• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2353-2362
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• 2015

In this paper, we employ the single channel full duplex radio for wireless local area network (WLAN) systems, and design digital interference cancellers using adaptive signal processing. When the full duplex scheme is used for WLAN systems with multiple transmit and receive antennas, some interference is caused through the feedback of transmit signals from multiple antennas. To remove the feedback interference, we derive the least mean square (LMS), normalized LMS (NLMS), and recursive least squares (RLS) algorithms based on adaptive signal processing techniques. In addition, we analyze the theoretical convergence of the proposed LMS and RLS methods. The channel capacity of full duplex radios increases by two times than that of half duplex radios, when the packet error rate (PER) performances for the two systems are identical. Through numerical simulations in WLAN systems, it is shown that the full duplex method with the proposed interference cancellers has a similar PER performance with the conventional half duplex transmission scheme.

• Journal of Broadcast Engineering
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• v.5 no.2
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• pp.211-219
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• 2000

The IBAC DAB system was interfered by existing FM broadcasting signal as was used guardband within existing FM broadcasting. The FM interference signals are very important parameter in performance evaluation of IBAC DAB system. We got the characteristic of FM PSD in according to instantaneous change and average characteristic of FM broadcasting signal in according to characteristic of FM channel. In this paper, based on proposed IBAC DAB system, we analyze effects of FM interference for occupied bandwidth and performance of IBAC DAB modeling various FM interference signals with sum of sinusoid function using C language, suggest FM interference ratio that can maintain performance. We was know that IBAC DAB system have a great performance variation in according to average characteristic of FM PSD by simulation results, also, FM interference ration that can maintain performance of system is 10dB.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.3
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• pp.246-252
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• 2013

This paper presents method to suppress signal interference by using the filter in the RF output stage of the radiation equipment as a way to avoid interference between the RF(Radio Frequency) equipment mounted on aircraft. Especially filter design to suppress harmonics of the radiation equipment and testing method to verify the filter's performance is presented. Filter was installed at RF output stage of U/VHF radio in order to prevent interference between U/VHF(Ultra/Very High Frequency) radio and data link system. Filter design and testing method in this paper will be able to give help in the design of aircraft equipments as a tool that can be used to establish measures for problem of interference in the aircraft.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4A
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• pp.291-301
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• 2009

In this paper, the effect of ISI(Inter-Symbol Interference) and ICI(Inter-Carrier Interference) due to time difference of arrival on OFDMA-based mobile multi-hop relay (MMR) systems is analyzed. Analyses are performed for the ISI caused by the previous OFDMA symbol transmitted from neighboring macro or relay cell as well as the ISI caused by the next OFDMA symbol transmitted from neighboring macro or relay cell. Then, an effective SINR(Signal to Interference plus Noise Ratio) estimation method and a path selection method considering time difference of arrival are proposed to minimize the effect of ISI and ICI. It is shown by simulation that the performance degradation caused by time difference of arrival can be significantly mitigated when the proposed path selection method is applied to the uplink of OFDMA-based MMR systems.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.11 no.1
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• pp.10-15
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• 2012

Ultra wideband (UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geo-location, and other applications. The energy of UWB signal is extremely spread from near DC (Direct Current) to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional wireless systems sharing the frequency bands such as broadcasting system. This paper experimentally evaluates the interference from two kinds of UWB sources, namely an orthogonal frequency division multiplex UWB source and an impulse radio UWB source, to a broadcasting transmission system. The S/N ratio degradation of broadcasting system is presented. From these experimental results, we show that in all practical cases UWB system can be coexisted 35m distance in-band broadcasting network.

• ETRI Journal
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• v.32 no.6
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• pp.921-931
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• 2010

It has been shown that the principal subspace-based multichannel Wiener filter (MWF) provides better performance than the conventional MWF for suppressing interference in the case of a single target source. It can efficiently estimate the target speech component in the principal subspace which estimates the acoustic transfer function up to a scaling factor. However, as the input signal-to-interference ratio (SIR) becomes lower, larger errors are incurred in the estimation of the acoustic transfer function by the principal subspace method, degrading the performance in interference suppression. In order to alleviate this problem, a principal subspace modification method was proposed in previous work. The principal subspace modification reduces the estimation error of the acoustic transfer function vector at low SIRs. In this work, a frequency-band dependent interpolation technique is further employed for the principal subspace modification. The speech recognition test is also conducted using the Sphinx-4 system and demonstrates the practical usefulness of the proposed method as a front processing for the speech recognizer in a distant-talking and interferer-present environment.

• Journal of electromagnetic engineering and science
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• v.9 no.2
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• pp.61-65
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• 2009

Successive interference cancellation(SIC) for the uplink of MC-CDMA mobile communications systems is an effective method to improve performance. We propose a successive interference cancellation(SIC) technique for the uplink of MC-CDMA mobile systems with multiple receive antennas. The destination uses optimum combining(OC) to combine the signals from an OFDM Demodulator with multiple receiving antennas, and applies SIC processing to the combined signals. Achieved interference cancellation order is depends on the signal to interference-plus-noise ratio (SINR) at the output of the optimum combiner. Monte-Carlo simulations are employed to verify the proposed technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.10
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• pp.956-964
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• 2012

An opportunistic interference alignment based on dynamic cell selection is proposed. Since the proposed method can switch the desired signal space and the interference space of received signals, an additional selective diversity gain increases. The performance analysis using probabilistic models provides a mathematical expression for the sum-rate capacity. Simulation examples show that the proposed method achieves the higher sum-rate capacity than that of the conventional opportunistic interference alignment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1714-1721
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• 2000

In the mobile communication using DS-CDMA systems the problem of multiple user interference which reduce the performance is generated by multiple user access. In this paper to solve this problem we proposed the direct decision blind adaptive receiver with knowledge of only the desired user's spreading sequence. Simulation result present that the total user's power has equal gain The gain of signal to interference ratio for the proposed blind DD-LMS receiver has about 6[dB] than conventional receiver at additive white Gaussian noise and large gain at multipath channels. And when interference user's power has more large gain than desired user's power the gain of SIR for the proposed receiver has large value. And simulation result of bit error rate present that DD-LMS receiver has higher performance than LCCMA receiver. Thus the proposed blind DD-LMS receiver has robustness against interference of high power user and multipath channels.

• Journal of electromagnetic engineering and science
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• v.6 no.1
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• pp.76-81
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• 2006

Ultra wideband(UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geo-location, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional wireless systems sharing the frequency bands such as Broadcasting system. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a orthogonal frequency division Multiplex UWB source and an impulse radio UWB source, to a Broadcasting transmission system. The receive power degradations of broadcasting system are presented. From these experimental results, we show that in all practical cases UWB system can coexist 35 m distance in-band broadcasting network.