WPAN 피코넷 채널 시간 배정에 대한 연구

조무호(Mooho Cho),문준호(Junho Moon) 한국조명·전기설비학회 2005 한국조명·전기설비학회 학술대회논문집 Vol.2005 No.5월

WPAN 시스템 개발의 중요한 목표는 다양한 대역폭의 멀티미디어 서비스를 효율적으로 언제, 어디서나, 누구와도 자연스럽고 현실감 있게 정보를 교환할 수 있도록 제공하는 것이다. 멀티미디어 서비스 품질을 보장하기 위해서는 Ad hoc 네트워크에서 한정된 자원과 물리적인 한계에 의해서 가장 취약한 부분인 무선접속 구간에서의 트래픽 특성에 따른 채널할당이 가장 중요시 고려되어야 한다. 본 논문에서는 WPAN 응용을 지원하기 위한 대역폭 요구사항에 대해 알아보고, 응용 서비스별 트래픽 종류에 따라 WPAN MAC 계층에서의 채널 시간 할당 방안에 대해 살펴본다.

무선 센서 네트워크에서 클러스터 기반 라우팅 프로토콜 연구

조무호(Mooho Cho),문준호(Junho Moon) 한국조명·전기설비학회 2005 한국조명·전기설비학회 학술대회논문집 Vol.2005 No.11월

클러스터 기반의 계층적 트리 구조는 대형화가 용이하면서 라우팅 프로토콜이 단순하다는 점에서 장점을 가진다. 본 논문에서는 무선 센스 네트워크에서 클러스터 트리 네트워크 관리를 효과적으로 지원할 수 있는 방안과 라우팅 프로토콜의 데이터 모음과 지연에 대해 분석한다. 수치 해석의 결과에서 보면 중간 노드에서의 데이터 모음을 통한 통신 메시지 수를 줄임으로 센스 노드의 에너지를 크게 절약할 수 있지만, 이에 따른 메시지 전달 지연이 커짐을 알 수 있었다.

차일드 피코넷의 데이터 처리율에 대한 연구

조무호 慶州大學校 2005 論文集 Vol.18 No.2

A piconet is a wireless ad hoc data communications system which allows a number of independent data devices to communicate with each other. A piconet is distinguished from other types of data networks in that communications are normally confined to a small area around person or object whether stationary or in motion that typically covers at least 10 m in all directions. A child piconet is one that is formed under an established piconet. The child piconet functionality is useful for either extending the area of coverage of the piconet or shifting some computational or memory requirements to another PNC capable device. Child piconet is also referred to as dependent piconet since they rely on the parent PNC to allocate channel time for the operation of the dependent piconet. It is possible for the parent piconet to have more than one child piconet. In addition, it is also possible for a child PNC to allow a child piconet as a part of its own piconet. The data throughput of piconet can be affected by these hierarchical formation. In this paper we investigate the data throughput of child piconet by numerical analysis. Results show that child piconet can extend the service coverage as expected. And the child piconet data throughput is increased according to the local traffic. This is due to the closeness of peer to peer communication in child piconet.

가입자 이동성 모델을 이용한 소프트 핸드오프 빈도 예측

조무호 경주대학교 2002 論文集 Vol.15 No.-

In DS-CDMA (Direct Sequence-Code Division Multiple Access) mobile systems, universal frequency reuse applies not only to all mobile users in the same cell, but also to those in all other cells. This feature makes it possible to use the soft handoff scheme. Soft handoff provides various advantages such as an increase of reverse link capacity and a decrease of outage probability. Because it provides sigmficant diversity gains under lognormal shadowing vanahons for both forward and reverse links. The previous traffic models of hard handoff are not applicable to the system with soft handoff due to switching radio channels in that region. The handoff rate can be calculated by the mobility of mobiles, which is a function of the size and shape of a cell, and the speed and density of the mobiles. In this paper, we propose an analytical traffic model to study the soft handoff rate. We assume that the system uses multi-way handoff scheme, which connects all the cells to a mobile during soft handoff. We performed a computer simulation to confirm the accuracy of the proposed soft handoff model. The simulation results show good agreement with the analytical model.

LR_WPAN에서 실시한 데이터 전송 방안 연구

조무호 경주대학교 정보전자기술연구소 2008 情報電子技術論叢 Vol.7 No.-

IEEE 802.15.4 systems are basically designed both for sparsely generating events in order to keep a low duty-cycle and dedicated bandwidth to guarantee message latency. In order to achieve better energy-efficiency and lower data rate, IEEE 802.15.4 can operate in a so called beacon-enabled mode. As the energy saving in the beacon-enabled mode depends on the periodic sleep managed by beacons, it is important to control the ratio of the active period to the inactive period called the duty-cycle. The small duty-cycle causes a packet accumulation and drop in the buffer. Also, the cumulated packets increase collision probability. On the other hands, a long duty-cycle enables end devices to transmit packets while reducing the packet drop and end-to-end delay. For the special case in LR-WPAN, a streaming data like voice transmission is required. At the 2.4GHz band, only one way 32Kbps voice data can be transferred with the retransmission allowed. But in IEEE 802.15.4a, the user data rate is supported up to 850Kbps, the voice streaming data can be transferred more easily. In this research, we study the beacon-enabled mode in IEEE 802.15.4 LR-WPAN standard. We study the beacon-enabled mode in the standard, the limitation of voice transmission over LR-WPAN standard and patent trends for voice transmission.

PCB상의 전류분포에 대한 유한 영상평면의 EMI 차폐효과 해석

조무호,김진석 경주대학교 2003 論文集 Vol.16 No.-

This paper deals with the influence of image planes on the radiation from a printed circuit board (PCB). The shielding performance of image planes of finite width and length is analyzed for three types of source current distributions in PCB by the method of moments based on the triangular surface patch model. It was observed that the electric field radiated from the current source can be considerably reduced with a small sized image plane. In addition, the method of dividing integration intervals into nonuniform cells whose widths reflect the variation of the current distribution is improved, showing that the distribution curve can be more smoothed than the previous one.

이동망 세분화에 대한 연구

조무호 경주대학교 정보전자기술연구소 2002 情報電子技術論叢 Vol.1 No.-

The industry has some urgent issues to resolve in the interconnection between fixed and mobile network, such as introduction of costed based interconnection pricing system. Because of the interconnection way, the profits resulting from the interconnection charges and services can be changed. In the interconnection of all from mobile subscriber to land subscriber (m0bil-to-land), mobile operators route the call with their own network maximum and handover the call to land network near the termination subscriber. They apply the far end havdover method. On the other hand, in the interconnection of call from land subscriber to mobile subscriber (land-to-mobile), land operators handover the call to mobile network. In this case, they use the near end handover method. It is because the land operators do not know about the location of mobile subscribers. Under these unbalanced environment, the costed based interconnection pricing system can make the differences in the profits of interconnection charges between the operators. In this paper, the improvements of land to mobile interconnect system are introduced and the mobile network unbundling is proposed with HLR(Home Location register) access.

WPAN에서 데이터 처리량을 고려한 피코넷 코디네이터 선발 방안 연구

조무호 경주대학교 2004 論文集 Vol.17 No.-

The high rate WPAN was designed to enable wireless connectivity of high-speed, low-power, low-cost, multimedia-capable portable consumer electronic devices. In WPAN, one device is required to assume the role of the piconet coordinator (PNC) of the piconet. The PNC provides the basic timing for the piconet with the beacon and manages the quality of service requirements, power save modes and access control to the piconet. When a device associates with an existing WPAN, the PNC checks the capabilities of the new device to see if it is more capable to be the PNC of the piconet based on the criteria defined in the IEEE Std. 802.15.3. If the new device is more capable and the current security policies allow it, then the PNC has the option of handing over control of the piconet to the device that has just joined. And, if the PNC is shutting down or wants to leave the WPAN, it also uses the handover process to give control to another device in the piconet. However when the PNC is selected, only the device capability information is checked in the standard specification and no detail criteria is described. In this paper, the PNC selection method with considering the data throughput in the WPAN is studied. From the numerical analysis results, the considering with the devices concentration has higher data throughput compared with the uniform distribution. For the efficient performance, the device distribution within the piconet should be considered in the PNC selection.

초음파진단기 합성구경영상법의 진화

배무호,Bae, MooHo 한국음향학회 2022 韓國音響學會誌 Vol.41 No.5

초음파진단기는 실시간으로 손쉽고 안전하게 환자의 병변을 관찰할 수 있는 등의 다양한 장점으로 인해 병원, 의원 등의 의료현장에서 널리 활용되고 있다. 이 초음파진단기 신호처리 블록 중 하나인 빔포머는 초음파진단기 영상의 화질을 결정하는 부분 중 하나이다. 초음파진단기 기술의 발전과 더불어 이 빔포머와 관련된 기술들도 장기간 많은 발전을 이루어 왔는데, 이 기술들 중 하나의 주요 방법인 합성구경영상법(Synthetic Aperture Imaging method, SAI)은 프로브를 통해 수신한 신호가 운반해 온 환자로부터의 정보를 최대로 활용하기 위한 방법으로, 1990년대 경 최초로 초음파진단기에 도입된 이래 획기적 화질 향상에 기여해 왔고, 수십년동안 다양한 형태의 발전을 거쳐왔다. 이 논문에서는 이러한 진화과정을 살펴보고, 이 기술의 미래의 발전 방향을 예상해 본다. Medical ultrasound system has been widely used to visualize the lesion for diagnostics in most medical service site including hospitals and clinics thanks to its advantages such as real time operation, ease of use, safety. Among many signal processing blocks of the system, one of the most important part that governs the image quality is the beamformer, and technologies for this part has been continuously developed in long time. The synthetic aperture imaging method, that is one of the major technologies of beamforming, was introduced to maximize utilizing the information delivered from the patient's body through the probe, and contributed to breakthrough of the image quality since it was introduced in around 1990's, and evolved continuously in decades. This paper reviews and surveys the process of development of this technology and expects future evolution.

PNC Selection Method using Candidate List for High Rate WPAN

HeonJu Jeong,Mooho Cho,SungHee Kim,JungTae Lee 대한전자공학회 2004 ITC-CSCC :International Technical Conference on Ci Vol.2004 No.7