Experiments with a Queuing Mechanism over Ever-Changing Data Rates in a VHF Network

In this paper, we discuss experimental results testing a hierarchy of queues controlling the user data-flow over a VHF network with ever-changing data rates (up to 9.6 kbps). We challenged our solution creating three patterns of ever-changing data rates using a stochastic model to include the element of chance (randomness) that can be reproduced for quantitative comparisons. We discuss numbers showing that our queuing mechanism adapts its behavior (i.e. shaping the user data-flow) to the network conditions using feedback from the radio buffer (reactive) and from the routing protocol (proactive). Thus, our hybrid solution monitors the radio buffer occupancy to pause the transmission when a threshold is crossed, and proactively adds an inter-packet interval (IPI). The IPI varies as a function of the link data rate (computed by a tactical router), current network usage, packet loss and latency. The experimental results show three queues (for messages, IP packets and the radio buffer) complementing each other to handle different network conditions while transmitting a message that surely overflows the radio buffer (four times the buffer size).