• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.24-31
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• 2015

A differential codebook using M-ary phase shift keying (M-PSK) constellation as its codeword elements, is proposed for Long term evolution (LTE), LTE-Advanced (LTE-A), and/or WiMAX systems. Due to the temporal correlation of the adjacent channel, the consecutive precoding matrices are likely to be similar. This approach quantize only the differential information of the channel instead of the whole channel subspace, which virtually increase the codebook size to realize more accurate quantization of the channel. Especially, the proposed codebook has the same properties of LTE release-8 codebook that is, constant modulus, complexity reduction, and nested property. The mobile station can be designed by using a less expensive non-linear amplifier utilizing the constant modulus property. Computer simulations show that the capacity of the proposed codebook performs better than LTE release-8 codebook with the same amount of feedback information.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.2
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• pp.222-231
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• 2011

In this paper, we have proposed a method which can make it possible to stably transmit and receive data like the ARC-164 radio frequency hopping environment as a S/W packet modem with PSK modulation. This is a method that the S/W packet modem with PSK digital modulation and the use of PC sound cards change over from data to voice signals and then transmit/receive data. We confirmed not only that it is possible to solve the slow speed communication with the use of sending data through multi-channels and PSK modulation that has the ability to methodically improve transmission rates, but also that it is possible to send the state of frequency hopping stably. In conclusion, we've confirmed both tactical values that though the transmission rate may be a tad slow, a state of frequency hopping of more than 94% confidence plus voice and data can be sent via radio at the same time. In this paper, the proposed S/W packet modem is only an implemented S/W component, so when we apply it to aircraft that we don't consider EMC problems with, then we have the advantage of a wider use of conventional UHF/VHF/HF radio that is possible to voice communication. If we recognize these operational requirements, we can apply for a lot of field equipment efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7C
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• pp.678-687
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• 2003

8SQAM(8-state Superposed Quadrature Amplitude Modulation) being a new modem technique for use in power and bandwidth limited digital communication system generates output signals which have a mか and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitudes and phases of two subsequent symbols. Also, 8SQAM signal is free of inter-symbol interference(ISI), and has a compact power spectrum. Accordingly 8SQAM, as compared with a conventional 8PSK, is influenced a little by inter-modulation(IM), inter-symbol interference(ISI) and adjacent channel interference(ACI) in a nonlinearly amplified multi-channel(SCPC-FDMA) environment. In this paper, the performance of 8SQAM system in a nonlinearly amplified multi-channel interference environment is analyzed via computer simulation The simulation result shows that 8SQAM outperforms 8PSK with roll-off value of $\alpha$ = 0.3 by 2.7dB in CNR to maintain BER=1$\times$10$^{-4}$ when input back-off(IBO) of HPA is 1dB and channel space is 41.7% of the data bit rate(i.e., spectral efficiency = 2.40b/s/Hz).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7C
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• pp.669-677
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• 2003

A new Modem technique - 8SQAM(8-state Superposed Quadrature Amplitude Modulation) - for use in power and bandwidth limited digital communication system is proposed. 8SQAM is free of inter-symbol interference(ISI) and generates output signals which have a smooth and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitudes and phases of two subsequent symbols. Accordingly, 8SQAM, as compared with a conventional 8PSK, is influenced a little by ISI and inter-modulation(IM) caused by nonlinear distortions. In this paper, the performance of the 8SQAM system, in a nonlinearly amplified channel impaired by additive white Gaussian noise(AWGN), ISI and IM, is analyzed via computer simulation. The simulation result shows that 8SQAM outperforms 8PSK with roll-off value of $\alpha$=0.25 by 2.5dB in CNR to maintain BER=1$\times$10$^{-4}$ when input back-off(IBO) of HPA is 3dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.73-81
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• 2005

We propose an automatic modulation recognition scheme which extracts pre-defined key features from the received signal and then applies equal gain combining method to determine the used modulation. Moreover, we compare and analyze the performance of the proposed algorithm with that of decision-theoretic algorithm. Our scheme extracts five pre-defined key features from each data segment, a data unit for the key feature extraction, which are then averaged over all the segments to recognize the modulation according to the decision procedure. We check the performance of the proposed algorithm through computer simulations for analog modulations such as AM, FM, SSB and for digital modulations such as FSK2, FSK4, PSK2, and PSK4, by measuring recognition success rate varying SNR and data collection time. The result shows that the performance of the proposed scheme is comparable to that of the decision-theoretic algorithm with less complexity.

• The Journal of the Acoustical Society of Korea
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• v.26 no.7
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• pp.366-374
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• 2007

In underwater wireless communication, needs for long distance communication using the high frequency are surpassing ones of short range communication by ultrasonic wave, and demands for transmitting and receiving various data such as voice or high resolution image data are increasing as well. In this work, we studied the effects on the real underwater communication depending on the difference of digital modulation methods. Simulation shows that only the performance of GMSK among many other PSK based modulation schemes(BPSK, QPSK, MSK, GMSK) is significant. Test condition simulates the oceanographic conditions along the 207-survey line, 15Km south of Busan and SNR is maintained 35dB or below. Simulated tests are composed of both transmitting image data($3{\times}10^5$ pixel, 4 bit per pixel) and voice communication($10^{-2}$BER, channel capacity of 1Kbps). Test results show that there are gain of about 7 seconds in transmission time in image transmission case, where channel capacity for BPSK, QPSK, and MSK and for GMSK were 65 Kbps and 45 Kbps, respectively and gain of about 8Km in distances in voice communication case.

• Journal of IKEEE
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• v.16 no.1
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• pp.56-61
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• 2012

In this paper, a digital modem for the medical implant communication system will operate in 402~405 Mhz wide-band in international standardization frequency was designed and implemented. The ${\pi}$/4-D8PSSK modem, which is not only power effective with a good low-powered characteristics but also band-width effective, can overcome the shortcoming of PSK. The proposed digital modem was verified through the wave comparison based on the result of Matlab simulation and the wave from the measured one using Chipscope, and implemented with FPGA.

• Journal of Advanced Navigation Technology
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• v.13 no.3
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• pp.337-343
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• 2009

In this paper, we proposed a burst mode symbol timing recovery unit that is applicable to the VDL Mode-2 using D8PSK modulation. A method that IIR loop filter is used to minimize symbol timing error is hard to apply to burst mode because its convergence time is long. That is, the fast convergence property is important. In this paper, the proposed method takes one sample which has maximum symbol power after the initial synchronization has been achieved by using preambles. The main principle of operation is that the unit moves one sample clock to advance or retard according to symbol power. We verify that the proposed method is operated well in ${\pm}100$ ppm or greater through the test results between Australia ADS Corp. transmitter and the designed receiver.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.8
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• pp.2003-2012
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• 1996

The 16- and 32-state Trellis-coded M-ary 4-dimensional (4-D) orthogonal modulation scheme with a frequency-reuse technique have been investigated. Here, 5 coded bits form a rate 4/5 convolutional encoder provide 32 possible symbols. Then the signals are mapped by a M-ary 4-D orthogonal modulator, where each signal has equal energy and is PSK modulated. In the M-ary 4-D modulator, we have employed the vectors which is derived by the optimization technique of signal waveforms in a 4-D sphere. This technique is usedin maximizing the minimum Euclidean distance between a set of signal poits on a multidimensional sphere. By combinig trellis coding with M-ary 4-D modulation and proper set-partitioning, we have obtained a considerable impeovement in the free minimum distance of the system over an AWGN channel. The 16-state scheme obtains coding gains up to 5.5 dB over the uncoded two-independent QPSK scheme and 2.5 dB over the two-independent 2-D TCM scheme. And, the 32-state scheme obtains coding gains up to 6.4 dB over the uncoded two-independent QPSK schemeand 3.4 dB over the two-independent 2-D TCM scheme.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.89-92
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• 2001

In this paper, as a study of programmable software radio digital communication, we implemented ASK(Amplitude Shift Keying), FSK(Frequency Shift Keying), and PSK(Phase Shift Keying) modulation using programmable software(algorithm) of DSP(Digital Signal Processor). Moreover, it is possible to select one of those three modulation methods by realizing on single DSP. We adopted Motorola DSP56002 and Crystal CS4215(A/D and D/A converter) for our purpose. The DSP56002 is 24-bit and operates 20 MIPS at 40 MHz, and the CS4215 is 16-bit and supports the maximum 50 kHz sampling frequency.