The Project 25 standard allows for both voice and data communications on digital radios. However, commercial manufacturers have implemented the data communications portion of the standard using very expensive equipment. While large agencies may have the resources to purchase and maintain this equipment, small agencies, such as e.g. a town police department with a few cruisers, just cannot afford to do so. Project54 has set out to create a low cost Project 25 data-capable base station that will allow small agencies with limited resources to implement data communications between headquarters and mobile units.

This picture below shows a laboratory demonstration of our Project 25 data-capable base station. On the left is a laptop connected to a Project 25 digital radio. On the right is a PC connected to an analog radio. We have created PC software that sends and receives Project 25 waveforms via the analog radio. The waveforms are received and sent via the PC’s sound card. Our software implements a digital signal processing algorithm that can decode Project 25 waveforms received by the analog radio. The software can also encode information as Project 25 waveforms.

In the video below you can see a demonstration of the Project 25 base station. In the demo the laptop, which runs the widely-deployed Project54 software, initiates a database query by sending out data packets over the Project 25 digital radio. The packets are received by the analog radio. Instead of connecting the analog radio to speakers, we connect its audio output to the PC’s sound card. The DSP software we’ve created then reads the packets (that is the Project 25 waveforms that encode the packets), and extracts the query. The query is sent to a server (in this demo the server resides on the same PC). The server response is encoded as a Project 25 waveform and this waveform is sent to the audio input of the analog radio, via the sound card. The analog radio transmits the Project 25 waveform, which is received by the Project 25 digital radio. Finally, the Project54 software receives the response to the query from the digital radio and provides an output to the user. 

Ivan Elhart

Subscribe to the comments through RSS Feed