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Top1. Introduction
The scheduling system model plays a major role in the Voice over IP (VoIP) over Wireless LANs (WLANs). It fulfills the Quality of Service (QoS) requirements of the VoIP over WLAN through the scheduler, efficient algorithms and managing traffic flow. The VoIP over WLAN is another emerging application besides the Internet Protocol TV (IPTV) and the High Performance-Video Conferencing (HP-VC). This paper presents a new VoIP scheduling system model and algorithm in order to enhance performance of voice traffic over WLANs. The scheduling system model is an important technique to achieve efficient throughput and fairness over WLANs based on IEEE 802.11 standards (Lee, Claypool, & Kinicki, 2010; Wang & Zhuang, 2008). Scheduling techniques manage voice traffic over WLANs. It will be able to offer bandwidth link-sharing to tolerate the status of changing traffic queues and to be scalable over IP-based networks. A number of related schedulers have been proposed to support traffic flow over IP-based networks. Most of the existing schedulers support limited services and do not meet the requirements of real-time applications especially for the VoIP over WLANs.
The bottleneck of the scheduling mechanism is the downlink path and uplink path of traffic flow over WLANs. In the scheduling mechanism, the downlink path is comparatively easy due to the Access Point (AP) having complete information regarding traffic flow. As far as the uplink path is concerned, traffic flow comes from Stations (STA) which makes it difficult due to diverse techniques, procedures, parameters and traffic flow over networks (Ansel, Ni, & Turletti, 2006).
The IEEE 802.11 WLAN network is a wireless Ethernet, play an important function in the future-generation networks. WLAN is based on Link Layer (LL). LL is divided into Logical Link Control (LLC) and Medium Access Control (MAC) sub-layer categorizes with two functions, Distributed Coordination Function (DCF) and Point Coordination Function (PCF) (Mirkovic, Orfanos, Reumerman, & Denteneer, 2006; Wang & Wei, 2009). The IEEE 802.11 WLAN networks support both contention-based DCF and contention-free PCF functions. DCF uses Carrier Sensing Multiple Access/Collision Avoidance (CSMA/CA) as the access method (Cao, Li, & Leith, 2009; Dini, Font-Bach, & Mangues-Bafalluy, 2008; Li,Ni, Turletti, & Xiao, 2006; Ni, Li, Turletti, & Xiao, 2005; Garg & Kappes, 2003; Hole & Tobagi, 2004; Cai, Shen, Mark, Cai, & Xiao, 2006; Deng & Yen, 2005; Ergen, Lee, Sengupta, & Varaiya, 2004; Deng, Ke, Chen, & Huang, 2008; Wang, Liew, & Li, 2005; Tickoo & Sikdar, 2004). IEEE 802.11 standards 802.11a support 5GHz frequency band and 54Mbps data rate, 802.11b support 2.4GHz frequency and 11Mpbs data rate, 802.11g support 2.4GHz frequency band and data rate 54Mbps (Ahmed, Jiang, Ho, & Horiguchi, 2009; Forouzan, 2007; Ni, Romdhani, & Turletti, 2004; Wu, Peng, Long, Cheng, & Ma, 2002; Li, Ni, Turletti, & Xiao, 2006; Ni, Romdhani, Turletti, & Aad, 2002; Xiao & Rosdahl, 2002; Garg & Kappes, 2004; Chen, Pang, Sheu, & Tseng, 2005).