• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.3-8
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• 2013

Bit patterned media (BPM) storage is one of the promising technologies to overcome the limitations of the conventional magnetic recording. However, there are some problems in a high areal density BPM storage, inter-track interference, inter-symbol interference and noise which are severely degrading performance of the system with reducing the bit error rate. In this paper, we present a simple iterative two-dimensional equalizer based on the contraction mapping theorem to mitigate these adverse effects. Furthermore, we examine that the channel characteristics of the proposed two-dimensional equalizer satisfies the convergence conditions. In the simulation we demonstrate the bit separation characteristics of the one-dimensional equalizer and the two-dimensional equalizer and evaluate the BER performance of the proposed equalizer comparing with the conventional equalizers. According to the results of experiments, the proposed equalizer is an promising equalizer with maintaining proper complexity for a high areal density BPM storage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5776-5782
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• 2014

Relay-assisted wireless communication systems have been studied widely to cope with shadow areas and extend the cell coverage. This paper proposes a space-frequency (SF) block coded single carrier-frequency division multiple access (SC-FDMA) transmission system in a relaying multi-path shadow area and present the performance comparison of SC-FDMA systems based on the signal-to-noise power ratio (SNR) between a relay and a destination station. The performance of relaying SC-FDMA systems can be improved by applying SF block code to the recovered signals of relays before re-transmitting them. The simulation result showed that the SNR performance of the proposed SF block coded relaying SC-FDMA system was approximately 5 dB better than the SNR performance of the single-path relaying SC-FDMA system at a symbol error rate (SER) of $10^{-2}$.

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.109-114
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• 2015

Frame synchronization is achieved by correlation between received symbols and a preamble pattern which is periodically appended at a frame header. In this paper, we deal with a frame detection method complaint with satellite-based DVB-S2 system. In DVB-S2, frame synchronization is performed under the low signal-to-noise ratio(SNR), a large frequency offset which can be up to 20% of a symbol transmission rate and unknown modulation schemes ranging from QPSK to 32-APSK. In this environment, we propose a method combining differential correlation based on SOF and PLSC with an accumulated correlation method for the detection of frame structures. In addition, detection performances about mean acquisition time(MAT) and detection error probability are evaluated via computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.830-837
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• 2005

ISI is caused by delay spread in the multipath channel environment. There are two kinds of channel equalizer: Linear and Non-Linear type according to the structures. In this paper, we propose an improved adaptive linear equalizer to mitigate ISI. The proposed adaptive equalizer is constructed by using asymmetrical Dsmvenu filter based on USE sub-optimal receiver. Asymmetrical structure of the transversal filter is realized by moving the main tap position from center to side. If this structure is used, we can divide ISI to precusor and postcusor. As a result the proposed equalizer has a larger extended compensation range than conventional adaptive linear equalizer. In computer simulation, we compare the bit error rate performance of the proposed linear equalizer with the conventional one on the S-V channel which is modeled for WB systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5A
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• pp.484-492
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• 2006

A multi-code biorthogonal code keying(MBCK) system consists of multiple waveform coding block, and the sum of output codewords is transmitted. Drawback of MBCK is that it requires amplifier with high linearity because its output symbol is multi-level. MBCK with constant amplitude preceding blcok(CA-MBCK) has been proposed, which guarantees sum of orthogonal codes to have constant amplitude. Redundant bits of CA-MBCK for constant amplitude coding are not only used to make constant amplitude signal but also used to improve the bit error rate(BER) performance at receiver. In this paper, we proposed a transmission scheme which combine CA-MBCK with $Q^{2}PSK$ to improve bandwidth efficiency of CA-MBCK. The BER performance of the scheme is same that of CA-MBCK in additive white gaussian noise(AWGN). And we showed that BER performance of the proposed system can be improved using redundant bits of constant amplitude preceding.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1205-1213
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• 2006

In this paper, we analyze the IQ(In-phase/Quadrature) imbalance effects at both transmitter and receiver side of OFDM(Orthogonal Frequency Division Multiplexing) and show that IQ imbalance is the parameter to improve the performance using ML and OSIC scheme. Especially, we can archive the diversity gain due to the IQ imbalance in multipath fading environment. In addition, new preamble format is proposed, which enable estimation of the channel and IQ imbalance parameters to maximize the diversity gain. Significant performance improvement is achieved by using the ML(Maximum Likelihood)and OSIC(Ordered Successive Interference Cancellation) with compensation compared to a standard receiver with no compensation for IQ imbalance and proposed channel estimation scheme achieves the better performance improvement than conventional.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.43-46
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• 2015

Recently, full-duplex communications has been considered as one of the most promising techniques for net-generation mobile communication system. In this paper, we propose a compressed sensing based signal detection technique for full-duplex generalized spatial modulation (FD-GSM) systems. In FD-GSM systems, some antennas are used for signal transmission according to input data and the otehrs are used for detecting signals received over the same frequency band. The self-interference (SI) is assumed to be completely removed by help for the recently proposed SI cancellation techniques. The proposed signal detection technique significantly outperforms the conventional ones in terms of symbol error rate (SER). We will investigate the optimal number of used antennas in FD-GSM systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1146-1153
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• 2007

In this paper, we analyze the I/Q imbalances effects at the WiBro uplimk when using direct-conversion RF transceiver. If I/Q imbalance exists, the transmit signal is spread over two sbcarriers. As a result, phenomenon of performance reducing is produced. Contrary to OFDM system in which one user uses all subcarrier, symmetrical two subcarriers are assigned other users in OFDMA system. I/Q imbalances elements can't be estimated such a conventional allocation method of tiles in subchannel and compensated. In order to solve the problem, We propose a new method in order that symmetrical two subcarriers are assigned one user. If novel method is applied, we can estimate I/Q imbalances and compensate distortion received signal. As a result, we can obtain a performance similar performance when I/Q imbalances is not existed. Also, if proper detection methods are used, we get the effect of performance improvement, because of diversity gain what is happened due to combining I/Q imbalances with multi path fading channel.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.104-110
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• 2008

In this paper, a novel 2-level-search sphere decoding algorithm for multiple-input multiple-output (MIMO) detection and its VLSI implementation are presented. The proposed algorithm extends the search space by concurrently performing symbol detection on 2 level of the tree search. Therefore, the possibility of discarding good candidates can be avoided. Simulation results demonstrate the good performance of the proposed algorithm in terms of bit-error-rate (BER). From the proposed algorithm, an efficient very large scale integration (VLSI) architecture which incorporates low-complexity and fixed throughput features is proposed. The proposed architecture supports many modulation techniques such as BPSK, QPSK, 16-QAM and 64-QAM. The sorting block, which occupies a large portion of hardware utilization, is shared for different operating modes to reduce the area. The proposed hardware implementation results show the improvement in terms of area and BER performance compared with existing architectures.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.15-22
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• 2012

This paper deals with the performance comparison and evaluation of blind adaptive equalizer, the PMCMA-MDD and DW-MCMA, that is used for compensation of the amplitude and phase distortion which occurs in the time dispersive channel. Basically, these algorithms are modification of MCMA cost function in order to obtain the fast convergence speed and reduced residual isi by taking the parallel and serial double structured and the combination of the concept of RCA for the updating the tap coefficient. We implements the algorithm of it and compare the recovered constellation, residual isi, MSE characteristics curve and SER in the signal to noise ratio given the time dispersive channel. As a result of simulation, the PMCMA-MDD has a good in recovered constellation than DW-MCMA. But in the SER, the DW-MCMA has a good than PMCMA-MDD.