• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.8
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• pp.37-44
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• 2004

This paper describes a new GaAs-based surface-micromachined microstrip line supported by dielectric post and air-gapped signal line with ground metal. This new type of dielectric-supported air-gapped microstripline(DAML) structure is developed using surface micromachining techniques to provide easy means of airbridge connection between the signal lines and to archive low losses at millimeter-wave frequency band with wide impedance range. Each DAMLs with the length of 5 mm are fabricated and the measured characteristics are compared with those of the conventional microstrip transmission line. These transmission lines are composed of 10 ${\mu}{\textrm}{m}$ height of signal line, post size of 10 ${\mu}{\textrm}{m}$ ${\times}$ 10 ${\mu}{\textrm}{m}$ and post height of 9 ${\mu}{\textrm}{m}$. By elevating the signal lines from the substrate using the micromachining technology, the substrate dielectric loss can be reduced Compared with of the conventional microstrip transmission line showing 7.5 dB/cm loss at 50 GHz, the loss can be reduced to 1.1 dB/cm loss at 50 GHz.

• The KIPS Transactions:PartC
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• v.13C no.5 s.108
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• pp.635-640
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• 2006

The Snoop in the BS (Base Station) performs a local retransmission over wired-wireless networks to recover packet loss quickly. However, when the MH (Mobile Host) leaves the reception range of the signal, the local retransmission causes performance to degrade. In this paper, we minimize the packet loss and local retransmission caused by the unreachability from BS to MH to improve network performance. To do this, we suggest to add RSS(Received Signal Strengths) flag bit in ACK packet of MH. By using this flag bit, the BS decides whether it retransmits or not to minimize packet loss. The result of the simulation by ns-2 shows a big improvement of performance in the networks.

• The Journal of the Acoustical Society of Korea
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• v.19 no.8
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• pp.12-21
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• 2000

In this paper, we propose a novel hearing aid algorithm for sensorinural hearing loss restoration with multi-channel(band) dynamic range compression and psychoacoustics. In this way, we can present a normal perception condition to the impaired listener. The proposed algorithm make loudness scaling function achieve proper loudness level, and analysis masking property for the signal will be perceived to impaired listener, and then, restore normal spectral contrast using SMR(signal-to-masking ratio) defined by distance between the level of each frequency and masking threshold.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.359-364
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• 2006

Interference can seriously degrade the performance of GPS receiver because GPS signal has extremely low power at earth surface. This paper presents a Narrowband Interference Excision Filter (NIEF) in frequency domain that removes narrowband interferences with small signal loss. A NIEF transforms the received GPS signals with interferences into the frequency domain with FFT and then compute statistics such as mean and standard deviation to determine an excision threshold. All spectrums exceeding the threshold are removed and the remaining spectrums are restored by IFFT. A NIEF effectively can remove various and strong interferences with a simple structure. However, the signal power loss is unavoidable during FFT and IFFT. Besides the hamming window and overlap technique, a threshold-whitening technique and an adaptive detection threshold are adopted to effectively reduce the signal power loss. The performance of implemented NIEF is evaluated using real signals obtained by 12 bit GPS signal acquisition board. The output of NIEF is fed into the Software Defined Receiver to evaluate the acquisition and tracking performance. Experimental results shows that many types of interference such as single-tone CWI, AM, FM, swept CWI and multi-tones CWI are effectively mitigated with small signal power loss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.8 s.99
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• pp.790-796
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• 2005

In order to accomplish a wireless communication of capsule endoscopy, an environment study in the human body and receiving antenna design have been performed. The proposed antenna is the loop antenna designed to minimize the propagation loss in multi-loss layer such as the human body and utilize the magnetic field. Considering the propagation loss in the human body, the frequency range is from 400 MHz to 500 MHz. Acorrrding to the FCC regulations, the permittivity and conductivity for each human tissue were extracted. We set up an equivalent model and make an aqueous solution which is replaced with the human body. Due to movement of capsule in the human body which propagation loss is extremly severe, an array antenna is required. Irrespective of the location of transmission antenna transmitting a signal of 1 mW, we confirme what it is possible for the enough signal detection as the average signal level of array antenna is -60 dBm.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.3
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• pp.194-198
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• 2011

In this paper, we obtained the path loss characteristics in the 850 MHz for Russia area by using the free space path loss model and Okumura-Hata path loss model. In order to extract the additional path loss model parameter from the new Russian regional properties, the mean square error technique is used to obtain the correction factor. According to the obtained correction factor, the differences for the free space and Hata path loss model are 17, 6 dB in the 5 ~ 10 Km, 28, 14 dB in the 10 ~ 15 Km, and 35, 18 dB in the 15 ~ 20 Km. By applying the correction factors, the appropriate partial path loss models for the measured Russain area are proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9A
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• pp.1306-1313
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• 1999

In this paper, we propose the signal strength path loss model (modified Hata path loss Model) and the signal strength distribution model (log-normal distribution) for the cell design of the land mobile communication system. We applied the measured experimental data at Soosungdon and Sanjuckdong in Daeku, to this model and calculate the fraction of total area above threshold.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.94-100
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• 2012

Radio interference has been occurring in mobile communication services on the southern seashore in Korea. Monitoring the radio interference signal revealed that the main reason for the radio interference was a radio ducting signal coming from the seaside of Japan. In this paper, we have analyzed the effect of interference on WiMAX service using a 2.5 GHz frequency band between Korea and Japan. We focus on the interference scenario from base station to base station and we use the Minimum Coupling Loss (MCL) method for interference analysis and the Advanced Propagation Model (APM) for calculating the propagation loss in ducts. The propagation model is also compared with experimental measurement data. We confirm that the interfering signal strength depends on the antenna height and this result can be applied to deployment planning for each system with an interference impact acceptable to both parties.

• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.687-689
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• 2010

In this paper, the equalization for frequency slope of path loss in Multi-Band(MB) OFDM UWB is proposed. The path loss of a signal is proportionate to the square of the signal's frequency. So, the received signal amplitudes of OFDM subcarrier can be different up to 3dB when MB-OFDM occupies bandwidth over 1.5GHz. The differences of subcarrier-amplitudes make an effective of 0.3 bit reduction of soft decision bits of viterbi decoder, and when the effective of 0.3 bit reduction can cause 0.5dB SNR degradation. This paper proposes two modem architectures which compensate for the degraded subcarrier by multiplying the reciprocal of degraded values in analog or digital domain. It is shown that, for the proposed architecture applied to MB-OFDM UWB, the performance improvements up to 0.5dB can be obtained over the conventional uncompensated receiver architecture.

• ETRI Journal
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• v.41 no.5
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• pp.637-647
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• 2019

Separating highly correlated users can reduce the loss caused by spatial correlation (SC) in multiuser multiple-input multiple-output (MU-MIMO) systems. However, few accurate analyses of the loss caused by SC have been conducted. In this study, we define signal-to-interference-plus-noise ratio (SINR) loss to characterize it in multiuser multiple-input single-output (MU-MISO) systems, and use coefficient of correlation (CoC) to describe the SC between users. A formula is deduced to show the accurate relation between SINR loss and CoC. Based on this relation, we propose a user selection method that utilizes CoC to minimize the average SINR loss of users in massive MU-MISO systems. Simulation results verify the correctness of the relation and show that the proposed user selection method is very effective at reducing the loss caused by SC in massive MU-MISO systems.