• Current Optics and Photonics
• /
• v.6 no.1
• /
• pp.23-31
• /
• 2022

Heterodyne efficiency is an indicator to evaluate the performance of space coherent laser communication systems. It is affected by signal light and local oscillator (LO) light amplitude, phase and polarization state. In this paper, based on the common heterodyne efficiency, a heterodyne efficiency model that can reflect polarization aberration of optical system is proposed. The heterodyne efficiency is analyzed when the signal light and the LO light are linearly polarized or circularly polarized. For a coherent communication optical system, when the incident signal light is right-circularly polarized light and the incident LO light is 45° linear polarized light. Based on the three-dimensional ray tracing theory and the heterodyne efficiency proposed in this paper, the change of polarization states and the distribution of heterodyne efficiency of the signal light and LO light influenced by the optical system's polarization aberration are analyzed. Analysis shows that the heterodyne efficiency model proposed in this paper can be used to evaluate coherent communication systems and reflect the influence of optical system polarization aberration.

• Journal of IKEEE
• /
• v.27 no.4
• /
• pp.579-586
• /
• 2023

Device-to-Device communication is a very important essential feature in PPDR(Public Protection Disaster Relief) communication, but it has not yet been implemented in LTE-based PPDR communication. In this study, we propose a solution to implement the LTE-based domestic PPDR communication network by evolving the terminals into D2D in-band terminals and effectively operating the current PS-LTE terminals and digital radios in the transitional period.

• Journal of Electrical Engineering and information Science
• /
• v.1 no.2
• /
• pp.15-26
• /
• 1996

MPAs(Massively Parallel Architectures) should address two fundamental issues for scalability: synchronization and communication latency. Dataflow architecture faces problems of excessive synchronization overhead and inefficient execution of sequential programs while they offer the ability to exploit massive parallelism inherent in programs. In contrast, MPAs based on von Neumann computational model may suffer from inefficient synchronization mechanism and communication latency. DAVRID (DAtaflow/Von Neumann RISC hybrID) is a massively parallel multithreaded architecture which takes advantages of von Neumann and dataflow models. It has good single thread performance as well as tolerates synchronization and communication latency. In this paper, we describe the DAVRID architecture in detail and evaluate its performance through simulation runs over several benchmarks.

• Journal of Korean Academy of Nursing
• /
• v.44 no.3
• /
• pp.317-327
• /
• 2014

Purpose: This study was done to compare families of boys or of girls for actor and partner effect of stress, depression and parent-adolescent communication as perceived by mother, father and adolescent on adolescents' suicidal ideation. Methods: Participants were 183 families (104 boys' families, 79 girls' families) who met eligibility criteria. All measures were self-administered. Data were analyzed using SPSS 18.0 and AMOS 18.0 program. Results: In boys' families, boys' depression and communication with father showed actor effect on boys' suicidal ideation. Boys' stress showed indirect effect on boys' suicidal ideation through communication with father and boys' depression. Mothers' depression showed indirect partner effect on boys' suicidal ideation through boys' depression. In families of girls, girls' depression and stress showed actor effects on girls' suicidal ideation. Girls' communication with mother showed indirect effects through girls' depression. Also girls' stress showed indirect effect through girls' depression. Stress in mothers and/or fathers showed partner effect on girls' suicidal ideation. Conclusion: To intervene in adolescents' suicidal ideation and promote adolescents' mental health, programs should be developed differently according to gender and based on parent's psychological states.

• Journal of Broadcast Engineering
• /
• v.14 no.4
• /
• pp.475-487
• /
• 2009

We propose a visible light road-to-vehicle communication system at intersection as one of ITS technique. In this system, the communication between vehicle and a LED traffic light is approached using LED traffic light as a transmitter, and on-vehicle high-speed camera as a receiver. The LEDs in the transmitter are emitted in 500Hz and those emitting LEDs are captured by a high-speed camera for making communication. Here, the luminance value of each LED in the transmitter should be found for consecutive frames to achieve effective communication. For this purpose, first the transmitter should be identified, then it should be tracked for consecutive frames while the vehicle is moving, by processing the images from the high-speed camera. In our previous work, the transmitter was identified by getting the subtraction of two consecutive frames. In this paper, we mainly introduce an algorithm to track the identified transmitter in consecutive frames. Experimental results using appropriate images showed the effectiveness of the proposal.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.5
• /
• pp.2357-2380
• /
• 2019

In this paper, we investigate the impact of hardware impairments (HWIs) on the performance of a downlink massive MIMO system. We consider a single-cell system with maximum ratio transmission (MRT) as precoding scheme, and with all the HWIs characteristics such as phase noise, distortion noise, and amplified thermal noise. Based on the system model, we derive closed-form expressions for a typical user data rate under two scenarios: when a common local oscillator (CLO) is used at the base station and when separated oscillators (SLOs) are used. We also derive closed-form expressions for the downlink transmit power required for some desired per-user data rate under each scenario. Compared to the conventional system with ideal transceiver hardware, our results show that impairments of hardware make a finite upper limit on the user's downlink channel capacity; and as the number of base station antennas grows large, it is only the hardware impairments at the users that mainly limit the capacity. Our results also show that SLOs configuration provides higher data rate than CLO at the price of higher power consumption. An approach to minimize the effect of the hardware impairments on the system performance is also proposed in the paper. In our approach, we show that by reducing the cell size, the effect of accumulated phase noise during channel estimation time is minimized and hence the user capacity is increased, and the downlink transmit power is decreased.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.11 no.5
• /
• pp.608-614
• /
• 2018

In addition to the diffusion of ICT technology, various protocols of short range wireless communication technology are being applied for efficient information operation. However, due to limitations of short-range wireless communication, communication is not smooth in places where frequency environment is poor, such as frequency confusion and warehouse type factory. When an alternative is needed. The development of LED technology and expansion of infrastructure through LED based visible light communication is attracting attention as an alternative and spreading the usage in wide range now a days. In addition, the infrastructure has been expanded with solar panels in response to the development of smarthome built-in with renewable energy. In this situation, visible light communication using PD has been limitedly applied in a near environment where the receiving angle of the PD and the ambient light ensure the LoS and the influence of the ambient light is small. In order to solve this problem, we have implemented visible light communication using LED lighting with large current infrastructure and solar panel with large receiving area, and proposed a circuit for restoring accurate data even in ambient light. Through this study results, it is expected that visible light communication can be more widely used and this result used as the base data for visible light communication research using the solar panel as the receiver.

• Journal of dental hygiene science
• /
• v.16 no.2
• /
• pp.134-141
• /
• 2016

The purpose of this study was to develop a dental communication course in dental hygiene schools that included theory, practice, and skill for effective dental communication. Thirty-six senior dental hygiene students in a dental hygiene school took a dental communication course and responded to a questionnaire. The instrument used in the study was a modified form of Kim's communication skill self-assessment sheet. The self-assessment questionnaire about communication competencies was administered before and after the class, and the difference between scores at each time point was analyzed using the Wilcoxon signed rank sum test. Among seven elements of dental communication competencies, the competency of "information gathering" was significantly improved (p=0.008). Students' scores on perception of the importance (p=0.019) and necessity (0.016) of a communication course significantly increased after the course. Competencies in communication are essential requirement for dental hygienists. This study showed the possibility of communication skill training. An objective evaluation tool regarding students' communication competencies should be developed. Further studies with larger samples size are needed to develop a standardized comprehensive communication course in dental hygiene schools.

• Proceedings of the Korean Information Science Society Conference
• /
• 2011.06d
• /
• pp.213-214
• /
• 2011

This paper presents a distributed relay selection algorithm for cooperative communication. The algorithm separates the decision making into two simple steps, decision making for employing cooperative communication and decision making for relay selection.

• Proceedings of the Korea Society for Simulation Conference
• /
• 1991.10a
• /
• pp.41-77
• /
• 1991

A large number of R & D projects in automobile information and communication systems have been achieved in these twenty years to improve various aspects on automobile usage. Examples on simulation for evaluation of these systems such as these on road to vehicle communication, inter-vehicle communication, and vehicle guidance are shown.