• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.49-56
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• 2010

Severe energy constraints and the low power consumption require the significance of the energy efficient error control mechanisms in wireless sensor network (WSN). In this paper, an automatic repeat request (ARQ) methodology for the analysis of error control schemes in WSN is presented such that the effects of packet length, the modulation scheme and the interference effect of the wireless channel are investigated. Moreover, an analyis of ARQ error control is provided by considering two major architectures for wireless sensor network, i.e., Mica2 and MicaZ sensor nodes. And the throughput performance of WSN with asynchronous FSK signal and DSSS-OQPSK signal with selective repeat ARQ scheme are analyzed in multiple interference environment, and the probability of receiving a correct bit and packet from target node to sink node is evaluated as a function of the channel parameter, the number of wireless sensor node, and the spreading factor.

• Journal of the Korea Society of Computer and Information
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• v.11 no.3
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• pp.271-279
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• 2006

This study proposes a new diversity algorithm to improve the signal-to-noise ratio. In the wireless channel, if fading occurs due to the multipaths, the performance of the system is apparently reduced. One of the methods to reduce fadings like this is the diversity method, and this study aims to improve the performance of the system by proposing a new diversity algorithm. This study applied rake receiver It applied QPSK and OQPSK modulation methods and applied the convolutional codes, where the code rate is 1/3 and the constraint length is 9, and the turbo code where the constraint length is 4. Under these conditions, this study compared and analyzed the average error probability of Multicarrier CDMA system.

• Journal of information and communication convergence engineering
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• v.7 no.2
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• pp.152-156
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• 2009

This paper examines the BER performance of the recently proposed half-symbol-rate-carrier (HSRC) offset quadrature phase-shift-keying (OQPSK) receiver for high-speed data communication. A modified demodulation technique using a bit-time period signal integration, the bit-error-rate (BER) performance of the HSRC-OQPSK signal improves more than 4dB compared to that of a demodulation technique using a symbol-time period integration. This paper also examines the BER performance of modified demodulation with various band-limited channels modeled using low-pass filters, and the three different data-rate systems are simulated and compared with the performance of the system using the conventional demodulation technique.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.303-304
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• 2008

In this paper, the performance of DSSS OQPSK architecture for 868/915MHz LR-WPAN(Low-Rate Wire less Personal Area Network) is analyzed. Since the frequency offset of ${\pm}40ppm$ on 868/915MHz band is recommended in IEEE 802.15.4 LR-WPAN specification. it is required to have a non-coherent detection that is stable operation in the channel environment with large frequency offset is required.

• Journal of the Korea Society of Computer and Information
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• v.11 no.3
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• pp.213-219
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• 2006

Interference occurs by signals received from directions that were different from the signals of the users in a mobile communication system. Various studies have been undertaken, including diversity, equalizer, etc., in order to reduce interference. In this study, the weighted value of the array antenna was obtained to improve signal-to-noise ratio. The weighted value was obtained as an eigen value and an eigen vector by using the correlation coefficient of the signal. The weighted value obtained was then applied to the CDMA system to increase system performance and capacity. Both QPSK and OQPSK modulation systems were applied to analyze performance.

• Journal of Navigation and Port Research
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• v.36 no.5
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• pp.371-378
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• 2012

This paper presents a timing recovery method using Gardner TED (Timing Error Detector) with a Peak Detector using Parabola Peak Interpolation in underwater acoustic communication. This method will have an eye to improve phase converge speed of timing recovery and reduced amount of Tx data. The OQPSK(Offset Quadrature Phase Shift Keying) modulation technique was considered. The proposed algorithm has faster recovery speed and more accurate than Gardner TED because the sampling values in the proposed algorithm are moved persistingly to maximum or minimum point using parabolic peak interpolation. when simulation performed using Preposed method, it improved BER (Bit Error Rate) performance about 23% And to evaluate the performances of the proposed algorithm the sea trial was performed in the Korean East Sea. And distance of a transmitter-receiver is 3 km each other. As a result, the proposed algorithm outperforms better BER performance about 20% of timing recovery than the Gardner method. Also Proposed method improved converge speed of timing recovery about 1.4 times better than Gardner method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.594-599
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• 2001

The symbol rate which is the main feature of NRZ information signal is detected by DAM (Delay-And-Multiplier) receiver. It is important for secure communication to reduce the normalized output SNR which is calculated at the DAM output as a measure of detectability. In this paper, we use the signal which is modulated by the class of MSK modulation schemes as the input signal of the DAM receiver for analyzing LPI performance and the GMSK(BT=0.3) used in GSM system is highlighted. Consequently, GMSK which has better bandwidth efficiency than other modulation schemes(BPSK, QPSK, OQPSK, and MSK) has better LPI performance compared with other ones. To compare the performances of each modulation scheme fairly, the transmitted powers of each system are set to be same within useful bandwidth.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.368-377
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• 1999

In this paper, the wide-band CDMA transmitter for 2 GHz band is designed and implemented. The CC-OQPSK implemented as ASIC has better spectral and power efficiency than the conventional QPSK system because it has constant envelope characteristics. Good harmonics rejection characteristics and gain of 20 dB are shown on the intermediate frequency stage using double-conversion scheme. The output power of two-stage RF amplifier is +2l.14 dBm in 1.9 GHz band. It is confirmed that the electrical characteristics of the transmitter satisfy with required the specification of the wide-band CDMA transmitter for 2 GHz band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.519-529
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• 1993

A spectral and power efficient modulation technique, named Compact Superposed Quadrature Amplitude Modulation (Compact-SQAM), is introduced. The performance of Compact-SQAM system, in a Linearly and nonlinearly amplified single and multicarrier environment, in the presence of additive white Gaussian noise(AWGN), intersymbol interference(ISI), timing jitter and adjacent channel interference (ACI), is experimentally analyzed via computer simulation. Various channel conditions, such as channel spacing, between the main and adjacent channels and fade depth on the desired main channel, are examined. Our result shows that Compact-SQAM, and better P(e) performance that other modems using simple Butteroworth type postdetection receive filters. Especially, Compact-SQAM modem achieves higher efficiency of frequency utilization and better P(e) performance than other modems in the severly bandlimited nonlinear multicarrier channels.

• The Journal of the Acoustical Society of Korea
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• v.10 no.4
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• pp.19-26
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• 1991

$GQ^2PSK$ which is a novel digital mobile communication modulation scheme has been introduced and described. $GQ^2PSK$ is a modulation scheme that bandlimits NRZ digital data with Gaussian filter and modulates it by $Q^2PSK$ scheme which uses two shaping pulses and two carriers which are pairwise quadrature. Thus transmission bit rate can be enhanced and available signal space dimensions are more efficiently utilized, with comparison to the already-existing GMSK, QPSK and OQPSK modulation methods. Via the computer simulation, bit error rate of $GQ^2PSK$ scheme which is bandlimited by gaussian filter to be suitable for digital mobil communication, is lower than that of $Q^2PSK$ by 1.4[dB] in case that the signal-to-noise ration is 0[dB], but we have confirmed that $GQ^2PSK$ modulation scheme is approximately equivalent to the GMSK in the respect of power efficiency, and transmission efficiency of $GQ^2PSK$ is improved to 1.5 times than that of GMSK.