## 4 QoS Provisioning Techniques for Future FiWi Networks
### FiWi QoS Provisioning Techniques and Mechanisms  
Traffic Class Mapping, Scheduling, and Resource Management  
In [50], centralized and distributed scheduling approaches were proposed for the integration of EPON and WiMAX. The simulation results demonstrate the improvement of network throughput and end-to-end delay for different QoS demands. The integrated QoS-aware DBA scheme proposed in [51] supports bandwidth fairness at the ONU-BS interface, while the WiMAX SSs perform class-of-service bandwidth assignment. The reported results show the improvement of network throughput, delay, and bandwidth utilization. Figure 6: SuperMAN architecture: integrating next-generation WiFi technologies with WDM EPON and next-generation WiMAX technologies with RPR. Fig. 7 depicts the optical-wireless interface between an RPR metro edge ring and a WiMAX access network, where the so-called integrated rate controller (IRC) plays a key role in integrating the two networks [52]. It comprises a BS controller, a traffic class mapping unit, a central processing unit (CPU), and a traffic shaper. The IRC is used to seamlessly integrate both networks and jointly optimize the RPR scheduler and WiMAX downlink (DL) and uplink (UL) schedulers. The BS controller is responsible for handling incoming and outgoing WiMAX traffic, besides providing hand-over for SSs between different interface nodes. The traffic class mapping unit is able to translate the different WiMAX and RPR traffic classes bidirectionally. The traffic shaper checks the control rates of RPR traffic and performs traffic shaping according to RPR's fairness policies. The CPU synchronizes the aforementioned units and controls the RPR and WiMAX schedulers. More specifically, the CPU estimates the load of incoming traffic from different domains and synchronizes the schedulers based on traffic monitoring. As mentioned  
Figure 8: Hierarchical WiMAX scheduling algorithm of an RPR/WiMAX interface node. Figure 7: Optical-wireless interface between RPR and WiMAX networks. in Section 2, RPR specifies traffic classes A, B, and C, while WiMAX specifies UGS, ErtPS, rtPS, nrtPS, and BE scheduling services. According to the aforementioned properties of RPR traffic classes and WiMAX scheduling services, bidirectional traffic classes are mapped as shown in Table 1.  
Fig. 8 shows the novel hierarchical scheduling algorithm proposed to provide end-to-end QoS in SuperMAN [52]. The proposed hierarchical scheduling algorithm deploys the following different queuing methods:  
* **FIFO:** Typically, UGS SFs consist of fixed-size packets at a constant data rate. FIFO queuing is used for UGS SFs due to its ability to provide in-order packet queuing for high-priority packets. * **Adaptive DRR:** To schedule ertPS, rtPS, and nrtPS SFs, an adaptive deficit round robin (DRR) scheduler is used to satisfy both delay and fairness performance of real-time traffic. The adaptive scheduler operates according to the traffic status, _i.e._, non-burst mode or burst mode. * **RR:** Due to the delay insensitivity of BE SFs, a simple round robin (RR) scheduler is applied for scheduling them. * **DFPQ:** This scheduling scheme is deployed in order to improve the fairness between the outputs of the adaptive DRR and RR schedulers. Deficit fair priority queuing (DFPQ) arranges the SF queues according to their priority classes. It then calculates the quantum of each non-empty queue based on the required bandwidth in a scheduling cycle. The higher priority packets are scheduled