• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.9-18
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• 1998

In this paper, an equalization technique for OFDM(orthogonal frequency division multiplexing) in a time-variant multipath fading environment is described. A loss of subchannel orthogonality due to time-varying multipath fading channels leads to interchannel interference (ICI) which increases the error floor in proportion to Doppler frequency. A simple frequency-domain equalizer which can compensate the effect of ICI caused by time variation of multipath fading channel is proposed by modifying the previous frequency-domain equalization technique with taking into account only the ICI terms significantly affecting the error performance. The effectiveness of the proposed approach is demonstrated via computer simulation by applying it to OFDM systems when the multipath fading channel is slowly time variant.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.217-223
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• 2010

In this paper, an interchannel interference (ICI) cancellation method is proposed for multiple frequency offsets in orthogonal frequency division multiplexing (OFDM) systems. When several same signals are received from different transmitters simultaneously, multiple frequency offsets may occur at the receiver because of the frequency difference of the oscillators of the two transmitters and the receiver. This causes degradation of system performance because OFDM systems are very sensitive to the frequency offsets. In this paper, we propose a method to eliminate the effect of the multiple frequency offsets for OFDM systems. The method is accomplished in two steps: compensation of the frequency offset in the time domain and subsequent cancellation of the ICI in the frequency domain. Through computer simulations, we verify the effectiveness of the proposed ICI cancellation method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.329-337
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• 2005

In this paper, we propose a new type of RAKE receiver for complementary code keying (CCK) codes, which is suitable for the multipath channel with large delay spread. Our proposed system is based on channel matched filter (CMF) with decision feedback equalizer (DFE) and contains codeword DFE structure. In our system, inter chip interference (ICI) and inter symbol interference (ISI) generated due to multipath environments are calculated by using detected CCK codeword. Also it uses the error correcting capability of CCK codes, and it can remove ISI and ICI at the same time.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.40-46
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• 2007

In this paper, the effect of a Doppler Spread caused by a mobile station (MS) is analyzed for transparent mobile multi-hop relays (MMR) systems based on orthogonal frequency division multiplexing (OFDM). The exact expression of interchannel interference (ICI) power and the upper bounds of ICI power are derived for OFDM systems with cooperative MMR or non-coopeartive throughput enhancement (TE) MMR. Also, the exact signal-to-interference ratio (SIR) and its lower bound as well as ICI power and its upper bound, derived in this paper, are evaluated by computer simulation with the OFDM parameter set used for mobile WiMax (WiBro) systems.

• 수도
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• v.24 no.4 s.85
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• pp.69-74
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• 1997

ICI 프로그램에서 보는 바와 같이 주정부의 주된 역할은 지방의 프로그램을 지원해주는 것이다. 이 지원은 ICI 사업계획의 목적달성을 위한 정책과 규정을 수립하는 것이다. 즉, 재정적 보상, 연구, 훈련 및 기술지원 등이다. 향후 장기계획수립에 ICI보전 및 재이용 가능성을 포괄하는 수자원보전 및 재이용에 관한 내용을 포함한다. 그러나 중요한 사실은 항상 각 지방의 프로그램을 지원해 주는데 초점을 맞추는 것이어야 한다.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2004.04a
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• pp.90-96
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• 2004

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.10-17
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• 2006

For orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) should be longer than the length of channel impulse response, resulting in a loss of bandwidth efficiency. In this letter, the CP reconstruction (CPR) technique is first applied to a multi-input multi-output (MIMO)-OFDM system with insufficient CP. The intercarrier interference (ICI) from multiple transmit antennas is so large for MIMO system that it can not be sufficiently suppressed with the conventional CPR procedure used in single-input single-output (SISO) system. A new minimum mean-square error (MMSE) equalization and ordering process is proposed for MIMO system to suppress the ICI during the CPR procedure. By applying the proposed CPR algerian to MIMO-OFDM system, we can obtain both the benefits of multiplexing gai and spectral efficiency gain.

• Advances in pediatric surgery
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• v.17 no.1
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• pp.23-34
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• 2011

We analyzed the clinical characteristics and outcome of ileocecal and small bowel intussusceptions (ICI and SBI) in the pediatric patients. From August 2003 to July 2010, 144 children with intussusception were included in this study. We retrospectively reviewed the clinical records and Imaging study findings. A total of 86 children with ICI and 58 children with SBI were diagnosed. Children with SBI were older than ICI ($36.6{\pm}24.6$ months vs. $24.2{\pm}21.6$ months, p=0.002). Typical symptoms such as irritability, abdominal mass, bloody stool were more frequent in ICI than SBI (p<0.05) patients. In the ICI group, intussusceptums were reduced with air reduction (84.5%), surgery (17.4%), and spontaneity (1.2%). All patients in the SBI group were reduced spontaneously. SBI occurred in older age and was reduced spontaneously more frequently than ICI. Conservative management with close observation with follow-up by ultrasonography is recommended for SBI.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.499-506
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• 2012

In this paper, we analyze the effects of phase noise and frequency offset that cause performance degradation. Basically, we like to propose reduced PNFS(Phase Noise and Frequency offset Suppression) algorithm. The OFDM system is seriously affected by ICI component such as phase noise, frequency offset and Doppler effects. Especially, complicated processing algorithm with high complexity was required it in order to compensate those ICI components. So, we propose PNFS algorithm that can decrease complexity and compensate ICI components. We propose a method decreased complexity by approximation of parameters that affect slightly performance change and compare the quantity of conventional and revised PNFS algorithm. Also, simulation shows that BER performance of revised PNFS algorithm can be improved slightly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.259-266
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• 2011

Femtocells are expected as the surest way to increase the system capacity with higher-quality links and more spatial reuse in future networks. In spite of their great potential, the system capacity is highly susceptible to network density because a large portion of users are exposed to inter-cell interference (ICI). In this work, we proposed a dynamic interference avoidance scheme in densely deployed cell environments. Our proposed DDIA (Distributed Dynamic ICI Avoidance) scheme not only works in a fully distributed manner, but also controls interference link connectivity of users with high agility so that it is suited for self-organizing networks (SONs). We introduced the concept of ICI-link and two-tier scheduling in designing the DDIA scheme. To avoid ICI without any central entity, our scheme tries to harmonize all base stations (BSs) with users adaptively. Through extensive simulations, it was shown that our proposed scheme improves the throughput of users by more than twice on average compared to the frequency reuse factor 1 scheme, who are exposed to ICI while maintaining or even improving overall network performance. Our scheme operates well regardless of network density and topology.