Design consideration of router-to-radio interface in mobile networks

In order to provide versatile and reliable transport of data, voice and video traffic, military organizations deploy complex communications systems that integrate terrestrial, airborne, and space-based platforms. In these tactical communication systems, typically wireless networks, interface with COTS routers at the sub-network boundaries to form a contiguous network infrastructure. The wireless sub-systems employed in such tactical communications networks are susceptible to time-varying link quality due to dynamic network conditions. In such situations, ordinary routers are unaware of the quality of the wireless links, resulting in problems with network flow- control and link-state detections. In the end, this problem leads to suboptimal operations of the network as a whole. The IETF RFC 5578 has addressed this issue with a router- to-radio interface protocol standard. This protocol, based on a supplier-consumer model, provides a method to arbitrate bandwidth between the time-invariant throughput found in the Ethernet interface and the time-varying link capacity of the RF link. Specifically, this protocol improves RF link utilization by employing a flow-control mechanism resulting in rapid link state detection on the RF links that allows the router to make a more informed decision based on known link cost. While IETF RFC 5578 provides much improved RF link utilization in the network, this protocol is known to cause packet loss and/or degraded router performance under high data rate conditions. This is due to the protocol's need for frequent credit updates between router and the radio, as well as finite buffer space at the radio. In this paper, we propose a solution to this problem that features a new flow-control protocol for regulating bandwidth usage between the COTS routers and the radios, in place of the currently used RFC 5578's protocol. The proposed mechanism not only eliminates the aforementioned packet loss and/or performance problem encountered with RFC 5578, it also removes the requirement for resource- tracking by the routers and radios, thus making it simpler and more efficient to employ.