Abstract
Cognitive Radio (CR) and Software Defined Radio (SDR), concepts which were mere proposals to solve the population of services over the past two decades, are now enabled by novel materials and components to offer fully reconfigurable devices. Thus, a convergence of services can be attained within a reduced, or even single RF (Radio Frequency) signal path in the device. A solid design of reconfigurable frontends, from the RF part to the digital baseband, should consider different criteria to better exploit the available spectrum. Examples of such criteria are scattering parameters and phase linearity of components at a defined carrier frequency, RF signal bandwidth, and signal quality in terms of Error Vector Magnitude and Bit Error Rate. In this chapter, a general perspective to achieve smarter air interfaces is studied and discussed by setting out strategies based on CR and SDR techniques for the implementation and integration of future reconfigurable RF-Frontends.
TopReconfigurable Frontends: A Smarter Air Interface Between Cognitive Radios
With the steady growth of services and applications for portable devices, dynamic and adaptable communication approaches are strongly required. In that way, an agile reconfiguration should take into account every layer of a typical communication system, i.e. from the application layer down to the physical layer (Tanenbaum, 2003). Nevertheless, while a clear roadmap for protocols and standards has been developed, at the physical layer the RF-Frontend of a device reaches a bottleneck to satisfy forthcoming demands (Nguyen, Villain, & Le Guillou, 2012). In Figure 1, a scenario taking into account a fully-sensed urban area, also known as smart city, shares information in a smart way so that a single user can exploit it by using a single reconfigurable platform. Here, wireless coordination of sensing devices and cooperative computing are enabled to perform different tasks such as tracking, traffic information, monitoring, warning and surveillance. In this way, by means of Cognitive Radio techniques, the aim is to constantly sense the RF environment so that an efficient management of the network resources, namely the wireless spectrum, supported by allocation algorithms can be obtained, either in the baseband or in the RF-Frontend. Thus, an integration of distributed sensors and networks with portable devices like mobile phones, tablets, and PDAs, is required to achieve the convergence of information and its different communication technologies into global service platforms.
Figure 1.
Interoperation of services and convergence of applications performed by a single reconfigurable platform. By employing CR and SDR techniques, the design of a platform towards universal capability, reconfigures its hardware so that a smart communication between distributed sensors and networks is enabled.
Key Terms in this Chapter
Smart Air Interface: Set of concepts, components and elements that altogether enable a device to be capable of communicate with its environment in a cooperative network.
Smart City: Sensed urban area that shares information in a smart way to ease communication and to improve life quality of its inhabitants.
Internet of Things: Interconnection of miscellaneous physical and virtual objects in an Internet-like fashion.
Convergence: Description of different communication systems performing tasks within a shared medium and distributed network architecture.
Tunable Components: RF components or devices able to change its microwave characteristics by means of an external electric or magnetic field.
Cognitive Radio: Constant sensing of the RF environment to efficiently achieve an allocation of RF resources supported by different algorithms, either in the baseband or in the RF part.
Reconfigurable Transceiver: Device enabled to adapt its characteristics for communication with upcoming and current supported technologies and protocols within a sensor network environment.