• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3731-3750
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• 2014

This paper considers a wideband cognitive radio network (WCRN) which can simultaneously sense multiple narrowband channels and thus aggregate the detected available channels for transmission and studies the ergodic throughput of the WCRN that operated under: the wideband sensing-based spectrum sharing (WSSS) scheme and the wideband opportunistic spectrum access (WOSA) scheme. In our analysis, besides the average interference power constraint at PU, the average transmit power constraint of SU is also considered for the two schemes and a novel cognitive radio sensing frame that allows data transmission and spectrum sensing at the same time is utilized, and then the maximization throughput problem is solved by developing a gradient projection method. Finally, numerical simulations are presented to verify the performance of the two proposed schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.68-78
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• 2013

In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.

• Journal of Broadcast Engineering
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• v.21 no.1
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• pp.113-116
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• 2016

Cognitive radio network technology is that secondary (unlicensed) users use the spectrum of primary (licensed) users without interfering primary communication. In this paper, we propose multiple access scheme for a cognitive radio network, where multiple secondary users access spectrum of one primary user. We consider two types of multiple access scheme, one is p-persistent and one is non-persistent, and apply these two schemes in the secondary network. For each multiple access scheme, total throughput of secondary network is derived and verified by Monte Carlo simulation. Simulation results show that maximum total throughput of the secondary network is achieved when channel access probability or the number of maximum waiting frames is chosen appropriately.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.550-552
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• 2004

In this paper, access protocol is proposed that can optimally control the radio buoy system used for inshore and deep sea fishery. Proposed protocol can minimize the power consumption of radio buoy and can ensure high security from burglary and loss, and it enable a mother ship to control remotely more than 150 radio buoys simultaneously. GPS technology and remote control techniques are used to monitor the exact location and status of the radio buoy system in real time.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.112-122
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• 2016

Cognitive radio (CR) is considered an attractive technology to deal with the spectrum scarcity problem. Multi-radio access technology (multi-RAT) can improve network capacity because data are transmitted by multiple RANs (radio access networks) concurrently. Thus, multi-RAT embedded in a cognitive radio network (CRN) is a promising paradigm for developing spectrum efficiency and network capacity in future wireless networks. In this study, we consider a new CRN model in which the primary user networks consist of heterogeneous primary users (PUs). Specifically, we focus on the energy-efficient resource allocation (EERA) problem for CR users with a special location coverage overlapping region in which heterogeneous PUs operate simultaneously via multi-RAT. We propose a two-tier crossover genetic algorithm-based search scheme to obtain an optimal solution in terms of the power and bandwidth. In addition, we introduce a radio environment map to manage the resource allocation and network synchronization. The simulation results show the proposed algorithm is stable and has faster convergence. Our proposal can significantly increase the energy efficiency.

• ETRI Journal
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• v.34 no.2
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• pp.276-279
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• 2012

In this letter, a modified 802.11-based opportunistic spectrum access is proposed for single-channel cognitive radio networks where primary users operate on a slot-by-slot basis. In our opportunistic spectrum access, control frames are used to reduce the slot-boundary impact and achieve channel reservation to improve throughput of secondary users. An absorbing Markov chain model is used to analyze the throughput of secondary users. Simulation results show that the analysis accurately predicts the saturation throughput.

• The Journal of Information Technology
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• v.4 no.3
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• pp.65-75
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• 2001

Code-division multiple access has been widely accepted as the major multiple access scheme in mobile communication systems. Wide-band CDMA and its hybrid associate time-division CDMA are key elements in the mobile communication. Since 10 years ago, there has been enormous research activity in analysis of the capacity of these CDMA-based systems. Recently, upgrading service, high quality and the different service classes in radio resource allocation has recently increased. This paper presents an overview of Radio Resource Allocation on the CDMA-based systems that are flexible, support traffic services, minimize call blocking rate and have acceptable radio resource utilization.

• Journal of Broadcast Engineering
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• v.19 no.1
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• pp.14-23
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• 2014

This paper proposed controlling methods for SDN(Software Defined Network) based multiple radio access technology as the solutions of following two issues which were mainly occurred by explosive increasing of video traffic. The first one is a requirement for traffic off-loading caused by 3rd-party video service providers from the mobile network operator's viewpoint. The other one is a provision of high-speed video contents transmission services with low price. Furthermore, the performance evaluation was also conducted on the real test-bed which is composed of OpenStack cloud and SDN technology such as OpenFlow and Open vSwitch. A virtual machine running on the OpenStack provide a video service and the terminal which is able to use multiple radio access technology supports two 2.4GHz WLANs(Wireless Local Area Network) and three 5GHz WLANs, concurrently. Finally, we can get 820Mbps of the maximum transmission speed by using that five WLAN links for the single service at the same time.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.6
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• pp.553-560
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• 2016

There propagate use management paradigm in developed countries is changing as Command & Control $\Rightarrow$ Market Based $\Rightarrow$ Open Access $\Rightarrow$ Manage By Technology & Technical Analysis, that the policy response to environmental changes, such as a variety of new technologies. The emergence of service, the proliferation of propagation users It is to activate the market. However, the basic principles of radio management such that the change of paradigm be used to spread in a range that does not affect the interference, such as the horn is to be observed. Around the world in order to prevent the propagation and utilization Horn interference enacted regulations for managing the radio station, and also discipline.

• The Journal of Korean Institute of Information Technology
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• v.17 no.2
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• pp.71-77
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• 2019

With 5G standards proceeding in earnest and increasing demand for services of indoor localization, research on indoor location recognition is being studied in various industrial fields, and research based on fingerprint recognition technology using Wireless Local Area Network (WLAN) is representative. In this paper, we propose an indoor positioning system based on fingerprinting technique that uses Cloud Radio Access Network (C-RAN) architecture and Channel State Information (CSI). In order to improve the performance in indoor positioning, we combined existing fingerprinting method and K nearest neighbor (KNN) technology which is one of the machine running technique. The performance improvements of the proposed indoor positioning system was verified by comparative experiments with the existing localization technique in a indoor localizztion testbed.