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To increase the spectral efficiency of HFC network, the standard of digital video broadcasting for cable systems (DVB-C2) was completed in 2010 and products that support the DVB-C2 is expected to be released within years. Before making products for DVB-C2 receiver, the performance of them should be investigated under various channel conditions first. Thus, we show the performance of the proposed structure for a pre-FEC in DVB-C2 receiver considering the channel model including additive white Gaussian noise (AWGN), a frequency offset, and echo channels to provide information about the implementation of DVB-C2 receiver. Based on the simulation results, we implement the pre-FEC using two field programmable gate arrays (FPGAs) and show the measured symbol error rate (SER) between the transmitted and received quadrature amplitude modulation (QAM) symbols with respect to various symbol timing estimations (STEs) of synchronization (SYNC) and powers of analog-to-digital converter (ADC) input. Because the STE makes the received pilot symbols in preamble rotated and these rotated pilot symbols are used in channel estimation, it affects the channel estimation and SER of pre-FEC. In addition, the channel estimation impaired by the STE causes the received QAM symbols to have biased mean values compared with the transmitted 4096QAM symbols. Since this degrades the performance of pre-FEC, the automatic gain control (AGC) is added after zero-forcing linear equalizer (ZF-LE) to improve the performance of pre-FEC. As the power of ADC input decreases, the SER increases due to the noise enhancement of ZF-LE.

This paper describes the development of DSSS wireless communication uplink system for missile remote control. In consideration of low probability of intercept, low probability of exploitation, anti-jam, low latency, and doppler frequency offset, we used DSSS partially DBPSK. Also we used the selective diversity with two receiving antennas to mitigate multipath interference which is the dominant channel impairment and the turbo product code(TPC) for forward error correction(FEC) to improve bit error rate performance.

In this paper, we compare the performance of wavelet OFDM (Orthogonal Frequency Division Multiplexing) and FD-OFDM(Frequency diversity OFDM) system with conventional OFDM system. Wavelet OFDM system uses wavelet transform rather than Fourier transform and contains intermediate characteristics of CDM (Code Division Multiplexing) and OFDM. In wavelet OFDM system, inter-symbol interference (ISI) can be suppressed effectively and adjacent channel interference can be also minimized well. In FD-OFDM system, each parallel branch symbol is multiplied by the orthogonal sequence and distributed into all sub-carriers. Then, each sub-carrier transmits information composed of the symbol components of all parallel branches in the given frame. FD-OFDM contains the frequency diversity characteristic and, therefore, FD-OFDM can be robust to the narrowband interference. For the comparison among different systems, BER (Bit-Error Rate) performances are evaluated in the presence of narrow-band interference and a harmonic noise channel. From the evaluation results, compared to the conventional OFDM, wavelet OFDM and FD-OFDM shows better robustness against the interference and, especially, wavelet OFDM is the most robust in harmonic noise channel.

This paper presents the signal-to-interference plus noise ratio (SINR) estimation of IEEE 802.16m WirelessMAN-Advanced mobile station with simulation and implementation results. The downlink signal of IEEE 802.16m has two kinds of A-Preambles: the PA-preamble and the SA-preamble. This paper proposes the efficient method of estimating SINR with A-Preambles, by measuring noise power from PA-preamble and measuring interference power and signal power from SA-preamble. The proposed SINR measurement block contains important features such as subcarrier phase rotation elimination and simplified dB transform. The result of this paper is integrated to ETRI's IEEE 802.16m test mobile station, used for decision of adaptive-modulation-and-coding (AMC) and hand-over. It showed good measurement performance in simulation and unified system link test also.

A receiver of upstream cable modem (CM) for data over cable service interface specifications (DOCSIS) 3.0 is proposed and implemented in field programmable gate arrays (FPGAs). The receiver, which can demodulate four upstream channels simultaneously, consists of a digital down converter (DDC), a pre-forward error correction (FEC) and a FEC decoder. In DDC, fixed decimation and variable decimation with respect to symbol rate are used to remove adjacent channel images. An automatic gain control (AGC) uses a power calculation in a packet detection (PD) to reduce hardware complexity. Coefficients of symbol timing estimation (STE) use the sign of preamble symbols for eliminating multipliers. In addition, STE operates only for some parts of preamble to save power consumption. We simulate estimated AGC values, success probability of STE, estimated frequency offsets. In addition, it is found that when the bit error rate (BER) of the pre-FEC of 64QAM is 10-5, the required Eb/N0 is 19.5 dB under the conditions of additive white Gaussian noise (AWGN), a frequency offset, and echo channel. We measure the spectrum of DDC output, an estimated AGC value, and an estimated frequency offset, and experiment on FEC decoder. Measured results show the maximum transmitted error vector magnitude (EVM) of 1.54 % and the maximum received EVM of 2.67%.

In this paper, a new frequency offset estimation method in OFDM system is suggested. To measure fractional part of frequency offset, the repetition feature of cyclic prefix and that of training sequence is adopted. Both method shows relatively large frequency offset estimation error under low SNR circumstances, but this error can be greatly reduced by joint measurement of cyclic prefix and inversely repeated training symbol such as primary advanced preamble (PA-preamble) of IEEE 802.16m IMT-Advanced WiMax system. In this paper, the performance of suggested frequency offset estimation method is verified in IEEE 802.16m IMT Advanced WiMax system, using its PA-preamble and cyclic prefixes of A-preambles.

In this paper, we have identified the system instability factors in a bistatic radar system using pulse chasing and considered their effects on the bistatic receiver`s MTI(Moving Target Indication) improvement performance. The pulse chasing is a scan method that searchs a restricted area on the transmit pulse-to-pulse basis and the MTI filter is a signal processing that separates a target from some kinds of interferences such as clutter using small number of transmit pulses. Ideal MTI processing performance, e.g., clutter attenuation and improvement, has been limited by the property of the clutter itself, however, the MTI performance in a proposed bistatic receiver configuration could be affected by the receiving beam pointing error during pulse chasing scanning. Also, for the bistatic receiver, we have defined other system instability factors, which result from the time synchronization error, COHO`s phase error, the frequency/phase synchronization error, and have analyzed their effects on the system performance improvement.

In this paper, we have identified the system instability factors in a bistatic radar system using pulse chasing and considered their effects on the bistatic receiver`s MTI(Moving Target Indication) improvement performance. The pulse chasing is a method to efficiently scan a restricted search area within the limited transmitter power and time in a bistatic radar and to track a series of transmitted pulses using the receiver beam which has ideally matched to the pulse propagation rate. In this paper, we have discussed the interrelationship between the pulse chasing and time and frequency/phase synchronization and described the effects of the identified system instability factors on two kinds of MTI filter configuration, single delay-line and double delay-line, in the bistatic radar. And also, we have confirmed that the overall system improvement is restricted by a lower improvement factor among identified them, and discussed the allowable tolerance of the time and frequency/phase synchronization in the bistatic system.

MTI filter is used to separate target signal from clutter in many radar signal processing. By suppressing clutter before CFAR detection, the detection performance can be improved. As a radar system designed, a design engineer generally takes averaged SNR and CNR into account and does not include the effect of MTI filter`s frequency response. In practice, when the signals including clutter are pass through the filter, SNR is widely varying according to target velocity and CNR is also varying according to clutter center frequency and spectrum spreading. In this paper, we have derived the relationship between the MTI filter`s frequency response and a target`s velocity and a clutter`s spectrum characteristics. With the variation of SNR and CNR at the filter output, the detection performance of CFAR has been analyzed by the simulation and has made certain of their influences on the performance.

In this paper, we propose the SNR weighted LLR combining method in uplink mmWave multi-beams environment. Until now, the mmWave band has been considered as a candidate for new radio band for 5G mobile communication system. Because the mmWave band has good directivity, we can make sharp beam by applying beamforming technology using a plurality of antenna elements. The BS can have the antenna configuration for 3D beamforming and the UE can have the antenna configuration for circularly-switched beamforming for multi-beams communication. In the above situation, the uplink beam forms wider than the downlink beam and the transmitted signal energy of UE is distributed widely throughout the receive antennas of BS. Therefore, we propose the SNR weighted uplink LLR combining method for effective uplink performance in the above situation. Through the link-level simulation, we show the effect on the SNR weighted LLR combining of the uplink receiving beams and compare the coded BER performance of the suggested method with that of no weighted LLR combining method.

Monitoring abnormalities within reactor coolant pumps due to vibration, we introduce a Wigner distribution (WD) to a vibration monitoring system for analyzing vibration signals, and develop an on-line diagnostic method using the neural network employing back propagation algorithm. A rotor kit is used to simulate the abnormal conditions in the pump such as bearing rubbing, shaft bending, misalignment, etc. The data collected from the kit are analyzed using both a conventional system based on the Fourier transform (FT) and the software developed with the WD in this study, and they are compared. The study shows that spectrum represented by WD makes it easy to analyze the vibration signals of a rotating machine and the developed diagnostic method will help the operators grasp the cause of vibrations.

In this paper, several methods of carrier frequency offset (CFO) estimation for IEEE 802.16m WirelessMAN-Advanced are suggested and their performances are verified. Fractional part of CFO can be measured using time-domain repetition, and two types of repetition can be utilizable in IEEE 802.16m: the cyclic prefix and PA-preamble. Comparing the CFO measurement performance of the two methods by computer simulation, effective method of CFO measurement in IEEE 802.16m system is suggested.

In this paper, we analyzed the available frame synchronization error ranges through the uncoded BER (bit error rate) performance in the condition of 64-QAM digital modulation in Mobile-WiMAX system.

This paper finds the optimum input bit size of FFT engine in WiBro system through the uncoded-BER performances of computer simulation.

GPON Extender is required to extend transmission reach in GPON. In this paper, we propose simple activation techniques and a burst reset controller for the extender, and discuss experimental results of the Extender with CWDM links.

There are some leakage radiations from human body depending on incoming signals to it. As there are many noises in the frequency band spanning several MHz, human body communication (HBC), which is a technique to transfer various information through the human body as a communication channel, requires a limitation of frequencies and data rates to support a reliable network that can cope with interference from adjacent users and electrical devices. This paper proposes a frequency selective baseband transmission (FSBT) for HBC. FSBT requires no RF/IF components or overhearing in sleep mode as a service based on Touch-And-Play (TAP). The proposed HBC system supports high reliability, low power consumption, and low cost through FSBT. We achieved a biterror rate of 10–6 at 2 Mbps without forward error correction and verified the functions of the prototypes to transfer streaming data or image files between ultra-mobile PCs, or an ultra-mobile PC and printer.

Bolt degradation has become a major issue in the nuclear industry since the 1980's. If small cracks in stud bolts are not detected early enough, they grow rapidly and cause catastrophic disasters. Their detection, despite its importance, is known to be a very difficult problem due to the complicated structures of the stud bolts. This paper presents a method of detecting and sizing a small crack in the root between two adjacent crests in threads. The key idea is from the fact that the mode-converted Rayleigh wave travels slowly down the face of the crack and turns from the intersection of the crack and the root of thread to the transducer. Thus, when a crack exists, a small delayed pulse due to the Rayleigh wave is detected between large regularly spaced pulses from the thread. The delay time is the same as the propagation delay time of the slow Rayleigh wave and is proportional to the site of the crack. To efficiently detect the slow Rayleigh wave, three methods based on digital signal processing are proposed: wave shaping, dynamic predictive deconvolution, and dynamic predictive deconvolution combined with wave shaping.

OFDM systems are very sensitive to the phase noise. The phase noise in OFDM has two side effects: common phase error (CPE) and intercarrier interference (ICI). Especially, the rotation of constellation caused by CPE may be fatal in coherent schemes. This paper suggests an equalizer coupled with a phase tracking algorithm to combat frequency selectivity and to correct CPE. Computer simulations prove that CPE can be reduced by the phase tracking loop with low complexity.

This paper studies an automatic gain control (AGC) algorithm used in mobile cellular systems. The AGC design includes the determination of the precision of quantizer and a circuit to keep the input power of quantizer constant to minimize the quantization noise generated from the analog-to-digital conversion process. The proposed algorithm illustrates the method to determine the required precision of quantizer and to set the design parameters of the AGC in a mobile cellular system. The validity of the proposed algorithm is verified by computer simulation.

The general frame structure of current orthogonal frequency division multiplexing (OFDM) systems is based on the reservation-based time division multiple access (TDMA). The TDMA frame consists of a number of bursts, which are the transmission formats of the physical layer. Since the OFDM/TDMA uses broad bandwidth consisting of a large number of narrow bands, even the size assignment for the smallest burst is so large that a good throughput cannot be expected where a fine granularity is required. In this paper, we suggest an idea to obtain fine granularity effectively and to improve the system throughput greatly.

As the demand of down link high speed data packet service such as wireless Internet increases, the standardization for high speed downlink packet access (HSDPA) in wideband code division multiple access (WCDMA) system is in progress. HSDPA adopts adaptive modulation and coding (AMC) scheme, which changes the modulation level (for example, M-PSK, where M=4, 16, etc.) and channel coding rate adaptively to wireless channel conditions to maximize throughput. To adopt AMC, the receiver should measure the signal energy to interference power spectral density ratio (SIR) as the channel quality for feedback to the transmitter. The SIR estimation method, which has been used for the conventional voice services, was un-biased and had no problem in case of low power, low data rate, and low cell loading (i.e., single code transmission). However, the bias error of the conventional method increases as the transmitter has higher power, higher data rate, and more full loading (i.e., multi-code transmission), which are typical of the HSDPA service environment. To solve this problem, this paper proposes and verifies the validity of a SIR estimation method using the symbol patterns which are conventionally used to separate the pilot signals of transmit antennas. This paper also shows the method is always un-biased even with the HSDPA service environments.

This paper proposes an improved power control method, changing the target bit energy per noise spectral density (Eb/No) threshold with adaptive up and down step sizes in variable fading environments. We carry out computer simulations and hardware experiments for verification of the method. The new method results in better frame error rate (FER) and Eb/No performance than the existing ones.

This paper presents some channel estimation methods adequate for the space time transmit diversity (STTD) receiver that coherently demodulates signals from each path of two transmit antennas. The STTD mode receiver estimates the channel information of each antenna path from the received common pilot channel (CPICH) signals with known orthogonal patterns transmitted by two antennas at the base station. The conventional channel estimation methods using a pilot filter result in serious inter-antenna interference caused by imperfect orthogonal processing of signals between the two antennas. Another drawback is the inter-symbol interference caused by lack of orthogonality between two symbols Which is the basic premise of the STTD decoding algorithm. This paper analyzes the effects of the inter-symbol interference and proposes some robust channel estimation methods to reduce the effects of the inter-symbol interference; This paper also compares the performance of the proposed channel estimation methods in various fading channel environments through the effective signal to interference ratio (SIR) and the bit error rate (BER).

In an uplink cable modem, it is crucial to employ a preamble pattern suitable for frame acquisition, channel estimation and coarse timing/frequency acquisition. Proposed is an oversampled constant envelope zero autocorrelation code (CAZAC) for an uplink cable modem compliant with the data over cable service interface specification. The false alarm and missing probability of the proposed preamble pattern are investigated and compared to those of the existing preamble pattern based on the extended CAZAC sequence.