• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.4
• /
• pp.853-871
• /
• 2012

The location based service is divided into GPS that uses the artificial satellite or base transceiver station in order to cover the wide area and RTLS(Real Time Location System) using the Zigbee, RFID, CSS(Chirp Spread Spectrum), UWB, Bluetooth and Wi-Fi equipment in the space(close range) limited like the building inside or park. Moreover it also repeats the technical development upon through the acceleration of the development of the wire and wireless infrastructure and determination technology, the development of the Internet, diversification of the contents, and etc. As a result, it is expected to develop around the determination technology, witch is common core technology element, contents technology, Internet and mobile communication technology, and etc. afterward. In this research, the direction we investigate was to find and analyze new technology and standardization trend of LBS in order to contribute to the related industry.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.13 no.5
• /
• pp.400-410
• /
• 1988

In this paper, a fast synchronization system using SAW TDL matched filter and SAW recirculation loop not only for acquisition but also tracking in the direct sequence spread spectrum communication receiver in case of low SNR was designed and its characteristics were investigated. When signal of 16dB SNR was inputed at the receiver, the PN code of the receiver could be synchronized from the extracted signal for synchronization through SAW TDL matched filter and SAM recirculation loop for 30 recirculations. And the average synchronization time of this system was calculated. From the results, we found that this synchronization system could achieve faster synchronization of PN codes in the receiver under the circumstances of low SNR than that of using only matched filter.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.5
• /
• pp.580-586
• /
• 2019

In this paper, we propose a biomimetic communication method using a dolphin whistle to covertly transmit the communication signal. A conventional CSS (Chirp Spread Spectrum) modulation technique divides dolphin whistle into several slots and modulates with up and down chirp signals. That causes the time-frequency characteristic difference between the original dolphin whistle and the camouflage performance is degraded. In this paper, we propose a delay based modulation scheme to eliminate distortions. The simulation results show that the bit error rate of the proposed method is better performance than that of the conventional CSS modulation method by about 3.5 dB to 8 dB. And the camouflage performance that evaluated through the cross correlation in the time-frequency domain is also better than that of the CSS modulation method.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 2006.07a
• /
• pp.344-344
• /
• 2006

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.8
• /
• pp.1-11
• /
• 2012

The multi-code spread spectrum communication system, which spreads data bit stream by multiplexing orthogonal codes, can transmit data in high rate. However it needs the high-cost good linear amplifier because of the multi-level output signal. In order to overcome this drawback several systems making the amplitude of output signal constant with Walsh codes have been proposed. Recently constant amplitude pre-coded multi-code spread spectrum systems using extended m-sequence have been proposed. In this paper we consider an extended m-sequence based constant amplitude multi-code spread spectrum system with code set partitioning. By grouping the orthogonal codes into 4 subsets, not only is the computational complexity of the transceiver reduced but BER performance also improves. It has been shown that parity checking on four detected codes at the receiver can correct code detection error and result in BER performance enhancement. In this paper we propose a improved parity check receiver. We carried out computer simulation to verify feasibility of the proposed algorithm.

• The Journal of the Acoustical Society of Korea
• /
• v.35 no.5
• /
• pp.368-374
• /
• 2016

This paper presents constructing transmitter and receiver by using a direct sequence spread spectrum techniques to DPSK (Differential Phase-Shift Keying) scheme in underwater acoustic communication. Since DPSK signal can be demodulated if the receiver knows only the phase difference between the adjacent bits, DPSK receiver structure has the advantage of being simplified. In the conventional receiver, two adjacent symbols of transmitted signal before despread are passed to the transition correlator that detects data by comparing maximum correlation outputs. At this time, the error for maximum value of the correlator output may increase because of low SNR (Signal to Noise Ratio) or high Doppler shift frequency according to the underwater channel. In this paper, we propose a method for accurate detection result using the width as well as the magnitude among outputs produced by the correlator. The performances of the proposed method was evaluated by simulation and lake trial data.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.10 no.4
• /
• pp.145-150
• /
• 2010

In this paper, we propose additional data transmission system for spectrum efficiency improvement and derive channel capacity formula as a approximated closed-form. Spread spectrum watermarking scheme is selected for the watermarking embedder. Nakagami-q (Hoyt) model is considered as a multipath fading channel. Numerical results show the channel capacity variation of the proposed system in wireless fading channel. From the results, we confirm that the channel capacity of the watermarking system is affected by the fading coefficient and system parameters such that host sampling frequency, host-to-watermark ratio, watermark-to-noise ratio, and PN sequence length.

• Journal of the Korean Institute of Telematics and Electronics C
• /
• v.34C no.8
• /
• pp.1-7
• /
• 1997

In tis paper, w eproposed a modeling for direct-sequence spread communication base band modem in RT-level VHDL and implemented in a one-chip VLSI and tested. The transmitter modulates with DQPSK modulation method and spreads a modulated signal with 32-bit PN code into 1.152MHz. The receiver de-spreads a signal using 32-tap matched filter and recovers with DQPSK demodulation method. The digital frequency synthesizer generates the sine signal and the cosine signal of 2.304MHz with ROM tables in the size of 7$\^$*/256 and 6$\^$*/256, respectively. The implemented VLSI has been verified a BER with 10$\^$-4/ at E$\_$b//N$\_$o/ of 13dB with a SPW fixed design model and fabricated in the 0.8.mu.m KG6423 gate array with a VHDL model.

• Proceedings of the KIEE Conference
• /
• 2005.05a
• /
• pp.78-80
• /
• 2005

The pattern recognition of automobile and parking line for the automatic car parking system was processed based on statistical method for reducing the processing time. The command of driving for parking at the vacant parking lot was transmitted from processor to motor driven actuator using direct sequence spread spectrum communication, which enables the multiple transmission in CAN(controller area network). The test-bed which has CCD camera, processor, radio transceiver and FPGA was implemented and demonstrated to be operated well.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.49 no.4
• /
• pp.45-54
• /
• 2012

Location-based services with GPS positioning technology as a key technology, but recognizing the current location through satellite communication is not possible in an indoor location-aware technology, low-power short-range communication is primarily made of the study. Especially, as Chirp Spread Spectrum(CSS) based location-aware approach for low-power physical layer IEEE802.15.4a is selected as a standard, Ranging distance estimation techniques and data transfer speed enhancements have been more developed. It is known that the distance measured by CSS ranging has quite a lot of noise as well as its bias. However, the noise problem can be adjusted by modeling the non-zero mean noise value by a scaling factor which corresponds to the change of magnitude of a measured distance vector. In this paper, we propose a localization system using the CSS signal to measure distance for a mobile node taken a measurement of the exact coordinates. By applying the extended kalman filter and least mean squares method, the localization system is faster, more stable. Finally, we evaluate the reliability and accuracy of the proposed algorithm's performance by the experiment for the realization of localization system.