EmStar: Software for Wireless Sensor Networks

What is EmStar?

EmStar is a programming model and software framework for creating Linux-based sensor network applications that are self configuring, reactive to dynamics, and can either be interactively debugged or operate without user interaction.

In traditional (e.g., Internet) programming models, problems such as routing, retransmissions after lost packets, or transient failures of nodes and links are hidden from the application. The goal of EmStar is to facilitate a more direct interaction with underlying modules by doing away with strict layering, but in a way that does not sacrifice very much modularity or layers of conceptual abstraction.

The EmStar execution environment makes your code easier to debug. The same code and configuration can be run on real nodes (either using low-power radios such as motes, or 802.11), as a pure simulation, or in a hybrid mode that combines processing done in simulation and communication, sensing, and actuation on real (physical) channels. The same source code can be used in any of these modes without changes. Developers can seamlessly iterate between simulation and reality.

This page has resources that describe what EmStar does and how to use it. We don't yet have formal documentation because the code is still new and in flux. So, for now, the emstar user will have to rely heavily on reading source code of example programs and the framework itself.

Downloads

Current development happens in our CVS Repository. The module name is emstar. Our CVS repository supports anonymous checkout, and has various online source browsing tools, such as ViewCVS and LXR.

Code in CVS is not guaranteed to work. We periodically make stable releases for people who don't want to live on the bleeding edge:

Release	CVS Tag	Release date
EmStar 1.3.2	EMSTAR_RELEASE_1_3_2	February 20, 2004
EmStar 1.3.1	EMSTAR_RELEASE_1_3_1	February 12, 2004
EmStar 1.3	EMSTAR_RELEASE_1_3	February 11, 2004
EmStar 1.2	EMSTAR_RELEASE_1_2	February 4, 2004
EmStar 1.1	EMSTAR_RELEASE_1_1	January 29, 2004
EmStar 1.0	EMSTAR_RELEASE_1_0	November 18, 2003

Mailing Lists: emstar-users and emstar-design

We run a mailing list for questions and discussion about using EmStar, EmStar tools and services, and implementation of new components.

New members can subscribe via the emstar-users mailing list web page.
The mailing list archives may contain the answers to commonly asked questions: emstar-users Archives.

There is also another list intended to host a discussion of design issues and design directions in EmStar. By using this channel, we hope to be able to discuss planned changes to the system in a broader community, and get new design ideas and feedback.

New members can subscribe via the emstar-design mailing list web page.
The mailing list archives are also available at emstar-design Archives.

Finally, for EmStar developers working from our CVS repository, several CVS mailing lists are relevant.

Overview

EmStar White Paper -- CENS Technical Report 009, a good overview of EmStar and its motivation. (Under submission.)
EmStar USENIX Paper -- CENS Technical Report 034. (Under submission.)
Why do we need a new programming model? Written by Lew Girod; not yet complete.
Emstar Overview -- Powerpoint presentation given by Jeremy and Lew in the CENS Systems Meeting, August 2003

Software Documentation

Finding a computer for EmStar development -- Instructions on using the computers managed by CENS, or how to set up your own computer to work with EmStar.
Using the EmStar build system
EmRun: Your one-stop shop for running everything
My First Program: Sending and Receiving Packets with EmStar -- How to run a basic example program ('ping') that sends packets from one computer to another (via UDP in this example).
Using the EmStar Simulator -- Running exactly the same 'ping' example program, but inside the simulator, with a simulated Mote channel, instead of via UDP.
Advanced Simulator Configuration -- Creating simulations that have node-specific or time-varying configurations.
Simulator Channel Models -- Descriptions of the channel models available in the simulator.
EmCee: Running your code on real motes, on the ceiling array -- A cross between reality and simulation. All your code runs centrally, just like in the simulator. But, instead of a simulated channel, your packets go over the real mote channel, via the motes mounted on the lab ceiling.
EmTOS: Debugging TinyOS Code using EmStar -- Compile your NesC code as an EmStar binary, allowing you to use the full EmStar debugging facilities. You can even run NesC programs on our simulator, or on our network of real motes using our ceiling array!
Using and Extending EmView. Powerpoint introduction to EmView, the EmStar visualization engine. EmView is designed to visualize protocol state in a distributed network, whether that network is running on real nodes, on the simulator, or on the ceiling. EmView is easily extensible to add new, application specific visualization features.
An Introduction to the EmStar Event Model
Neighbor Discovery: How to learn who is around
Flooding: Contacting far-away nodes
FUSD: Creating user-space device drivers -- EmStar makes extensive use of FUSD to create user-space devices -- device files that are interfaces to other programs in the system. Beginning users will probably never need to use this API directly, but I had to put a link to it here since it's the only thing that we actually have real documentation for :-).

Publications

L. Girod, J. Elson, A. Cerpa, T. Stathopoulos, N. Ramanathan, D. Estrin, "EmStar: a Software Environment for Developing and Deploying Wireless Sensor Networks", to appear in the Proceeding of USENIX 04, also as CENS Technical Report 34. .ps, .pdf

J. Elson, S. Bien, N. Busek, V. Bychkovskiy, A. Cerpa, D. Ganesan, L. Girod, B. Greenstein, T. Schoellhammer, T. Stathopoulos, and D. Estrin, "EmStar: An Environment for Developing Wireless Embedded Systems Software" .pdf, CENS Technical Report 0009, March 24, 2003.

Last modified 20 February 2004