• Design and Development of a Digital Signal Processing System that Responds Automatically to an Audio Trigger Event

      Borah, Deva K.; Chavez, Rudy; Favela, Frank; Ontiveros, Adrian; Smith, Matthew; Wallace, Matthew; New Mexico State University (International Foundation for Telemetering, 2013-10)
      This paper presents the development of a signal processing system that responds automatically to an audio trigger event. The audio trigger event, for example, can be a gun shot, and the system's response is to fire back at the source. The proposed system uses microcontrollers to digitally process audio signals coming from the audio trigger. Once the event is detected, the location of that source relative to the base location is estimated and retaliatory measures are automatically activated by the system. In our study, gunshot sounds are replaced by recorded audio tones and the retaliatory mechanism consists of a Nerf dart being fired toward the sound source. Sound localization is achieved via time stamping the digitized microphone signals. With an array of microphones, angular components as well as radial components can be determined. Servo motors are used to control the turret type mechanism for firing back Nerf darts to the source. The project has potentials for both lethal and non-lethal responses to a firearm discharge. The work is based on a 2013 senior undergraduate capstone project.
    • Pulse Position Modulation using BICM-ID for FSO Channels

      Borah, Deva K.; Kumar, Kuldeep; New Mexico State University (International Foundation for Telemetering, 2013-10)
      We investigate pulse position modulation (PPM) and multipulse PPM (MPPM) for free space op- tical channels using bit interleaved coded modulation with iterative decoding. Data bits are first encoded by using a non recursive convolutional code and the coded bits after an interleaver are modulated before transmission. Iterative decoding is performed at the receiver. Optimized mapping is designed for MPPM. A genetic algorithm is used to find the optimized mapping for MPPM. Our simulation results show that a significant improvement in the error performance can be achieved by using optimized mapping and iterative decoding at the receiver.
    • Relay Selection for Multiple Source Communications and Localization

      Borah, Deva K.; Perez-Ramirez, Javier; New Mexico State University (International Foundation for Telemetering, 2013-10)
      Relay selection for optimal communication as well as multiple source localization is studied. We consider the use of dual-role nodes that can work both as relays and also as anchors. The dual-role nodes and multiple sources are placed at fixed locations in a two-dimensional space. Each dual-role node estimates its distance to all the sources within its radius of action. Dual-role selection is then obtained considering all the measured distances and the total SNR of all sources-to-destination channels for optimal communication and multiple source localization. Bit error rate performance as well as mean squared error of the proposed optimal dual-role node selection scheme are presented.