• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.16-19
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• 2014

In this paper, the beacon signals of WiFi doppler frequency detection based WiFi-AP was designed with the subcarrier between a transmitter and a receiver of WLAN(wireless LAN). We can use such signals to identify human moving as an antenna array and tracking of RF beam. This wireless security services with the combination of WiFi doppler frequency and adaptive beacon time signal was proposed for wireless detection and motion based services.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.65-74
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• 2002

A three dimension(3D) link analysis is peformed considering multipath effects caused by a reflected signal and the difference angle between the antenna bore-sight and Line-Of-Sight(LOS). In addition, a direction of a receive antenna is determined for a receiver to get maximum signal strength in a telemetry situation. For a fixed receive antenna, the angle is determined to maximize the average Carrier to Noise Ratio(CNR) over the interested part of a trajectory. For a tracking antenna, the angle at every position is selected to give maximum CNR or to direct the boresight to the flying projectile.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.761-770
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• 1997

Narrowband signals can be treated like a single tone interference at the receiver which demodulates wideband signals spectrum overlaid at the same frequency band. In this paper, the single tone interference is effectively suppressed by the use of a multicarrier DPSK direct-sequence(DS) spread spectrum(SS) with maximal-ratio(MR) combining instead of notch filter, which is hard to implement. A noncoherent DPSK system is considered because it is more realizable and does not require any complicate phase tracking, compared with a single carrier system subject to a constraint system bandwidth, and their performance comparisons are validated through simulation. We also propose a suboptimal-ratio(SR) combining which yields uniform and tight low bound on the performance of the MR combining, and then system parameters re optimized by theoretically evaluating the low bound, since an exact analysis appears intractable.

• Journal of Korea Multimedia Society
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• v.19 no.8
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• pp.1460-1465
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• 2016

In this paper, we propose an energy efficient and multimedia traffic friendly MAC protocol (EEMF-MAC) that controls sender's wakeup period based on the data packet's transmission urgency and the receiver's wakeup periods based on the received data packet traffic loads. The protocol is useful for applications such as object tracking, real time data gathering, in which priority-based packet transmission is required. The basic idea of EEMF-MAC is that it uses the priority concept with transmission urgency of sender's data packet to reduce the transmission delay of the urgent data and it also uses duty cycling technique in order to achieve energy efficiency. EEMF-MAC showed a better performance in energy efficiency and packet transmission delay compared to existing protocols, RI-MAC and EE-RI-MAC.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.149-152
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• 1998

A synchronization is very important element not only wire communication but also wireless communication. A synchronous oscillator(SO) is a network which synchronizes, tracks, filter, amplifies and divides (if necessary) in a single process. The coherent phase synchronous oscillator(CPSO) is created by adding two external loops to the SO. The CPSO ratains all virtues of a SO while providing coherency throughout the tracking range. This paper has applied a clock recovery of GPS signal using CPSO.

• Journal of Advanced Navigation Technology
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• v.16 no.1
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• pp.16-26
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• 2012

Pseudolites are ground-based transmitters that can be configured to emit GPS-like signals for enhancing the GPS by providing increased accuracy, integrity, and availability. However, a pseudolite (PL) can interfere with GPS satellite signals while it is transmitting or cause saturation to automatic gain control circuit. To solve these problems pulsing scheme is used, which transmits PL signal during a short period of time. In this paper the effect of the number of PL and pulsing scheme on the software GPS L1 and L2C signal acquisition performance is studied for the three pulsing schemes such as static pulsing, sweep pulsing, and pseudo random pulsing. For GPS L1 signal, static pulsing shows the best signal acquisition and tracking performance with one PL, and random pulsing shows the best performance with more than or equal to two PLs. For GPS L2C signal, all three pulsing schemes show the similar signal acquisition and tracking performance, but static pulsing shows a little better performance. For GPS L1 and L2C signals, software GPS receivers can do positioning with up to three PLs.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2601-2610
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• 2013

The main limiting factors of Precise Point Positioning(PPP) accuracy are errors in broadcast satellite orbits, clock errors, and the others, which are receiver-dependent errors(ionospheric, tropospheric refraction, multipath, and tides, etc.). Therefore, to facilitate high precision PPP, precise orbits/clocks corrections, the receiver-dependent errors corrections have to apply to multi frequency GNSS measurements for an ionosphere free combination and integer ambiguity resolution in real-time. Currently, there are many Analysis Centers, which offer the precise corrections stream computed in real-time using the global or regional GNSS tracking network. The goles of this research considered performances of the real-time static PPP with using RTCM corrections from NTRIP casters. For this, the corrections streams of Analysis Centers received via NTRIP does apply to GNSS data of check points individually, as well as jointly, in accordance with various session lengths. After that, have compared the PPP results from the corrections streams with each other, and with Standard Point Positioning(SPP) results.

• Journal of Korea Multimedia Society
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• v.16 no.6
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• pp.746-755
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• 2013

This paper presents a three dimensional bilateral filter detecting target trajectory, extracting spatial target information using two dimensional bilateral filter and temporal target information using one dimensional bilateral filter. In order to discriminate edge pixel with flat background and target region spatially and temporally, spatial and temporal variance are used for an image and temporal profile. With this procedure, background and background profile are predicted without original target through two dimensional and one dimensional bilateral filter. Finally, using spatially predicted background and temporally predicted background profile, small target can be detected. For comparison of existing target detection methods and the proposed method, the receiver operating characteristics (ROC) is used in experimental results. Experimental results show that the proposed method has superior target detection rate and lower false alarm rate.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.7
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• pp.767-773
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• 2014

The carrier-to-noise power ratio is a key parameter for determining the reliability of PVT (Position, Velocity, and Time) solutions which are obtained by a GNSS (Global Navigation Satellite System) receiver. It is also used for locking a tracking loop, deciding the re-acquisition process, and processing advanced navigation in the receiver subsystem. The representative carrier-to-noise power ratio estimation schemes are the narrowband-wideband power ratio method (NW), the MM (Moment Method), and Beaulieu's method (BL). The NW scheme is the most classical one for commercial GNSS receivers. It is often used as an authoritative benchmark for assessing carrier-to-noise power estimation schemes. The MM scheme is the least biased solution among them, and the BL scheme is a simpler scheme than the MM scheme. This paper focuses on the less biased estimation with low complexity when the residual phase noise remains, then proposes a novel carrier-to-noise power ratio estimation scheme with low complexity for GNSS receivers. The asymptotic bias of the proposed scheme is derived and compared with others, and the simulation results demonstrate that the complexity of the proposed scheme is lowest among them, while the estimation performance of the proposed scheme is similar to those of the BL and MM schemes in normal and high gained reception environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9C
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• pp.729-734
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• 2010

In the initial stage of the communications between a base station and a satellite transponder, the base station transmits the frequency-sweeping un-modulated up-link carrier within a certain frequency range to acquire the doppler frequency shift and signal power between the base station and the satellite in orbital flight. The satellite transponder acquires and tracks the carrier in order to initialize the communication. To control such initialization process, the satellite receiver should analyze the input carrier signal in various ways. This paper presents an SNR estimation algorithm to control the initialization process. The proposed algorithm converts the input signal into the baseband polar coordinate representation and estimates the SNR via the statistics of the angular signal components as well as the status parameters to control the receiver. The Monte-Carlo simulations shows the validity of the estimation proposed.