• Title/Summary/Keyword: TDMA

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Polyphase jammer suppression on DS-CDMA forward link using multi-rate techniques (순방향 DS-CDMA시스템에서 Multi-rate 기술을 이용한 협대역 재머 억제 여파기)

  • 김동구;박형일
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.23 no.7
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    • pp.1707-1717
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    • 1998
  • Polyphase filtering techniques is used to suppress the narrowband jammer signal such as USDC TDMA overlaying the band occupied by DS-CDMA system. In the proposed jammer suppression, the received signal is separated into 64 subchannels in two stages by polyphase filtering and the location of the narrowband jammer signal is determined by measuring each subchannel power and the contaminated subchannels are simply blocked. The $E_{b}/N_{0}$ 0/ improvement of the CDMA system from jammer suppession was outstanding. The $E_{b}/N_{0}$ degradation in comparison with a performance of no jammer is around 0.8dB in the worst case. The results are also compared with those of linear prediction jammer suppression. The implementation of the ployphase jammer suppression requires great amount of data processing and computation compared to linear predication filter. Thus it is more appropriate to implement with a ASIC rather than WITH several DSPs for user terminals of forward link.

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A realization of up/down-stream transmission on an optical subscriber network with the PON structure (PON구조의 광가입자망에서 상/하향전송 구현)

  • 김효중;이찬구;강성수;이만섭
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.3
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    • pp.795-806
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    • 1996
  • A structure which transmits and receives 3 subscribers packet data through an optical splitter node in an optical subscriber network of PON wave suggested and realized. All the functions which are necessary to use PON structure such as 155.52Mb/s multiplexer/demultiplexer of down-stream signal, 25.92Mb/s multiplexer/demultiplexer of up-stream signal, frame synchronizer, and phase aligner for aligning phase of the clock and received data have been integrated within 2 ICs using CMOS technonology. TDMAtechnology was suggested for up-stream transmission. In the optical up-stream transmission of the urst signals transmissionquality degradataion by APC and AGC of optical tranceiver was observed. By compensating the degradation, more than 17dB of link budget which is enough to satisfy 11.2dBthat is required in SWAN of PON architecture has been obtained with optical transceiver whose power and sensitivity are -17dBm and -34dBm respectively.

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A Study on Film Boiling Heat Transfer in a Forced Convective Flow System (강제대류계(强制對流系)에 있어서 막비등열전달(膜沸騰熱傳達)에 관한 연구(硏究))

  • Kim, Y.T.;Kwon, S.S.;Jung, D.I.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.1
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    • pp.51-60
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    • 1991
  • The aim of this study is to investigate the heat transfer characteristics in the transient cooling process of a high temperature wall. The slow transient cooling experiment was carried out with a copper block of high thermal capacity. The results of these experiments are as follows. 1. Temperature histories measured by the thermocouple, which is 0.99, 2.00, 2.99mm from the heat transfer surface showed monotonous during the cooling process. These variation are the curves of typical temperature histories in film-boiling, transition-boiling, and nucleate-boiling regions. 2. The temperature histories were measured by thermocouple installed in the copper block. The variations of the surface heat fluxes and surface temperature were computed from the numerical solution method TDMA from the measured temperature histories for radial position one dimensional heat transfer inverse problem. The boiling curves were found by the computed temperature histories. 3. The rewetting point which starts to change from film boiling to nucleate boiling is not connected with the mass velocity and it were found that the temperature of rewetting point indicated about $100^{\circ}C$. 4. The heat flux of rewetting point was about $10^5Kcal/m^2h$, at that time, the heat transfer coeficient indicated about $1000Kcal/m^2h^{\circ}C$ irrelevent to mass velocity. 5. The wall superheat decreases as the pressure increases. But I found that rewetting point appeared under higher condition in the wall temperature.

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Distributed Time Division Piconet Coexistence Using Local Time Offset Exchange (로컬 오프셋을 이용한 분산 시간 분리 피코넷 충돌회피 방법론)

  • Park, Yongsuk
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.6
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    • pp.1447-1453
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    • 2014
  • Wireless Body Area Networks (WBAN), standardized as IEEE 802.15.6, enable digital devices on/around the human body to communicate with one another. WBAN is essentially a person's piconet consisting of a master (mobile) device and several slave devices, which follows his/her mobility pattern, and hence, occasionally collides with another piconet as people meet or pass by. As such, a mechanism to detect collision and avoid interference is needed for intra-piconet communications. In this paper, we focus on this notorious problem of piconet collision and propose Distributed Time Division Piconet Coexistence (DTDPC) using local time offset exchange as a simple, attractive solution. The proposed DTDPC provides different level of services for various applications. Besides our simulation results have shown that the proposed solution outperforms the conventional CSMA protocols.

High Power Amplifier Design and Fabrication for Tactical Data Link (전술데이터링크용 고출력증폭기 설계 및 제작)

  • Kim, Jong-Sung;Bae, Moon-Kwan;Kim, Joo-Yeon
    • Journal of IKEEE
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    • v.21 no.4
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    • pp.338-347
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    • 2017
  • This paper describes the design and fabrication of a high power amplifier which is a component of TDL(Tactical Data Link) aircraft terminal. We applied high-speed frequency hopping technology, cognitive radio technology, and receive filter bank technology to efficiently use limited frequency resources with radar and other communication equipment using the same frequency band. The high-power amplifier is physically composed of a transmitter, a receiver, a mechanical part, and a cable assembly, and is designed to meet temperature characteristics and electrical characteristics such as maximum transmission distance and reception sensitivity. Modeling and simulator were used to satisfy the requirement of high power amplifier. The transmit power and the noise figure were measured at 50.02dBm and 2.682dB, respectively. It was confirmed that all the required specifications were satisfied in the electrical characteristics test and the environmental characteristic test.

2.5 Gbps Hybrid PON link Using RSOA Based WDM-PON and a Reach Extender (RSOA기반 WDM-PON 링크와 Reach Extender를 이용한 2.5 Gbps 하이브리드 PON 링크 기술)

  • Kim, Kwang-Ok;Lee, Jie-Hyun;Lee, Sang-Soo;Jang, Youn-Seon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.6B
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    • pp.583-591
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    • 2011
  • We presents the architecture of the 2.5 Gbps hybrid PON link which can increase of the transmission distance and link capability, and split ratio by using a colorless DWDM-PON and O/E/O based reach extender into an existing G-PON link. A RSOA based DWDM-PON to apply the feeder fiber can provide a link capacity of 32 larger that of a legacy G-PON. The reach extender converts the wavelength of DWDM-PON to G-PON through GTC frame regeneration at the remote node, and can provide a burst reset signal in order to extract upstream burst signal, simultaneously. The proposed hybrid PON enable a legacy G-PON to operate over the maximum 60 km distance with a 128-way split per WDM wavelength.

An Energy and Delay Efficient Hybrid MAC Protocol for Multi-Hop Wireless Sensor Networks (멀티 홉 무선센서네트워크에서 에너지와 지연에 효율적인 하이브리드 MAC 프로토콜)

  • Jeon, Jun-Heon;Kim, Seong-Cheol
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.2
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    • pp.471-476
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    • 2015
  • In this paper, we propose an energy efficient hybrid MAC protocol for multi-hop wireless sensor networks. The proposed MAC protocol used a hybrid mechanism, in which contention-based MAC protocol and contention free MAC protocol are combined. The sensor nodes located far from the sink node usually send few data packet since they try to send measured data by themselves. So contention-based MAC protocol is useful among them. But other nodes located near sink node usually have lots of data packets since they plays as a relay node. Contention-based MAC protocol among them is not suitable. Using contention-based MAC protocol in heavy data traffic environment, packet collisions and transmission delay may increase. In this paper, slot assignment between sender nodes by sink node is used. The proposed mechanism is efficient in energy and latency. Results showed that our MAC protocol outperformed other protocol in terms of data packet delivery delay and energy consumption.

AtoN AIS Standardization Research for Centralized Management of the AtoN(Aids to Navigation) (항로표지 집약관리를 위한 AtoN AIS의 표준화에 관한 연구)

  • Lim, Jong-Gun;Song, Gil-Boak;Park, Jeong-Nam;Cho, Tae-Gyun
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2009.06a
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    • pp.425-431
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    • 2009
  • Recently, new technology has been introducing according to the efforts for maritime safety, traffic and environmental protection that uses electronic method to make use of maritime information effectively. To be associated with the tendance, international society which centered to IALA Introduces advanced technology of AtoN with Automatic Identification System(AIS) that it is crucial method to collect and transmit maritime data. This article is to thoroughly analyse and investigate the international and national regulation of related AtoN AIS, and propose to be included and applied into national radio-communication equipment regulation.

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Case Study for Ship Ad-hoc Networks under a Maritime Channel Model in Coastline Areas

  • Su, Xin;Yu, HaiFeng;Chang, KyungHi;Kim, Seung-Geun;Lim, Yong-Kon
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.10
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    • pp.4002-4014
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    • 2015
  • ITU-R M.1842-1, as a well-known specification dedicated to maritime mobile applications, has standardized wireless transmission protocols according to the particular characteristics of a maritime communications scenario. A time division multiple access (TDMA) frame structure, along with modulation schemes to achieve a high data rate, has been described clearly in ITU-R M.1842-1. However, several specification items are still under "to be decided" status, which brings ambiguity to research works. In addition, the current version of ITU-R M.1842-1 is focused mainly on maritime transmissions in open-sea areas, where the cyclic prefix (CP) is set to zero and only 16-QAM is used in the multi-carrier (MC) system. System performance might be dramatically degraded in coastline areas due to the inter-symbol interference (ISI) caused by selective fading. This is because there is a higher probability that the signal will be reflected by obstacles in coastline areas. In this paper, we introduce the transmission resource block (TRB) dedicated to ITU-R M.1842-1 for a ship ad-hoc network (SANET), where the pilot pattern of TRB is based on the terrestrial trunked radio (TETRA). After that, we evaluated SANET performance under the maritime channel model in a coastline area. In order to avoid noise amplification and to overcome the ISI caused by selective fading, several strategies are suggested and compared in the channel estimation and equalization procedures, where the link-level simulation results finally validate our proposals.

A Study on clustering method for Banlancing Energy Consumption in Hierarchical Sensor Network (계층적 센서 네트워크에서 균등한 에너지 소비를 위한 클러스터링 기법에 관한 연구)

  • Kim, Yo-Sup;Hong, Yeong-Pyo;Cho, Young-Il;Kim, Jin-Su;Eun, Jong-Won;Lee, Jong-Yong;Lee, Sang-Hun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.9
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    • pp.3472-3480
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    • 2010
  • The Clustering technology of Energy efficiency wireless sensor network gets the energy efficiency by reducing the number of communication between sensor nodes and sink node. In this paper, First analyzed on the clustering technique of the distributed clustering protocol routing scheme LEACH (Low Energy Adaptive Clustering Hierarchy) and HEED (Hybrid, Energy-Efficient Distributed Clustering Approach), and based on this, new energy-efficient clustering technique is proposed for the cause the maximum delay of dead nodes and to increase the lifetime of the network. In the proposed method, the cluster head is elect the optimal efficiency node based on the residual energy information of each member node and located information between sink node and cluster node, and elected a node in the cluster head since the data transfer process from the data been sent to the sink node to form a network by sending the energy consumption of individual nodes evenly to increase the network's entire life is the purpose of this study. To verify the performance of the proposed method through simulation and compared with existing clustering techniques. As a result, compared to the existing method of the network life cycle is approximately 5-10% improvement could be confirmed.