logging in or signing up QualTalk April25 Breezy Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINTLite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 112 Category: Entertainment License: All Rights Reserved Like it (0) Dislike it (0) Added: October 29, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript Designing Self-Sustainable Photovoltaic Sensor Network: Designing Self-Sustainable Photovoltaic Sensor Network Jaein Jeong Qualifying Exam April 25th, 2006Target Environment: Target Environment Outdoor application Wired power and battery has limitations. Solar energy is available, but budget varies. Large-scale, multi-hop networks Multi-hop is needed to cover large WSN. Power saving for multi-hop is not easy. RADIO ON for synchronizing nodes. RADIO OFF for power saving. Power saving for single-hop is trivial.Related Work on Solar Powered Sensor Network: Related Work on Solar Powered Sensor Network Trio [DHJ+06] Real deployment of large sensor nodes. Multi-hop routing. Operate only for several hours with full radio cycle. Other Previous Works RF transmit beacon [ROC+03], Prometheus [JPC05] Heliomote [RKH+05], ZebraNet [ZSLM04]Goals: Goals Power saving for multi-hop networks under solar energy source. Solar Energy: time-varying, low-rate Battery: constant rate, possibly at high rateApproaches: Approaches Modeling energy budget and consumption. Energy budget: Analysis of varying solar radiation. Energy consumption: Estimation based on on-off duty-cycle and power consumption measurement of Trio. Experiments with single-hop & on-off duty-cycle. Proposal of ideas that can achieve low duty-cycling in multi-hop under varying solar energy.Organization: Organization Introduction Modeling of energy budget, consumption (a) Solar energy budget (b) Energy consumption and duty-cycling (c) Charging and energy storage Power saving in multi-hop networks under solar energy Experiment and Discussion Future workOrganization: Organization Introduction Modeling of energy budget, consumption (a) Solar energy budget (b) Energy consumption and duty-cycling (c) Charging and energy storage Power saving in multi-hop networks under solar energy Experiment and Discussion Future workModeling of Energy Budget – Solar Energy Radiation: Modeling of Energy Budget – Solar Energy Radiation Need to model solar energy as variable that can change over time. Solar irradiance is assumed as 100mW/cm2 (= 1kW/m2), but varies on time and location. We can model solar radiation as PSH. For solar cell outputting Psolar at 100mW/cm2, available energy Eavail can be calculated as:Modeling of Energy Budget – Solar Energy Radiation (cont.): Modeling of Energy Budget – Solar Energy Radiation (cont.) Modeling solar radiation at a specific location: Requires meteorological data. We used data from Meteonorm software. Example: PSH for San Francisco, CA Max: 7.35 hours in Jul Min: 1.97 hours in Dec Avg: 4.71 hoursModeling of Energy Budget – Solar Cell Energy Conversion: Modeling of Energy Budget – Solar Cell Energy Conversion Power converted by solar cell is given by: Psolar = Area * Efficiency * Irradiance Estimate Psolar for solar cell used for Trio. Also consider Psolar for previous works.Modeling of Energy Budget – Solar Cell Energy Conversion (cont.): Modeling of Energy Budget – Solar Cell Energy Conversion (cont.) Load Constraint: I-V char. is given: Vp, Ip, Pmax Output voltage ≤ 5.1V due to Zener diode. Space Constraint: Dimension L and W are given. Maximize solar cell output power by connecting multiple solar cells in parallel within the area. 10cm by 10cm Modeling of Energy Budget – Solar Cell Energy Conversion (cont.): Modeling of Energy Budget – Solar Cell Energy Conversion (cont.) Solar cell module output based on published rates with output load and space constraints:Modeling of Energy Consumption – Trio Node: Modeling of Energy Consumption – Trio Node Power consumption for duty-cycle rate R: Pcons = R*Pactive + (1-R)*Psleep Daily energy consumption: Eday = Pcons * 24 hours Trio node power consumption measurement: Radio consumes most power. Reducing radio duty-cycle will reduce power consumption.Modeling of Energy Consumption – Trio Node (cont.): Modeling of Energy Consumption – Trio Node (cont.) 1 solar-cell case: 2 solar-cell case: 25% for all the year 10% for all the year 100% for Apr. to Sep. 50% for Apr. to Sep. Location: San FranciscoCharging to Energy Storage Element: Charging to Energy Storage Element Supercap for primary, lithium-ion for secondary. Reduces battery charging frequency. Software-controlled battery charging. Unlike other batteries, Li+ battery should be charged only when there is sufficient charge in the supercap. Pros: Simple hardware: micro-controller, DC-DC converter, analog switch. Cons: Requires correct software for charging control.Consideration of other types of storage element: Consideration of other types of storage element Battery is needed during overcast days. Supercap-only method doesn’t have sufficient capacity. Comparison of charging efficiency is not available yet.Organization: Organization Introduction Modeling of energy budget, consumption (a) Solar energy budget (b) Energy consumption and duty-cycling (c) Charging and energy storage Power saving in multi-hop networks under solar energy Experiment and Discussion Future workRelated Work on Duty-Cycling: Related Work on Duty-Cycling Protocols with no synchronization: Prometheus, Heliomote Periodic turns on/off, no synchronization. Low power MAC protocols: Dual channel (data + control): PAMAS [SR98] Synchronous: S-MAC [YHE02], T-MAC [vDL03] Asynchronous: B-MAC [PHC04], Seesaw [BSE06] Network level protocols: system-wide energy scheduling. FPS [HDB04], VigilNet [HKL+05], LEACH [HCB00]Limitation of previous low duty-cycle protocols: Limitation of previous low duty-cycle protocols Previous protocols use single duty-cycle rate. Works well for battery. Could drain energy source for time varying source. We need a low duty-cycle protocol that can adjust rate based on solar energy.Interfacing low-power network protocol with energy harvesting: Interfacing low-power network protocol with energy harvesting Energy monitor notifies change in solar radiation. Use CapVol due to high correlation among nodes. Low-power network protocol adjusts the duty-cycle when notified. Low-power network protocol Energy Monitoring Module Change in energy condition Set duty-cycleImplementing Duty-Cycling for Trio: Implementing Duty-Cycling for Trio Needs to address system dependent issues. Use of low level timer is dependent on Atmel μ-controller. Use of long preamble works for CC1000, not for CC2420. Instead of long preamble, a sender can send multiple packets with same interval [Seesaw: BSE06].Duty-Cycling Estimation for Seesaw Implementation: Duty-Cycling Estimation for Seesaw Implementation Facts and assumptions TinyOS packet length: 39 bytes, CC2420 data rate: 250 kbps Tperiod <= 1000 ms due to latency requirement Tpacket >= 39 bytes/250 kbps = 1.248 ms, let Tpacket=1.5ms Estimating performance metric Duty-cycle rate = Tlisten/Tperiod = 2Tsend/Tperiod = 2Tsend/(λTperiod) Date rate = 1 packet / Tperiod Seesaw implementation could achieve 1.5% duty-cycle at λ = 0.2.Organization: Organization Introduction Modeling of energy budget, consumption (a) Solar energy budget (b) Energy consumption and duty-cycling (c) Charging and energy storage Power saving in multi-hop networks under solar energy Experiment and Discussion Future workExperiment: Experiment Measurements: April 6th, 2006 – April 9th, 2006 Metrics to measure: Vcc, BatVol, CapVol Power source, Charging and Duty-cycle. Duty cycling: Naïve duty-cycling, no use of low-power MAC Two mode: normal (12.5%) & low duty-cycle (1.56%) Communication: Single hop btw. each Trio and the base. Sending rate: once every 4 sec with radio on.Experiment Setting – Power source check logic: Experiment Setting – Power source check logic Power source logic Charging logic Run on Cap Run on Bat (3) Low Vcc, High Bat: Vcc < 2.7V and BatVol >= 2.8V (1) Low Vcc, Low Bat: (1) Vcc < 2.7V and BatVol >= 2.8V (2) High Vcc, High Cap: Vcc >= 2.7V and CapVol >= 3.0V Charging No Charging (1) High Radiation: BatVol < 4.1V and CapVol >= 3.3V (2) USB Charging: BatVol < 4.1V and plugged to USB (3) Low Radiation: BatVol < 4.1V CapVol >= 3.0V (3) Overcharging: BatVol >= 4.1VExperiment: One day trend – Verifying the charging logic: Experiment: One day trend – Verifying the charging logic Charging was done from 13:00 to 18:00 Gradual increase in BatVol Average CapVol reached 3.1V during the peak Experiment: One day trend – Balancing Energy Consumption: Experiment: One day trend – Balancing Energy Consumption Trio nodes maintain about the same level for BatVol and CapVol while operating continuously. Experiment: Four day trend – BatVol, CapVol variation with weather: Experiment: Four day trend – BatVol, CapVol variation with weather Battery voltage drops over successive overcast daysSummary of Experiment Results : Summary of Experiment Results Charging logic is correctly working. Naïve duty-cycling with single-hop traffic works sustainably over sunny or cloudy days. Battery level decreases over successive overcast days. Research Timeline: Research Timeline May 2006 to December 2006: Implementation and evaluation of low duty-cycle MAC and network protocol for Trio. Comparative analysis of energy storage design. January 2007 to August 2007: Dissertation work. References: References [BSE06] Rebecca Braynard, Adam Silberstein, and Carla Ellis. Extending network lifetime using an automatically tuned energy-aware mac protocol. IEEE EWSN, Feb. 2006. [DHJ+06] Prabal Dutta, Jonathan Hui, Jaein Jeong, Sukun Kim, Cory Sharp, Jay Taneja, Gilman Tolle, Kamin Whitehouse, and David Culler. Trio: Enabling sustainable and scalable outdoor wireless sensor network deployments. IEEE SPOTS in submission, 2006. [HCB00] Wendi Rabiner Heinzelman, Anatha Chandrakasan, and Hari Balakrishnan. Energy-efficient communication protocols for wireless microsensor networks. Proceedings of the Hawaii International Conference on Systems Science, Jan. 2000. [HDB04] Barbara Hohlt, Lance Doherty, and Eric Brewer. Flexible power scheduling for sensor networks. IEEE IPSN, Apr. 2004. [HKL+05] Tian He, Sudha Krishnamurthy, Liqian Luo, Ting Yan, Lin Gu, Radu Stoleru, Gang Zhou, Qing Cao, Pascal Vicaire, John A. Stankovic, Tarek F. Abdelzaher, Jonathan Hui, and Bruce Krogh. Vigilnet: An integrated sensor network system for energyefficient surveillance. ACM Transactions on Sensor Networks, 2005. [JPC05] Xiaofan Jiang, Joseph Polastre, and David Culler. Perpetual environmentally powered sensor networks. IEEE SPOTS, 2005. [PHC04] Joseph Polastre, Jason Hill, and David Culler. Versatile low power media access for wireless sensor networks. ACM Sensys, Nov. 2004. References – cont.: References – cont. [RSF+04] Shad Roundy and Dan Steingart and Luc Frechette and Paul Wright and Jan Rabaey, Power Sources for Wireless Sensor Networks, IEEE EWSN, 2004. [RKH+05] Vijay Raghunathan, Aman Kansal, Jason Hsu, Jonathan Friedman, and Mani Srivastava. Design considerations for solar energy harvesting wireless embedded systems. IEEE SPOTS, 2005. [Rou03] Shad J. Roundy. Energy scavenging for wireless sensor nodes with a focus on vibration to electricity conversion. Ph.D Thesis, University of California at Berkeley, May 2003. [RU6] The ru6730 photo battery. http://rusolar.com/products.ru6730.html. [RWAM05] Injong Rhee, Ajit Warrier, Mahesh Aia, and Jeongki Min. Zmac: a hybrid mac for wireless sensor networks. ACM Sensys, Nov. 2005. [Sola] Power film - flexible solar panels. http://www.solar-world.com/PowerFilm.htm. [Solb] Solar panels - high efficiency. http://www.solar-world.com/SolarPanels.htm. [SR98] Suresh Singh and C. S. Raghavendra. Pamas - power aware multi-access protocol with signalling for ad hoc networks. ACM SIGCOMM, 1998. [SSC05] F. Simjee, D. Sharma and P. H. Chou, “Everlast: Long-life, Supercapacitor-operated Wireless Sensor Node” [Sun] Panasonic solar cells technical handbook ‘98/99. http://downloads.solarbotics.com/PDF/sunceramcat.pdf. [vDL03] Tijs van Dam and Koen Langendoen. An adaptive energyefficient mac protocol for wireless sensor networks. ACM Sensys, Nov. 2003. [YHE02] Wei Ye, John Heidemann, and Deborah Estrin. An energyefficient mac protocol for wireless sensor networks. IEEE INFOCOM, 2002. Possible Questions: Possible QuestionsPossible Questions: Possible Questions Why do we use solar energy? Solar energy has the highest energy density among energy harvesting methods. Commercially available. [RSF+04]Possible Questions: Possible Questions How about just using batteries? Non-rechargeable lithium batteries have high energy density. Even the high density battery have limited lifetime From Digikey.comPossible Questions: Possible Questions For power saving, duty-cycling is needed. Single-hop case: Sender duty-cycles, but receiver is always on. Synchronized when sender is awake. Multi-hop case: Both sender and receiver duty-cycle radio. Synchronized when both sender and receiver are awake. Possible Questions: Possible Questions Definitions and Units Spectral irradiance (W/m2μm): Power received by a unit surface area in a wave length differential dλ. Irradiance (W/m2): Integral of the spectral irradiance extended to all wavelengths of interest. Radiation (kWh/m2): Time integral of the irradiance over a given period of time.Possible Questions: Possible Questions I-V characteristic varies depending on the solar irradiance. From “Modelling Photovoltaic Systems Using PSpice” by Luis Castaner, Santiago SilvestrePossible Questions: Possible Questions Load Limitation with Zener diode: The reverse voltage across the Zener diode is regulated below VZener as long as the current is limited to a certain level.Possible Questions: Possible Questions Capacity of supercap: Ecap = ½ CVmax2 + ½ CVmax2 = CVmax2 = 22F * (2.5V)2 = 137.5 J = 38.2 mWh Capacitor of battery: Ebat = C * V = 750mAh * 3.5V = 2625 mWh Supercap alone is not sufficient for overcast days: Eday for 10% = 181 mWh Bday: # days a node can operate with no sunlight. Bday = Ebat / EdayPossible Questions: Possible Questions Heliomote Battery Capacity: Ebat = 2 * C * V = 2 * 1800mAh * 1.2V = 4320 mWh Everlast Capacitor Capacity: Ecap = ½ CVmax2 = ½ * 100F * (2.5V)2 = 312.5 J = 86.8 mWh Bday: # days a node can operate with no sunlight. Bday = Ebat / Eday or Ecap / Eday Possible Questions: Possible Questions Possible receiver duty cycle with Seesaw: TinyOS packet length on CC2420: 39 bytes 8 bytes header, 2 bytes footer, 29 bytes data CC2420 data rate: 250 kbps Assume Tpacket = 1.5 ms 39 bytes / 250 kbps = 1.248 ms Assume Tperiod = 200ms. For channel utilization λ: Tsend = Tpacket / λ Tlisten = 2Tsend Duty-cycle = 2Tsend/Tperiod = 2Tpacket / (λ Tperiod ) = 0.015 / λ For λ = 0.1, duty-cycle = 0.15 λ = 0.2, duty-cycle = 0.075 λ = 0.5, duty-cycle = 0.03Back-up Slides: Back-up SlidesExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Battery Voltage Capacitor VoltageExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Charging Status Duty CycleExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Power Source Status VccExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Vcc Battery VoltageExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Capacitor Voltage Charging StatusExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Power Source Duty CycleExperiment Results (April 6th-9th, 2006) – Four day measurement: Experiment Results (April 6th-9th, 2006) – Four day measurement Battery Voltage VccExperiment Results (April 6th-9th, 2006) – Four day measurement: Experiment Results (April 6th-9th, 2006) – Four day measurement Capacitor Voltage Charging StatusExperiment Results (April 6th-9th, 2006) – Four day measurement: Experiment Results (April 6th-9th, 2006) – Four day measurement Power Source Duty CycleModeling of Energy Consumption – Prometheus Node: Modeling of Energy Consumption – Prometheus Node 1 solar-cell case: 2 solar-cell case: 50% for all the year 20% for all the year 100% for May to Aug. 75% for May to Aug. Parameters: Energy Budget: Pmax= 384mW at (Vp,Ip) = (4.8V,40mA) Energy Consumption: Pactive = 60mW, Psleep = 0.015mW Modeling of Energy Consumption – Heliomote Node: Modeling of Energy Consumption – Heliomote Node 1 solar-cell case: 2 solar-cell case: 20% for all the year 10% for all the year 100% for May to Aug. 50% for May to Aug. Parameters: Energy Budget: Pmax= 270mW at (Vp,Ip) = (3V,90mA) Energy Consumption: Pactive = 54.88mW, Psleep = 6.72mW Experiment Results – Charging through USB port: Experiment Results – Charging through USB port Trend of BatVol of two Trios with USB plugged. BatVol monotonically increases up to 4.1V and saturates around 4.2V.Experiment: Four day measurement – Variation in Solar Radiation: Experiment: Four day measurement – Variation in Solar Radiation High correlation between charging frequency and solar cell short circuit measurement.Previous Work on Duty-Cycling – Naïve duty-cycling: Previous Work on Duty-Cycling – Naïve duty-cycling Used for Prometheus and Heliomote. Power Saving: Periodically turns on for Ton and turns off for Toff. No synchronization among nodes. Pros: Easy to implement, Platform independent. Cons: Doesn’t work for multi-hop network.Previous Work on Duty-Cycling – Dual-channel MAC: PAMAS [SR98]: Previous Work on Duty-Cycling – Dual-channel MAC: PAMAS [SR98] Synchronization of PAMAS: Each node sends and receives RTS/CTS messages over control channel, which is always turned on. Power Saving of PAMAS: Data channel is turned on when activity is expected. Pros: Easy to implement. Cons: Requires dual-channel, control channel still consumes powerPrevious Work on Duty-Cycling – Virtual Clustering (S-MAC, T-MAC): Previous Work on Duty-Cycling – Virtual Clustering (S-MAC, T-MAC) Power Saving of S-MAC: Each node is turned on only for its time slot. Synchronization of S-MAC: Each node sets up its own schedule by (1) Sending its SYNC packet when it hasn’t found neighbor. (2) Following schedule of a neighbor whose schedule is earlier. Channel contention is addressed by RTS/CTS. Pros: Algorithm can be applied to any platform. Cons: Overhead of RTS/CTS, Atmel specific implementation. Previous Work on Duty-Cycling – Low-power listening (B-MAC): Previous Work on Duty-Cycling – Low-power listening (B-MAC) Power Saving for B-MAC: Each node sleeps after listen with no channel activity. Synchronization for B-MAC: Preamble from sender node is long enough to span Tperiod. Pros: No separate synchronization step is needed. Cons: Long preamble is not supported on Trio node.Previous Work on Duty-Cycling – Network-level protocols: Previous Work on Duty-Cycling – Network-level protocols Pros: System-wide energy scheduling. Cons: Tied to a specific network protocol. FPS [HDB04]: Assumes treelike sense-gateway routing. Power Saving: Wakes up only for its time window. Synchronization: Slot is reserved with advertisement and reservation request among parent and child nodes. VigilNet [HKL+05] and LEACH [HCB00]: Form a cluster among nodes. Synchronization: Cluster heads take care of synchronization among nodes. Power Saving: Non-cluster heads are turned off for power saving when they are not sending or receiving.Experiment Setting – Power source check logic: Experiment Setting – Power source check logic If (Vcc < 2.7V and BatVol >= 2.8V) Run on battery. Else if (Vcc < 2.7V and BatVol < 2.7V) Run on capacitor. Else if (Vcc >= 2.7V and CapVol >= 3.0V) Run on capacitor.Experiment Setting – Charging Logic: Experiment Setting – Charging Logic If running on battery CapVol = CapVol - 0.35V. If (BatVol < 4.1V and CapVol < 3.0V ) Stop charging. Else if (BatVol < 4.1V and CapVol >= 3.3V ) Start charging. Else if (BatVol < 4.1V and node is plugged to USB) Start charging. Else if (BatVol >= 4.1V) Stop charging. Adjustment Step USB Charging Condition Overcharging Detection Condition Charging Stop Condition Charging Start ConditionExperiment Results – One day measurement: Experiment Results – One day measurement One day measurement on April 6th, 2006. Use trend data for easier analysis.Experiment: One day measurement – Solar Radiation Hours: Experiment: One day measurement – Solar Radiation Hours Charging was done from 13:00 to 18:00 Running on supercap from 09:00 to 21:00 Mostly running on supercap from 14:00 to 17:00Experiment: One day measurement – Battery Voltage Trend: Experiment: One day measurement – Battery Voltage Trend Initial battery voltage is different among nodes. Due to pre-charging. Either from solar cell charging or USB charging.Experiment: One day measurement – Charging and Battery Voltage: Experiment: One day measurement – Charging and Battery Voltage Node with lower BatVol charges more frequently. Due to overcharging detection condition. Charging threshold Battery voltage and Frequency of charging are reverse order.Experiment Results – Four day measurement: Experiment Results – Four day measurement From 2006/4/6 through 2006/4/9. Experiment: Four day measurement – Verifying the charging logic: Experiment: Four day measurement – Verifying the charging logic Cloudy Rainy Cloudy Variation in CapVol peak hours CapVol and charging hours are highly dependent on solar radiation and weather. Variation in charging hoursExperiment: Experiment Metrics to be measured: Vcc, BatVol, CapVol Power source, Charging and Duty-cycle. Two-mode duty-cycling: Normal duty-cycle (Vcc >= 2.7V): Duty-cycle rate 12.5% (= 8192ms / 65536ms ) Low duty-cycle (Vcc < 2.7V): Duty-cycle rate 1.56% (= 8192ms / 524282ms ) Communication: Single hop btw. each Trio and the base. Sending rate: once every 4 sec with radio on.Estimating energy saving with choice of protocol – S-MAC, B-MAC vs. Always-On: Estimating energy saving with choice of protocol – S-MAC, B-MAC vs. Always-On Used simulation data from B-MAC paper [PHC04]. Simulation with 10 hop multi-hop network. S-MAC for latency of 2 sec: 20% of always-on B-MAC for latency of 2 sec: Around 6% of always-on For latency of 4 sec or longer: Both S-MAC, B-MAC less than 10% of always-onImplementing duty-cycling for Trio – Comparing B-MAC and Seesaw: Implementing duty-cycling for Trio – Comparing B-MAC and Seesaw B-MAC [PHC04]: Seesaw [BSE06]: You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
QualTalk April25 Breezy Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINTLite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 112 Category: Entertainment License: All Rights Reserved Like it (0) Dislike it (0) Added: October 29, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript Designing Self-Sustainable Photovoltaic Sensor Network: Designing Self-Sustainable Photovoltaic Sensor Network Jaein Jeong Qualifying Exam April 25th, 2006Target Environment: Target Environment Outdoor application Wired power and battery has limitations. Solar energy is available, but budget varies. Large-scale, multi-hop networks Multi-hop is needed to cover large WSN. Power saving for multi-hop is not easy. RADIO ON for synchronizing nodes. RADIO OFF for power saving. Power saving for single-hop is trivial.Related Work on Solar Powered Sensor Network: Related Work on Solar Powered Sensor Network Trio [DHJ+06] Real deployment of large sensor nodes. Multi-hop routing. Operate only for several hours with full radio cycle. Other Previous Works RF transmit beacon [ROC+03], Prometheus [JPC05] Heliomote [RKH+05], ZebraNet [ZSLM04]Goals: Goals Power saving for multi-hop networks under solar energy source. Solar Energy: time-varying, low-rate Battery: constant rate, possibly at high rateApproaches: Approaches Modeling energy budget and consumption. Energy budget: Analysis of varying solar radiation. Energy consumption: Estimation based on on-off duty-cycle and power consumption measurement of Trio. Experiments with single-hop & on-off duty-cycle. Proposal of ideas that can achieve low duty-cycling in multi-hop under varying solar energy.Organization: Organization Introduction Modeling of energy budget, consumption (a) Solar energy budget (b) Energy consumption and duty-cycling (c) Charging and energy storage Power saving in multi-hop networks under solar energy Experiment and Discussion Future workOrganization: Organization Introduction Modeling of energy budget, consumption (a) Solar energy budget (b) Energy consumption and duty-cycling (c) Charging and energy storage Power saving in multi-hop networks under solar energy Experiment and Discussion Future workModeling of Energy Budget – Solar Energy Radiation: Modeling of Energy Budget – Solar Energy Radiation Need to model solar energy as variable that can change over time. Solar irradiance is assumed as 100mW/cm2 (= 1kW/m2), but varies on time and location. We can model solar radiation as PSH. For solar cell outputting Psolar at 100mW/cm2, available energy Eavail can be calculated as:Modeling of Energy Budget – Solar Energy Radiation (cont.): Modeling of Energy Budget – Solar Energy Radiation (cont.) Modeling solar radiation at a specific location: Requires meteorological data. We used data from Meteonorm software. Example: PSH for San Francisco, CA Max: 7.35 hours in Jul Min: 1.97 hours in Dec Avg: 4.71 hoursModeling of Energy Budget – Solar Cell Energy Conversion: Modeling of Energy Budget – Solar Cell Energy Conversion Power converted by solar cell is given by: Psolar = Area * Efficiency * Irradiance Estimate Psolar for solar cell used for Trio. Also consider Psolar for previous works.Modeling of Energy Budget – Solar Cell Energy Conversion (cont.): Modeling of Energy Budget – Solar Cell Energy Conversion (cont.) Load Constraint: I-V char. is given: Vp, Ip, Pmax Output voltage ≤ 5.1V due to Zener diode. Space Constraint: Dimension L and W are given. Maximize solar cell output power by connecting multiple solar cells in parallel within the area. 10cm by 10cm Modeling of Energy Budget – Solar Cell Energy Conversion (cont.): Modeling of Energy Budget – Solar Cell Energy Conversion (cont.) Solar cell module output based on published rates with output load and space constraints:Modeling of Energy Consumption – Trio Node: Modeling of Energy Consumption – Trio Node Power consumption for duty-cycle rate R: Pcons = R*Pactive + (1-R)*Psleep Daily energy consumption: Eday = Pcons * 24 hours Trio node power consumption measurement: Radio consumes most power. Reducing radio duty-cycle will reduce power consumption.Modeling of Energy Consumption – Trio Node (cont.): Modeling of Energy Consumption – Trio Node (cont.) 1 solar-cell case: 2 solar-cell case: 25% for all the year 10% for all the year 100% for Apr. to Sep. 50% for Apr. to Sep. Location: San FranciscoCharging to Energy Storage Element: Charging to Energy Storage Element Supercap for primary, lithium-ion for secondary. Reduces battery charging frequency. Software-controlled battery charging. Unlike other batteries, Li+ battery should be charged only when there is sufficient charge in the supercap. Pros: Simple hardware: micro-controller, DC-DC converter, analog switch. Cons: Requires correct software for charging control.Consideration of other types of storage element: Consideration of other types of storage element Battery is needed during overcast days. Supercap-only method doesn’t have sufficient capacity. Comparison of charging efficiency is not available yet.Organization: Organization Introduction Modeling of energy budget, consumption (a) Solar energy budget (b) Energy consumption and duty-cycling (c) Charging and energy storage Power saving in multi-hop networks under solar energy Experiment and Discussion Future workRelated Work on Duty-Cycling: Related Work on Duty-Cycling Protocols with no synchronization: Prometheus, Heliomote Periodic turns on/off, no synchronization. Low power MAC protocols: Dual channel (data + control): PAMAS [SR98] Synchronous: S-MAC [YHE02], T-MAC [vDL03] Asynchronous: B-MAC [PHC04], Seesaw [BSE06] Network level protocols: system-wide energy scheduling. FPS [HDB04], VigilNet [HKL+05], LEACH [HCB00]Limitation of previous low duty-cycle protocols: Limitation of previous low duty-cycle protocols Previous protocols use single duty-cycle rate. Works well for battery. Could drain energy source for time varying source. We need a low duty-cycle protocol that can adjust rate based on solar energy.Interfacing low-power network protocol with energy harvesting: Interfacing low-power network protocol with energy harvesting Energy monitor notifies change in solar radiation. Use CapVol due to high correlation among nodes. Low-power network protocol adjusts the duty-cycle when notified. Low-power network protocol Energy Monitoring Module Change in energy condition Set duty-cycleImplementing Duty-Cycling for Trio: Implementing Duty-Cycling for Trio Needs to address system dependent issues. Use of low level timer is dependent on Atmel μ-controller. Use of long preamble works for CC1000, not for CC2420. Instead of long preamble, a sender can send multiple packets with same interval [Seesaw: BSE06].Duty-Cycling Estimation for Seesaw Implementation: Duty-Cycling Estimation for Seesaw Implementation Facts and assumptions TinyOS packet length: 39 bytes, CC2420 data rate: 250 kbps Tperiod <= 1000 ms due to latency requirement Tpacket >= 39 bytes/250 kbps = 1.248 ms, let Tpacket=1.5ms Estimating performance metric Duty-cycle rate = Tlisten/Tperiod = 2Tsend/Tperiod = 2Tsend/(λTperiod) Date rate = 1 packet / Tperiod Seesaw implementation could achieve 1.5% duty-cycle at λ = 0.2.Organization: Organization Introduction Modeling of energy budget, consumption (a) Solar energy budget (b) Energy consumption and duty-cycling (c) Charging and energy storage Power saving in multi-hop networks under solar energy Experiment and Discussion Future workExperiment: Experiment Measurements: April 6th, 2006 – April 9th, 2006 Metrics to measure: Vcc, BatVol, CapVol Power source, Charging and Duty-cycle. Duty cycling: Naïve duty-cycling, no use of low-power MAC Two mode: normal (12.5%) & low duty-cycle (1.56%) Communication: Single hop btw. each Trio and the base. Sending rate: once every 4 sec with radio on.Experiment Setting – Power source check logic: Experiment Setting – Power source check logic Power source logic Charging logic Run on Cap Run on Bat (3) Low Vcc, High Bat: Vcc < 2.7V and BatVol >= 2.8V (1) Low Vcc, Low Bat: (1) Vcc < 2.7V and BatVol >= 2.8V (2) High Vcc, High Cap: Vcc >= 2.7V and CapVol >= 3.0V Charging No Charging (1) High Radiation: BatVol < 4.1V and CapVol >= 3.3V (2) USB Charging: BatVol < 4.1V and plugged to USB (3) Low Radiation: BatVol < 4.1V CapVol >= 3.0V (3) Overcharging: BatVol >= 4.1VExperiment: One day trend – Verifying the charging logic: Experiment: One day trend – Verifying the charging logic Charging was done from 13:00 to 18:00 Gradual increase in BatVol Average CapVol reached 3.1V during the peak Experiment: One day trend – Balancing Energy Consumption: Experiment: One day trend – Balancing Energy Consumption Trio nodes maintain about the same level for BatVol and CapVol while operating continuously. Experiment: Four day trend – BatVol, CapVol variation with weather: Experiment: Four day trend – BatVol, CapVol variation with weather Battery voltage drops over successive overcast daysSummary of Experiment Results : Summary of Experiment Results Charging logic is correctly working. Naïve duty-cycling with single-hop traffic works sustainably over sunny or cloudy days. Battery level decreases over successive overcast days. Research Timeline: Research Timeline May 2006 to December 2006: Implementation and evaluation of low duty-cycle MAC and network protocol for Trio. Comparative analysis of energy storage design. January 2007 to August 2007: Dissertation work. References: References [BSE06] Rebecca Braynard, Adam Silberstein, and Carla Ellis. Extending network lifetime using an automatically tuned energy-aware mac protocol. IEEE EWSN, Feb. 2006. [DHJ+06] Prabal Dutta, Jonathan Hui, Jaein Jeong, Sukun Kim, Cory Sharp, Jay Taneja, Gilman Tolle, Kamin Whitehouse, and David Culler. Trio: Enabling sustainable and scalable outdoor wireless sensor network deployments. IEEE SPOTS in submission, 2006. [HCB00] Wendi Rabiner Heinzelman, Anatha Chandrakasan, and Hari Balakrishnan. Energy-efficient communication protocols for wireless microsensor networks. Proceedings of the Hawaii International Conference on Systems Science, Jan. 2000. [HDB04] Barbara Hohlt, Lance Doherty, and Eric Brewer. Flexible power scheduling for sensor networks. IEEE IPSN, Apr. 2004. [HKL+05] Tian He, Sudha Krishnamurthy, Liqian Luo, Ting Yan, Lin Gu, Radu Stoleru, Gang Zhou, Qing Cao, Pascal Vicaire, John A. Stankovic, Tarek F. Abdelzaher, Jonathan Hui, and Bruce Krogh. Vigilnet: An integrated sensor network system for energyefficient surveillance. ACM Transactions on Sensor Networks, 2005. [JPC05] Xiaofan Jiang, Joseph Polastre, and David Culler. Perpetual environmentally powered sensor networks. IEEE SPOTS, 2005. [PHC04] Joseph Polastre, Jason Hill, and David Culler. Versatile low power media access for wireless sensor networks. ACM Sensys, Nov. 2004. References – cont.: References – cont. [RSF+04] Shad Roundy and Dan Steingart and Luc Frechette and Paul Wright and Jan Rabaey, Power Sources for Wireless Sensor Networks, IEEE EWSN, 2004. [RKH+05] Vijay Raghunathan, Aman Kansal, Jason Hsu, Jonathan Friedman, and Mani Srivastava. Design considerations for solar energy harvesting wireless embedded systems. IEEE SPOTS, 2005. [Rou03] Shad J. Roundy. Energy scavenging for wireless sensor nodes with a focus on vibration to electricity conversion. Ph.D Thesis, University of California at Berkeley, May 2003. [RU6] The ru6730 photo battery. http://rusolar.com/products.ru6730.html. [RWAM05] Injong Rhee, Ajit Warrier, Mahesh Aia, and Jeongki Min. Zmac: a hybrid mac for wireless sensor networks. ACM Sensys, Nov. 2005. [Sola] Power film - flexible solar panels. http://www.solar-world.com/PowerFilm.htm. [Solb] Solar panels - high efficiency. http://www.solar-world.com/SolarPanels.htm. [SR98] Suresh Singh and C. S. Raghavendra. Pamas - power aware multi-access protocol with signalling for ad hoc networks. ACM SIGCOMM, 1998. [SSC05] F. Simjee, D. Sharma and P. H. Chou, “Everlast: Long-life, Supercapacitor-operated Wireless Sensor Node” [Sun] Panasonic solar cells technical handbook ‘98/99. http://downloads.solarbotics.com/PDF/sunceramcat.pdf. [vDL03] Tijs van Dam and Koen Langendoen. An adaptive energyefficient mac protocol for wireless sensor networks. ACM Sensys, Nov. 2003. [YHE02] Wei Ye, John Heidemann, and Deborah Estrin. An energyefficient mac protocol for wireless sensor networks. IEEE INFOCOM, 2002. Possible Questions: Possible QuestionsPossible Questions: Possible Questions Why do we use solar energy? Solar energy has the highest energy density among energy harvesting methods. Commercially available. [RSF+04]Possible Questions: Possible Questions How about just using batteries? Non-rechargeable lithium batteries have high energy density. Even the high density battery have limited lifetime From Digikey.comPossible Questions: Possible Questions For power saving, duty-cycling is needed. Single-hop case: Sender duty-cycles, but receiver is always on. Synchronized when sender is awake. Multi-hop case: Both sender and receiver duty-cycle radio. Synchronized when both sender and receiver are awake. Possible Questions: Possible Questions Definitions and Units Spectral irradiance (W/m2μm): Power received by a unit surface area in a wave length differential dλ. Irradiance (W/m2): Integral of the spectral irradiance extended to all wavelengths of interest. Radiation (kWh/m2): Time integral of the irradiance over a given period of time.Possible Questions: Possible Questions I-V characteristic varies depending on the solar irradiance. From “Modelling Photovoltaic Systems Using PSpice” by Luis Castaner, Santiago SilvestrePossible Questions: Possible Questions Load Limitation with Zener diode: The reverse voltage across the Zener diode is regulated below VZener as long as the current is limited to a certain level.Possible Questions: Possible Questions Capacity of supercap: Ecap = ½ CVmax2 + ½ CVmax2 = CVmax2 = 22F * (2.5V)2 = 137.5 J = 38.2 mWh Capacitor of battery: Ebat = C * V = 750mAh * 3.5V = 2625 mWh Supercap alone is not sufficient for overcast days: Eday for 10% = 181 mWh Bday: # days a node can operate with no sunlight. Bday = Ebat / EdayPossible Questions: Possible Questions Heliomote Battery Capacity: Ebat = 2 * C * V = 2 * 1800mAh * 1.2V = 4320 mWh Everlast Capacitor Capacity: Ecap = ½ CVmax2 = ½ * 100F * (2.5V)2 = 312.5 J = 86.8 mWh Bday: # days a node can operate with no sunlight. Bday = Ebat / Eday or Ecap / Eday Possible Questions: Possible Questions Possible receiver duty cycle with Seesaw: TinyOS packet length on CC2420: 39 bytes 8 bytes header, 2 bytes footer, 29 bytes data CC2420 data rate: 250 kbps Assume Tpacket = 1.5 ms 39 bytes / 250 kbps = 1.248 ms Assume Tperiod = 200ms. For channel utilization λ: Tsend = Tpacket / λ Tlisten = 2Tsend Duty-cycle = 2Tsend/Tperiod = 2Tpacket / (λ Tperiod ) = 0.015 / λ For λ = 0.1, duty-cycle = 0.15 λ = 0.2, duty-cycle = 0.075 λ = 0.5, duty-cycle = 0.03Back-up Slides: Back-up SlidesExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Battery Voltage Capacitor VoltageExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Charging Status Duty CycleExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Power Source Status VccExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Vcc Battery VoltageExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Capacitor Voltage Charging StatusExperiment Results (April 6th, 2006) – One day measurement: Experiment Results (April 6th, 2006) – One day measurement Power Source Duty CycleExperiment Results (April 6th-9th, 2006) – Four day measurement: Experiment Results (April 6th-9th, 2006) – Four day measurement Battery Voltage VccExperiment Results (April 6th-9th, 2006) – Four day measurement: Experiment Results (April 6th-9th, 2006) – Four day measurement Capacitor Voltage Charging StatusExperiment Results (April 6th-9th, 2006) – Four day measurement: Experiment Results (April 6th-9th, 2006) – Four day measurement Power Source Duty CycleModeling of Energy Consumption – Prometheus Node: Modeling of Energy Consumption – Prometheus Node 1 solar-cell case: 2 solar-cell case: 50% for all the year 20% for all the year 100% for May to Aug. 75% for May to Aug. Parameters: Energy Budget: Pmax= 384mW at (Vp,Ip) = (4.8V,40mA) Energy Consumption: Pactive = 60mW, Psleep = 0.015mW Modeling of Energy Consumption – Heliomote Node: Modeling of Energy Consumption – Heliomote Node 1 solar-cell case: 2 solar-cell case: 20% for all the year 10% for all the year 100% for May to Aug. 50% for May to Aug. Parameters: Energy Budget: Pmax= 270mW at (Vp,Ip) = (3V,90mA) Energy Consumption: Pactive = 54.88mW, Psleep = 6.72mW Experiment Results – Charging through USB port: Experiment Results – Charging through USB port Trend of BatVol of two Trios with USB plugged. BatVol monotonically increases up to 4.1V and saturates around 4.2V.Experiment: Four day measurement – Variation in Solar Radiation: Experiment: Four day measurement – Variation in Solar Radiation High correlation between charging frequency and solar cell short circuit measurement.Previous Work on Duty-Cycling – Naïve duty-cycling: Previous Work on Duty-Cycling – Naïve duty-cycling Used for Prometheus and Heliomote. Power Saving: Periodically turns on for Ton and turns off for Toff. No synchronization among nodes. Pros: Easy to implement, Platform independent. Cons: Doesn’t work for multi-hop network.Previous Work on Duty-Cycling – Dual-channel MAC: PAMAS [SR98]: Previous Work on Duty-Cycling – Dual-channel MAC: PAMAS [SR98] Synchronization of PAMAS: Each node sends and receives RTS/CTS messages over control channel, which is always turned on. Power Saving of PAMAS: Data channel is turned on when activity is expected. Pros: Easy to implement. Cons: Requires dual-channel, control channel still consumes powerPrevious Work on Duty-Cycling – Virtual Clustering (S-MAC, T-MAC): Previous Work on Duty-Cycling – Virtual Clustering (S-MAC, T-MAC) Power Saving of S-MAC: Each node is turned on only for its time slot. Synchronization of S-MAC: Each node sets up its own schedule by (1) Sending its SYNC packet when it hasn’t found neighbor. (2) Following schedule of a neighbor whose schedule is earlier. Channel contention is addressed by RTS/CTS. Pros: Algorithm can be applied to any platform. Cons: Overhead of RTS/CTS, Atmel specific implementation. Previous Work on Duty-Cycling – Low-power listening (B-MAC): Previous Work on Duty-Cycling – Low-power listening (B-MAC) Power Saving for B-MAC: Each node sleeps after listen with no channel activity. Synchronization for B-MAC: Preamble from sender node is long enough to span Tperiod. Pros: No separate synchronization step is needed. Cons: Long preamble is not supported on Trio node.Previous Work on Duty-Cycling – Network-level protocols: Previous Work on Duty-Cycling – Network-level protocols Pros: System-wide energy scheduling. Cons: Tied to a specific network protocol. FPS [HDB04]: Assumes treelike sense-gateway routing. Power Saving: Wakes up only for its time window. Synchronization: Slot is reserved with advertisement and reservation request among parent and child nodes. VigilNet [HKL+05] and LEACH [HCB00]: Form a cluster among nodes. Synchronization: Cluster heads take care of synchronization among nodes. Power Saving: Non-cluster heads are turned off for power saving when they are not sending or receiving.Experiment Setting – Power source check logic: Experiment Setting – Power source check logic If (Vcc < 2.7V and BatVol >= 2.8V) Run on battery. Else if (Vcc < 2.7V and BatVol < 2.7V) Run on capacitor. Else if (Vcc >= 2.7V and CapVol >= 3.0V) Run on capacitor.Experiment Setting – Charging Logic: Experiment Setting – Charging Logic If running on battery CapVol = CapVol - 0.35V. If (BatVol < 4.1V and CapVol < 3.0V ) Stop charging. Else if (BatVol < 4.1V and CapVol >= 3.3V ) Start charging. Else if (BatVol < 4.1V and node is plugged to USB) Start charging. Else if (BatVol >= 4.1V) Stop charging. Adjustment Step USB Charging Condition Overcharging Detection Condition Charging Stop Condition Charging Start ConditionExperiment Results – One day measurement: Experiment Results – One day measurement One day measurement on April 6th, 2006. Use trend data for easier analysis.Experiment: One day measurement – Solar Radiation Hours: Experiment: One day measurement – Solar Radiation Hours Charging was done from 13:00 to 18:00 Running on supercap from 09:00 to 21:00 Mostly running on supercap from 14:00 to 17:00Experiment: One day measurement – Battery Voltage Trend: Experiment: One day measurement – Battery Voltage Trend Initial battery voltage is different among nodes. Due to pre-charging. Either from solar cell charging or USB charging.Experiment: One day measurement – Charging and Battery Voltage: Experiment: One day measurement – Charging and Battery Voltage Node with lower BatVol charges more frequently. Due to overcharging detection condition. Charging threshold Battery voltage and Frequency of charging are reverse order.Experiment Results – Four day measurement: Experiment Results – Four day measurement From 2006/4/6 through 2006/4/9. Experiment: Four day measurement – Verifying the charging logic: Experiment: Four day measurement – Verifying the charging logic Cloudy Rainy Cloudy Variation in CapVol peak hours CapVol and charging hours are highly dependent on solar radiation and weather. Variation in charging hoursExperiment: Experiment Metrics to be measured: Vcc, BatVol, CapVol Power source, Charging and Duty-cycle. Two-mode duty-cycling: Normal duty-cycle (Vcc >= 2.7V): Duty-cycle rate 12.5% (= 8192ms / 65536ms ) Low duty-cycle (Vcc < 2.7V): Duty-cycle rate 1.56% (= 8192ms / 524282ms ) Communication: Single hop btw. each Trio and the base. Sending rate: once every 4 sec with radio on.Estimating energy saving with choice of protocol – S-MAC, B-MAC vs. Always-On: Estimating energy saving with choice of protocol – S-MAC, B-MAC vs. Always-On Used simulation data from B-MAC paper [PHC04]. Simulation with 10 hop multi-hop network. S-MAC for latency of 2 sec: 20% of always-on B-MAC for latency of 2 sec: Around 6% of always-on For latency of 4 sec or longer: Both S-MAC, B-MAC less than 10% of always-onImplementing duty-cycling for Trio – Comparing B-MAC and Seesaw: Implementing duty-cycling for Trio – Comparing B-MAC and Seesaw B-MAC [PHC04]: Seesaw [BSE06]: