• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9C
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• pp.922-927
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• 2009

Utilization problem of the limited spectrum is the one of the most important issues in wireless communication systems. Cognitive radio technique which is finding and utilizing frequency holes is also one of those techniques. Specially, the spectrum sensing technique to detect the primary user signal is a core technology in cognitive radio area. In this paper, we propose the spectrum sensing algorithm using Bussgang theorem. The proposed algorithm calculates the statistical difference between the Gaussian noise and the primary user signal by applying Bussgang theorem to the received signal. The algorithm is not affected by noise uncertainty and can detect the primary user signal in the very low SNR environment. We evaluate the algorithm through computer simulations with 12 ATSC A/74 DTV signal captures based on IEEE 802.22 WRAN and formulate the sensing threshold for the proposed scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.6
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• pp.759-767
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• 2020

This paper proposes a new Recurrent neural network (RNN) based spectrum sensing technique for cognitive radio communications. The proposed technique determines the existence of primary user's signal without any prior information of the primary users. The method performs high-speed sampling by considering the whole sensing bandwidth and then converts the signal into frequency spectrum via fast Fourier transform (FFT). This spectrum signal is cut in sensing channel bandwidth and entered into the RNN to determine the channel vacancy. The performance of the proposed technique is verified through computer simulations. According to the results, the proposed one is superior to more than 2 [dB] than the existing threshold-based technique and has similar performance to that of the existing Convolutional neural network (CNN) based method. In addition, experiments are carried out in indoor environments and the results show that the proposed technique performs more than 4 [dB] better than both the conventional threshold-based and the CNN based methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.356-368
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• 2011

While most of the public radio spectrum bands are allocated to licensed users, cognitive radio has been considered as a promising technology for the efficient spectrum utilization. In this new technology, secondary users opportunistically use the temporally underutilized licensed bands as long as they do not give the harmful interference to primary users. In this paper, we focus on the infra-structured network condition in which the cognitive radio network consists of a cognitive radio base station and multiple secondary users. Upon detecting a primary user, the entire cognitive radio network generally switches to another available channel, even if most of the on-going communications still does not interfere with the primary user. Moreover, the network re-entry process on a new channel causes the service disruption of the on-going communications. For this reason, in this paper, we propose a relaying scheme for efficient frequency usage, in which the secondary user out of the interference range of a primary user performs as a relaying node for the secondary user possibly interfering with a primary user. The entire spectrum switching is not required, and thus, we can avoid the service disruption of the on-going communications as much as possible.

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.91-99
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• 2015

The Korean Solar Radio Burst Locator (KSRBL) is a solar radio spectrograph observing the broad frequency range from 0.245 to 18 GHz with the capability of locating wideband gyrosynchrotron bursts. Due to the characteristics of a spiral feed, the beam center varies in a spiral pattern with frequency, making a modulation pattern over the wideband spectrum. After a calibration process, we obtained dynamic spectra consistent with the Nobeyama Radio Polarimeter (NoRP). We compared and analyzed the locations of bursts observed by KSRBL with results from the Nobeyama Radioheliograph (NoRH) and Atmospheric Imaging Assembly (AIA). As a result, we found that the KSRBL provides the ability to locate flaring sources on the Sun within around 2'.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.697-708
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• 2016

As the needs for fast wireless communication technology in various fields, including companies, individuals, etc., grows, many research projects related to the coverage of propagation are being carried out for plaining optimized communication services. On the other hand, there are some limitations in surveying and analyzing propagation in highland areas. To provide a better communication service of a new service, a range of radio environment conditions based on a wide radio bandwidth (selection of propagation model, correction of value in accordance with radio bandwidth, etc.) should be considered. In particular, radio environment conditions are becoming increasingly sophisticated. By the early detection of real-time changes in the radio spectrum, which is based on an examination and research of regional occupied band width condition, proper measures should be established. To make a proper solution of above, the basic real-time analysis of spectrum distribution status by regional groups is necessary. In addition, the establishment of prompt measures should be enable by stored or analyzed radio data. In an attempt to predict reliable propagation coverage, this thesis examines the limited propagation data with HTZ Warfare, which were collected from domestic high land sites faced with limited access. Furthermore, a comparative result value evaluation for an optimized propagation model was performed through testing simulations, and frequency-dependent and propagation model-dependent analysis.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.32-36
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• 2012

In this paper, we present a novel algorithm for detecting a bonded channel in a cognitive radio network where channel bonding is allowed for a higher data rate. The envelope detection algorithm is proposed to distinguish the center frequency of the received signal in order to determine whether the signal is transmitted by a primary user occupying a single channel or a secondary user occupying more than two channels when the channel is in use.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.225-230
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• 2012

The Korean nationwide differential global positioning system (NDGPS) reference station transmits a global positioning system (GPS) enhancement signal using minimum shift keying modulation with a 200 bps data rate. The ocean-based DGPS covers the service area of 100 NM with 300 W output power; on the other hand, the land-based DGPS transmits the output power of 500 W, which covers the service area of 100 km. The DGPS reference stations with high output power can radiate spurious signals, which may act as interference sources affecting the other DGPS reference stations or the wireless ground stations that utilize the medium frequency band. In this paper, the radiation spectrums of the DGPS reference stations are measured and analyzed in the spurious domain. The DGPS radiation spectrums are evaluated from the perspective of the interference effect.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.8
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• pp.1894-1912
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• 2012

This paper proposes a system called Wireless Link based on Global Communication Channel (WLGCC) to enhance the spectrum sharing between digital broadcasting (DB) services and the cognitive radio (CR) system in the licensed band of 470-790 MHz. The WLGCC aims to enhance the spectrum sensing and geolocation database (GLD) spectrum sharing methods in the CR system. Spectrum sensing can be enhanced by receiving the status of the used frequencies from the WLGCC, thereby eliminating the need for a low detection threshold (i.e., avoiding the hidden node problem). In addition, the GLD can be enhanced by providing a reliable communication link between the database and the CR device in the form of an unused TV white space that is reserved as the proposed Global Communication Channel (GCC). This paper analyzes the coexistence of the new WLGCC system and the DB service in terms of avoiding additional interference. Specifically, we mathematically determine the WLGCC parameters, such as the in-band and out-of-band power levels, and operation coverage, and verify them using Monte Carlo simulation. The results show that WLGCC does not degrade the existing DB service and reliably transmits information of the vacant (or used) frequency bands to the CR.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.2
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• pp.58-64
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• 2008

In this paper, we proposed the methodology of interference analysis based on monte-carlo method for effective use of Industrial, Scientific, Medical (ISM) band. The interference scenario is divided according to the distance and density. The simulation of interference analysis evaluates the interference probability according to distribution density of Interfering Transmitters (It) in the Secure Interference Area (SIA). The SIA is gained from the Interference Efficiency Range that satisfied to Interference Permissible Range of Victim Receiver (Vr). Simulation result that apply the proposed interference scenario to the WLAN and bluetooth, Interference Permissible Range was 60~400m. And the WLAN was acceptable within interference permissible range to six bluetooth that exist in the SIA. In the same condition, when applied Listen Before Talk (LBT) based on Cognitive Radio (CR) to the bluetooth using Frequency Hopping (FH), interference probability was decreased sharply. The Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT) that has been developed based on the monte-carlo method by European Radio-communications Office (ERO) were used to the interference simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.484-493
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• 2009

For the flexible frequency utilization, cognitive radio technique has been prominently considered. The most important requirement in cognitive radio networks is to protect the communications of primary users. Spectrum sensing task by secondary users should be seriously considered in cognitive radio networks, since the spectrum sensing process makes their current quality of service worse. In this paper, we propose the channel sensing scheduling method that keeps the requirements for protecting the primary and guarantee the secondary user's quality of service as possible. The quality of service of secondary user is analyzed in terms of packet delay and loss while the protection-requirements in terms of sensing interval and sensing time predefined. In numerical analysis, we can get appropriate parameters which guarantee QoS in various environment. And simulation results show that this method can improve the performance, delay and the number of transmitted packets against consecutive sensing method.