A Software-Defined Retransmission Mechanism to Manage Real-Time Traffic in Wi-Fi Networks

In several application contexts, keeping transmission latencies on a wireless network bounded is required. When high bandwidth is additionally demanded, IEEE 802.11 is certainly a reasonable choice. Reliable data delivery is customarily achieved through automatic retransmission upon errors. In Wi-Fi, retries are managed in hardware by adapters. Unfortunately, this constrains the possible sequences with which messages are sent on air, which increases latency and worsens communication determinism. Previous works showed that such limitations can be overcome by having frames retransmissions managed in software by conventional user-space applications. To do so, slight modifications are needed to device drivers to provide the required functions. In this paper, a comprehensive performance analysis of software retransmission mechanisms is performed, which highlights that the related overhead is negligible when compared with the provided advantages and confirms that finely scheduling real-time traffic over Wi-Fi is actually possible. A pilot implementation showed that tangible improvements can be obtained by using a scheduling policy with packet granularity.