NDLI: A tale of two synchronizing clocks

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ADB: an efficient multihop broadcast protocol based on asynchronous duty-cycling in wireless sensor networks

VTrack: accurate, energy-aware road traffic delay estimation using mobile phones

TOSThreads: thread-safe and non-invasive preemption in TinyOS

Darjeeling, a feature-rich VM for the resource poor

Low-power clock synchronization using electromagnetic energy radiating from AC power lines

FIND: faulty node detection for wireless sensor networks

YETI: an Eclipse plug-in for TinyOS 2.1

Live photo mosaic with a group of wireless image sensors

RACNet: a high-fidelity data center sensing network

M&M: multi-level Markov model for wireless link simulations

Canopy closure estimates with GreenOrbs: sustainable sensing in the forest

Macrodebugging: global views of distributed program execution

Mercury: a wearable sensor network platform for high-fidelity motion analysis

Optimal clock synchronization in networks

The case for a network protocol isolation layer

ASSERT: Advanced wireleSS Environment Research Testbed

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Explicit and precise rate control for wireless sensor networks

Bursty traffic over bursty links

Experiences with a high-fidelity wireless building energy auditing network

Evaluating a BASIC approach to sensor network node programming

Suelo: human-assisted sensing for exploratory soil monitoring studies

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Achieving range-free localization beyond connectivity

Distributed energy measurements in wireless sensor networks

ANN-based non-linearity compensator of LVDT sensor for structural health monitoring

Generation of controllable radio interference for protocol testing in wireless sensor networks

Teaching wireless sensor networks through testbed development

A wireless sensor network for border surveillance

Run time assurance of application-level requirements in wireless sensor networks

Macrodebugging with MDB

Prototyping a software factory for wireless sensor networks

HONS (hybrid open networking stack) for diverse wireless sensor networks

Wildlife and environmental monitoring using RFID and WSN technology

A service-oriented operating system and an application development infrastructure for wireless sensor networks

Characterization of link asymmetry in wireless sensor networks

A navigation system based on a sensor network without exit and locations

PipeProbe: mapping hidden water pipelines

NISAT: a zero-side-effect testbed for wireless sensor networks

On building mobility models for floating objects

iLight: device-free passive tracking by wireless sensor networks

An efficient operating system abstraction layer for portable applications in the domain of wireless sensor networks

Physicalnet: a middleware for programming concurrent, across administrative domain sensor and actuator networks

Integrated distributed energy awareness for wireless sensor networks

A virtualization framework for heterogeneous sensor network platforms

Learning from sensor network data

An implementation of a wireless sensor network-based meter reading system

Heuristics for scheduling periodic real-time streams in wireless sensor networks

Towards power transformer condition monitoring

Recovering network topology with binary sensors

Measuring foot pronation using RFID sensor networks

A wireless routing protocol in d-dimensional spaces

SensorFly: a controlled-mobile aerial sensor network

Wireless link simulations using multi-level Markov models

TransitGenie: a context-aware, real-time transit navigator

A wireless pedestrian tracking network

Hallway monitoring with sensor networks

Ear-Phone assessment of noise pollution with mobile phones

Whac-A-Bee: a sensor network game

Design of a low-cost sensor node for distributed spectrum sensing

Radio information management for distributed spectrum sensing

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Low-power high-precision timing hardware for sensor networks

A cyber-physical middleware framework for continuous monitoring of water distribution systems

SNORES: towards a less-intrusive home sleep monitoring system using wireless sensor networks

Exploiting the tradeoff between fast wakeup and long standby in event-monitoring WSN

A wake-on sensor network

A stolen object detection and tracing system for mobile valuables

WIA-PA network and its interconnection with legacy process automation system

Energy profiling for mPlatform

Hybrid-powered RFID sensor networks

Energy-efficient management of wireless sensor networks

mCrowd: a platform for mobile crowdsourcing

SensorTrust: a resilient trust model for WSNs

Common Sense: participatory urban sensing using a network of handheld air quality monitors

SolarMote: a low-cost solar energy supplying and monitoring system for wireless sensor networks

An affordable, long-lasting, and autonomous theft detection and tracking system

The FlockLab testbed architecture

A human probe for measuring walkability

Implementation of the low power performance analysis system for WSN

Integrated GPS-denied localization, tracking and automatic personal identification

Application of geosensor nodes in low-rate networks

A tale of two synchronizing clocks

Content Provider	ACM Digital Library
Author	Montestruque, Luis Bagchi, Saurabh Panta, Rajesh K. Koo, Jinkyu
Abstract	A specific application for wastewater monitoring and actuation, called CSOnet, deployed city-wide in a mid-sized US city, South Bend, Indiana, posed some challenges to a time synchronization protocol. The nodes in CSOnet have a low duty cycle (2% in current deployment) and use an external clock, called the Real Time Clock (RTC), for triggering the sleep and the wake-up. The RTC has a very low drift (2 ppm) over the wide range of temperature fluctuations that the CSOnet nodes have, while having a low power consumption (0.66 mW). However, these clocks will still have to be synchronized occasionally during the long lifetime of the CSOnet nodes and this was the problem we confronted with our time synchronization protocol. The RTC to fit within the power and the cost constraints makes the tradeoff of having a coarse time granularity of only 1 second. Therefore, it is not sufficient to synchronize the RTC itself---that would mean a synchronization error of up to 1 second would be possible even with a perfect synchronization protocol. This would be unacceptable for the low duty cycle operation---each node stays awake for only 6 seconds in a 5 minute time window. This was the first of three challenges for time synchronization. The second challenge is that the synchronization has to be extremely fast since ideally the entire network should be synchronized during the 6 second wake-up period. Third, the long range radio used for the metropolitan-scale CSOnet does not make its radio stack software available, as is seen with several other radios for long-range ISM band RF communication. Therefore, a common technique for time synchronization---MAC layer time-stamping---cannot be used. Additionally, MAC layer time-stamping is known to be problematic with high speed radios (even at 250 kbps). We solve these challenges and design a synchronization protocol called Harmonia. It has three design innovations. First, it uses the finely granular microcontroller clock to achieve synchronization of the RTC, such that the synchronization error, despite the coarse granularity of the RTC, is in the microsecond range. Second, Harmonia pipelines the synchronization messages through the network resulting in fast synchronization of the entire network. Third, Harmonia provides failure handling for transient node and link failures such that the network is not overburdened with synchronization messages and the recovery is done locally. We evaluate Harmonia on CSOnet nodes and compare the two metrics of synchronization error and synchronization speed with FTSP. It performs slightly worse in the former and significantly better in the latter.
Starting Page	239
Ending Page	252
Page Count	14
File Format	PDF
ISBN	9781605585192
DOI	10.1145/1644038.1644062
Language	English
Publisher	Association for Computing Machinery (ACM)
Publisher Date	2009-11-04
Publisher Place	New York
Access Restriction	Subscribed
Subject Keyword	Low duty cycle Synchronization Sensor
Content Type	Text
Resource Type	Article

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