scispace - formally typeset
Search or ask a question
Author

Brian M. Sadler

Bio: Brian M. Sadler is an academic researcher from United States Army Research Laboratory. The author has contributed to research in topics: Fading & Communication channel. The author has an hindex of 52, co-authored 419 publications receiving 14773 citations. Previous affiliations of Brian M. Sadler include University of Leicester & Lehigh University.


Papers
More filters
Journal ArticleDOI
TL;DR: An overview of challenges and recent developments in both technological and regulatory aspects of opportunistic spectrum access (OSA) is presented, and the three basic components of OSA are discussed.
Abstract: Compounding the confusion is the use of the broad term cognitive radio as a synonym for dynamic spectrum access. As an initial attempt at unifying the terminology, the taxonomy of dynamic spectrum access is provided. In this article, an overview of challenges and recent developments in both technological and regulatory aspects of opportunistic spectrum access (OSA). The three basic components of OSA are discussed. Spectrum opportunity identification is crucial to OSA in order to achieve nonintrusive communication. The basic functions of the opportunity identification module are identified

2,819 citations

Journal ArticleDOI
TL;DR: It is shown that cumulant-based classification is particularly effective when used in a hierarchical scheme, enabling separation into subclasses at low signal-to-noise ratio with small sample size.
Abstract: A simple method, based on elementary fourth-order cumulants, is proposed for the classification of digital modulation schemes. These statistics are natural in this setting as they characterize the shape of the distribution of the noisy baseband I and Q samples. It is shown that cumulant-based classification is particularly effective when used in a hierarchical scheme, enabling separation into subclasses at low signal-to-noise ratio with small sample size. Thus, the method can be used as a preliminary classifier if desired. Computational complexity is order N, where N is the number of complex baseband data samples. This method is robust in the presence of carrier phase and frequency offsets and can be implemented recursively. Theoretical arguments are verified via extensive simulations and comparisons with existing approaches.

974 citations

Journal ArticleDOI
TL;DR: In this article, a statistical model based on empirical data is presented, and it is shown how to use this model for deriving access strategies for the coexistence of Bluetooth and WLAN.
Abstract: Dynamic spectrum access is a promising approach to alleviate the spectrum scarcity that wireless communications face today. In short, it aims at reusing sparsely occupied frequency bands while causing no (or insignificant) interference to the actual licensees. This article focuses on applying this concept in the time domain by exploiting idle periods between bursty transmissions of multi-access communication channels and addresses WLAN as an example of practical importance. A statistical model based on empirical data is presented, and it is shown how to use this model for deriving access strategies. The coexistence of Bluetooth and WLAN is considered as a concrete example

549 citations

Journal ArticleDOI
TL;DR: This article presents the state-of-the-art of associated systems and their components and discusses related issues including communication link characterization, channel modeling, and link capacity study, as well as transceiver design, link duplexing, multiple access, and networking.
Abstract: Motivated by the recent and rapid developments in deep ultraviolet LEDs, solar blind ultraviolet filters, and detectors, this article reviews wireless UV technology used for communications and sensing in either line-of-sight or non-line-of-sight channel conditions. We present the state-of-the-art of associated systems and their components and discuss related issues including communication link characterization, channel modeling, and link capacity study, as well as transceiver design, link duplexing, multiple access, and networking. We also envision applications in the commercial and military sectors.

475 citations

Journal ArticleDOI
TL;DR: In this article, a general PAT model is given as well as the review of the common design criteria and the information theoretic and signal processing issues were also discussed.
Abstract: Pilot-assisted transmission (PAT) multiplexes the known symbols with the information bearing data. These pilot symbols and the specific multiplexing scheme are known at the receiver and can be exploited for channel estimation, receiver adaptation, and optimal decoding. Even though PAT has been used for many practical reasons, there still remains a need for an optimal design. The theory and methodology for the design of an optimal PAT have emerged, but much still remains unknown. In this article, the author has presented an overview of PAT. A general PAT model is given as well as the review of the common design criteria. The information theoretic and signal processing issues were also discussed.

449 citations


Cited by
More filters
Journal ArticleDOI

6,278 citations

Journal ArticleDOI
TL;DR: In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented and the cooperative sensing concept and its various forms are explained.
Abstract: The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented. Various aspects of spectrum sensing problem are studied from a cognitive radio perspective and multi-dimensional spectrum sensing concept is introduced. Challenges associated with spectrum sensing are given and enabling spectrum sensing methods are reviewed. The paper explains the cooperative sensing concept and its various forms. External sensing algorithms and other alternative sensing methods are discussed. Furthermore, statistical modeling of network traffic and utilization of these models for prediction of primary user behavior is studied. Finally, sensing features of some current wireless standards are given.

4,812 citations

Journal ArticleDOI
TL;DR: An overview of challenges and recent developments in both technological and regulatory aspects of opportunistic spectrum access (OSA) is presented, and the three basic components of OSA are discussed.
Abstract: Compounding the confusion is the use of the broad term cognitive radio as a synonym for dynamic spectrum access. As an initial attempt at unifying the terminology, the taxonomy of dynamic spectrum access is provided. In this article, an overview of challenges and recent developments in both technological and regulatory aspects of opportunistic spectrum access (OSA). The three basic components of OSA are discussed. Spectrum opportunity identification is crucial to OSA in order to achieve nonintrusive communication. The basic functions of the opportunity identification module are identified

2,819 citations

Journal ArticleDOI
24 Apr 2009
TL;DR: This information-theoretic survey provides guidelines for the spectral efficiency gains possible through cognitive radios, as well as practical design ideas to mitigate the coexistence challenges in today's crowded spectrum.
Abstract: Cognitive radios hold tremendous promise for increasing spectral efficiency in wireless systems. This paper surveys the fundamental capacity limits and associated transmission techniques for different wireless network design paradigms based on this promising technology. These paradigms are unified by the definition of a cognitive radio as an intelligent wireless communication device that exploits side information about its environment to improve spectrum utilization. This side information typically comprises knowledge about the activity, channels, codebooks, and/or messages of other nodes with which the cognitive node shares the spectrum. Based on the nature of the available side information as well as a priori rules about spectrum usage, cognitive radio systems seek to underlay, overlay, or interweave the cognitive radios' signals with the transmissions of noncognitive nodes. We provide a comprehensive summary of the known capacity characterizations in terms of upper and lower bounds for each of these three approaches. The increase in system degrees of freedom obtained through cognitive radios is also illuminated. This information-theoretic survey provides guidelines for the spectral efficiency gains possible through cognitive radios, as well as practical design ideas to mitigate the coexistence challenges in today's crowded spectrum.

2,516 citations