• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.12
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• pp.61-68
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• 2004

Wireless mobile communication systems request high speed mobility and high speed data transmission capability. In order to meet the requirements, OFDM(Orthogonal Frequency Division Multiplex) is mainly adopted in the physical layer of the wireless systems. In commercial wireless mobile systems, IEEE802.(11a, 16e, etc) series seem to be used as the modulation method. For supporting multiple air-interfaces in a wireless mobile system, different kinds of OFDM based modulation methods should be supported in one modem chip. It requires a variable point IFFT/FFT or reconfigurable IFFT/FFT processor. In this paper, we propose the design method of a reconfigurable IFFT/FFT processor. In addition, it is shown that a reconfigurable IFFT/FFT processor can he implemented by using the proposed method.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.4
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• pp.31-43
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• 1999

The main goal of this paper is to design a high performance SVP(Stack based Video Processor) for network applications. The SVP is a comprehensive scheme; 'better' in the sense that it is an optimal selection of previously proposed enhancements of a stack machine and a video processor. This can process effectively object-based video data using a S-RISC(Stack-based Reduced Instruction Set Computer) with a semi -general-purpose architecture having a stack buffer for OOP(Object-Oriented Programming) with many small procedures at running programs. And it includes a vector processor that can improve the MPEG coding speed. The vector processor in the SVP can execute advanced mode motion compensation, motion prediction by half pixel and SA-DCT(Shape Adaptive-Discrete Cosine Transform) of MPEG-4. Absolutors and halfers in the vector processor make this architecture extensive to a encoder. We also designed a VLSI stack-oriented video processor using the proposed architecture of stack-oriented video decoding. It was designed with O.5$\mu\textrm{m}$ 3LM standard-cell technology, and has 110K logic gates and 12 Kbits SRAM internal buffer. The operating frequency is 50MHz. This executes algorithms of video decoding for QCIF 15fps(frame per second), maximum rate of VLBV(Very Low Bitrate Video) in MPEG-4.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.79-84
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• 1996

In this paper, adaptive correlator model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of adaptive correlator uswing backpropagation neural network improved than that of adaptive transversal filter of direct sequence spread spectrum considering of co-channel and narrow-band interference. Bit error ratio of adaptive correlator using backpropagation neural network is reduced about $10^{-1}$ than that of adaptive transversal filter where interference versus signal ratio is 5 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1202-1210
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• 2005

For the efficient and safe navigation management of ships cruising across oceans, international maritime law environments have been reinforced and the demand of information sharing between ships and shore has also been increasing. According to these environments and demand. researches about digital ships, ship integration, and ship integration networks have been active recently in US and Europe. In this raper, we first investigate about the proper ship integration platform, and then design and implement a ship integration network based upon the ship integration platform. We construct networks connecting various devices and systems into a layered architecture, and design an integration protocols. Based upon this architecture and protocols, we implement an ship integration system which manages all data and information of ship in a standardized platform and support ship-shore information sharing through which the more efficient and safer ship navigation management are supported with help from shore. We test our ship integration system by applying it to real operating ships and we find our system reliability and verify the efficiency of ship-shore information sharing and management.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.923-930
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• 2004

Wireless sensor networks is a core technology of ubiquitous computing which enables the network to aware the different kind of context by integrating exiting wired/wireless infranet with various sensor devices and connecting collected environmental data with applications. However it needs an energy-efficient approach in network layer to maintain the dynamic ad hoc network and to maximize the network lifetime by using energy constrained node. Cluster-based data aggregation and routing are energy-efficient solution judging from architecture of sensor networks and characteristics of data. In this paper. we propose a new distributed clustering algorithm in using distance from the sink. This algorithm shows that it can balance energy dissipation among nodes while minimizing the overhead. We verify that our clustering is more en-ergy-efficient and thus prolongs the network lifetime in comparing our proposed clustering to existing probabilistic clustering for sensor network via simulation.

• The KIPS Transactions:PartC
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• v.12C no.6 s.102
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• pp.799-808
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• 2005

This paper proposes low latency handover procedure for seamless connectivity and QoS support between wired (e.g. Ethernet) and wireless (e.g. WLAN, WiBro(802.16-compatible), CDMA) networks by the mobile-assisted and server-initiated handover strategy. It is assumed that the server decides the best target network considering network status and user preferences. In this algorithm a mobile terminal associates with the wireless link decided at the server In advance and receives CoA as well. When handover occurs without the prediction in wired networks, the server performs fast binding update using physical handover trigger through the MIH(media independent handover) function. As a result, a mobile terminal does not need to perform L2 and L3 handover during handover so that this procedure decreases handover latency and loss.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.751-762
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• 2000

In the forthcoming next generation highspeed networks, the provisioning of broadband mobile multimedia services is the most important issue while an efficient network management architecture, which can manage the network resources efficiently, is essential. The next generation highspeed networks will be composed of the ATMand SDH-based transport network systems and the H-based interworking systems. The management functions of these network systems are implemented various technologies, such as TMN and SNMP. In order to integrate these network resources efficiently with heterogeneous management functions, the distributed network management architecture such as TINA is most appropriate. In this pape, we propose an interworking architecture for TINA manager and TMN agent. where the TINA-based EML subnetwork management operations mapped into the related management operations of the TMN NE agent. The proposed interworking architecture is simpler than JIDM, and the processing overhead is minimized.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6B
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• pp.433-442
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• 2012

We have proposed a solution to multicast services and an advanced quality of service (QoS) mechanism on a packet transport system (PTS) based on PBB-TE. The point-to-multipoint (PtMP) connection in the PBB-TE system have been realized by grouping point-to-point (PtP) PTL trunks and mapping a BSI onto the PtP PTL trunks using a multicast backbone destination address. To provide end-to-end QoS of the PtMP services, the hierarchical QoS scheme for backbone service instances and connection-oriented paths has been implemented in the PTS. For providing different capabilities for service selection and priority selection, the PTS offers to customers three basic types of the port-based, C-tagged, and S-tagged service interface defined by the IEEE 802.1ah. To offer to customers different capabilities of the layer 3 applications and services, moreover, an IP-flow service interface have been added. In order to evaluate traffic performance for PtMP services in the PTS, the PtMP throughputs for the link capacity of 1 Gbps at the four service interfaces were measured in the leaves of the ingress edge node, the transit node, and the egress edge node. The throughputs were about 96 % because the B-MAC overhead of 22 bytes occupies 4% of the 512-byte packet. The QoS performance is ability to guarantee an application or a user a required bandwidth, and could be evaluated by the accuracy of policing or shaping. The accuracy of the policing scheme and the accuracy of the shaping scheme were 99% and 99.3% respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1151-1168
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• 2009

Improving packet loss does not necessarily coincide with the improvement in user perceivable QoS because each frame carries different degree of importance. We propose Significance-aware packet scheduling (SAPS) to maximize user perceivable QoS. SAPS carries out two fundamental issues of packet scheduling: "What to transmit" and "When to transmit?" To adapt to the available bandwidth, it is necessarily to transmit the subset of the data packets if the entire set of packets can not be transmitted. "Packet Significance" quantifies the importance of the frame by elaborately incorporating frames' dependency. Greedy approach is used in selecting packets and transmission schedule is determined based on the Packet Significance. The proposed scheme is tested using publicly available MPEG-4 video clips. Decoding engine is embedded in the simulation software and user perceivable QoS is exposeed in termstermiSNR. Throughout the simulation based experiment, the performance of the proposed scheme is compared two other schemes: Size-based packet scheduling and Bit-rate based best effort packet scheduling. SAPS successfully incorporates the semantics of a packet and improves user perceivable QoS significantly. It successfully provides unequal protection to more important packets.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.5
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• pp.351-359
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• 2009

Recently with increase of data in the Internet, platform technologies that can process huge data effectively such as Google platform and Hadoop are regarded as worthy of notice. In this kind of platform, there exist network I/O overheads to send task outputs due to the MapReduce operation which is a programming model to support parallel computation in the large cluster system. In this paper, we suggest applying of TIPC (Transparent Inter-Process Communication) protocol for reducing network I/O overheads and increasing network performance in the distributed computing environments. TIPC has a lightweight protocol stack and it spends relatively less CPU time than TCP because of its simple connection establishment and logical addressing. In this paper, we analyze main features of the Hadoop-based distributed computing system, and we build an experimental model which can be used for experiments to compare the performance of various protocols. In the experimental result, TIPC has a higher bandwidth and lower CPU overheads than other protocols.