# Cluster-Based Transmission Diversity Optimization in Ultra Reliable Low Latency Communication
## 5 Conclusions  
This paper proposes a Cluster-based Orthogonal Frequency Subcarrier Multiple Access (C-OFSMA) mechanism for future 5G automated intra-vehicular communication through multiple clusters. This C-OFSMA divides the region into numerous clusters according to the sensor's location. Moreover, the system also classified the whole subcarrier frequency channel set into recurring frequency subcarrier channel subsets based on the cluster division. The clusters and their subcarrier restrict the sensors to select subcarrier channels from others.  
Figure 13: Determine air interference latency in different packet size.  
The goal behind this is to reduce the collision probability among clusters. The minimum subcarrier channels are evaluated that satisfy the URLLC recommended reliability of 99.999% and latency of 0.2 ms considering the 3-, 5-, and 7-packet duplication conditions.  
Simulation results prove that the 3-packet duplication required 306 subcarrier channels, 5-packet duplication required 198 channels, and the 7-packet duplication required 180 channels to satisfy the 99.999% reliability at 5000 pkt/s arrival conditions. In addition, the total number of clusters is also calculated, which are appropriate for gaining higher reliability under minimum subcarrier channels conditions. The system offered significantly greater reliability in fixed 90 channels condition, having 3- and 4-clusters. Additionally, the system reliability under the fixed channel and fixed cluster conditions are also demonstrated through simulation analysis. The proposed mechanism outperforms the URLLC standard for intra-vehicular communication by considering critical aspects.  
In a wireless sensor-based MAC protocol, energy consumption is a significant factor. Moreover, with the rapid growth of Electric Vehicles (EV), energy efficiency will draw more attention. Therefore, as possible future work, the proposed system will evaluate the energy performance transmitting, receiving, and regarding CPU for the sensor nodes, and might be applied for EV application. Finally, the proposed mechanism can be verified in other time-critical applications other than advanced vehicular communication.  
Conceptualization, M.A.H. and M.A.H.S.; methodology, M.A.H.S. and B.; software, M.A.H.S. and B.; validation, M.A.H., B. and M.A.H.S.; formal analysis, B. and M.A.H.S.; investigation, M.A.H. and A.K.; resources, M.A.H., M.M.R. and A.K.; data curation, M.A.H.S. and B.; writing--original draft preparation, M.A.H.S., A.K. and B.; writing--review and editing, M.A.H.S., M.A.H., A.K. and B.; visualization, M.A.H.S. and B.; supervision, M.A.H.; project administration, M.A.H. and M.M.R. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} C-OFSMA & Cluster-based Orthogonal Frequency Subcarrier-based Multiple Access \\ OFSMA & Orthogonal Frequency Subcarrier-based Multiple Access \\ URLLC & Ultra-Reliable Low-Latency Communication \\ WSN & Wireless Sensor Network \\
3 GPP & 3 rd Generation Partnership Project \\ eMBB & evolved Mobile Broadband \\ mMTC & massive Machine Type Communication \\ URC & Ultra-Reliable Communication \\ TTI & Transmission Time Interval \\ CAN & Controller Area Network \\ LIN & Local Interconnect Network \\ CDMA & Code-Division Multiple Access \\ OFDM & Orthogonal Frequency-Division Multiplexing \\ QoS & Quality of Service \\ HAS & Hybrid Access Scheme \\ LDPC & Low-Density Parity-Check \\ MIMO & Multiple-input Multiple-output \\ DCA & Dedicate Access Channel \\ \end{tabular}