encoding & timing
Each message consists of 13 dibits transmitted over 1300ms. The four dibits (00, 01, 10, 11) correspond with frequencies of 1000Hz, 1250Hz, 1667Hz, and 2500Hz respectively. Each team communicates at 10 baud (dibits/s), resulting in a total bit rate of 20 bits/s, as depicted by the pseudo-sample clock shown in Figure 1.
framing & media access control
Table 1 contains a frame diagram of how the data shall be sent. For more information on how each activity is translated to a 13-dibit packet, please view the full Communications Protocol.
In order to give all stations a chance to transmit without collision, the protocol defines the use of a time-division multiple access (TDMA) protocol to allow all teams a fair chance to transmit what they need without collision. Table 2 shows the time slots for the TDMA frame. Each station will have 2 seconds to send 1 packet of data, but afterwards will need to relinquish the line for the next user. Recall that each packet is 1.3 seconds long, not including the time for raising and lowering the servo to manage push-to-talk over Mumble.