A middleware for reliable soft real-time communication over IEEE 802.11 WLANs

This paper describes a middleware layer for soft real-time communication in wireless networks devised and realized using standard WLAN hardware and software. The proposed middleware relies on a simple network architecture comprising a number of stations that generate real-time traffic and a particular station, called Scheduler, that coordinates the transmission of the real-time packets using a polling mechanism. The middleware combines EDF scheduling with a dynamic adjustment of the maximum number of transmission attempts, so as to adapt the performance to fluctuations of the link quality, thus increasing the communication reliability, while taking deadlines into account. After describing the basic communication paradigm and the underlying concepts of the proposed middleware, the paper describes the target network configuration and the software architecture. Finally, the paper assesses the effectiveness of the proposed middleware in terms of PER, On-Time Throughput, and Deadline Miss Rate, presenting the results of measurements performed on real testbeds.