Communications and Networks

Military radars, military communications networks, and commercial communications networks all require increasing amounts of limited radio frequency spectrum. Balancing national security requirements of radars and military networks with the growing bandwidth demands of commercial wireless data networks calls for innovative approaches to managing spectrum access. DARPA’s Shared Spectrum Access for Radar and Communications (SSPARC) program aims to improve radar and communications capabilities for military and commercial users by creating technical solutions to enable spectrum sharing.

In areas lacking trustworthy communications infrastructure, deployed servicemembers rely on wireless devices to perform double duty: they not only provide access to the network; they are the network. Protocols for these networks require nodes to coordinate among themselves to manage resources, such as spectrum and power, and determine the best configurations to enable sharing of information. A problem with these protocols is that they implicitly trust all information shared about the security and operational state of each node, and the network as a whole. Consequently, inaccurate control or security information can quickly render the network unusable. This shortcoming could put productivity and mission success at risk as use of military wireless systems increases.

Troops operating in forward locations without telecommunication infrastructure often rely on a mobile ad hoc network (MANET) to communicate and share data. The communication devices troops use on foot or in vehicles double as nodes on the mobile network. A constraint with current MANETs is they can only scale to around 50 nodes before network services become ineffective. For the past 20 years, researchers have unsuccessfully used Internet-based concepts in attempts to significantly scale MANETs.

Air-ground fire coordination—also known as Close Air Support or CAS—is a dangerous and difficult business. Pilots and dismounted ground agents must ensure they hit only the intended target using just voice directions and, if they’re lucky, a common paper map. It can often take up to an hour to confer, get in position and strike—time in which targets can attack first or move out of reach. To help address these challenges, DARPA recently awarded a contract for Phase II of its Persistent Close Air Support (PCAS) program to the Raytheon Company of Waltham, Mass.

As wireless devices proliferate and the radio spectrum becomes ever more congested, all users have a common interest in radio technologies that can accommodate the largest number of users but still enable priority traffic to get through. The DARPA Spectrum Challenge—a competitive demonstration of robust wireless technologies—recently announced the selection of 15 of 18 semifinalists for $150,000 in prize money. DARPA plans to fill three remaining wildcard slots in August 2013 before the September 2013 semifinals at DARPA’s offices in Arlington, Va.