• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.383-385
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• 2007

IEEE 802.15.4 is a standard designed for low rate wireless personal area networks(LR-WPANs). This paper presents the analytical model for to derive the saturation throughput of collision avoidance protocol of IEEE 802.15.4 in ad hoc network. we assume that nodes placed according to a two-dimensional Poisson distribution.

• 한국정보통신학회논문지
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• 제18권2호
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• pp.303-310
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• 2014

n개의 무선 노드가 랜덤하게 위치한 초 광 대역 애드 혹 네트워크에서의 개선된 용량 스케일링 법칙을 보인다. 먼저, 수정된 계층적 협력 기술이 사용되는 경우를 고려한다. 단위 면적의 밀집 네트워크에서, 유도한 용량 스케일링은 전력 제한된 성격 때문에 특정 동작 영역에서 경로손실 지수 ${\alpha}$에 의존함을 보인다. 또한, 계층적 협력 기술은 2 < ${\alpha}$ < 3에서 우월하지만 ${\alpha}{\geq}3$에 대해서는 다중 홉 라우팅을 사용하는 것이 더 높은 용량을 취득함이 밝혀진다. 둘째로, m개의 기지국이 초 광 대역 네트워크에 균일하게 분포한 경우, 인프라 구조의 영향 및 이득을 분석한다. 이때, 모든 동작 영역에 대해 전력 제한된 성격 때문에, 유도한 용량 스케일링은 ${\alpha}$에 의존한다. 게다가, 변수 m이 특정 레벨 이상일 때 전체 용량이 m과 함께 선형적으로 스케일함을 보인다. 그러므로 계층적 협력 또는 인프라 구조의 사용은 특정 조건에서 초 광 대역 네트워크의 용량을 개선하는데 도움이 된다.

• Journal of Communications and Networks
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• 제16권2호
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• pp.227-237
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• 2014

Throughput scaling laws for two coexisting ad hoc networks with m primary users (PUs) and n secondary users (SUs) randomly distributed in an unit area have been widely studied. Early work showed that the secondary network performs as well as stand-alone networks, namely, the per-node throughput of the secondary networks is ${\Theta}(1/\sqrt{n{\log}n})$. In this paper, we show that by exploiting directional spectrum opportunities in secondary network, the throughput of secondary network can be improved. If the beamwidth of secondary transmitter (TX)'s main lobe is ${\delta}=o(1/{\log}n)$, SUs can achieve a per-node throughput of ${\Theta}(1/\sqrt{n{\log}n})$ for directional transmission and omni reception (DTOR), which is ${\Theta}({\log}n)$ times higher than the throughput with-out directional transmission. On the contrary, if ${\delta}={\omega}(1/{\log}n)$, the throughput gain of SUs is $2{\pi}/{\delta}$ for DTOR compared with the throughput without directional antennas. Similarly, we have derived the throughput for other cases of directional transmission. The connectivity is another critical metric to evaluate the performance of random ad hoc networks. The relation between the number of SUs n and the number of PUs m is assumed to be $n=m^{\beta}$. We show that with the HDP-VDP routing scheme, which is widely employed in the analysis of throughput scaling laws of ad hoc networks, the connectivity of a single SU can be guaranteed when ${\beta}$ > 1, and the connectivity of a single secondary path can be guaranteed when ${\beta}$ > 2. While circumventing routing can improve the connectivity of cognitive radio ad hoc network, we verify that the connectivity of a single SU as well as a single secondary path can be guaranteed when ${\beta}$ > 1. Thus, to achieve the connectivity of secondary networks, the density of SUs should be (asymptotically) bigger than that of PUs.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.467-469
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• 2006

In wireless network environments, as users' demands on high-speed data communications due to increase of multi-media services, the necessity of new high-speed WLAN technologies has appeared. Nowaday, IEEE is standardizing a new WLAN protocol caned as IEEE 802.11n. To effectively use wireless resources, IEEE 802.11n introduces MAC aggregation function which is similar to that in IEEE 802.11e. In case of transmitting several frames without MAC aggregation, the frames include individual frame header and trailer, and their corresponding acknowledgement frames can appear on wireless link. However, if they are aggregated into single MAC frame, we can reduce the number of used bits due to frame headers/trailers and also remove redundant acknowledgement frames. In this paper, we explain two different MAC frame aggregation methods for IEEE 802.11e and IEEE 802.11n and evaluate their throughput by simulations.

• Journal of Communications and Networks
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• 제13권5호
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• pp.463-471
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• 2011

Cooperative communications using relays in wireless networks have similar effects of multiple-input and multiple-output without the need of multiple antennas at each node. To implement cooperation into a system, efficient protocols are desired. In IEEE 802.11 families such as a/b/g, mobile stations can automatically adjust transmission rates according to channel conditions. However throughput performance degradation is observed by low-rate stations in multi-rate circumstances resulting in so-called performance anomaly. In this paper, we propose active relay-based cooperative medium access control (AR-CMAC) protocol, in which active relays desiring to transmit their own data for cooperation participate in relaying, and it is designed to increase throughput as a solution to performance anomaly. We have analyzed the performance of the simplified AR-CMAC using an embedded Markov chain model to demonstrate the gain of AR-CMAC and to verify it with our simulations. Simulations in an infrastructure network with an IEEE 802.11b/g access point show noticeable improvement than the legacy schemes.

• 전자공학회논문지
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• 제50권2호
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• pp.104-113
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• 2013

60GHz 멀티-기가비트 WPAN 시스템을 위한 고속 QC-LDPC 복호기의 구조를 제안한다. 제안한 QC-LDPC 복호기 설계를 위하여 4 블록-병렬 계층 복호 기술과 fixed wire network 기술이 적용 되었다. 2단 파이프라이닝과 4 블록-병렬 계층 복호기술은 동작 주파수와 데이터 처리량을 개선시키는데에 큰 효과가 있다. 또한 본 제안한 복호기 구조에서 스위치 네트워크를 구현하여 위하여 fixed wire network로 간단하게 구현될 수 있으면 하드웨어 복잡도를 크게 감소시킬 수 있다. 제안한 672-비트, rate-1/2인 QC-LDPC 복호기 구조는 90-nm CMOS 표준 셀을 이용해 설계 및 합성하였다. 성능 분석 결과 제안한 QC-LDPC 복호기 구조는 794K 게이트를 가지며 클락 속도 290MHz 에서 작동한다. 12-iteration일 때 데이터 처리율은 3.9 Gbps 이며 60GHz WPAN 시스템에 적용되어 사용 될 수 있다.

• Mass Spectrometry Letters
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• 제4권3호
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• pp.47-50
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• 2013

An ultra-fast generic LC-MS/MS method was developed for high-throughput quantification of discovery pharmacokinetic (PK) samples and its reliability was verified. The method involves a simple protein precipitation for sample preparation and the analysis by ultra-fast generic LC-MS/MS with the ballistic gradient program and selected reaction monitoring (SRM) mode. Approximately 290 new chemical entities (NCEs) (over 10,000 samples) from 5 therapeutic programs were analyzed. The calibration curves showed good linearity in the concentration range of 1, 2 or 5 to 2000 ng/mL. No significant ion suppression was observed in the elution region of all the NCEs. When approximately 300 plasma samples were continuously analyzed, the peak area of internal standard was constant and reproducible. In the repeated analysis of samples, the plasma concentrations and the area under the curve (AUC) were consistent with the results from the first analysis. These results showed that the present ultra-fast generic LC-MS/MS method is reliable in terms of selectivity, sensitivity, and reproducibility and could be useful for high-throughput quantification and other bioanalysis in drug discovery.

• ETRI Journal
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• 제31권5호
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• pp.510-517
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• 2009

A high throughput parallel decoding method is developed for context-based adaptive variable length codes. In this paper, several new design ideas are devised and implemented for scalable parallel processing, a reduction in area, and a reduction in power requirements. First, simplified logical operations instead of memory lookups are used for parallel processing. Second, the codes are grouped based on their lengths for efficient logical operation. Third, up to M bits of the input stream can be analyzed simultaneously. For comparison, we designed a logical-operation-based parallel decoder for M=8 and a conventional parallel decoder. High-speed parallel decoding becomes possible with our method. In addition, for similar decoding rates (1.57 codes/cycle for M=8), our new approach uses 46% less chip area than the conventional method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.297-300
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• 2000

This paper proposes a high-speed and area-efficient FFT algorithm and performs a hardware implementation. This algorithm, named by “Radix-4/2”, uses the feature of existing radix-2$^3$algorithm, It reduces the number of non-trivial multipliers in SFG to the ratio of 3 to 2 campared with radix-2 or radix-4 algorithm and radix-4/2 has also twice throughput as radix-2$^3$algorithm's. It is proved that FFT processor using the proposed algorithm and 64-point MDC pipeline architecture has twice throughput as radix-2$^3$algorithm's, and reduces areas by 25 percentages in contrast to radix-4 algorithm's.

• 전자공학회논문지A
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• 제31A권4호
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• pp.21-29
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• 1994

Three protocols based on the slotted Aloha technique are proposed for very high-speed optical fiber local area networks using wavelength division multiplexing (WDM) passive star topology and the throughputs and delays are derived. For getting a high probability in successful transmission of control packets determining the transmission of a data packet, we adopt control mini slot groups in these protocols. The retransmission probability is also considered in analysis. Both throughput and delay of three protocols are compared and analyzed by varying the number of control solt groups, the retransmission probability the length of a data packet and the number of channels. The numerical analysis shows that the proposed protocols adopted the control slot groups give the increase of throughput and the decrease of delay.