• Journal of Satellite, Information and Communications
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• v.4 no.2
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• pp.34-38
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• 2009

This paper is related with optimum burst structure design for high efficient TDMA satellite return link transmission. In general, some typical burst structure for data transmission is composed of a pair of preamble and traffic data in the DVB-RCS (Digital Video Broadcasting. Return Channel via Satellite) and IPOS (IP over Satellite) standard. This structure has some difficulties to increase spectral efficiency that it requires a large of preamble length, high SNR environment, or receiver complexity. To cope with them, burst structure with distributed pilot symbol can be used to alleviate the residual frequency offset effect by calculating accurate frequency offset than conventional one. In particular, we investigate some relevant to proposed distributed pilot structure, previously and analyze their strong points/drawbacks in terms of synchronization to draw the most appropriate one.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.1
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• pp.61-67
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• 2011

The GPS new civil signal is modulated on the L2 carrier at a frequency of 1227.6MHz. The L2C signal is composed of two multiplexed code signals, which include CM code with a 10,230 chip sequency repeating every 20ms, and CL code which has a 767,250 chip sequency repeating every 1.5 seconds. Thus, the new civil signal have much improved cross correlation properties so that the position fixing can be possible even with very weak signals. However, it requires very long acquisition time because of its long code length. This paper presents an efficient signal acquisition method for L2C AGPS receiver. Snapshot mode and coarse time assistance are assumed and total integration time is given by 1.5 sec. By SNR worksheet and computer simulation, it is proven that L2C signal can be acquired with very weak power less than -150dBm. Considering the acquisition time and the sensitivity, it is recommended that the highest power signal is acquired with CM code first to reduce TTFF. By the timing synchronization, at this time, search space of the code phase for other signals can be greatly reduced so that CL code can be used in signal acquisition to maximize sensitivity with small computation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1699-1709
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• 2015

Moving terminals like high-speed-train undergo high Doppler frequency shift, and this leads to carrier frequency offsets that have to be compensated to avoid degradation of communication performance. In multiple access mechanism like OFDMA, base-stations need complex hardware to compensate the uplink frequency offset. In this paper, we propose a method, which can reduce burden of the base-station and makes frequency offset estimation and compensation simple. This method contains transmitting new synchronization signal, estimating frequency offsets in base-station, transmitting feedback information to terminal, and compensating the offset in uplink transmission. Simulation results show the proposed method operates well in high Doppler frequency shift conditions of 500 km/h which is the requirements of 5G mobile communication.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.754-757
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• 2007

In this paper, we present an implementation and it's real-sea test of an underwater acoustic data communication system, which allows the system to reduce complexity and increase robustness in time variant underwater environments. For easy adaptation to complicated and time-varying environments of the ocean, all-digital transmitter and receiver systems were implemented. For frame synchronization the CAZAC sequence was used, and QPSK modulation/ demodulation method with carrier frequency of 25kHz and a bandwidth of 5kHz were applied to generate 10kbps transmission rate including overhead. To improve transmission quality, we used several techniques and algorithms such as adaptive beamforming, adaptive equalizer, and convolution coding/Viterbi decoding. for the verification of the system performance, measurement of BER has been done in a very shallow water with depth of 8m at JangMok, Geoje. During the experiment, image data were successfully transmitted up to about 7.4km.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.49-56
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• 2006

This paper describes the design and the verification of IEEE 802.15.4 LR-WPAN 2.4GHz Physical layer for Ubiquitous Sensor Network(USN). We designed the Carrier Frequency Offset(CFO) compensation satisfied the frequency tolerance of IEEE 802.15.4 LR-WPAN and the adaptive matched filter that re-setting of the threshold for the symbol synchronization of the various USN environment. The multiplications is reduced 1/16 by this method each other at i, q phases and has 0.5dB performance improvement in detection probability. Proposed baseband system is designed with verilog HDL and implemented using FPGA prototype board.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.87-93
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• 2001

As a new type of a linear decorrelating receiver, the Pseudo-Decorrelator was presented for asynchronous code division multiple access systems by the author. In this paper, the concept of the Pseudo-Decorrelator is extended to derive a receiver for WCDMA uplink systems over an additive white Gaussian noise channel. Starting with the analysis of the multiple access components of the decision statistics, a non-square cross-correlation matrix for each bit is obtained. This cross-correlation matrix is then inverted, and the inverted matrix is applied to the decision statistics obtained from a conventional receiver. In this receiver, the detection process can be started after the first three consecutive bits are received. Simulation results are presented for K-user systems over an additive white Gaussian noise channel under the circumstances in which synchronization errors, including time delay errors and carrier phase errors exist. It is shown that the proposed receiver performs better than a conventional receiver and parallel interference canceller.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.991-997
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• 2004

In this paper, we propose the architecture of modem receiver to fabricate HomePNA 2.0 chip. HomePNA suffers from inferior channel because of bridge tap, the effect of amateur HAM band and so on. To transfer data over such channel, HomePNA 2.0 uses training sequence to equalize channel and uses FD-QAM optionally as modulation method. So modem receiver demodulate QAM based signal and needs optimum architecture that fully uses these transmission feature. As a result of research, we define 2 mode function of modem receiver depending on TX/RX state. In this paper, particularly, we show the algorithm of equalizer, carrier phase recovery and frame synchromzationblock and propose architecture that improve the performance of channel equalization and is stable in operation. In the end, we estimate the performance of proposed HomePNA2.0 modem receiver over HomePNA TEST LOOP using SPW program.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.1-8
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• 2006

In this paper, we propose carrier phase synchronization algorithm which are base on turbo coded system for DVB-RCS. There have been two categories of phase estimator, single estimator outside turbo code decoder and multiple estimators inside turbo code decoder. In single estimator, we use the estimation algorithm that ML(Maximum Likelihood) and LMS(Least Mean Square), also three different soft decision methods are proposed. Multiple estimator apply PSP(Per Survivor Processing) algorithm additionally. We compared performance between single estimator and Multiple estimator in AWGN channel. We presented the two methods of PSP algorithm for performance elevation. First is the Bi-directional channel estimation and second is binding method.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.401-412
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• 2005

We propose and design the algorithms of symbol timing recovery, carrier recovery, and equalization for the receiver of S-DMT cable modem, which supports more channels and better symmetric mutimedia services over HFC network. We evaluate the performance of the concatenated entire receiving system of 16QAM, 64QAM in the mixed noise channel of AWGN, ISI and impulse. The result of evaluation shows those algorithms work correctly and designed S-DMT receiver has good performance. We also verify the designed system has excellent immunity against impulse noise channel of practical Cable TV networks by the result of simulation with the parameters of impulse internal $\varepsilon$ and noise power $\gamma^{k}$.

• Journal of Power Electronics
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• v.18 no.1
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• pp.70-80
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• 2018

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.