FAST: A Fuzzy-based Adaptive Scheduling Technique for IEEE 802.16 Networks Sin-seok Seo ∗ , Joon-Myung Kang ∗ , Nazim Agoulmine †‡ , John Strassner † , and James Won-Ki Hong † ∗ Department of Computer Science and Engineering Pohang University of Science and Technology (POSTECH), Pohang, Korea Email: {sesise, eliot}@postech.ac.kr † Division of IT Convergence Engineering Pohang University of Science and Technology (POSTECH), Pohang, Korea Email: {nazim, johns, jwkhong}@postech.ac.kr ‡ LRSM Team - IBISC Lab University of Evry Val d’Essonne, France Email: nazim.agoulmine@iup.univ-evry.fr Abstract—Since the IEEE 802.16 first standard was proposed in 2004 to provide broadband wireless service, the standard has not only been widely studied, but also broadly commercialized. The current IEEE 802.16-2009 standard document specifies five Quality of Service classes. As is typical with most standards, IEEE 802.16 does not require the use of a specific scheduler. In this paper, we first evaluate the performance of four popular schedulers. By analyzing the results, we highlight that no single scheduler type performs the best in all traffic situations; however, we shown that there exist the most favorable scheduler type in each situation. Based on this rationale, our idea is to propose an adaptive scheduling schema where the scheduler is dynamically chosen based on the current traffic context, such as the number of flows of each Quality of Service class. We investigate this approach and evaluate its performance against existing static schemas. The results show that our approach presents some interesting performances in terms of throughput, delay, and packet loss ratio regarding state of art approaches. Index Terms—Packet Scheduling, IEEE 802.16, WiMAX, Net- work Management, Fuzzy Logic, Quality of Service I. I NTRODUCTION The demand for high data rate and large coverage in wireless networks is increasing sharply with various mobile services including video call, mobile internet, and games. To cope with this trend, the IEEE 802.16 standard [1] for broadband wireless access was proposed in 2004 superseded by several documents including the latest approved document IEEE 802.16-2009 (Air Interface for Fixed and Mobile Broadband Wireless Access System) that is a rollup of 802.16-2004, 802.16- 2004/Cor 1, 802.16e, 802.16f, 802.16g and P802.16i. This specification itself is being enhanced into IEEE 802.16m [2]. The WiMAX Forum is an industry-led organization in the area to certify and promote the compatibility and interoperability of broadband wireless products based upon the harmonized IEEE 802.16 standard. An IEEE 802.16 base station (BS) can This work was partly supported by the IT R&D program of MKE/KEIT [KI003594 , Novel Study on Highly Manageable Network and Service Ar- chitecture for New Generation] and WCU (World Class University) program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (Project No. R31-2008-000-10100-0). provide wireless access service to a fixed subscriber station (SS) within a range of 50 km and to a moving SS within a range of 3 to 15 km. The maximum data rate is up to 70 Mbps. The IEEE 802.16-2009 defines five different Quality of Service (QoS) classes, which are Unsolicited Grant Service (UGS), Extended Real Time Polling Service (ertPS), Real Time Polling Service (rtPS), Non Real Time Polling Service (nrtPS), and Best Effort Service (BE). These classes help provide different services to applications having different QoS requirements. The UGS class is designed to support constant bit rate (CBR) real-time traffic. For that, a BS regularly allocates a fixed amount of bandwidth to this traffic class. The ertPS class is intended to support Voice over IP (VoIP) traffic, which has repeated speech periods and silent periods. A BS allocates a fixed amount of bandwidth for a speech period, but no bandwidth for a silent period, unlike the UGS. The rtPS class is designed to support variable bit rate (VBR) real-time traffic, such as video streaming. A BS regularly polls each SS to determine the amount of bandwidth that needs to be allocated, because the required bandwidth varies for this kind of traffic. The nrtPS class is for non-real-time VBR traffic, and it only guarantees minimum throughput for an application. File downloading traffic is a good example of an application of this QoS class. The BE class allocates resources to SSs if and only if there are left-over resources after allocating the resources to other QoS classes of higher priority. This QoS class guarantees neither delay nor throughput. A scheduler works as a resource allocator to share limited resources among SSs that are served by a BS. IEEE 802.16 does not constrain the use of any specific scheduler; rather, the manufacturers of IEEE 802.16 devices can choose to use existing scheduler(s) or develop new one. Accordingly, the design of an efficient scheduler can be indeed a differentiation factor among manufacturer’s devices. Several schedulers have been suggested including Deficit Round Robin (DRR) [3], Pro- portional Fair (PF) [4], and Earliest Deadline First (EDF) [5]. Also, several papers that evaluate the performance of various schedulers have been published [6]–[9]. Designing a scheduler 201 978-1-4244-9220-6/11/$26.00 ©2011 IEEE 12th IFIP/IEEE International Symposium on Integrated Network Management 2011