• ETRI Journal
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• v.38 no.1
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• pp.30-40
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• 2016

Co-channel interference between macro-femtocell networks is an unresolved problem, due to the frequency reuse phenomenon. To mitigate such interference, a secondary femtocell must acquire channel-state knowledge about a co-channel macrocell user and accordingly condition the maximum transmit power of femtocell user. This paper proposes a pilot-based spectrum sensing (PSS) algorithm for overlaid femtocell networks to sense the presence of a macrocell user over a channel of interest. The PSS algorithm senses the pilot tones in the received signal through the power level and the correlation metric comparisons between the received signal and the local reference pilots. On ensuring the existence of a co-channel macrocell user, the maximum transmit power of the corresponding femtocell user is optimized so as to avoid interference. Time and frequency offsets are carefully handled in our proposal. Simulation results show that the PSS algorithm outperforms existing sensing techniques, even at poor received signal quality. It requires less sensing time and provides better detection probability over existing techniques.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.6
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• pp.119-125
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• 2008

In this paper, we proposed the modeling of UHF frequency environment in a random mountainous area with line of sight. A transmitting station is defined as wanted transmitter(Wr) and a receiving station is defined as victim receiver(Vr). These set up victim link. A interference transmitter(It) and wanted receiver(Wr) set up interference link. We compared measured data at random mountainous area with data of the result using spectrum engineering advanced monte calo analysis tool(SEAMCAT), interference simulation based on the monte-carlo method. The desired received signal strength(dRSS) of SEAMCAT had the calculated error of 70% from the measured received signal strength because there was a topographical effect. Therefore, the effect of diffraction interference was included to lessen the power of transmitter in the proposed simulation. The cause of received power error are cable loss and errors of a measuring instrument. The proposed simulation modeling in UHF frequency environment expect that is the useful study on interference analysis and reassignment of broadcasting frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.409-416
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• 2007

In cellular orthogonal frequency division multiplexing (OFDM) networks, co-channel interference (CCI) leads to severe degradation in the BER performance. To solve this problem, maximum-likelihood estimation (MLE) CCI cancellation scheme has been proposed in the literature. MLE CCI cancellation scheme generates weighted replicas of the transmitted signals where weights represent the estimated channel transfer functions. The replica with the smallest Euclidean distance from the received signal is selected and data are detected. When the received power of the desired and interference signals are nearly the same, the BER performance is degraded. In this paper, we propose a closed-loop power control (PC) scheme capable of detecting the equal received power situation at the mobile station (MS) receiver by using the newly introduced parameter power ratio (PR). When this situation is detected, the MS sends a feedback to the desired base station (BS) which boosts the transmission power in the next frame. At cell edge where signal to interferer ratio (SIR) is considered to have average value between -5 dB and 10 dB, computer simulations show that the proposed CCI cancellation scheme has a gain of 7 dB at 28 Km/h.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8C
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• pp.771-778
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• 2003

A mobile station in a cell receives interference signals from neighboring base stations. Due to the interference signals, the forward link capacity of the cellular system is reduced. Pilot signal received from a neighboring base station is one of the interference signals. Since the pilot signal is a known signal for all the mobile stations, the pilot interference signal can be cancelled by interference cancellation techniques. In this paper, we propose a demodulator with interference canceller to cancel pilot interference signals received from neighboring base stations. The simulation results show that Eb/No value to obtain BER = 10-2 is lowered by 3㏈ in the propose demodulator.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.4
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• pp.456-464
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• 2013

Passive sonar in submarine can detect the target in long range and can attack using it. There are many noises which can be received at passive sonar of submarine. When noise received in the sonar it make diverse interference pattern depend on the ocean ambient and movement scenario. Interference pattern can be explained by theory of waveguide invariant. In this paper, analyze the interference pattern according to the relative motions of surface ship and submarine. And analyze the occurrence reason of 2 kinds of interference patterns those are usually display on the submarine console. The results show that if relative speed of submarine and target increase then gradient of interference pattern will increase. And closest point approach of submarine and target decrease then gradient of interference pattern will increase. Bathtube pattern usually appear when target pass though close to submarine and Pinetree pattern appear target pass though above of submarine.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.920-926
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• 2005

In this paper, we analyzed the effect by building materials in the case of floor cell design and the penetration loss value by material in each frequency bands through an experiment in high building. Specially, the penetration loss measured about interference signal that is received to direct path, interference signal and flowed in slant path. Also, we analyzed system performance according to path of standard Cell received interference signal.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.4
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• pp.165-173
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• 2019

In this paper, we apply a discrete wavelet packet transform (DWPT) to reduce the influence of interference in global positioning system (GPS) signals and compare the interference mitigation performance of various wavelets. By applying DWPT to the received signal, we can gradually divide the received signal band into low-pass and high-pass bands. After calculating the average power for the separate bands, we can determine whether there is interference by comparing the value with the given threshold. For a band that includes interference, we can reconstruct the whole band signal using inverse DWPT (IDWPT) after applying a nulling method that sets all of the wavelet coefficients to 0. The reconstructed signals are correlated with the pseudorandom noise (PRN) codes to acquire GPS signals. The performance evaluation is based on the number of satellite signals whose peak ratio (defined as the ratio of the first and second correlation peak values in the acquisition stage) exceeds the threshold. In this paper, we compare and evaluate the performance of 6 wavelets including Haar, Daubechies, Symlets, Coiflets, Biorthogonal Splines, and Discrete Meyer.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.4
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• pp.319-325
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• 2020

In order to propose new satellite navigation signals, it is essential to analyze the increased level of interference effect that the existing signals suffer. In this paper, a method for estimating the power density of the interference signals on GPS signals is proposed before and after the additional transmission of the KPS signals in the L1, L2 and L5 bands. For estimation, we assume the number of visible satellites observed over the Korean peninsular and the minimum received power of the satellite navigation signals. The comparison of the estimated values shows that the power density of the interfering signal increases by up to 1.37 dB due to the introduction of KPS, but this leads to an increase in interference plus noise power density below 0.47 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.416-425
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• 2002

In this Paper, It is analysed 5 GHz frequency characteristics that carry out interference experimental under the indoor environments for understanding propagation interference between existing 5 GHz band wireless communication system and 5 GHz band wireless LAN system. The interference signal which was generated by signal generator injected to 5 GHz Wireless LAN communication system measured interference characteristics and This radio propagation main interference factors were classified received power level separation by interference source frequency and interference source frequency pulse period & width separation. It is measured transmission rate according to variable data and packet size for conforming the quality of 5 GHz band wireless LAN system. We measured the packet data loss rate and power level of received signal and analyzed its frequency characteristics effected by interference signal.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.151-155
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• 2002

In this paper, interference effects between NGSO and HAPS analyze into two cases. One is HAPS interference effect into NGSO, another is NGSO interference effect into HAPS. First, same case of number of users for LEO and HAPS interference received to LEO mobile station are over the -8.82dB. But in case of 1/10 and 1/100, I/N values are lowest 16.9dB and -20.3dB respectively. In case of interference received to HPAS mobile station, as LEO is 87$^{\circ}$, if the HAPS and LEO users is same, interference criterion over the 2200 users. but in the case of 1/10 and 1/100 of LEO is HAPS users, we don't know over the interference criterion. In accordance with, for reduce to effects of interference important suitable establishment of transmission power, number of users and cell radius of two system.