• 한국정보통신학회논문지
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• 제10권1호
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• pp.42-48
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• 2006

본 논문에서는 차세대 복합 시분할 부호분할 다중접속 이동통신 시스템에서 타 셀 사용자 간섭 제거를 위한 결합검출 방안을 제안한다. 결합검출 기술은 차세대 복합 시분할 부호분할 다중접속 이동통신 시스템 TD-CDMA 시스템에서의 가장 큰 특징이라 할 수 있는 기술로서 셀 내의 서로 다른 사용자의 신호 간섭을 제거하여 동시에 사용자 데이터를 복원할 수 있다. 종래의 연구에서는 2단계 결합 검출 방식을 이용하여 목적 셀의 사용자 간섭 뿐 아니라 타 셀 간섭을 제거해 줄 수 있는 방안이 제안되었으나 이 방안에서는 타 셀 간섭 제거를 위한 구체적인 사용자 인식에 대한 방안이 없다. 따라서 주변 타 셀 내의 사용자의 간섭의 크기에 상관없이 모든 사용자에 대하여 결합검출을 수행해야 하며 2단계 결합검출의 복잡도가 매우 높다. 본 논문에서는 타 셀 사용자의 간섭의 크기에 따라서 선택적으로 2단계 결합 검출을 수행하는 방안을 제안한다. 제안된 방식은 모의실험을 통하여 성능을 조사하였으며 종래의 결합검출 방식에 비하여 성능의 열화가 없는 동시에 2 단계 결합검출의 복잡도를 크게 줄일 수 있다.

• 한국통신학회논문지
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• 제30권4A호
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• pp.259-270
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• 2005

본 논문에서는 비대칭적이고 불균질적인 트래픽이 혼재하는 멀티미디어 서비스 환경에서 시분할 듀플렉싱을 사용하는 시분할-코드분할 다중 접속(TD-CDMA) 시스템의 직교 코드와 시간의 2차원적인 자원을 효율적으로 운용하는 방법을 수학적 모델링을 통해서 알아본다. 호-계층에서는 상/하향 트래픽 부하를 2차원 벡터로 나타내어 대기 이론을 기반으로 하여 호손율을 구하며, 최소의 호손율을 보이는 최적의 스윗칭-포인트를 찾는다. 패킷-계층에서는 서킷호와 패킷호로 구분하여 대기 중인 패킷과 서비스 중인 서킷호를 2차원의 상태로 나타내어 패킷 손실율을 구한다. 또한 일정 수준 이상의 서비스 품질을 위해 요구되는 버퍼 크기를 알아본다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.17-20
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• 2001

This paper studies the channel estimation schemes of Time Division Duplex (TDD) Code Division Multiple Access (CDMA) system with a parallel interference cancellation (PIC) scheme in the multi-Path fading channel. Also, the effective interpolation scheme which maintains the merits of WCDMA TDD mode is proposed. By Monte Carlo simulations, it is shown that the proposed interpolation method can be used in order to obtain the proper performance of a multi-stage PIC and in order to reduce the required Eb/No in the second stage at a BER= 10$^{-2}$

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.271-272
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• 2008

TD-SCDMA combines TDMA and CDMA components to provide more efficient use of radio resources, and includes a new feature called HSDPA (high-speed downlink packet access) in the R5 stage. The TD-HSDPA supports high-speed traffic with a shared channel, but its uplink mechanism causes feedback problem for scheduling. Since the base station of TD-SCDMA can estimate the location of mobile terminals precisely, it can also estimate the possible path loss. In this paper, the base station utilizes the estimated path loss for scheduling, which is related with CQI (channel quality indicator) values. The proposed mechanism can provide the TD-HSDPA scheduler with an intial CQI value for efficient transmission.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.261-262
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• 2008

TD-SCDMA is considered as an innovative Chinese 3G technology adopted by the ITU for the IMT-2000 family. TD-SCDMA combines TDMA and CDMA components to provide more efficient use of radio resources. However, the downlink scheduler of TD-SCDMA should transmit data packets with the initial configuration and cannot change the configuration dynamically. Therefore, in this paper, we propose an enhanced channel allocation, by which mobile terminals can share the downlink channelization codes dynamically.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.269-270
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• 2008

TD-SCDMA combines TDMA and CDMA components to provide more efficient use of radio resources, and includes a new feature called HSDPA (high-speed downlink packet access) in the R5 stage. The TD-HSDPA supports high-speed traffic with a shared channel, but the adopted mechanism causes feedback problem for scheduling. In this paper, we propose an improved mechanism that transmits channel quality indicator (CQI) more frequently, so that the TD-HSDPA scheduler can utilize all possible information about the downlink channel status.

• Journal of electromagnetic engineering and science
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• 제6권1호
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• pp.10-17
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• 2006

For the sake of the potential ability of overcoming interference in TD-SCDMA(time division-synchronous code division multiple access) systems, pilot signal is adopted, but the presented TD-SCDMA protocol has not considered the Rake technique for their mobile terminals. This paper developed a RAKE receiver algorithm and an implementation circuit, which make use of the pilot signal in the burst structure of the TD-SCDMA base station to estimate main channel parameter(channel delays) in the downlink of TD-SCDMA wireless network. The algorithm can reduce multipath interference for the mobile units in multiusers' case. Theoretic performance analysis presented in the paper and computer simulations show that there is a range of BER for Rake receiver and confirm that the proposed RAKE receiver algorithm achieved a better performance under multipath fading propagation and multiusers conditions.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.101-104
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• 2001

In TD-CDMA system, multi-user interference degrades the system performance. In this paper, we propose a effective multi-user detection algorithm applicable to TDD mode. We certify a channel estimation capacity by using midamble and performance of the proposed multistage interference canceller in the system complex aspect. In computer simulations, it is verified that proposed algorithm has lower complexity and better performance than conventional multi-user interference cancellation in Rayleigh fading channel.

• Journal of electromagnetic engineering and science
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• 제6권2호
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• pp.83-91
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• 2006

In this paper, we develop space-time(ST) Rake receivers for Time Division Synchronous Code Division Multiple Access(TD-SCDMA) base stations(BS). The beamforming of BS transforms the uplink MIMO channel space into many sub-sectors' channels to be nearly orthogonal, thus, well established 1-D Rake technology can be used to TD-SCDMA base station to construct ST Rake, which simplified the system's implementation as well as enlarged users' capacity by the beamforming. The construction and capacity of MIMO sub-sectors by multi-beamforming have been presented. The proposed ST Rake algorithm include the multi-beamforming algorithm for MIMO sub-sectors and classical 1-D Rake algorithm. The calculating formulas for interference plus noise ratio(SINR) and bit error rate(BER) have been derived. Simulations verify that the proposed ST Rake receiver for BS is effective, and the BS systems can get higher system capacity and can be of better performance than presented TD-SCDMA systems.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.267-268
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• 2008

TD-SCDMA is considered as an innovative Chinese 3G technology adopted by the ITU for the IMT-2000 family. TD-SCDMA combines TDMA and CDMA components to provide more efficient use of radio resources. According to the traffic volume and activity level, the operation mode of a mobile terminal can change from one state to other states. This paper focuses on the problem of recovery delay from inactive states, and proposes a resource management algorithm, which holds some resources for rapid recovery of service after the service determines to release the dedicated resources.