• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.4 no.5
• /
• pp.1005-1015
• /
• 2000

In this paper, the performance of Hybrid CDU MFSK system has been analyzed in the environment that narrowband Class-A impulsive noise include Gaussian noise in wireless communication channel and Nakagami fading. The performance of system improved to adopting both of technique MRC diversity and BCH channel coding. The results show that there is substantial degraded in Hybrid CDMA system performance by impulse index is stronger and the fading index is smaller. But also improvement can be obtained when BCH coding techniques are adopted. Additional MRC diversity techniques is more improvement than BCH coding techniques when degraded environment with the low fading index. But BCH coding techniques is more improvement than MRC diversity techniques when fading index has been increased. The Hybrid CDMA MFSK system is incomplete to voice communication standard BER$(10^{-3})$ in Rayleigh fading by independent each adopting techniques BCH coding and MRC diversity. But it's satisfy(improvement can be obtained) to voice communication standard BER in strong impulse noise(24dB over) by adopting techniques BCH coding and MRC diversity at a time. Additional it's a substantial enhancement $(10^{-3})$satisfaction) in fading index (m=3, 22dB) in addition to strong impulse noise and 24dB over with data service standard $(10^{-5})$ BER satisfaction. This result show that there is error performance improved by diversity branch and coding advantage.

• Proceedings of the IEEK Conference
• /
• 2001.09a
• /
• pp.587-590
• /
• 2001

본 논문에서는 스마트 안테나를 적용하여 서로 다른 대역폭(1.25MHz, 5Mhz)과 서로 다른 환경(rural, urban)에서 W-CDMA 시스템의 성능을 분석하였다. 먼저 스마트 안테나 시스템의 성능을 분석하기 위해서 시·공간 상관특성을 갖는 채널이 필요하다. 이를 위해 시간 정보를 고려하기 위해 시변 선형 필터로 모델링하였고, 공간 정보를 고려하기 위하여 배열 응답 벡터를 삽입하였다. 이 때 공간적으로는 일정량의 각도 퍼짐을 갖는 부-다중경로 성분으로 구성된 한 개의 반사파가 한 방향으로부터만 수신된다고 가정하였다. 또한 한 칩 내에 들어오는 다중 경로 성분을 분리하여 가장 큰 신호 성분만을 찾아내어 원하는 사용자의 신호로 사용하는 방법으로 모의 실험을 실행하였다. 모의실험 결과, 협대역 CDMA를 사용하는 스마트 안테나 시스템보다 광대역 CDMA를 사용하는 스마트 안테나 시스템이 더 나은 성능을 보임을 확인할 수 있었다. 또한 스마트 안테나는 2D-RAKE receiver를 사용했을 때 urban area에서 보다 더 효과적임을 확인할 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.7
• /
• pp.737-743
• /
• 2011

In this paper, we designed and implemented a Monopole+IFA(Inverted F Antenna) hybrid antenna using the coupled feeding structure for the all band mobile phone. Studied antenna has wide band characteristics by the simultaneous operation both monopole and IFA under the coupled feeding structure. An antenna has designed PCB embedded type without antenna carrier component for the low in cost. Implemented antenna has within 2.5:1 for VSWR under LTE/CDMA/GSM900/DCS/USPCS/WCDMA/WiBro/WiFi in all band for the mobile services Measured average gains and efficiencies were -3.98~-0.09 dBi and 40.03~97.99 % for the LTE, CDMA, GSM900 band, and -3.90~-1.01 dBi and 40.70~79.31 % for the DCS, USPCS, WCDMA, WiBro, WiFi band. It's shown that studied antenna can be applied to all band mobile phone antenna including LTE.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.5
• /
• pp.1-9
• /
• 2000

In this paper, for the reverse link of a imperfect power controlled DS/CDMA cellular system when a mobile radio channel is a Rayleigh distributed multipath fading channel, A extended DS/CDMA blocking probability formula considering both shadowing and multipath fading is derived. Erlang capacity and equivalent channel number considering shadowing are analyzed and compared with those considering both shadowing and multipath fading, respectively. The DS/CDMA blocking probability is calculated based on the analysis method that obtains Erlang capacity and ICF(interference correction factor) using the median value of $E_{b(i)}$/ $I_{0}$ corresponding to each reverse link user Assuming that the blocking probability set 2%, it is observed that the Erlang capacity is 19.97 Erlang at the data rate $R_{b}$=9.6 kbps and 11.67 Erlang at the data rate $R_{b}$=14.4 kbps and then is less 16% and 19% than the Erlang capacity considering shadowing only, respectively. It is also shown that the effect of multipath fading must not be ignored and then exact Erlang capacity and equivalent channel numbers that the DS/CDMA cellular system can support are provided.d.d.d.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.5
• /
• pp.1-7
• /
• 2011

In this paper, CDD(Cyclic Delay Diversity)-DF(Decode-and-Forward)-Relay scheme is proposed for MC-CDMA(Multicarrier-Code Division Multiple Access) systems over multipath Rayleigh fading channels. The advantages of general DF schemes come at the expense of the spectral efficiency since the source and all the relays must transmit on orthogonal channels. In order to mitigate this disadvantage of general DF schemes, we have applied CDD techniques to each relays so that all the relays can transmit on single channel. It means that all R-D link channels can be considered as a single channel which is widely delay spread. Namely, it causes the increasing the number of multipath so that the frequency diversity gain can be achieved in MC-CDMA systems. By simulations, we have compared proposed one with general DF scheme. Therefore, it is confirmed that the proposed one can be a possible solution to achieve cooperative diversity gain without a reduction of spectral efficiency.

• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.273-276
• /
• 2003

In this paper, we designed and made up/down converter (UDC) for using W-CDMA digital pre-distortion system which is one of the efficiency enhancement techniques. UDC is required that frequency up(baseband to RF) and down(RF to baseband) of information signals. The focus of the design and PCB layout is to satisfy the linearity of the UDC. We tested that UDC was satisfied specification which is based on 3GPP base stations and repeaters. The ACLR results which are -51.84dBc(Up Converter) and -55.0dBc(Down Converter) at upper 5 MHz offset from center-frequency show that UDC satisfy the 3GPP specification with superior linearity data.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 1999.11a
• /
• pp.135-138
• /
• 1999

본 논문에서는 차세대 멀티미디어 통신인 IMT-2000의 억세스방식으로 제안되고 있는 비동기 W-CDMA(3GPP) System을 적용, 기존의 IS-95와는 달리 Pilot symbol을 이용하여 페이딩채널을 추정하여, 이를 통한 다중사용자 간섭제거 방법으로 PIC(Parallel Interference Cancellation)을 적용하고 DPCCH(Contorl)과 DPDCH(Data)의 Power Ratio에 따른 성능을 분석하였다. 시뮬레이션 결과 Hard decision 인 경우 사용자5명의 설정에서 C:D : 3:7 과 4:6에서 가장 좋은 성능을 보였으며, 사용자를 10명으로 늘렸을 경우 C:D = 4:6 보다는 3:7의 비율에서 가장 나은 성능을 보였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.4
• /
• pp.356-362
• /
• 2003

In this paper, we propose a predistortion technique which uses a novel combination of the second harmonic technique and the difference frequency technique to achieve independent control of the 3rd and 5th order intermodulation products generated by the PA. The second harmonic and difference frequency terms are generated using an envelope detector and two frequency multipliers. The RF predistorter has capability to independently control of the 3rd and 5th order intermodulation products so that high power amplifier is optimized for linear characteristics. From the measurement results, over the frequency band 2137.5 MHz to 2142.5 MHz, ACPR reduction of 11 dB is obtained for a single 30 dBm W-CDMA carrier.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.6A
• /
• pp.923-928
• /
• 2001

본 논문은 레이크 수신기의 성능 개선에 관한 것으로 다중 경로 페이딩에 의한 시간 지연으로 나타나는 자기 간섭이 제거된 DS-CDMA/QPSK 신호의 성능을 분석하였다. 자기 간섭 제거를 위해 새로운 레이크 수신기를 제안하고 제안된 수신기의 시스템 성능은 차량 이동통신 환경, 실내 이동통신 환경과 실외에서 실내로 이동중인 환경으로 구분하여 라이시안과 레일리 페이딩 환경에서 분석하였다. 제안된 레이크 수신기는 적용한 DS-CDMA 시스템의 합성 수신 SNR 증가로 오율 성능이 개선되었으며 오율 $10^{-3}$에서 K=6[dB]일 경우에 1[dB]의 성능 개선 효과가 나타났으며, K=3.7[dB]일 경우에는 1.5[dB], K=0[dB]일 경우에는 2[dB]의 성능 개선 효과를 얻을 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.606-610
• /
• 2003

본 논문에서는 임펄스 잡음과 실내 무선 페이딩, 그리고 다중 사용자 간섭 환경에서 멀티코드 DS/CDMA-BPSK 통신 시스템의 BER 성능을 분석하였다. 분석 결과 멀티코드의 수가 증가함에 따라서 하나의 사용자에게 점유되는 채널의 수가 증가하여 시스템의 성능은 열화 되나 반면에 시스템에서 제공할 수 있는 서비스의 속도는 멀티코드의 수에 비례하여 증가함을 알 수 있었다. 또한, 성능개선기법으로 Turbo Code와 다이버시티 기법을 적용함으로써 전력선에서 방출되는 임펄스 잡음 파라미터인 A=0.2, $\Gamma$' =0.22에서 전송속도에 따라 5.5, 7, 16dB의 신호전력 이상에서 $10^{-5}$ 이하의 BER 성능을 얻을 수 있었다.