• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.5
• /
• pp.358-363
• /
• 2019

If the EOIR equipment mounted on an unmanned aircraft transmits images and receives commands through a data link, there may be delays in data transmission depending on the transmission path of the data and the conditions of the ground equipment or wireless network. This increases the possibility of initial target LOCK-ON failure due to the difference between the time when the received image is viewed and the time when the image is taken. Therefore, this paper proposed a way to use frame indexes to synchronize with images, and to increase the success of target tracking by adding frame indexes to commands from the ground station.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.6
• /
• pp.515-519
• /
• 2021

IEEE 1588 PTP is a precision time protocol in which two systems synchronize without the aid of GPS by exchanging packets including transmission/reception time information. In the time synchronization process, the propagation delay time can be calculated and the distance between the two systems can be measured using this. In this paper, we proposed a method to improve the distance measurement precision less than the modulation symbol period using the timing error information extracted from the preamble of the received packet. Computer simulations show that the distance measurement precision is proportional to the length of the preamble PN sequence and the signal-to-noise ratio.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.26 no.3
• /
• pp.449-455
• /
• 2022

In this paper, we propose a position measuring system using trilateration based on the illuminance of a light-emitting diode (LED). Three LEDs are located on the ceiling of the virtual space, and each fixed coordinate is inputted to the monitoring program, and Length to the illuminance sensor is drawn through the relational expression of the length and illuminance value from the respective LED. Based on the derived length, the trilateration method is used to find object location information in virtual space. By using the least square equation to minimize the error of the length drawn to trilateration, the error is reduced to the utmost. Unlike the existing indoor positioning system using visible light communication (VLC), the proposed system does not require synchronization between the transmitter and the receiver, so the system can be configured simply.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.2
• /
• pp.9-14
• /
• 2006

Galileo is the European Global Navigation Satellite System, under civilian control, and consists on a constellation of medium Earth orbit satellites and its associated ground infrastructure. Galileo will provide to their users highly accurate global positioning services and their associated integrity information. The elements in charge of the computation of Galileo navigation and integrity information are the OSPF (Orbit Synchronization Processing Facility) and IPF (Integrity Processing Facility), within the Galileo Ground Mission Segment (GMS). Navigation algorithms play a key role in the provision of the Galileo Mission, since they are responsible for computing the essential information the users need to calculate their position: the satellite ephemeris and clock offsets. Such information is generated in the Galileo Ground Mission Segment and broadcast by the satellites within the navigation signal, together with the expected a-priori accuracy (SISA: Signal-In-Space Accuracy), which is the parameter that in fault-free conditions makes the overbounding the predicted ephemeris and clock model errors for the Worst User Location. In parallel, the integrity algorithms of the GMS are responsible of providing a real-time monitoring of the satellite status with timely alarm messages in case of failures. The accuracy of the integrity monitoring system is characterized by the SISMA (Signal In Space Monitoring Accuracy), which is also broadcast to the users through the integrity message.

• Journal of Positioning, Navigation, and Timing
• /
• v.12 no.4
• /
• pp.335-342
• /
• 2023

Lunar Navigation Satellite System refers to a constellation of satellite providing PNT services on the moon. LNSS consists of main satellite and navigation satellites. Navigation satellites orbiting around the moon and a main satellite moves the area between the moon and the L2 point. The navigation satellite performs the same role as the Earth's GNSS satellite, and the main satellite communicates with the Earth for time synchronization. Due to the effect of the non-uniform shape of the moon, it is necessary to focus on the influence of the lunar gravitational field when designing the orbit simulation for navigation satellite. Since the main satellite is farther away from the moon than the navigation satellite, both the earth's gravity and the moon's gravity must be considered simultaneously when designing the orbit simulation for main satellite. Therefore, the main satellite orbit simulation must be designed through the three-body problem between the Earth, the moon, and the main satellite. In this paper, the orbit simulation tool for main satellite and navigation satellite required for LNSS was designed. The orbit simulation considers the environment characteristics of the moon. As a result of comparing long-term data (180 days) with the commercial program GMAT, it was confirmed that there was an error of about 1 m.

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.5
• /
• pp.532-536
• /
• 2008

In this paper, we propose the method to measure tensions of character motions, using LMA (Laban Movement Analysis). Using tension values, we tan take advantage of them as a standard for synchronization of motion and BGM(Back Ground Music). In LMA, a motion is divided into 4 space-time factors which are called Efforts, and each Effort has two bases opposed to each other. We can analyze the motion by justifying which basis is stronger than the other in each Effort of motion. To measure quantitatively tension values, we propose some equations based on kinematics and dynamics. Then we can measure the tension value by the weighted sum of values calculated from those equations. Each weight can be determined by the optimization process which tries to minimize the difference between the calculated tension value and human's decision. The experimental result shows that the in creasing order of the motion tension value is similar to that of the tension score given by human.

• Journal of Internet Computing and Services
• /
• v.8 no.2
• /
• pp.1-13
• /
• 2007

GPS/GIS and RFID technologies have been changing the paradigm af our society toward ubiquitous era. Especially, geographically distributed mobile agents with transporting objects need to be automatically recognizable and traceable under certain conditions. To do this, fundamental theories and technologies are required to specify and verify spatial and temporal behaviors of agents on geographical space. This paper presents a new formal method, called Calculus of Real-Time Distribution, Mobility, and Interaction (CaRDMI), for this purpose. For specification, CaRDMI defines a map, mobile agents with transporting objects. The movement of on agent is represented by a path on the map, consisting of a list of nodes and a list of edges with spatial and temporal constraints. Interactive constraints among agents are represented by synchronization modes on objects at nodes. These constraints are distinguishable features of CaRDMI from other methods. Especially, many-to-many timed synchronization constraints are noticeable. For verification, CaRDMI presents the spatial, temporal and interactive deduction rules and the spatial and temporal equivalence relations.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.5C
• /
• pp.479-486
• /
• 2010

In this paper, we propose a novel low-complexity Alamouti coded orthogonal frequency division multiplexing (OFDM) scheme for asynchronous cooperative communications. Exploiting the combination of OFDM symbols at the source node and simple operations including sign change and complex product at the relay node, the proposed scheme can achieve cooperative diversity gain without use of time-reversion and shifting operations that the conventional scheme proposed by Li and Xia needs. In addition, by using the cyclic prefix (CP) removal and insertion operations at the relay node, the proposed scheme does not suffer from a considerable degradation of bit-error-rate (BER) performance even though perfect timing synchronization is not achieved at the relay node. From the simulation results, it is demonstrated that the BER performance of the proposed scheme is much superior to that of the conventional scheme in the presence of timing synchronization error at the relay node. It is also shown that the proposed scheme obtains two times higher diversity gain compared with the conventional scheme at the cost of half reduction in transmission efficiency.

• Industrial Engineering and Management Systems
• /
• v.8 no.3
• /
• pp.155-161
• /
• 2009

We focus on discrete event systems with a structure of parallel processing, synchronization, and no-concurrency. We use max-plus algebra, which is an effective approach for controller design for this type of system, for modeling and formulation. Since a typical feature of this type of system is that the initial schedule is frequently changed due to unpredictable disturbances, we use a simple model and numerical examples to examine the possibility of applying the concepts of the feeding buffer and the project buffer of critical chain project management (CCPM) on max-plus linear discrete event systems in order to control the occurrence of an undesirable state change. The application of a CCPM-based framework on a max-plus linear discrete event system was proven to be effective.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.1203-1208
• /
• 2010

Recently, there are environmental issues for sustainable transportation system to pursue the energy-efficient and environment-friendly public urban transit. These transportation system needs to offer demand-oriented high-quality service being on the same level with cab service for urban space. PRT(Personal Rapid Transit), small track-guided vehicle, is repeatedly mentioned as a possible alternative for the new urban public transportion system, but but there are not many researches on the operational optimal routing for PRT network. In this paper, the concept of PRT and general optimal routing methods are reviewed. And we suggest the optimal routing method for city-wide PRT network with multi-vehicles and stations, junctions and directional arcs. Futher research directions for PRT routing are presented.