• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.1 no.1
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• pp.53-59
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• 2008

In this paper, we compare two methods that improve the reliability of soft output at the receiver of MIMO communications. The receiver complexity of spatially mutiplexed MIMO system is in proportion to the number of candidate vectors. Low complexity receiver techniques involving a small number of candidate vectors, provide soft output values of low reliability. In order to improve the low reliability of soft output, two previous methods can be used; the first method involves a clipping threshold, the second method uses Euclidian distance instead of squared Euclidian distance. In the paper, we address the theoretical similarity of the two methods, then we compare the two methods from the perspective of hardware implementation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1256-1265
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• 1996

Soft-decision detectors are used in many FEC and ARQ schemes to enhance the bit-error-probability and system throughput. Also, the hybrid-ARQ protocol is a very efficient schemeto achieve overall performance improvement. In this paper, we propose a new hybrid-ARQ protocol based on the first-order Reed-Muller codes employing soft-decision detectors. The Reed-Muller codes have the virtue of being able to use the fast Green machine decoder that is simple to implement. As the performance measures, the bit-error-probability and system throughput are evaluted for the proposed hybrid-ARQ procol, and compared with those of other hybrid-ARQ schemes. It is shown that the use of the proposed hybrid-ARQ protocol results in significant performance improvement without causing much loss in view of system complexity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.705-710
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• 2011

In this paper, we proposed the low computational complexity soft-decision e-BCH decoding algorithm based on the Chase algorithm. In order to make the test patterns, it is necessary to re-order the least reliable received symbols. In the process of ordering and finding optimal decoding symbols, high computational complexity is required. Therefore, this paper proposes the method of low computational complexity algorithm for soft-decision e-BCH decoding process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2791-2797
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• 2010

In recent years, the goal of providing high speed wireless data services has generated a great amount of interest among the research community. Several researchers have shown that the capacity of the system, in the presence of flat Rayleigh fading, improves significantly with the use of combined MIMO and LDPC. To feed the soft values to LDPC decoder, the soft values must be calculated from multiple transmitter and receiver antennas in Rayleigh fading channel. It requires high computational complexity to get the soft symbols by increasing number of transmitter and receiver antennas. Therefore, this thesis proposed on effective algorithm for calculation of soft values from multiple antennas based on LLR. As result, This thesis shows that maximum 61% of computational complexity is reduced with a little loss of performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6A
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• pp.611-616
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• 2006

In this paper, we propose a practical implementation method of a soft bit decision expression for an R-QAM (Gray coded Rectangular Quadrature Amplitude Modulation) signal based on the Max-Log-MAP algorithm. The parameters of the soft decision expression for the practical implementation can be obtained with simple arithmetic functions associated with some deterministic parameters such as a received value, distances between symbols, and the order of modulation on a signal space. Also, we analyze the performance of an iterative decoding scheme for the QAM signal with I/Q phase unbalance. The unbalance results from the non-ideal characteristic of components such as a phase shifter between in-phase and quadrature paths for quadrature modulator/demondulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.6
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• pp.540-549
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• 2013

An adaptive non-uniform quantization scheme is proposed for soft-decision error correction in NAND flash memory. Even though the conventional maximizing mutual information (MMI) quantizer shows the optimal post-FEC (forward error correction) bit error rate (BER) performance, this quantization scheme demands heavy computational overheads due to the exhaustive search to find the optimal parameter values. The proposed quantization scheme has a simple structure that is constructed by only six parameters, and the optimal values of them are found by maximizing the mutual information between the input and the output symbols. It is demonstrated that the proposed quantization scheme improves the BER performance of soft-decision decoding with only small computational overheads.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.324-330
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• 2002

In this paper, we proposed a simple modification on Fiebig's REC algorithm for multiuser detection of FH/MFSK systems replacing hard limiter with soft limiter. The performance improvement of our modified REC algorithm has been confirmed with computer simulations. for the parameter of interest, the capacity could be increased about 5% or more without degrading the reliability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.5
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• pp.623-629
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• 2020

In this paper, a multiple transmission communication system employing ranging based transmission timing adjustment capability is proposed. In addition, a decision feedback equalizer with the use of combinations of soft decision and hard decision adequate to the proposed multiple transmission communication system is also proposed. The proposed ranging based transmission timing adjustment capability makes the received signals from the multiple transmission points centered on the different symbol timing boundaries. The decision making method for the inputs to the proposed decision feedback equalizer is adaptively selected between soft decision and hard decision as per channel conditions like SNR. The performance of the proposed method had been analyzed through the simulation under the fading channel environments and compared with the previous methods. The simulation results showed performance improvement of the proposed method over the existing ones without noticeable increments in complexities.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1996.06a
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• pp.583-586
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• 1996

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2347-2352
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• 2012

In this paper, a new alternating equalizer and its differential adjustment algorithm are proposed. The proposed alternating equalizer achieves equalization effectively using an algorithm performing symbol decisions based on soft/hard decision. In addition, it is possible to improve the initial blind convergence speed and steady-state error performance simultaneously by adjusting the equalizer differentially according to the relative reliability of the symbol decisions by soft/hard decision devices. The simulation results on 16/64-QAM constellations under multipath propagation channel and additive noise conditions confirmed to support usefulness of the proposed method.