ABSTRACT
Contents 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 8.2 Cognitive WLAN over Fiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
8.2.1 Cognitive Radio in WLAN over Fiber . . . . . . . . . . . . . . . . . . . . . . 223 8.2.2 CWLANoF System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
8.2.2.1 Medium Access Issue in CWLANoF . . . . . . . . . . . . . . 226 8.2.2.2 Design Concepts of CogAP . . . . . . . . . . . . . . . . . . . . . . . . 228
8.2.3 ISM-Band Spectrum Sensing and Interference Avoidance/Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 8.2.3.1 External Systems Sharing ISM Band. . . . . . . . . . . . . . . 229 8.2.3.2 WLAN Co-Channel and Adjacent-Channel
Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 8.2.3.3 Existing Spectrum Sensing and Interference
Avoidance/Mitigation Techniques . . . . . . . . . . . . . . . . . 232 8.2.3.4 Enhancements in CWLANoF . . . . . . . . . . . . . . . . . . . . . 233
8.3 QoS in Conventional WLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
8.3.1 Channel Access in 802.11e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 8.3.1.1 EDCA and Priority-Based QoS . . . . . . . . . . . . . . . . . . . . 237 8.3.1.2 HCCA and Parameterized QoS. . . . . . . . . . . . . . . . . . . . 237
8.3.2 Traffic Stream: Admission Controller and Scheduler . . . . . . . 238 8.4 QoS in Cognitive WLAN over Fiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
8.4.1 Existing FCA Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 8.4.1.1 FAP in Graph Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 8.4.1.2 FAP and Integer Programming . . . . . . . . . . . . . . . . . . . . 239 8.4.1.3 MI-FAP and Constraint Satisfaction Problem. . . . . 239 8.4.1.4 Heuristic Methods in MI-FAP. . . . . . . . . . . . . . . . . . . . . 240
8.4.2 DCA Strategies in Cognitive WLAN over Fiber . . . . . . . . . . . . 241 8.4.2.1 Adjacent Channels in 5 GHz Band . . . . . . . . . . . . . . . . 242 8.4.2.2 Priority of Allocating 5 GHz Channels . . . . . . . . . . . . 242 8.4.2.3 Third-Order Intermodulation . . . . . . . . . . . . . . . . . . . . . 242 8.4.2.4 Near-Far Effects over Multiple Uplink
Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 8.4.3 QoS Provisioning Using Q Learning . . . . . . . . . . . . . . . . . . . . . . . . 244
8.4.3.1 Assumptions and Abbreviations. . . . . . . . . . . . . . . . . . . . 244 8.4.3.2 MDP Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
8.5 Conclusions and Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 8.5.1 Open Issues in QoS Provisioning . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
8.5.1.1 Semi-Markov Decision Process Modeling . . . . . . . . . 250 8.5.1.2 Improving Rate of Convergence . . . . . . . . . . . . . . . . . . . 250 8.5.1.3 Backward Compatibility of QoS Provisioning. . . . . 250 8.5.1.4 Degraded Admission and Dynamic
Source-Coding Adjustment . . . . . . . . . . . . . . . . . . . . . . . . 250 8.5.2 Open Issues in Cognitive WLAN over Fiber
Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 8.5.2.1 Other 802.11 Projects and CWLANoF . . . . . . . . . . . 251 8.5.2.2 Standardization Activities on Radio over Fiber . . . . 251
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252 List of Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
8.1 Introduction Cognitive wireless local area network (WLAN) over fiber (CWLANoF) is a new architecture [1] that applies advanced cognitive radio [2] and advanced broadband radio over fiber (RoF) [3] technologies to infrastructure-based IEEE 802.11 WLAN extended service sets (ESSs) comprised of multiple access points (APs), each forming its own basic service set (BSS), to provide centralized radio resource management (RRM) and equal spectrum access through cooperative spectrum sensing. In this chapter, we examine how this architecture supports QoS provisioning in
a WLAN ESS with a high degree of flexibility. We first review the architecture of CWLANoF [1] and discuss approaches on spectrum sensing and interference avoidance/mitigation in CWLANoF. After surveying existing RRM methods, most of which employ fixed channel assignment (FCA), we discuss how CWLANoF enables new dynamic channel assignment (DCA) strategies, and propose a reinforcement learning (RL) approach for QoS provisioning in CWLANoF. The QoS-provisioning problem is formulated as a Markov decision process (MDP), whose parameters are defined according to the QoS framework specified by 802.11e [4]. We present a solution framework using the Q-learning algorithm [5], which has several advantages that contribute to the suitability of this framework. The symbols and abbreviations frequently used in this chapter are listed in Table 8.1.
