• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.3B
• /
• pp.251-258
• /
• 2002

In this paper, an adaptive convolutional coding method in multicarrier direct sequence code division multiple access (DS/CDMA) systems is considered. In order to accommodate a number of coding rates easily and make the encoder and decoder structure simple, we use the rate compatible punctured convolutional (RCPC) code. To achieve maximum data throughput, an adaptive rate system based on the channel state information (the SINR estimate) is proposed. We show that the proposed adaptive rate convolution coded multicarrier DS/CDMA systems can enhance spectral efficiency and provide frequency diversity.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.10
• /
• pp.2679-2686
• /
• 1996

In this paper, we propsoed the two methods to improve the conventional decision feedback interference canceller in DS/SS communication systems. The data bit is obtained by correlating the PN sequence with the received signals to the present time k, and thus the errors in the reference signal can be reduced by newly deciding all the reference signals with the resultant data bit. Additionally the cancelled signals are computed with less weight for initial reference signals of low processing gain, and highly weighted as the processing gain goes up. the resulting interference canceller outperforms the existing ones. By simulation, we found the proposed algorithm has "2-3 dB" performance gain at BER 10$^{-3}$ compared to the conventional descision feedback algorithm.algorithm.

• Annual Conference of KIPS
• /
• 2000.10b
• /
• pp.1211-1214
• /
• 2000

의사잡음(PN) 부호는 이상적인 자기상관특성을 갖지 못한다. 본 논문에서는 이상적인 자기상관 특성을 갖지 못하는 PN 부호에 대하여 이상적인 자기상관 특성을 가지도록 하여 동기 직접확산 부호분할 다원접속(DS/CDMA)시스템에서 부가적인 하드웨어 복잡성의 큰 증가 없이 간섭제거가 가능한 수신기 구조를 제안한다. PN 부호 오프셋을 사용하여 사용자 부호를 할당하고, 제안한 수신기 알고리즘을 PN 부호 오프셋을 사용한 시스템에 적용하여 다원접속 간섭 신호가 제거됨을 보이며 컴퓨터 모의실험을 통하여 이를 확인한다.

• Journal of Plant Biology
• /
• v.9 no.3_4
• /
• pp.7-13
• /
• 1966

The investigation on the grassland type was conducted by the data in the previous these (Park 1963, '64, '65, '66). The results obtained are as follows; 1) I defined that the relationship between the valves of DS and the main species of the grass in Korea(Table Ⅰ) Grassland Stage ; Waste type………6 community-types Short grass type………3 community-types Pteridium type………1 community-types Tall grass type………4 community-types Sasamorpha type………1 community-types Shrubby Stage; Lespedeza type Pioneer tree type………6 species Forest Stage; Deciduous broad leave tree type………6 species Evergreen broad leaved tree type………3 species Evergreen needle leaved tree type………7 species 2) I defined; that the relationship between the valves of DS and the grassland type in Korea(Table 2). Of grassnland type, the range of valves of DS, 50-220 belongs to waste type; 130-310 short grass type; 230-640 tall grass type; 210-450 pteridium type; 510-970 sasamorpha type; 730-1450 shrubby type; 3) I decided; The succession stage centering on the Sasamorpha purpuracens in Korea(Table 3). 4) I decided the climate type and the grassland succession in Korea(Table 4).

• Proceedings of the IEEK Conference
• /
• 2002.06a
• /
• pp.69-72
• /
• 2002

In this paper, adaptive minimum mean-squared error (MMSE) multiuser detector combined with decision-feedback detector (DFD) is considered fur near-far resistant DS-CDMA system. To provide a reliable input to the adaptive MMSE detector, multiple-access interference (MAI) is regenerated using bit estimates from DFD and subtracted from the received signal. In the adaptive MMSE detector, the effect of the imperfect cancellation is compensated by a least mean square (LMS) algorithm. Through the numerical results, it is shown that, in a near-far situation, the proposed scheme provides superior performance to the matched filter (MF) receiver, adaptive MMSE detector, and DFD in terms of the bit error rate (BER).

• Journal of Communications and Networks
• /
• v.7 no.1
• /
• pp.36-44
• /
• 2005

In this paper, we present a retransmission power adjustment (RPA) scheme for DS/SSMA ALOHA packet radio systems with packet combining. In the proposed RPA scheme, retransmission power is adjusted in such a way that the erroneously-received packet can be recovered with a minimized interference to other user packets. We analyze the performance of the system with the RPA by employing the equilibrium point analysis (EPA), and confirm that the results obtained from the EPA are very close to the simulation results in low power cases. Simulation results demonstrate that the RPA scheme brings forth performance gain in the throughput and the average delay while saving a significant amount of transmission power. We also investigate the stability of the system from the EPA results, and conclude that the system becomes stable as the offered load increases or the level of retransmission power decreases.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.9A
• /
• pp.1322-1331
• /
• 2000

In this paper, we compare the performance of noncoherent DS-CDMA system where orthogonal code is used for identifying the user to reduce multiple access interference or for M-ary orthogonal signaling to improve the performance of demodulation. The effects of M-ary orthogonal signaling on the noncoherent demodulation is investigated and compared with one of coherent demodulation. The analysis results show that M-ary orthogonal signaling gives better performance than quasi-synchronous orthogonal scheme for a moderate number of users when the processing gain is 128 over AWGN channel. In addition, when the number of user is 41, M=64 orthogonal signaling has a similar performance to the quasi-synchronous orthogonal scheme at the BER of 10-2 when the time misalignment between channels is within 1/2 chip and M=256 orthogonal signaling always outperforms the quasi-synchronous orthogonal scheme. Start after striking space key 2 times.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.48 no.4
• /
• pp.467-473
• /
• 1999

We have realized the two kinds of power line communication systems by the FSK MODEM. The first approach is the DS-SS (Direct suquence-spread spectrum) technique using 8 bits pseudo noise, the other is Convolutional coding method by the new algorithm. Their characteristics are comparied with each other by experimenting their Bit Error Rates (BER) in high level of Noise. The results have showed that two systems are useful to the application of HA (Home Automation) systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.21 no.2
• /
• pp.34-39
• /
• 2007

UWB(Ultra Wide Band) system for high speed and high accurate location has been studying actively. This paper presents the design and implementation of RF transceiver for DS-CDMA(Direct Sequence-Code Division Multiple Access) UWB device. Major components of RF transceiver such as Low Noise Amplifier(LNA) and Band Pass Filter(BPF) are designed and then fabricated to meet wideband characteristics. The RF transceiver was implemented by the use of the fabricated components and commercial devices after carrying out performance simulation. Through the performance evaluation of the UWB RF transceiver with W-CDMA signal, the approach of design, implementation and evaluation of RF transceiver which is available to DS-CDMA UWB system is verified.

• 한국정보통신설비학회:학술대회논문집
• /
• 2005.08a
• /
• pp.422-426
• /
• 2005

초고속통신, 고 정밀 위치정보 시스템 등을 구현하기 위해 광 대역 특성을 요구하는 UWB(Ultra Wideband) 시스템에 대한 연구가 활발히 진행되고 있다. 본 논문에서는 DS-CDMA(Direct Sequence - Code Division Multiple Access)를 근간으로 하는 3 GHz $\sim$ 5GHz의 주파수 대역을 갖는 UWB 시스템에서 아날로그 QPSK(Quadrature Phase Shift Keying) 변복조, 주파수 변환 및 전력 증폭 기능을 수행하는 RF 트랜시버 설계 방안을 제시하였고, 광 대역 특성을 만족하는 주요 구성 성분들의 설계 방법 및 성능 특성을 분석하였다. 상용 부품 및 제작된 부품 들을 이용하여 구현된 RF 트랜시버에 대한 성능평가를 통해 DS-CDMA 방식의 UWB 시스템을 위한 RF 트랜시버 설계 및 구현 접근 방법을 검증하였다.