Sensor networking toward real time acoustical beamforming

Wireless sensor networks have been attracting increasing research interest given the recent advances in microelectronics, array processing, and wireless networking. Consisting of a large collection of small, wireless, low-cost, integrated sensing, computing, and communicating nodes capable of performing various demanding collaborative space-time processing tasks, wireless sensor network technology poses various unique design challenges. In this paper, we consider the use of Compaq iPAQ 3760s, which are handheld, battery-powered device normally meant to be used as personal organizers (PDAs), as sensor nodes. The iPAQ provide a reasonable balance of cost, availability, and functionality. It has a build-in StrongARM processor, microphone, codec for acoustic acquisition and processing, and a PCMCIA bus for external IEEE802.11b wireless cards for radio communication. The iPAQs form a distributed sensor network to perform a real-time acoustical beamforming. A beamforming algorithm, based on the maximum-likelihood parameter estimation method, can be used to perform real-time source detection, enhancement, localization, and direction-of-arrival estimation. Field-measured results show the effectiveness of the proposed testbed.