## 6 Summary of Challenges  
TI applications such as self-driving vehicles, augmented reality (AR), virtual reality (VR), Industry 4.0, immersive virtual reality (IVR) and eHealth are the hot topics of research, and a remarkable amount of research is being carried out. Still, existing network infrastructures are finding it hard to cope with the stringent requirements of the TI. Moreover, the speed of light also hampers the speed of TI communication as tactile ends can be at a maximum of 150 km from each other, otherwise there would be noticeable motion sickness, also referred to as lag. As TI applications mentioned earlier, the demand for the core competencies such as ultra-low latency, ultra-high reliability, ultra-high availability, ultra-responsive and ultra-fast reaction times shows that current cellular infrastructure cannot support these competencies. It is worrisome to fulfil all the requirements of TI applications at the early stage of 5G development. The challenges related to haptic devices such as Sensable [14] and Geomatic [15] in the market have a robotic arm attached to a stylus, which restricts the free movement of the arm. Thus, it reduces the Degrees of Freedom (DoF) that are required to realise the TI truly. Since there has not been significant development of the 5G framework, the consensus implies adapting one network and sharing the resources among various vertical applications. Challenges are also experienced with the transparency of the user. An action executed in one location must replicate in remote locations with a specific level of immersion. If the RTT becomes noticeable or measurable, the transparency of the user is affected drastically. The RTT of haptic communications should be 1 ms or below. If this RTT is not achieved, it again influences the transparency of the user. There is another challenge between the control server and user to have a reliable stream of data so that any vulnerabilities cannot mess with the original data. The reliability of the connection also relies on the end-user data and its feedback. Furthermore, there is a need for qualitative and quantitative research on network slicing, including the productive virtualisation of the network framework, applying services to the network slice, the disintegration of network function and end-to-end network MANO. Here, the concept of SDN and NFV would be helpful as a potential enabler to address the challenges of TI communication. Network slicing can be used to customise wireless resources. However, human-related or machine-related communications rely on the conventional wireless resource allocation strategies focussing on the uplink and downlink of the communication. Therefore, more research is needed for wireless resource allocation for applications, considering the global control loop required for TI applications. Thus, incorporating hybrid systems, including wired and wireless systems, could solve the challenges of examining and studying the performance of haptics over Internet protocols. Because of the freely available unlicensed band, there was a crowded situation surrounding the reliability of wireless technologies. To address this issue, research should be conducted to find the substitute free spectrum for TI applications. Though millimetre wave could solve the TI's problems, it comes with a set of limitations for the shorter range of communications. In addition, there is always a trade-off between security and RTT requirements. A few applications require high privacy of data, and others rely on low RTT. Hence, emerging technologies such as 5G, Blockchain, etc., can be adopted in the TI scenario to resolve security issues. Regarding haptic devices, there are challenges related to dielectric material used in fabricating sensors, power consumption, the placement and the sensitivity range of the sensor, scanning time, spatial resolution and much more. Moreover, there are challenges surrounding the realisation of the realistic sense of touch through haptic feedback.