• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1990.10a
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• pp.34-39
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• 1990

• Current Optics and Photonics
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• v.4 no.3
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• pp.186-192
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• 2020

This paper describes a real-time monitoring system in Ethernet passive optical networks (EPON) that uses burst-mode fiber Bragg grating (FBG) optical sensors. The FBG interrogation unit in the optical line terminal (OLT) transmits the monitoring wavelength to optical network units (ONUs). The FBG sensor unit in each ONU returns a burst-mode monitoring signal to the OLT. As the system applies time division multiple access (TDMA), a uniform Bragg wavelength can be used to monitor the EPON system. The FBG interrogation unit analyzes the received burst-mode monitoring signals and outputs fault information on the ONU branches in EPON. The simulation results show the effectiveness of the proposed monitoring system based on TDMA. In addition, we compared the proposed TDMA-based monitoring system with a WDMA-based monitoring system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2839-2846
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• 2014

New VHF band for use in VDE is determined by WRC-12 due to the overload of AIS VDL, and the system characteristics of the VDE is recommended as ITU-R M. 1842-1. CS-TDMA, a multiple access method of AIS class B, is recommended as that of the VDE. It is inefficient for CS-TDMA just applying the report interval used in AIS class B to transmit high speed data with higher payload in the aspect of efficiency. In this paper, a simulation is executed in order to determine adequate report interval according to the number of active ships that affects directly network traffic. To this end, the performance of CS-TDMA, which includes the number of received packets, reception success rate, channel utilization, and collision rate, is investigated via a simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.2009-2014
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• 2012

The general bus system architecture consists of masters, slaves, arbiter, decoder and so on in shared bus. As several masters can't use a bus concurrently, arbiter plays an role in bus arbitration. In compliance with the selection of arbitration method, The efficiency of bus usage can be determined. Fixed Priority, Round-Robin, TDMA, Lottery arbitration are studied in conventional arbitration method. In this paper, we draw the performance comparison of TDMA and Lottery bus arbitration policy developed recently due to farious conditions and propose the methods of performance improvement.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.5
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• pp.107-114
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• 2004

In this paper, we present the architecture design of CDMA/TDMA modem chipset for wireless telemetry system. The wireless telemetry system a measuring data collecting system from many RTs(Remote Terminal) installed at the specific area using wireless communication technology. It consists of CU single CU (Central Unit) for collecting data and a large amount of RTs for transmitting the measuring data. We propose the hardware architecture of the modem for RT and CU. We also design those modem using Verilog HDL and synthesis them using Synopsys$^{TM}$ CAD tool. The modem of RT is implemented with 27K gates and that of CU is implemented around 220k gates using 0.6${\mu}{\textrm}{m}$ CMOS standard cell. The proposed system is implemented and tested using Altera$^{TM}$ FPGA.PGA.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.3
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• pp.39-46
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• 1998

In the FDMA and TDMA Cellular Systems, call blocking rise when frewquence slots andtime slots are used to ther users. Otherwise, in the CDMA cellular systems, call locking arises when interference level is above 10dB according to call of other users. System capacity is defined to be Erlang capacity that is the number of users when CDMA blocking probability is 1% or 2%. Users number corresponded channel number of AMPS and TDMA cellular systems. In this paper, we proposed new reuse-fraction using square of interference poser and obtained Erlang capacity for reverse link of CDMA cellular system with bit rate $R_{b}$, 9.6kbps and 14.4kbps. As a results, Erlange capacity of CDMA system have more 20.7 and 5.5 times than AMPS and TDMA system and have more form 1 to 4 Erlang thatn Viterbi and Padovani obtaned.d.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1129-1137
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• 2012

The wireless link of tactical datalink system provides a communication network to share digitalized tactical data in real-time. Also MAC(Multiple Access Control) of this system is subject to TDMA or CSMA according to a operated circumstance of target nodes to exchange the data reliably. In this paper, we verify the operability when we use CSMA scheme based on MIL-STD-188-220 in tactical datalink system which is basically designed with TDMA, and provide a mathematical analysis scheme to verify the operability and performance. Finally, by implementing CSMA scheme to a tactical datalink equipment we obtain practical results which can be compared with theoretical results.

• Journal of Satellite, Information and Communications
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• v.3 no.1
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• pp.8-14
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• 2008

In this paper, we analyze throughput performance of MF-TDMA scheme and QS MC-DS/CDMA(quasi-synchronous MC-DS/CDMA) scheme based on scrambling on WH sequence and PPGC sequence in early frequency offset caused by high speed transfer terminal. QS MC-DS/CDMA scheme with scrambled WH sequence shows 5.7% higher throughput than MF-TDMA scheme and 8% higher throughput than QS MC-DS/CDMA with PPGC sequence in high speed transfer terminal environment such as maximum 1000Km/h speed with high frequency of Ka-band. Finally, we show that QS MC-DS/CDMA scheme with scrambled WH sequence is more efficient than traditional MF-TDMA scheme at the aspect of throughput in DVB-RCS system with Ka frequency band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.5
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• pp.260-270
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• 2014

In this paper, we first analyze the delay performance of Dynamic Space-time Subframe (DSTS)-based frame structure which has been proposed to support the real-time service as well as non real-time service, using Ad hoc Self-Organizing Time Division Multiple Access (ASO-TDMA) MAC protocol, especially when transmitting a MAC SDU with two or more MAC PDUs, in a multi-hop ad-hoc maritime communication network. We propose two key transmission schemes: contiguous DSTS reservation which guarantees the end-to-end delay for the multiple PDUs, and adaptive transmission probability control schemes to maximize the system throughput. Our simulation results show that the proposed schemes outperform the system throughput of the existing transmission schemes, while supporting the real-time requirement.

• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.660-664
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• 2010

This paper proposes a backoff control scheme for guaranteeing fair packet transmissions in TDMA wireless networks. In order to maximize the system performance, the number of packets transmitted in a frame should be kept at a proper level. In the proposed scheme, the base station calculates the packet transmission probability according to the offered loads and then broadcasts to all the mobile stations. Mobile stations attempt to transmit a packet with the received probability. Simulation results show that the proposed scheme can offer better system throughput and delay performance than the conventional one regardless of the offered loads.