MANET Route Optimization using Cross-Layer Enhancements in Tactical Radio Waveforms

Cross Layer interactions have gained acceptance in communications protocol stacks in order to optimize the operation of network nodes with ever increasing sophistication. In a related paper [4] we discuss the role of selecting a cross layer architectural framework for mobile tactical communications nodes. If we go to the effort of developing a cross-layer architecture for mobile tactical radio networks, will the performance gains justify the cost? This paper discusses the results from discrete event simulation studies that compare the gains made in network route optimization from cross-layer event data at the physical layer. Specifically, the Signal to Noise Ratio (SNR) calculated by a mobile radio in a deployment environment is used to adjust the signal modulation order and hence the data capacity of links formed between mobile nodes. The radios dynamically adjust the data capacity of the links. Many routing protocols never update routing link cost after initialization which leads to inefficient routing paths in a dynamic RF environment such as seen in mobile tactical networks. Simulation studies show that converting physical layer events to a metric such as current link data capacity and reporting this to a routing protocol that can dynamically change route selection cost results in overall network throughput gains and improved network convergence times. Results show a comparison of mobile network simulation scenarios which demonstrate the gain of the cross layer protocols as opposed to the network performance without consideration of cross layer interaction.