## 4 Current Issues and Challenges of Realising the Tactile Internet
\begin{table}
\begin{tabular}{p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt}} \hline \hline
**Challenges** & **Description** & **Potential Enabler and Solution with References** \\ \hline Ultra-low Latency (I ms RTT) & & & Emerging Passive Optical Local Area (POL) technology [33]. \\ Ultra-low Latency (I ms RTT) & & To avoid noticeable motion sickness (lag). & \(\bullet\) Employing short frame transmission structure [34]. \\  & & & Needing physical layer and control (MAC) layer techniques. \\  & & & Relating to core network: SDN-based methods, NFV-based methods, Fog/Edge-based designs and Directory-based architectures [35; 36; 37; 38; 39; 40; 41; 42]. \\ Transparency with the User & Action performed in real time must be the same in the remote scenario to have desired feedback to the end user. Experience a specific level of immersion to perform desired activities. & \(\bullet\) & Faultless simulation needed when dealing with physical interaction of virtual scenario emulating the remote scenario [43]. \\ \hline Ultra-high Availability and Reliability of Information/ Connection & To ensure a consistent stream of information between server and end user. Relying on the data of the end user and its feedback. & \(\bullet\) & Making use of concurrent connections with several links [44]. \\  & & & Using multi-path communication to avoid a single point of failure. \\  & & & Relies on dynamics of the Channel State Information (CSI). \\  & & & Need for re-exploring the control layer, transport layer protocols and session layer [45; 46]. \\ Network Slicing & Trade-off between the three generic services of 5G, viz. eMBB, mMTC and URLLC. & & Non-orthogonal allocation resources among the heterogeneous services through slicing of radio access network (RAN) [47]. \\  & & Trade-off between the three generic services of 5G, viz. eMBB, mMTC and URLLC. & & Dynamic network slicing for facilitating network in demand functionalities [48; 49]. \\  & & & Integration of network-aware and control-aware for maximising Quality of Experience (QoE). \\  & & & Need for dynamic control switching methodologies for TI telepresence applications [50]. \\ Wireless Resource Customisation & Usage of application-specific wireless resources allocation techniques. & & Need for joint uplink and downlink symmetric resource allocation with constant rate [51]. \\  & & & Radio resource slicing, i.e., Flexible resource allocation techniques with network slicing [49] and adaptive flow management for traffic. \\ Easy Incorporation & Incorporation of wired and wireless system, i.e., hybrid systems. & \(\bullet\) & Incorporation of haptic communications in the 5G TI system. \\  & & & Incorporation of Haptic codeces involving the kinaesthetic and tactile data. \\  & & & To determine the trade-off between the RTT (delay) and energy efficiency in unlicensed band. \\  & & & A traffic balancing scheme and scheduling needed [52]. \\ Band & & & Collaborating licensed and unlicensed access keys in 5G unlicensed [53]. \\ \hline Safety and Security Concer & Regarding the data integrity and accountability. & \(\bullet\) & Imble the trade-off for the required security level with the increment in RTT (delay). So distinct levels of security would be opted across broad range of tactile applications [3]. \\ \hline \hline \multirow{3}{*}{Haptic Devices} & \multirow{3}{*}{Dealing with Haptic Sensor and Haptic Actuators.} & \(\bullet\) & Optimising the spatial resolution, sensitivity, scan time and placements while selecting haptic sensors. \\  & & & Designing a lightweight haptic display that gives an excellent feeling to user as similar as it would feel in the real-world context. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Open challenges with descriptions and potential enablers/solutions.