Real-time voice streaming over IEEE 802.15.4

Audio and video applications over wireless sensor networks have recently emerged as a promising research field. However, the limits in terms of communication bandwidth and transmission power have withstood the design of low-power embedded nodes for voice communication. In this work we describe the implementation details of an embedded system for the wireless broadcasting of audio signals over the low datarate IEEE 802.15.4 standard, which is widely adopted to build Wireless Personal and Sensor Networks. The resulting device has been developed from scratch by combining several techniques with the goal of obtaining the most suitable implementation on a low-cost and low-power 16-bit microcontroller. We used a realtime operating system, a well-known psychoacoustic model based on FFT signal decomposition and the Haar wavelet transform to create a novel audio compression algorithm targeted to embedded systems with limited computational capabilities. The result is a fully-functional embedded system which is able to stream voice in real-time over IEEE 802.15.4 with an acceptable audio quality.