Toss-It provides intuitive information transfer techniques for mobile devices, by fully utilizing their mobility. With Toss-It, a user can send information from the user's PDA to other electronic devices with a “toss” or “swing” action, as the user would toss a ball or deals cards to others.

In recent years, mobile devices have rapidly penetrated into our daily lives. Several drawbacks of mobile devices have been mentioned so far, such as their limited computational capability, small screen real estate, and, so on, as compared with notebook or desktop computers. However, by fully utilizing the most notable feature of mobile devices, that is, mobility, we can explore possibilities for a new user interface of the devices. In this project, we use PDAs and propose intuitive information transfer techniques for them, which could not be achieved with notebook or desktop computers. By using the developed system called Toss-It, a user can send information from the user's PDA to other electronic devices with a “toss” or “swing” action, as the user would toss a ball or deals cards to others. Followings are examples of how Toss-It can be used:

• Pass a file from a user's PDA to another user's PDA with just a “toss” action toward him, or pass a file to another user's PDA beyond other users in-between with a stronger “toss” action as shown in Figure 1(a) (unicast transfer).
• Print out an image from a user's PDA through a printer with just a “toss” action toward the printer (Figure 1(b)) or project a slide onto a screen through a projector with just a “toss” action toward the screen.
• Pass a file from a user's PDA to multiple users with just a “(horizontal) swing” action toward them as shown in Figure 1(c). (multicast transfer).

Fig 2. A circuit board with inertial sensors attached to a PDA

In order to recognize a “toss” or “swing” action, we have developed a circuit board that mounts accelerometers, gyroscopes and a microprocessor. The circuit board is designed to be attached to a PDA. In the circuit board shown in Fig. 1, four 2-axis accelerometers and three 1-axis gyroscopes are embedded. They are connected to a PDA through a serial communication via a microprocessor.

Fig. 3 A typical example of the output data of an accelerometer
when a user conducted a “toss” action with Toss-It

We also devised an algorithm for reconizing “toss” and “swing” actions. In order to identify devices that receive information by a user's “toss” or “swing” action, Toss-It is required to recognize not only the action, but also the strength of the “toss” action in a unicast situation (as shown in Fig. 1(a)), and the trajectory of the “swing” action in a multicast situation (as shown in Fig. 1(c)).

Ideally, Toss-It can recognize a “toss” or “swing” action through the output data of the inertial sensors. Several informal experiments, however, have indicated that not-negligible fluctuation occurs in the output data just after the action has been completed. Fig. 3 shows a typical example of the output data of an accelerometer when a user conducted a “toss” action with Toss-It. Our recognition algorithm can remove this not-negligible fluctuation and Toss-It recognizes that a user's action happened between the highlighted region in Figure 3.

Fig. 4 A marker with infrared LEDs for location recognition

There are several existing location recognition technologies applicable to Toss-It. We are now developing a novel location and orientation recognition technology that can acquire relative positions and orientations of multiple devices without any external equipment, such as beacons in the ceiling.. In the current implementation, however, we use a camera-based technology.

A marker with infrared (IR) LEDs (Fig. 4) and a stereo camera are used for the position and orientation recognition of a user's PDA. The IR LEDs on a circuit board are arranged to form an isosceles triangle ( A , B , and C in Fig. 4). The position and orientation of a user's PDA are determined by the shape of the triangle captured through the stereo camera fixed to a ceiling. Different blinking patterns of LEDs (the LED in A is blinking actually) are assigned to individual PDAs for their identification.

Fig. 5 User1 “tosses” a photo to user3 beyond user2

There are various user scenarios that Toss-It makes possible. Fig. 5 shows that user1 “tosses” a photo file in his PDA to user3 beyond user2. All user1 has to do is to select the photo file and conduct a “toss” action. In Toss-It, users do not have to conduct bothersome manipulations on mobile devices, nor do users have to move close to a receiver of information. You can see other user scenarios in the video (download it below!) .