• Journal of Navigation and Port Research
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• v.36 no.3
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• pp.169-173
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• 2012

In this paper, we propose an equalizer to minimize the inter-symbol interference when PSSK(Phase Silence Shift Keying) technique is applied to the low power underwater acoustic communication. PSSK is a QPSK(Quadrature Phase Shift Keying) modulation combined with PPM(Pulse Position Modulation), and it was proposed for low power communication. However, it has poor performance due to delay spread of underwater channel. In this paper, we propose a decision feedback equalizer to minimize the error in PSSK receiver. The sea trial was performed to evaluate the performance of the proposed method. In the result, the BER of PSSK was $4.36{\times}10^{-2}$ before the equalizer was applied, but the BER of PSSK was $3.95{\times}10^{-4}$ after the proposed equalizer was applied.

• Journal of information and communication convergence engineering
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• v.14 no.2
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• pp.78-83
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• 2016

In underwater acoustic communication, the transmitted signals are severely influenced by the reflections from both the sea surface and the sea bottom. As very large reflection signals from these boundaries cause an inter-symbol interference (ISI) effect, the communication quality worsens. A channel estimation-based equalizer is usually adopted to compensate for the reflected signals under the acoustic communication channel. In this study, a feed-forward equalizer (FFE) with the least mean squares (LMS) algorithm was applied to a quadrature phase-shift keying (QPSK) transmission system. Two different types of equalizers were adopted in the QPSK system, namely a real-coefficient equalizer and a complex-coefficient equalizer. The performance of the complex-coefficient equalizer was better than that of two real-coefficient equalizers. Therefore, a Hilbert transform was applied to the real-coefficient binary phase-shift keying (BPSK) system to obtain a complex-coefficient BPSK system. Consequently, we obtained better results than those of a real-coefficient equalizer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1155-1163
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• 2010

An algorithm of the conventional wavelet shift keying is carried out that the scaling function and wavelet are encoded to 1(mark) and 0(space) for the input binary data, respectively. Two bit modulation technique which uses four carrier frequencies is existed. Four carrier frequencies are defined as scaling function, inversed scaling function, wavelet, and inversed wavelet, which are encoded to 10, 11, 00 and 01, respectively. In this paper, we defined 4-ary SWSK (4-ary scaling wavelet shift keying) which is two bit modulation, and it is derived to the probability of bit error and symbol error of the defined system from QPSK. In order to analyze to the performance of 4-ary SWSK, we are obtained in terms of the probability of bit error and symbol error for QPSK (quadrature phase shift keying), MFSK(M-ary frequency shift keying) and proposed method. As a results of simulation, we confirmed that the proposed method was superior to the performance in terms of the probability of bit error and symbol error.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.303-307
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• 2003

In this paper, the W(ultra widebend) system is used for high speed transmission applying BPSK(Binary Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying), and utilizing the convolution coding with code rate, 1/2 and constraint length, K=7 in order to reduce the bit error rate. And the performance of system is analyzed in the AWGN(Additive White Gaussian Noise) channel environment by using the Viterbi decoding algorithm and adopting the time-hopping sequence as a multiple access method in order to avoid the multiuser interference.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.1
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• pp.58-62
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• 2000

We Propose modulation scheme using I-Q modulation for transmitting different information simultaneously. For transmitting 1bit of each information, we apply QPSK scheme, for more bits, MAPSK. At the second modulation stage, We mix PN wavefoms with APSK waveforms for spreading bandwith. BER(Bit Error Rate) of each Information of the proposed scheme is analyzed on computer simulation. Finally we show power spectrum before and after spreading bandwidth.

• ETRI Journal
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• v.28 no.6
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• pp.793-795
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• 2006

When quadrature error exists, the shape of the M-ary phase shift keying (MPSK) signal constellation becomes skewed-elliptic. Each MPSK symbol takes on a different symbol error probability (SEP) value. The analytical results presented thus far have been derived from studies which examined the SEP problem assuming that the SEP of each MPSK symbol is equally likely; therefore, those results should not be treated as offering a complete solution. In this letter, we present a new and more complete solution to the SEP problem of MPSK by relaxing the above assumption and finding the expressions for the average as well as individual SEP in the presence of quadrature error.

• Journal of Navigation and Port Research
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• v.35 no.10
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• pp.811-816
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• 2011

In this paper, we analysis to consider the performance of PSPM (Phase Shift Pulse-position Modulation), the one of the low power communication technique, in near-field underwater sound channel by sea trial. PSPM is a QPSK(Quadrature Phase Shift Keying) modulation combined with PPM(Pulse Position Modulation) for low power communication in WBAN(Wireless Body Area Network). It is known that the bandwidth efficiency of PSPM is lower than conventional PSK but the power efficiency increases. In this paper, we will analyze the BER performance of PSPM using data acquired from the sea trials. The BER of QPSK was $6.04{\times}10^{-2}$, PSPM was $3.5{\times}10^{-1}$. Also, PSNR of QPSK was 9.37 dB and in case of PSPM was 9.11 dB.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1990.10a
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• pp.47-51
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• 1990

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.304-308
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• 2009

This paper proposes a new concept of a signal constellation of the recently introduced half-symbol-rate-carrier phase-shift keying (HSRC-PSK) modulations for bandwidth-efficient high speed data communications. Since the HSRC-PSK modulations contain different symbol energies representing the same bit sequences due to the loss of orthogonality of their HSRC signals, it is very hard to represent the symbol using the conventional signal constellation. To resolve the problem, two different energies are assigned to represent one symbol for the HSRC offset quadrature phase shift keying (OQPSK) modulation. Similarly, the different energies exist to display the different symbol for HSRC minimum shift keying (MSK) modulation. With the proposed signal space representation, HSRC-PSK symbol can easily be shown with a two-dimensional scatter plot which provides helpful information of evaluating HSRC-PSK signal's quality.

• ETRI Journal
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• v.29 no.6
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• pp.707-715
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• 2007

In-phase/quadrature (I/Q) imbalances, which are generated by non-ideal transceiver components, are inevitable physical phenomena that cause the performance of practical communication systems to be degraded. In this paper, we provide a new closed-form expression for the bit error rate of hierarchical M-ary phase shift keying with I/Q phase and amplitude imbalances and analyze the effect of I/Q imbalances on BER performance over an additive white Gaussian noise channel.