• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.1
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• pp.22-30
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• 1994

The error probability of the DS-CDMA / DPSK cellular mobile communication system with CCI canceller and MRC diversity reception technique has been analyzed in the cellular radio channel which is characterized by AWGN, Multi-User Interference(MUI) and m-distribution fading. System capacity i. e., number of user per cell has been derived and the evaluated results are shown in figures as a function of PN code sequence length, fading index, BER, number of diversity branches and $E_b/N_o$, Here, the voice activity factor is assumed to be 3/8, the number of sectors in a cell 3 and Multi-User Iner- ference is modeled as Gaussian process.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.49-55
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• 2015

In cognitive radio network (CRN), spectrum sensing is an elementary level of technology for non-interfering to licensed user. Required sample number for spectrum sensing is directly related to the throughput of secondary user and makes the tradeoff between the throughput of secondary user and interference to primary user. Required spectrum sensing sample is derived from required false alarm, detection probability and minimum required SNR of primary user (PU). If we make clustering and minimize the required transmission boundary of secondary user (SU), we can relax the required PU SNR for spectrum sensing because the required SNR for PU signal sensing is related to transmission range of SU. Therefore we can achieve efficient throughput of CRN by minimizing spectrum sensing sample. For this, we design the tradeoff between gain and loss could be obtained from clustering, according to the size of cluster members through game theory and simulation results confirm the effectiveness of the proposed method.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.58-62
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• 2016

In this paper, we propose a pre-processing scheme for improving indoor positioning accuracy in impulsive noise channel environments. The impulsive noise can be generated by multi-path fading effects by complicated indoor structures or interference environments, which causes an increase in demodulation error probability. The proposed pre-processing scheme is performed before a triangulation method to calculate user's position, and providing reliable input data demodulated from a received signal to the triangulation method. Therefore, we studied and proposed an adaptive threshold function for mitigation of the impulsive noise based on wavelet denoising. Through results of computer simulations for the proposed scheme, we confirmed that Bit Error Rate and Signal-to-Noise Ratio performance is improved compared to conventional schemes.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.05a
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• pp.21-32
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• 2002

In accordance with the development plans of Ulsan harbor, Ulsan new harbor will be contructed considering supporting Ulsan harbor as a safe berthing and departure at single buoy mooring(SBM). In this study, we used a full-mission ship handling simulator adopting 300,000 DWT VLCC manoeuvered at the planned Ulsan SBM. Five masters who have had a long experience of ship maneuvering were called to carry out the simulations, of which each scenario were tried one, completed total of 68 times. The marine traffic safety was assessed in terms of 1) the closest point of approach(CPA) to other SBM and breakwater in the vicinity and the probability of crossing the restricted area of the closest SBM and fairway limit, 2) subjective evaluation such as the mental burden and the maneuvering difficulty of shiphanders, and 3) the opinions of shiphandlers. From the result of this simulation, we have a conclusion as follows; First, because crude oil berthing angle is so small by current S-OiL Co. crude oil buoy by SK Co. No 3 crude oil buoy different view SK Co. No 3 crude oil buoy and interference of current KNOC crude oil buoy, Berthing is impossible, and Emergency departing is very dangerous too operation impossible. Second it is desirable that SK Co. No 2 and No 3 Single buoy Mooring that do different view controls position so that to be not put in straight line each other. Third, SK Co. No 1 and 2 single buoy mooring that do different view to Onsanhang berthing and departing is seized by single buoy mooring by external force ship that set sail does faith control need.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1A
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• pp.9-17
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• 2004

Adapt ive and fixed step size PC (power control) schemes for accommodating voice, video, and data are evaluated according to the different PC command rates and their effects on integrated Voice/Video/Data are investigated. The required minimum power levels are derived as PC thresholds and the effects of PC errors on channel quality and radio 1 ink capacity are investigated. The services with high bit rates and low bit error rates can cause a significant effect on the radio link qualifies of the other types of traffic. The results show that the adapt ive step size PC scheme for voice/video/data services can achieve more capacity and cause less interference to the radio channels because less minimum PIL(Power Increment Level) is required for the specified radio link outage probability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7A
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• pp.757-767
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• 2008

Start Ongoing next generation networks are expected to be deployed over current existing networks, in the form of overlayed heterogeneous networks, in particular, in hot spot areas. Therefore, it will be necessary to develop an interworking technique such as load balancing, to achieve increased overall resource utilization in the various heterogeneous networks. In this paper, we present a new load balancing mechanism termed 'soft' load balancing where the IP(Internet Protocol) traffic of a user is divided into sub-traffic, each of which flows into a different access network. The terminology of soft load balancing involves the use of both load sharing and handover techniques. Through a numerical analysis, we obtain an optimal LBR (Load Balancing Ratio) for determining the volume of traffic delivered to each network over an overlayed multi-cell environment. Using the optimal LBR, a more reliable channel transmission can be achieved by reducing the outage probability efficiently for a given user traffic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.479-485
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• 2013

Recently, interest for wireless communication technology with improved security and low eavesdropping probability is increasing rapidly recognizing that information security is an important. Chaos signal can be used encode information efficiently due to irregular phenomena. Chaotic signal is very sensitive to the initial condition. Chaos signal is difficult to detect the signal if you do not know the initial conditions. Also, chaotic signal has robustness to multipath interference. In this paper, we evaluate the performance of correlation delay shift keying (CDSK) modulation with different chaotic map such as Tent map, Logistic map, Henon map, and Bernoulli shift map. Also, we analyze the BER performance depending on the selection of spreading factor (SF) in CDSK. Through the theoretical analyses and simulations, it is confirmed that Henon map has better BER performance than the other three chaotic maps when spreading factor is 70.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.8
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• pp.46-51
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• 2012

In this paper, we investigate the power allocation for cognitive relay networks. Cognitive relay networks offer not only increasing spectral efficiency by spectrum sharing but also extending the coverage through the use of relays. For spectrum sharing, conventional works have assumed that secondary users know perfect channel information between the secondary and primary users. However, this channel information may be outdated at the secondary user because of the time-varying properties or feedback latency from the primary user. This causes the violation for interference constraint, and the secondary user cannot share the spectrum of the primary after all. To overcome this problem, we propose the power allocation scheme for the secondary user under the allowable primary user's outage probability constraint. Since the proposed power allocation scheme does not use the instantaneous channel information, the secondary users have lower feedback burden. In addition, the proposed scheme is also robust to the outdated channel environment.

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.581-588
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• 2002

In this paper, we newly propose the optical CDMA routing scheme for the radio access network. At the radio base station (RBS), the received radio signals are multiplied by the PN codes and converted to the CDMA radio signals. In the next optical CDMAS are performed and multiplxed by using the PN codes which are the addresses of the routing mobile switching center (MSC). At the MSC, the CDMA radio signals are routined to another MSC by the CDM receiver at the routing node. In the case MSC is equal to the desired MSC, the radio signal is correlated by the two-layerd spectrum despreading at a time. Finally we theoretically analyze the signal-to-interference and noise power ratio of regenerated signal and the routing error probability and show the availability of proposed scheme.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2008.04a
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• pp.243-246
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• 2008

ISM(Industrial, Scientific, Medical)대역은 비면허 대역으로 일정한 출력 규제만 지키면 자유롭게 사용할 수 있다는 장점으로 인하여 육상 통신뿐만 아니라 해상 통신 영역까지 그 사용량이 급증하고 있다. 이에 어선 내에서 사용하는 전파응용설비 및 ISM대역을 사용하는 소출력무선기기 등과의 전파간섭 문제는 시스템의 안정성을 열화시킬 수 있는 요인이 되며, 선박상황을 고려하면 안전성과 직결되므로, 간과되지 말아야 한다. 따라서 ISM대역에서 사용되거나 사용될 무선설비의 간섭확률 분석은 필수적이다. 본 논문에서는 Monte-Carlo 방식을 기반으로 하는 SEAMCAT를 이용하여 거리 및 밀도에 따른 간섭 시나리오와 전파 간섭 simulation methodology를 제안하였으며, 해상에서 환경을 가정하여 다른 전파간섭을 배제하였다. 제안된 시나리오를 적용하여 13.56MHz ISM 대역의 거리 시나리오 시뮬레이션 결과 RFID는 4.7m 이상, 모형기기는 2.7m 이상의 동종 기기간 이격거리를 가질 경우 간섭 영향이 양호하였다. 밀도 시나리오 시뮬레이션 결과 RFID(${V_r}$)를 중심으로 간섭 영향권에 RFID와 모형기기가 각각 2개 이하, 모형기기(${V_r}$)를 중심으로 간섭 영향권에 모형기기 2개 이하, RFID 1개 이하로 사용될 경우 통신환경이 양호함을 알 수 있었다. 제안된 간섭 시나리오 및 시뮬레이션 기법은 향후 ISM대역의 규제 정책 및 간섭확률 분석에 기여할 것으로 기대된다.