Abstract
Densely distributed wireless real-time system must perform communication scheduling and protocols in addition to task scheduling to achieve schedulability and reliable communication. While many wireless sensor networks are densely distributed, they assume low duty cycling and trivial data packet rates, and they cannot handle many real-world applications. To highlight these design issues, this paper presents a case study with EcoDAQ, a wireless data acquisition system with 50 sensor nodes streaming real-time data over the same frequency channel. To achieve reliable communication, we define a pulling protocol that minimizes node complexity while guaranteeing collision freedom on a given frequency channel. Our case study illustrates the impact of communication requirements on the rest of the systems including bus and processing speeds. Experimental results show that our monitoring station can sustain gathering accelerometer data from up to 50 nodes in one square meter area at up to 15,000 samples per second with minimal latency and show very high expandability, flexibility and reliability. © 2008 IEEE.