## 5 Numerical Results
### Integration of EPON and WLAN  
Advanced Aggregation Techniques  
Fig. 11 shows the considered FiWi network interface consisting of a tree-based EPON and next-generation WLAN-based single-channel WMN. In this figure, the optical-wireless interface consists of the following three components: \((i)\) ONU--this component contains a MAC enhanced legacy ONU which is backward compatible to legacy TDM EPON ONUs and performs aggregation and de-aggregation operations for incoming and outgoing EPON traffic, \((ii)\) MPP--this unit includes the wireless equipment of a next-generation WLAN-based WMN, and \((iii)\) CPU--this component synchronizes the two aforementioned units and controls both optical and wireless network segments by monitoring their operation. We note that the WMN provides multihop communications to forward traffic en route to and from MPPs by using intermediate MPs. In our simulations, we consider uniform unicast traffic where a given node (_i.e._, OLT, ONU-MPP, or STA) sends a generated packet to any other node with equal probability \(1/(N-1)\) and \(N\) denotes the number of nodes. We assume that 2 ONU-MPPs are connected to the OLT, whereby the distance between ONUs and OLT is set to 20 km. The optical line rate is set to 1 Gb/s. We evaluate the proposed FiWi network performance in terms of throughput, delay, overhead, and packet loss, whereby throughput denotes the number of successfully transmitted packets and delay denotes the time interval between packet arrival at the source node and packet reception at the destination node in steady state. First, we consider Poisson data traffic with different packet sizes. The size of a generated data packet is equal to 40, 552, and 1500 bytes according to a distribution of 50%, 30%, and 20%, respectively. The generated data packets are transmitted with an additional 20-byte TCP header and 20-byte IP header. In addition, we consider triple-play traffic (_i.e._, voice, video, and data). For the generation of voice traffic, we use the voice codec standard ITU-T G.711 where a packet of 160 bytes is generated every 20 ms without compression, translating into a CBR source rate of 64 kb/s. The fixed-size CBR voice packets contain 12,  
Figure 11: FiWi network interface: integrated EPON and next-generation WLAN-based WMN. 8, and 20 bytes of RTP, UDP, and IP headers, respectively. Further, we assume that there is no silence suppression. For the generation of video traffic, we deploy MPEG-4 to encode 600-byte packets at a data rate of 768 Kb/s which generates UDP CBR traffic, including 8 bytes and 20 bytes of UDP and IP headers, respectively. In our simulations, the two voice and video codecs are used simultaneously, each encoding 50% of the generated traffic. Moreover, we assume Poisson traffic with different packet sizes as background data traffic which uses 20% of the network capacity. In our simulations, we use the limited-service interleaved polling with adaptive cycle time (IPACT) with the maximum grant size of \(G_{max}\)=15 kbytes as EPON DBA algorithm [56]. In the limited-service granting approach, the transmission grant size per ONU is set to the reported queue size up to a maximum grant size of this ONU. Three STAs are located at a range of 2 km of the associated MAPs, while the distance between a connected pair of MP and MPP is set to 2 km. In our simulations, the bit error rate (BER) of the wireless channel is set to \(10^{-5}\). Fig. 12 shows the beneficial impact of our proposed advanced aggregation techniques on the network performance for a 54 Mb/s WMN under voice, video, and data traffic. We observe that the proposed aggregation techniques improve both network throughput and delay. The throughput increases for increasing load, whereby the voice traffic achieves higher throughput than others using the proposed aggregation techniques. Fig. 13 shows the impact of our proposed aggregation techniques on the performance of the FiWi network for various WMN data rates 54 Mb/s, 100 Mb/s, 300 Mb/s, and 600 Mb/s under triple-play traffic.