Cognitive Radio generates interest from the military

However, according to Ari Hulkkonen, senior manager at Elektrobit, it has been more the requirements at the demand end of the chain, rather than technology at the supply end, that has driven development. "From the technology point-of-view, Cognitive Radio is mostly based on existing technologies and solutions. The key is how these technologies are applied. "Cognitive radio breaks the traditional rules of strictly regulated wireless communications and spectrum allocation with the main goal to improve the overall spectrum utilisation and efficiency. The key driving force has been the rapid development of the mobile communications with the bandwidth thirsty internet access provided to handheld devices. The all increasing demand for peak data rates and system capacity requires more bandwidth but the problem is that the usable radio spectrum is already allocated. Cognitive Radio is a key technology to solve the problem." The main application then becomes the more efficient use of the 'TV white spaces' - the frequencies between the channels in the TV spectrum that are either unused or not used permanently. "Considering the implementation, software defined radio is one of the key implementation techniques as the radio equipment must be able to switch between waveforms in addition to just changing the operating frequency," continued Hulkkonen. "This applies especially to military communications and also to commercial cellular networks but so far most handsets are still based on dedicated chip sets." The decision making logic in a CR is contained in the cognitive engine, which can configure such parameters as waveform, operating frequency, protocols and the network. A CR continuously monitors its own set-up, performance and environment and uses this information to optimise its operation and it is this behaviour that makes it particularly appropriate to the defence arena, as Hulkkonen describes: "Cognitive radio is aware of its radio environment and the available communication resources – an awareness based on using existing knowledge and databases or active sensing. "It can optimise the link and system performance by avoiding interference and by selecting the best communication methods while operating in a busy radio spectrum. A military communications system operates under very similar conditions, although the primary interest is not to avoid causing interference to the primary users of the spectrum, but to hide and avoid being interfered with. Collaborative spectrum sensing, decision making (the cognitive engine) and how to implement the decisions in practice are common to both cognitive radio and advanced military communications systems." Frequency selection and changes of frequency will be determined within the cognitive engine and such decisions are sent to each node and terminal in the network, which means a logical or physical control channel must be used. If the cognitive engine is centralised the task is straightforward, but if it is distributed the control becomes more complex. An obvious issue regarding military applications, particularly if these networks are going to be on the front line, is concern about security. There are two ways to address this said Hulkkonen: "Encryption, which can be applied to various layers of communication, is the common way to prevent your transmission to be decoded. However, if trying to hide the transmission, the key is to use short transmissions, as low power or spectral power density as possible, frequency hopping and spread spectrum techniques, to mention a few examples. "With situational awareness, a CR system can optimise its operation to keep the overall power levels as low as possible, route the data in the system so that long hops that require high power are avoided, optimise the antenna directions to minimise the signal emitted towards the enemy and avoid the interference sources by selecting right frequencies in addition to optimising the antenna directions." Widespread adoption in the defence environment might seem an obvious next step, but it may be that in many cases the practical problems could outweigh the technical advantages. "Many defence organisations use rather old communications systems and it is perhaps not possible to upgrade them to have cognitive functionality," explained Hulkkonen. "Secondly, the life-time of a military communications system and equipment can be decades and it is a long and time-consuming process to upgrade them unless radical decisions are made to replace all at once. "A network management system is also required to allow centralized frequency allocation and parameter control, which may be an issue in many cases today, too. While digital and SDR based radio systems are gradually getting more common, it will also be possible to update the system functionality afterwards." Another issue is that every country and warzone presents unique spectrum access conditions and there is the further complication of communicating with allied or coalition forces, and so further research into both technology and implementation continues. However, it appears that wireless CR-based systems could form a useful and flexible component in a typical hybrid military communications system, typically sitting alongside UAVs, satellites and terrestrial wired connections. Finnish defence forces look to cognitive radio systems Elektrobit's Tactical Wireless IP Network (TAC WIN) is a complete solution to building a tactical communications mobile ad hoc network for vehicle and stationary applications and includes cognitive radio technologies. With TAC WIN, battle groups can create high-data-rate wireless IP networks as backbones to support C2 data transmission during operations. The flexibility offered by such a solution in different frequency bands and network topologies suits various tactical communication scenarios. TAC WIN has been selected by the Finnish Defence Forces for the next generation of its wireless networks. FDF is building its new wireless command system where TAC WIN forms the core network providing the key connections between command centres and the forces on the field. It interfaces to other communications systems that extend the coverage of the command system all the way to individual soldiers. Hulkkonen commented: "Finnish Defence Forces has launched an R&D program called Technology Programme 2013, in which a cognitive mobile adhoc network is the key application. The program aims at developing cognitive solutions directly applicable to FDF's new wireless command system (based on TAC WIN). The program also comprises other technology areas but is a significant investment in CR by the FDF. "In addition to the FDF's technology program, the Finnish Technology Funding Agency (Tekes) is coordinating and funding a large research and development program called TRIAL. The goal of TRIAL is to develop cognitive radio technology and to demonstrate it. Elektrobit has its own project within TRIAL program, with the intention to provide solutions that can be applied not only to commercial applications but to TAC WIN too."