Atarraya is a simulation tool for teaching and researching topology control algorithms and protocols for wireless sensor networks. This project was initiated as part of our research work in this area and included as part of our book "Topology Control in Wireless Sensor Networks" published by Springer in 2009. 

The main idea of Atarraya is to provide a simple tool for creating and testing old and new topology control protocols. Following the book's new definition of topology control, Atarraya includes both topology construction and topology maintenance protocols and algorithms. The inclusion of topology maintenance is a unique aspect of Atarraya. Atarraya's modularity makes it very easy to create new protocols.

Atarraya can also be used in the classroom for teaching purposes. Atarraya's graphical user interface  makes it easy to illustrate how these protocols work. 

In the current version, Atarraya provides the following features:

• Several topology construction and several topology maintenance algorithms and protocols
• Deployment generation using different distributions
• Simulation agent for initial topology construction based on an available algorithm (the user can create and add its own)
• Message generator that can be used to test endurance of the network after the TC algorithm was applied
• Simulation results can be stored in a csv file that can be open in many math analysis software. Also, simulations in batch can be executed
• Implementation of a version of the KNEIGH topology construction protocol as an example of Tx-based TC protocols
• Support for simple mobility models, and the implementation of a random walk-based mobility model
• Support for different energy models

Atarraya is an event-driven simulator. Basically, everything that happens on the simulation is an event. Who generate these events? The simulator, the nodes, etc. The figure below show the general structure of Atarraya.

The basic structure for a simulator is a priority queue of events that are executed based on their time of occurrence. All events are guaranteed to execute in order. There are several actors in this simulator that allow the execution:

• The agent is in charge of taking events from the queue and sending them to the Event Handler. The agent is always running until the simulation finishes. Also, it updates the simulation clock.
• The Event Handler is in charge of executing the proper actions depending on the type of event received. The possible actions that this element can do are: modify the data from nodes in the deployment, generate new events and add them to the queue, etc.
• The data bank will store the latest information of the deployment, and will be consulted by most of the elements in order to have accurate information about the nodes.