• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.10-18
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• 2013

With advancing of mobile communication services and commercializing of VoLTE (Voice of LTE), it is getting to pay attention on QoS of VoLTE. This paper proposes an integrated E-model in which some factors influenced to service quality of VoIP and VoLTE based voice communication system are considered in calculating the voice quality of Wideband Codec. The model aims to calculate R value which reflects the situations of access network, network characteristics, terminals' usage and mobility. We mainly deal with the integrated E-model's structure, related algorithms and optimal parameters for VoLTE. Some experiments show that the voice quality difference between VoIP and VoiceChecker, and VoLTE and POLQA, is below 10%. With the proposed model, we can calculate the voice quality by making use of the factors directly affected to service quality and the environment of VoLTE terminal and network. As a result, we can estimate the service quality in advance, without measuring it in real wireless environment.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.2
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• pp.84-93
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• 2011

In order to provide the real time and proper information to the pedestrian who is using the transport connection and transfer center through data collecting and processing process, the design of the test-bed (Gimpo airport)'s communication construction and the technology of the pedestrian location tracking has been researched. The design of the communication construction should make sure that it can provide believable data to the user of the transfer center. At the same time, the location tracking should also be considered, so that the require of the communication efficiency and the location tracking efficiency can be met together. In order to make the efficient location tracking technology, the problems related to the commercial technology based real time location identification will be resolved and the new approach method was proposed and be applied and analysed to the test-bed. The wireless access points can be located in the most real-world situation which has added the characteristics of the real building to the electronic map, and through the analysis of theirs location, they can be set as the mainly necessary points for the communication construction design and the location tracking and the method to locate that points has been proposed. How to set, how to apply it to the test-bed and the examination result will be introduced in this paper.

• Progress in Medical Physics
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• v.19 no.1
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• pp.42-48
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• 2008

Bio-implantable devices such as heart pacers, gastric pacers and drug-delivery systems require power for carrying out their intended functions. These devices are usually powered through a battery implanted with the system or are wired to an external power source. This paper describes an inductive power transmission link, which was developed for an implantable stimulator for direct stimulation of denervated muscles. The carrier frequency is around 1MHz, the transmitter coil has a diameter of 46mm, and the implant coil is 46mm. Data transmission to the implant with amplitude shift keying (ASK) and back to the transmitter with passive telemetry can be added without major design changes. We chose the range of coil spacing (2 to 30mm) to care for lateral misalignment, as it occurs in practical use. If the transmitter coil has a well defined and reliable position in respect to the implant, a smaller working range might be sufficient. Under these conditions the link can be operated in fixed frequency mode, and reaches even higher efficiencies of up to 37%. The link transmits a current of 50 mA over a distance range of 2-15 mm with an efficiency of more than 20% in tracking frequency. The efficiency of the link was optimized with different approaches. A class E transmitter was used to minimize losses of the power stage. The geometry and material of the transmitter coil was optimized for maximum coupling. Phase lock techniques were used to achieve frequency tracking, keeping the transmitter optimally tuned at different coupling conditions caused by coil distance variations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.1-9
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• 2004

User-Perceived application-level performance is a key to the adoption and success of CDMA 2000. To predict this performance in advance, a detailed end-to-end simulation model of a CDMA network was built to include application traffic characteristics, network architecture, network element details, and protocol features. We assess the user application performance when a Radio Access Network (RAN) and a Core Network (CN) adopt different transport architectures such as ATM and If. For voice Performance, we found that the vocoder bypass scenario shows 8% performance improvement over the others. For data packet performance, we found that HTTP v.1.1 shows better performance than that of HTTP v.1.0 due to the pipelining and TCP persistent connection. We also found that If transport technology is better solution for higher FER environment since the IP packet overhead is smaller than that of ATM for web browsing data traffic, while it shows opposite effect to small size voice packet in RAN architecture. Though simulation results we showed that the 3G-lX EV system gives much better packet delay performance than 3G-lX RTT, the main conclusion is that end-to-end application-level performance is affected by various elements and layers of the network and thus it must be considered in all phases of the technology evolution process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.352-360
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• 2008

Recently Task Group (TG) 4 of the Institute of Electrical and Electronics Engineers (IEEE) 802.15a has been recommended a system with ranging capability in existence of multiple Simultaneous operating piconets (SOPs) as well as low-cost, low-power. According to the ranging service, coherent and non-coherent based ranging schemes using ternary code have been adopted as a standard. However it is hard to estimate an accurate time of arrival (TOA) in case of using direct sequence based TOA estimation method because pulse repetition interval (PRI) offered by TG is more limited than the maximum excess delay (MED) of channel. To mitigate inter pulse interference (IPI) problem, this paper proposes a non-coherent TOA estimation scheme using non-periodic transmission (NPT) pattern. The proposed receiver is based on a non-coherent energy detection considering with motivation of low rate wireless personal area network (LR-WPAN). TOA information is estimated via proper comparison with a prescribed threshold after the sliding correlation and search back window (SBW) process for reducing TOA error. To verify the performance of proposed ranging scheme, two distinct channel models approved by IEEE 802.15.4a TG are considered. According to the simulation results, we could conclude that the proposed scheme have performed better performance than the conventional method on the existence of multiple SOPs.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.93-100
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• 2009

This paper presents a step up four channel DC-DC converter using charge pump voltage doubler structure. Our goal is to design and implement DC-DC converter for capacitive SP4T RF MEMS switch in front end module in wireless transceiver system. Charge pump structure is small and consume low power 3.3V input voltage is boosted by DC-DC Converter to $11.3{\pm}0.1V$, $12.4{\pm}0.1V$, $14.1{\pm}0.2V$ output voltage With 10MHz switching frequency. By using voltage level shifter structure, output of DC-DC converter is selected by 3.3V four channel selection signals and transferred to capacitive MEMS devices. External passive devices are not used for driving DC-DC converter. The total chip area is $2.8{\times}2.1mm^2$ including pads and the power consumption is 7.52mW, 7.82mW, 8.61mW.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.49 no.1
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• pp.29-38
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• 2012

Due to the rapid development of network environment and wireless communication technology, the distribution of digital video has made easily and the importance of the protection for digital video has been increased. This paper proposes the digital video encryption system based on multiple chaos maps for MPEG-2 video encoding process. The proposed method generates secret hash key of having 128-bit characteristics from hash chain using Tent map as a basic block and generates $8{\times}8$ lattice cipher by applying this hash key to Logistic map and Henon map. The method can reduce the encryption overhead by doing selective XOR operations between $8{\times}8$ lattice cipher and some coefficient of low frequency in DCT block and it provides simple and randomness characteristic because it uses the architecture of combining chaos maps. Experimental results show that PSNR of the proposed method is less than or equal to 12 dB with respect to encrypted video, the time change ratio, compression ratio of the proposed method are 2%, 0.4%, respectively so that it provides good performance in visual security and can be applied in real time.

• Spatial Information Research
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• v.9 no.1
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• pp.51-72
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• 2001

It is frequently pointed out that the conventional field survey for natural environment has may limitations in terms of positional accuracy, real-time GIS data acquisition, and economic efficiency. The aim of this research was to develop an on site real-time mapping technique that enables the surveyor to input data in the field. The idea is based upon the recent trends in the field of Telecommunication and Information Technology that uses a GPS, wireless network computing, moving computing, etc. A virtual office approach has been adopted, in which a portable computer is linked to a GPS and field workers record data on the computer at the site and analyse data on site. This field mapping system has shown to be much less susceptible to the positional accuracy than that of th conventional approach. The Graphic User Interface, in particular, were ideally suited to combining positional information with attribute data which changes with every survey points. This interface allows users to interactively display and query GIS layers reproduced from the past survey results. The GIS database stored in the virtual office will serve to carry out a highly reliable survey since it could play a crucial role in identifying temporal and spatial changes occurred in the site. It is expected that integrated utilization of field data among the related agencies would be increased much more than before since the virtual office survey would be a powerful tool to ensure geometric fidelity in GIS database creation process. This paper also discusses the limitations and future direction of the present prototype research.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.5
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• pp.473-479
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• 2004

In this paper, power density in near field is calculated about analytic object which has comparatively large volume in considering used wavelength such as cellular base station antenna. Panel sector antenna which is used widespreadly in domestic cellular wireless communication system is modeled and electromagnetic field distribution in reactive near field region is calculated by FDTD (Finite Difference Time Domain) method. After that, antenna gain in far field region is obtain by near to far transformation. Power spectral density in radiated near field is calculated in applying to gain-based model with antenna gain in far field. Finally, compliance distance is obtained in considering the result from radiated near field calculation and basic restrictions on occupational and general public exposure limits in ICNIRP guideline. In the center of main radiating position, the result from gain-based model is -14.55 ㏈m and the result from surface scanning method is -15.75 ㏈m. When the losses from cables and connectors used in measurement are considered, the results from gain-based model and surface scanning method are nearly coincident.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.4
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• pp.3-11
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• 2016

In the environment of Internet of Things (IoT), IoT devices are limited by physical components such as power supply and memory, and also limited to their network performance in bandwidth, wireless channel, throughput, payload, etc. Despite these limitations, resources of IoT devices are shared with other IoT devices. Especially, remote management of the information of devices and patients are very important for the IoT healthcare service, moreover, providing the interoperability between the healthcare device and healthcare platform is essential. To meet these requirements, format of the message and the expressions for the data information and data transmission need to comply with suitable international standards for the IoT environment. However, the ISO/IEEE 11073 PHD (Personal Healthcare Device) standards, the existing international standards for the transmission of health informatics, does not consider the IoT environment, and therefore it is difficult to be applied for the IoT healthcare service. For this matter, we have designed and implemented the IoT healthcare system by applying the oneM2M, standards for the Internet of Things, and ISO/IEEE 11073 DIM (Domain Information Model), standards for the transmission of health informatics. For the implementation, the OM2M platform, which is based on the oneM2M standards, has been used. To evaluate the efficiency of transfer syntaxes between the healthcare device and OM2M platform, we have implemented comparative performance evaluation between HTTP and CoAP, and also between XML and JSON by comparing the packet size and number of packets in one transaction.