• Journal of Communications and Networks
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• v.1 no.2
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• pp.99-110
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• 1999

The adaptive coded modulation (ACM) is a promissing way to provide a substantial improvement in spectral efficiency for slow fading channels. The basic idea is to adapt system functional-ity such as modulation, coding, information rate, and transmission power to varying channel conditions. In this work, the potential of adaptive coded modulation is investigated using cut-off rate anal-ysis in a unified way and using computer simulation. The anal-ysis includes various effects of fading channels such as feedback delay and channel prediction error. It was shown that the adaptive coded modulation can provide several folds of increase in spectral efficiency compared to a fixed coded-modulation system employing QPSK when channel varies slowly.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.12-15
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• 2000

In this paper, we have evaluated the performance of an OFDM system using hierarchical 16QAM (OFDM/HL-16QAM) for achieving high quality and high speed data and image transmission in multipath fading channel. The wireless channel for performance evaluation is assumed to include AWGN and two ray multipath fading. Through simulation we have obtained the BER performance of the system according to $E_{b}$, $N_{0}$, then compared the received image quality of proposed system with that of conventional system. From the result, it is shown that the OFDM/HL-16QAM system is more effective for data and image transmission.n.n.

• Journal of Advanced Navigation Technology
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• v.12 no.1
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• pp.54-60
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• 2008

The reliability of conventional wireless communication systems are diminished by multi-path fading, shadowing, propagation delay, pathloss, AWGN and an interference of the symbols. Therefore, we need more reliable system which can stably transmit multimedia datas over the poor communication environments, so, in this paper, we used STBC system based on STTC that allows a maximum space diversity gain of STBC scheme and channel efficiency, coding gain and diversity gain of STTC scheme at the same time. We did then analyzed the performance over the correlated slow fading channel between transmitter and receiver channels.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1269-1274
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• 2010

Wireless communication channels with the most severe multipath fading phenomenon that appears each time a different delay is caused by the frequency selective fading. At this time, ISI due to the performance degradation of wireless communication channels and data transfer speed gives the constraints. OFDM technique can remove ISI inserting longer guard interval than channel delay spread of channel between symbol. However, the multi-path delay of the channel to be serious with the guard interval can not eliminate ISI. In this case, using the equalizer must compensate. Especially, use of equalizer is need absolutely as data rate becomes high speed. In this paper, we analyze the BER performance with pre-equalization for MIMO-OFDM over fading channel. The results of this paper can be applied to MIMO-OFDM system with equalization.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.397-400
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• 2002

In this paper, a novel noncoherent multiuser detector with diversity reception for a differentially encoded DS/CDMA signal in a frequency-selective Rayleigh fading channel is proposed. The proposed receiver employs multipath decorrelator and decision feedback differential detector (DFDD) with diversity reception. DFDD performs differential encoding and diversity combining. The performance is obtained by analysis and simulation and it is sown that the proposed receiver outperforms conventional differential receiver with slight increase of complexity.

• Journal of electromagnetic engineering and science
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• v.12 no.2
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• pp.142-147
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• 2012

In this paper, we propose a novel protocol called Cooperative Multi-hop transmission using Incremental Relaying (CMIR). We evaluate the performance of the CMIR protocol by deriving expressions for the average end-to-end outage probability and the average number of transmissions. Monte Carlo simulations are presented to verify the accuracy of the theoretical analyses.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1240-1243
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• 2016

In this paper, we analyze the queueing performance of cumulative distribution function (CDF)-based opportunistic scheduling over Nakagami-m Markov fading channels. We derive the formula for the average queueing delay and the queue length distribution by constructing a two-dimensional Markov chain. Using our formula, we investigate the queueing performance for various fading parameters.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.4
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• pp.288-291
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• 2002

We characterize multipath fading channel dynamics at the packet level and analyze the corresponding data queueing performance in various environments. We identify the similarity between wire-line queueing analysis and wireless network per-formance analysis. The second order channel statistics, i.e. channel power spectrum, is fecund to play an important role in the modeling of multipath fading channels. However, it is identified that the first order statistics, i.e. channel CDF also has significant impact on queueing performance. We use a special Markov chain, so-called CMPP, throughout this paper.

• ETRI Journal
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• v.20 no.1
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• pp.16-27
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• 1998

In this paper, we consider the acquisition performance of an IS-95 reverse link access channel slot as a function of system design parameters such as postdetection integration length and the number of access channel message block repetitons. The uncertainty region of the reverse link spreading codes compared to that of forward link is very small, since the uncertainty region of the reverse link is determined by a cell radius. Thus, the parallel acquisiton technique in the reverse link is more efficient than a serial acquisition technique in terms of implementation and of acquisition time. The parallel acquisition is achieved by a bank of N parallel I/Q noncoherent correlator are analyzed for band-limited noise and the Rayleigh fast fading channel. The detection probability is derived for multiple correct code-phase offsets and multipath fading. The probability of no message error is derived when rake combining, access channel message block combining, and Viterbi decoding are applied. Numerical results provide the acquisition performance for system design parameters such as postdetection integration length and number of access channel message block repetitions in case of a random access on a mobile station.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.3
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• pp.1047-1062
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• 2018

In this paper the problem of massive multiple input multiple output (MIMO) channel estimation with sparsity aware adaptive algorithms for $5^{th}$ generation mobile systems is investigated. These channels are shown to be non-stationary along with being sparse. Non-stationarity is a feature that implies channel taps change with time. Up until now most of the adaptive algorithms that have been presented for channel estimation, have only considered sparsity and very few of them have been tested in non-stationary conditions. Therefore we investigate the performance of several newly proposed sparsity aware algorithms in these conditions and finally propose an enhanced version of RZA-LMS/F algorithm with variable threshold namely VT-RZA-LMS/F. The results show that this algorithm has better performance than all other algorithms for the next generation channel estimation problems, especially when the non-stationarity gets high. Overall, in this paper for the first time, we estimate a non-stationary Rayleigh fading channel with sparsity aware algorithms and show that by increasing non-stationarity, the estimation performance declines.