• Journal of information and communication convergence engineering
• /
• v.5 no.4
• /
• pp.333-338
• /
• 2007

In this paper we propose a new structure of the long code MMSE receiver with pilot channel, which maintians excellent symbol detection capability even in the presence of Rayleigh fading. We explain analytically how the stability of the receiver weight vector, which is critical to the system performance, can be achieved by compensating the error signal as well as received signal vector distorted by fading channel. Computer simulation shows while maintaining better performance than the conventional matched filter receiver, the proposed long code MMSE receiver can extend its period up to $16{\times}T_b$ in a fading environment.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.8A
• /
• pp.1156-1162
• /
• 1999

In this paper, the problem of decoding transmitted data sequence with diversity reception in the presence of nondelective fading is studied. The expection maximizaton (EM) algorithm is employed to derive an interactive algorithm. The algorithm performs block-by-block coherent decoding with the aid of pilot symbols. It is shown that the complexity of the algorithm grows linearly as a function of sequence length. The performance of the algorithm is shown to better than that of the conventional pilot symbol aided (PSI) algorithm. Simulation results are presented to assess the performance of the algorithm and the results are compared with that of the conventional PSI alforithm.

• Proceedings of the IEEK Conference
• /
• 2001.06a
• /
• pp.109-112
• /
• 2001

Recently, as demands for super-high speed broad band wireless multimedia service increase, variable researches to develop wireless LAN have been carried out. In this paper, we propose and analyze LS(Least Squares)-PSA(Pilot Symbol Assisted) equalizer which compensates for each subcarrier of different attenuations and phase response for OFDM(Orthogonal Frequency Division Multiplexing)-based indoor wireless LAN systems. The proposed equalizer enhances the $E_{b}$ $N_{o}$ performance of 3dB and 4dB at BER=10$^{-2}$ as compared with LS equalizer in AWGN channel and indoor wireless channel respectively..

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 2004.11a
• /
• pp.64-64
• /
• 2004

• The KIPS Transactions:PartC
• /
• v.12C no.5 s.101
• /
• pp.665-672
• /
• 2005

We present a novel pilot-aided channel estimation method for OFDM (Orthogonal Frequency Division Muitiplexing) system using WT(Wavelet transform) and interpolation. Due to excellent AWGN (Additive White Gaussian Noise) cancellation capability of n, pilot channels are estimated quite exactly and then, Dey are used in 2-degree polynomial interpolating the other remaining data symbol channels. The simulation results for Short WATM (Wireless Asynchronous Transfer Mode) channel show that the degradation in BER (Bit Error Ratio) performance of OFDM system iか this estimator is negligible compared to the case of perfect knowledge of CSI (Channel State Information).

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.2A
• /
• pp.43-50
• /
• 2005

In this paper, we present an improved channel estimation method for orthogonal frequency division multipexing systems using pilot symbol assisted modulation(PSAM). Conventional linear minimum mean square error(LMMSE) channel estimation method uses only pilot symbols for channel estimation. So, as the fading channel varies rapidly, the system performance is degraded. The basic idea of the proposed scheme is that we firstly estimate channel coefficients at the middle point between two pilot symbols and then compute the channel attenuation by using LMMSE method. Superior performance achieved with the proposed method is illustrated by simulation experiments with the Doppler frequency of 36Hz and 185Hz in comparison with conventional LMMSE channel estimator.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.6C
• /
• pp.554-561
• /
• 2010

This paper proposes an integer frequency offset estimation scheme robust to timing offset for the orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems. The proposed scheme exploits a feature that a sample distance between a continual pilot and a scattered pilot nearest to it in an OFDM symbol belongs to one of predetermined distances. First after calculating a correlation value of every continual pilot and its nearest scattered pilot. Then, it is divided into several groups according to the sample distances. Since correlation values with the same sample distance undergo the same effect of the timing offset, the effect of the timing offset can be removed by re-correlating these correlation values. From the simulation results we can confirm that the proposed algorithm estimates the integer frequency offset with the robustness to the timing offset when compared to a conventional scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.1 s.116
• /
• pp.53-61
• /
• 2007

This paper researches on the scheme superimposing the rotation phases over the pilot and data symbols in order to reduce the peak-to-average power ratio(PAPR) of the orthogonal frequency division multiplexing(OFDM) communication. The bandwidth and power efficiency are the main consideration. The phases of rotation vector are added to those of both pilot symbols and data symbols interlaying between any two pilot symbols in an OFDM block. Owing to this scheme the transmitter reduces the PAPR using the partial transmit sequences(PTS) and the receiver restores the data symbol utilizing the channel estimation of pilot symbols. Therefore, the bandwidth efficiency is accomplished by not using the further subcarriers for the reduction of PAPR and the enormous increase of bit error rate according to the receiving error of the side information, i.e. the phases of rotation vector, is prevented. In other words, both bandwidth-and power-efficiency and quality of communication performance can be improved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.7
• /
• pp.1128-1138
• /
• 2000

This paper presents two different approaches for channel estimation of IMT-2000 pilot symbol-assisted W-CDMA reverse link over Rayleigh fading channels of one and two paths. By obtaining BER performance through computer simulations, the proposed algorithms of 2-point second-order interpolation and IDD BWMA are compared with the performance of existing interpolation and adaptive algorithms. The BER performance of the proposed algorithms is superior to WMSA, linear and second-order Gaussian interpolation, LMS, and RLS algorithm in fast fading channels. In particular, the BER performance of the IDD BWMA algorithm is nearly insensitive for Doppler frequency within simulation range $E_b/N_0$ = 28 dB. The two proposed algorithms also have relatively simple structure and similar processing delay in comparison to the existing algorithms. Therefore, these algorithms are more suitable for high-speed mobile communication environments.

• The Journal of the Korea Contents Association
• /
• v.9 no.5
• /
• pp.84-90
• /
• 2009

In this paper, the new channel estimation was proposed that have the low complexity and high performance using Fuzzy inference method uses recently from various field for estimation about uncertainty in channel estimation of OFDM. Proposed method is channel estimation performance improve, calculation and interpolation for statistics character of channel using the pilot before LS channel estimation by Fuzzy inference method. Simulation result in QPSK proposed channel estimation method shows the enhancement of 5.5dB compared to the LS channel estimation and the deterioration of 1.3dB compared to the MMSE channel estimation in mean square error point $10^{-3}$. symbol error rate shows similarity performance the MMSE $10^{-1.96}$, proposed channel estimation $10^{-1.93}$ and enhancement of $10^{-0.35}$ compared to the LS channel estimation in signal to noise ratio point 20dB.