Another Look at the Duke Wireless Classroom (1998)

During the spring semesters of 1994 and 1995, freshmen at Duke University participated in the first full-scale test of diffuse Infrared OR) networking to link notebook computers in the classroom. Preliminary results were reported in the October '95 issue of T.H.E. Journal and elsewhere.[1-9] Three years have passed since the experiment was discontinued because notebook computers did not become standard issue for students at Duke. This article will take another look at that experiment and, in particular, examine the actual and potential impact of diffuse IR technology. In the Duke Wireless Classroom, as the experiment was called, between 30 and 40 students brought notebook computers (Apple PowerBooks) twice a week into a lecture hall, where a wireless diffuse IR network was established using a newly developed device called the Cooperative. The teacher's notebook computer was projected in front of the class, and Timbuktu screen,sharing software allowed the teacher to project the screen of any student's computer and to control any student's keyboard and trackball (or mouse). The teacher could, in effect, lean over the shoulder of any student with the rest of the class watching. Conversely, students could take turns operating the teacher's computer to work on a single project. Since a wireless network was used, no physical alteration to the classroom was required. What is Diffuse IR? Desktop computers and workstations routinely are connected to networks using copper wire or fiber optics. With portable computers, local wireless communications offers the ability to (1) move around within larger public space such as a library or laboratory, and (2) create local networks for stationary Students without installing wires to every seat in the classroom. Two modes of wireless communication are available: radio and infrared. Radio provides greater range, but is limited in the number of channels of high bandwidth information, specifically because greater range leads to interference between local networks. Among the choices for infrared, direct line-of-sight IR claims the vast majority of present day applications, but requires that each transmitter and receiver pair be aimed at each other across a non-obstructed path. Therefore, line-of-sight IR is inherently limited to a single pair of computers, a computer and a printer, or a computer and an access point to a hard-wired network. The other choke for infrared is diffuse IR, which we used in the Duke Wireless Classroom. Since its commercial introduction in 1994, diffuse IR has received little attention, in spite of its advantages. Diffuse IR systems have greater sensitivity, requiring only that the transmitter and receivers be pointed at the same area of the ceiling. Thus a diffuse IR network can contain many transceiver nodes, just as hard-wired or radio networks do. Unlike radio devices, however, there is no problem with interference from other networks in neighboring rooms. The Photonics device was the first commercially available embodiment of diffuse IR technology. This device, about the size of a computer mouse, plugs into the back of a PowerBook, from which it derives power. Unlike line-of-sight systems, the receiver is sensitive enough to capture reflections from ceilings and walls. We connected a large number (up to 41 at a time) of transceivers simply by pointing them at the same general area of the ceiling in our lecture hall. The speed of our IR network was 230 kitobits per second. A similar IR device for a PC runs at approximately 1 megabit per second. These speeds are roughly 10-40 times slower than typical Ethernet, which operates at 10 Mbps. Nonetheless, diffuse IR is fast enough to support certain important in-classroom functions, such as screen sharing and remote control between the teacher and a single student. The network proved to be very reliable and easy to establish. Information Channels The primary goal of the experiment was to enhance the existing communication within the classroom. …