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This paper deals with an adaptive multiuser detector for DS-CDMA (Direct Sequence Code Division Multiple Access) wireless communication systems, whose main features are low complexity and joint utilization of the time diversity and blind adaptive processing techniques. The proposed multiuser detector, defined as Pre-combining Advanced Blind Adaptive Multiuser Detector (PABA-MUD), a window reprocessing...
The classical energy detection (CED) system is a well known technique for spectrum sensing in cognitive radio. Generalized p-norm detector for spectrum sensing in additive white Gaussian noise (AWGN) has been shown to provide improved performance over CED under certain conditions. Further, improved algorithm exists which works better than the classical energy detection algorithm. The present paper...
In this paper, the problem of cooperative spectrum sensing of cyclostationary signals for cognitive radios is considered. It has been shown that the MMSE optimal filters for cyclostationary signals involve one or more frequency shift branches and are called FRESH (FREquency SHift) filters. Adaptive FRESH filters have been used in the past to enhance cyclostationary signals so as to ease their detection...
This work is devoted to the analysis of the performance of energy detection based spectrum sensing in the presence of enriched fading conditions which are distinct for the large number of multipath components and the lack of a dominant components. This type of fading conditions are characterized efficiently by the well known Nakagami-q or Hoyt distribution and the proposed analysis is carried out...
In the present article, the cooperative spectrum sensing with a weighted fusion (WCSS) scheme has been analyzed in Rayleigh fading. Cognitive radio (CR) uses an improved energy detector (IED) with several antennas. Antenna selection diversity combining (SC) is performed at each CR on the basis of the values of decision statistics measured from different antennas at IED. Every CR takes 1-bit decision...
This paper estimates bounds on the capacity of Nakagami-m fading massive multiple-input multiple-output (MIMO) channels with large number of antennas at the transmitter and receiver. We consider two models namely conventional co-located MIMO (C-MIMO) and distributed MIMO (D-MIMO) models. At first, we derive the achievable rate for the C-MIMO and D-MIMO systems. Secondly, we use maximum ratio combining...
We present in this paper a partial coherent receiver for detecting (at the relay) the modulo-2 sum bit of the uplink orthogonal modulations in a two-way relay communication system with physical network coding and fading. The detector exploits the availability of implicit pilot symbols in every signaling interval of an orthogonal modulation and is able to provide reasonably accurate data recovery without...
We present the results of an extensive, high spatial density measurement campaign made for investigating the shadowing correlations on two different frequency bands, namely 485MHz and 2600MHz in an urban propagation environment. In particular, we report results using different analysis procedures and tools. Our results show that the signal detector has only a small impact on the extracted data, given...
The paper investigates the performance of the energy detector in fading environments under the constraint, that each sensor has only a limited dynamic range. First, the effects which limit the dynamic of a sensor node are discussed before the influence on the energy detector is analyzed. Simulations are presented how cooperative spectrum sensing affects the detection probability and it is shown that...
In this paper, we consider adaptive quadratic amplitude modulation (QAM) for a cooperative network consists of a source, one decode-and-forward (DF) relay and a destination which are single antenna systems. For increasing the spectral efficiency of the system, we use adaptive modulation method for data transmission. We propose a new adaptive modulation scheme which has less complexity than available...
Cognitive Radio (CR) is a novel promising approach proposed to ensure efficient spectrum utilization. It is the obvious solution to the spectral congestion problem. Spectrum sensing is the most essential functionality required for the practical implementation of cognitive radio networks. An efficient spectrum sensing method must detect very weak primary user signals while being sufficiently fast and...
Energy detectors are preferred choice for spectrum sensing in cognitive radio networks due to their low implementation complexity. Recently, there is a lot of work being done to analyze the energy detectors in both diversity and cooperative relay networks. In this work, detection performance of energy detector is analyzed in a fixed-gain cooperative relay network with maximum-ratio combiner (MRC)...
Frequency-selective fading channels are encountered in many modern wireless communication systems. In order to combat the intersymbol interference (ISI) introduced by such fading, equalization is required for reliable symbol detection. The maximum-likelihood sequence detector is the optimal equalization scheme; however its implementation complexity increases exponentially with the channel length and...
This paper presents a cooperative spectrum sensing scheme for cognitive radio based on the FFT energy detection. The proposed cooperative sensing scheme utilizes the cross correlation between the output of the sensor of interest and composite output of other sensors. Simulation results show that the proposed cooperative sensing scheme is superior to conventional cooperative sensing using frequency...
In cognitive radio network (CRN), traditional energy detection algorithm has a bad detection performance in fading and shadowing environment. So cooperative spectrum sensing among cognitive radio nodes is needed in order to overcome these drawbacks. However it will result in a large demand of communication bandwidth on the control channel when the number of nodes is great. To solve this problem, this...
In this paper we propose a computationally efficient detector for an M-aray Phase Shift Keying (MPSK) signal over fast fading channel with unknown parameters in a Single-Input-Multiple-Output (SIMO) scenario for cognitive radio applications. Employing Basis Expansion Model (BEM) as a usual approach for modeling such environments, we derive the Generalized Likelihood Ratio (GLR) Detector. However,...
In this paper a new spectrum sensing technique for multiple antenna cognitive radio network is proposed. While a large majority of the existing literature assume that the signal is corrupted by additive white Gaussian noise, this assumption is not always true in practice. In the present work, slow Rayleigh fading channel in the presence of impulsive noise is considered and BPSK modulation is employed...
Cognitive radio is a novel technology that is provision to overcome the spectrum scarcity problem in wireless networks. Cognitive radio network is founded to provide the capability of sharing the wireless channel between unlicensed users (secondary users) and licensed users (primary users) in an opportunistic manner. Primary user detection in low signal to noise ratio (SNR) regime is one of the main...
Recent studies have shown that, while the available licensed radio spectrum becomes more occupied, the assigned spectrum is significantly underutilized. To alleviate the situation, cognitive radio (CR) technology has been proposed to provide an opportunistic access to the licensed spectrum areas. CR systems are able to serve the secondary users for detecting and utilizing so called spectrum holes...
In this study we analyze the performance of a class of detectors for deterministic signals with unknown amplitudes. We derive the test statistic and evaluate the performance in AWGN and some fading channels. The results help to give a better insight into the effect of number of recieved samples for the detector and its general performance. We compare our results to the classic energy detector and...
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