• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.185-193
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• 2007

This paper evaluates the performance combining space-time transmit diversity (STTD) and an efficient channel estimator (ECE) for wideband code division multiple access (WCDMA) systems in various mobile channels. Using decision variable (DV), we also derive the analytic bit error rate (BER) and mean square error (MSE) for WCDMA applying ECE for STTD schemes. The simulation results show that the ECE performance is superior to the previous works in [1] as because we use additional pilot diversity which is so called secondary common control physical channel (S-CCPCH). The performance in case of the channel estimator using only one-channel or two-channel is worse than that of an ECE as about the maximum 4 dB at BER 1.0E-3 satisfying voice service over Rician fading channel. Our results show that, even with ICE, an ECE algorithm are effective in improving the output SNR and significantly reduce the error floor. In addition, the simulation results investigated in this paper also reveal that WCDMA combining an ECE and the STTD scheme could provide appreciable performance improvements in Rayleigh fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.11
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• pp.1626-1634
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• 1993

In this paper we propose a coding scheme which combines source codes and error correcting codes in order to be robus to channel noise. One of the coding schemes that take into account both the source and the channel is the channel optimized quantizer (COQ) which simultaneously minimizes quantization noise and the noise due to channel errors. This paper deals with the problem of combining channel optimized quantizers with ECC to build an improved system. To be specific, we computed the performance of an n bit COQ and that of an n-1 bit COQ followed by an (n-1)/n punctured convolutional code. From this result whether or not the ECC are selected is determined by the number of allocated bits and the channel bit error rate. These results are applied to the image trans-mission method using DCT, and the system performances are evaluated.

• ETRI Journal
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• v.32 no.1
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• pp.139-141
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• 2010

In this letter, closed-form approximations for outage probability and symbol error rate are presented for a selective decode-and-forward relay network with partial channel information. An independent but not identically distributed Rayleigh fading environment is considered. Numerical and simulated results demonstrate the validity of the analytical results.

• Journal of Korea Society of Digital Industry and Information Management
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• v.7 no.3
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• pp.107-113
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• 2011

An OFDMA(Orthogonal Frequency Division Multiple Access) includes a MIMO(Multi-Input Multi-Output) scheme for improving spectral efficiency and data throughput. Recognizing that the performance of MIMO system is heavily dependent upon the accuracy of channel estimation, we propose a novel channel estimation for the MIMO scheme based on OFDMA. Conventional interpolation-based channel estimation suffers from poor estimation error at specific subcarriers. Proposed scheme makes use of a planar interpolation instead of linear interpolation for those subcarriers of bad accuracy. Simulation results show that the proposed scheme improves the performance of MIMO system by improving the accuracy in channel estimation especially for the adverse subcarrier positions. It is observed that the proposed scheme outperforms the conventional method by about 2dB in terms of both mean squared error and overall bit error rate with a reasonable computational complexity.

• ETRI Journal
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• v.28 no.5
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• pp.684-687
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• 2006

In this letter, we evaluate the system performance of a space-time block coded (STBC) multicarrier (MC) DS-CDMA system over a time selective fading channel, with imperfect channel knowledge. The average bit error rate impairment due to imperfect channel information is investigated by taking into account the effect of the STBC position. We consider two schemes: STBC after spreading and STBC before spreading in the MC DS-CDMA system. In the scheme with STBC after spreading, STBC is performed at the chip level; in the scheme with STBC before spreading, STBC is performed at the symbol level. We found that these two schemes have various channel estimation errors, and that the system with STBC before spreading is more sensitive to channel estimation than the system with STBC after spreading. Furthermore, derived results prove that a high spreading factor (SF) in the MC DS-CDMA system with STBC before spreading leads to high channel estimation error, whereas for a system with STBC after spreading this statement is not true.

• Journal of Communications and Networks
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• v.14 no.2
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• pp.199-205
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• 2012

This work investigates the progressive linear precoder design for packet retransmissions in multi-input multi-output (MIMO) systems with multiple codewords and automatic repeat request (ARQ) bundling feedback. Assuming perfect channel state information, a novel progressive linear ARQ precoder is proposed in the perspective of minimizing the packet error rate. We devise the ARQ precoder by combining power loading and sub channel pairing between current retransmission and previous transmissions. Furthermore, we extend the design to the case that the channel estimation error exists. Numerical results show that the proposed scheme can improve the performance of MIMO ARQ systems significantly regardless of the channel estimation error.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.165-168
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• 2000

The bit error rate(BER)of the data passed through Wideband-Code Division Multiple Access (W-CDMA) system with turbo-codes structure is presented. The performance of turbo-codes under W-CDMA system is estimated for various users and iteration numbers of decoding. The channel model is Additive White Gaussian Noise(AWGN) and Rayleigh fading channel. When iteration number increases, bit error probability of turbo-codes decreases. and when the number of users increase, bit error probability of turbo-codes increases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.454-460
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• 2004

In this paper, we studied hierarchical channel coding scheme using unequal error protection method for consecutively broadcastingservice under the rain attenuation of Ka band satellite broadcasting. Unlike time-sharing methods, which are design for different channel coding scheme in according to different modulation, unequal error protection method is made in such way that minimum distance between signals are different for importance of signals with same modulation. Consequently we proposed optimal method according to performance analysis.

• Journal of Communications and Networks
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• v.9 no.4
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• pp.466-472
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• 2007

Single carrier block transmission with frequency domain equalization(SC-FDE) has been shown to be a promising candidate in ultra-wideband(UWB) communications. In this paper, we analyze the performance of SC-FDE over UWB communications with channel estimation error. The probability density functions of the frequency domain minimum mean-squared error(MMSE) equalizer taps are derived in closed form. The error probabilities of single carrier block transmission with frequency domain MMSE equalization under imperfect channel estimation are presented and evaluated numerically. Compared with the simulation results, our semi-analytical analysis yields fairly accurate bit error rate performance, thus validating the use of the Gaussian approximation method in the performance analysis of the SC-FDE system with channel estimation error.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.8
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• pp.63-68
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• 2004

The capacity of MIMO systems is numerically analyzed when channel estimation error exists. The analysis shows that the capacity is influenced by Mean Square Error (MSE) as well as average Signal to Noise Ratio (SNR). Furthermore, in this paper we present the standard selecting a channel estimator suitable to a system owing to get a tolerable channel estimation error in a given average SNR and channel capacity loss. The simulation results show that the tolerable MSEs for 1 bps/Hz capacity loss are about 10$^{-2}$ and 10$^{-4}$ at n dB and 40 dB average SNR, respectively.