• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.10a
• /
• pp.686-690
• /
• 2003

직접 확산 부호 분할 다원 접속 (Direct Sequence Code Division Multiple Access : DS-CDMA) 시스템과 시분할 다원 접속 (Time Division Multiple Access : TDMA) 시스템을 동일 주파수 대역에서 중첩되어 전송할 때 DS-CDMA 신호에서의 TDMA 신호의 협대역 간섭이 문제된다. 본 논문에서는 DS-CDMA 신호의 협대역 간섭(narrowband interference : NI)를 제거하는 방법으로서 노치필터를 이용해서 협대역 간섭파 제거법을 제안하고, 간섭제거기(CCI canceller)를 이용해서 다중접속간섭을 제거하여 DS-CDMA 신호의 성능을 개선한다. 본 논문은 잡음, 다중접속 간섭 및 협대역 간섭환경에서 DS-CDMA 신호와 TDMA 신호의 주파수 공용 시스템에 적용할 때의 성능을 분석하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.9A
• /
• pp.1273-1281
• /
• 2000

In this paper we studied for multi-user detection system, which hold the merit of CDMA system and can enhance the system capacity. We designed actually realizable quasi-optimal multiuser detection system by use of linear equalizer on the concept that multiuser detection algorithm can be reduced by combining TDMA with CDMA. we call this the hybrid TDMA/CDMA system. And we proposed multiuser detection system, which can use PSAD and MSDD channel estimation method. As a result of performance analysis we acquired equal or much better performance by use of linear multichannel equalizer in the case of not so many user. And on the occasion of many user within cell we can also acquired much better performance in comparison with conventional single user detection system by use of hybrid TDMA/CDMA system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2011.10a
• /
• pp.114-115
• /
• 2011

최근 애드혹 네트워크에서 신뢰성과 확장성을 고려하여 메쉬 라우팅의 지원이 요구되고 있으며 IEEE 802.15.5의 Low-rate WPAN Mesh 와 ZigBee alliance에서 AODV를 기반으로 한 메쉬 라우팅이 대표적이다. IEEE 802.15.5 Low-rate WPAN Mesh의 경우 메쉬 라우팅을 위해 hello command의 주기적인 브로드캐스팅이 필요한데 이는 네트워크를 구성하는 노드의 밀집도가 증가할 경우 그 부하가 기하급수적으로 증가하게 된다. 또한 ZigBee alliance의 AODV 기반 메쉬 라우팅 기법도 RREQ 메시지의 브로드캐스팅에 기반하고 있기 때문에 경로 설정을 위한 제어 트래픽의 부하가 매우 크다는 단점을 갖는다. 본 논문에서는 TDMA 네트워크에서 TDMA MAC의 특성과 토폴로지 기반으로 할당된 주소를 활용한 메쉬 라우팅 알고리즘의 설계를 제안한다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2014.04a
• /
• pp.264-267
• /
• 2014

TDMA(Time Division Multiple Access)는 사용자에게 자신에게 할당된 시간구간에서 모든 대역폭을 이용하여 무선 네트워크에서 통신할 수 있는 다중 접속기술이다. TDMA에서 동기화 방식은 동기화를 이루는 방법이 어렵기 때문에 소규모 네트워크에는 적합하지 않다. 본 논문에서는 DESYNC 알고리즘을 이용하여 소규모 네트워크에 적합한 동기화 방식의 TDMA 기법인 C-DESYNC를 제안하고자 한다. C-DESYNC는 DESYNC의 firing 방식을 이용하고, 주기의 시작 정보를 포함하고 있는 Global Packet을 이용하여 안정화상태까지 걸리는 최대 지연시간을 보장한다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2013.11a
• /
• pp.396-399
• /
• 2013

TDMA(Time-Division Multiple Access)는 한정된 채널을 시간상에서 여러 개의 구간으로 분할하고, 자신에게 할당된 시간 구간에서 정보를 전송하는 기법이다. 본 논문은 TDMA 알고리즘의 한 종류인 DESYNC 알고리즘을 소규모 네트워크에 적용하여 별도의 동기화 작업 없이 간단한 규칙으로 동기화를 유지하는 기법을 소개 한다. 기존의 DESYNC 알고리즘은 모든 노드들이 전송 영역 안에 있어야 하고, 전부 연결되어있어야 한다는 단점이 있다. 이 문제점을 해결하고자 중앙제어장치인 CU(Central Unit)을 네트워크에 배치하여 2-홉 형태의 중앙 집중방식 네트워크가 운영되도록 하였다. 제시하는 알고리즘은 기존의 DESYNC 알고리즘과 마찬가지로 복잡한 동기화 과정 없이 단순한 방식으로 TDMA가 동작할 수 있도록 하면서, 전송 범위는 기존의 DESYNC 알고리즘의 성능에 비해 우수하다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.6 no.10
• /
• pp.2509-2528
• /
• 2012

Time division multiple access (TDMA) is a widely used media access control (MAC) technique that can provide collision-free and reliable communications, save energy and bound the delay of packets. In TDMA, energy saving is usually achieved by switching the nodes' radio off when such nodes are not engaged. However, the frequent switching of the radio's state not only wastes energy, but also increases end-to-end delay. To achieve high energy efficiency and low delay, as well as to further minimize the number of time slots, a multi-objective TDMA scheduling problem for industrial wireless mesh networks is presented. A hybrid algorithm that combines genetic algorithm (GA) and simulated annealing (SA) algorithm is then proposed to solve the TDMA scheduling problem effectively. A number of critical techniques are also adopted to reduce energy consumption and to shorten end-to-end delay further. Simulation results with different kinds of networks demonstrate that the proposed algorithm outperforms traditional scheduling algorithms in terms of addressing the problems of energy consumption and end-to-end delay, thus satisfying the demands of industrial wireless mesh networks.

• Journal of Satellite, Information and Communications
• /
• v.4 no.1
• /
• pp.14-20
• /
• 2009

This paper describes synchronization concept and algorithm of the reverse DS-SS/TDMA control channel to handle satellite terminals which are distributed through the mission area. Military satellite control channel should have ECCM capabilities and handle more than several hundreds satcom terminals simultaneously. DS-SS/TDMA control channel can satisfy these demand but it spend much synchronization time. Proposed algorithm insert the preamble which is divided with several short sub bins prior to control data and use the parallel matched filtering searcher for each sub bin. As a result of the test, proposed algorithm can acquire most of control channel packet successfully within several milliseconds in severe jamming environment.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.4C
• /
• pp.364-370
• /
• 2006

It is required for correct signal detection to accurately maintain the synchronization of frequency and timing in a TDMA system. In this paper, we consider nondecision-aided estimation of frequency offset for the transmission of QPSK signal in a TDMA-based satellite system. The proposed scheme estimates the phases of two parts in the burst and then estimates the frequency offset based on the difference between the two estimated phases. Thus, it can provides performance comparable to that of conventional schemes, while significantly reducing the implementation complexity, The performance of the proposed scheme is analyzed and verified by computer simulation, when applied to a GSM based geostationary earth orbit mobile radio(GMR) system.

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

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.5B
• /
• pp.466-474
• /
• 2003

In this paper, we develope the simulation model for Ethernet passive optical networks (Ethernet-PON) by using OPNET. Ethernet-PON is an emerging access network technology that provides a low-cost method of deploying optical access lines. The simulator uses a Request/Grant TDMA MAC protocol based on IEEE 802.3ah EFM. It also executes registration, ranging and dynamic bandwidth allocation algorithm by exchanging control packets between OLT and ONUs. We have evaluated for success ratio of initial registration process and delay of late registration process. We also have simulated for dynamic TDMA protocol and static TDMA protocol in terms of channel utilization and queueing delay. We expect that this simulator can help to determine various parameters which are considered for designing Ethernet-PON system.