Fast radio interferometric measurement on low power COTS radio chips A. Bata, A. Bíró, Gy. Kalmár and M. Maróti University of Szeged, Hungary

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1 Fast radio interferometric measurement on low power COS radio chips A. Bata, A. Bíró, Gy. Kalmár and M. Maróti University of Szeged, Hungary ÁMOP-...A-//KONV-0-007: elemedicine oriented research in the fields of mathematics, informatics and medical sciences

2 Localization Ontology Physical phenomena: radeoffs: radio (GPS, radar, WiFi, etc) acoustic (ping, ultrasonic) optical (pics, video, laser) inertial (accelerometer, gyro) magnetic & pressure Ranging: time based (OF, DOA) amplitude based (SI) map based (SI) angle based phase based precision (proximity vs. cm) coverage (global vs. local) responsiveness (immediate) infrastructure (anchors) stealth and security (yes/no) mobile vs. static processing (centralized/local) localization vs. tracking indoor vs. outdoor

3 Localization Ontology Physical phenomena: radeoffs: radio (GPS, radar, WiFi, etc) acoustic (ping, ultrasonic) optical (pics, video, laser) inertial (accelerometer, gyro) magnetic & pressure Ranging: time based (OF, DOA) amplitude based (SI) map based (SI) angle based phase based precision (proximity vs. cm) coverage (global vs. local) responsiveness (immediate) infrastructure (anchors) stealth and security (yes/no) mobile vs. static processing (centralized/local) localization vs. tracking indoor vs. outdoor oday: radio interferometric sensor tracking indoors

4 Radio Interferometric Ranging wo transmitters (A and B) simultaneously send unmodulated sine waves at slightly different frequencies he interference is a high frequency amplitude modulated by a low frequency beat signal wo receivers (C and D) measure the phase of the beat signal at the same time Relative phase offset depends on the distances between A, B, C and D

5 Radio Interferometric Ranging est mode of COS radio gives unmodulated sine wave Beat signal can be measured as signal strength (SI) Quad range: linear combination of four ranges Outdoor experiment: 00 x 0m on football field XSM (CC000) nodes 00-0 MHz carrier Avg. localization error: cm ook 0 minutes long

6 Indoor Radio Interferometry Outdoor solution does not work indoors Phase error depends on carrier frequency CC000 radio is no longer available IDEA: RFA vs. CC000. GHz vs. 0 MHz Single freq tracking Significant speedup DMA like schedule

7 Step : Sensor and RF ment UCMote Proton A DRD Atmega8RFA primary radio with chip antenna 8-bit MHz microcontroller 8 KB ROM, KB RAM IEEE 80.. compliant COS radio chip est mode: unmodulated wave Fixed carrier frequencies need 0-00 KHz offset trim the load capacitance Unpredictable carriers: ±0 KHz Slow reset (switch to test mode) SI signal designed for CCA and LQ low resolution (8 steps) good refresh rate (00 KHz) One measurement: ms

8 Step : Signal Processing Low resolution (8 steps) ime synchronization default is not precise use rising edge Unpredictable beat freq depends on carrier offset we expect 0-00 KHz Dynamic range depends on X powers very small (- steps) Device dependent noise 0. ms processing time

9 Step : Distributed Schedule A X X X S X X X B X X X X S X X C X X X X X S X D S X X X X X X S S xmit sync rcv sync X xmit wave rcv rssi

10 Step : ime Synchronization S ta tb tc imesync Message S mote A mote B X mote C Periodically send synchronization messages to keep in sync Scheduling of measurements on different motes (0 μs precision) Messages can be lost, motes turned on/off, local time drifts

11 Step : Data Extraction and iming SLO ID PERIOD... PERIOD N PHASE... PHASE N IMESAMP All measurements (8-bit period and 8-bit phase) in a frame are packed into a single synchronization message Data is arriving out of order to the base station ment timing Single measurement: ms Synchronization msg:. ms Processing and runtime overhead: ms SuperFrame ( sync msg, measurements): ms One relative phase per pair of transmitters:. ms (80 Hz)

12 Step : Sort Data on Basestation Super Frame Super Frame mote A mote B mote C Sync C Sync B Sync A Sync D Sync C Sync B Sync A Sync D Frame mote D

13 Step 7: Calculate Relative Phases Find matching pair of absolute phase measurements Filter out incorrect measurements different error codes from signal processing unit the two periods are not close enough Calculate relative phase: this is between 0 and π Unwrap relative phases to a number Calculate speed (difference of two consecutive relative phases) Filter out big speed jumps Integrate to get unwrapped phase he unwrapped phase is the level on the surface with the hyperbolic geodesics

14 Demo:

15 hank you! ÁMOP-...A-//KONV-0-007: elemedicine oriented research in the fields of mathematics, informatics and medical sciences