• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.149-154
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• 2004

In this paper, Interference-Cancelled CDMA system using binary ZCD spreading codes is introduced. Proposed Interference-Cancelled CDMA system can be usefully used for the intra-cellular Interference-Cancelled wireless communication systems. Binary ZCD spreading code sets have various sequence period and family sizes and the ZCD properties of them are very effective for Interference-cancelled CDMA Systems. In this paper, we mathematically analyzed the system performance of our proposed Interference-Cancelled CDMA system in the AWGN channel and various interference environments such as MAI and MPI. Furthermore, using the BER performance simulation we certify the available interference cancellation properties of the proposed system.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.09a
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• pp.384-384
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• 1995

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.27-30
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• 1999

A spatio-temporal vector channel model is introduced for the position location (PL) estimation problem for CDMA cellular system environment. Two common ways for the PL make use of the AOA (Angle Of Arrival) and TDOA (Time Difference Of Arrival) from a subscriber to the multiple sensors (base stations). In this paper, we applied the derived vector channel to simulate the multipath channel for the angle of the signal arrival in CDMA systems. Cross-correlation method is a good candidate among other direction finding algorithms available in literature, especially in wideband modulation as in the CDMA system. The PL estimation errors are evaluated for different channels, which are obtained as a parameter of scattering radius of the suggested model. We noted that the number of sensors (base-stations) are related to the PL errors in favor of the available data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.12B
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• pp.2109-2119
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• 2000

In this paper, the Packet CDMA Reservation ALOHA protocol is proposed to support the multi-traffic services such as voice and videophone services with handoff calls, high-rate data and low-rate data services efficiently on the multi-rate transmission in uplink cellular systems. The frame structure, composed of the access slot and the transmission slot, and the proposed access permission probability based on the estimated number of contending users for each service are presented to reduce MAI. The assured priority to the voice and the videophone handoff calls is given through higher access permission probability. And through the proposed code assignment scheme, the voice service can be provided without the voice packet dropping probability in the CDMA/PRMA protocols. The code reservation is allowed to the voice and the videophone services. The low-rate data service uses the available codes during the silent periods of voice calls and the remaining codes in the codes assigned to the voice service to utilize codes efficiently. The high-rate data service uses the assigned codes to the high-rate data service and the remaining codes in the codes assigned to the videophone service. Using the Markov-chain subsystem model for each service including the handoff calls in uplink cellular systems, the steady-state performances are simulated and analyzed. After a round of tests for the examples, through the proposed code assignment scheme and the access permission probability, the Packet CDMA Reservation ALOHA protocol can guarantee the priority and the constant QoS for the handoff calls even at large number of contending users. Also, the data services are integrated efficiently on the multi-rate transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.12A
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• pp.1806-1814
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• 2000

본 논문에서는 CDMA 계층구조 셀룰러 시스템에서 매크로 셀 기지국과 통신을 하는 고속 이동국과 마이크로 셀 기지국과 통신을 하는 저속 이동국의 비 그리고 소프트 핸드오프 영역 비에 따른 기지국이 받는 간섭전력과 시스템 용량을 구하였다. 매크로 셀 기지국과 통신을 하는 고속 이동국이 마이크로 셀 기지국과 통신을 하는 저속 이동국보다 많을수록 기지국이 받는 간섭전력은 증가하며 따라서 시스템 용량은 감소한다. 그러나 소프트 핸드오프 영역의 증가로 기지국이 받는 간섭전력은 감소하명 시스템 용량은 상당히 증가한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1107-1114
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• 1999

In this paper, we analyze the effect of co-channel interferers coming from other systems with composite log-normal shadowing and Nakagami fading on the capacity of the imperfect power-controlled DS/CDMA cellular system. The analytical results are compared with the results of Prasad and Jansen in which they derive the result under the condition of imperfect power-control of DS/CDMA system and without considering interference. And the outage probability is calculated fro the effect of the log-normal/Nakagami faded inferers on DS/CDMA system using Schwartz and Yeh's method. With the deviation of outage probability, we analyzed the decreases in the capacity of DS/CDMA system with the variation of the paramenters of the imperfect power-control, the fadig index, the processing gain, the power ratio, the voice activity factor, and the number of interferers. Analysis reuslts have shown that the capacity of DS/CDMA system is very sensitive to the imperfect power-control and the number of interferers. It is shown that the DS/CDMA system capacity decreased according to increase of the deviation of the impertect power-control, the increase of the fading, and the increase of interferer number.

• Journal of Communications and Networks
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• v.12 no.3
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• pp.216-221
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• 2010

In this paper, we propose and develop a new algorithm for the principle subspace tracking by orthonormalizing the eigenvectors using an approximation of Gram-Schmidt procedure. We carry out a novel mathematical derivation to show that when this approximated version of Gram-Schmidt procedure is added to a modified form of projection approximation subspace tracking deflation (PASTd) algorithm, the eigenvectors can be orthonormalized within a linear computational complexity. While the PASTd algorithm tries to extracts orthonormalized eigenvectors, the new scheme orthonormalizes the eigenvectors after their extraction, yielding much more tacking efficiency. We apply the new tracking scheme for blind adaptive multiuser detection for non-stationary cellular CDMA environment and use extensive simulation results to demonstrate the performance improvement of the proposed scheme.

• Journal of Communications and Networks
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• v.2 no.1
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• pp.46-57
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• 2000

Ongoing standardization effort on 3G cellular system in 3GPP (UNTS) is based on GPRS core network and promises a global standard for systems capable of offering ubiquitous access to internet for mobile users. Considered radio access systems(FDD CDMA, TDD CDMA, and EDGE) are optimized for robust mobile use. However, there are alternative relatively high-rate radio interfaces being standardized for WLAN (IEEE802.11 and HIPER-LAN/2) which are capable of delivering significantly higher data rates to static or semi-static terminals with much less overhead. Also WPANs(BLUETOOTH, IEEE802.15), which will be present in virtually every mobile handset in the near future, are offering low cast and considerable access data rate and thus are very attractive for interworking scenarios. The prospect of using these interfaces as alternative RANs inthe modular UMTS architecture is very promising. Additionally, the recent inclusion of M-IP in the UMTS R99 standard opens the way for IP-level interfacing to the core network. This article offers an overview into WLAN-Cellular interworking. A brief overview of GPRS, UMTS cellular architectures and relevant WLAN standards is given. Possible interworking architectures are presented.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.2
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• pp.22-30
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• 1998

In this paper, we analyze CDMA systems using M-orthogonal spreading codes. We assume that each user one set of M-orthogonal spreading codes allocated randomaly. The effect of multiple access interference from the reference and adjacent cells is considered slowly frequency selective rayleigh fading channels. and the adjacent cells interference is considered toanalyze the system performance. We calculate bit error rate and the maximum number of users whoe can communicate simulaneously within a cell by suing Rake receiver. By comparing CDMA systemwhich transmits 1 bit/spreding code, our system shows bit error rate decreases as M increases under the same bandwidth and infromation rate.

• ETRI Journal
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• v.19 no.3
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• pp.259-280
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• 1997

This paper briefly explains the configuration of CDMA Mobile System (CMS) test bed. The measured fading and delay results of CDMA signal in Taejon area are shown. In comparison to other cellular systems, there are more parameters in the CDMA systems that affect system performance and capacity. We performed the optimization test of the selected parameters and present the effect of each parameter on the performance. This paper presents the capacity and performance test results of CMS. The capacity test was performed on ETRI site of three sectors in Taejon area. The performance tests include call completion rate, busy hour call attempt, and the delay characteristics of voice.