# KQI Performance Evaluation of 3 GPP LBT Priorities for Indoor Unlicensed Coexistence Scenarios
## 6 Conclusions  
This article presents an end-to-end multi-service performance evaluation by simulating an indoor dense coexistence environment. In such scenario, two non-cooperative deployments in the unlicensed sub-6-GHz bands coexist. The first is an operator using 3 GPP Listen Before Talk access technology and the other is an operator with the WiFi 802.11 ac. In this context, the performance and fairness of each \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **3 GPP LBT p(1)** & **3 GPP LBT p(2)** & **3 GPP LBT p(3)** & **3 GPP LBT p(4)** & & \\ \cline{2-9}  & **D-max** & _p-Value_ & **D-max** & _p-Value_ & **D-max** & _p-Value_ & **D-max** & _p-Value_ & **Da = 0.05** \\ \hline
**Throughput** & 0.32860 & \(5.73\times 10^{-98}\) & 0.31493 & \(1.03\times 10^{-98}\) & 0.292340 & \(1.25\times 10^{-78}\) & 0.294113 & \(1.44\times 10^{-77}\) & 0.02371 \\ \hline
**Latency** & 0.28093 & \(1.01\times 10^{-71}\) & 0.25849 & \(8.68\times 10^{-61}\) & 0.24505 & \(1.13\times 10^{-54}\) & 0.24682 & \(1.85\times 10^{-55}\) & 0.02371 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Fairness assessment based on K-S test \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **3 GPP LBT** & **WiFi** \\ \hline Standard version & Rel.13 & 802.11 ac \\ \hline MCS selection Scheme & Adaptive based on SINR (AMC) with BER\(=1\times 10^{-5}\) \\ \hline Frequency & 5180 MHz & 5180 MHz \\ \hline Bandwidth & 20 MHz & 20 MHz \\ \hline Max power TX (dBm) & 18 dBm & 18 dBm \\ \hline Antenna gain (dBi) & \multicolumn{2}{c}{5 dBi base stations} \\ \hline Antenna type & Omnidirectional & Omnidirectional \\ \hline Thresholds CCA (dBm) & ED (\(-72\) dBm) & (PD, ED) (\(-82\), \(-72\)) dBm \\ \hline Antenna configuration & MIMO \(2\times 2\) & MIMO \(2\times 2\) \\ \hline Minimum duration of sensing period & 34 us & 43 us \\ \hline Channel model & ITU InH IEEE \\ \hline User distribution & Uniform random distribution \\ \hline Noise figure in UE & \multicolumn{2}{c}{9 dB (\(-104\) dBm noise floor)} \\ \hline DRS, Packet Scheduler & 80 ms, Proportional Fair & N/A \\ \hline CW Updating Rule & “any NACK” (to detect collisions) & N/A \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulation parameters. priority established by 3 GPP for LBT CAT4 proposed for LAA, eLAA and FeLAA and applicable for 5G NR-U were evaluated for a real-time service (FTP) and a non-realtime (Video Streaming) service. According to the results obtained, and in contrast to the predicted from abstract models, Priorities 3 and 4 show very similar behavior, offering higher levels of user satisfaction measured in KQI for both real-time and non-real-time service compared to Priorities 1 and 2 and greater fairness towards WiFi. Therefore, it is proved that, in indoor dense coexistence scenarios, the 3 GPP LBT parameter with the most significant impact is the Maximum Channel Occupation Time (MCOT). As a rule, configurations with longer MCOT provide higher user throughput and lower latencies. Nevertheless, it is essential to note that fairness is always compromised for all priorities, indicating that WiFi is still degraded. Based on the evaluation made, it is necessary to find ways to optimize user's performance and fairness in dense scenarios for future 5G NR-U developments in the unlicensed band. In addition, it can be inferred that the use of lower priority values (3 and 4) is recommended to get the best user experience, even if their waiting times are longer. A method to manage the synchronization between 3 GPP Listen Before Talk base stations in order to avoid self-collisions when shorter duration signals are sent (1-2 ms) is therefore needed. In this way, an algorithm to dynamically assign priority classes and further elaboration on network metrics (e.g., cell throughput, resource blocks utilization, network power consumption, etc.) are envisioned as future work.