Seung-Yong Chun

Acoustic intruder detection system for home security

We propose a new algorithm to detect an intruder in a small room. The basic idea of the proposed method is to estimate the variation of features of the room acoustic transfer function.

A Study on the Cooperative Diversity Technique with Amplify and Forward for Underwater Wireless Communication

In this paper, we introduce the application of the cooperative diversity in underwater wireless communication. Cooperative diversity creates a virtual sensor array between source and destination, thereby influence the space diversity benefits of multiple-input/multiple-output (MIMO) system. In this paper, we consider the amplify-and-forward (AF) protocols in cooperative diversity for underwater wireless communication. For AF protocol in cooperative diversity, each relay node is amplifying the received signal from the source node and retransmits to destination node. We used the Ray mode model base on underwater channel parameter between each node for assume the underwater channel. Simulation results of the AF cooperative diversity in underwater wireless communication show the better performance than the direct transmission. As a result, we acquired more enhanced result of about 5 dB than other comparison technique.

Passive-range estimation using dual focused beamformers

The passive-range estimation technique using a single focused beamformer has been studied under the sea. However, there are not many more methods in the case of closed multisource environments. In this paper, we propose the technique using dual focused beamformers to estimate the ranges of a closed multisource, and compare the proposed technique with the previous method. The proposed method is verified via computer simulation under the simplified multipath underwater channel model.

Design of OFDM System for High Speed Underwater Communication

The performance of underwater acoustic communication system is influenced on channel characteristic. Especially, an important feature of the underwater acoustic communication is multipath propagation and Doppler spread cause by the surface and bottom reflections. In this paper, we study the application of high speed data transmission in underwater to use the OFDM (Orthogonal Frequency Division Multiplexing) technique for robust the reverberation and multi-path. We use the clipping method for overcome the performance reduce in high PAPR (Peak-to-Average Power Ratio). We confirm the performance of communication in underwater to use the model for actually underwater channel simulation model and experiment in small water tank. As a result of experiment in small water tank, we acquired the BER of modulation techniques.

Sea Trial Results of the Direct Sequence Spread Spectrum Underwater Acoustic Communication in the East Sea

Spread spectrum provides the minimized inter-symbol interference, the low probability of intercept and the multiple access capability. This paper presents a direct sequence spread spectrum with carrier/timing recovery and equalizer which compensates the delay spread caused by multipath transmission. When the sea trials were performed in Korean East Sea, the bit error rates of QPSK and direct sequence spread spectrum are and at 3 km source-receiver range, respectively.

A Study on the Low Power Communication for Underwater Sensor Network

In this paper, we study the possibility and the performance of PSSK(Phase Shift Silence Keying) and PSPM(Phase Shift Pulse-position Modulation) technique for low power communication. Every Mary PSK(Phase Shift Keying) symbol of PSSK that was proposed for low power communication in WBAN(Wireless Body Area Network) has the silence period for a half period of symbol. Similarly, PSPM is a kind of PSK modulation combined with PPM(Pulse Position Modulation). The bandwidth efficiency of PSPM is lower than conventional PSK and PSSK, but the power efficiency increases. Also, there is the advantage of hamming distance gain. It can get from lower modulation level of PSPM modulation technique. At the last of this paper, we will compare the BER performance of QPSK, PSSK and PSPM data acquired from the sea trials.

Doppler estimation based on frequency average and remodulation for underwater acoustic communication

Underwater acoustic communication channel is time varying and has Doppler effect due to wind, sea surface roughness, and platform motion. We have to recognize the changing channel state and apply it to communication technique for increasing transmission efficiency in the underwater acoustic channel. In this paper, we propose more reliable Doppler estimation method based on frequency average and remodulation. We conducted the simulation and sea trial to evaluate the performance of the proposed method. When the channel coding technique was not applied, the uncoded bit error rate performance of the proposed method was improved about maximum 50.3% compared with conventional method.

Underwater Acoustic Communication of FH-MFSK Method with Multiple Orthogonal Properties

The present invention relates to a method for designing a signal having multiple orthogonal properties to prevent the degradation of communication performance due to inter-symbol interference caused by multi-path transmission in an underwater acoustic communication system and, more particularly, to a communication method for reducing an error rate by using an orthogonal signal for each symbol. That is, provided is a frequency-hopped multiple frequency shift keying (FH-MFSK) underwater acoustic communication method having multiple orthogonal properties. In general, an FSK method is simple in processing but vulnerable to the inter-symbol interference caused by the multi-path transmission. The method of the present invention generates orthogonal codes of the same number as the symbols to be transmitted. The codes correspond to multiple frequencies. An m-sequence is used to generate the multiple orthogonal codes. The performance of the method of the present invention is compared with the performance of an existing MFSK method through an experiment. The comparison result shows that the error rate at 100 bps in the method of the present invention is lower than that in the existing method by 6 to 10%.

Decision feedback equalization for low power underwater communication system

In this paper, a decision feedback equalizer(DFE) is applied to the PSSK(Phase Shift Silence Keying) and PSPM (Phase Shift Pulse-position Modulation) for low-power communication in underwater sensor network. All of the M-ary PSK(Phase Shift Keying) symbol of PSSK that was proposed for low power communication in WBAN(Wireless Body Area Network) has the silence duration for a half period of symbol. Similarly, PSPM is also a kind of PSK modulation which is combined with PPM(Pulse Position Modulation). The bandwidth efficiency of PSPM is lower than conventional PSK and PSSK, but the power efficiency better than those methods. However, the problem of PSSK/PSPM is so erratic to find PSK signal duration because of the delay spreads. If the decision for the signal position is wrong, then the error probability of PSSK/PSPM is significantly increased. For this reason, we applied to these modulations the DFE and compared the BER performances about QPSK, PSSK and PSPM data which is acquired from the sea trials.

Underwater Source Localization Using the Interference Pattern Matching in Range Dependent Environments

This paper proposes a method of underwater source localization using the wideband interference patterns matching in shallow water environments that vary in range. By matching two interference patterns in the spectrogram, it is estimated a ratio of the range from source to sensors, and then this ratio is applied to the Apollonius circle. The Apollonius circle is defined as the locus of all points whose distances from two fixed points are in a constant value so that it is possible to represent the locus of potential source location. The Apollonius circle alone, however, still keeps the ambiguity against the correct source location. Therefore another equation is necessary to estimate the unique locus of the source location. By estimating time differences of signal arrivals between source and sensors, the hyperbola equation is used to get the cross point of the two equations, where the point being assumed to be the source position. Simulations are performed to get performances of the proposed algorithm. The results show that the proposed algorithm successfully estimates the source position within an error bound of 10%.