# Model Mediation to Overcome Light Limitations--Toward a Secure Tactile Internet System
## 1 Introduction
The intelligent smart grid systems monitor the status of the power generators and transmission lines, and control the operation of both. Furthermore, the user consumptions and tariffs are monitored and controlled by the intelligent grid systems. Thus, such systems require ultra-reliability and low latency communication systems (e.g., the required end-to-end latency of a synchronous co-phasing of power suppliers is 1 ms) to convey the information among the network. Tactile Internet will support these systems by achieving an end-to-end latency of 1 ms with an ultra-high reliability (e.g., systems with packet loss probability of 0.001%) [25]. 8. Other applications: Tactile Internet will have many applications in various fields, which are not limited to the previous mentioned ones. Tactile Internet is expected to have applications in other vital fields such as education, culture, serious gaming, and unmanned aerial vehicles. Tactile Internet will assist developing applications that will help children as well as adults with difficulties in developing their education skills, recovery of skills after injury or having disabilities [17; 26]. Serious games are games that combine fun with other motivations and problem-solving challenges [27]. These motivations represent the primary goal of the game; other than the fun and entertainment. Serious games have applications in all vital fields such as; education, simulation, training and health. Since, the end-to-end latency of communication systems supporting these games represents an important factor of limiting the development of game-mechanics; the tactile Internetwill provide a great support for this kind of applications. Furthermore, tactile Internet will provide the communication medium for the human controlled unmanned aerial vehicle applications with the required latency, reliability, and system availability [28]. Powered by the recent advances and developments in the near future release of the fifth-generation cellular system (5G), researchers and industry groups begin to take real steps and put road maps toward tactile Internet system realization [29]. There are many requirements and constraints on designing, developing and realizing the tactile Internet systems, which include the high system availability, the very high reliability and the ultra-low latency [30]. The most important challenges among these design constraints include the following:  
* Latency: Tactile Internet is announced as an ultra-reliable low latency (uRLL) use case of the fifth-generation cellular system (5G/IMT2020) [31, 32]. Tactile Internet system requires an end-to-end latency of 1 ms, which is far from the end-to-end latency of current applications and systems. Latest systems of fourth-generation cellular system (4G) handle a round trip latency of 15 ms, while the first release of 5G is expected to enhance the latency performance and achieve an end-to-end latency of 5 ms [33]. Tactile Internet will reduce this latency to 1 ms that will include all delays involved in the communication process. Section 3 discusses the 1 ms challenge in details. * Reliability: Tactile Internet system is required to achieve ultra-high reliability so that the packet loss will be less than \(10^{-7}\)[34]. This is because higher packet loss probability, results in incorrect data at the slave side that leads to incorrect interaction with the remote side [35]. Current transmission protocols (e.g., UDP and TCP) cannot be used for the tactile Internet applications, especially for haptic based applications, because of the required reliability and latency. Thus, new protocols need to be developed. * Security: Heterogeneous communications over the tactile Internet requires different levels of security.