The Eight International Conference on Information Processing in Sensor Networks (IPSN '09) IPSN '09 will be hosting the Extreme Sensing competition April 13, 2009. Each team will need to build a sensor system using 7 sensors or less that can perform dead reckoning as people walk along predefined paths through a 10m x 10m arena. Each team can use up to 5 body sensors and at most 2 sensors placed in the arena.  In Phase 1, all teams will track conference attendees, estimating their final position relative to a known starting position.  Results will be broadcast live during Phase 1, providing each team an opportunity to discern how the other teams' systems work and how they might fail. In Phase 2, this information can be used to prevent the other teams from scoring more points, as each team gets one chance to walk through the arena themselves while suited up with their opponents' sensors.  

Rules of Play

Each team must build a sensing system that can perform dead reckoning as people walk through a 10m x 10m arena, which will be located in the poster/demo session of the conference. The goal is to estimate the final position of the person given the initial position. Teams can use up to 5 body sensors, which may include accelerometers, gyroscopes, magnetometers, etc. Each team can also setup at most 2 sensors in or around the arena, but predefined paths must remain unobstructed for people to walk, as shown in the diagram below.  The predefined paths will not be revealed until the day of the competition, and will be marked with tape. Examples of sensors placed in the arena might include passive infrared motion sensors, active infrared break beams, ultrasound, dopplar radar, weights sensors, etc. These sensors can be useful for on-line calibration of the body sensors.  The sensor systems have three restrictions: 1) no system may have data cables more than 12 inches in length* 2) no system may impede the motion of the person being sensed, and 3) no system may use more than 7 pixels in total, eg. no cameras with more than 7 pixels, and no more than 7 single-pixel** sensors. Signal emitters will be permitted, as long as they do not interfere with other teams' sensors and as long as they do not help the system emulate more than seven pixels (see below**). Each time a person walks a path with a team's sensors, that team will be required to update a server with its current position estimate at least once per second.  The path estimate will be visualized and projected onto a wall.

During Phase 1, between 5-10 volunteers from among the conference attendees will walk along predefined paths in the arena, while being tracked by the various teams.  Each volunteer will walk the same path for all teams, and can wear body sensors from multiple teams simultaneously, if possible.  The volunteer must walk along the path, with each foot landing on the path in front of the other foot, like tight-rope walking -- i.e. the volunteer cannot veer from the path and cannot walk backwards.  Aside from these restrictions, however, the volunteer can move the body in any way that he/she chooses.  The teams must be able to outfit each volunteer with sensors in 1 minute or less, and must put a sign on the volunteer to indicate that he/she is wearing that team's sensors.  Ground truth will be obtained by entering the path number and a set of team numbers into a computer before the volunteer walks the path.  During Phase 1, contestants will not be allowed to enter the arena.

In Phase 2, each team will be given one chance for a team member to walk a path with every team's body sensors. The goal of each team is to score points for themselves without scoring points for competing teams.  The team can choose any of the predefined paths, but must obey the same rules applied to the volunteers in Phase 1.  The team member must wear all teams' sensors simultaneously, to the extent possible.  If the different teams' sensors cannot be worn simultaneously, all team members must still walk the same path for all teams. 

When walking a path in Phase 2, you will be wearing body sensors from multiple teams, and is unlikely to be able to fool all of them.  Instead, you will need to choose your walking strategies carefully to fool the teams that are most likely to beat you, given the scores after Phase 1. The position estimates from each team will be shown live on a wall projection during Phase 1, as shown in the Figure to the right. This is an opportunity for each team to discern how the other systems work, and how they might fail. For example, radar and PIR sensors may not detect slow moving objects; accelerometers may be fooled by shaking or jumping, gyroscopes may be fooled by bending sideways, and so on. This knowledge can then be used during Phase 2 to score points for your own team but not for the other teams. No competitive strategies are off-limits, except that all players must walk monotonically forward along the predefined path. This means that running or jumping to fool body sensors or spraying baby powder to illuminate laser beams are all acceptable. Be sure to focus on avoiding the sensors of the team whose score is closest to yours.

On Game Day, each system must automatically (ie. no human intervention) report scores to a scoring server at least once per minute when it is in use. This can be done through the following XML-RPC function: