# Future Is Unlicensed: Private 5G Unlicensed Network for Connecting Industries of Future
## 4 Challenges and Research Directions
### Challenge 3: Neutral Host Deployment  
The neutral host network (NHN)[52; 53] access mode is one of the new network architectures envisioned by 5G. The NHN mode is a new self-contained network, which enables access authentication with or without a SIM card to provide services for subscribers from different types of service providers, including traditional mobile network operators, as well as non-traditional participating service providers. In a smart factory where the network is mostly for the robots and UAVs, but the factory also needs to support employees and visitors' smartphones from different host providers, if we see the channel access mechanism proposed with Category 4 for NR-U, there are only four priority access labels available for NR-U devices, as shown in Table 6. All of the accessible equipment in the smart factory will connect via the access Category 4 specification for the channel access mechanism. The problem with NR-U while interconnecting these devices is that when the mobile users use high priority applications such as voice or video applications based on Category 4, the other mission-critical applications manufacturing devices such as robots or UAV devices that are assigned to do time-critical tasks will be highly interrupted. That is a smartphone using high multimedia (non-official work) data that will make channels busy for mission-critical applications. The interruption in this time-critical function can incur disasters in the smart factory. Hence, we need to modify the existing Category 4 priority access mechanism and design a new category specification that reconsiders specifications and manages resource allocation based on mission-critical applications or tasks.  
A self-organized network (SON) [54] encompasses solutions to self-configure and self-optimize a network. It was introduced in LTE to facilitate the deployment of a system and to allow for further performance optimization. Mobility robustness optimization (MRO) and mobility load balancing (MLB) are two popular SON features in LTE. Other SONs such as energy saving (ES), inter-cell interference coordination (i.e., ICIC), enhanced interference mitigation and traffic adaptation (eIMTA), and coordinated multipoint (CoMP) operation are also available in the LTE network. Considering  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
\begin{tabular}{c} **Channel access** \\ **Priority Class (P)** \\ \end{tabular} & **Mp** & **CWmin,p** & **CWmax,p** & **Tm cat,p** & **Allowed CWp Sizes** \\ \hline
1 & 2 & 3 & 7 & 2 ms & [3,7] \\ \hline
2 & 2 & 7 & 15 & 4 ms & [7,15] \\ \hline
3 & 3 & 15 & 1023 & 6 or 10 ms & [15,31,63,127,255,511,1023] \\ \hline
4 & 7 & 15 & 1023 & 6 or 10 ms & [15,31,63,127,255,511,1023] \\ \hline \hline \end{tabular}
\end{table}
Table 6: Channel access priority of LBT.  
Figure 4: Handover skipping.  
the role that SON has played in LTE in helping operators deploy and increase the robustness of the LTE networks, these similar features must be included in standalone NR-U. MulteFire White Paper Version 1.01 [34] specifies the SON element for the NR-U access point. Hence, SON features can be implemented to classify the priority access between the devices and optimize the performance of the mission-critical application. For this purpose, a network slicing approach can be adopted, where network resources are packaged and assigned in an isolated manner to a set of user devices according to their priority categories.The width of network slices is dynamically optimized based on the available load in each slice, as well as adjustments of COT, CW, UL, and DL can be implemented in each slice for intra-slice priority optimization. SON features accelerated with machine learning techniques [33] can play a significant role in processing data to enhance the performance of SONs.