• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.7 no.1
• /
• pp.71-82
• /
• 1996

In this paper, the Doppler phase error due to the relative velocity between a satellite and the earth station in communications using a low earth orbit mobile satellite is detected. The performance of BPSK system in the presence of Rician fading with Doppler phase error and interference, noise is compared with that of the system disturbed by Doppler phase error and noise only. The expression of error rate performance of BPSK system is derived as the type of complementary error function. The numerical calculation of the induced equation are performed in terms of satellite-height, orbit-eccentricity, the velocity of the earth, Rician fading parameter, signal to interference rateio (SIR), the ratio of carrier frequency and base band bit rate. The main conclusion that can be drawn from this analysis is that Rician fading channel environment with Doppler phase error and interference effect yields severe performance degradation than Do- ppler phase error and noise effect in satellite communication channel. And using the numerical calculation, we give a quantitative insight how much the satellite communication channel parameters degrade the system performance. Furthermore it is shown that an appropriate transmission power control for the performance enhancement is beneficial to the new satellite communication system planning.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.36S no.8
• /
• pp.8-16
• /
• 1999

In this paper, the performance of a hybrid DS/SFH-SS(direct-sequence/slow-frequency-hopped spread-spectrum) system with coherent BPSK modulation over Nakagami fading channel in the presence of multiple tone jamming is analyzed. Because the Nakagami m-distribution can describe not only Rayleigh fading but also more general fluctuations involving a specular component by adjusting the value of the fading index m. It is known that for m=1 corresponds to Rayleigh fading, for $1/2{\le}m{\le}1$ corresponds to the worst case fading condition, for m>1 corresponds to Rician fading, and for $m{\to}{\infty}$ corresponds to the nonfading condition. The bit error probability is derived over Nakagami model and numerical evaluations are presented for some combinations of system parameters. The results show that as m increases, the bit error probability is better. Also, at a low JSR(jamming-to-signal power ratio), a pure DS-SS system can achieve lower bit error probability than a hybrid DS/SFH-SS system. But at a high JSR, a hybrid DS/SFH-SS system is shown to be superior to a pure DS-SS system. Therefore, it is demonstrated that without increasing the total system bandwidth, the performance of a hybrid DS/SFH-SS is superior to that of a pure DS-SS system in the presence of multiple tone jamming.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.47 no.1
• /
• pp.60-68
• /
• 2010

In case of sensorineural hearing loss, auditory perception can be activated by electrical stimulation of the nervous system via electrode implanted into the cochlea or auditory nerve. Since the tonotopic map of the human auditory nerve has not been definitively identified, the recording of auditory nerve signal with microelectrode is desirable for determining the tonotopic map. This paper proposes the multi-channel analog front-end for auditory nerve signal detection. A channel of the proposed analog front-end consists of an AC coupling circuit, a low-power 4th-order Gm-C LPF, and a single-slope ADC. The AC coupling circuit transfers only AC signal while it blocks DC signal level. Considering the bandwidth of the auditory signal, the Gm-C LPF is designed with OTAs adopting floating-gate technique. For the channel-parallel ADC structure, the single-slope ADC is used because it occupies the small silicon area. Experimental results shows that the AC coupling circuit and LPF have the bandwidth of 100 Hz - 6.95 kHz and the ADC has the effective resolution of 7.7 bits. The power consumption per a channel is $12\;{\mu}W$, the power supply is 3.0 V, and the core area is $2.6\;mm\;{\times}\;3.7\;mm$. The proposed analog front-end was fabricated in a 1-poly 4-metal $0.35-{\mu}m$ CMOS process.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.9
• /
• pp.809-819
• /
• 2004

In this paper, in order to exclude the expansion of M/W relay frequency or its new frequency assignment possibly, we analyzed a possibility of substituting M/W system by B-WLL or optical fiber network regarding service quality and economical points. To define the target of service quality, pre-condition and analysis method for the selected media have been derived to compare each other. E1 transmission with BER 10$^{-1}$ was chosen as a reference capacity, and service distance was calculated f3r the selected media as a function of availability. Also from the economical point we considered 3 systems such as optical fiber, M/W, and B-WLL based upon basic system structure, and analyzed them for various line configurations of fiber optic and B-WLL according to service period, system capacity, transmission distance, and data rate. It was confirmed that B-WLL can provide quality of service with 99.999 % availability within 1.6 km cell radius, and for optical fiber substitution, the leased fiber conduit on an electric pole is more economical than M/W system irrespective of service period, but in case of directly digging for underground conduit, it turned out ineffective regardless of cabling duct types.

• Journal of Korea Multimedia Society
• /
• v.13 no.5
• /
• pp.710-721
• /
• 2010

Recently, for the advancement of embedded technology about mobile device, a new kind of service, mash-up is appeared. It is service or application combining multimedia content making tool or device and web-GIS(geographic information system) service in the mobile environment. This service can be ease to use for casual user and can apply in various ways. So, It is served in web 2.0 environment actively. But, in the mashup service, because generated multimedia contents linked with web map are new type of multimedia contents which include user's migration routes in the space such as GPS coordinates. Thus, there are no protection ways for intellectual property created by GIS web-map service users and user's privacy. In this paper, we proposed a location and user information hiding scheme for GIS web-map service. This scheme embeds location and user information into a picture that is taken by camera module on the mobile phone. It is not only protecting way for user's privacy but is also tracing way against illegal photographer who is peeping person through hidden camera. And than, we also realized proposed scheme on the mobile smart phone. For minimizing margin of error about location coordinate value against contents manipulating attacks, GPS information is embedded into chrominance signal of contents considering weight of each digit about binary type of GPS coordinate value. And for tracing illegal photographer, user information such as serial number of mobile phone, phone number and photographing date is embedded into frequency spectrum of contents luminance signal. In the experimental results, we confirmed that the error of extracted information against various image processing attacks is within reliable tolerance. And after file format translation attack, we extracted embedded information from the attacked contents without no damage. Using similarity between extracted one and original templete, we also extracted whole information from damaged chrominance signal of contents by various image processing attacks.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.4
• /
• pp.876-884
• /
• 2014

A hardware design of LDPC decoder which is based on the improved normalized min-sum(INMS) decoding algorithm is described in this paper. The designed LDPC decoder supports 19 block lengths(576~2304) and 6 code rates(1/2, 2/3A, 2/3B, 3/4A, 3/4B, 5/6) of IEEE 802.16e mobile WiMAX standard and 3 block lengths(648, 1296, 1944) and 4 code rates(1/2, 2/3, 3/4, 5/6) of IEEE 802.11n WLAN standard. The decoding function unit(DFU) which is a main arithmetic block is implemented using sign-magnitude(SM) arithmetic and INMS decoding algorithm to optimize hardware complexity and decoding performance. The LDPC decoder synthesized using a 0.18-${\mu}m$ CMOS cell library with 100 MHz clock has 284,409 gates and RAM of 62,976 bits, and it is verified by FPGA implementation. The estimated performance depending on code rate and block length is about 82~218 Mbps at 100 MHz@1.8V.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.35 no.2
• /
• pp.129-135
• /
• 1999

The telemetry system for the current speed and direction, the underwater ambient noise and the distribution ecology of fishes was constructed by the author and his collaborator in order to product and manage effectively in shallow sea culture and setnets fisheries, and then the experiments for the telemetry system carried out at set net fishing ground located Nungpobay in Kojedo from October 1996 to June 1997. As this results, the techniques suggested in the telemetry system gave full display its function even though far away 1.5 km from transmitting part, but with the suggested telemetry system could not be ascertained relationship between physical environment and distribution ecology of fishes.

• Journal of Internet Computing and Services
• /
• v.18 no.5
• /
• pp.17-22
• /
• 2017

In a MPC coding using excitation source of voiced and unvoiced, it would be a distortion of speech waveform. This is caused by normalization of synthesis speech waveform of voiced in the process of restoration the multi-pulses of representation section. This paper present PCFBD-MPC( Position Compensation Frequency Band Division-Multi Pulse Coding ) used V/UV/S( Voiced / Unvoiced / Silence ) switching, position compensation in a multi-pulses each pitch interval and Unvoiced approximate-synthesis by using specific frequency in order to reduce distortion of synthesis waveform. Also, I was implemented that the PCFBD-MPC( Position Compensation Frequency Band Division-Multi Pulse Coding ) system and evaluate the SNRseg of PCFBD-MPC in coding condition of 8kbps. As a result, SNRseg of PCFBD-MPC was 13.4dB for female voice and 13.8dB for male voice respectively. In the future, I will study the evaluation of the sound quality of 8kbps speech coding method that simultaneously compensation the amplitude and position of multi-pulse source. These methods are expected to be applied to a method of speech coding using sound source in a low bit rate such as a cellular phone or a smart phone.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.8
• /
• pp.1-10
• /
• 2000

Performance analyses of hybrid DS-SFH spread-spectrum systems using coherent MSK and QPSK modulation techniques are considered over Rayleigh fading channel in the presence of multi-tone jamming. The BER equations for MSK and QPSK systems with non-diversity reception in the receiver are derived as the concept of average signal-to-noise power ratio E$\_$b//N$\_$0/ and jamming-to-signal power ratio JSR, and the performances is evaluated for various system parameters. The evaluation of performance is done between fading and nonfading system, and between MSK and QPSK system. Results show that the performances of two systems are similar in low JSR. However, MSK system outperforms QPSK system as JSR increases. Overall performances of two systems are a little improved as the DS spreading gain increases for the total spread-spectrum bandwidth fixed. The performance difference between fading system and nonfading system is similar in low E$\_$b//N$\_$0/, however, it becomes very largewith increase of E$\_$b//N$\_$0/..

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.42 no.5 s.305
• /
• pp.173-180
• /
• 2005

In this paper, we proposed the image hiding method which decreases calculation amount by encrypt partial data using discrete wavelet transform(DWT) and linear scale quantization which were adopted as the main technique for frequency transform in JPEG2000 standard. Also we used the chaotic system and cat map which has smaller calculation amount than other encryption algorithms and then dramatically decreased calculation amount. This method operates encryption process between quantization and entropy coding for preserving compression ratio of images and uses the subband selection method. Also, suggested encryption method to JPEG2000 progressive transmission. The experiments have been performed with the Proposed methods implemented in software for about 500 images. Consequently, we are sure that the proposed is efficient image encryption methods to acquire the high encryption effect with small amount of encryption. It has been shown that there exits a relation of trade-off between the execution time and the effect of the encryption. It means that the proposed methods can be selectively used according to the application areas.