- •Introduction
- •Increasing Demand for Wireless QoS
- •Technical Approach
- •Outline
- •The Indoor Radio Channel
- •Time Variations of Channel Characteristics
- •Orthogonal Frequency Division Multiplexing
- •The 5 GHz Band
- •Interference Calculation
- •Error Probability Analysis
- •Results and Discussion
- •IEEE 802.11
- •IEEE 802.11 Reference Model
- •IEEE 802.11 Architecture and Services
- •Architecture
- •Services
- •802.11a Frame Format
- •Medium Access Control
- •Distributed Coordination Function
- •Collision Avoidance
- •Post-Backoff
- •Recovery Procedure and Retransmissions
- •Fragmentation
- •Hidden Stations and RTS/CTS
- •Synchronization and Beacons
- •Point Coordination Function
- •Contention Free Period and Superframes
- •QoS Support with PCF
- •The 802.11 Standards
- •IEEE 802.11
- •IEEE 802.11a
- •IEEE 802.11b
- •IEEE 802.11c
- •IEEE 802.11d
- •IEEE 802.11e
- •IEEE 802.11f
- •IEEE 802.11g
- •IEEE 802.11h
- •IEEE 802.11i
- •Overview and Introduction
- •Naming Conventions
- •Enhancements of the Legacy 802.11 MAC Protocol
- •Transmission Opportunity
- •Beacon Protection
- •Direct Link
- •Fragmentation
- •Traffic Differentiation, Access Categories, and Priorities
- •EDCF Parameter Sets per AC
- •Minimum Contention Window as Parameter per Access Category
- •Maximum TXOP Duration as Parameter per Access Category
- •Collisions of Frames
- •Other EDCF Parameters per AC that are not Part of 802.11e
- •Retry Counters as Parameter per Access Category
- •Persistence Factor as Parameter per Access Category
- •Traffic Streams
- •Default EDCF Parameter Set per Draft 4.0, Table 20.1
- •Hybrid Coordination Function, Controlled Channel Access
- •Controlled Access Period
- •Improved Efficiency
- •Throughput Improvement: Contention Free Bursts
- •Throughput Improvement: Block Acknowledgement
- •Delay Improvement: Controlled Contention
- •Maximum Achievable Throughput
- •System Saturation Throughput
- •Modifications of Bianchi’s Legacy 802.11 Model
- •Throughput Evaluation for Different EDCF Parameter Sets
- •Lower Priority AC Saturation Throughput
- •Higher Priority AC Saturation Throughput
- •Share of Capacity per Access Category
- •Calculation of Access Priorities from the EDCF Parameters
- •Markov Chain Analysis
- •The Priority Vector
- •Results and Discussion
- •QoS Support with EDCF Contending with Legacy DCF
- •1 EDCF Backoff Entity Against 1 DCF Station
- •Discussion
- •Summary
- •1 EDCF Backoff Entity Against 8 DCF Stations
- •Discussion
- •Summary
- •8 EDCF Backoff Entities Against 8 DCF Stations
- •Discussion
- •Summary
- •Contention Free Bursts
- •Contention Free Bursts and Link Adaptation
- •Simulation Scenario: two Overlapping QBSSs
- •Throughput Results with CFBs
- •Throughput Results with Static PHY mode 1
- •Delay Results with CFBs
- •Conclusion
- •Radio Resource Capture
- •Radio Resource Capture by Hidden Stations
- •Solution
- •Mutual Synchronization across QBSSs and Slotting
- •Evaluation
- •Simulation Results and Discussion
- •Conclusion
- •Prioritized Channel Access in Coexistence Scenarios
- •Saturation Throughput in Coexistence Scenarios
- •MSDU Delivery Delay in Coexistence Scenarios
- •Scenario
- •Simulation Results and Discussion
- •Conclusions about the HCF Controlled Channel Access
- •Summary and Conclusion
- •ETSI BRAN HiperLAN/2
- •Reference Model (Service Model)
- •System Architecture
- •Medium Access Control
- •Interworking Control of ETSI BRAN HiperLAN/2 and IEEE 802.11
- •CCHC Medium Access Control
- •CCHC Scenario
- •CCHC and Legacy 802.11
- •CCHC Working Principle
- •CCHC Frame Structure
- •Requirements for QoS Support
- •Coexistence Control of ETSI BRAN HiperLAN/2 and IEEE 802.11
- •Conventional Solutions to Support Coexistence of WLANs
- •Coexistence as a Game Problem
- •The Game Model
- •Overview
- •The Single Stage Game (SSG) Competition Model
- •The Superframe as SSG
- •Action, Action Space A, Requirements vs. Demands
- •Abstract Representation of QoS
- •Utility
- •Preference and Behavior
- •Payoff, Response and Equilibrium
- •The Multi Stage Game (MSG) Competition Model
- •Estimating the Demands of the Opponent Player
- •Description of the Estimation Method
- •Evaluation
- •Application and Improvements
- •Concluding Remark
- •The Superframe as Single Stage Game
- •The Markov Chain P
- •Illustration and Transition Probabilities
- •Definition of Corresponding States and Transitions
- •Solution of P
- •Collisions of Resource Allocation Attempts
- •Transition Probabilities Expressed with the QoS Demands
- •Average State Durations Expressed with the QoS Demands
- •Result
- •Evaluation
- •Conclusion
- •Definition and Objective of the Nash Equilibrium
- •Bargaining Domain
- •Core Behaviors
- •Available Behaviors
- •Strategies in MSGs
- •Payoff Calculation in the MSGs, Discounting and Patience
- •Static Strategies
- •Definition of Static Resource Allocation Strategies
- •Experimental Results
- •Scenario
- •Discussion
- •Persistent Behavior
- •Rational Behavior
- •Cooperative Behavior
- •Conclusion
- •Dynamic Strategies
- •Cooperation and Punishment
- •Condition for Cooperation
- •Experimental Results
- •Conclusion
- •Conclusions
- •Problem and Selected Method
- •Summary of Results
- •Contributions of this Thesis
- •Further Development and Motivation
- •IEEE 802.11a/e Simulation Tool “WARP2”
- •Model of Offered Traffic and Requirements
- •Table of Symbols
- •List of Figures
- •List of Tables
- •Abbreviations
- •Bibliography
Chapter 7
THE GAME MODEL
7.1 |
Overview............................................................................. |
132 |
7.2 |
The Single Stage Game (SSG) Competition Model......... |
133 |
7.3 |
The Multi Stage Game (MSG) Competition Model ........ |
150 |
7.4 |
Estimating the Demands of the Opponent Player.......... |
152 |
7.5 |
Concluding Remark........................................................... |
156 |
THIS CHAPTER introduces a model derived from game theory, that describes the CCHC coexistence problem as a game of decision makers. A game model is based on a set of decision makers (here entities within a
CCHC device) that are called players (Fudenberg and Tirole 1991). The model will be used to analyze the coexistence problem that was identified in the previous chapters. After an overview about the approach taken in the next Section 7.1, Section 7.2 introduces the Single Stage Game (SSG) including the concepts of action, utility, preference and behavior. Section 7.3 introduces the Multi Stage Game (MSG), which will serve for the investigation of static and dynamic strategies, and rational behavior versus cooperation. Further, the prediction method that allows coexisting entities to estimate the demands of other coexisting entities is described in Section 7.4. This prediction method serves as estimator of QoS requirements of different coexisting CCHCs throughout the analysis that follows in the next chapters. The SSG will be used in Chapter 8 for an in-depth analysis of the problem, and for the definition of various kinds of so-called behaviors for coexisting entities.
The MSG will finally serve as the rational behind the concept of cooperation of coexisting entities, as studied in Chapter 9 in the context of the CCHC coexistence problem.
132 |
7. The Game Model |
The vocabulary of game theory is not standardized. In this thesis, the notation and terminology of Osborne and Rubinstein (1994) and Neumann and Morgenstern (1953) are used, with many definitions taken from Fudenberg and Tirole (1991), Debreu (1959), and Green and Heller (1981).
7.1Overview
A dynamic game model is applied to study the CCHC coexistence. The game model comprises a set of players that choose their actions in each stage of the game to maximize their expected own utility in the stage, given their assessment of their opponent’s actions in that particular stage. Utilities are defined in Section 7.2.3. An action of a player is the selection of a certain way of resource allocation by a CCHC. The game model is called dynamic as players periodically adapt their action to the environment after each period of the game. At each game stage a player observes the action of its opponent together with its own utility, which is measured in the CCHC case based on the mutual influence of the player’s interactions, see Section 7.2.3.
The SSG competition model that is discussed in the next section, describes one such stage of the game. Based on that model, the MSG competition model covers the dynamic effects in repeated SSGs. Whereas an SSG is played once, the MSG represents a repeated interaction of players. The MSG competition model helps to understand social phenomena between players that interact for a longer time. Section 7.2 introduces the competition model of the SSG. Section 7.3 extends the SSG to the multi stage case.
In Section 7.4, a prediction method is described that allows a player to estimate the demands of its opponent player. This approach gives way for the usage of game models with complete knowledge, i.e., games where each player determines its action after observing past actions of its opponent players and determining the demands of those opponent players from the observed actions10. However, knowing the demands does not imply that the actual requirements are known to the opponent players. This differentiates the coexistence scenario from an interworking scenario, as discussed earlier in this thesis.
10Games where the interacting players do not have any means to determine the requirements of their opponent player from their observation are referred to as games without complete knowledge.