• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.10
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• pp.25-32
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• 2011

We have analyzed adjacent cell dependency of threshold voltage shift caused by the cell to cell interference, and we proposed a 3-adjacent-cell model to model the pattern dependency of the threshold voltage shift. The proposed algorithm is verified by using MATLAB simulation and measurement results. In the experimental results, we found that accuracy of the proposed simple 3-adjacient-cell model is comparable to the widely used conventional 8-adjacient-cell model. The Bit Error Rate (BER) of LSB and of MSB is improved by 28.9% and 19.8%, respectively, by applying the proposed algorithm based on 3-adjacent-cell model to 20nm-class 2-bit MLC NAND flash memories.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.10
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• pp.46-53
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• 2011

This paper presents an equalizer reducing CCI(cell-to-cell interference) in MLC NAND flash memory. The CCI is a critical factor which affects occurring data errors in a cell, when surrounding cells are programed. We derived a characteristic equation for CCI considering write procedure of data that is similar with signal equalizing. The model considers the floating gate capacitance coupling effect, the direct field effect, and programming methods of the MLC NAND flash memory. We verify the proposed equalizer comparing with the measured data of 1-block MLC NAND flash memory. As the simulation result, the equalizer shows an error correction ratio about 60% under 20nm NAND process.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1095-1102
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• 2010

This paper presents an equalizer reducing CCI(cell-to-cell interference) in MLC NAND flash memory. High growth of the flash memory market has been driven by two combined technological efforts that are an aggressive scaling technique which doubles the memory density every year and the introduction of MLC(multi level cell) technology. Therefore, the CCI is a critical factor which affects occurring data errors in cells. We introduced an equation of CCI model and designed an equalizer reducing CCI based on the proposed equation. In the model, we have been considered the floating gate capacitance coupling effect, the direct field effect, and programming methods of the MLC NAND flash memory. Also we design and verify the proposed equalizer using Matlab. As the simulation result, the error correction ratio of the equalizer shows about 20% under 20nm NAND process where the memory channel model has serious CCI.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.3
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• pp.9-18
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• 1998

For constructionof the next generation satellite B-ISDN/ATM networks considering integration with terrestrial information infrastructure networks, various high speed and wideband satellites with be launched and they will make used of frequency reue techniques for efficient management of limited frequency resource. Therefore, CCI(Co-Channel Interference) inherent in frequency reuse will be a dominant factor in performance degradation of satellite networks. This paper alanyzes the ATM cell transmission performance degradation caused by CCI. The satellite link, including up-link and down-link thermal noise, CCI, and nonlinear satellite transponder, is modeled and interleaving technique is used for compensating the ATM cell transmission performance degradation caused by burst error of satellite link. First, each satellite link subsystem is analyzed in detail and then end-to-end ATM cell transmission performance is evaluated with BER and CLR. Specifically, ATMcell transmission performance degradation caused by CCI is evaluated in detail.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.92-98
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• 2007

We propose the schemes for the dynamic channel allocation (DCA) in multi-cell OFDMA systems to avoid co-channel interference (CCI) without the additional complexity. The allocatable subcarriers areas, which is designed to avoid CCI among cells, are determined for each cell. Each cell allocates the subcarriers within the allocatable subcarriers area of the cell independently. We consider the trade off between the reduced frequency selection diversity and the amount of CCI on a subcarrier by the determination of allocatable subcarriers area. Hence, the equal allocation bound scheme for the high selectivity channel and the flexible allocation bound scheme for the low selectivity channel are proposed. Through the numerical results, it is confirmed that the proposed schemes have better performance in the aspects of the number of overlapping allocated subcarriers, the capacity and the outage probability compared to the case which does not determined the allocatable subcarriers area.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.6
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• pp.2014-2034
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• 2015

This paper focuses on solving co-channel interference (CCI) issues arising in the open subscriber group (OSG) mode of heterogeneous networks (HetNets). Considering a general framework consisting of arbitrary number of picocells within a macro cell, where the inter-user interference (IUI) is the main CCI to macro user equipments (UEs), while the the inter-cell interference (ICI) is the major CCI to pico UEs. In this paper, three IA based transceiver design schemes are proposed. For macro cell, we uniformly use block diagonalization (BD) scheme to eliminate the IUI. And for picocells, three IA schemes are proposed to mitigate the ICI. The first scheme, named as zero forcing IA (ZF-IA) scheme, aligns the inter picocell interference onto an arbitrary sub-space of the cross-tier interference using ZF scheme. Considering the channel state information (CSI) of the desired channel of pico UEs, the second scheme, named as optimal desired sub-channel selected IA (ODC-IA) scheme, aligns the inter picocell interference onto a certain sub-space of the cross-tier interference, which guarantees the largest channel gain of the desired signal of pico UEs. The third IA scheme, named as maximum cross-tier interference selected IA (MI-IA) scheme, is designed for the system with less receive antennas. The inter picocell interference is aligned onto the space of the strongest cross-tier interference and only the interference on this space is nullified. The complexity analysis and simulations show that the proposed transceiver design schemes outperform the existing IA schemes in the OSG mode of HetNets, and the MI-IA scheme reduces the requirement of the receive antennas number with lower complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.409-416
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• 2007

In cellular orthogonal frequency division multiplexing (OFDM) networks, co-channel interference (CCI) leads to severe degradation in the BER performance. To solve this problem, maximum-likelihood estimation (MLE) CCI cancellation scheme has been proposed in the literature. MLE CCI cancellation scheme generates weighted replicas of the transmitted signals where weights represent the estimated channel transfer functions. The replica with the smallest Euclidean distance from the received signal is selected and data are detected. When the received power of the desired and interference signals are nearly the same, the BER performance is degraded. In this paper, we propose a closed-loop power control (PC) scheme capable of detecting the equal received power situation at the mobile station (MS) receiver by using the newly introduced parameter power ratio (PR). When this situation is detected, the MS sends a feedback to the desired base station (BS) which boosts the transmission power in the next frame. At cell edge where signal to interferer ratio (SIR) is considered to have average value between -5 dB and 10 dB, computer simulations show that the proposed CCI cancellation scheme has a gain of 7 dB at 28 Km/h.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.710-716
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• 2007

In this paper, a new scheme of downlink co-channel interference (CCI) cancellation in OFDM cellular networks is introduced for users at the cell-edge. Coordinated symbol transmission between base stations (BS) is operated where the same symbol is transmitted from different BS on different sub-carriers. At the mobile station (MS) receiver, we introduce a soft decision maximum likelihood CCI canceler and a modified maximum ratio combining (M-MRC) to obtain an estimate of the transmitted symbols. Weights used in the combining method are derived from the channels coefficients between the cooperated BSs and the MS. Simulations show that the proposed scheme works well under frequency-selective channels and frequency non-selective channels. A gain of 9 dB and 6 dB in SIR is obtained under multipath fading and flat-fading channels, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.240-246
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• 2013

In heterogeneous networks, the almost blank subframes (ABS) for inter-cell interference coordination (ICIC), which can be protected from the CCI due to unutilized subframes (i.e., ABS) is proposed. However, the analytical model for ABS-based systems has not been fully studied yet. In this paper, we derive a new analytical model to evaluate the performance of ABS-based systems. In an analytic model, we assume that each carrier in multicarrier systems, such as in OFDMA, is subject to large-scale fading, which is independent of other carriers. As a performance measure, we present the cumulative distribution function (CDF) for the effective SINR. We show the accuracy of the analytical model via simulation results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.37-46
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• 1996

In this paper, we analyzed the performance improvement of the DS-CDMA/dPSK cellular mobile communication system with CCI canceller and RAKE receiver techniques in mobile radio channel which is characterized by AWGN, Multi-user interference (mUI) and frequency-selective rayleigh fading. System capacity i.e., number of user per cell has been derived and the evaluated results are shown in figuraes as a function of PN code sequence length, number of RAKE receiver tap, BER and E$_{b}$/N$_{o}$. The voice activity factor is assumed to be 3/8 the number of sectors in a cell 3 and MUI is modeled as gaussian process. From the results, the capacity of the DS-CDMA/DPSK cellular mobile communication system is improved by adopting CCI canceller. When we adopt the RAKE receiver to mitigate the multipath fading, the error performance is improved and the amount of improvement is proportional ot the number of taps L in the case that each tap contains a signal component and the better of improvement can be obtained, the smaller of the SNR difference in each tap. The system capacity is more increased when the CCI canceller and the RAKE receiver is used in cascade.