• ETRI Journal
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• v.32 no.1
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• pp.44-52
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• 2010

Ultra-wideband (UWB) systems have witnessed a debate over whether they may cause interference to other existing and future narrowband systems sharing their band of operation. The detect and avoid (DAA) mechanism was developed as a solution to reduce interference to narrowband systems in order to ease regulatory concerns. It works by adaptively reducing the transmitted power at the overlapping bands upon detecting an active narrowband link. However, employing DAA degrades the performance of UWB transmissions. In this paper, we present the Korean UWB regulations as an example of regulations that require DAA in certain bands. We investigate DAA's impact on performance and propose a method to mitigate it, which provides UWB with the more efficient support of the DAA mechanism and enables it to avoid a larger number of narrowband users while sustaining the data rate. Results show significant improvement in performance with the application of our technique compared to conventional performance.

• ETRI Journal
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• v.30 no.1
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• pp.161-163
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• 2008

An M-ary bi-orthogonal modulation scheme for ultra-wideband (UWB) systems capable of narrowband interference (NBI) suppression is proposed in this letter. We utilize a set of bi-orthogonal pulse series to achieve NBI suppression. Through analysis and simulation, we verify that the proposed scheme can suppress NBIs effectively.

• ETRI Journal
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• v.29 no.3
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• pp.322-328
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• 2007

We propose a direct-sequence pulse-amplitude modulation (DS-PAM) ultra-wideband (UWB) system which employs a non-linear chirp waveform instead of the conventional Gaussian monocycle in this paper. In the approved frequency for UWB, there exist myriad narrowband interferers. Specifically, we focus on the mutual interference between UWB systems and 802.11a WLAN. This paper offers a method to suppress this in-band narrowband interference by introducing a kind of non-linear chirp waveform. Using the proposed non-linear chirp waveform, the effects of one or more narrowband interference sources with different frequencies can be suppressed. System performance of UWB systems in the narrowband interference environment can be improved. Computer simulations with additive white Gaussian noise successfully demonstrate an increase in performance with the proposed system as compared to traditional linear chirp systems.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.745-751
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• 2010

In this paper, the proposed a narrowband interference cancellation techniques for the frequence sharing of Ultra wideband Impulse Radio communication system and narrowband communication system. In this system, the narrowband communication signals can cause intolerant interferences to Impulse Radio signals. In this paper, Ultra wideband Impulse Radio system have been analyzed in AWGN, MAI and NI(Narrowband Interference) environment. Also, performance improvement has been obtained by adopting an adaptive notch filtering scheme using Complex Filter Bank and CCI canceller. The results show that there is a substantial enhancement in performance by employing the adaptive notch filtering and/or CCI canceller.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.1
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• pp.28-36
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• 2020

Due to the continued demand for high-definition video, video compression technology is steadily developing and the High Efficiency Video Coding standard was established in 2013. However, despite the development of this compression technology, it is very difficult to smoothly transmit VGA-level videos in Ultra-narrowband environments. In this paper, the target information preprocessing algorithm is presented for smooth transmission of target images moving in forest or open-terrain in Ultra-narrowband environment. In addition, for algorithm verification, the target information preprocessing algorithm was simulated and the simulated results were compared with the video compression result without the algorithm being applied.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.603-614
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• 2005

In this paper, digital ultra-narrowband Walky-Talky using direct conversion method for CQPSK modulation scheme is implemented with satisfying the requirements of APCO P25. RF transceiver design and implementation scheme that minimize the influence of DC-offset and AC-coupling at ultra-narrowband is proposed. This scheme also minimizes the influence of nonlinear characteristic at power amplifier fir CQPSK modulation method. Test results of full system including DSP module and direct conversion RF transceiver show that FCC emission mask at 36.8 dBm PEP meets the standard requirements. The characteristic of receiver AGC by PWM control signal is linear at 40 dB dynamic range and voice communication at input power level of -116 dBm is successful. Also it is verified that the performance of BER versus frequency offset and versus SNR meets the standard requirements.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.374-385
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• 2003

The growing interest towards ultra-wideband (UWB) communications stems from its unique features such as baseband operation, ample multipath diversity, and the potential of enhanced user capacity. But since UWB has to overlay existing narrowband systems, multiple access has to be achieved in the presence of narrowband interference (NBI). However, existing baseband spreading codes for UWB multiple access are not flexible in handling NBI. In this paper, we introduce two novel spreading codes that not only enable baseband UWB multiple access, but also facilitate flexible NBI cancellation. We construct our codes using a single carrier or multiple carriers (SC or MC), which can be implemented with standard discrete-cosine transform (DCT) circuits. With our SC/MC codes, NBI can be avoided by simply nulling undesired digital carriers. Being digital, these SC/MC codes give rise to multiband UWB systems, without invoking analog carriers. In addition, our SC/MC codes enable full multipath diversity, and maximum coding gains. Equally attractive is their capability to reduce the number of interfering users, with simple matched filter operations. Comprehensive simulations are also carried out to corroborate our analysis.

• Journal of Communications and Networks
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• v.10 no.3
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• pp.297-300
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• 2008

The capacity of ultra-wideband (UWB) systems in presence of narrowband interference (NBI) is studied. By appropriately modifying the Shannon capacity formula, an analytical expression for the capacity of M-ary pulse position modulation (PPM) signals in the presence of NBI is obtained. Performance evaluation results for the capacity of such signals as a function of the NBI carrier frequency and power are also presented.

• ETRI Journal
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• v.29 no.4
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• pp.521-523
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• 2007

In this letter, we analyze an ultra-wideband ranging system based on non-linear chirp waveforms with the ability of narrowband interference suppression. A number of non-linear chirp waveforms are proposed and evaluated by simulation. The results verify that the proposed schemes can suppress the Narrowband interference to a certain degree.

• Journal of electromagnetic engineering and science
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• v.4 no.2
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• pp.72-78
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• 2004

In this paper, we evaluate the performance of the digital modulation schemes described in the APCO Project 25 FDMA specifications which can be used for applying the ultra-narrowband technology to the current domestic simple two-way radio systems, and discuss difficulties in the DSP implementation of the systems. We analyze the effect on the systems' BER performance of receiver non-matched filter and frequency-offset between the transmitter and receiver oscillators. And we present a frequency offset compensation method for improving the system performance. The results of performance analysis showed that the CQPSK of APCO Project 25 using non-matched filter degraded the BER by 0.5～1.0 ㏈ comparing with PI/4 DQPSK using matched filter. In the event of 2 % frequency offset, about 1 ㏈ performance loss was produced at the BER of $$10^{-3}TEX>. With the frequency-offset compensation method implemented in the systems using phase recovery scheme of PSK synchronization detection, the performance degradation of about 1.0 ㏈ was occurred at the BER of $$10^{-3}TEX> for 10 % of frequency offset. The proposed method can be used for the improvement of system performance.