Whether it is for public safety, homeland security or military communications, access to spectrum is critical, especially as the spectrum get congested with time and usage mushrooms. Despite the progress in the last decade or so in multiband and multimode receivers and smart radios, the problem continues to haunt spectrum managers and users. As a result, researchers and developers have continued to advance intelligent and adaptive radio technologies with sophisticated algorithms to dynamically access frequencies without interference to other legacy radios. Dynamic spectrum access or DSA is one of them.

DSA enables real-time adjustment of spectrum resource usage in response to changing circumstances and objectives, including interference experienced or created, changes of the radio's state (operational mode, battery life, location, etc.), changes in environmental/external constraints (spectrum, propagation, operational policies, etc.); changing circumstances and objectives may also include energy conservation, interference avoidance, spectrum-usage efficiency, quality of service (QoS), graceful degradation guidelines and maximization of radio lifetime. While its physical layer operating functions and parameters (e.g., frequency range, modulation type or maximum output power) are implemented and controlled through use of software processing without making changes to hardware components that affect RF emissions, it includes RF devices that are aware of their environment and internal state and can make decisions about their radio operating behavior based on that information and predefined objectives. Plus, it uses software-defined radio (SDR), adaptive radio, and other technologies to automatically adjust its behavior or operations to achieve desired objectives.

In the first feature, Shared Spectrum Company (SSC) authors Salvador D'Itri and Mark McHenry demonstrate that dynamic spectrum access technology is available now to provide the critical link through a wireless software suite comprising policy-based rules and database engines that drive algorithms for frequency agility and cognitive decision-making. The suite enables an environment for users to adopt DSA and begin to address spectrum challenges and enable innovation and growth in wireless solutions.

In this article titled “Dynamic spectrum access moves to the forefront,” D'Itri and McHenry describe DSA in more detail and show that it was first demonstrated in 2006 by the Defense Advanced Research Projects Agency (DARPA) and SSC. According to the article, DSA software technology enables users of virtually any modern radio device to use dynamic spectrum access techniques and thereby dramatically improve spectrum efficiency, communications reliability, and deployment time. Fundamentally, a device running DSA software dynamically senses and adapts to its RF environment to maintain reliable communications with other DSA-enabled devices, and it does so without interference with non-DSA enabled systems (i.e., non-cooperative or legacy radios). Furthermore, a DSA-enabled radio operates within prescribed policy constraints, which may vary depending upon geographic location, frequency band, time of day, legacy radio activity and other anticipated or unanticipated factors. DSA presents an opportunity to harvest licensed, under-used spectrum to enhance everything from mission-critical wireless access to consumer wireless consumption. According to the article, DSA technology can change our use of spectrum assets the way the IP protocol changed our use of traditional switched network communications.

There are many benefits of MIMO technology. And its usage in the military tactical systems is on the rise. In the second feature, “MIMO: The next revolution in wireless data communications” by Babak Daneshrad of Silvus Technologies, the author provides a technical overview of MIMO and its different variants. Besides quantifying some of its benefits, this article identifies key capabilities that efficient MIMO development/evaluation platforms must offer.

After making a reliable connection, the communication system must ensure that the data is protected from interference and enemy reproduction. Especially in the event the end system is captured, security enhancements integrated in the system design must ensure that the information is secure and tamper proof. The third feature, “Protecting the key is the “key“ to secure communications” by Dave Locke of ON Semiconductor provides an overview of potential security enhancements including the use of volatile memory of the key code and integration of the key code memory within the system electronics to optimize the key protection.