• Journal of the Korea Safety Management & Science
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• v.2 no.4
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• pp.165-176
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• 2000

Broadband networks are designed to support a wide variety of services with different traffic characteristics and demands for Quality of Services. Bandwidth allocation methods can be classified into two major categories： static and dynamic. In static allocation, bandwidth is allocated only at call setup time and the allocated bandwidth is maintained during a session. In dynamic allocation, the allocated bandwidth is negotiated during a session. The purpose of this paper is to develop policies for deciding and for adjusting the amount of bandwidth requested for a best effort connection over such as ATM networks.. This method is to develop such policies that a good trade off between utilization and latency using cell delay variation to the forecast the incoming traffic in the next period. The performances of the different polices are compared by simulations.

• Proceedings of the Safety Management and Science Conference
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• 2000.11a
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• pp.131-134
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• 2000

Broadband networks are designed to support a wide variety of services with different traffic characteristics and demands for Quality of Services. Bandwidth allocation methods can be classified into two major categories: static and dynamic. In static allocation, bandwidth is allocated only at call setup time and the allocated bandwidth is maintained during a session. In dynamic allocation, the allocated bandwidth is negotiated during a session. The purpose of this paper is to develop policies for deciding and for adjusting the amount of bandwidth requested for a best effort connection over such as ATM networks. This method is to develop such policies that a good trade off between utilization and latency using cell delay variation to the forecast the incoming traffic in the next period. The performances of the different polices are compared by simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.2
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• pp.268-279
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• 1997

In this paper, we show the movable boundary (MB) method is the effective bandwidth allocation strategy for the ABR service among existing bandwidth allocation methods. The MB method can gurantee the QOS requirement according to the service priority and improve bandwidth utilization using the characteristics of the ABR service. The threshold values of the MB, which have an important effect upon connection blocking probability(CBP) performance of each service, are obtained by simulation. The MB method with the fixed thresholds, however, may not have good performance to variation of input traffic parameters. We suggest the dynamic MB method which changes the threshold values adaptively according to the required bandwidth of input traffic. We also show that the dynamic MB method can urantee the CBP performance according to the service priority regardless of variation of input traffic parameters.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.48-58
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• 2015

The bandwidth enhancement of an aperture coupled microstrip patch antenna(ACMPA) with a high permittivity feed substrate suitable for the integration with MMIC is investigated using variation of an aperture width. As an aperture width increases, the 10 dB return loss bandwidth increases due to the increase of the mutual resonance region between a patch resonance and an aperture resonance. The bandwidth of an ACMPA with extended aperture width is increased up to 35.3 % from 20.8 % of the ACMPA with an aperture of a typical aspect ratio 10:1. The degradation of the radiation characteristics of an ACMPA due to the increase of an aperture width is very small.

• Journal of electromagnetic engineering and science
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• v.1 no.2
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• pp.166-172
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• 2001

A novel RF tunable bandpass filter structure using dielectric resonators and varactor diodes is considered for the optimization to achieve constant bandwidth with minimum passband insertion loss. The coupling between resonators is realized by coupling windows and series lumped L, C elements are used to realize the input/output stage couplings. A 5 poles, 0.01 dB ripple Chebyshev type filter tuned from 800 MHz~900 MHz is designed and presented in this paper. The passband bandwidth for the design is 10 MHz (fractional bandwidth = 1.2 %). Experimental results show that the 3 dB passband bandwidth variation is 12.04 MHz~12.16 MHz (less than 1 %) and passband insertion loss is 15 dB~7 dB depending on the tuning voltages.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.43-45
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• 2004

In this paper, new design concept of MEMS gyroscope using multi mass system is proposed. The gyroscope having wide bandwidth was designed utilizing the multi mass system in order to reduce the degradation of the performance by resonance variation. The multi mass system has more than two masses and separates the resonant peak of each mass. Using MATLAB, the variation of bandwidth and driving displacement according to mass ratio of the multi mass system was analyzed. This result was compared with that of current single mass system gyroscope. In the 7 kHz resonant frequency design, the multi mass system has 395.3Hz bandwidth, which is six times larger than single mass system bandwidth, 58.5 Hz.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.441-446
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• 2003

Earlier efforts on optical access concentrated on the design of PONs for the collection and distribution portion of the access network. The PON architecture is very simple but it requires a MAC protocol for control of upstream traffic. The MAC protocol must support QoS (Quality of Service) administration function by various traffic class, efficient dynamic bandwidth assignment function, CDV (Ceil Delay Variation) minimization function etc. This paper proposes a dynamic bandwidth assignment algorithm of the MAC protocol for a broadband access network using an Ethernet Passive Optical Network supporting various traffic class. We compare our proposed with MDRR algorithm using simulation, and confirmed that our proposed Request-Counter algorithm produces shorter average cell delay.

• Journal of Power Electronics
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• v.10 no.4
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• pp.382-387
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• 2010

This paper presents a novel design method for determining the PID gains of a speed controller for a servo system compensating variations in bandwidth at a low speed. The variations in bandwidth of a speed controller are measured at a low speed and the relationship between the bandwidth and the damping ratio are verified by determining the location of the closed loop pole. The proposed algorithm uses the z-transform of a plant and speed controller and applies the time-varying sampling method for determining the PID gains of the speed controller at low speed. The magnitude and the phase condition are considered for finding a suitable control gain. The usefulness and effectiveness of the proposed method is demonstrated through experimental results such as low speed control and robust disturbance responses.

• ETRI Journal
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• v.23 no.4
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• pp.177-189
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• 2001

Multicarrier DS-CDMA is an effective approach to combat fading and various kinds of interference. In this paper, we present an overlapped multicarrier DS-CDMA system, wherein each of the rate 1/M convolutionally-encoded symbols is also repetition coded and transmitted using overlapped multicarriers. However, since the frequency spectrums of successive carriers are allowed to overlap, the transmission bandwidth is more efficiently utilized. The effect of the overlapping percentage between successive carriers of a multicarrier DS-CDMA system on the performance is investigated to determine the overlapping percentage showing the best performance. We suggest two methods for sub-band overlapping variation. One is to allow variation of sub-band overlapping percentage when the total number of subcarriers is fixed. The other is to increase the number of sub-bands (the number of repetitions R) with fixed sub-band bandwidth. Given a total number of subcarriers MR, we show that the BER variation is highly dependent on the roll-off factor ${\beta}$ of a raised-cosine chip wave-shaping filter irrespective of convolutional encoding rate 1/M and repetition coding rate 1/R. We also analyze the possibility of reduction in total multi-user interference by considering the variation of both the roll-off factor ($0<{\beta}{\leq}1$) and the sub-band overlapping factor ($0<{\lambda}{\leq}2$), and show that the proposed system may outperform the multicarrier DS-CDMA system in [3].

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2A
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• pp.86-96
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• 2006

In recent year, EPON(Ethernet PON) system is expected to be more attractive solutions for high speed, broadband access networks in next generation access networks due to the conversionce of low-cost ethernet equipment and low-cost fiber infrastructure. Upstream channel control algorithm is essential to hare upstream bandwidth in EPON. In this paper, we suggest HUHG(High Utilization and Hybrid Granting) algorithm for supporting high bandwidth utilization and QoS for different service class. This algorithm improves bandwidth utilization as removing or diminishing idle time of upstream channel using characteristics of fixed EF(Expedited Forwarding) sub-cycle. The proposed algorithm also minimizes the packet delay and delay variation of EF class. We conduct detailed simulation experiments using OPNET to study the performance and validate the effectiveness of the proposed algorithm.