Fundamentals of Cognitive Radio
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List of Figures xv
List of Tables xxiii
Preface xxv
Acknowledgments xxvii
Acronyms xxix
1 Introduction 1
1.1 The Fourth Industrial Revolution 1
1.2 Cognitive Radio 4
1.3 The Spectrum-Underutilization Problem 7
1.4 Countrywide Measurements of Spectrum Utilization 8
1.5 Why be Interested in Cognitive Radio Networks? 9
1.6 Directed Information Flow 11
1.7 Cognitive Radio Networks 14
1.8 Mathematical Toolbox 17
1.8.1 Game Theory 17
1.8.2 Control Theory 18
1.8.3 Optimization under Uncertainty 19
1.9 Dominant Sources of Uncertainty in Cognitive Radio Networks 20
1.10 Issue of Trustworthiness 22
1.11 Vision for the Book 22
2 GameTheory 25
2.1 Game Theory Terminology 25
2.1.1 Noncooperative Games versus Cooperative Games 26
2.1.2 Static Games versus Dynamic Games 26
2.1.3 One-Shot Games versus Repeated Games 26
2.1.4 Games with Complete Information versus Games with Incomplete Information 26
2.1.5 Games with Perfect Information versus Games with Imperfect Information 26
2.2 Noncooperative Games 27
2.2.1 Nash Equilibrium 28
2.2.2 Variational Inequalities 28
2.3 Cooperative Games 28
2.3.1 Nash Bargaining 29
2.4 Minority Games 29
2.5 Concluding Remarks 30
3 Cognitive Radio Transceiver 31
3.1 Spectrum Sensing 32
3.1.1 Attributes of Reliable Spectrum Sensing 33
3.1.2 The Multitaper Method 33
3.1.3 Space-Time Processing 38
3.1.4 Time-Frequency Analysis 41
3.1.5 Cyclostationarity: Fourier Perspective 50
3.1.6 Rayleigh Fading Channels 54
3.1.7 Remarks on Nonparametric Spectrum Sensing 55
3.1.8 Filter-Bank Implementation of the Multitaper Method 57
3.1.9 Cooperative Spectrum Sensing 57
3.2 Dynamic Spectrum Management 58
3.2.1 The Tsigankov-Koulakov Model 60
3.2.2 Self-Organizing Dynamic Spectrum Management 61
3.2.3 Dynamic Spectrum Management Based on Minority Games 68
3.2.4 Self-Organized Maps versus Minority Games 70
3.3 Transmit-Power Control 71
3.3.1 Waterfilling Interpretation of Information Capacity Theorem 75
3.3.2 Iterative Waterfilling Algorithm (IWFA) 77
3.3.3 IWFA as a Multistage Optimization Problem in Light of System Uncertainties 80
3.3.4 Robust IWFA 80
3.3.5 The Price of Robustness 81
3.3.6 Robust IWFA versus Classic IWFA 82
3.4 Information Value 91
3.5 Concluding Remarks 93
4 Cognitive Radio Networks 94
4.1 Cognitive Radio Networks Viewed as Spectrum-Supply Chain Networks 94
4.2 Open-access Cognitive Radio Networks 99
4.2.1 Network Dynamics 102
4.2.2 Cognitive Radio Network Viewed as a Hybrid Dynamic System 109
4.2.3 Network Stability in the Presence of Uncertainty and Time Delay 111
4.2.4 Double-layer Dynamics of Cognitive Radio Networks 115
4.3 Market-driven Cognitive Radio Networks 121
4.3.1 Legacy Owners 124
4.3.2 Spectrum Brokers 125
4.3.3 Secondary Users 126
4.3.4 Equilibrium of the Spectrum-Supply Chain Network 127
4.3.5 Network Dynamics 129
4.3.6 Network Stability 129
4.3.7 The Transportation Network Representation of the Spectrum-Supply Chain Network 129
4.4 Supply Chain Efficiency 131
4.5 Concluding Remarks 133
4.5.1 Two Regimes of Cognitive Radio Networks 133
4.5.2 Supply Chain Networks 135
4.5.3 Cognitive Radio Commercialization 136
4.5.4 The Role of Cognition in Cognitive Radio Networks 137
5 Sustainability of the Spectrum-Supply Chain Network 140
5.1 Unlicensed Bands as Public Goods 140
5.2 The Spectrum-Supply Chain Network as an Artificial Economy 142
5.3 Aiming for Lindahl Equilibria 144
5.4 Concluding Remarks 147
6 Cognitive Heterogeneous Networks 148
6.1 Heterogeneous Networks 148
6.2 Horizontal Mergers of Spectrum-Supply Chain Networks 151
6.2.1 Premerger Status 151
6.2.2 Spectrum Sharing 154
6.2.3 Infrastructure Sharing 155
6.2.4 Spectrum and Infrastructure Sharing 155
6.3 Synergy Measure for Horizontal Mergers 155
6.4 Concluding Remarks 156
Appendix A Mathematical Model for Open-Access Cognitive
Radio Networks 157
Appendix B Proof of Theorems 167
References
List of Figures
- Figure 1.1 The cognitive information-processing cycle in cognitive radio. A cognitive radio transceiver is built on a perception-action cycle. Radio-scene analyzer in the receiver plays the role of the perceptor. Dynamic spectrum manager and transmit power controller in the transmitter play the role of the executive part. The perceptual and executive parts together with the feedforward and feedback channels form a closed-loop system.
- Figure 1.2 Directed-information flow in cognitive radio. DSM: dynamic spectrum manager; TPC: transmit-power controller; RSA: radio-scene analyzer; RX: receiver; TX: transmitter; TX CR: transmitter unit in the transceiver of cognitive radio; RX CR: receiver unit in the transceiver of cognitive radio.
- Figure 3.1 Diagrammatic depiction of singular value decomposition applied to the matrix of (3.13).
- Figure 3.2 Illustrating the one-to-one correspondences between the Loève and Fourier theories for cyclostationarity. Basic instrument for estimating (a) the Loève spectral correlations of a time series and (b) the Fourier spectral correlations of cyclostationary signal .
- Figure 3.3 A self-organizing map: (a) initial state and (b) organized state.
- Figure 3.4 Block diagram of an OFDM transceiver.
- Figure 3.5 Waterfilling interpretation of the information-capacity theorem.
- Figure 3.6 Multihop communication path between a source node and a destination node.
- Figure 3.7 Effect of user mobility on the communication path: (a) partially changed, (b) completely changed with respect to the path shown in Figure 3.6.
- Figure 3.8 Resource-allocation results of simultaneous IWFA, when two new users join a network of five users and interference gains are changed randomly due to mobility of the users: (a) transmit powers of three users on two subcarriers, (b) data rates of three users and the total data rate in the network.
- Figure 3.9 Resource-allocation results of simultaneous robust IWFA, when two new users join a network of five users and interference gains are changed randomly due to mobility of the users: (a) transmit powers of three users on two subcarriers, (b) data rates of three users and the total data rate in the network.
- Figure 3.10 Resource-allocation results of simultaneous IWFA, when two new users join a network of five users, a subcarrier disappears, and interference gains are changed randomly due to mobility of the users: (a) transmit powers of three users on four subcarriers, (b) data rates of three users and the total data rate in the network.
- Figure 3.11 Resource-allocation results of simultaneous robust IWFA, when two new users join a network of five users, a subcarrier disappears, and interference gains are changed randomly due to mobility of the users: (a) transmit powers of three users on four subcarriers, (b) data rates of three users and the total data rate in the network.
- Figure 3.12 Resource-allocation results of IWFA, when interference gains change randomly with time and users use outdated information to update their transmit powers: (a) time-varying delays introduced by each user's feedback channel. Sum of transmit power and interference plus noise for four users achieved by (b) classic IWFA and (c) robust IWFA. Dashed lines show the limit imposed by the permissible interference power level.
- Figure 4.1 The spectrum-supply chain network in its basic form with two tiers: legacy owners and secondary users. In each tier of the network, a noncooperative game is played among the peers. In a market-driven regime, legacy owners compete against each other to gain more benefit from leasing their underutilized subbands, and secondary users compete against each other to get a better share from unlicensed bands and a share of the licensed bands at a lower price if needed. In an open-access regime, only one game is played among secondary users to get a better share from unlicensed bands as well as the idle licensed subbands of legacy owners.
- Figure 4.2 The extended spectrum-supply chain network for market-driven regime with three tiers: legacy owners, spectrum brokers, and secondary users. In each tier of the network, a noncooperative game is played among the peers. Legacy owners compete against each other to gain more benefit from leasing their underutilized subbands. Spectrum brokers compete against each other to maximize their profit by buying the right of using underutilized licensed subbands from legacy owners at a lower price and selling it to secondary users at a higher price. Secondary users compete against each other to get a better share from unlicensed bands and a share of the licensed bands at a lower price if needed.
- Figure 4.3 Decentralized hierarchical control structure in a cognitive radio network. Licensed bands are occupied and released according to the communication activities of primary users. These activities, which are discrete events, may be interpreted as the actions of a high-level network controller. On the other hand, the resource-allocation algorithms, which are employed by secondary users, may be viewed as local controllers. These local controllers are two-level controllers that handle channel assignment and transmit-power adjustment in a hierarchical manner.
- Figure 4.4 Two-level control scheme for cognitive radio. The controller is a hierarchical hybrid system. In the control hierarchy, the supervisory-level controller has a higher rank with respect to the field-level controller. The supervisory-level controller is an event-triggered controller and handles channel selection according to the primary users' communication patterns, which lead to appearance and disappearance of spectrum holes. In a cognitive radio, the dynamic spectrum manager plays the role of the supervisory-level controller. On the other hand, the field-level controller is a continuous state-based controller that adjusts the transmit power over the set of chosen channels. In a cognitive radio, the transmit-power controller plays the role of the field-level controller.
- Figure 4.5 Geometric interpretation of variational inequalities. For all in the feasible set, the equilibrium point denoted by satisfies the inequality .
- Figure 4.6 Geometric interpretation of projected dynamic systems. In a projected dynamic system, the state trajectory is confined to the feasible set by a projection operator. The state equation of such systems has a discontinuous right-hand side due to the projection operator.
- Figure 4.7 A two-player packet-forwarding scenario.
- Figure 4.8 Payoff matrix for a symmetric two-player packet-forwarding game.
- Figure 4.9 A two-player relaying scenario.
- Figure 4.10 Power trajectories for a network of three users with three available subcarriers obtained from the associated PDS, when both the interference gains and the number of subcarriers change by time. Direction of evolution of states and the achieved equilibrium points are shown by arrows and asterisks, respectively. Trajectories enter lower dimensional spaces when spectrum holes disappear and then, go back to higher-dimensional spaces again, when new spectrum holes are available. When the second subcarrier is not idle, trajectories enter plane and when the third subcarrier is not also idle anymore, trajectories enter line. After a while when third and then second subcarriers become available again, state trajectories go back to plane and then space.
- Figure 4.11 Solution stability analysis. Solution of the perturbed system converges to the solution of the original system (shown by asterisks) as the perturbed system approaches the original system. Results are depicted for different subcarriers separately: (a) subcarrier 1, (b) subcarrier 2, and (c) subcarrier 3. Arrows show the direction of convergence.
- Figure 4.12 Power trajectories for a network of three users with three available subcarriers obtained from the associated multiple-time-varying-delay PDS with uncertainty, when both the interference gains and the number of subcarriers change by time. Direction of evolution of states and the achieved equilibrium points are shown by arrows and asterisks, respectively. Trajectories enter lower dimensional spaces when spectrum holes disappear and then, go back to higher-dimensional spaces again, when new spectrum holes are available. When the second subcarrier is not idle, trajectories enter plane and when the third subcarrier is not also idle anymore, trajectories enter line. After a while when second and then third subcarriers become available again, state trajectories go back to plane and then space.
- Figure 4.13 Time-varying delays introduced by feedback channels in transmit power control loops for a network of three users.
- Figure 4.14 Timescale decomposition in a three-dimensional space. A change in communication patterns of primary users is viewed as a discrete event and corresponds to a rapid motion from a two-dimensional space to another one. In each one of the two-dimensional spaces, dynamic spectrum management and transmit power control are associated with the two axes.
- Figure 4.15 Relationship between different notions of monotonicity. Strong monotonicity implies strict monotonicity, which, in turn, implies monotonicity. By the same token, strong pseudo-monotonicity implies strict pseudo-monotonicity, which, in turn, implies pseudo-monotonicity. Furthermore, strong monotonicity, strict...
