• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1355-1362
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• 2004

In this paper, we present the performance analysis of a multi-path searcher operating over Rayleigh fading channels when multiple transmit antennas are employed in the down-link of W-CDMA system. The simulation results for the receiver operating characteristics (ROC) for 1, 2, and 4 transmit antennas are presented to corroborate the theoretical analyses. We also propose a procedure to find the optimum parameters of double-dwell serial searcher according to the number of the multiple transmit antennas. Our analyses and simulations indicate that post-detection integration is not necessary when the number of transmit antennas is more than two. Finally, we found that increasing transmit diversity order does not necessarily improve the detection performance when the received pilot signal strength is relatively low. Therefore, this gives us a practical criterion on increasing transmit diversity order.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1045-1049
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• 2001

Wireless LANs in the 2.4 ㎓ ISM- band create a new Electromagnetic Compatibility (EMC) problem. We investigated the interference characteristics between such wireless LANs in the case of identical systems, systems with different technical parameters for modulation and demodulation, and using a Gaussian noise source as a disturbance source. Experimental results show that higher throughput is obtained when adjacent wireless LANs use different systems, and that interference characteristics can be evaluated experimentally using a Gaussian noise source. Calculated BER characteristics for the interference agree with experimental measurements, indicating that this calculation method can be used for the design of the wireless LAN network to avoid interference. It is possible to construct an efficient wireless LAN network by combining different wireless LAN systems.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.417-421
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• 2005

In the recent digital communication systems, the performance of Turbo Code using the error correction coding depends on the interleaver influencing the free distance determination and the recursive decoding algorithms that is executed in the turbo decoder. However, performance depends on the interleaver depth that needs many delays over the reception process. Moreover, turbo code has been known as the robust coding methods with the confidence over the fading channel. International Telecommunication Union(ITU) has recently adopted it as the standardization of the channel coding over the third generation mobile communications(IMT-2000). Therefore, in this paper, we proposed the interleaver that has the better performance than existing block interleaver, and modified turbo decoder that has the parallel concatenated structure using MAP algorithm. In the real-time voice and video service over third generation mobile communications, the performance of the proposed two methods was analyzed and compared with the existing methods by computer simulation in terms of reduced decoding delay using the variable decoding method over AWGN and fading channels for CDMA environments.

• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.211-214
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• 2007

In this paper, we have designed microstrip antenna if 800[MHz] band It will be able to integrate TRS(Trunked Radio System), GSM(Global System for Mobile telecommunication) band including the CDMA(Code Division Multiple Access) band we designed repeater and a base station antenna which is possible at the ship and marine of safety. It is improves a narrow bandwidth problem of microstrip antenna. It had U-shaped feeding structure at a rectangular patch And ground or feeding structure used between dielectric constant(${\varepsilon}_T$ = 2.1), patch or feeding structure used between dielectric constant(${\varepsilon}_T$ =1). So it used a duplex resonance effect Designed frequency bandwith(V5WR 2:1) if the antenna showed good characteristic of $780[MHz]{\sim}1.83[GHz]$ to 2.61[GHz]. Also the E-plan and H-plan all profit 9.4[dBi] above, the 3[dB] beam width showed the characteristic over the E-plan and H-plan $60^{\circ}$ to be improved.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.3
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• pp.219-222
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• 2007

In this paper, we have designed microstrip antenna of 800[MHz] band. It will be able to integrate TRS(Trunked Radio System), GSM(Global System for Mobile telecommunication) band including the CDMA(Code Division Multiple Access) band. we designed repeater and a base station antenna which is possible at the ship and marine of safety. It is improves a narrow bandwidth problem of microstrip antenna. It had L-shaped feeding structure at a rectangular patch and added the parallel L-slot that used a duplex resonance effect. Also for the improvement of profit the stack with the perpendicular. Designed frequency bandwith(VSWR 2:1) of the antenna showed good characteristic of 789${\sim}$1046[MHz] to 292[MHz](36%). Also the E-plan and H-plan all profit 6.4[dBi] above, the 3[dB] beam width showed the characteristic over the E-plan $44.7^{\circ} and H-plan $61.8^{\circ} to be improved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1686-1692
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• 2012

Spreading sequence play an important role in wireless communications, such as in a CDMA(code division multiple access) communication system and multi-carrier spectrum communication system. Spreading sequences with low cross-correlation, in a direct-sequence spread spectrum communication system, help to minimize multiple access interference and to increase security degree of system. Analysis of cross-correlations between the sequences is a necessary process to design sequences. However it require lots of computing time for analysis of cross-correlations between sequences. In this paper we propose a method which is possible to compute effectively cross-correlation using subfield in the process of practical computation of cross-correlation between nonlinear binary sequences.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.454-456
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• 2002

Embedded system is used a lot in electric home appliances and home network equipment. However, this system is designed to operate by the system operator directly at home and operator could find out them only when he pays attention to the system in case event happens. In this paper, to improve above things, it designed to remote-control system anywhere in which internet access is possible as well as at home, and also it designed SMS(short message service) information transmission system to inform the errors to the operator when they happen. To design the system, development board(be included the Strong Arm), CDMA module, and electric door lock are used as hardware, and web browser, CGI(common gateway interface) programming, and C-language are used for implementation of software in embedded-linux platform.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1210-1230
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• 1997

In this paper, we suggest an architecture of DS/CDMA tranceiver composed of one pilot channel used as reference and multiple traffic channels. The pilot channel-an unmodulated PN code-is used as the reference signal for synchronization of PN code and data demondulation. The coherent demodulation architecture is also exploited for the reverse link as well as for the forward link. Here are the characteristics of the suggested DS/CDMA system. First, we suggest an interlaced quadrature spreading(IQS) method. In this method, the PN coe for I-phase 1st channel is used for Q-phase 2nd channels and the PN code for Q-phase 1st channel is used for I-phase 2nd channel, and so on-which is quite different from the eisting spreading schemes of DS/CDMA systems, such as IS-95 digital CDMA cellular or W-CDMA for PCS. By doing IQS spreading, we can drastically reduce the zero crossing rate of the RF signals. Second, we introduce an adaptive threshold setting for the synchronization of PN code, an initial acquistion method that uses a single PN code generator and reduces the acquistion time by a half compared the existing ones, and exploit the state machines to reduce the reacquistion time Third, various kinds of functions, such as automatic frequency control(AFC), automatic level control(ALC), bit-error-rate(BER) estimator, and spectral shaping for reducing the adjacent channel interference, are introduced to improve the system performance. Fourth, we designed and implemented the DS/CDMA MODEM to be used for variable transmission rate applications-from 16Kbps to 1.024Mbps. We developed and confirmed the DS/CDMA MODEM architecture through mathematical analysis and various kind of simulations. The ASIC design was done using VHDL coding and synthesis. To cope with several different kinds of applications, we developed transmitter and receiver ASICs separately. While a single transmitter or receiver ASC contains three channels (one for the pilot and the others for the traffic channels), by combining several transmitter ASICs, we can expand the number of channels up to 64. The ASICs are now under use for implementing a line-of-sight (LOS) radio equipment.

• Proceedings of the Korea Multimedia Society Conference
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• 2001.06a
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• pp.299-302
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• 2001

무선 이동 네트워크 환경을 이용하여 특정교역에 산재해 있는 노상 및 노외 유·무료 주자창의 무인 요금징수장비를 실 시간으로 제어·관리하여 이용자에게 휴대용 컴퓨터 핀 셀룰러폰을 통해 정보를 제공할 수 있는 주차관리시스템을 제안한다. 본 논문에서 각 요금징수장비는 현재 상용화되어 있는 각 통신사의 PCS 또는 Cellular Phone의 COMA SMS(Code Division Multiple Access Short Message Service)를 이용하여 장비의 상태 및 제어 기법을 제안하였으며, 이 경우 추가적인 무선망 관리장비가 필요 없이 mobile phone만을 이용하기 때문에 아직 일반화되지 않은 고비용의 무선패킷통신을 대신할 수 있어 향후 S/W 교체만으로 전환 가능하여 보다 유용한 기법이 될 것으로 기대 된다.

• The KIPS Transactions:PartD
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• v.9D no.1
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• pp.161-166
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• 2002

The existing method in PN code acquisition process have a problem in PN code acquisition time because PN code searching is accomplished in one epoch. In this paper, we propose algorithm that can reduce PN code acquisition time because PN code searching is accomplished in each other two epoches. The designed ASIC chip using proposed algorithm confirmed that the area (the number of gates) increase more than existing method in PN code acquisition, but the performance of PN code acquisition is better than existing method.