TIBD Phase III: V-NAD scheduler performance and parameter optimization using Taguchi robust design methodology

A key requirement of the US Army´s Tactical Internet Division and Below (TIDB) network is that the network provide robust performance over a wide range of voice and data traffic loads in fully connected as well as fragmented net topologies. The Internet controller (INC), the tactical router for TIDB, is governed by the MIL-STD-188-220B protocol. This protocol specifies a number of interrelated link layer and radio parameters that have significant cross-correlation. As a result the Taguchi robust design technique, which permits optimization of several central factors concurrently, is particularly well suited for the problem of optimizing network performance for a given scenario. The most critical control factors hate been shown to be parameters related to the net access delay (V-NAD) scheduler algorithm and the Type 4 queue structure. The key objective is to determine the MIL-STD-188-220B parameter values that optimize performance in a fragmented net, with voice, situation awareness (SA), and Type 4 data traffic using the ITT TIDB Phase III OPNET-based networking model. Optimization is performed using the dynamic Taguchi robust design method. The matrix experiments are conducted with an L₁₈ orthogonal array. One of the most critical processes for the optimization of throughput with minimal delay is identification of the ideal function. Message completion and delay time are combined into a single quality characteristic for the purpose of maximizing the probability of delivering a message at a given delay time. Based on the Taguchi robust design experiments, three optimum sets, each yielding different scheduler speed, are recommended. Of the three sets, the one with the slowest scheduler speed, provides the greatest improvement in performance of the mission critical C2 multicast and unicast messages