• Journal of the Korean Society of Industry Convergence
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• v.20 no.3
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• pp.205-212
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• 2017

This paper focuses on worst-case delay analysis of the time-triggered IEEE 802.15.4 protocol to satisfy the industrial quality-of-service (QoS) performance. The IEEE 802.15.4 protocol is considered to be unsuitable for industrial networks because its medium access control method is contention-based CSMA/CA, which exhibits unstable performance with an unbounded delay distribution under heavy traffic. To avoid these limitations, this paper presents a time-triggered version of the nonbeacon-enabled network of IEEE 802.15.4 that relies on a time division multiplexing access (TDMA) method implemented in the application layer without any modification of specification. The timing analysis of this time-triggered IEEE 802.15.4 was executed, and the worst-case transmission delay was calculated. Based on this analysis, the time-triggered IEEE 802.15.4 is a promising alternative for wireless industrial networking.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.3
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• pp.80-90
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• 2004

국내 2.3 GHz 휴대인터넷의 본격화에 즈음하여 이동통신에서의 초고속 무선인터넷에 대한 관심이 높아지고 있다. 본 기고에서는 IEEE LAN/MAN Standard Committee내에서 현재 진행중인 무선 표준 화 동향에 대해서 살펴본다. 이미 Wi-Fi라는 이름으로 상용화되어 로컬 환경에서 벗어나 고속의 서비스 및 로밍 서비스를 지원하기 위해서 진행 중인 IEEE 802.11과 각종 가전 제품들의 근거리 통신을 위한 IEEE 802.15, 그리고 차세대 무선 인터넷의 접속 기술로 각광 받고 있는 IEEE 802.16과 단말의 고속 이동을 지원하기 위한 IEEE 802,20, 그리고 마지막으로 이종 망간의 유연한 핸드오버를 지원하기 위한 IEEE 802.21의 표준 진행 결과 및 향후 전망에 대해서 주로 다룬다. (중략)

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.2
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• pp.39-44
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• 2015

Restricted Access Window (RAW) has been designed to improve power saving efficiency by reducing collisions of contending stations in the IEEE 802.11ah Wireless Local Area Networks (WLANs). We conduct simulations in order to observe the stations' operations influencing the lengths of the Restricted Access Window (RAW). From the observation, we consider how to adjust the stations' operations for proper RAW managements.

• Journal of IKEEE
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• v.20 no.3
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• pp.322-325
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• 2016

This paper proposed Enhanced Segmentized Clear Channel Assesment(ESCCA) for the IEEE 802.15.4 networks. This method divides original CCA into two groups to check precise channel status and perform additional CCA to increase throughput performance. Through the proposed method, the device can access the channel more often, so the transmission efficiency of the IEEE 802.15.4 network improves. To confirm the feasibility and usability of the proposed method, computer simulation has been performed. In the simulation, a star topology with one coordinator and a lot of devices is considered and the traffic flows are all one way, with the communication directed to the coordinator. Simulation results_ show the proposed method is improving maximum 10 kbps of throughput and decreasing maximum 15 of the average number of total CCA than IEEE 802.15.4 CCA method.

• Information and Communications Magazine
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• v.30 no.6
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• pp.20-25
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• 2013

본고에서는 1GHz 이하 주파수에서 동작하는 Wireless LAN(WLAN) 표준으로, IEEE 802.11ah PHY/MAC 표준 규격에 대해서 알아 본다. IEEE 802.11ah 표준은, Smart Grid, M2M, IoT 와 같이 실내, 실외에서 많은 수의 단말들을 최소한의 전력소모로 데이터 통신을 하기 위한 목적으로 개발되었다. WLAN의 서비스 범위가 1Km 이상으로 늘어나게 되면, 그 동안 WLAN 에서 심각하게 다루지 않았던 Hidden Node 문제가 단말의 전력 소모, throughput performance 을 결정하는 중요한 요소로 등장하게 된다. 특별히 IEEE 802.11ah 에서는, 많은 수의 단말들간에 Hidden Node 을 고려한 Restricted Access Window 라는 새로운 channel access 기법이 제안되었고, 이에 본 고에서는 IEEE 802.11ah 에 새롭게 지원되는 MAC 기능들에 대해 중점적으로 살펴 보도록 한다.

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.4
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• pp.93-101
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• 2019

This paper presents a software design and implementation of software-defined radio based IEEE 802.11ac encoder using Texas Instruments TMS320C6670 digital signal processor (DSP) platform. In this paper, the implemented encoder has the capability of generating all the signals consisting of preamble field and data field under different modulation & coding scheme in the IEEE 802.11ac standard. Moreover, the flexibility in choosing different rate, bandwidth, or mode can also be achieved by software reconfiguration using the DSP. As a result, by utilizing the computing power provided by multi-cores as well as the FFT coprocessors in the DSP, the required maximum throughput 78Mbps can be fully reached within 4 ㎲ for each OFDM symbol in the case of 20MHz bandwidth of IEEE 802.11ac.

• Journal of Advanced Navigation Technology
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• v.20 no.3
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• pp.232-237
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• 2016

As a possible standardization of wireless local area network (WLAN), IEEE 802.11 LRLP is under discussion in order to support long range and low power (LRLP) communication for internet of things (IoT) including drones and many other IoT devices. In this paper, an efficient adaptive resource unit allocation scheme for uplink multiuser transmission in IEEE 802.11 LRLP networks is proposed. In the proposed scheme, which adopts OFDMA random access based transmission scheme of IEEE 802.11ax, in order to enhance the efficiency of the slotted OFDMA random access, access point (AP) traces the history of the sizes of successfully transmitted uplink data, and adjusts the sizes of resource units for the next uplink multiuser transmission adaptively. Our simulation results corroborate that the proposed scheme significantly improves the system throughput.

• Journal of Advanced Navigation Technology
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• v.23 no.6
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• pp.589-596
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• 2019

With the proliferation of intelligent transportation system (ITS) with dedicated short-range communication (DSRC) deployment, there are various applications requiring different throughput and reliability performance. To meet the enhanced throughput requirements in newly generated applications, IEEE 802.11bd is proposed to standardize for support of enhanced throughput and latency, preserving the fairness with previously deployed WLAN V2X devices. One of the main features of IEEE 802.11 bd is 20 MHz transmission to support the high data rate. In this paper, the primary channel selection method is proposed to guarantee the fairness with frame transmissions with 10 MHz bandwith including communications in WLAN V2X devices deployed with IEEE 802.11p. Simulation shows that the proposed channel access method for 20 MHz transmission with primary selection preserves the fairness without the change of channel access method in wide-band transmission.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.316-318
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• 2003

본 논문에서는 무선랜 프로토콜 IEEE802.11g에서 사용되는 변조방식인 OFDM (Orthogonal frequency division multiplexing) 방식을 TMX320C6416을 사용하여 구현하였다. 통신 시스템의 발달에 따라 고속으로 데이터를 전송하는 방식이 요구되었고, 유선망 없이 장소에 구애 받지 야고 데이터를 송수신할 수 있는 무선랜 시스템의 필요성이 증가하고 있다. 이러한 필요성에 따라 2002년 6월 현재 발표된 IEEE 802.11g 규격 Draft 2.8은 2.4GHz 주파수 대역에서 기존 IEEE 802.11b규격과 호환성은 유지하며 전송속도를 최소 20Mbps 이상을 목표로 한다. IEEE802.119에 정의된 규정에 따라 OFDM방식의 기저대역 알고리즘을 TMX320C6416 을 사용하여 각 블록별로 C언어로 구현하였고, TMX320C6416에 대한 리니어 어셈블리 언어로 구현하는 최적화 작업을 통해 연산속도를 향상시키는 것을 목적으로 하며, 구현한 알고리즘의 비트 오류 확률을 매트랩 시뮬레이션 결과와 비교해 보도록 한다.

• 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.