• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6B
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• pp.553-562
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• 2003

Supporting QoS (Quality of Service) for the multimedia applications becomes an important issue as the demand of multimedia applications increases. Thus, it is necessary for the application layer to have an efficient congestion control algorithm, which can support the multimedia applications' QoS requirements. In this paper, we propose a new application layer congestion control algorithm, called RRC-OTT (Receiver-based Rate Control with One-way Trip Time). RRC-OTT algorithm differs from the previously proposed algorithms in that the receiver takes the responsibility of the network congestion control. Thus, RRC-OTT algorithm can not only precisely estimate the network congestion using OTT (one-way Trip Time), but reduce the work load from the sender (e.g., the web server). Our simulation study shows that RRC-OTT algorithm can maintain the comparable link utilization to the previously proposed algorithms and keep the packet jitter low, which thus can help enhance the quality of multimedia applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.9
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• pp.1633-1637
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• 2008

A protocol is proposed to control the rate of each subcarrier in OFDM-based wireless network systems. The proposed protocol adds an OFDM symbol in CTS frame defined in IEEE 802.11 standard. A receiver determines the rate of its subcarrier after it receives the RTS frame. The determined rate is added to OFDM symbol in CTS frame. In order to synchronize the rate information between the sender and the receiver, error recovery process is proposed. The performance improvement of the proposed method is shown by numerical results.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.899-910
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• 2013

This paper presents a novel lateral stability control system for electric vehicle based on sideslip angle estimation through Kalman filter using the integration of a single antenna GPS receiver and yaw rate sensor. Using multi-rate measurements including yaw rate and course angle, time-varying parameters disappear from the measurement equation of the proposed Kalman filter. Accurate sideslip angle estimation is achieved by treating the combination of model uncertainties and external disturbances as extended states. Active front steering and direct yaw moment are integrated to manipulate sideslip angle and yaw rate of the vehicle. Instead of decoupling control design method, a new control scheme, "two-input two-output controller", is proposed. The extended states are utilized for disturbance rejection that improves the robustness of lateral stability control system. The effectiveness of the proposed methods is verified by computer simulations and experiments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.7
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• pp.2354-2370
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• 2015

The advantages of employing SCTP-based Concurrent Multipath Transfer (CMT) have been demonstrated to be very useful for data delivery over multi-homed wireless networks. However, there is still significant ongoing work addressing some remaining limitations and challenges. The most important concern when applying CMT to data delivery is related to handling packet reordering and buffer blocking. Another concern on this topic is that current sender-based CMT solutions seldom consider balancing the overhead and sharing the load between the sender and receiver. This paper proposes a novel Receiver-driven Cooperation-based Concurrent Multipath Transfer solution (CMT-Rev) with the following aims: (i) to balance overhead and share load between the sender and receiver, by moving some functions including congestion and flow control from the sender onto receiver; (ii) to mitigate the data reordering and buffer blocking problems, by using an adaptive receiver-cooperative path aggregation model, (iii) to adaptively transmit packets over multiple paths according to their receiver-inspired sending rate values, by employing a new receiver-aware data distribution scheduler. Simulation results show that CMT-Rev outperforms the existing CMT solutions in terms of data delivery performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.6
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• pp.1147-1165
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• 2011

We present a simple and cost effective rate control scheme for streaming video over a wireless channel by using the information of mobile devices' buffer level. To prevent buffer fullness and emptiness at receivers, the server should be able to adjust sending rate according to receivers' buffer status. We propose methods to adjust sending rate based on the buffer level and discrete derivative of the buffer occupancy. To be compatible with existing network protocols, we provide methods to adjust sending rate by changing the inter-packet delay (IPD) at the server side. At every round-trip time, adjustments of sending rate are made in order to achieve responsiveness to sudden changes of buffer availabilities. A series of simulations and the prototype system showed that the proposed methods did not cause buffer overflows and it can maintain smoother rate control and react to bandwidth changes promptly.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.69-72
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• 2000

This paper shows the more improved design of MRI receiver compared to conventional one based on Elscint Spectrometer. At first, the low-cost ADC is 16 bits, 3MHz sampling A/D converter Comparing to conventional one with signal bits of 14 bits, this device with those of 16 bits helps getting Improved the image resolution improved. If frequency is designed centering around 7.6 MHz to be satisfied in 10 MHz of maximum input bandwidth of ADC. For 1st demodulation, fixed IF is used for the purpose of the implementing multi nuclei system. Control parts & partial digital parts are integrated on one chip(FPGA). In DDC(Digital Down Converter), we got required bandwidth of LPF by controlling its decimation rate. With above considerations, we designed optimal receiver for high resolution imaging to be implemented through PC interface & experimental test of receiver of MRI after receiver's fabrication.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.6
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• pp.286-295
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• 2006

This paper presents a design of a real-time software GPS receiver which runs on a PC. The software GPS receiver has advantages over conventional hardware based receivers in terms of flexibility and efficiency in application oriented system design and modification. In odor to reduce the processing time of the software operations in the receiver, a shared memory structure is used with a dynamic data control, and the byte-type IF data is processed through an Open Multi-Processing technique in the mixer and integrator which requires the most computational load. A high speed data acquisition device is used to capture the incoming high-rate IF signals. The FFT-IFFT correlation technique is used for initial acquisition and FLL assisted PLL is used for carrier tracking. All software modules are operated in sequence and are synchronized with pre-defined time scheduling. The performance of the designed software GPS receiver is evaluated by running it in real-time using the real GPS signals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7B
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• pp.481-488
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• 2005

As the demand on the multimedia application increases, the congestion control algorithm for the multimedia applications becomes an important research issue. The ultimate goal of congestion control is to adapt the trans-mission rate at the sender to the mont of network resource available on the forward path. In general, the congestion control algorithms use the round trip time(RTT) to estimate the network congestion on the forward path. however, since the RTT includes the delay on both forward and backward paths, it is possible for the algorithms using the RTT to make a wrong decision such as deciding the congestion on the forward path due to the congestion built on the backward path. In this paper, we enhance the performance of RRC-OTT(Receiver-based rate control with one-way Trip Time) algorithm, which uses the one-way trip time(OTT) to estimate the network congestion. By separating the estimation mechanism on the forward path from the backward path, the performance of RRC-OTT algorithm is hardly affected by the congestion built on the backward path.

• Journal of Communications and Networks
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• v.6 no.4
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• pp.376-386
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• 2004

In ad hoc networks, loss-based congestion window progression by the traditional means of duplicate ACKs and timeouts causes high network buffer utilization due to large bursts of data, thereby degrading network bandwidth utilization. Moreover, network-oriented feedbacks to handle route disconnection events may impair packet forwarding capability by adding to MAC layer congestion and also dissipate considerable network resources at reluctant intermediate nodes. Here, we propose a new TCP scheme that does not require the participation of intermediate nodes. It is a purely end-to-end scheme using TCP timestamps to deduce link conditions. It also eliminates spurious reductions of the transmission window in cases of timeouts and fast retransmits. The scheme incorporates a receiver-oriented rate controller (rater), and a congestion window delimiter for the 802.11 MAC protocol. In addition, the transient nature of medium availability due to medium contention during the connection time is addressed by a freezing timer (freezer) at the receiver, which freezes the sender whenever heavy contention is perceived. Finally, the sender-end is modified to comply with the receiver-end enhancements, as an optional deployment. Simulation studies show that our modification of TCP for ad hoc networks offers outstanding performance in terms of goodput, as well as throughput.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.176-180
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• 2004

The ST-segment that the beginning part of T wave is the important diagnostic parameter to finding myocardial ischemia. Abnormal ST appears in two types. One is the level change, and the other is the pattern change. In this paper, we describe the monitoring of abnormal ST using PC based system. Hardware of this system consists of transmitter, receiver and PC. The function of transmitter is measuring ECG in three channels which are selected manually and transmitting the data to receiver by digital radio way. Connection with receiver and PC is by RS232C, and the data received on the PC is analyzed automatically by ECG analysis algorithm and saved to file. In the algorithm part for detecting abnormal ST, ST-segments are approximated by a polynomial. This method can detect all of the deviation and pattern change of ST-segment regardless the change in the heart rate or sampling rate. To gain algorithm reliability, the method rejects distorted polynomial approximation by calculation the difference between the approximated ST-segment and original ST-segment. In pre-signal processing, the wavelet transformation separates high frequency bands including QRS complex from the original ECG. Consequently, the process improves the performance of detecting each feature points.