Guanbo Zheng

Weighted-Collaborative Spectrum Sensing in Cognitive Radio

Cognitive radio is an advanced enabling technology for efficient utilization of under-utilized spectrum since it is able to sense the spectrum and use the frequency when the primary users are absent. Recent investigation suggests that spectrum sensing is compromised when a user experiences fading or shadowing. In order to combat such effects, collaborative sensing is presented. However, the conventional collaborative sensing is not effective when users suffer from different fading environments. In this paper, we propose a weighted-collaborative scheme to improve the spectrum sensing performance under fading environment. The analysis of the simulation results proves that the weighted-collaborative scheme improves sensing performance obviously.

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.

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.

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.

A Cognitive UWB Testbed Employing Adaptive Pulse Generation

Ultra wideband (UWB) is an promising underlying method for coexistence among different systems. However, the performance may not be as good as expected due to the changing spectrum environment. Thus, cognitive UWB radio is proposed by taking the advantage of cognition, which enables the radio to learn the spectrum environment by itself. In this paper, we explore a cognitive UWB testbed in physical layer, including cognitive pulse generator, stream view and performance evaluation. In order to protect the potential narrowband systems, the specific mask and channel information are utilized to adapt the system parameters with the help of pulse mask code and pulse generation block. Simulation results show that the proposed testbed is capable to generate the adaptive pulse that suitable for different spectrum environment.

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.