Design and Simulation of Spectrum Management Methods for Wireless Local Area Networks (Advanced Studies Mobile Research Center Bremen)

Growing demands of wireless local area communication are prominent for many day-to-day activities. Applications such as multimedia or VoIP which rely on tight quality-of-service (QoS) support are widely used. In order to handle these applications properly, the data transmission over radio channels should be enhanced by means of spectrum management. Andreas Könsgen describes two major areas of spectrum management, namely the coordination of neighbouring networks with overlapping ranges by controlling different transmission parameters and the channel allocation by the base station inside a radio cell using a cross-layer approach. Theoretical analyses and simulations demonstrate the usage of these methods and show the QoS enhancements which can be achieved. Finally, the author discusses the practical meaning of spectrum management and presents an outlook for future enhancements. Preface Abstract Contents List of Tables List of Figures List of Abbreviations List of Symbols 1 Introduction 2 The IEEE 802.11 Standard Series 2.1 The ISO/OSI Reference Model 2.2 IEEE 802.11 Architecture 2.3 IEEE 802.11 Protocol Stack 2.3.1 IEEE 802.11 PHY Layer 2.3.1.1 OFDM Transmission 2.3.1.2 Structure of the 802.11a PHY PDU 2.3.1.3 Clear Channel Assessment 2.3.2 IEEE 802.11 MAC Layer 2.3.2.1 Contention Window Size Control 2.3.2.2 Interframe Spacing 2.3.2.3 Timing sequence of a 802.11 DCF packet transmission 2.3.3 RTS/CTS Extension 2.3.4 Power Management 2.3.5 Format of the MAC Frame 2.4 IEEE 802.11h Spectrum Management Extensions 2.4.1 Dynamic Frequency Selection 2.4.2 Transmit Power Control 2.4.3 Negotiation of Spectrum Management Capabilities 2.5 Centralised Channel Access 2.6 Enhancing Transmission Speed by MIMO: IEEE 802.11n 2.7 Summary 3 Theoretical Aspects of Wireless LAN Performance 3.1 RelatedWork onWireless LAN Performanceand Spectrum Management 3.1.1 Frequency Channel Selection 3.1.2 Power Control 3.1.3 Link Adaptation 3.1.4 Cross-Layer Design 3.2 Performance of IEEE 802.11Wireless LANs 3.2.1 Throughput 3.2.1.1 Network with Two Stations 3.2.1.2 General Case: Network with n Stations 3.2.2 Delay in Case of Ideal Channel 3.3 Performance in Case of Limited Transmission Ranges 3.3.1 Concurrent Transmissions 3.3.2 Effect of the CCA Threshold 3.3.3 Stations Outside Each Other’s CCA Range 3.3.4 Hidden Stations 3.4 Effects of Spectrum Management on the Capacity 3.4.1 Power Control 3.4.2 Dynamic Frequency Selection 3.4.2.1 Effects on the Performance 3.4.2.2 DFS Convergence Characteristics 3.5 Assigning Airtime in Centralised Operation 3.5.1 Sequential Transmission 3.5.2 Parallelised Transmission 3.6 Summary 4 Spectrum Management Algorithms 4.1 Dynamic Frequency Selection 4.1.1 Acquisition of Measurements 4.1.1.1 Measuring Sequence 4.1.1.2 Measurement Values 4.1.2 Principle of Controllers 4.1.3 Decision Algorithms 4.1.3.1 Least Interfered 4.1.3.2 Fuzzy Logic 4.1.3.3 Genetic Algorithm 4.1.3.4 Introduction of Randomness 4.1.4 Simulated Annealing 4.1.5 Error Recovery 4.2 Transmit Power Control 4.2.1 Infrastructure Networks 4.2.2 Ad-Hoc Networks 4.2.2.1 Initialisation State 4.2.2.2 Testing State 4.2.2.3 Controlling State 4.2.2.4 Monitoring State 4.3 Signalling Issues for Power Control 4.4 Link Adaptation 4.5 Summary 5 Cross-Layer Architecture 5.1 Introduction 5.2 Two-Stage Cross-Layer Scheduler 5.2.1 QoS Aware Scheduler 5.2.2 MIMO-TDMA 5.3 Scheduling for Parallelised Transmissions 5.3.1 MIMO-OFDMA 5.3.2 MIMO-SDMA 5.4 Summary 6 Simulation Environment 6.1 Discrete Event Simulators 6.2 The WARP2 Simulator 6.2.1 Specification and Description Language 6.2.2 Structure of the Simulator 6.3 Simulator Extension by Spectrum Management 6.4 Simulator Extension by Cross-Layer Scheduling 6.5 Summary 7 Simulation Results 7.1 Spectrum Management Results 7.1.1 Network Performance without Spectrum Management 7.1.2 Dynamic Frequency Selection (DFS) 7.1.2.1 Static Scenario 7.1.2.2 Convergence Characteristics 7.1.2.3 Mobility Scenario 7.1.3 Transmit Power Control (TPC) 7.1.3.1 Validation of the Theoretical Model 7.1.3.2 CCA Effect 7.1.3.3 TPC Convergence: Infrastructure 7.1.3.4 TPC Convergence: Ad-Hoc 7.1.3.5 TPC with Variable Load and Number of Stations 7.1.4 DFS and TPC 7.1.4.1 Regular Scenario 7.1.4.2 Irregular Scenario 7.1.5 Integration of DFS, TPC and Link Adaptation (LA) 7.2 Performance of the Cross-Layer Architecture 7.2.1 Cross-Layer Scheduler 7.2.2 Quality-of-Service Scheduling on the MAC Layer 7.2.3 Parallel Transmission of Data 7.3 Summary 8 Conclusions and Outlook 8.1 Conclusions 8.2 Outlook Bibliography Andreas Konsgen describes two major areas of spectrum management: the coordination of neighbouring networks with overlapping ranges by controlling different transmission parameters and the channel allocation by the base station inside a radio cell using a cross-layer approach. Theoretical analyses and simulations demonstrate the usage of these methods and show the QoS enhancements which can be achieved Andreas Koensgen describes two major areas of spectrum management: the coordination of neighbouring networks with overlapping ranges by controlling different transmission parameters and the channel allocation by the base station inside a radio cell using a cross-layer approach.