Simulations

1. Tcycle BPS BPS BPS S1 D Sn D S1 D Sn D BPS BPS COORDINATOR Ch = CC 50% Sensors Alive ? Y N SENSOR Send (CC) Y ACK ? Send (BC) N Send (CC) Y ACK ? N Y ACK ? TD Send (CC) N Send (BC) Y ACK ? CC ↨ BC N Y ACK ? University of Brescia Department of Electronics for the Automation A. Flammini, D. Marioli, G. Mazzoleni, E. Sisinni, A. Taroni A LOW POWER SOLUTION FOR WIRELESS SENSOR NETWORKING Actual wireless sensor scenario Proposed solution Power supply / wired link • On-line Coordinator floor noise monitoring (RSSI) in a 2 active channels architecture Channel selection • Few retries for a fast reconnect time • STAR network topology: isochronous time slots allocation with ACK (Si) COORDINATOR COORDINATOR COORDINATOR BPS: battery powered sensor • Low transfer rate (tens bps) • Low cycle time (tens s) • Few sensors (Point to Point, Star Topology) • Several insulated star networks • Additional transceiver to scan all available channels • Reserved “diagnostic” time slot (D) where coordinator computes channels energy • Coordinator dynamically sorts channels according to their floor noise Features: ExperimentalResults Simulations Simulations Test Bench: • Channels divided in 2 groups • Selection of CC (Clear Channel), BC (Backup Channel) • No data from more than 50 % of sensors ? BC  CC • Filtering of noise estimation Coordinator 802.15.4 Coordinator 802.15.4 Sensor 1.5m LeCroy LT374 1.5m Ch = BC Rshunt=1.5Ω Tek RSA3408A “Sniffer” INA110 G=100 Sensor WUSB Sensor WUSB Coordinator • Five retransmission in case of no ACK; 2 attempts on CC plus 1 retransmission on BC then it waits for a variable time before to retry again on BC and finally on CC • BC is free ? CC  BC • Rebinding procedure when failing condition remains for more than 2 cycles CC ↨ BC • WUSB • RF section power consumption (@3.3V): • TX: 69mA, RX:60mA • Sleep: µA, Idle: 2.5mA • 802.15.4 • RF section power consumption (@3.3V): • TX: 29mA, RX:33mA • Sleep: µA, Idle: 1mA N • Performances evaluation varying floor noise FN, burst number BN and burst length BL • Comparison between the proposed solution and standard approach • Index of merit based on Cost where W represents weight of retransmissions (W =1) and rebinding procedures (W=26) Simulated Traffic: channel occupation Simulations 802.15.4 Coordinator RF consumption 802.15.4 Sensor RF consumption • Tx power = 3 dBm, Transfer rate = 250kbps • Data payload = 100 bytes , ACK = 5 bytes • Duty cycle ~ 48 % M = Number of sensors, N = Simulation steps, W = Consumption weight Power spectrum estimation Power spectrum and spectrogram as measured by RSA 3408A RSSI as evaluated by RF transceivers BN = 10, BL = 2000, N = 105, M=10 FN = 0.2 , BL = 2000, N = 105, M=10 FN = 0.2 , BN = 10, N = 105, M=10 Email: {alessandra.flammini,giuseppe.mazzoleni,daniele.marioli,emiliano.sisinni,andrea.taroni}@ing.unibs.it Web Site: http://www.ing.unibs.it/~wsnlab/