Huseyin Arslan

A survey of spectrum sensing algorithms for cognitive radio applications

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.

Channel estimation for wireless ofdm systems

Techniques are described for efficiently estimating and compensating for the effects of a communication channel in a multi-carrier wireless communication system. The techniques exploit the fact that the transmitted symbols are drawn from a finite-alphabet to efficiently estimate the propagation channel for multi-carrier communication systems, such systems using OFDM modulation. A transmitter transmits data through a communication channel according to the modulation format. A receiver includes a demodulator to demodulate the data and an estimator to estimate the channel based on the demodulated data. The channel estimator applies a power-law operation to the demodulated data to identify the channel. The techniques can be used in both blind and semi-blind modes of channel estimation.

Ultra-Wideband Wireless Communications

Summary Ultra-wideband (UWB) communication techniques have attracted a great interest in both academia and industry in the past few years for applications in short-range wireless mobile systems. This is due to the potential advantages of UWB transmissions such as low power, high rate, immunity to multipath propagation, less complex transceiver hardware, and low interference. However, tremendous R&D efforts are required to face various technical challenges in developing UWB wireless systems, including UWB channel characterization, transceiver design, coexistence and interworking with other narrowband wireless systems, design of the link and network layers to benefit from UWB transmission characteristics. This paper is to provide an overview of UWB communications, summarize the previous research results, and identify further research issues that need to be tackled. The emphasis is placed on the commercial wireless communications. Copyright # 2003 John Wiley & Sons, Ltd.

OFDM for cognitive radio: merits and challenges

Cognitive radio is a novel concept that enables wireless systems to sense the environment, adapt, and learn from previous experience to improve the quality of the communication. However, CR requires a flexible and adaptive physical layer in order to perform the required tasks efficiently. In this article, CR systems and their requirement of a physical layer are discussed, and the orthogonal frequency division multiplexing technique is investigated as a candidate transmission technology for CR. The challenges that arise from employing OFDM in CR systems are identified. The cognitive properties of some OFDM-based wireless standards also are discussed to indicate the trend toward a more cognitive radio.

Cognitive Radio, Software Defined Radio, and Adaptive Wireless Systems

Preface. Chapter 1: Introducing Adaptive, Aware, and Cognitive Radios Bruce Fette. Chapter 2: Cognitive Networks Ryan W. Thomas, Daniel H. Friend, Luiz A. DaSilva, Allen B. MacKenzie. Chapter 3: Cognitive Radio Architecture Joseph Mitola III. Chapter 4: Software Defined Radio Architectures for Cognitive radios H. Arslan, H. celebi. Chapter 5: Value-Creation and Migration in Adaptive and Cognitive Radio Systems Keith E. Nolan, Francis J. Mullany, Eamonn Ambrose, Linda E. Doyle. Chapter 6: Codes and Games for Dynamic Spectrum Access Yiping Xing, Harikeshwar Kushwaha, K.P. Subbalakshmi, R. Chandramouli. Chapter 7: Efficiency and Coexistence Strategies for Cognitive Radio Sai Shankar N. Chapter 8: Enabling Cognitive Radio Through Sensing, Awareness, and Measurements H. Arslan, S. yarkan. Chapter 9: Spectrum Sensing for Cognitive Radio Applications H. Arslan, T. Yucek. Chapter 10: Location Information Management Systems for Cognitive Wireless Networks H. Arslan, H. Celebi. Chapter 11: OFDM for Cognitive Radio: Merits and Challenges H. Arslan, H. A. Mahmoud, T.Yucek. Chapter 12: UWB Cognitive Radio H. Arslan, M.E. Sahin. Chapter 13: Applications of Cognitive radio H. Arslan, S. Ahmed. Chapter 14: Cross-layer Adaptation and Optimization for Cognitive Radio H. Arslan, S. Yarkan. Index.

Sidelobe suppression in OFDM-based spectrum sharing systems using adaptive symbol transition

In this letter, we introduce a new method for orthogonal frequency division multiplexing (OFDM) sidelobe suppression. An extension is added to OFDM symbols that is calculated using optimization methods to minimize adjacent channel interference (ACI) while keeping the extension power at an acceptable level. Using this technique, interference to adjacent signals is reduced significantly at the cost of a small decrease in the useful symbol energy. The proposed method can be used by cognitive radio (CR) systems to shape the spectrum of OFDM signals and to minimize interference to licensed users (LU), or to reduce the size of guard bands used in conventional OFDM systems.

A Survey on Multicarrier Communications: Prototype Filters, Lattice Structures, and Implementation Aspects

Due to their numerous advantages, communications over multicarrier schemes constitute an appealing approach for broadband wireless systems. Especially, the strong penetration of orthogonal frequency division multiplexing (OFDM) into the communications standards has triggered heavy investigation on multicarrier systems, leading to re-consideration of different approaches as an alternative to OFDM. The goal of the present survey is not only to provide a unified review of waveform design options for multicarrier schemes, but also to pave the way for the evolution of the multicarrier schemes from the current state of the art to future technologies. In particular, a generalized framework on multicarrier schemes is presented, based on what to transmit, i.e., symbols, how to transmit, i.e., filters, and where/when to transmit, i.e., lattice. Capitalizing on this framework, different variations of orthogonal, bi-orthogonal, and non-orthogonal multicarrier schemes are discussed. In addition, filter designs for various multicarrier systems are reviewed considering four different design perspectives: energy concentration, rapid decay, spectrum nulling, and channel/hardware characteristics. Subsequently, evaluation tools which may be used to compare different filters in multicarrier schemes are studied. Finally, multicarrier schemes are evaluated from the perspective of practical implementation aspects, such as lattice adaptation, equalization, synchronization, multiple antennas, and hardware impairments.

Spectrum Characterization for Opportunistic Cognitive Radio Systems

Spectrum sensing is one of the most challenging problems in cognitive radio systems. The spectrum of interest needs to be characterized and unused frequencies should be identified for possible exploitation. This process, however, should be computationally simple and fast in order to catch up with the changing transmission parameters. This paper proposes a sensing method for identifying the unused spectrum for opportunistic transmission by estimating the RF transmission parameters of primary users. The primary users are identified by matching the a priory information about their transmission characteristics to the features extracted from the received signal. The application of the proposed sensing method to WiMAX mobile stations for finding the active channels during initial network entry is also discussed as a case study

Utilization of Location Information in Cognitive Wireless Networks

Location awareness is an essential characteristic of cognitive radios as well as networks. In this article a location awareness engine architecture is proposed for the realization of location awareness in cognitive radios and networks. The proposed architecture consists of location estimation and/or sensing, seamless positioning and interoperability, statistical learning and tracking, security and privacy, mobility management, and location-based applications. However, the focus of this article is on location-based applications where we demonstrate the utilization of location information in cognitive wireless networks by presenting some representative location-assisted network optimization applications such as location-assisted spectrum management, network planning and expansion, and handover. Our study unveils that location information can be used in cognitive wireless networks to optimize network performance. Possible solutions to the implementation issues are proposed, and the remaining open issues are also addressed.

Binary Time Series Approach to Spectrum Prediction for Cognitive Radio

One of the major goals of cognitive radio (CR) is to alleviate the inefficient use of the spectrum. CR can sense the spectrum steadily and gather information about the evolution of the spectrum in time. Spectrum occupancy information can be used for both learning the usage of the spectrum and predicting the future occupancy status. In this study, the use of binary time series for spectrum occupancy characterization and prediction is proposed. Both deterministic and non-deterministic occupancy schemes are examined. Numerical results and discussions are presented.