• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.603-606
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• 2019

본 논문에서는 무선전력 센서 네트워크에서 다수의 센서 노드가 하베스팅한 에너지를 이용하여 데이터를 기지국으로 전송하고자 할 때, slotted ALOHA 기반의 랜덤 접속 프로토콜을 제안하고 채널 처리율을 최대화하는 최적의 랜덤 슬롯의 개수를 도출한다. 수학적 분석을 통하여 처리율이 랜덤 슬롯 개수에 따라 concavity를 가짐을 밝히고 최적의 슬롯 개수를 구한다. 시뮬레이션을 통하여 고려하는 무선전력 센서 네트워크에서 제안하는 slotted ALOHA 기반의 랜덤 접속 프로토콜이 최적 랜덤 슬롯 개수를 사용할 때 처리율이 최대화됨을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권2호
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• pp.511-527
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• 2024

This paper proposes a block-based self-organizing time-division multiple access (BSO-TDMA) protocol for very high frequency (VHF) data exchange system (VDES) in shipborne ad-hoc networks (SANETs). The BSO-TDMA reduces the collisions caused by the simultaneous transmission of automatic identification system (AIS) messages by uniformly allocating channel resources using a block-wise frame. For this purpose, the BSO-TDMA includes two functional operations: (1) frame configuration and (2) slot allocation. The first operation consists of block division and block selection. A frame is divided into multiple blocks, each consisting of fixed-size subblocks, by using the reporting interval (RI) of the ship. Then, the ship selects one of the subblocks within a block by considering the number of occupied slots for each subblock. The second operation allocates the slots within the selected subblock for transmitting AIS messages. First, one of the unoccupied slots within the selected subblock is allocated for the periodic transmission of position reports. Next, to transmit various types of AIS messages, an unoccupied slot is randomly selected from candidate slots located around the previously allocated slot. Experimental simulations are conducted to evaluate the performance of BSO-TDMA. The results show that BSO-TDMA has better performance than that of the existing SOTDMA.

• 한국통신학회논문지
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• 제34권7B호
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• pp.686-693
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• 2009

본 논문에서는 능동형 RFID 시스템에서 태그 수집 성능을 향상시키기 위해 빈 시간 슬롯을 활용하는 효율적인 태그 슬립 기법을 제안한다. 제안하는 태그 슬립 기법에서 리더는 프레임 슬롯 알로하 기반의 태그 수집 과정 동안 캐리어 신호의 감지를 통해 빈 시간 슬롯의 발생을 검출하고 낭비되는 빈 시간 슬롯을 수집된 태그들에게 슬립 명령어를 전송하는데 활용하여서 결과적으로 태그 수집에 소요되는 시간을 감소시킨다. 본 논문에서는 시뮬레이션 실험을 통해 제안하는 태그 슬립 기법을 적용한 태그 수집의 성능을 일반적인 태그 수집의 성능과 비교하여 평가하였다. 시뮬레이션 결과는 제안하는 태그 슬립 기법을 적용한 태그 수집 방식이 128개와 256개의 고정시간 슬롯을 가지는 프레엄 슬롯 알로하 및 동적 프레엄 슬롯 알로하 충돌방지 프로토콜들이 사용되었을 때, 각각 12.28%, 12.30%, 13.31%의 평균 태그 수집 시간을 감소시킴을 보였다.

• 한국산업정보학회논문지
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• 제18권1호
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• pp.11-17
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• 2013

A design method to achieve multiple band-rejection characteristics in a wideband circular slot antenna is presented. First, a wideband circular slot antenna fed by a coplanar waveguide is designed to operate in the frequency range between 2.3 and 11GHz, which covers WLAN, WiBro, WiMAX, and UWB frequency bands. Next, resonant frequency variations of rejection bands are examined with respect to different slot locations and lengths when slots are inserted on the ground conductor and the circular patch of the antenna. When arc-shaped slots are placed close to the circular transition from a feeding part, multiple notch bands are obtained. In this case, a half of the guided wavelength of the first notch band corresponds to the slot length and other notch bands are integer-multiple of the first band. Single notch band can be obtained when the slot is located off the transition part. Based on this study, a wideband circular slot antenna with five band-rejection frequency bands at 2.45, 3.5, 4.9, 7.35, and 9.8GHz is designed and fabricated. The first arc-shaped slots are located in the ground conductor close to the circular transition from a feeding part to generate notch bands at 2.45, 4.9, 7.35, and 9.8GHz, while the second slot for 3.73 GHz is placed on top side in the circular patch. The proposed design method is validated by good agreement between the simulated and measured results.

• ETRI Journal
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• 제35권1호
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• pp.58-68
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• 2013

Five-phase reservation protocol (FPRP) is a contention-based media access control protocol for wireless ad hoc networks. FPRP uses a five-phase reservation process to establish slot assignments based on time division multiple access. It allows a node to reserve only one slot in an information frame. Once a node has reserved a slot, it will cease contending for other slots. As a result, there may be less contending nodes in the remaining slots, so the time slots in an information frame are not fully used by FPRP. To improve time slot utilization, this paper proposes an improved pseudo-Bayesian algorithm, based on which an improved contention access mechanism for FPRP is proposed, in which nodes are allowed to contend for more than one slot in a reservation frame according to a certain probability/priority. Simulation results indicate that the proposed mechanism performs better than FPRP in time slot utilization and hence the network throughput under various scenarios.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.466-469
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• 2004

In this paper, we improve the matching impedance of antennas by inserting parasitic slots on the ground plane of right-angle triangular slot antennas. The designed antennas characteristics are analyzed by using Finite Different Time Domain (FDTD) method, the specific design frequency is 10 GHz and match impedance is 50 ohms. Simulation results show that the efficient of return loss and radiation patterns are improved and enhance. In this case, the right-angle triangular slot antennas with parasitic slots have matching impedance better than antennas without parasitic slots.

• 전자공학회논문지A
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• 제29A권11호
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• pp.1-13
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• 1992

In this DQDB networks, erasure nodes may be allocated on the bus and release slots which already had been read by destination nodes. An important function of the erasure node must be to eliminate as many requests as erased slots used by downstream nodes. In the networks with priorities, following two additional issues must be solved : (1) accurately to guess for which priority the erased slots is to be used, and (2) to find in a short period a request of that priority to cancel. In this paper, we propose two erasure node algorithms based on elimination of the requests. In these algorithms, the requests are eliminated excessively at low load but optimum elimination can be achieved at full load. Simulation results show that these two algorithms have similar access delay to that of existing algorithms at low load and better performance at high load.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.196-201
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• 2008

This paper is about electromagnetic vibration source in outer rotor type of BLDC motors. Experiments are carried out with three pole-slot combinations which are 6 slots, 12 slots, and 24 slots with 4 poles rotor. According to results, vibration sources separate into electromagnetic and mechanical factors. Using the finite element method (FEM), It is analyed that vibration characteristics of electromagnetic source in each type. This paper shows electromagnetic sensitivity to vibration, and introduces necessary point in lower vibration motors. Also rotor balance is important to prevent uneven distribution of magnetic flux between rotor and stator.

• 한국정보통신학회논문지
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• 제6권2호
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• pp.141-150
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• 2002

본 논문에서는 주파수 도약 시퀀스를 사용하는 직교 멀티캐리어 FH/CDMA 시스템을 구성해 보고 지연된 다른 사용자 신호들에 의한 충돌 발생 가능성을 사용자 접속 캐리어 슬롯 수에 따라 변화시켜 가면서 성능 저하에 큰 영향을 미치지 않는 최적의 사용자 접속 캐리어 슬롯 수를 찾아보았다. 아울러 시스템의 TCM과 Concatenated code 기법을 적용하여 BER 성능 개선 정도를 컴퓨터 시뮬레이션을 통해 평가하였다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.44-48
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• 2000

In this study was modify the PRMA for supporting various types of traffic classes such as CBR, VBR, ABR and UBR. For uplink, we use reservation slots and so the performance will not degrade in case of over load conditions. For downlink broadcasting slots for informing the status of slot reservations are used so the high priority priority terminal can preempt. And we use almost same size buffer as the frame size. So we can dynamically deal with, the traffic changes of VBR terminals. It makes easy for the terminals to reserve supplementary slots. Each terminal is reallocated by the priority of traffic classes and so we can easily select the dropping packets in case of overload conditions. As a result, using our scheme, we can get high channel efficiency and get low packet dropping ratio and delay.