Wireless Sensor Networks in the control loop: Delay-sensitive networks

Traditional short-range wireless network standards, such as IEEE 802.11 and IEEE 802.15.4, do not consider packets according to their delay deadlines and they treat the packets all the same regardless of these requirements. In this document, we propose a cross-layer architecture where the application using the wireless medium associates each packet it is pushing down the communication stack with a delay requirement. We propose two new mechanisms: ER (Early Retirement) and PHY+. These mechanisms utilize the deadline associated with each packet for further transmission and redundancy optimization. In our simulations, we focus on the Wireless Sensor Networks domain and apply our methods as an extension to the well-known and widely acceptable low-power, low-throughput IEEE 802.15.4 standard. Simulations performed showed that our mechanisms outperform the original standard considerably, especially in situations where high numbers of users exist in the system.