• The Journal of the Acoustical Society of Korea
• /
• v.34 no.3
• /
• pp.210-218
• /
• 2015

When the driving voltage of an ultrasound transducer is increased to improve the quality of ultrasound images, heat is generated inside the transducer that can cause patient's skin burn and degradation of transducer performance. Hence, in this paper, a method to disperse the heat of the transducer has been studied. The phased array transducer having 3 MHz center frequency and 32 channels was selected for analyses of the thermal dispersion. First, mechanism of the heat generation was investigated in relation to the transducer operation through theoretical analysis, and material damping and sound pressure amplitude were confirmed to be influential on the heat generation. Further, we investigated the effects of the properties of the materials constituting the transducer on the thermal dispersion through finite element analysis. Based on the analysis results, we determined the thermal properties of the constituent materials that could facilitate the thermal dispersion inside the transducer. The determined thermal properties were applied to the finite element model, and the results showed that the maximum temperature at an acoustic lens contacting with a patient was decreased to 51 % of its initial value.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.3
• /
• pp.514-522
• /
• 2015

In Microwave Radio Link, it is necessary to consider the radio fading to consistently assure the radio link of the high quality as the distance. If the fixed modulation is used for the microwave radio link, it is difficult to keep the high availability of link for the case of the long distance. Adaptive Modulation(AM) provide good quality on microwave link, but the application of the only-AM is not enough to provide the availability assurance due to the fluctuating characteristics of link capacity. Our previous study has proposed the improvement method of transmission in association with the distance, however the previous method needed to make up for the common application. There was no suggestion of a mathematical formula with a variable. In this paper, we propose an optimized Adaptive Transmission Techniques with calculating formula of the priority traffic transmission capacity based on AM in consideration of the fade margin for the availability assurance as the distance and the comparison of the channel bandwidth for Long-distance Radio Link.

• Journal of Satellite, Information and Communications
• /
• v.11 no.4
• /
• pp.102-106
• /
• 2016

With the popularity of smart phones and the help of high-speed wireless communication technology, high-quality multimedia contents have become common in mobile devices. Especially, the release of Oculus Rift opens a new era of virtual reality technology in consumer market. At the same time, 3D audio technology which is currently used to make computer games more realistic will soon be applied to the next generation of mobile phone and expected to offer a more expansive experience than its visual counterpart. This paper surveys concepts, algorithms, and systems for modeling 3D sound virtual environment applications. To do this, we first introduce an important design principle for audio rendering based on physics-based geometric algorithms and multichannel technologies, and introduce an audio rendering pipeline to a scene graph-based virtual reality system and a hardware architecture to model sound propagation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.11
• /
• pp.2412-2418
• /
• 2009

As an astonishing progress of FTTH infrastructure, the new technologies have been widely studied to use the tantalizing benefits of high bandwidth in fiber optic cable. In this paper, a new VONU is presented to perform all necessary optical functions. It can converts digital and analog CATV signals and satellite-based signal transmitted via one fiber optic cable to electrical signals (electric lights). However, most previous VONU systems have the problems such as interference between difference services, signal distortion, and noise increasing rate. These problems cause the quality deterioration in broadcasting. Therefore, we suggest the new VONU system to solve all problems listed above. In addition, we show that how our system performs well by measuring the real data with implemented system.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.12
• /
• pp.2219-2225
• /
• 2016

Mobile communication systems should be able to support multimedia traffics with limited transmit power due to the frequency reuse for maximizing the channel accommodation. Real-time data is very sensitive to delay, and they need to be transmitted instantly. On the other hand, non-real time data is less sensitive to delay, and their packet loss can be handled more flexibly. Therefore an adaptive resource management scheme is essentially required which enables to keep the minimal power allocated in the base station while guaranteeing the user requirements for QoE within a permissible range. Power-saving techniques are required in order to support multimedia services in the mobile networks because the power consumption increases greatly with the transmission rate increase. This paper proposes a novel scheme which enables to keep the allocated power minimal while guaranteeing the user requirements for QoE within a permissible range.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2015.05a
• /
• pp.681-684
• /
• 2015

Power amplifier is an essential component for transmitting signals to a remote receiver in wireless communication systems. Power amplifier is a non-linear device in general, and the nonlinear distortion becomes severer as the output power increases. The nonlinearity results in spectral regrowth, which leads to adjacent channel interference, and decreases the transmit signal quality. To linearize power amplifiers, many techniques have been developed so far. Among the techniques, digital pre-distortion is known as the most cost and performance effective technique. However, the linearization performance falls down abruptly when the power amplifier operates in its saturation region. This is because of the severe nonlinearity. To relieve this problem, this paper proposes a new adaptive predistortion technique. The proposed technique controls the adaptive algorithm based on the power amplifier input level. Specifically, for small signals, the adaptive predistortion algorithm works normally. On the contrary, for large signals, the adaptive algorithm stops until small signals occur again. By doing this, wrong coefficient update by severe nonlinearity can be avoided. Computer simulation results show that the proposed method can improve the linearization performance compared with the conventional digital predistortion algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.8
• /
• pp.651-659
• /
• 2014

In this paper, we consider a two way relay network for ship-to-ship communications in a fleet, where two communicating ships exchange the information with the help of a multi-antenna relay ship. For the network, we propose a rate-aware three-phase analog network coding to improve the reliability of the information exchange with asymmetric rates. The proposed scheme allows low-complex implementation of the relay without channel estimation by generating an improved analog network coded signal with the orthogonally received signals from two ships by using only the received signal power at each antenna. In addition, the proposed scheme reduces outages in the data exchange at asymmetric rates by adopting a rate-aware relay power allocation, which is confirmed by evaluating the outage performance via simulation.

• Journal of the Korea Convergence Society
• /
• v.9 no.9
• /
• pp.47-52
• /
• 2018

Wi-Fi enabled Internet of Things (IoTs) had a substantial impact on society, economy and industry. However wireless connectivity technologies in unlicensed band such as Wi-Fi are vulnerable to interferences. They also face difficulty providing wireless connectivity over long range in dense networks due to the dynamically changed interference effect and asymmetric interference conditions. In this paper, robust acknowledgement transmission scheme is proposed for long range IoTs. According to the proposed scheme, it is possible to control the transmission rate of the transmission success rate of the response frame by adjusting the transmission rate of the response frame when the interference is present asymmetrically. It is also possible to use higher data rate when high quality link is guaranteed. The evaluation results demonstrated the proposed scheme improves the aggregate throughput by at most 9 Mbps when 20 MHz bandwidth transmission mode was adopted.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.9
• /
• pp.106-113
• /
• 2015

This paper integrates human visual system (HVS) characteristics into compressed sensing recovery of color images. The proposed visual weighting of each color channel in group-sparsity minimization not only pursues sparsity level of image but also reflects HVS characteristics well. Additionally, an edge-preserving filter is embedded in the scheme to remove noise while preserving edges of image so that quality of reconstructed image is further enhanced. Experimental results show that the average PSNR of the proposed method is 0.56 ~ 4dB higher than that of the state-of-the art group-sparsity minimization method. These results prove the excellence of the proposed method in both terms of objective and subjective qualities.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.10
• /
• pp.53-59
• /
• 2011

In recent years, mobile communication service is used extensively as a larger service area for the maintenance of quality of service required by the expansion of service areas and As the ever-increasing role in relays, and the location is relatively easy to install and less constrained costs, operating cost savings in terms of ICS(Interference Cancellation System) repeaters are required. However, an adaptive algorithm that is applied when updating the filter due to the increase in volume of operations increase the complexity of hardware implementation is fraught with many difficulties. In this paper, if there is a path that feedback. ICS repeater utilizing baseband signal processing for the removal of interfering signals from the feedback operation, significantly reducing the amount of reducing hardware complexity Complex Singed Signed LMS adaption algorithm is proposed. Proposed algorithm for evaluating the performance of Static channel WCDMA signal environment for the ICS, the results of the simulation algorithm, convergence speed and better performance in therms of convergence errors that are required through the implementation of the operation greatly reduces the amount of hardware complexity able to reduce the effect was visible.