This scenario (workshop) is a fun way for school age students to learn about the methods of data transmission. In addition to introducing the fundamentals of a communication system, the sub-goal of the scenario is to introduce Hedy Lamarr, an Austrian-born American film actress and inventor who developed a radio guidance system for Allied torpedoes that used spread spectrum and frequency hopping technology to defeat the threat of jamming by the Axis powers. Her significant role in the wold war II, encouraged us to illustrate her idea in data transmission in this workshop, via a simulator system.
The curriculum included in this document is suitable for a two hour workshop with grades 6-7 participants. The curriculum can easily be modified for longer or shorter workshop and can be adapted for younger or older participants as well.
The workshop starts with a presentation for the participants. Based on the grade and age of the students, the presentation may or may not include a short introduction to the World War II and some of those women who have a specific role in this war or their life style have been affected by it. In the main part of the presentation the concept of the spread spectrum in data transmission, which for the first time was proposed by Hedy Lamar, is explained. The rules of a game, designed based on the Hedy Lamarr’s method is clarified for the participants. This presentation can be modified depending on the length of the workshop and the age of the participants.
Figure 2 shows the simulator system, named Toreh, which has been designed to illustrate the concept of the spread spectrum.
In order to better understand how the scenario works, consider four students: Titus, Miles, Victor, and Kevin.
Titus, Miles from group A and Victor and Kevin from group B are ready to play the scenario. Titus and Miles play roles of transmitter and receiver respectively. Victor and Kevin have the role of noise. Titus and Miles receive a codebook which contains the codes of English letters (Table 1).
Titus is privately shown a message (e.g. HAPPINESS CANNOT BE FOUND). For each letter of the message, he finds its associated code from the codebook.
Figure 3 shows the position of each student and their actions at Toreh.
To send each bit of the code, Titus randomly chooses one of the 6 channels of Toreh and drops a blue ball for bit 1 or red ball for bit 0. For example if he wants to send the first letter (H), he finds its code from the codebook (00111-See table 1.). As shown in figure 3, for the first bit, he has chosen channel 2. Independent of him and at the same time, Victor randomly blocks one of the channels by pushing one of the red keys. As shown in figure 3 for the first bit, he has blocked channel 4. Since he has blocked 4 rather than 3, Titus succeeds to send the first bit correctly. It means the blue ball goes to the down left corner of the Balls steep road. In this situation there is no chance for Kevin to have any action.
If Titus and Victor simultaneously had chosen a same channel, then Titus would have failed to send the first bit and the blue ball would have been pushed back to the Blocked Balls Box. In this case Kevin would have randomly dropped a blue or red ball in the Balls Steep Road Panel. Same procedure is down for the second bit, the third bit, etc. It continues for all letters and their related codes.
Figure 4 shows the situation after sending 30 bits correctly. Each bit has reached properly to its destination, because Titus and Vector have chosen different channels or Kevin has dropped the same balls as Titus in the balls’ steep road panel. Hence, Titus has succeeded to send H A P P I N to Miles.). For the 31st bit which is 0, (Note that the code of E is 00100.), Titus drops a red ball in channel 5. However, Victor has blocked this channel (See figure 5.). Hence the ball is pushed back to Blocked Balls Box. Simultaneously Kevin drops a blue ball in Balls Steep Road Panel. Hence a bit error occurs.
Meanwhile, Miles who looks at the panel tries to decode and figure out the message. He needs to process the detected text to correct the errors. Once he detects the message, the game restarts by substituting the positions of group A and B. At this time Victor should send the message IF YOU SEEK IT FOR YOURSELF.
In the simplest form Toreh may be used even for kindergarten students. On a board we have some pictures and their related codes. A student uses these codes to send a message to his/her friends. For example as shown in figure 5, Rose has sent the message MOTHER has bought FLOWERS and ICE CREAM from MARKET. Note that for kindergarten students only one channel (channel 1) is used and all other channels and the channel blocking system are frozen.
