• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.144-149
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• 2016

In this paper, we analyze a QPSK MODEM over underwater acoustic channel model. Ambient noises and parameters of underwater environments debase the BER performance of an underwater modem. In the paper, the BER performance of uncoded QPSK and rate-2/3 convolutional coded QPSK is analyzed. And To improve BER Performance, we apply a channel equalization technique to the underwater modem.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.1
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• pp.7-13
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• 2011

A mixed-mode QPSK demodulator for 60-GHz wireless personal area network application is demonstrated. In this work, mixed-mode QPKS demodulation scheme achieving low power consumption and small area is employed. The prototype chip realized by 60-nm CMOS Logic process can demodulate up to 4.8-Gb/s QPSK signals at 4.8-GHz carrier frequency. At this carrier frequency, the demodulator core consumes 54 mW from 1.2-V power supply while the chip area is $150{\times}150{\mu}m^2$. Using the fabricated chip, transmission and demodulation of 1.7-GSymbol/s QPSK signal in 60-GHz link is demonstrated.

• Journal of Korea Society of Industrial Information Systems
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• v.8 no.1
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• pp.83-91
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• 2003

High-speed QPSK demodulator has been in important design objective of any wireless communication systems, especially those offering broadband multimedia service. This paper describes all-digital QPSK demodulator for high-speed wireless communications, and its hardware structures are discussed. All-digital QPSK demodulator is mainly composed of symbol time circuit and carrier recovery circuit to estimate timing and phase-offsets. There are various schemes. Among them, we use Gardner algorithm and Decision-Directed carrier recovery algorithm which is most efficient scheme to warrant the fast acquisition and tacking to fabricate FPGA chip. The testing results of the implemented onto CPLD-EPF10K100GC 503-4 chip show demodulation speed is reached up to 2.6[Mbps]. If it is implemented a CPLD chip with speed grade 1, the demodulation speed can be faster by about 5 times. Actually in case of designing by ASIC, its speed my be faster than CPLD by 5 times. Therefore, it is possible to fabricate the all-digital QPSK demodulator chipset with speed of 50[Mbps].

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1248-1255
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• 2003

High-speed QPSK demodulator has been one important design objective of any wireless communication systems, especially those offering broadband multimedia service. This paper describes Zero-Crossing IF-level(ZCIF) QPSK demodulator for high-speed wireless communications, and its hardware structures are discussed. ZCIF QPSK demodulator is mainly composed of symbol time circuit and carrier recovery circuit to estimate timing and phase-offsets. There are various schemes. Among them, we use Gardner algorithm and Decision-Directed carrier recovery algorithm which is most efficient scheme to warrant the fast acquisition and tracking to fabricate FPGA chip. The testing results of the implemented onto CPLD-FLEX10K chip show demodulation speed is reached up to 2.6［Mbps］. Actually in case of designing by ASIC, its speed may be faster than CPLD by 5 times. Therefore, it is possible to fabricate the ZCIF QPSK demodulator with speed of 10 Mbps.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.517-522
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• 2004

In this paper, we have analyzed the performance enhancement of Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio(OFDM/QPSK-DMR) system using Band Limited-Pulse Shaping Filter(BL-PSF) over microwave channel environments. For performance enhancement, the one-tap adaptive equalizer is adopted in the OFDM/QPSK-DMR system and than both BER and signature curve performance are compared with those of single carrier DMR system. Computer simulations confirm that the OFDM/QPSK-DMR system using 16 sub-carrier increase the fade margin about 2 dB over microwave channel environments and that of performance using one-tap adaptive equalizer is highly increased the fade margin as the number of sub-carriers is larger.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.587-592
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• 2020

The giant information exchange enabled by the Internet of Things paradigm will likely exploit electrical lines as a ready-to-use infrastructure. The advantage of using the pre-installed infrastructure of wiring networks makes power line communication a competitive technology for broad-band communications. Therefore, there has been a growing interest towards the use of existing power line communication channels as an effective means for transmitting high speed data and Internet service. One of the main noise types affecting power line communication systems is the impulsive noise, and the focus of this work is on the impact of this impulsive noise on the performance of OFDM-QPSK systems. For the performance analysis of impulsive noise, data measured in three environments were used. Through the analysis, it is shown that OFDM-QPSK system outperforms QPSK system for most of the impulsive noise cases. Also, RS-coded OFDM-QPSK system can achieve good BER performance under 3 cases impulsive noise environment.

• Journal of the Korea Society of Computer and Information
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• v.3 no.2
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• pp.155-160
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• 1998

We applied a pilot symbol assisted modulation technique to QPSK system for improving BER performance over mobile communication channel. We demonstrate through computer simulation, that the proposed scheme achieves a prominent improvement comparison to that of conventional QPSK in a fast flat Rayleigh fading environment.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.39-44
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• 2012

In this paper, we studied a high speed Trellis Coded Modulation (TCM) system and 8PSK-TCM system, and compare 8PSK-TCM system with QPSK system of BER. We know that 8PSK-TCM had 3 db improvement of BER than QPSK. And we demonstrated the superiority of 8PSK-TCM by simulating with Matlab. Input signal was 2 bits long, and 8PSK-TCM used 3bits long. Results of this simulation said that 8PSK-TCM had 3 db improvement of BER than QPSK.

• The Journal of the Korea Contents Association
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• v.9 no.2
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• pp.10-17
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• 2009

This paper analyze the effect of frequency offset for the IEEE 802.15.4b LR-WPAN(Low-Rate Wireless Personal Area Network) with 915MHz bandwidth noncoherent DSSS O-QPSK based receiver system, and presents a compensation method with addition of differential filter to the system for compensation of frequency offset problem. DSSS PSSS-ASK and DSSS O-QPSK modulation techniques are accepted within the regularization of IEEE 802.15.4b. These new method can obtain 250kbps transmission rate. The DSSS O-QPSK modulation method that is used in this paper has no BER variation below 40ppm(frequency offset 36.6kHz), but if the offset frequency become high above 40ppm, then the system cannot have stable receiving condition due to worse BER. To solve this problem, we present a more stabilized receiver system at maximum frequency offset ${\pm}80ppm$ using MDDF unti a correlator of DSSS O-QPSK modulator. Moreover computer simulation results will be presented to evaluate the performance of the proposed algorithm unde various AWGN and frequency offset environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.1019-1026
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• 1996

A modulation type classifier based on statistical moments has been successfully employed to classify PSK signals. Previously, developed Classifiers were analyzed in AWGN channel only. In this paper, a moments-based modulation type classifier to classify BPSK and QPSK signals over Rayleigh fading channel is proposed and analyzed. The moments of received signal are evaluated with the exact distribution of the received signal and a moments-based classifier is proposed. The performance evaluation of the proposed classifier in terms of the misclassification probability for BPSK and QPSK is investigated under Rayleigh fading environment.