• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.45-55
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• 2010

While Long Term Evolution-Frequency Division Duplexing (LTE-FDD) is regarded as one of the strong candidates for "4G" wireless broadband access in FDD field, LTE-Time Division Duplexing (TDD) is emerging as one possible migration path for WiMAX-TDD in some cases as well as the migration path for Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). In this paper, we analyze the feasibility of dual mode with LTE-TDD in two combinations: dual mode LTE-FDD/TDD and dual mode Worldwide Interoperability for Microwave Access (WiMAX)-TDD/LTE-TDD. Thanks to the commonality in numerology, terminology, and frame structure between LTE-FDD and LTE-TDD, dual mode LTE-FDD/TDD looks feasible in a cost-effective manner. Thanks to the commonality in scheduling algorithm, control mechanism, and supported spectrum bands, it is shown that dual mode WiMAX-TDD/LTE-TDD looks feasible as well. It should be also noted that the commonality in numerology and frame structure is critical for building a chip while the commonality in algorithms and control mechanisms is critical to make it work.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.104-116
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• 2010

With several advantages such as flexible downlink-to-uplink(DL-to-UL) ratio and flexible spectrum usage, Time Division Duplexing(TDD) is emerging as an alternate to Frequency Division Duplexing(FDD), especially in wireless broadband systems. We already have at least four different TDD systems in the industry: Time Division-Synchronous Code Division Multiple Access(TD-SCDMA), IEEE 802.16e-TDD, IEEE 802.16m-TDD, and Time Division-Long Term Evolution(TD-LTE). A disadvantage of TDD is that tight coordination such as time synchronization between adjacent operators is required to prevent interference between the adjacent TDD systems. In this paper, we investigate coexistence scenarios among the above four well-known TDD systems and calculate spectral efficiency(SE) loss in each scenario. Our findings are that SE loss can be significant if TDD ratios of the adjacent operators are considerably different. However, as long as the TDD ratios of the adjacent operators are similar, configurations in the systems permit perfect time synchronization between the two heterogeneous TDD systems, and the resulting SE loss is zero or reasonably low. We believe that the above findings and the configurations of the TDD systems recommended tominimize SE loss will be helpful for operators who deploy TDD systems in system parameter determination and cross-operator coordination.

• Electronics and Telecommunications Trends
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• v.32 no.2
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• pp.80-89
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• 2017

국내 이동통신은 상향과 하향 신호를 주파수 대역으로 구분하는 주파수분할(FDD: Frequency Division Duplex) 방식을 중심으로 발전해 왔으나, 최근 가용 주파수가 줄어드는 상황에서 5G 대응 및 모바일 생태계의 지속적인 발전을 위해 상향과 하향을 시간으로 구분하는 시분할(TDD: Time Division Duplex) 방식의 주파수 활용에 대한 필요성이 높아지는 추세이다. 또한, 주파수 이용 효율성, 주파수 확보 용이성, FDD-TDD 상호 호환성, TDD 생태계 조성의 필요성, 5G 신기술 수용 및 확장성 등을 고려할 때 국내 TDD 주파수 정책은 분명 새로운 전환 국면을 맞이하고 있으며, 이에 국내 환경에 적합한 TDD 정책방향을 탐색하기 위해 최근 국내외 LTE-TDD 서비스 및 시장, 주파수 및 기술 동향을 살펴보고, 향후 TDD 활용 전망을 제시하고자 하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.21-30
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• 2004

The capacity of WCDMA TDD system is limited mainly by the interference. So, to achieve the expected performance of WCDMA TDD system and to minimize the interference to cdma2000 system interferences, such as interference within WCDMA TDD system inter-cell interference, and interferences between cdma2000 systems, should be considered carefully. In this paper, by using System-level Simulation, we analyzed the interferences between WCDMA TDD system and cdma2000 system in practical situation based on the exact parameters of 3GPP TR 25.942 and by using System-level Simulation considering Link-level we analyze the interferences between WCDMA TDD system and cdam2000 system. From Simulation Results, we propose the condition for optimizing system capacity considering the interferences between WCDMA TDD system ＆ cdam2000 system

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.161-168
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• 2019

This paper proposes a variable data transfer asymmetric TDD(Time Division Duplex) system for small UAV(Unmanned Aerial Vehicle) data link system. In the proposed method, a turbo decoder with a double buffer controller is proposed to apply turbo decoder with long decoding time to asymmetric TDD system. The proposed method achieves variable data transfer rate and maximum data transfer rate. The advantage of the proposed method is demonstrated by its data transfer rate. The measured data transfer rate is more than 1.8 times than that of symmetric TDD system. In addition, PER(Packet Error Rate) performance is the same and data transfer rate is variable.

• ETRI Journal
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• v.32 no.4
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• pp.503-511
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• 2010

WiBro radio frequency (RF) repeater is used for solving the problem of partial shadow areas in the wireless communication field that uses time-division duplexing (TDD) mode. In this paper, a method to efficiently generate TDD signals for WiBro RF repeater is proposed and its digital circuit is implemented. A TDD signal is detected from RF signals transmitted/received to/from RF repeater and then inputted again into the RF repeater, so that it can operate normally. First, the envelope of downlink signals is detected and then clamped to extract the basic form of a TDD signal using an operational amplifier circuit. Next, the TDD signal is generated by restoring and filtering the shape which has been distorted by the wireless channel. The algorithm and system to acquire TDD signal are developed with a goal to have simple but powerful functions with as little cost as possible. The proposed method is implemented as an RF-digital integrated system and verified through the experiments under the same condition as actual WiBro service environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.909-917
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• 2009

In this paper, we proposed and implemented the method to efficiently generate TDD synchronization signal and the digital circuit for the RF repeater which can eliminate the shadow region in the wireless communication field using the time division duplex (TDD) method. After detecting the TDD signal from the transmitted or received RF signal, the detected TDD signal is fed to the RF repeater for the normal operation. The proposed technique detects the envelop of the downlink signal and amplifies the detected envelop, and then restores the degraded envelop with the proposed digital filtering method. Finally the restored envelop is manipulated to the TDD synchronization signal. Our focus on the proposed algorithm is to develop it with simple feature and low cost but robust performance. The proposed scheme was implemented to the integrated system which has both RF and digital circuit and tested under the same condition with the commercial WiBro service.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.11
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• pp.32-36
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• 2008

In this paper, we investigate the capacity of CDMA/TDD in the inner zone of multimode scenario with dual-band operation where high frequency band is used for TDD in the inner zone and lower frequency band is utilized for FDD in the outer zone. The effects of various system parameters such as cell radius, date rate, and time slot allocation are analyzed.

• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.45-50
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• 2011

In this paper, the encoding time delay of FH/TDD(Frequency Hopping/Time Division Duplex) based Motion JPEG image compression CODEC is analyzed for radio video transmissions of multi-camera systems in a vehicle. And, Synchronized connection of minimum channel collision is designed with synchronized shift and access according to channel status for Motion JPEG based FH/TDD multiple access.

• Journal of Korea Multimedia Society
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• v.16 no.7
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• pp.862-869
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• 2013

In order to support a cell-independent traffic asymmetry, the conventional TDD system cannot avoid crossed time slot (CTS) interference. Moreover, the TDD/FDD hierarchical overlay cellular systems is taken into account as a generally accepted cell model in a heterogeneous radio environment. In this paper, we propose an interference resolving radio resource allocation technique in a TDD-OFDMA cellular system that overlays a FDD-CDMA cell. In our proposed scheme, we exploit under-used FDD-CDMA uplink resource by TDD mobile abiding by a region based time slot(TS) allocation which in turn mitigates CTS interference considerably. It is demonstrated that combined with under-used resource utilization scheme based on mobile's location, the proposed technique can reduce CTS interference considerably and support the asymmetric traffic in TDD system.