• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.18-23
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• 2006

높은 데이터 전송률과 넓은 전송 대역을 제공할 수 있도록 표준화 된 시스템인 IEEE 802.16d[1]시스템에서는 여러 가지 서비스 클래스들을 이용하여 QoS를 보장해 줄 수 있을 것으로 기대하고 있다. 그러나, 효율적인 QoS를 제공하기 위해서는 스케줄링에 필요한 factor들을 적절하게 설정해야 하며, 시스템의 환경에 맞도록 변경해야 한다. 따라서, 본 논문에서는 IEEE 802.16d 시스템을 simulator (NS-2) [2]에 구현하고, IEEE 802.16f [3]에서 표준화한 MIB과 QoS를 고려한 MIB (Q-MAN MIB)을 구현하여 IEEE 802.16d 시스템과 연동하도록 구축한 네트워크 관리 시스템인 Q-MAN을 소개한다. Q-MAN 네트워크 관리 시스템을 통해 IEEE 802.16d 시스템의 QoS 제공 상태에 대한 모니터링이 가능하고, 스케줄링에 필요한 설정 값을 동적으로 변경이 가능하기 때문에 IEEE 802.16d 시스템의 효율을 극대화 시킬 수 있다.

• Journal of KIISE:Information Networking
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• v.35 no.5
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• pp.437-452
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• 2008

IEEE 802.16j MR networks introduce RSs (Relay Stations) within the IEEE 802.16 system in order to enhance the data throughput and extend the coverage. However, the current standardization defines that the BS (Base Station) controls MS's (Mobile Station's) handover, not only it induces the large signaling overhead but also handover latency could increase. In this paper, we propose a handover protocol in the MR networks where the high capability RSs that can process the MS's control functions are deployed. First, we classify the handover scenarios for the MR networks with the high capability RSs. Then, we define the MAC handover procedure, corresponding MAC management messages and the transmission routes for the proposed messages so that an 802.16e MS can perform seamless handover without noticing it is attached to an MR network. The simulation results show that the proposed handover protocol not only reduces the MAC management message overhead transferred through the wireless links compared to IEEE 802.16j/D1, which is the current standard for MR networks, but also performs the rapider and more secure MS handover than IEEE 802.16e and IEEE 802.16j/D1.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.666-673
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• 2006

In this paper, we evaluated the performance of 4 types of ARQ algorithms that have been adopted to offer reliable transmission between MAC layers. First of all, we implemented IEEE 802.16 ARQ algorithms with NS-2 network simulator and then evaluated the performances in various channel states. We used two performance measures to evaluate those performances. First, we used the total number of ARQ block in bytes that have been received without error. Second, we used ACK_Efficiency that is newly defined in this paper. From the results of simulation, we could be aware that each ARQ algorithm has different performance in a various channel states. For improving the transmission data rate in a specific channel state, we have to choose the right ACK interval as well as a suitable ARQ algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.2
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• pp.154-161
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• 2013

This paper presents the signal-to-interference plus noise ratio (SINR) estimation of IEEE 802.16m WirelessMAN-Advanced mobile station with simulation and implementation results. The downlink signal of IEEE 802.16m has two kinds of A-Preambles: the PA-preamble and the SA-preamble. This paper proposes the efficient method of estimating SINR with A-Preambles, by measuring noise power from PA-preamble and measuring interference power and signal power from SA-preamble. The proposed SINR measurement block contains important features such as subcarrier phase rotation elimination and simplified dB transform. The result of this paper is integrated to ETRI's IEEE 802.16m test mobile station, used for decision of adaptive-modulation-and-coding (AMC) and hand-over. It showed good measurement performance in simulation and unified system link test also.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.602-607
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• 2007

최근 4G 이동통신 시스템의 진화를 위한 단계로 기존의 이동통신 시스템을 유지하면서 효율 극대화를 통한 비용 절약 측면과 고 주파수 대역을 이용한 셀 간격의 협소화로 인해 나타나는 문제점에 대한 대안으로 커버리지 확대와 데이터 처리율 향상을 위한 IEEE 802.16j 표준화 작업이 진행 중에 있다. 향후 VoIP 서비스를 위한 업링크 스케줄링 기법으로 몇 가지가 IEEE 802.16j에 제시되어 있으나, 본 논문에서는 보이스 트래픽 특성 및 수학적 모델링을 통하여 기존 방법들보다 더 효율적인 대역 이용을 통해 같은 대역폭 대비 성능과 용량 면에서 개선된 스케줄링 기법인 eertPS를 제시하여 IEEE 802.16j Multi-Hop 환경하에서도 대역 효율적인 VoIP 서비스를 이용할 수 있도록 한다.

• Journal of the Korea Society for Simulation
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• v.15 no.3
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• pp.87-91
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• 2006

With the growth of the internet, the number of wireless internet users has increased continuously up to date. However, mobile communications could not support high speed transmission rate with cheap communication fee and wireless LAN has problems in providing terminal mobility and wide area connectivity, respectively. So the WMAN standard has been newly designed to make up for these limits. The initial 802.16 specification effectively offers a solution for providing fixed users with high speed wireless communication but it does not offer terminal mobility. So the 802.16d and 802.16e have been developed as the next generation solution that can support various PHY layer (SC, SCa, OFDM, OFDMA) and offer the terminal mobility. In this paper, we propose an effective uplink scheduling algorithm for VoIP with using UGS, and we show that our proposed algorithm is superior in view of average delay and management of uplink bandwidth to conventional rtPS algorithm and the scheme in reference, with using NS-2 network simulator.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.116-126
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• 2008

This paper describes the Dual-band WLAN transmitter with 2.4[GHz], 5[GHz]. Dual-band WLAN transmitter was designed at 2.4[GHz] and 5[GHz]. The Dual-band WLAN transmitter has a amplifier which operate at 2.4[GHz] and 5[GHz] frequency and two VCO(Voltage Controlled Oscillator) or VCO has a wide scope of frequency. these problem cause a size and a power consumption, The Dual-band WLAN transmitter module was proposed to solve these. the transmitter was designed to get output signals of IEEE 802.11a's 5.8[GHz] band signal using frequency multiplication way or to act a amplifier about the 2.4[GHz] band signal of IEEE 802.11b/g, according to inputed frequency and bias voltage that a eve using single transmission block. The output spectrum get the improved specification of ACPR of 4[dB], 6[dB], 16[dB] at +11[MHz], +20[MHz], +30[MHz] offset of center frequency compared to no linearization, was satisfied to transmit spectrum mask of IEEE 802.11a wireless Lan.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.490-496
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• 2007

This paper describes the design and implementation of an integrated LTCC front-end module for the IEEE802.11a WLAN applications by performing the behavioral-level simulation using measurement-based behavioral model. To meet the IEEE802.11a WLAN standard, a system transmitting 1024 symbols through 64-QAM process at the rate of 54Mbps should be implemented and nonlinear properties are confirmed by simulations of ACPR and EVM in this circumstance. The right offsets of ACPR which are 30MHz, 20MHz, and 11MHz distant from the center frequency of 5.8GHz are 49.36dBc, 36.90dBc, and 24.58dBc, respectively. The left offsets are 50.14dBc, 30.04dBc, and 28.85dBc, respectively and EVM is 2.94%. The size of the module implemented with LTCC five-layer substrates is $13.4mm{\times}14.2mm$. The measured characteristics of the transmitter show P1dB of 16.2dBm and power gain of 16.73dB. Those of the receiver exhibit the small signal gain of 16.24dB and noise figure of 7.83dB.

• Journal of KIISE:Information Networking
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• v.36 no.3
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• pp.256-262
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• 2009

In this paper, we propose a mechanism for increasing the handover performance of the IEEE 802.11 link layer. The mechanism reduces the number of scanning channels by referencing an AP map based on GPS. Also, by monitoring the SNRs of the mobile node and neighbor APs, it enables the handover to maintain a higher SNR than a given threshold. The experimental results establish that it has a disconnection ratio of 6.7% and an average SNR of 16.8 dB. It is 4.1% lower disconnection ratio and 26% higher SNR than the mechanism used by MadWifi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.5
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• pp.568-575
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• 2011

In this paper, we propose a small broadband antenna for mobile device. The proposed antenna consists of a printed rectangular monopole antenna and a parastic element connected to ground using narrow meander line and it is designed on a FR-4 substrate that has a thickness of 0.8 mm and a dielectric constant of 4.4. The FR-4 substrate's size is 50 mm${\times}$90 mm comparable to the real mobile device. The fabricated antenna's size is 12.5 mm${\times}$10.5 mm${\times}$0.8 mm and the measurement shows -10 dB return loss bandwidth of 2,200~6,000 MHz and gains of 2.86~4.01 dBi. Accordingly, the proposed antenna can support mobile device for WiBro(2,300~2,380 MHz), WLAN(IEEE 802.11b/g/n: 2,400~2,480 MHz, IEEE 802.11a: 5,150~5,825 MHz), and mobile WiMAX(IEEE 802.16e : 2,500~2,690 MHz, 3,400~3,600 MHz) service bands.