• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.52-57
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• 2016

We introduce a hybrid scheduling in a multi-path poor scattering full-duplex (FD) system, which consists of one multi-antenna FD base station and a large number of single-antenna half-duplex mobile stations. Our hybrid scheduling utilizes partial channel state information at the transmitter. In particular, unlike the conventional scheduling method using opportunistic transmission for both uplink and downlink, the proposed scheme combines a random transmit beamforming for downlink and a zero forcing beamforming for uplink. As our main result, via computer simulations, it is shown that the proposed scheme has a superior sum-rate performance than that of the conventional scheduling method beyond a certain signal-to-noise ratio regime.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.204-209
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• 2003

In an urban area telecommunication using wireless system, the accurate prediction and analysis of wave propagation characteristics are very important to determine the service area, optimized selection of base station, and cell design, etc. In the stage of these analyses, we have to present the propagation prediction model which is varied with the type of antenna, directional angle, and configuration of the ground in our urban area. In addition we need to perform an analysis of the conventional model which is similar to ours and dig out the parameters to evaluate the wave environment before the cell design for the selected area. In this paper, we propose a wave propagation prediction model concerning the topography and obstacles in our urban area. We extract the parameters and apply them to the proposed wave environment for the simulation analyzing the propagation characteristics. Throughout these analyzing procedure, we extracted the essential parameters such as the position of the base station, the height of topography, and adequate type and height of the antenna with our preferable correctness.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.10
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• pp.3-9
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• 2016

Current mobile communication systems utilize the multiple-input multiple-output (MIMO) transmission technique as an important means to enhance the bandwidth efficiency. Accurate beamforming via channel estimation contributes to the signal-to-interference-plus-noise ratio (SINR) increase and the system performance improvement when MIMO transmission techniques are employed. Therefore, determination of beamforming vectors as well as the design of appropriate codebooks defining these codevectors play an important role in system operation. In this paper, we statistically analyze the phase difference between the channels corresponding to adjacent antenna elements in order to design an efficient codebook for uniform circular arrays (UCAs). We introduce new parameters which compensate for the additional phase difference observed in its probability density functions (PDFs). The performance of the proposed codebook is tested using the spatial channel model (SCM) to demonstrate its gain over the standard codebooks adopted in the long term evolution (LTE) Releases 8 and 10.

• The Journal of the Korea Contents Association
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• v.4 no.2
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• pp.21-27
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• 2004

In an urban area telecommunication using wireless system, the accurate prediction and analysis of wave propagation characteristics are very important to determine the service area optimized selection of base station, and eel design, etc. In the stage of these analyses, we have to present the propagation prediction mood which is varied with the type of antenna, directional angle, and configuration of the ground in our urban area in addition we need to perform an analysis of the conventional mode which is similar to ours and dig out the parameters to evaluate the wave environment before the cell design for the selected area. In this paper, we propose a wave propagation prediction model concerning the topography and obstacles in our urban area. We extract the parameters and apply them to the proposed wave environment for the simulation analyzing the propagation characteristics. Throughout these analyzing procedure, we extracted the essential parameters such as the position of the base station, the height of topography, and adequate type and height of the antenna with our preferable cuteness.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.35-40
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• 2007

As the mobile communication service is widely used and the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But a wireless repeater has a problem that the output of the transmit antenna is partially fed back to the receive antenna, which results in feedback interference. In this paper, we propose a new varable step-size LMS algorithm which utilizes correlation between reference and error signals to adjust the step sizes, for cancelling the feedback interference signals in the WCDMA repeater under time-varying multi-path channels. The proposed algorithm was evaluated through computer simualation by being applied to the feedback canceling filter of the WCDMA repeater. The simulation results demonstrated that the proposed one is superior to the conventional ones in terms of the cancelation perormance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2B
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• pp.170-177
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• 2009

In this paper, we propose the structures of the NBTC (Narrow-Beam Trisector Cell) and the WBTC(Wide-Beam Trisector Cell) in which directional antennas both at the base station and at the relay station are used. We analyze and compare total capacity of the both systems taking the co-channel interference into consideration for two channel models. Through analysis, we find the effect of LOS (Lind of Sight) path to the total capacity of NBTC structure and that of WBTC structure. Our work may be useful as a guideline to control the interference for the next generation mobile communication and WiBro systems using multi-hop relays.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.123-129
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• 2018

Recently, as required wireless communication traffic increase, millimeter wave mobile technologies that can secure broadband spectrum are gaining attention. However, the path loss is high in the millimeter wave channel. Massive MIMO system is being researched in which can complement the path loss by beamforming by equiped large-scale antenna at the base station. While legacy beamforming techniques have analog and digital methods, practical difficulties exist for application to massive MIMO systems in terms of system complexity and cost. Therefore, this paper studies a hybrid beamforming scheme for massive MIMO system in the millimeter wave band. Also this paper considers spatial multiplexing scheme to serve multi-users with multiple received antennas. Gains of the beamforming and the spatial multiplexing schemes are evaluated by analyzing the spectral efficiency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.4
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• pp.508-514
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• 2020

To implement the continuously evolving mobile communication standards such as Long Term Evolution (LTE) and 5G, the Software Defined Radio (SDR) concept provides great flexibility and efficiency. For many years, a high-end Digital Signal Processor (DSP) System on Chip (SoC) has been developed to support multicore and various hardware coprocessors. This paper introduces the implementation of the SDR platform hardware using TI's TCI663x chip. Using the platform, LTE transport channel is implemented by interworking multicore DSP with Bit rate Coprocessor (BCP) and Turbo Decoder Coprocessor (TCP) and the performance is evaluated according to various implementation options. In order to evaluate the performance of the implemented LTE transport channel, LTE base station system was constructed by combining FPGA main board for physical channels, SDR platform board, and RF & Antenna board.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.2B
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• pp.120-129
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• 2012

Wireless mesh network (WMN) has recently emerged as a promising technology for tactical operation. If a platoon is organized with MPs, this system is suitable for tactical coverage is given for battle field where there is a shortage of wired infrastructure. However, MPs of typical WMN are generally fixed. This condition does not apply to diverse tactical scenarios. In this paper, it is considered that MPs have group mobility for flexible tactical networks. We propose cluster based multi-channel MAC scheme for mobilie WMN with single antenna condition. We have reduced the collision problems and message storming problems occur by mobility, so the reliability of WMN has been improved. Consequently, reliable communication is guaranteed by our framework in mobile WMN.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.2 s.5
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• pp.9-17
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• 2004

In this paper, we examine the MIMO(Multiple Input Multiple Output) system in the point of mobile communication that is used for railway environment. First, under the radio environment, wireless channel characteristics are analyzed between moving train and base station, both assuming track side base stations and non-track side base stations. Next, the paper introduces the MIMO system which can be used to solve the problem of performance degradation in railway environment, and analyzes its performance in terms of channel capacity and diversity. We especially compares open-loop scheme with closed loop scheme at the diversity and analyses their performance according to antenna correlation. Finally, the we presents experimental result from the ESCORT project that was studied in railway environment with the MIMO system.