• ETRI Journal
• /
• v.36 no.3
• /
• pp.502-505
• /
• 2014

Polarized spectrum sharing (PSS) exploits the spectrum opportunities in a polarized domain. However, when it comes to wideband environments PSS is impaired by the frequency-dependent polarization mode dispersion (PMD); thus, the effective throughput of PSS drops. To combat the PMD effect, this work proposes a cluster-based PSS approach to enable PSS on a narrower frequency span. Simulation results show that the effective throughput of PSS on cluster basis outperforms that of PSS on bandwidth and subcarrier basis.

• Journal of Communications and Networks
• /
• v.11 no.2
• /
• pp.104-114
• /
• 2009

In this paper, a technique is proposed that enables secondary users to evaluate channel availability in cognitive radio networks. Here, secondary users estimate the utilization of channels via predicting the traffic pattern of primary user, and select a proper channel for radio transmission. The proposed technique reduces the channel switching rate of secondary users (the rate of switching from one channel to another) and the interference on primary users, while maintaining a reasonable call blocking rate of secondary users.

• Information and Communications Magazine
• /
• v.30 no.12
• /
• pp.90-96
• /
• 2013

본고에서는 신규 통신사업자가 펨토셀 시장에 진입할 것인지 여부와 진입한다면 어떤 펨토셀 공유 기술(Spectrum Sharing Scheme)을 선택할 것인지를 장기적인 문제로 분석한다. 그리고 이와 관련된 신규 사업자의 가격 결정 전략과 사용자의 펨토셀 통신 서비스 가입 결정을 각각 중기, 단기적인 문제로 분석한다. 신규 사업자가 펨토셀 시장에 진입하여 독점사업자로 운영하는 경우와 기존의 통신사업자와 복점으로 경쟁하는 경우를 고려하고, 각 시나리오에서 이윤을 극대화하고자 하는 신규 통신사업자의 최적 의사결정에 대해 논한다.

• Journal of Advanced Navigation Technology
• /
• v.23 no.6
• /
• pp.507-514
• /
• 2019

Federal communications commissions (FCC) has announced the first set of rules for 3.5 GHz (3,550 - 3,700 MHz) band used Navy radar and fixed satellite service (FSS) earth stations as primary service to sharing for citizen broadband radio service (CBRS) enable development of relatively low powered network technologies like small cells. Since CBRS sharing technique based on the 3-tiered spectrum access system (SAS) is able to protect the higher tiered users from harmful interference from lower tiered users, it has been considered actively to be introduced in Korea. However, 3.5 GHz band had been already allocated to the 5G services in Korea, the sharing studies have been carried out for 3,700 - 5,000 MHz, As the result, the 3.8 GHz (3,800 - 3,900 MHz) band used for only FSS system is able to be sharing, and an introduction of CBRS has been proposed in Korea by analyzing the interference to the FSS earth stations.

• East Asian mathematical journal
• /
• v.27 no.1
• /
• pp.23-33
• /
• 2011

Due to underutilization of spectrum under current inefficient and static spectrum management policy, various kinds of opportunistic spectrum access (OSA) strategies have appeared. Myopic policy is a simple and robust OSA strategy with reduced complexity that maximizes immediate throughput. In this paper, we propose mathematical models to evaluate the throughput and the MAC delay of a myopic policy under saturation tra c conditions. Using the MAC delay distribution, we evaluate the packet delay of secondary users under nonsaturation conditions. Numerical results are given to show the performance of the myopic policy in cognitive radio networks.

• Journal of Advanced Navigation Technology
• /
• v.16 no.2
• /
• pp.219-226
• /
• 2012

Since OFDM(Orthogonal Frequency Division Multiplexing) technology is applied into LTE(Long Term Evolution)/LTE-Advanced system, it is important to estimate the spectrum sharing and to analyze interference in LTE system based on the characteristics of frequency assignment. Therefore, in this paper, a study on the adjacent channel interference between two operators/systems to provide LTE services. For co-existence of LTE systems, the relative capacity loss and the relative throughput loss in uplink and downlink have been simulated to evaluated ACIR(Adjacent Channel Interference Ratio) values with 5% loss rate. Some parameters such as the location of user, aggressor bandwidth, and the separation offset affect the required ACIR value for spectrum sharing, and these results and interference analysis schemes in this article can provide reliable reference for LTE RF standardization and efficient frequency utilization in future.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.1
• /
• pp.105-110
• /
• 2015

In cognitive radio networks, when the signal-to-noise ratio (SNR) of the link between a primary transmitter and receiver is sufficiently high, the primary transmission does not frequently demand cooperation because direct transmission of the primary communication is usually successful. Therefore, there are few opportunities for a secondary transmitter to cooperate with the primary user system in exchange for an opportunity to share the spectrum. This article proposes a scheme in which the secondary system can deliberately degrade the SNR of the primary transmission, making it so that the primary system needs cooperation from the secondary nodes, and thereby increases opportunities for spectrum sharing.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.10
• /
• pp.1005-1019
• /
• 2014

In this paper, we proposed the frequency candidates band for the spectrum sharing through researching and analyzing the current status of the policy and the economic values which is actively conducted on the United States and Europe. To this end, we investigated to the status and problems with the frequency reallocation and arrangement in respond to the current frequency demand. To solve these frequency reallocation and arrangement method problems, we introduce to the concept and current status of policy for the frequency method progress by advanced countries mainly. Also the results of the economic value analysis introduced in terms of the operators. In addition, we proposed the assessment terms and criteria for the selection of frequency candidates band through joint research and analysis results.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.3
• /
• pp.1333-1343
• /
• 2016

Spectrum sharing in centrally controlled cognitive radio (CR) networks has been widely studied, however, research on channel access for distributively controlled individual cognitive users has not been fully characterized. This paper conducts an analysis of random channel access of cognitive users controlled in a distributed manner in a CR network. Based on the proposed estimation method, each cognitive user can estimate the current channel condition by using its own Markov-chain model and can compute its own blocking probability, collision probability, and forced termination probability. Using the proposed scheme, CR with distributed control (CR-DC), CR devices can make self-controlled decisions based on the status estimations to adaptively control its system parameters to communicate better.

• ETRI Journal
• /
• v.44 no.4
• /
• pp.531-542
• /
• 2022

With the increasing demand for unlicensed spectrum, several regulators have been opening up the 6-GHz band for unlicensed use while ensuring compliance with the technical requirement to avoid harmful interference in the existing primary services (PSs). In this paper, we present two methodologies, a channel-based method and a frequency-based method, which are applicable to a frequency coordination system that calculates the permissible transmit power in the channels or frequencies available to a secondary service (SS). In addition, we have demonstrated that the available transmit power of an SS can be maximized by adjusting the power allocation of the assigned resource units under the condition that the channel of the SS is partially overlapped with that of the PS. Based on the analysis results, it is suggested that it would be better to utilize the two methods selectively according to the operating channel conditions of the PS and the SS.