• Journal of Communications and Networks
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• v.12 no.4
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• pp.308-316
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• 2010

The problem of compressed sensing (CS) based multiple access is studied under the assumption of random data traffic. In many multiple access systems, i.e., wireless sensor networks (WSNs), data arrival is random due to the bursty data traffic for every transmitter. Following the recently developed CS methodology, the technique of compressing the transmitter identities into data transmissions is proposed, such that it is unnecessary for a transmitter to inform the base station its identity and its request to transmit. The proposed compressed multiple access scheme identifies transmitters and recovers data symbols jointly. Numerical simulations demonstrate that, compared with traditional multiple access approaches like carrier sense multiple access (CSMA), the proposed CS based scheme achieves better expectation and variance of packet delays when the traffic load is not too small.

• International Journal of Knowledge Content Development & Technology
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• v.6 no.1
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• pp.69-84
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• 2016

The paper investigates open access (OA) self archiving policies of different Open Access Repositories (OARs) of COAPI (Coalition of Open Access Policy Institutions) founder members as reported in June 2011 (i.e. a total of 22 members against a total of 46 COPAI members as reported by Open Biomed (http://openbiomed.info/2011/08/coapi-cats/). The paper consulted three databases (OpenDOAR, ROAR and ROARMAP) in order to evaluate twenty-two (22) COAPI-members OARs self archiving policy documentations and highlights of some progress on issues so far. After analyzing policy documentations, key findings have been highlighted and common practices have been suggested in line with global recommendations and best practice guidelines at national and international levels for strengthening national research systems. The paper has implications for administrators, funding agencies, policy makers and professional librarians in devising institute specific self archiving policies for their own organization.

• Journal of Korean Society of Transportation
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• v.4 no.1
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• pp.28-40
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• 1986

Accurate subway demand estimation which is essential for better route selection can be achieved by the exact definition of the influence sphere of subway station. The influence was derived implicitly from the analysis of access time to the station for the cases of Seoul. Access time distribution was investigated by trip purposes, by age, by income, by sex, by travel distance, by kinds of thickets, by the location of station for the analysis of relationship between access time and socio-economic characteristics or urban structure. The difference of average access time between direct access trip and transfer trip which is found 8.6 minutes and 6.1 minutes respectively also investigated. The small difference implies poor transfer system of Seoul subway. 83.1% of subway users are coming from the distance of 10minutes' walk and average access time is 7.8minutes as a whole.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9B
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• pp.596-601
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• 2005

In this paper it is focused on the relation between CLR(Cell Loss Ratio) and blocking probability in the wireless ATM access transport. Traffic model of wireless ATH access transport is based on the cell scale, burst scale and call connection level. The CLR due to buffer overflow for wireless access node is derived for VBR traffic. The CLR due to transmission errors for wireless channel is derived. Using the CLR for both access node and wireless channel: the CLR of wireless ATM access transport is derived. The relation between CLR and blocking probability is analyzed for VBR traffic to evaluate performance of wireless ATM access transport.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5497-5512
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• 2016

An improved optimal weights based on parallel interference cancellation algorithm has been proposed to cancel for interference induced by multi-user access satellite to ground uplink system. Due to differences in elevation relative motion between the user and the satellite, as well as access between users, resulting in multi-user access interference (Multi-user Access Interference, MUI), which significantly degrade system performance when multi-user access. By steepest gradient method, it obtained based on the MMSE criterion, parallel interference cancellation adjust optimal weights to obtain the maximum SINR. Compared to traditional parallel interference cancellation (Parallel Interference Cancellation, PIC) algorithm or serial interference cancellation ( Successive interference Cancellation, SIC), the accuracy of which is not high and too many complex iterations, we establish the multi-user access to the satellite to ground up link system to demonstrate that the improved WPIC algorithm could be provided with high accuracy and relatively low number of iterations.

• Journal of the Institute of Convergence Signal Processing
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• v.13 no.3
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• pp.156-161
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• 2012

Random access protocol takes advantage of constructing a decentralized wireless network due to its intrinsic spectrum sensing capability. Such technical feature goes well with cognitive radio networks consisting of heterogeneous wireless systems, in which a centralized control between heterogeneous wireless systems is hard to be implemented. Motivated by the decentralized feature of the random access, we adopt the random access protocol in cognitive radio networks, and evaluate the performance of a CSMA-based cognitive radio network.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.2047-2050
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• 2002

At present, many applications independently provide access control for their own resources, for example Web, Databases and Operating Systems, etc. Such independent access control systems result in multiple access control configurations each of which deals with the access control in its own application context. Since those multiple configurations are operated in isolation, and maintained by possibly different administrators, they are likely to be incoherent. In this paper, we propose a logical specification to reason about multiple access control configurations. Our specification can be used to detect the incoherence in multiple configurations. Furthermore, it of offers many kinds of policies for multiple configurations that can capture several kinds of requirements for multiple access control systems.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.135-149
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• 2016

Cloud radio access network (C-RAN) refers to the virtualization of base station functionalities by means of cloud computing. This results in a novel cellular architecture in which low-cost wireless access points, known as radio units or remote radio heads, are centrally managed by a reconfigurable centralized "cloud", or central, unit. C-RAN allows operators to reduce the capital and operating expenses needed to deploy and maintain dense heterogeneous networks. This critical advantage, along with spectral efficiency, statistical multiplexing and load balancing gains, make C-RAN well positioned to be one of the key technologies in the development of 5G systems. In this paper, a succinct overview is presented regarding the state of the art on the research on C-RAN with emphasis on fronthaul compression, baseband processing, medium access control, resource allocation, system-level considerations and standardization efforts.

• Journal of the Korea Society of Computer and Information
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• v.5 no.3
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• pp.84-90
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• 2000

This paper presents a design of an access control mechanism that can resolves the complicated problems of access control requirements in internet environment. In this paper, we proposed an access control mechanism which can satisfy the combined goals of confidentiality integrity and availability of any resource. We defined an access control mechanism from the viewpoints of identity-based, rule-based and role-based policy and implemented 6 access control operations. The Proposed access control mechanism can protect resources from unauthorized accesses based on the multi-level security policies of security label, integrity level, role and ownership.

• International Journal of Advanced Culture Technology
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• v.6 no.4
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• pp.65-70
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• 2018

Wireless data broadcasting system that can support any number of clients is the effective alternative for the challenge of scalability in ubiquitous computing in IoT environment. In the system, it is important to evaluate quickly the performance parameter, the access time that means how quickly the client access desired data items. In this paper, we derive the mathematical model for the access time in the wireless data broadcast system adopting two-tier indexing scheme. The derived model enables to evaluate the access time without the complicated simulation. In order to evaluate the model, we compare the access time by the model with the access time by the simulation.