• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.12
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• pp.1644-1651
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• 1995

A data and clock recovery integrated circuit for MAC (Multiplexed Analog Component) TV standard is described. The chip performs the recovery of a system clock from a digitally encoded voice signal, clamping of a video signal for DC-level restoration, and precise gain control of a video signal in the presence of a large amplitude variation. A PLL (Phase Locked Loop) is used for timing recovery and a new gain control circuit is proposed which enhances its accuracy and dynamic range by employing two identical four-quadrant analog multipliers. The chip is designed in full custom with 1.5um BiCMOS technology, and layout verification is completed by post-simulation with the extracted circuit.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.11
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• pp.50-55
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• 2008

As more DSP functionalities are integrated into an embedded mobile device, power consumption and device reliability have emerged as crucial issues. As the complexity of mobile embedded designs increases very rapidly, verifying the functionality of the mobile devices has become extremely difficult. Therefore, designs with error (fault) tolerance are often required since these capabilities will enable the design to operate properly even with some existence of errors. However, designs with fault tolerance may suffer from significant power overhead since fault tolerance is often achieved by resource replication. In this paper, we propose a low power and fault tolerant MAC (multiply-and-accumulate) design. The proposed MAC design is based on multiple barrel shifters since MAC designs with barrel-shifters and adders are known to be excellent in terms of power consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1048-1057
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• 2015

In this paper, we propose a fast MAS reallocation method that can avoid reservation conflicts in the DRP process of WiMedia system in real time. WiMedia MAC DRP has been developed aimed QoS support for audio and video transmission that generate traffic periodically. The size variation of the video streaming data causes DRP reservation conflicts frequently, so that DRP could not support QoS of the video streaming service which is delay-sensitive. Fast MAS reallocation method could avoid reservation conflicts in real-time analyzing reservation requests information of the other device. Our proposed method is evaluated with test sequences using the software simulation and implemented in hardware/software with the integrated WiMedia MAC/PHY system.

• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.456-469
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• 2009

We develop a new wireless link quality metric, ECOT(Estimated Channel Occupancy Time) that enables a high throughput route setup in wireless mesh networks. The key feature of ECOT is to be applicable to diverse mesh network environments where IEEE 802.11 MAC (Medium Access Control) variants are used. We take into account the exact operational features of 802.11 MAC protocols, such as 802.11 DCF(Distributed Coordination Function), 802.11e EDCA(Enhanced Distributed Channel Access) with BACK (Block Acknowledgement), and 802.11n A-MPDU(Aggregate MAC Protocol Data Unit), and derive the integrated link metric based on which a high throughput end-to-end path is established. Through extensive simulation in random-topology settings, we evaluate the performance of proposed link metric and present that ECOT shows 8.5 to 354.4% throughput gain over existing link metrics.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.8
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• pp.1519-1527
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• 2007

In order to combat the security threats that sensor networks are exposed to, a cryptography protocol is implemented at sensor nodes for point-to-point encryption between nodes. Given that nodes have limited resources, symmetric cryptography that is proven to be efficient for low power devices is implemented. Data protection is integrated into a sensor's packet by the means of symmetric encryption with the Dragon stream cipher and incorporating the newly designed Dragon-MAC Message Authentication Code. The proposed algorithm was designed to employ some of the data already computed by the underlying Dragon stream cipher for the purpose of minimizing the computational cost of the operations required by the MAC algorithm. In view that Dragon is a word based stream cipher with a fast key stream generation, it is very suitable for a constrained environment. Our protocol regarded the entity authentication and message authentication through the implementation of authenticated encryption scheme in wireless sensor nodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1173-1183
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• 1998

This paper proposes an SS-PRMA protocol for the integrated voice and data services in the packet radio networks. In this protocol, the uplink logical channels are provided by combining the time slots and the spreding codes. SS-PRMA protocol contains some features of existing protocols such as PRMA, slotted ALOHA, and CDMA. In the proposed protocol, the voice terminals use a reservation mechanism, and the dta terminals use a slotted ALOHA scheme. The analysis and the simulation results show that most of the performances for the voice traffic can be achieved by employing a few distinct spreading codes and the data traffic throughput is closely related to the number of spreading code channels. Also it shows that the data traffic performance can be significantly improved by applying an FEC scheme to the data link layer.

• Journal of KIISE:Information Networking
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• v.27 no.1
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• pp.68-75
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• 2000

In this paper, a media access control protocol is proposed for voice/data integrated services in the packet CDMA network, and the performance of the proposed protocol is analyzed. The proposed protocol uses the spreading code sensing and the reservation schemes. This protocol gives higher priority to the delay-sensitive voice traffic than to the data traffic. A voice terminal can reserve an available spreading code during a talkspurt to transmit multiple voice packets. On the other hand, whenever a data packet is generated, the data terminal transmits the packet through one of the available spreading codes that are not used by the voice terminals. In this protocol, the voice packets do not come into collision with the data packets. The numerical results show that this protocol can increase the maximum number of voice terminals. The performance for the data traffic degrades by increasing the voice traffic load because of the low priority. But it shows that the data traffic performance can be increased in proportion to the number of spreading codes.

• Journal of the Korea Society of Computer and Information
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• v.12 no.3
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• pp.37-50
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• 2007

In this paper, we designed and implementation of the high speed neuron processor for real time object recognition in the making automatic system. and we designed of the PE(Processing Element) used residue number system without carry propagation for the high speed operation. Consisting of MAC(Multiplication and Accumulation) operator using residue number system and sigmoid function operator unit using MAC(Mixed Radix conversion) is designed. The designed circuits are descript by C language and VHDL(Very High Speed Integrated Circuit Hardware Description Language) and synthesized by compass tools and finally, the designed processor is fabricated in $0.8{\mu}m$ CMOS process. we designed of MAC operation unit and sigmoid proceeding unit are proved that it could run time 0.6nsec on the simulation and improved to the speed of the three times and decreased to hardware size about 50%, each order. The designed neuron processor can be implemented of the object recognition in making automatic system with desired real time processing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1141-1148
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• 1999

In this paper, an RRA_CDMA protocol is proposed for the integrated voice and data services in the cellular packet CDMA systems. The proposed protocol employs the RRA scheme. In the cellular CDMA systems, the backward logical channels are composed of time slots with multiple spreading codes per slot based on WB-TD-CDMA concept. When a voice terminal begins a talkspurt, it reserves one of the available spreading codes in the next slot and uses the reserved channel exclusively untill it ends the talkspurt. On th other hand, whenever a data terminal generates a packet, it selects an avaliable spreading code and transmits its packet. Throughout the results, it is shown that the system capacity increases in proportion to the number of spreading codes.

• Journal of Korea Multimedia Society
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• v.17 no.6
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• pp.687-696
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• 2014

An integrated ship area network has functionality of remote control and autonomous management of various sensors and instruments embedded or boarded in a ship. For such environment, an wireless bridge is essential to transmit control and/or managing information to sensors or instruments from a central integrated ship area network station. In this paper, one of reliable schemes of WiMedia based wireless bridge using relay cooperative transmission using WiMedia distributed MAC protocol is proposed to increase a communication reliability between cluster headers, irrespective of channel variation. Simulation results show that the proposed wireless bridge using relay cooperative transmission scheme increases communication reliability.