Testbed Implementation of Loop-Free Soft Handoff in Wireless Battlefield Networks

A fundamental challenge in wireless mobile battlefield networks WMBNs is frequent occurrence of wireless link congestion and failures due to blockage, mobility, interference, etc. In case of a link or node failure, the end-to-end session will be disrupted until the underlying routing protocol converges to its new path. We propose an innovative distributed architecture for a seamless multi-layer soft handoff protocol in WMBNs to provide the sub-second convergence in case of linknode failures . Our architecture utilizes a proactive make-before- break approach by introducing the concept of pre-computed remote Loop-Free Alternate Paths LFAPs on top of local LFAPs proposed by the IETF IP Fast-Reroute framework. We implemented this framework in the laboratory test bed using real COTS routers and collected statistics related to the convergence times and alternate path coverage ratios of local and remote LFAPs. The convergence experiments show that the convergence time of the remote LFAP mechanism is only slightly higher a few tens of milliseconds compared to that of the local LFAP. Our coverage analysis showed that, by using only a small neighborhood e.g., 2-hop neighborhood, a complete LFAP coverage can be achieved for most topologies generated by the BRITE topology generator. These results are significant since the IP fast reroute with a complete coverage can be achieved for WMBNs by introducing only a minimal overhead bounded within a small neighborhood.