• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.127-133
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• 2011

This study proposed the PHB mapping model for combining services with DiffServ in the MPLS network capable of high-speed switching, and the effective differential bandwidth service model in the MPLS network on the basis of the proposed mapping model. The result of simulation on the service model using PRI showed that the transmission rate was achieved as much as the assigned bandwidth regardless of the increase of traffic as far as the EF PHB did not exceed the assigned bandwidth at the peak rate when the overall traffic increased.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.1
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• pp.27-32
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• 2015

In this paper, a mushroom typed electromagnetic band gap (EBG) structure to be inserted in the printed circuit board (PCB) inner layer in order to stabilize the PCB power line is proposed for global-navigation satellite service (GNSS). In designing the proposed EBG structure, the target stop-bandwidth was designed from 1.55GHz to 1.81GHz including GNSS and mobile communication-related frequency bandwidth. In this bandwidth, the insertion loss(S21) was observed below about -40dB. From the simulation results, it is expected that the stabilization of power delivery network (PDN) structure in the PCB circuit design should be improved and the effective correspondence to EMI will be helpful.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7C
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• pp.654-662
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• 2009

Video streams for mobile video streaming can be encoded to fit the available network bandwidth by controlling three factors: temporal resolution, spatial resolution, and picture quality. The controlling of picture quality by modifying the quantization parameter (QP) is most widely used. In this paper, we demonstrate that reducing the spatial resolution adaptively can be more efficient in terms of picture quality and energy consumption in low bit-rate environment, and present a model to find the optimal spatial resolution for the available bandwidth. Adaptive spatial resolution control scheme is especially effective when the bandwidth between the video server and the mobile device varies considerably with time, and when the mobile device is sensitive to energy consumption. Our scheme can improve the picture quality by approximately O.5dB and reduce energy consumption by more than 50% compared to the conventional video coding in low bit-rate environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.387-393
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• 2007

In this paper, we propose the load control procedure for WiBro system in order to keep the data traffic throughput maximum. The transmitter at a mobile terminal can estimate maximum available power for each user and then the maximum number of subchannels can be calculated considering the total available power. The data traffic throughput and the total throughput (the sum of signaling traffic and data traffic throughput) are considered. As the number of bandwidth requests per frame increases, the data traffic throughput can significantly decrease. Therefore, the load control procedure is indispensible to maintain the data throughput at the maximum level. So, we propose the load control procedure to prevent data traffic throughput from decreasing and evaluate the proposed procedure through the computer simulation under the multi-user environment. The maximum throughput can be maintained by applying the proposed procedure.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.71-77
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• 2009

A novel phase-locked loop(PLL) architecture with multiple charge pumps for fast locking has been proposed. The proposed PLL has three charge pumps. The effective capacitance and resistance of the loop filter can be scaled up/down according to the locking status by controlling the direction and magnitude of each charge pump current. The fast locking PLL that changes its loop bandwidth through controlling charge pumps depending on locking status has been designed. The capacitor usually occupying the larger portion of the chip is also minimized with the proposed scheme. Therefore, the PLL size of $990{\mu}m\;{\times}\;670{\mu}m$ including resistors and capacitors at the bandwidth of 29.9KHz has been achieved. It has been fabricated with 3.3V $0.35{\mu}m$ CMOS process. The locking time is less than $6{\mu}s$ with the measured phase noise of -90.45dBc/Hz @1MHz at 851.2MHz output frequency.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.1-8
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• 2011

In this paper, a water tank experiment using Binary Frequency Shift Keying (BFSK) method for text transmission performance by water surface fluctuation is conducted. Water surface fluctuation and delay spread which affect the channel coherence bandwidth is a limiting factor in underwater acoustic communication. The amplitude fluctuation and delay spread the smooth surface and fluctuation surface, were identified. The effective delay spread of both cases are 5ms, 4ms corresponding to the coherence bandwidth of 200Hz, 250Hz, respectively. The bit error rate of BFSK modulated text transmission is about $10^{-4}$ in less than 200bps in smooth surface but less than 250bps in fluctuation surface. Therefore, this experiment shows that the water surface fluctuation is important factor determining the performance of the underwater acoustic transmission.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1208-1213
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• 2010

In this paper, a microstrip balun-BPF of slotted-square-patch type is proposed. The conventional balun-BPF has some drawbacks of narrow bandwidth and high insertion loss. In order to improve these weak points, we used a square patch in designing balun-BPF on which two slots intersecting perpendicularly and one corner-edge perturbation are adopted. This structure allows one of the most effective use of the patch space so that the insertion loss can be decreased. Changing the slot lengths is use to control the operating frequency and the bandwidth of the balun-BPF. A fabricated balun-BPF shows wide bandwidth of 300 MHz(12.7 %), small insertion loss of 0.56 dB, phase difference of $184^{\circ}{\pm}15^{\circ}$ and amplitude imbalances of within 1 dB between two output ports at 2.4 GHz band.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.93-99
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• 2004

According to rapid increment of demand for wireless Local Area Network (LAN), the HyperLAN of 5.1-533GHz and 5.725-5.825GHz is newly allocated for wireless LAM in many regions over the world. Also, because most of mobile communication equipments are small, the size of antenna is important factor of effective design. In this paper, the compacted and wide bandwidth antenna is designed for wireless LAN at 5GHz band. Although the structure of U-shaped slot antenna is simple, It has large bandwidth of $10-40\%$. Also, the U-slot antenna has good radiation pattern. However, in general, the size of U-slot antenna is large. Therefore, it is difficult to apply to wireless equipment such as PDA and Notebook. This proposed antenna has a wide bandwidth by U-shaped slot in rectangular patch and is compacted by using two layered dielectric substrates and foam. For the design of U-slot antenna, the Finite Difference Time Domain method is applied. Also, the method of MPI parallel program is used for the enhancement of the analyzing speed of the FDTD method.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.2
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• pp.47-55
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• 2003

In this paper, the performance of DS-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz,5MHz) and different channel environments (rural, urban) in wideband multipath channel. For the analysis of smart antenna system, the vector channel having the spatio-temporal correlation is modeled as a time-variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. Several multipath is within one chip are distingushed into each one and the strongest signal is selected, DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1387-1394
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• 2005

In this paper, we propose and the call admission control mechanism that can improve the capacity of the wireless system for the non-uniform traffic load distribution based intelligent information in multiple cellular CDMA environment. The number of mobile stations that can be served simultaneously in a base station is limited by the amount of total interference received in CDMA system. Further, the average number of mobile stations in each cell may not be uniformly distributed. In this paper, considering this factors, the call admission control mechanism using the effective bandwidth concept is adapted to improve the system capacity of non-uniform traffic load distribution based intelligent information. Thus, the bandwidth for a new call can be varied dynamically for reducing the blocking rate of new calls and the dropping rate of handoff calls. The suggested call admission control mechanism is experimented through simulation by dynamically assigning the bandwidth to new and handoff calls. The simulation results show that the proposed call admission control mechanism can accommodate more mobile stations than the other methods in multiple cellular CDMA environment.