One deficiency of the first-generation ADCR was the limited bandwidth offered by the onboard 802.11b radios. The effort to develop the second-generation systems, conducted during FY07-08 and also supported by the JGRE, produced an improved prototype system. The Deployer Module was smaller, taking only one-third of the PackBot payload bay. This was made possible by the much thinner relay nodes, which also made self-righting unnecessary. Instead, an accelerometer in the relay node detected which of the two faces the brick had landed on. A microcontroller then raised the dual-diversity antennas appropriately. Unlike the first-generation, this new antenna design could ensure that the deployed antennas were always vertical regardless of the ground slope (assuming that the robot was going up or down a hill and not sideways on its slope when it deployed the relay node—the antennas only had one degree of rotational freedom).
For higher bandwidth, the new radios used hardware developed by Rajant (funded separately by the National Center for Defense Robotics) to support an 802.11g radio card and the BBN Technologies ad hoc networking software. Figure 3 shows the second-generation ADCR system.
Figure 3. A second-generation ADCR Deployer Module on a PackBot and a deployed relay node.