QoS-aware Adaptive Middleware (QAM) for tactical MANET applications

Developing distributed applications for MANETs is a complex task due to the latter's bandwidth constrained nature. Further, in tactical MANETs, there is a need to prioritize traffic generated by distributed applications so that high priority traffic gets preferential access to the bandwidth constrained communication medium. Finally, applications must be designed to accommodate network bandwidth and traffic loads that vary with time. It is unrealistic to expect individual application developers to be able to accommodate these constraints which essentially cut across multiple applications that share the MANET. In this paper we describe a communication middleware system: QoS-aware Adaptive Middleware (QAM) that shields distributed application developers from the complexities of tactical MANETs. QAM resolves the problem of bandwidth contention between multi-priority applications by providing an adaptive, priority aware, middleware layer that acts as an intermediary between an application and the network protocols it uses. QAM adapts to current network conditions by providing a reliable data transfer mechanism that is capable of adapting data transfer rates in response to changing network conditions. The adaptations performed by QAM attempt to limit the use of network bandwidth by applications when network bandwidth is diminished. Moreover, QAM limits network use more aggressively for lower priority applications than for higher priority applications, thus giving preferential treatment to the latter. Existing network layer mechanisms such as priority queuing and bandwidth provisioning are either inadequate or inapplicable for addressing traffic prioritization needs in tactical MANETs. QAM provides capabilities that are complementary to existing QoS mechanisms and is better suited for tactical MANETs. Our paper provides a description of the QAM architecture and early evaluations of a QAM prototype.