| The Joint Tactical Radio System (JTRS) Wideband Network Waveform (WNW) is applying the latest advances in distributed ad-hoc networking to a wide range of military applications and platforms. The Mobile Data Link (MDL) provides the channel access for WNW using adaptive TDMA to efficiently schedule transmissions in the face of scarce channel resources, challenging throughput and latency requirements, and mobility. Spatial reuse over time and frequency is achieved by enforcing multi-hop constraints to minimize self-jamming (hidden terminal problem) while taking advantage of simultaneous transmissions whenever possible (exposed node problem). Channel resources are managed to concentrate them in the nodes that can best utilize them both from a topological point of view, i.e. to serve as relays, and to alleviate congestion. The MDL provides the routing layer above it with a one-hop broadcast and unicast service that is available without prior reservation for use on the currently selected channel. This makes use of both allocated TDMA slots and contention slots. In addition, a unicast reservation can be made for communications to other channels if the node is serving as a gateway between operational units on different channels. This paper will describe the architecture of the MDL, its major functions and unique algorithms, and its adaptability to different operational scenarios based on configuration parameters. It will also present performance results based both on recent lab tests using pre-EDM units and on shared code simulation models that uses the MDL operational code in realistic emulated networking environments. |