• Title/Summary/Keyword: bit error rate

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Cold Data Identification using Raw Bit Error Rate in Wear Leveling for NAND Flash Memory

  • Hwang, Sang-Ho;Kwak, Jong Wook;Park, Chang-Hyeon
    • Journal of the Korea Society of Computer and Information
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    • v.20 no.12
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    • pp.1-8
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    • 2015
  • Wear leveling techniques have been studied to prolong the lifetime of NAND flash memory. Most of studies have used Program/Erase(P/E) cycles as wear index for wear leveling. Unfortunately, P/E cycles could not predict the real lifetime of NAND flash blocks. Therefore, these algorithms have the limited performance from prolonging the lifetime when applied to the SSD. In order to apply the real lifetime, wear leveling algorithms, which use raw Bit Error Rate(rBER) as wear index, have been studied in recent years. In this paper, we propose CrEWL(Cold data identification using raw Bit error rate in Wear Leveling), which uses rBER as wear index to apply to the real lifetime. The proposed wear leveling reduces an overhead of garbage collections by using HBSQ(Hot Block Sequence Queue) which identifies hot data. In order to reduce overhead of wear leveling, CrEWL does not perform wear leveling until rBER of the some blocks reaches a threshold value. We evaluate CrEWL in comparison with the previous studies under the traces having the different Hot/Cold rate, and the experimental results show that our wear leveling technique can reduce the overhead up to 41% and prolong the lifetime up to 72% compared with previous wear leveling techniques.

Bit Error Rate of Underlay Decode-and-Forward Cognitive Networks with Best Relay Selection

  • Ho-Van, Khuong;Sofotasios, Paschalis C.;Alexandropoulos, George C.;Freear, Steven
    • Journal of Communications and Networks
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    • v.17 no.2
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    • pp.162-171
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    • 2015
  • This paper provides an analytic performance evaluation of the bit error rate (BER) of underlay decode-and-forward cognitive networks with best relay selection over Rayleigh multipath fading channels. A generalized BER expression valid for arbitrary operational parameters is firstly presented in the form of a single integral, which is then employed for determining the diversity order and coding gain for different best relay selection scenarios. Furthermore, a novel and highly accurate closed-form approximate BER expression is derived for the specific case where relays are located relatively close to each other. The presented results are rather convenient to handle both analytically and numerically, while they are shown to be in good agreement with results from respective computer simulations. In addition, it is shown that as in the case of conventional relaying networks, the behaviour of underlay relaying cognitive networks with best relay selection depends significantly on the number of involved relays.

Overlap-Based Chirp Spread Spectrum Transmission Scheme for Maritime Multipath Environment (해양 다중 경로 환경에 알맞은 오버랩 기반 처프 확산 대역 전송 기법)

  • Chae, Keunhong;Lee, Seong Ro;Yoon, Seokho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39C no.11
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    • pp.1124-1131
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    • 2014
  • The chirp spread spectrum (CSS) technique that transmits data signal by using a chirp signal is often used for maritime wireless communication systems such as sound detection radar systems for submarines. However, maritime multipath environment could reduce the data rate of the CSS system. To tackle the problem, an overlap-based CSS transmission scheme is proposed and analyzed in this paper: Based on the approximated Gaussian Q function, we derive a closed form expression of the bit error rate (BER) of the proposed overlap-based CSS system and investigate the mathematical relationship between the number of overlaps and the intersymbol interference (ISI).

Performance of SFBC OFDM Transmission Systems Using PSAM Technique (PSAM 방식의 SFBC OFDM 전송 시스템의 성능)

  • Choi, Seung-Kuk
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.15 no.5
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    • pp.1031-1037
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    • 2011
  • Pilot symbol assisted modulation (PSAM) can be used for the channel estimation in orthogonal frequency division multiplexing (OFDM) transmission systems. However, imperfect channel estimates in PSAM systems degrade the bit error rate (BER) performance. I derive the BER of PSAM OFDM systems over time dispersive fading channels. The BER performance of OFDM systems with SFBC antenna diversity are analyzed, where data is transmitted over time and frequency selective Rayleigh fading channel. The performance of this PSAM SFBC OFDM systems, gauged by the average bit error rate, is analyzed considering the channel estimation error.

Bit Error Rate of Generalized Triangular QAM (일반화된 TQAM의 비트 오류 확률)

  • Cho, Kyongkuk
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39A no.5
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    • pp.229-236
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    • 2014
  • Quadrature Amplitude Modulation (QAM) is widely used in contemporary wired and wireless communications systems. In this paper, I propose a generalized triangular quadrature amplitude modulation (gTQAM) that includes the square quadrature amplitude modulation (SQAM), TQAM, and ${\Theta}$-QAM as special cases. Therefore, the proposed gTQAM forming a lattice of arbitrary triangles provides a versatile structure in signal constellations compared to other QAM schemes. For M-ary gTQAM, I derive an exact closed-form expression for the bit error rate (BER), and present the optimal signal constellations for given SNR values from the derived BER expression. Finally, I validate the derived BER results through computer simulations.

Performance Evaluation of OFDM Systems Dependent on Subcarrier Allocation Method (부반송파 할당방식에 따른 OFDM 시스템의 성능 분석)

  • Choi, Seung-Kuk
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.2
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    • pp.295-302
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    • 2014
  • OFDM technique uses multiple sub-carriers for the data transmission. Therefore, inter carrier interference is generated because of nonlinear high power amplifier and carrier frequency offset. Wireless OFDM transmission over Doppler fading channels also causes inter carrier interference. The interference increases the bit error rate in receiver. Sub-carrier allocation methods in LTE and WiMAX standards are different. The performance of OFDM systems using different sub-carrier allocation, gauged by the bit error rate, is analyzed considering the nonlinear high power amplifier, carrier frequency offset and Doppler fading channels.

Performance Analysis of Optical Transmitters with the Non-ideal Mach-Zehnder Modulator

  • Lee, Dong-Soo
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.22 no.11
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    • pp.9-14
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    • 2008
  • This paper presents the performance analysis of 10[Gb/s] optical duobinary transmitters with the non-ideal Mach-Zehnder modulator which does not have exactly 50/50 splitting/combining ratios by computer simulations. For driving voltage ratios(=driving voltage/switching voltage) with smaller than 100[%], the transmission performance has been greatly affected by extension of LPF bandwidths. Nevertheless, the performance has been degraded when the driving voltage ratio is 100[%]. The smaller driving voltage ratios has, the more sensitivity improves by extension of LPF bandwidths under the asymmetry condition. But the driving voltage ratio with 80[%] has better bit error rate(BER) than those with 50[%] and 25[%].

Effects of LDPC Code on the BER Performance of MPSK System with Imperfect Receiver Components over Rician Channels

  • Djordjevic, Goran T.;Djordjevic, Ivan B.;Ivanis, Predrag N.
    • ETRI Journal
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    • v.31 no.5
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    • pp.619-621
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    • 2009
  • In this letter, we study the influence of receiver imperfections on bit error rate (BER) degradations in detecting low-density parity-check coded multilevel phase-shift keying signals transmitted over a Rician fading channel. Based on the analytical system model which we previously developed using Monte Carlo simulations, we determine the BER degradations caused by the simultaneous influences of stochastic phase error, quadrature error, in-phase-quadrature mismatch, and the fading severity.

Data Randomization Scheme for Endurance Enhancement and Interference Mitigation of Multilevel Flash Memory Devices

  • Cha, Jaewon;Kang, Sungho
    • ETRI Journal
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    • v.35 no.1
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    • pp.166-169
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    • 2013
  • In this letter, we propose a data randomization scheme for endurance and interference mitigation of deeply-scaled multilevel flash memory. We address the relationships between data patterns and the raw bit error rate. An on-chip pseudorandom generator composed of an address-based seed location decoder is developed and evaluated with respect to uniformity. Experiments performed with 2x-nm and 4x-nm NAND flash memory devices illustrate the effectiveness of our scheme. The results show that the error rate is reduced up to 86% compared to that of a conventional cycling scheme. Accordingly, the endurance phenomenon can be mitigated through analysis of interference that causes tech shrinkage.