# A Review on Internet of Things for Defense and Public Safety
## 4 Operational Requirements
### Interoperability Capabilities  
Taking advantage of the full value of IoT is about maximizing the number of hardware and software systems, nodes and connections in the data ecosystem. However, defense lacks a cohesive IT architecture. The different and heterogeneous systems are developed independently and according to different operational and technical requirements. Frequently, multiple services are involved in an operation, or several departments are involved in a process, but information has to be adapted between their systems manually. The usage of different hardware designs and data standards can impact the cohesion of defense infrastructure, leading to stove pipe systems. The fragmentation of the architecture also complicates the use and development of common security protocols. Adequate interoperability between devices is often not achieved given the variety of functions served by defense hardware, the integration across partners, or when potentially useful devices in an area of operations are to be leveraged (i.e., smart city deployment). IoT capabilities across an enterprise as broad as defense can only be delivered through a suite of common standards and protocols. To enhance end-to-end interoperability, one of the most popular approaches is the usage of Service-oriented Architectures (SoAs). SoAs use common messaging protocols and well-defined interfaces to share information between multiple services. They consider aspects such as service reuse,rapid configuration, and composability with dynamic workflows. SoAs in the tactical domain could help to leverage commercial IoT capabilities and attempt to address the interoperability challenges specific to C4 ISR. Both military computers and sensor networks should have longer service lives than commercial equivalents, resulting in greater needs to maintain legacy systems. One of the key weaknesses of legacy systems is their lack of interoperability. This limits significantly the ability to integrate new platforms into the defense digital ecosystem, and to leverage existing systems in innovative ways. DISA is implementing a cohesive digital architecture through the Joint Information Environment (JIE) initiative [110] to unify capabilities, facilitate collaborations with partners, consolidate infrastructure, create a single security architecture, and provide global access to services. TacNet Tactical radios [111] help to demonstrate how an open systems architecture can enable improved interoperability between next-generation and legacy fighter aircrafts. Lockheed Martin performed tests on a F-22 and F-35 Cooperative Avionics Test Bed (CAT-B). Those aircrafts were flown to assess the capability to share real-time information among varied platforms. The ability to transmit/receive Link-16 communications on F-22 was proven, also the software reuse and reduction of the aircraft system integration and the use of Air Force UCI messaging standards. U.S. Army CERDEC NVESD [112] has developed ISA under the Deployable Force Protection program. ISA is an interoperability solution that allows components to join a tactical network and use its functionality without requiring neither prior knowledge of the resources available on that network, nor physical integration. ISA uses dynamic discovery to find other ISA-compliant systems, regardless of platform. This dynamic discovery is accomplished by requiring all members to announce the data they provide and functionality they can perform when they connect to the network. Members can change their capabilities on the fly and search for others that provide either data or the functionality they need. ISA understands the capabilities of those sensors and shares their information with operators. When future sensors come online to a network, they can register and communicate their capabilities. Assets and sensors on that network can then subscribe to the types of information they are interested in. ISA seeks to provide the critical capabilities needed for a forward operating base to defend itself.