AN ULTRA-LOW-POWERVAD HARDWAREIMPLEMENTATION FOR INTELLIGENT UBIQUITOUS SENSORNETWORKS

We propose a power management method using a digital voice activity detection (VAD) module for intelligent ubiquitous sensor systems. When this VAD module detects a speech signal, a main signal processing circuit is connected to a power source. When no speech signal is detected, most circuits except VAD are blocked off, thereby reducing stand-by power for the specialized sensor nodes used for speech signal processing. We implemented the VAD algorithm , using zero crossing of input signals to an FPGA, thereby achieving 2.10 mW operation. We synthesized this VAD module using CMOS 0.18-llm process, achieving 3.49 IlW power consumption for operation at 1.8 V and 100 kHz. some microphones must not only process signal recording but also noise reduction, sound-source separation, speech recognition, speaker identification , and other tasks [2-6]. As described herein, for the intelligent ubiquitous sensor system described above , we implement a voice activity detector (VAD) to reduce the power consumption of each sensor node. The rest of this paper is organized as follows. The next section presents a description of the intelligent ubiquitous sensor system. Section 3 introduces VAD algorithms. Section 4 describes the system implementation and experiment results. Section 5 explains subjects of future work. Finally, section 6 summarizes the paper.