• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.256-259
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• 2007

Multicast and Broadcast Service (MBS) provides flexible and efficient transmission of the same information to multiple users using shared radio resources on WiBro network. The advantage of this service is to achieve the most efficient use of radio and network resources as well as to lessen sender's processing load when sending the same information to multiple users. Though radio resources are saved since a multicast or broadcast transport connection is associated with a service flow, it is hard to change MBS service channel dynamically. In this paper, we propose a Radio Resource Management System (RRMS) for supporting dynamic scheduling of MBS service channels. Results show that our proposed scheme using Radio Resource Allocation Table (RRAT) can efficiently support MBS services by providing dynamic schedule for MBS service channels.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.102-104
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• 2011

최근 비디오 스트리밍과 대화형 비디오 서비스 등과 같은 광대역 멀티미디어 서비스를 지원하기 위하여 Wimax와 같은 4G 무선네트워크 시스템 기술이 발전해 왔다. 4G 무선네트워크의 OFDM(Orthogonal Frequency Division Multiplexing)과 MIMO(multi Input Multi Output)은 사용자들에게 매우 유연한 QoS(Quality of Service) 서비스를 제공해 줄 수 있다.[1] 이 논문에서는 다양한 네트워크 상황에서 멀티캐스트 그룹에게 효율적인 방법으로 통신 자원을 할당하기 위해 OFDM 방법을 사용 하였다. 이에 본 논문에서는 한 셀(cell) 내의 서로 다른 멀티캐스트의 그룹의 다른 SNR(Signal to noise Ratio)의 사용자 분포에 따른 적응적인 scalable 비디오 멀티캐스트 방식을 제안한다. 더 나은 수신율을 가진 사용자는 최적의 MCS(Modulation and Coding Scheme) 할당을 통해 서로 다른 화질의 scalable 비디오 계층 중 높은 해상도의 비디오를 받을 수 있다. 논문에서는 전체 전송률을 최적화 하는 대신 전송받은 전체 비디오의 평균 화질을 최적화하는 방법을 제안한다.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.203-207
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• 2009

WiBro(Mobile WiMAX) has gained momentum as a top candidate to deliver the dream of full mobile wireless internet. To save cost and time in WiBro network design, simulation tool has to deploy powerful and useful analysis functions. If path loss model is more accurate, the reliability of analysis result of simulation tool will be much improved. So we emphasize on the importance of pathloss model in WiBro network design in this paper. For this, we introduce to three kinds of pathloss models(SUI, SCM, SCM-E) supposed properly models in WiBro RF (Radio Frequency) environment. Also we treat from basic theory to practical substance on the pathloss model to adopt WiBro network design/optimization. Finally, we describe about wireless network analysis tool named 'CellPLAN(R)' and techniques possible to improvethe accuracy of pathloss model.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.1
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• pp.117-123
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• 2012

This paper implements mobile Worldwide Interoperability for Microwave Access (WiMAX) receiver using Software Defined Radio (SDR) technology. SDR system is difficult to implement on the mobile handset because of restrictions that are computing power and under space constraints. The implemented receiver processes mobile WiMAX software modem on Open Multimedia Application Platform (OMAP) System on Chip (SoC) and Field Programmable Gate Array (FPGA). OMAP SoC is composed of ARM processor and Digital Signal Processor (DSP). ARM processor supports Single Instruction Multiple Data (SIMD) instruction which could operate on a vector of data with a single instruction and DSP is powerful image and video accelerators. For this reason, we suggest the possibility of SDR technology in the mobile handset. In order to verify the performance of the mobile WiMAX receiver, we measure the software modem runtime respectively. The experimental results show that the proposed receiver is able to do real-time signal processing.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.409-413
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• 2008

In this paper, we introduce a platform of advanced multiple antenna system based on orthogonal frequency-division multiplexing (OFDM). The advanced multiple antennas have beamforming gain using array antenna. In array antenna systems, received signal has phase delay caused distance of each antennas, therefore it should compensate with optimum weight vector which calculated by Lagrange algorithm. To implement the presented above procedures using Digital Signal Processor (DSP), we should fixed-point design. The performance of implemented platform is verified through MATLAB$^{(R)}$ simulations with various signal environments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.403-406
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• 2010

Nowadays, there's not made up of communication linking smoothly between the equipment for heterogenous. They are not decided a standardized communication method. The necessity for interlock with various wireless connection is raising its head. And user's terminal is developing with multiplex interface through them to use constant service. This paper study on the algorithm of the heterogenous. It's a terminal which have the technology for wireless access about mobility of seperating link technique.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.388-389
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• 2008

이중 이진 (double binary) 터보 디코더는 오류 정정 코드 중 하나로써, 높은 오류 정정 성능으로 인해 IEEE 802.16 표준 (WiMAX)에서 사용되고 있다. Maximum ${\alpha}$ posteriori probability (MAP) 디코딩 블록은 이중 이진 터보 디코더의 가장 핵심적인 블록으로, 본 논문은 이를 구현하기 위한 알고리즘 중 하나인 improved Max-Log-MAP 알고리즘에 대한 효율적인 하드웨어 구조를 제안한다. 제안하는 하드웨어 구조는 기존의 하드웨어 구조와 비교하였을 때, 오류 정정 성능은 동일만 반면, 구떤 복잡도는 감소한다. 0.13um 공정에서 입력 비트폭을 8비트로 가정하고 시뮬레이션 한 결과, 속도와 칩 면적, 그리고 소비전력 측면에서 각각 8.92%, 1845%, 그리고 29.93%의 향상을 보인다. 제안하는 구조를 WIMAX 설계에 적용하여 성능 개선을 이끌어낼 수 있다.

• Journal of Korea Multimedia Society
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• v.11 no.9
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• pp.1277-1285
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• 2008

In this paper, we first design the block diagram of the components for multi-mode SDR terminal based on SCA technology. It support both WIMAX mode and HSDPA mode. Then from the result of the analysis with a real SDR terminal implementation, we analyze which components of it have to be more lightweight. In addition we derive the general formula for the measure of dynamic reconfiguration time on the reconfiguration of the components. Finally we present a dynamic component-level reconfiguration algorithm with 22 stages based on the result of our analysis without violating the interface and procedure of SCA specification.

• Journal of KIISE:Information Networking
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• v.36 no.1
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• pp.1-11
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• 2009

In this paper, we propose a QoS routing protocol for WiMAX based wireless mesh networks. The proposed routing protocol is a proactive hop-by-hop QoS routing protocol. It can find an optimal route that satisfies QoS requirements using bandwidth and delay as QoS parameters. In this paper, we first present a network model for WIMAX based wireless mesh networks and explain why QoS routing protocol is the most appropriate for WiMAX based wireless mesh networks. Then, we propose a proactive hop-by-hop QoS routing protocol that meets QoS requirements of traffic flowing between mesh client and the gateway. The simulation results show that the proposed routing protocol outperforms QOLSR protocol in terms of end-to-end delay, packet delivery ratio and routing overhead.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.1000-1009
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• 2008

The purpose of this paper is to analyze the performance of MB-OFDM UWB system when the interference signal that can be WIMAX signal or 4 G system signal is received by detection limit of -80 dBm/MHz proposed in Korea for DAA(Detect And Avoid) to permit UWB in $3.1{\sim}4.8$ GHz. MB-OFDM UWB system supports two transmission modes; one is TFI(Time frequency Interleaving) mode that transmits OFDM symbols using different carrier frequency from symbol to symbol according to Time Frequency(TF) codes, the other is FFI(Fixed Frequency Interleaving) mode that transmits OFDM symbols using a specific carrier frequency. In this paper, we considered the TX average power and the synchronization structure to reflect the effect of frequency hopping according to TFC. Interference analysis results show that the WiMAX system is fenced thoroughly from UWB interference in domestic DAA regulation, but the performance of MB-OFDM UWB system is degraded seriously by an interference signal with the DAA detection limit even in frequency Hopping mode that can get frequency diversity effect.