Cooperation and Cognition for Railway Communications

In recent years, a new paradigm for communication called cooperative communications has been proposed for which initial information theoretic studies have shown the potential for improvements in capacity over traditional multi-hop wireless networks. Cooperative communication involves exploiting the broadcast nature of the wireless medium to form virtual antenna arrays out of independent single-antenna network nodes for transmission. The field of telecommunication networks involves exchange of information messages among a collection of terminals, links, and nodes that are connected together. The field has advanced tremendously and has generated many breakthroughs in research and technology innovations in the past century. The fundamental goals that have driven communications and networking research and technology developments mainly solve two problems: how to increase communication rates over a communication link connecting two nodes and how to increase the communication reliability to minimize the errors in information delivery. The first goal often refers to spectral efficiency, measured by bits per second per hertz. The second goal often refers to information multi-capacity or channel capacity, measured by the bits per second that can be achieved with arbitrarily small error probability. Emerging classes of wireless networks, such as ad hoc and sensor networks and cellular networks with multiple hops, often consist of a large number of nodes in different geometric locations. Compared with classical point-to-point systems, these new types of networks are extremely difficult to analyze and optimize. Therefore, new theoretical and practical techniques are needed to augment classical communication and networking theory and practice. The current spectrum allocation policy is highly inefficient, which is one of the main reasons that lead to significant underutilization of spectrum in the face of explosive growth in demand. The radio spectrum is the radio frequency (RF) portion of the electromagnetic spectrum, which is a natural resource used by the transmitter and receiver to transmit signals. In order to solve the shortage in spectrum resources and to improve the spectrum utilization, cognitive radio (CR) has been proposed, which allows a secondary user (unlicensed user) to exploit spectrum holes at a given time and location and transmit. The spectrum hole is the frequency band that is unoccupied by the primary user (licensed user), and can be exploited temporally, spectrally, and spatially. The concept of cognitive radio was first proposed by Mitola in 1999, whereby a radio can adapt and dynamically reconfigure itself based on its RF environment. After a decade of research, cognitive radio has attracted a lot of interest. Recently, cognitive radio has been considered as a promising candidate technique in the upcoming 5G wireless systems. In this chapter, we start from the introduction of fundamental cooperation and cognition, followed by a brief review of the application in railway communications.