The Army currently spends Billions procuring similarly functioning, but developmentally stove-piped Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR) and Electronic Warfare (EW) systems. Most notably, the Army's communications systems are neither developed nor integrated in tandem with their EW system counterparts, even though both have many common components with similar functionality. In addition, because all of these C4ISR and EW systems compete for extremely limited Radio Frequency (RF) spectrum and Size, Weight, and Power (SWaP) resources, they are prohibitively costly to integrate and procure, and their performance suffers from many conflicting requirements. The resultant multitude of systems and system configurations dramatically increases the logistical burden on our Combat Brigades that need to sustain, transport, and upgrade these capabilities. In order to address these problems, the Communications-Electronics Research, Development and Engineering Center (CERDEC) is integrating Communications and EW components into common modular, multifunctional hardware as a "Universal A-kit." This modular approach uses open interface standards and enables specialized domain cards (e.g., Communications, EW, Position Navigation and Time, Signals Intelligence, Mission Control, etc.) to integrate multiple functions onto a common chassis.

In this paper, we investigate general handoff problem for ad hoc wireless networks in face of multiple heterogeneous wireless interfaces and non-trivial node mobility. The handoff problem in ad hoc networks has major differences with respect to its counterpart in infrastructure networks, as handoff decisions are not restricted to simple evaluation of single-hop performances of available link interfaces but rather require a network-wide evaluation of ad hoc nodes. This requires an integrated multi-layer approach as indicated in our earlier efforts. In this study, we extend our existing work on developing an integrated framework through a cross layer approach. Further, we identify the key interrelation between the topology control and handoff processes and provide a multi-interface topology control process that maintains coordination between network nodes via k-hop clustering mechanism.

In our papers for MILCOM 2006 and 2007, we have presented an integrated architecture for seamless soft handoff in mobile ad hoc networks and demonstrated the good performance via showing that our handoff scheme can provide equivalent results as the benchmark with no handoff. In this position paper, we aim to investigate the general handoff problem in face of multiple heterogeneous wireless interfaces and non-trivial node mobility. This becomes ever important, since wireless heterogeneity will persist and nodes in military ad hoc networks are bound to move beyond rare-and-slow scenarios. The combination of wireless heterogeneity and mobility incurs lots of challenges in research and development, and the ultimate goal in our research is to provide transparent and seamless user experience in such environments without fixed or predictable infrastructure support. This paper identifies such challenges across the stack, investigates the design space, and points out promising research avenues. Finally, we investigate how such ideas may be implemented in the integrated architecture, which also contains the IEEE 802.21 Media Independent Handover functionality as a supporting component.

In our MILCOM 2006 paper [1], we have presented an integrated architecture for seamless soft handoff in mobile ad hoc networks, where various managers residing on multiple layers are proposed to tackle handoff issues in a cross-layer and cooperative manner. In this paper, we first demonstrate the handoff performance under nontrivial node mobility. Simulations show that our handoff scheme provides practically equivalent results as the benchmark with no handoff, which indicates that our scheme is quite resistant to node mobility. Next we investigate the general handoff problems where each node can possess multiple radios and nodes are randomly dispersed in some region. In this case, the network topology forms a multi-linked graph (multigraph). By converting the multigraph to simple graphs, our extensive simulations show that our scheme can render low latency, low overhead handoff with minimum packet loss. Finally, we study the synergies with IEEE 802.21 and describe how to integrate IEEE 802.21 into our multi-layer architecture.