Distributed spectrum sensing in unlicensed bands using the VESNA platform

1. Distributed spectrum sensing in unlicensed bands using the VESNA platform Seminar II Student: Zoltan Padrah Mentor: doc. dr. MihaelMohorčič

2. Agenda • Motivation • Theoretical aspects • Practical aspects • Stand-alone spectrum sensing • Distributed spectrum sensing • Spectrum sensing testbed • Experimental results • Conclusions • TODO: - slide number • - date • - location • headers somewhere Seminar II

3. Motivation Seminar II

4. Motivation • Motivation • Theoretical aspects • Practical aspects • Stand-alone spectrum sensing • Distributed spectrum sensing • Spectrum sensing testbed • Experimental results • Conclusions Seminar II • Introduction • Radio spectrum • Regulation • Usage • Using the radio spectrum more efficiently • Approach • Reusing radio frequency bands • Licensed • Unlicensed

5. Introduction 1 • Radio spectrum1 • Many systems use it: AM, FM, TV broadcast, GSM, UMTS, WiFi, GPS, satellite • Systems need to coexist • Avoid disturbance (interference) • Radio spectrum regulation • Frequency band allocation • Each system has its own frequency band Seminar II 1image credit: Roke Manor reseach, 2004

6. 2 Frequency band allocation Seminar II image credit: Roke Manor reseach, 2004

7. 3 Usage of radio spectrum • Studies about radio spectrum utilization Left: Cabric et al: Implemenation issues In spectrum sensing Bottom: Valenta et al: Survey in spectrum utilization in Europe Seminar II

8. Usage of radio spectrum • Studies about radio spectrum utilization Terminal 2 Terminal 3 Left: Cabric et al: Implemenation issues In spectrum sensing Bottom: Valenta et al: Survey in spectrum utilization in Europe Terminal 1 Seminar II

9. Usage of radio spectrum • Studies about radio spectrum utilization Terminal 2 Terminal 3 Left: Cabric et al: Implemenation issues In spectrum sensing Bottom: Valenta et al: Survey in spectrum utilization in Europe Terminal 1 Terminal 4 Seminar II

10. 4 Approach Get information about radio spectrum Take decision on the used frequency band Seminar II

11. Approach Perform database lookup Get information about radio spectrum Perform sensing with a radio Take decision on the used frequency band Seminar II

12. 5 Reusing radio spectrum In licensed bands In unlicensed bands Examples: ISM bands (868 MHz; 2.4 GHz) Multiple equally threated users Spectrum Sharing (SP) • Examples: TV VHF, UHF, GSM bands • Primary user(s) • Secondary user(s) • Dynamic spectrum access (DSA) Seminar II

13. Reusing radio spectrum In licensed bands In unlicensed bands Examples: ISM bands (868 MHz; 2.4 GHz) Multiple equally threated users Spectrum Sharing (SP) • Examples: TV VHF, UHF, GSM bands • Primary user(s) • Secondary user(s) • Dynamic spectrum access (DSA) Seminar II

14. Theoretical aspects Seminar II

15. Theoretical aspects • Motivation • Theoretical aspects • Practical aspects • Stand-alone spectrum sensing • Distributed spectrum sensing • Spectrum sensing testbed • Experimental results • Conclusions Seminar II Problem formulation Goals Hidden terminal and exposed terminal situations Spectrum sensing Energy detection

16. 6 Problem formulation • For solving the artificial spectrum scarcity problem, it is necessary: • Experimental-driven research • Experimental validation and improvement of sensing algorithms We assume that either: a radio communication experiment is prepared in an ISM radio frequency band the radio activity in an ISM band is of interest at a given location In both cases external interference might be observed. Seminar II Testbed is needed

17. 7 Goals Seminar II • Defining the system architecture for a testbed • Developing software that allows performing spectrum sensing with the VESNA platform • Spectrum sensing: • Calibration of multiple VESNA devices • Evaluation of their performance • Performing experiments with them • Implementation of the functionalities needed for • Integrating multiple VESNA devices in a testbed • Communication system of the testbed, supporting experiments • Experimental evaluation of the performance of a VESNA-based spectrum sensing testbed.

18. 8 Hidden terminal and exposed terminal situations • Idea: use multiple radios for observation • Each radio performs partial detection • Results are centralized • Resolves the problems: • Hidden transceiver • Hidden receiver • Relies on other methods for partial detection Seminar II

19. 9 Spectrum sensing • Detecting other radios • Spectrum sensing methods • Energy detection • Eigenvalue based detection • Cyclostationary feature detection • Matched filter detection • Collaborative sensing Seminar II

20. 10 Energy detection • Idea: measure the energy in frequency band and compare it to a threshold • Simple to implement • Needs correct threshold value: noise floor • Does not work well with spread spectrum signals Seminar II

21. Practical aspects Seminar II

22. Practical aspects Todo, agenda style • Motivation • Theoretical aspects • Practical aspects • Stand-alone spectrum sensing • Distributed spectrum sensing • Spectrum sensing testbed • Experimental results • Conclusions Seminar II Used devices VESNA platform Spectrum sensing framework

23. 11 Used devices Seminar II • Sensor network based testbed • VESNA platform • Low-cost, low-complexity • CC1101 radio – 868 MHz ISM band • CC2500 radio – 2.4 GHz ISM band • The radios can only provide RSSI values • Only energy detection is possible

24. 12 VESNA platform • Developed at Jozef Stefan Institute • ST ARM Cortex-M3, 64 MHz • JTAG, USB, USART PC interface • I2C, SPI, PWM, ADC, DAC, USART sensor and actuator interfaces • Code library: C/C++ (GCC) • 300-900 MHz, 2.4 GHz radio interface (all ISM bands); • TI CC1101, TI CC2500 • Software tools: Open Source • Eclipse IDE • Tool-chain: GNU Compiler Collection • Cygwin, Linux environment for Windows • JTAG server: OpenOCD • JTAG hardware interface: Olimex ARM-USB-OCD Seminar II

25. VESNA platform • Developed at Jozef Stefan Institute • ST ARM Cortex-M3, 64 MHz • JTAG, USB, USART PC interface • I2C, SPI, PWM, ADC, DAC, USART sensor and actuator interfaces • Code library: C/C++ (GCC) • 300-900 MHz, 2.4 GHz radio interface (all ISM bands); • TI CC1101, TI CC2500 • Software tools: Open Source • Eclipse IDE • Tool-chain: GNU Compiler Collection • Cygwin, Linux environment for Windows • JTAG server: OpenOCD • JTAG hardware interface: Olimex ARM-USB-OCD • Performance: • Comparable to other sensor node platforms, like TelosB or Sensinode • Lot less processing power than a PC Seminar II

26. 13 Spectrum sensing framework Control system Communication and control On-line processing Radio VESNA Data storage Communication interface Off-line processing Seminar II

27. Standalone spectrum sensing Seminar II

28. Standalone spectrum sensing • Motivation • Theoretical aspects • Practical aspects • Stand-alone spectrum sensing • Distributed spectrum sensing • Spectrum sensing testbed • Experimental results • Conclusions Seminar II • Goals • Experimental setup • Calibration results • CC2500 • CC1101

29. 14 Goals Seminar II Implementation of spectrum sensing functionality Calibration of the prototype

30. 15 Experimental setup Coaxial Cable Signal generator VESNA Generated signal level Measured signal level Offset value Seminar II

31. 16 Calibration – CC2500 Seminar II Absolute error: < 6 dB Nonlinearity: < 2 dB

32. 17 Calibration – CC1101 Seminar II Absolute error: < 8 dB Nonlinearity: < 0.5 dB

33. 18 Calibration – CC1101 Malfunction Seminar II

34. Distributed spectrum sensing Seminar II

35. Distributed spectrum sensing • Motivation • Theoretical aspects • Practical aspects • Stand-alone spectrum sensing • Distributed spectrum sensing • Spectrum sensing testbed • Experimental results • Conclusions Seminar II • Goals • Demonstration • Devices • Environment • Representative results • Device comparison • Introduction • Environment • Results

36. 19 Goals Seminar II • Demonstrate the functioning of heterogeneous sensing system • Benchmark • Devices • Combinations of devices

37. 20 Demonstration – devices Seminar II • eZ430-RF2500 • Texas Instruments wireless development tool • MSP430 CPU • CC2500 radio • USRP2 • Universal Software Radio Peripheral • SBX daugthterboard • Software defined radio device • GNU radio software • VESNA • CC2500 radio

38. 21 Demonstration – environment Seminar II

39. 22 Representative results Seminar II

40. 23 Device comparison Path loss model with parameters Measurement results from devices Fitting For each device Parameter values Error relative to the model Comparison Seminar II

41. Device comparison Path loss model with parameters Measurement results from devices Fitting For each device Parameter values Error relative to the model Comparison Seminar II

42. Device comparison TODO intro More text, because work has been done • One static continuous transmission • Multiple measurement locations Path loss model with parameters Measurement results from devices Fitting For each device Parameter values Error relative to the model Comparison Seminar II

43. Device comparison • One static continuous transmission • Multiple measurement locations Path loss model with parameters Measurement results from devices Fitting For each device Parameter values Error relative to the model Mean Squared Error (MSE): average of squared error values for each data point Comparison Seminar II

44. 24 Environment Seminar II

45. 25 Results - plotted Seminar II

46. 26 Results - numerical Seminar II

47. Spectrum sensing testbed Seminar II

48. Spectrum sensing testbed • Motivation • Theoretical aspects • Practical aspects • Stand-alone spectrum sensing • Distributed spectrum sensing • Spectrum sensing testbed • Experimental results • Conclusions Seminar II • Architecture • Goals • Requirements • Constraints • Measurements • Setup • Representative results

49. 27 Architecture Seminar II

50. Architecture • Functionality abstracted in resources • RESTful design: GET and POST requests • All nodes addressable • Requests initiated by management and control part Seminar II