1. Understanding the Issues in Software Defined Cognitive Radio Jeffrey H. Reed Charles W. Bostian Virginia Tech Bradley Dept. of Electrical and Computer Engineering
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21. 1) Access to spectrum (finding an open frequency and using it) Cognitive radios are a powerful tool for solving two major problems:
22. 2) Interoperability (talking to legacy radios using a variety of incompatible waveforms) Cognitive radios are a powerful tool for solving two major problems:
23. Levels of Radio Functionality Adapted From Table 4-1Mitola, “ Cognitive Radio: An Integrated Agent Architecture for Software Defined Radio, ” PhD Dissertation Royal Institute of Technology, Sweden, May 2000. Level Capability Comments 0 Pre-programmed A software radio 1 Goal Driven Chooses Waveform According to Goal. Requires Environment Awareness. 2 Context Awareness Knowledge of What the User is Trying to Do 3 Radio Aware Knowledge of Radio and Network Components, Environment Models 4 Capable of Planning Analyze Situation (Level 2& 3) to Determine Goals (QoS, power), Follows Prescribed Plans 5 Conducts Negotiations Settle on a Plan with Another Radio 6 Learns Environment Autonomously Determines Structure of Environment 7 Adapts Plans Generates New Goals 8 Adapts Protocols Proposes and Negotiates New Protocols
34. Comment Slide – Delete Before Submitting Following section presented by Reed Needs more work on example SDR architectures
35. Radio Architecture Rx Tx RF Signal Amplify Mixer Filter Amplify Mixer Filter IF Signal Baseband Signal Superhetrodyne RF Signal Amplify Mixer Filter Analog To Digital Converter IF Signal Digital Signal Processing Software Defined Radio
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56. Fundamental Composition of the SCA Keep track of HW in the system Store working environment, bit images, properties, etc. Boot up and maintain HW Keep track of what’s there (installed) Manage collection of resources to create waveform Capabilities e.g., Start and stop, test, describe Connections between resources Device Manager FileSystem Manager Devices Domain Manager Application Factory Resoruces Manage waveform operation Application Port
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63. Knobs and Meters Sample tabulation of knobs and meters by layer (adapted from Prof. Huseyin Arslan) Layer Meters (observable parameters) Knobs (writable parameters) MAC Frame error rate Data rate Source coding Channel coding rate and type Frame size and type Interleaving details Channel/slot/code allocation Duplexing Multiple access Encryption PHY Bit error rate SINR Received signal power Noise power Interference power Power consumption Fading statistics Doppler spread Delay spread Angle of Arrival Transmitter power Spreading type and code Modulation type Modulation index Pulse shaping Symbol rate Carrier frequency Dynamic range Equalization Antenna directivity Other Computational power Battery Life CPU Frequency scaling
73. GA’s and biological metaphor The WSGA uses a genetic algorithm, which operates on chromosomes. The genes of the chromosome represent the traits of the radio (frequency, modulation, bandwidth, coding, etc.). The WSGA creatively analyzes the information from the CSM to create a new radio chromosome.
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91. “ Rules of the Road” ➟ “Rules of the Cognitive Radio” POLICY AWARE Primary User has higher priority over Secondary users Radio emission may be prohibited at certain location or for certain type of radio LOCATION AWARE Precautions for certain areas, such as hospital, airplane, gas station, etc, where RF emission is highly restricted Parking Zone * Source of some pictures in this section: “California Drivers Handbook 2005”; “Illinois Rules of the Road 2004”
92. “ Rules of the Road”-inspired CR Philosophy and Etiquette Insights from “Traffic Model Analogy” TRAFFIC Scheduling Various traffic schedule methods and duplex methods for efficient and fair sharing of congested unlicensed spectrum TDD vs. FDD ➟ Dynamic Uplink/Downlink transmission in TDD mode Spectrum pooling is encouraged Traffic Law ➟ Spectrum Regulations Management by both Punishment and Encouragement FDD mode operation with paired spectrum $ fine
93. A traffic model analogy – Common Issues It is critical that everyone drives sensibly or defensively ➟ Every CR should be aware of Hidden Node problems Hidden Node Problem A and C are unaware of their interference at B, due to A, C cannot hear each other.
94. Vehicle Following Distances for Car Drivers ➟ Time needed to vacate channel after primary user (re-) appears for Cognitive Radios Vehicle Following Distances: TWO-SECOND RULE: Use the two-second rule to determine a safe following distance. A traffic model analogy (cont.)
95. A traffic model analogy (cont.) SPEED LIMIT for car driver ➟ Interference Level Limit (e.g. Max. Allowed Interference Temperature) for Cognitive Radio
96. City Map for Car Drivers ➟ Radio Environment Map (REM) for Cognitive Radios Learning from “Traffic model analogy” for the development of Cognitive Radio… REM Time (or duration) Location (x, y, z), Type of radio environment Local Policy Profile of primary users Profile of interference Max. allowed Interference Level
97. Learning from “Traffic model analogy” for the development of Cognitive Radio…(cont.) Regular conformance check against regulations Language and Etiquette for CR for Signaling and Negotiation
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100. Spectrum Occupancy Study Spectrum occupancy in each band averaged over six locations (Riverbend Park, Great Falls, VA, Tysons Corner, VA, NSF Roof, Arlington, VA, New York City, NRAO, Greenbank, WV, SSC Roof, Vienna, VA) [ Source: FCC NPRM 03-0322. http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-03-322A1.pdf Results from Shared Spectrum Co. and Univ. of Kansas
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105. Spectrum Policy Language Design Actors and Roles Source: BBN Technologies Solutions LLC Area that needs improvements! Spectrum Policy Policy Administrator (e.g. FCC, NTIA) XG System Spectrum Opportunities Awareness via XG Protocols and Sensing query Language Design Knowledge Core Language Model and Representation Policy Language Designer (e.g. BBN/XG Program) Policy Editing and Verification Tools design Machine Readable Policy Instances Policy Repository encode publish Policy Repository
109. Example of a Possible Cognitive Radio Application
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114. Note Daily Drive Home at 5:30 (GPS Aided) Recall Brief Coverage Hole 1. Observe and Analyze Situation 2. Evaluate Alternatives Do Nothing Increase Coding Gain Increase Transmit Power Vertical Handoff Decrease Call Drop Threshold 4. Adapt Network 3. Signal Base Station Request Decrease In Call Drop Threshold CR in a Cellular System
124. DARPA neXt Generation Program: Concepts of Policy Agility (2) Figure drawn from XG Vision RFC Decoupling policies, behaviors, and protocols: Separating what needs to be done from how it is implemented The framework's four key components
125. DARPA neXt Generation Program: Concepts of Policy Agility (3) Machine understandable policies will enable software downloads "on-the-fly" Figure drawn from XG Vision RFC
139. CR Test-bed under development Neighbor WLANs Ethernet Actions Cordless Phone Bluetooth MWOL Tektronix TDS694C: Digital Real-time Oscilloscope Tektronix RSA3408A: Real-Time Spectrum Analyzer Distributed Measurement Collaborative Processing Observations Analysis and decision REM online updating TV station
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151. Predictions for Future Evolution Time SDR with high ASIC content Re-programmable for fixed number of systems Factory reprogrammable Increased use of reconfigurable hardware Limited reconfiguration by user Early cognition Mid-level cognition Cognitive radios 2005 2007 2010 Adaptive spectrum allocation
