# Highest Cost First-Based QoS Mapping Scheme for Fiber Wireless Architecture
## 5 Simulation Setup and Results
The Equations (10) to (12) state the JFI relationship for allocated bandwidth and overall distribution of bandwidth:  
\[f(y)=\ \frac{\left[\sum_{i=1}^{s}\gamma_{i}\right]2}{S\times\sum_{i=1}^{s}( \gamma_{i})2},if\ \gamma_{i}\geq 0 \tag{10}\]  
\[y_{i}=\ \frac{AB_{i}}{TB_{i}}\ if\ TB_{i}>AB_{i} \tag{11}\]  
\[y_{i}=\ 1,\ otherwise \tag{12}\]  
where the \(\ \gamma_{i}\) value is expressed as the ratio of allocated bandwidth (\(AB_{i}\)) to the total bandwidth (\(TB_{i}\)) for each ONU at \(i\)th load. The term \(S\) is the number of contending streams. The performance results of JFI are shown in Figure 10 for dGIANT and HCF schemes versus the traffic load for all the traffic classes for both DCF and EDCA wireless modes. The JFI values in DCF mode are almost the same for all traffic classes due to the FIFO queuing mechanism. However, the HCF algorithm results in a slight performance improvement of 1.2%, 1.3%, and 1.5% for VI (T2), BK (T3), and BE (T4) traffic for the DCF model. However, due to the HCF algorithm, a significant performance improvement was observed in EDCA mode. The VI (T2) has the lowest CW size in EDCA with the highest priority, thus, its JFI values are higher than the other traffic classes. Figure 10b shows the fairness results for VI (T2), which shows that as the traffic load increases, the JFI values decrease. As VI (T2) is the second highest priority traffic in both standard XGPON and WLAN, therefore, at the XGPON side, the assured bandwidth is reserved for T2 TCONTs. The HCF and IACG combination, referred to here as HCF-DBA, results in higher bandwidth assignment due to efficient traffic mapping between the wireless and optical networks, and the excess bandwidth assignment by the IACG DBA process at the OLT. Figure 7:0 Mean US average delay versus traffic load using DCF and EDCA, with HCF and dGIANT in the FiWi network. A similar performance boost is also observed for the BK (T3) traffic in EDCA mode, as evident from Figure 10c. The T3 TCONTs have half assured and half non-assured bandwidth in the XGPON DBA process. As the load increases, the JFI index values decrease, but comparatively, the fairness results of HCF are observed to be better than dGIANT. The lowest priority traffic is the BE (T4), but its performance is also significantly improved due to the DCF and IACG combination. Figure 10d presents comparative results which show that dGIANT cannot assign more bandwidth to BE (T4) traffic as compared to IACG, therefore, the JFI values of HCF-DBA are much better than the dGIANT-DBA in our FiWi access network testbed. Overall, a performance improvement of up to 96.1%, 90.8%, and 55.5% for VI (T2), BK (T3), and BE (T4) traffic for the EDCF mode is observed with HCF-DBA compared to the dGIANT scheme. In order to measure the efficiency of both schemes, we also record the unallocated bandwidth ratio (UBR) at the OLT, as a percentile of unallocated bytes per cycle over total frame bytes available for the US link. Figure 11 shows the UBR for both DBA schemes in both modes. As expected, the UBR is higher for the DCF mode compared to EDCA mode due to single FIFO queuing for traffic. Similarly, as expected, the HCF-DBA performs better than the dGIANT DBA due to the efficient mapping of traffic classes. In all cases, the UBR decreases as the traffic load increases because of increasing traffic demand by the ONUs, which results in higher bandwidth assignment and, thus, lesser unutilized bandwidth. Overall, the HCF-DBA shows up to 65% and 15% lower UBR for DCF and EDCA modes compared to the dGIANT scheme in our FiWi access network testbed. Figure 7:1 Fairness index versus offer load using DCF and EDCA in the FiWi network: (**a**) Voice traffic case, (**b**) video traffic case, (**c**) background traffic case, and (**d**) best effort traffic case.