• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.6
• /
• pp.1150-1155
• /
• 2007

Orthogonal Frequency Division Multiplexing (OFDM) is an emerging multi-carrier modulation scheme, which has been adopted for several wireless standards such as IEEE 802.11a and HiperLAN2. A well-known problem of OFDM is its sensitivity to frequency offset between the transmitted and received carrier frequencies. This frequency offset introduces inter-carrier interference (ICI) in the OFDM symbol. This paper investigates three methods for combating the effects of ICI: ICI self-cancellation (SC), maximum likelihood (ML) estimation, and extended Kalman filter (EKF) method. These three methods are compared in terms of bit error rate performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.11
• /
• pp.1191-1197
• /
• 2003

In the multi-carrier OFDM communication system, the inter-carrier-interference(ICI) produced by phase noise in the transceiver local oscillator makes a severe influence on the system performance. In this paper, a new ICI self-cancellation scheme in the data-conversion type is proposed to reduce effectively the ICI. Also, the common phase error(CPE), ICI and carrier to interference power ratio(CIR) are found by the linear approximation of the phase noise. Then, the proposed method is compared with the conventional OFDM to analyze the efficiency of system performance improvement. When the number of subcarriers is 64, there are respectively the SNR gain of 0.6 ㏈ in the phase noise variance of 0.3 with QPSK and 1.5 ㏈ in the phase noise variance of 0.1 with 16 QAM at BER=10$\^$-3/. As a result, the performance degradation by ICI can be effectively lowered in the proposed system with ICI self. cancellation scheme, compared with the conventional OFDM system.

• Korean Journal of Radiology
• /
• v.22 no.4
• /
• pp.584-595
• /
• 2021

Objective: Immune checkpoint inhibitor (ICI) therapy has shown activity against melanoma brain metastases. Recently, promising results have also been reported for ICI combination therapy and ICI combined with radiotherapy. We aimed to evaluate radiologic response and adverse event rates of these therapeutic options by a systematic review and meta-analysis. Materials and Methods: A systematic literature search of Ovid-MEDLINE and EMBASE was performed up to October 12, 2019 and included studies evaluating the intracranial objective response rates (ORRs) and/or disease control rates (DCRs) of ICI with or without radiotherapy for treating melanoma brain metastases. We also evaluated safety-associated outcomes. Results: Eleven studies with 14 cohorts (3 with ICI combination therapy; 5 with ICI combined with radiotherapy; 6 with ICI monotherapy) were included. ICI combination therapy {pooled ORR, 53% (95% confidence interval [CI], 44-61%); DCR, 57% (95% CI, 49-66%)} and ICI combined with radiotherapy (pooled ORR, 42% [95% CI, 31-54%]; DCR, 85% [95% CI, 63-95%]) showed higher local efficacy compared to ICI monotherapy (pooled ORR, 15% [95% CI, 11-20%]; DCR, 26% [95% CI, 21-32%]). The grade 3 or 4 adverse event rate was significantly higher with ICI combination therapy (60%; 95% CI, 52-67%) compared to ICI monotherapy (11%; 95% CI, 8-17%) and ICI combined with radiotherapy (4%; 95% CI, 1-19%). Grade 3 or 4 central nervous system (CNS)-related adverse event rates were not different (9% in ICI combination therapy; 8% in ICI combined with radiotherapy; 5% in ICI monotherapy). Conclusion: ICI combination therapy or ICI combined with radiotherapy showed better local efficacy than ICI monotherapy for treating melanoma brain metastasis. The grade 3 or 4 adverse event rate was highest with ICI combination therapy, and the CNS-related grade 3 or 4 event rate was similar. Prospective trials will be necessary to compare the efficacy of ICI combination therapy and ICI combined with radiotherapy.

• Journal of Advanced Navigation Technology
• /
• v.16 no.6
• /
• pp.988-996
• /
• 2012

Assuming perfect channel state information (CSI), the conventional interference alignment (IA) algorithm in the uplink cellular system suppresses inter-cell interference (ICI) by aligning ICI to a randomly selected reference vector. However, IA in practice relies on limited feedback between base stations and users, resulting in residual ICI. In this paper, we propose the optimization of the reference vector that minimizes the upper-bound of residual ICI power. Secondly, the iterative IA that designs the direction of transmit and receive filter is proposed to minimize the residual ICI as well as maximize the desired signals. Moreover, we propose the user scheduling method combined with proposed IA schemes which provides the multiuser diversity gain in multi-cell environments. Finally, the performance gain of the proposed IA algorithms compared with the existing IA are analyzed and demonstrated by simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.6A
• /
• pp.676-684
• /
• 2008

In digital video broadcasting-terrestrial (DVB-T), which is the European digital terrestrial television standard, the orthogonal frequency division multiplexing (OFDM) has been adopted for signal transmission. The main reasons using OFDM are to increase the robustness against the frequency selective fading and impulse noise, and to use available bandwidth efficiently. However, channel variation within an OFDM symbol destroys orthogonality between subcarriers, resulting in inter-carrier interference (ICI), which increases an error floor in proportional to maximum Doppler spread. This paper provides an ICI analysis in both time and frequency domains while existing literatures analyze the ICI effects mainly in frequency domain and proposes the algorithms that estimate the channel impulse response and channel variation using least square (LS) algorithm which is the most simple channel estimation technique. And we propose adaptive channel estimation algorithm that estimates the velocity of terminals. The simulation results show that proposed algorithm has similar performance with about 1.5% computational complexity of noise and ICI reduction LS algorithm in low speed environments.

• International Journal of Computer Science & Network Security
• /
• v.23 no.6
• /
• pp.27-34
• /
• 2023

This paper proposed an Inter-Carrier-Interference (ICI) Canceling Orthogonal Frequency Division Multiplexing (OFDM) receiver for 5G mobile system to support 500 km/h linear motor high speed terrestrial transportation service. A receiver in such high-speed train sees the transmission channel which is composed of multiple Doppler-shifted propagation paths. Then, a loss of sub-carrier orthogonality due to Doppler-spread channels causes ICI. The ICI Canceler is realized by the following three steps. First, using the Demodulation Reference Symbol (DMRS) pilot signals, it analyzes three parameters such as attenuation, relative delay, and Doppler-shift of each multi-path component. Secondly, based on the sets of three parameters, Channel Transfer Function (CTF) of sender sub-carrier number 𝒏 to receiver sub-carrier number 𝒍 is generated. In case of 𝒏≠𝒍, the CTF corresponds to ICI factor. Thirdly, since ICI factor is obtained, by applying ICI reverse operation by Multi-Tap Equalizer, ICI canceling can be realized. ICI canceling performance has been simulated assuming severe channel condition such as 500 km/h, 2 path reverse Doppler Shift for QPSK, 16QAM, 64QAM and 256QAM modulations. In particular, for modulation schemes below 16QAM, we confirmed that the difference between BER in a 2 path reverse Doppler shift environment and stationary environment at a moving speed of 500 km/h was very small when the number of taps in the multi-tap equalizer was set to 31 taps or more. We also confirmed that the BER performance in high-speed mobile communications for multi-level modulation schemes above 64QAM is dramatically improved by the use of a multi-tap equalizer.

• Korean Journal of Materials Research
• /
• v.20 no.5
• /
• pp.267-270
• /
• 2010

Sn doped $In_2O_3$ (ITO) and ITO/Cu/ITO (ICI) multilayer films were prepared on glass substrates with a reactive radio frequency (RF) magnetron sputter without intentional substrate heating, and then the influence of the Cu interlayer on the methanol gas sensitivity of the ICI films were considered. Although both ITO and ICI film sensors had the same thickness of 100 nm, the ICI sensors had a sandwich structure of ITO 50 nm/Cu 5 nm/ITO 45 nm. The ICI films showed a ten times higher carrier density than that of the pure ITO films. However, the Cu interlayer may also have caused the decrement of carrier mobility because the interfaces between the ITO and Cu interlayer acted as a barrier to carrier movement. Although the ICI films had two times a lower mobility than that of the pure ITO films, the ICI films had a higher conductivity of $3.6{\cdot}10^{-4}\;{\Omega}cm$ due to a higher carrier density. The changes in the sensitivity of the film sensors caused by methanol gas ranging from 50 to 500 ppm were measured at room temperature. The ICI sensors showed a higher gas sensitivity than that of the ITO single layer sensors. Finally, it can be concluded that the ICI film sensors have the potential to be used as improved methanol gas sensors.

• Advances in pediatric surgery
• /
• v.17 no.1
• /
• pp.23-34
• /
• 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 Communications and Information Sciences
• /
• v.30 no.6A
• /
• pp.465-473
• /
• 2005

In this paper, the reduction scheme of Interchannel Interference(ICI) caused by the phase noise in Orthogonal Frequency Division Multiplexing(OFDM) systems for archiving high data rates is proposed. The performance of conventional common phase error(CPE) compensation method is degraded by the phase noise with wide 3dB bandwidth in OFDM systems width a higher-order constellation. After estimating dominant ICI coefficients using pilot subcarriers and data subcarriers adjacent to pilot subcarriers, the proposed scheme compensates OFDM signals distorted by the phase noise using estimated coefficients in the time or frequency domain. Also, in order to determine the length of dominant ICI coefficients effectively, the estimation method of the 3dB bandwidth of the phase noise is proposed. The proposed phase noise reduction method is shown to improve the Bit Error Ratio(BER) performance compared with the conventional CPE compensation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.6A
• /
• pp.583-591
• /
• 2008

OFDM (orthogonal frequency division multiplexing) has serious problem of high PAPR (peak-to-average power ratio). Recently, CI/OFDM (carrier interferometry OFDM) system has been proposed for the low PAPR. However, CI/OFDM system shows another problem of ICI because of phase offset mismatch due to the phase noise. In this paper, to simultaneously reduce the PAPR and ICI effects, we propose an A-CI/OFDM (advanced-CT/OFDM). This method improves the BER performance by use of the margin of phase offset at CI codes. Propose system to reduce the effect the phase noise, even though it shows a little bit higher PAPR than conventional CI/OFDM, so we apply the PTS among the PAPR reduction techniques to proposed system to mitigate this problem. Therefore, it improves the total BER performance because the proposed method can decrease the effect of phase noise and get the gain in PAPR reduction performance. From the simulation results, we can show the performance comparison between the conventional OFDM, CI/OFDM and A-CI/OFDM.