• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.8
• /
• pp.681-687
• /
• 2014

Internet traffic is rapidly increasing due to the spread of personal smart devices. It causes serious burden on base stations and access points which are installed in buildings, buses, trains, and ships. We consider a communication scenario aboard a cruise ship and propose efficient contents distribution schemes to alleviate the burden of access points with multi-device-to-multi-device(MD2MD) communication. The proposed transmission method is based on the hybrid STBC-SM scheme. We compare the error performance of MD2MD communication system on the cruise ship using space-time block coding (STBC) scheme, spatial multiplexing (SM) scheme. The proposed MD2MD communication system is expected to adopt in the ship-area-network (SAN) with efficient contents distribution and reliable communication.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.12A
• /
• pp.1209-1216
• /
• 2008

In order to maximize spectrum efficiency and data rate MIMO(Multiple Input Multiple Output) is adopted to wireless system. OFDM-based WiMAX and LTE accommodate MIMO as mandatory technology. STC(Space Time Coding) and SM(Spatial Multiplexing) are used in downlink while in uplink C-MIMO(Collaborative MIMO) is used to improve data throughput. In this paper conventional pairing schemes, RPS(Random Pairing Scheduling) and DPS(Determinant Pairing Scheduling) are analyzed. From the analysis the performance of DPS algorithm is better than that of RPS because DPS measures orthogonal factor between paired users. However, there are potential problems such as hardware complexity and performance. To overcome the issues Power-Based Scheduling(PBS) algorithm is proposed for C-MIMO. PBS can provide higher performance compared to RPS and dramatically reduce hardware complexity compared to DPS

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.7A
• /
• pp.640-648
• /
• 2011

We propose relay selection schemes using STBC (Space Time Block Coding) technique in OFDM (Orthogonal Frequency Division Multiplexing)-based wireless systems. The proposed schemes select the optimum relay having the maximum instantaneous equivalent channel gain among multiple candidate relays. Also, in order to reduce the system overhead, a symbol grouping method which groups some amount of symbols before selecting the optimum relay is proposed. The simulation results show that the proposed relay selection schemes can obtain more selection diversity gain as the number of selectable relay candidates increases. Furthermore, the proposed scheme with the symbol grouping can reduce system overhead without any degradation of the performance in fading channels with low frequency selectivity.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.10C
• /
• pp.923-929
• /
• 2003

Turbo processing have been known as methods close to Shannon limit in the aspect of wireless multi-input multi-output (MIMO) communications similarly to wireless single antenna communication. The iterative processing can maximize the mutual effect of coding and interference cancellation, but LDPC coding has not been used for turbo processing because of the inherent decoding process delay. This paper suggests a LDPC coded MIMO system with turbo parallel space-time (Turbo-PAST) processing for high-speed wireless communications and proposes a average soft-output syndrome (ASS) check scheme at low signal to noise ratio (SNR) for the Turbo-PAST system to decide the reliability of decoded frame. Simulation results show that the suggested system outperforms conventional system and the proposed ASS scheme effectively reduces the amount of turbo processing iterations without performance degradation from the point of average number of iterations.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.2
• /
• pp.385-391
• /
• 2007

In this paper, we propose and observe the Adaptive Modulation system with optimal Turbo Coded V-BLAST (Vertical-Bell-lab Layered Space-Time) technique that is applied the extrinsic information from MAP (Maximum A Posteriori) Decoder with Iterative Decoding to use as a priori probability in two decoding procedures of V-BLAST: ordering and slicing. Also, comparing with the Adaptive Modulation system using conventional Turbo Coded V-BLAST technique that is simply combined V-BLAST with Turbo Coding scheme, we observe how much throughput performance has been improved. As a result of simulation, in the Adaptive Modulation systems with several Turbo Coded V-BLAST techniques, the optimal Turbo Coded V-BLAST technique has higher throughput gain than the conventional Turbo Coded V-BLAST technique. Especially, the results show that the proposed scheme achieves the gain of 1.5 dB SNR compared to the conventional system at 2.5 Mbps throughput.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.7
• /
• pp.515-521
• /
• 2022

In this paper, we propose Quad BTC that compresses DSM files to allow random access for TRF (Terrain Referenced Flight). The terrain data used for TRF has a large data capacity to be stored in the UAV (Unmanned Aerial Vehicle), so its size must be reduced through compression. Conventional BTC (Block Truncation Coding) based compression methods are suitable for TRF because it can decode randomly accessing specific coordinates. However, These conventional methods have a problem that the error increases because the deviation of the data increases as the size of the block increases. In this paper, we propose Quad BTC method that adaptively divides a block in to 4 sub blocks and compresses to solve this problem. The proposed method may reduce errors because the size of the sub block can be adjusted within the block. Through simulation using actual terrain data, it is verified that Quad BTC has less error at the same compression ratio than conventional BTC and AM BTC.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.6
• /
• pp.473-480
• /
• 2021

In this paper, We analyze and present improvements to problems in software quality through Static Analysis for Open Source, which is widely used as the Flight Controller software for small unmanned aerial vehicle drones. MISRA coding rules, which are widely applied based on software quality, have been selected. Static analysis tools were used by LDRA tools certified international tools used in all industries, including automobiles, railways, nuclear power and healthcare, as well as aviation. We have identified some safety-threatening problems across the quality of the software, such as structure of open source modules, analysis of usage data, compliance with coding rules, and quality indicators (complexity and testability), and have presented improvements.

• Journal of Industrial Convergence
• /
• v.22 no.2
• /
• pp.55-62
• /
• 2024

Visible light communication, which transmits information using visible light, has advantages such as ultra-high speed, ultra-delay, and ultra-connectivity, so research is being conducted as a way to complement 6G communication. In this paper, a study was conducted to overcome the performance degradation caused by the RGB mixing ratio in visible light communication. In a visible light communication system using LED lighting, the role of lighting is an important function, and when used for communication, the performance difference according to the RGB mixing ratio inevitably occurs. In particular, if the intensity of light is below a certain standard, the problem of deteriorating the performance of the entire system occurs. In this study, when a certain performance or less occurs in the communication system caused by the difference in the mixing ratio among the three RGB channels, the remaining two signals except the LED with the best performance are transmitted to STBC (Space-Time Block Coding) to ensure the quality of communication. A computer simulation was performed to verify the performance of the proposed system, and it can be seen that the performance of the proposed system is improved compared to the existing system.

• Architectural research
• /
• v.16 no.2
• /
• pp.37-44
• /
• 2014

Utilizing spaces for awareness could be superficially noble. However, the typology of spaces played an important role in addressing the awareness of translating the messages through tangible forms, which in this context are sculptures. Assuring the efficacy of the typology of the spaces that is compatible with the content is important to ensure its timelessness to the dynamic demographical change of viewers. Therefore, the study proposes an investigation of the efficacy of typology of public urban space; garden that accommodates memorial sculptures. The study intends to analyze the features and flaws of ASEAN Sculpture Garden, as a mediatory role of ASEAN in instilling awareness of unity between ASEAN members to the public. The objective of the study is to analyze the efficacy of the garden to accommodate the rich memorial sculptures. The body of the research is formed by theoretical and case study research. It is projected by three methods; archival research, semi structured interviews and site documentation; direct observations and site visit. The qualitative data then will be analysed using Actor Network theory, keyword coding and site findings. Findings showed that as the main objective of the garden is to exhibit the sculptures, it could be summed up that it has failed to meet the apparent intention based on the site analysis conducted by the researcher. The typology of the space should be able to communicate the project's aims continuously rather than serving the function temporarily. The variables, which are space and time factors are debatable, as the neighboring tourist spot, National Monument residing the wide square managed to attract public attention due to its great efficacy of typological space regardless the time factor. As a conclusion, the typology of space is a huge factor to ensure the park's success.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.41 no.3
• /
• pp.167-167
• /
• 2004

The system combined layered space-time processing and space-time trellis codes (STTC) provide high transmission rate as well as diversity and coding gain without bandwidth expansion. In this paper, two layered receiver structures are proposed. One is the LSTT-MMSE in which received bit streams are decoupled by interference nulling and then decoded by separate STTC decoders. The decoded outputs are cancelled from the received signal before advancing to the next layer detection. The other is LSTT-Whitening employing whitening rather than nulling. The receiver employing whitening process shows several advantages on diversity gain and the required number of receive antennas compare to the convolutional coded space-time processing. The proposed receivers use different decoding order scheme according to each interference suwression. The (4, 3) LSTT-Whitening receiver still achieves 1㏈ gain over the (4, 4) LSTT-MMSE and the (4, 4) coded layered space-time processing.