and shapes. Researchers found that a user finished faster a task when using hand gestures than without them. This study reviewed different prototypes, systems, and methods used in remote collaboration over the last two decades. We categorized and analyzed the systems and functions of the devices used in remote collaboration, the display view of the local environment, and the communication cues used between remote collaborators. We discussed the limitations and disadvantages of the current system components and methods to better understand why these kinds of systems are not used at a large scale in industry and to help to make future decisions when designing a remote collaboration system. Table 5 summarizes the benefits and the drawbacks of the devices used in remote collaboration. Remote assistance began to be used in surgery more than 20 years ago, and it is now beginning to be employed in other fields, such as education or industry. We have seen that the latest technologies used in remote collaboration are those that allow the remote user to have an independent view of the local user's environment and offer the capability of a 360-degree panorama view. These systems employ HMDs together with MR, AR, or VR. Smart devices such as mobile phones and tablets, even if they are more accessible than HMDs and have better capabilities (such as video streaming), are not employed at a large scale for remote assistance. It can be concluded that there are many challenges in obtaining a remote collaboration system that allows the remote users to have a controlled view and make them feel as if they are immersed within the local user's environment, together with the capability of transmitting instructions in a natural manner. Digitization, together with remote assistance and collaboration to accomplish tasks, will be the future challenges for technological development. Due to the new 5G communications technologies, researchers' efforts will certainly focus on such methods.