Keith Nolan

Cyclostationary Signatures in Practical Cognitive Radio Applications

We define a cyclostationary signature as a feature which may be intentionally embedded in a digital communications signal, detected through cyclostationary analysis and used as a unique identifier. The purpose of this paper is to demonstrate how cyclostationary signatures can be exploited to overcome a number of the challenges associated with network coordination in emerging cognitive radio applications and spectrum sharing regimes. In particular we show their uses for signal detection, network identification and rendezvous and discuss these in the context of dynamic spectrum access. We present a theoretical discussion followed by application-oriented examples of the cyclostationary signatures used in practical cognitive radio and dynamic spectrum usage scenarios. We focus on orthogonal frequency division multiplexing (OFDM) based systems and present an analysis of a transceiver implementation employing these techniques developed on a cognitive radio test platform.

Cognitive radio: Ten years of experimentation and development

The year 2009 marked the 10th anniversary of Mitola and Maguire Jr. introducing the concept of cognitive radio. This prompted an outpouring of research work related to CR, including the publication of more than 30 special issue scientific journals and more than 60 dedicated conferences and workshops. Although the theoretical research is blooming, with many interesting results presented, hardware and system development for CR is progressing at a slower pace. We provide synopses of the commonly used platforms and testbeds, examine what has been achieved in the last decade of experimentation and trials relating to CR, and draw several perhaps surprising conclusions. This analysis will enable the research community to focus on the key technologies to enable CR in the future.

Iris: an architecture for cognitive radio networking testbeds

Iris is a software architecture for building highly reconfigurable radio networks. It has formed the basis for a wide range of dynamic spectrum access and cognitive radio demonstration systems presented at a number of international conferences between 2007 and 2010. These systems have been developed using heterogeneous processing platforms including general-purpose processors, field-programmable gate arrays and the Cell Broadband Engine. Focusing on runtime reconfiguration, Iris offers support for all layers of the network stack and provides a platform for the development of not only reconfigurable point-to-point radio links but complete networks of cognitive radios. This article provides an overview of Iris, presenting the unique features of the architecture and illustrating how it can be used to develop a cognitive radio testbed.

A Reconfigurable Platform for Cognitive Networks

By introducing self-awareness and computational intelligence to reconfigurable radio networks, cognitive networks are viewed as the key to a new generation of self-configuring, self-optimizing and self-healing communications systems. However, in order to make such systems realizable, a paradigm shift in the design of network node architectures is required. This paper presents a reconfigurable platform based on an architecture specifically designed for nodes within a cognitive network

Cyclostationary Signatures for Rendezvous in OFDM-Based Dynamic Spectrum Access Networks

Distributed coordination of operating frequencies and bandwidths is one of the key challenges in the development of dynamic spectrum access (DSA) technology. The spectrum efficiency of DSA networks is achieved through the use of spectrum white spaces, frequency bands which are unoccupied at a given time and place. The issue of frequency rendezvous arises as the availability of these white spaces may change dynamically in frequency, time and space. We propose a novel solution to the problem of distributed rendezvous in dynamic spectrum access networks using cyclostationary signatures. By embedding a cyclostationary signature or watermark in a transmitted signal, the received signal can be uniquely detected, classified, and used for frequency acquisition by distributed dynamic spectrum access-enabled nodes in a network. This paper therefore makes three key contributions. First, a solution to the problem of distributed rendezvous in DSA networks using the novel concept of cyclostationary signatures is presented. Second, a low-complexity technique for generating these cyclostationary signatures in OFDM (orthogonal frequency division multiplexing) waveforms is described. Finally, an initial performance analysis of an implemented test platform is discussed.

Cyclostationary Signature Detection in Multipath Rayleigh Fading Environments

Cognitive radio-based Open Spectrum systems offer a solution to the issue of spectrum scarcity by allowing wireless networks to dynamically access spectrum while coordinating to co-exist and avoid the creation of harmful interference. However, before a practical open spectrum system may be implemented, a number of significant technical and policy challenges must be overcome. One such technical challenge is the distributed coordination of operating frequencies and bandwidths between co-existing systems. Cyclostationary signatures have been shown to be a powerful tool in overcoming this challenge. A cyclostationary signature is a unique identifier or watermark which may be embedded in the physical properties of a communications signal. Such signatures may be used to aid peer devices in performing a number of critical tasks, including signal detection, classification and frequency acquisition. A key limitation of cyclostationary signatures when implemented in orthogonal frequency division multiplex (OFDM)-based systems is the sensitivity exhibited in time-variant multipath Rayleigh fading environments. Although OFDM-based systems offer robust performance under multipath conditions, detection of cyclostationary signatures can be severely degraded. As signature detection is adversely affected, the ability of Open Spectrum Systems to coordinate and coexist is seriously undermined. This paper therefore presents techniques for effectively over-coming the issue of multipath Rayleigh fading in the detection of cyclostationary signatures for Open Spectrum systems. Approaches for the generation and detection of signatures in OFDM-based waveforms are outlined and improvements in detection performance are illustrated using simulation results.

5G: The Convergence of Wireless Communications

As the rollout of 4G mobile communication networks takes place, representatives of industry and academia have started to look into the technological developments toward the next generation (5G). Several research projects involving key international mobile network operators, infrastructure manufacturers, and academic institutions, have been launched recently to set the technological foundations of 5G. However, the architecture of future 5G systems, their performance, and mobile services to be provided have not been clearly defined. In this paper, we put forth the vision for 5G as the convergence of evolved versions of current cellular networks with other complementary radio access technologies. Therefore, 5G may not be a single radio access interface but rather a “network of networks”. Evidently, the seamless integration of a variety of air interfaces, protocols, and frequency bands, requires paradigm shifts in the way networks cooperate and complement each other to deliver data rates of several Gigabits per second with end-to-end latency of a few milliseconds. We provide an overview of the key radio technologies that will play a key role in the realization of this vision for the next generation of mobile communication networks. We also introduce some of the research challenges that need to be addressed.

Radio Transmitter Fingerprinting: A Steady State Frequency Domain Approach

We present a novel technique for radio transmitter identification based on frequency domain characteristics. Our technique detects the unique features imbued in a signal as it passes through a transmit chain. We are the first to propose the use of discriminatory classifiers based on steady state spectral features. In laboratory experiments, we achieve 97% accuracy at 30 dB SNR and 66% accuracy at OdB SNR based on eight identical universal software radio peripherals (USRP) transmitters. Our technique can be implemented using todays low cost high-volume receivers and requires no manual performance tuning.

Cognitive radio for medical body area networks using ultra wideband

Wearable wireless medical sensors beneficially impact the healthcare sector, and this market is experiencing rapid growth. In the United States alone, the telecommunications services market for the healthcare sector is forecast to increase from

An evaluation of low power wide area network technologies for the Internet of Things

7.5 billion in 2008 to