• Journal of Communications and Networks
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• v.14 no.6
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• pp.692-702
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• 2012

Supporting quality of service (QoS) guarantees for diverse multimedia services are the primary concerns for WiMAX (IEEE 802.16) networks. A scheduling scheme that satisfies QoS requirements has become more important for wireless communications. We propose a downlink scheduling scheme called adaptive priority-based downlink scheduling (APDS) for providing QoS guarantees in IEEE 802.16 networks. APDS comprises two major components: Priority assignment and resource allocation. Different service-type connections primarily depend on their QoS requirements to adjust priority assignments and dispatch bandwidth resources dynamically. We consider both starvation avoidance and resource management. Simulation results show that our APDS methodology outperforms the representative scheduling approaches in QoS satisfaction and maintains fairness in starvation prevention.

• ETRI Journal
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• v.37 no.5
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• pp.906-916
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• 2015

High-speed I/O channels require adaptive techniques to optimize the settings for filter tap weights at decision feedback equalization (DFE) read channels to compensate for channel inter-symbol interference (ISI) and crosstalk from multiple adjacent channels. Both ISI and crosstalk tend to vary with channel length, process, and temperature variations. Individually optimizing parameters such as those just mentioned leads to suboptimal solutions. We propose a joint optimization technique for crosstalk cancellation (XTC) at DFE to compensate for both ISI and XTC in high-speed I/O channels. The technique is used to compensate for between 15.7 dB and 19.7 dB of channel loss combined with a variety of crosstalk strengths from $60mV_{p-p}$ to $180mV_{p-p}$ adaptively, where the transmit non-return-to-zero signal amplitude is a constant $500mV_{p-p}$.

• ETRI Journal
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• v.36 no.6
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• pp.894-904
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• 2014

Blind mismatch correction of time-interleaved analog-to-digital converters (TI-ADC) is a challenging task. We present a practical blind calibration technique for low-computation, low-complexity, and high-resolution applications. Its key features are: dramatically reduced computation; simple hardware; guaranteed parameter convergence with an arbitrary number of TI-ADC channels and most real-life input signals, with no bandwidth limitation; multiple Nyquist zone operation; and mixed-domain error correction. The proposed technique is experimentally verified by an M = 4 400 MSPS TI-ADC system. In a single-tone test, the proposed practical blind calibration technique suppressed mismatch spurs by 70 dB to 90 dB below the signal tone across the first two Nyquist zones (10 MHz to 390 MHz). A wideband signal test also confirms the proposed technique.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.119-120
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• 2007

The operation of Interference cancellation algorithm for wireless repeater cancellation depends on either existing correlation properties between desired signal and reference signal or not At the time, due to the correlation properties at the ICS system, adaptive algorithms without considering system delay do not function properly. Thus, this system should be oscillated. In this paper, to solve these problems, we use the delayed least mean square algorithm. For the best performance of ICS, the system delays must be estimated. To efficiently estimate the delay of ICS, we use relations between bandwidth and correlation properties of the received signal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8B
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• pp.764-768
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• 2006

Over the years, the widespread proliferation of multimedia services has necessitated the development for an efficient network management. In this paper, we investigate the role of adaptive online pricing mechanism in order to manage effectively the network congestion problem. Our on-line approach is dynamic and flexible that responds to current network conditions. With a simulation study, we demonstrate that our proposed scheme enhances network performance and system efficiency simultaneously under widely diverse traffic load intensities.

• Journal of Communications and Networks
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• v.15 no.6
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• pp.635-644
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• 2013

Adaptive hypertext transfer protocol (HTTP) streaming has become a new trend to support adaptivity in video delivery. An HTTP streaming client needs to estimate exactly resource availability and resource demand. In this paper, we focus on the most important resource which is bandwidth. A new and general formulation for throughput estimation is presented taking into account previous values of instant throughput and round trip time. Besides, we introduce for the first time the use of bitrate estimation in HTTP streaming. The experiments show that our approach can effectively cope with drastic changes in connection throughput and video bitrate.

• Journal of Korea Multimedia Society
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• v.17 no.5
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• pp.631-639
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• 2014

Recently, research on Media Access Control (MAC) techniques for underwater acoustic communication has been conducted actively. For successful acoustic communication in underwater conditions, development of environmentally adaptive MAC techniques, which is taking narrow bandwidth, distance, depth, noise level, salinity, multipath and etc into account, is an especially important work. In this paper, knowledge based system is introduced not only to obtain adaptive and optimal communication parameters but also increase network efficiency and availability by requesting change of MAC techniques based on decisions from knowledge-based system Smart Decision Block (SDB). Computer simulations were also conducted to verify the performance of the proposed system in underwater conditions.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.178-180
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• 2003

이동 컴퓨팅 환경에서의 프록시는 트랜스코딩과 캐슁 등의 방법으로 미디어 스트림을 재가공하여 멀티미디어 스트리밍의 연속성을 보장해 준다. 프록시에 대한 기존의 접근들은 대체로 트랜스코딩과 캐슁을 별개의 주제로 다루었었다. 따라서 본 논문에서는 트랜스코딩과 캐슁을 통할하여 연동시킨 프록시 시스템 아키텍처를 구현하였다. 또한 서버와 프록시 사이의 전송 지연. 프록시에서의 미디어 스트림 재가공에 걸리는 지연, 프록시와 클라이언트 사이의 bandwidth 자원 등을 창조하여 adaptive한 트랜스코딩 및 캐슁을 할 수 있도록 해주는 transco-prefix caching에 대해 제안하였다. 그 결과 transco-prefix caching을 통하여 트랜스코딩과 캐슁의 장점들을 동시에 살필 수 있었다.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.21-24
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• 2000

End-to-end congestion control mechanism have been critical to the robustness and stability of the Internet. Most of today's Internet traffic is TCP, and we expect this to remain so in the future. TCP/IP is the intermediate transport layer candidate for today's applications. TCP uses an adaptive window-based flow control. The congestion avoidance and control algorithms deployed by TCP aims at using the available network bandwidth. This paper compares different congestion control policies, and proposes the new design mechanism for future public networks

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1997.06a
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• pp.49-54
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• 1997

For the purpose of a flexible coded video transmission over a heterogeneous network, we propose a new packetization method for coded video data. The proposed method achieves small degradation of coded picture quality in case of packet discard at the network node and does not require heavy processing load for bitrate control operation. Computer simulation results show that the bitrate reduction from 384 kb/s to 192 kb/s does not cause severe degradation in picture quality.