Disruption-Tolerant Link-level Mechanisms for Extreme Wireless Network Environments

Abstract

Wireless links pose significant challenges in terms of achievable goodput and residual loss-rate. Our recent enhancements, called LT-TCP make TCP loss-tolerant in heavy/bursty erasure environments. Link-level protocols mitigate these problems by using a combination of FEC and ARQ but are insufficient when the channel experiences disruptions. When the underlying source of loss is interference (e.g., 802.11 environments), MAC-level mechanisms misinterpret interference as noise leading to poor scheduling (e.g., capture effects) and limit the benefit of transport layer mitigation efforts. We propose enhancements to link-level protocols that enable survival during disruptions. We explore an adaptive link-level strategy to export a small residual loss rate and bounded latency under high loss/ disruption conditions. We evaluate the proposed link-level enhancements, showing that the combination with LT-TCP helps achieve significant end-to-end performance gains. We also demonstrate the trade-off between reduced link layer residual loss (by increasing ARQ persistence) and transport layer timeouts.