Cognitive Radio Applications in Software Defined Radio

The topic of cognitive radios has been garnering a great deal of attention in the past several years. Opinions regarding the level of sophistication necessary to qualify a system as cognitive vary widely, and discussions have ensued regarding this technology. The software defined radio forum is also involved and has working group activity in the area of cognitive radio. Some of the working group results are shown in this paper. The modern software defined radio is the heart of a cognitive radio. The applications executing on the radio distinguish a cognitive radio from a software-defined radio. Additional hardware in the form of sensors and actuators enables more cognitive radio applications. Some of the enabling technology is presented in this paper. Various artificial intelligence approaches to machine learning and decision making may be applied to the cognitive radio system. In this paper, a survey of related cognitive radio topics is reviewed and candidate application architectures are presented. Section 1 is an introduction to the basis of cognitive radios from a hardware, software, and artificial intelligence point of view. Section 2 discusses the sensors and actuators needed by a cognitive radio. Section 3 presents software architectures for radio learning and ultimately cognition. Section 4 is the heart of the paper and describes three candidate cognitive radio applications. Some future trends and conclusions are presented in Section 5. 1. COGNITIVE RADIO ENABLING TECHNOLOGY Software Defined Radio (SDR) and Artificial Intelligence (AI) technology enable the new field of Cognitive Radio (CR). An overview of these two areas is presented in this section. Cognitive Radio A Cognitive Radio is an extension of modern Software Defined Radio. This extension creates new capabilities for users. The evolution of radio technology is shown in Figure 1. An “aware radio” has sensors and is aware of the environment (or at least a subset of the environment). An “adaptive radio” is aware of its environment and is capable of changing its behavior in response. The next level is CR, and the following characteristics are included in my concept of a CR: • Sensors creating awareness in the environment • Actuators enabling interaction with the environment • Memory and a model of the environment • Learns and models specific beneficial adaptations • Has specific performance goals Figure 1 – Cognitive Radio. The next goal in the development of SDR technology is a Cognitive Radio because CR enables new capabilities. The regulator’s desire of absolutely predictable behavior is beyond the scope of this paper. Questions such as the following must be addressed: Is all learning accomplished prior to fielding the system? Is learning and Proceeding of the SDR 04 Technical Conference and Product Exposition. Copyright © 2004 SDR Forum. All Rights Reserved behavior constrained? How is this demonstrated to regulators? The SDRF Cognitive Radio Working Group is developing a different set of definitions along these lines. The nomenclature document will be released soon and the Cognitive Radio discussed in this paper is similar in concept to the Heuristic Radio in the SDRF Cognitive Radio Working Group documents. Software Defined Radio A software-defined radio has several major sub-systems, but is essentially a distributed computing system. In this section, the major sub-systems are discussed.