Sung Hwan Sohn

An Alternative Energy Detection Using Sliding Window for Cognitive Radio System

Cognitive radio is one of the most effective techniques to improve the spectrum utilization efficiency. To implement the cognitive radio, spectrum sensing is considered as the key functionality because secondary users should identify the spectrum holes and utilize them efficiently without causing interference to primary users. In generally, there are three major spectrum sensing methods, including matched filter, energy detection and feature detection. The most common and simplest method is energy detection. However, the conventional energy detection suffers from large degradation in performance under low SNR environment. In this paper, we proposed alternative energy detection which can estimate the exact power of primary user without the noise effect and lead to the better performance. In order to reduce the effect of noise fluctuation, the sliding window function is utilized to assist the proposed detector. The simulation result shows that our proposed method outperform conventional one.

OFDM Signal Sensing Method Based on Cyclostationary Detection

Cognitive Radio is an advanced enabling technology for efficient utilization of vacant spectrum due to its ability to sense the spectrum environment. Various detection methods have been proposed for spectrum sensing, which is the key function in implementing cognitive radio. Most of the existing methods put their interests in detecting TV signal and wireless microphone signals. In this paper, we explore the cyclostationarity of the equally spaced pilot subcarriers in OFDM signal. By averaging over several symbols, the peak property is able to be captured. Simulations in various fading environments show that the proposed cyclostationary based detection method works well for OFDM signal.

Cognitive Radio Software Testbed using Dual Optimization in Genetic Algorithm

Cognitive Radio is considered as a potential solution to improve spectrum utilization via opportunistic spectrum sharing. In this paper, we present a software testbed which is developed to implement the cognitive radio system. The basic functions of cognitive radio are explored and implemented, including spectrum sensing and dynamic spectrum management. The testbed is able to verify the overall performance of cognitive radio technology. Furthermore, it provides an important system model to verify the effectiveness of the new algorithms in future study. The simulation on the testbed demonstrates that primary and secondary users can coexist. This is able to convince regulatory authorities as well as primary users to enable the implementation of cognitive radio technology.

Enhanced Energy Detector for IEEE 802.22 WRAN Systems Using Maximal-to-Mean Power Ratio

Spectrum sensing is the key function in implementing cognitive radio, which enables secondary users to identify and utilize vacant spectrum resource allocated to primary users. Recent studies have proposed three major sensing methods for WRAN systems, including matched filter, energy and feature detector. However, there are some drawbacks along with them. In this paper, we propose an enhanced energy detector that extends the ability of conventional one to differentiate the primary user from the other as well as the noise with maximum- to-mean power ratio. A novel structure of cognitive radio detector employing the proposed algorithm is also presented to implement spectrum sensing. The simulation result shows that our proposed scheme performs well in the individual sensing environment and can satisfy the requirement with high detection probability.

DFS algorithm with ranking based on Genetic Algorithm in UHF portable system

Cognitive radio(CR) is a potential technology for efficient utilization of under-utilized spectrum via spectrum sensing. CR users should move from current allocating channel to empty channel to avoid the interference to the primary user if the primary user is allocated that channel. Thus, CR system cannot support the CR users QoS(Quality of Service). In this paper, we propose a dynamic frequency selection method based on Genetic Algorithm(GA) with ranking in UHF personal/portable system, which is to find the optimization channel for satisfying various CR users needs such as throughput maximization and interference minimization. And, we propose the GA which determines the best configuration for CR communication systems. The computer simulation results show that the proposed method guaranteed the primary users optimized solution for various channel status.

Analysis of opportunistic access in the spectrum sharing system with heterogeneous secondary users

For the purpose of increasing the utilization efficiency of spectrum, secondary usage method of the licensed spectrum has been explored. In this paper, based on the concept of spectrum pooling, we propose a spectrum sharing system with opportunistic accesses. In order to satisfy with the realistic applications, we define heterogeneous secondary users (non-real-time and real-time services) with different quality-of-service (QoS) requirements in our system model. Since each primary userpsilas requiring channel may be occupied by different types of secondary user, the primary user uses different schemes to solve the collision. Numerical results show that our model can obtain a better tradeoff between increasing the spectrum utilization and guaranteeing the primary userpsilas access priority.

Pilot Periodicity Based OFDM Signal Detection Method for Cognitive Radio System

Cognitive Radio is an advanced enabling technology for efficient utilization of vacant spectrum due to its ability to sense the spectrum environment. Various detection methods have been proposed for spectrum sensing, which is the key function in implementing cognitive radio. However most of the existing methods put their interests in detecting TV signal and wireless microphone signals. In this paper, we explore the periodicity of the equally spaced pilot subcarriers in OFDM signal. Simulations in various fading environments show that the proposed cyclostationarity based detection method works well for OFDM signal.

Hybrid UWB Multi-Piconet Network Interference Modeling and Performance Enhancement by 6-Bands MB-OFDM

UWB (ultra-wide band) system that utilizes the unlicensed 3.1 - 10.6 GHz UWB band, as regulated in the United States by the Federal Communications Commission (FCC) Regulations, and there is a trend that UWB and Bluetooth technology are combined together for developing a next-generation low-power, low-cost ad hoc networking solution that will expand Bluetooth technologys current success. In this paper, we propose a novel piconet system model in which Bluetooth topology and MB-OFDM UWB devices are combined together to form a new ad hoc piconet system. For our proposed system, first, we used Bluetooth piconets topology as reference to construct our proposed systems topology, considering both the path-loss effect and the using of TFC code to model our proposed schemes inter-piconet interference. Second, we use the BER graph to evaluate our proposed systems performance taking into account of the Inter-piconet Interference influence, furthermore, we propose a 6-Bands MB-OFDM model to enhance our networks BER performance. Definitely, our model can be considered to provide a solid foundation for future interference aware UWB-Bluetooth protocols.

Chaotic Characteristic Based Sensing for Cognitive Radio

Chaotic phenomena are ubiquitous and widely existing. Signal detection based on chaotic characteristic has been a hot topic all along. In the mean time, Cognitive Radio also depicts a promising future for us. In this paper, for the first time signal sensing based on chaos is discussed. And the intriguing problems are also analyzed. Finally the simulation results verify that the sensing based on chaotic characteristic is prevailing to the current sensing method based on entropy.

Cognitive Radio in Multiple-Antenna Systems

This chapter presents an overview of the techniques used in a multiple-antenna 1 system and discusses the key issues in introducing cognitive radio (CR) technology. This discussion is followed by an explanation of the applications of the new system, which combines CR and multiple-antenna (MA) techniques. This chapter discusses the issues that combine the MA system with CR technology to increase the utilization of spectrum by sharing the spectrum among different systems as well as to improve the transmission efficiency by selecting the optimum transmission schemes under certain operational environments. It introduces the new functionalities, namely, radio environment observation and cognitive engine, in the MA system by adding cognitive capability. In such a system, besides signal detection and identification, the DOA and antenna correlation information should be obtained with the help of multiple antennas. By combining the environmental information, CE is able to select an optimum operation mode for the radio, depending on the related position between the primary units (PUs) and secondary units (SUs).