• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2013.10a
• /
• pp.402-404
• /
• 2013

The wireless communication channel different speed by depth of water or salt and it is influenced by multi-path according underwater. In the paper, MIMO(Multi-input-Multi-Output) system used turbo Equalizer combining Equalizer with Turbo codes for data rates by multi-path channel. we proposed and simulated that the Decision-Directed method used for phase offset. The simulation of proposed method show that the bit-error rate performance can be severely affected by phase errors.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.6C
• /
• pp.572-579
• /
• 2010

Filtered multi-tone (FMT) is a form of multicarrier modulation utilizing frequency-domain equalization efficient in multi-path fading channels. Doppler frequency information can be employed for channel estimation and link adaptation to improve the performance. However, most previous studies have concentrated on the orthogonal frequency division multiplexing (OFDM) instead of FMT. Moreover, they have not considered the synchronization error that can commonly occur in practical systems. In this paper, we propose Doppler frequency estimation scheme that is effective in FMT systems with residual synchronization error and high noise levels.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.12
• /
• pp.2055-2067
• /
• 1997

Values of process parameters in sheet metal forming can be estimated by various one-step inverse methods. One-step inverse methods based on deformation theory, however, cause some amount of error. The amount of error is generally increased as the deformation path becomes more complex. As a remedy, a new three dimensional multi-step inverse method is introduced for optimum design of blank shapes and strain distributions from desired final shapes. The approach extends a one-step inverse method to a multi-step inverse method in order to reduce the amount of error. The algorithm developed is applied to square cup drawing to confirm its validity by demonstrating reasonably accurate numerical results. Rapid calculation with this algorithm enables easy determination of an initial blank of sheet metal forming.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.6B
• /
• pp.601-609
• /
• 2002

In multi-path wireless channels with time-variant delay profile, a mobile station measures the received signal strength and report it to network which performs network control function such as handover. In order to improve the maximum ratio combining (MRC) gain, it also should search the strongest signal paths and measure their time offsets fast and exactly. This paper proposes some methods of fast and exactly measuring the multi-path signal strength and time offset. Since the W-CDMA system adopts antenna diversity technique for the next generation high speed packet access (HSDPA) service, we derive the optimum design parameter values for the proposed methods through computer simulations under the HSDPA conditions o( low speed of mobile, of no power control, and of multi-path wireless environment with transmit and receive antenna diversity. Finally, we prove the validity of the proposed methods by showing the improvement of the bit error rate (BER) performance.

• Journal of Korea Society of Industrial Information Systems
• /
• v.17 no.7
• /
• pp.9-16
• /
• 2012

In order to extend cell coverage and to cope with shadow areas, a relay-assisted wireless communications system has been widely studied. In this paper, we propose new equalization method for single carrier (SC) frequency domain equalizer (FDE) in amplify-and-forward (AF) relaying multi-path networks to improve the performance at shadow areas. The performance of SC-FDE system in 3-slot based multi-path networks can be improved considerably with the diversity gain which we obtain by equalizing the combined signal from relays by means of the minimum mean square error (MMSE) criteria. We find the weighting coefficients of maximum ratio combining (MRC) and the tap coefficients of MMSE equalizer for SC-FDE in AF relaying multi-path networks. Simulation results show that the proposed system considerably outperforms the conventional SC-FDE system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.6B
• /
• pp.689-696
• /
• 2011

In this paper, we propose the result of PSSK(Phase Silence Shift Keying) modulation scheme that is mixed PSK(Phase Shift Keying) modulation and PPM(Pulse Position Modulation) method. The performance of underwater communication systems are influenced underwater channel characteristics. In particular, delay spread can make ISI(Inter Symbol Interference) because of reverberation and multi path. It degrade the performance of the communication system. Also underwater sensor networks consider about power efficient due to the particularities of their operating environment. PSSK modulation method transmit two orthogonal symbol and using silence period in a period so it can reduce the power. Increasing the distance of between modulation symbols, to enhance the performance of BER(Bit Error Rate) as well as to improve power efficient. The result of sea trial, QPSK modulation BER is $3.19{\times}10^{-1}$ and PSSK modulation BER is $2.89{\times}10^{-1}$.

• Journal of Advanced Navigation Technology
• /
• v.18 no.3
• /
• pp.236-241
• /
• 2014

In a mobile ad hoc networks, multi-hop transmission is used to transfer data from source node to destination node and the routing protocol is the one of the important technical issues. The links between nodes can be unstable due to the changes of node location and channel conditions, and it can induce link error. To solve this problem, multipath routing was proposed. Multipath routing can reduce the data congestion and increase data throughput. In the multipath routing, however, each path can be interfered by the other path, and it can aggravate network performance. In this paper, we propose the multipath routing technique in the multi-rate MANET. The proposed multipath routing can avoid interference without the knowledge of node location. Simulation results show that the proposed multipath routing can reduce transmission delay and error.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.9
• /
• pp.1410-1415
• /
• 2001

Active control of sound radiation from a vibrating rectangular plate by a steady-state harmonic point force disturbance is experimentally studied. Structural excitation is achieved by two piezoceramic actuators mounted on the panel. Two accelerometers are implemented as error sensors. Estimated radiated sound signals using vibro-acoustic path transfer function are used as error signals. The vibro-acoustic path transfer function represents system between accelerometers and microphones. The approach is based on a multi-channel filtered-x LMS algorithm. The results shows that attenuation of sound levels of 11dB, 10dB is achieved.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.9
• /
• pp.785-798
• /
• 2004

This paper introduces the development of a range sensor based integrated navigation system for a multi-functional indoor service robot, called PSR (Public Service Robot System). The proposed navigation system includes hardware integration for sensors and actuators, the development of crucial navigation algorithms like mapping, localization, and path planning, and planning scheme such as error/fault handling. Major advantages of the proposed system are as follows: 1) A range sensor based generalized navigation system. 2) No need for the modification of environments. 3) Intelligent navigation-related components. 4) Framework supporting the selection of multiple behaviors and error/fault handling schemes. Experimental results are presented in order to show the feasibility of the proposed navigation system. The result of this research has been successfully applied to our three service robots in a variety of task domains including a delivery, a patrol, a guide, and a floor cleaning task.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.608-612
• /
• 2000

Active control of sound radiation(using active structural acoustic control) from a vibrating rectangular plate by a steady-state harmonic point force disturbance is experimentally studied. Control structural input are achieved by two piezoceramic actuators bonded to the surface of the panel. Two accelerometers are implemented as error sensors. Estimated radiated sound signals using vibro-acoustic path transfer function are used as error signals. The vibro-acoustic path transfer function represents system between accelerometers and microphones. The control approach are based on a multi-channel filtered-x LMS algorithm. The results demonstrate that attenuation of sound levels of 3dB, 13dB are achieved.