• International journal of advanced smart convergence
• /
• v.9 no.4
• /
• pp.156-166
• /
• 2020

In this paper, to improve spectral efficiency and mitigate interference in coordinated millimeter-wave systems, we proposes an optimal user group and beam selection scheme. The proposed scheme improves spectral efficiency by mitigating intra- and inter-cell interferences (ICI). By examining the effective channel capacity for all possible user combinations, user combinations and beams with minimized ICI can be selected. However, implementing this in a dense environment of cells and users requires highly complex computational abilities, which we have investigated applying multiclass classifiers based on machine learning. Compared with the conventional scheme, the numerical results show that our proposed scheme can achieve near-optimal performance, making it an attractive option for these systems.

• International Journal of Internet, Broadcasting and Communication
• /
• v.12 no.4
• /
• pp.18-25
• /
• 2020

In the fifth generation (5G) and beyond 5G (B5G) mobile communication, non-orthogonal multiple access (NOMA) has attracted great attention due to higher spectral efficiency and massive connectivity. We investigate the impacts of the channel estimation errors on the bit-error rate (BER) of NOMA, especially with the single-user decoding (SUD) receiver, which does not perform successive interference cancellation (SIC), in contrast to the conventional SIC NOMA scheme. First, an analytical expression of the BER for SUD NOMA with channel estimation errors is derived. Then, it is demonstrated that the BER performance degrades severely up to the power allocation less than about 20%. Additionally, we show that for the fixed power allocation of 10% in such power allocation range, the signal-to-noise (SNR) loss owing to channel estimation errors is about 5 dB. As a consequence, the channel estimation error should be considered for the design of the SUD NOMA scheme.

• Proceedings of the IEEK Conference
• /
• 2002.07a
• /
• pp.405-408
• /
• 2002

Because of superior division among sub-channels, DWT MC-CDMA is less interference with neighborhood channel. In our newly proposed multi-carrier CDMA data transmission method, lIR CMFB filter banks sharply divide sub-bands and reduces spectral overlaps among neighboring sub-channels. In experiment result, proposed filter is better ability of sub-band division than FIR filter. Since the proposed cosine modulated filter banks lIR filter having wavelet property is designed to response sharp transition band, the ISI and ICI between neighboring sub-channels can be effectively reduced. And robustness about narrow band interference of CMFB IIR MC-CDMA almost same FIR DWT MC-CDMA.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.12
• /
• pp.9-15
• /
• 1994

In this paper, the linearized power amplifier using digital adaptive predistorter is implemented in order to restrict spectral spreading and adjacent channel interference. The linearized systems is composed of a DSP56001 processor that executes predistortion in baseband. 90.deg. phase shifter, power splitter/combiner, quadrature modulator/demodulator of 360MHz band, and nonlinear amplifier. A ${\pi}$/4-shift QPSK is used to modulate digital random signals. As the quantized power of baseband signal and the output of amplifier are fed to the predistorter, and predistorting values are calculated using an adaptive algorithm. In the experiment, a peak to sidelobe ratio of the linearized amplifier is improved up to 15dB in comparison with conventional nonlinear amplifier, which means that the distortion of transmitted signal is decreased and adjacent channel interference was reduced.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.34D no.7
• /
• pp.79-87
• /
• 1997

Untill now, the most well-known cofiguration for waveguide grating router(WGR) is composed of radiative star couplers and arrayed waveguide grating(AWG), which usually suffer form the rdiation loss of around 3dB or more. Therefore, te improved design of WGRs is needed to reduce the loss. In ths paper, we propose a novel WGR composed of multimode interference couplers which have good unifiormity, fabrication tolerance, and very low excess loss, and suggest the efficient algorithm to find the proper path length differences of AWG for given channel spacing and channel assignment to each output prot. The simulated spectral responses of the proposed WGR using the finite difference beam propagation method (BPM) show that the excess loss is less than 0.3dB and the crosstalk less than -25dB in case of 4x4 WGR, and the excess loss less than 0.4dB and the crosstalk less than -25dB in case of 8x8 WGR for all the channel wavelengths.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.8 no.4
• /
• pp.129-133
• /
• 2012

Coordinated multi-point transmission (CoMP) is a candidate technique for next generation cellular communications systems. One of the primary elements discussed in LTE-Advanced technology is CoMP, which can improve cell edge user data rate as well as spectral efficiency due to multiple input multiple output - orthogonal frequency division multiplex (MIMO-OFDM). We consider a system with multiple cells in which base stations coordinate with each other by sharing user channel state information (CSI), which mitigates inter cell interference (ICI), especially for users located at the cell edge. We introduce a new user scheduling method of ICI cancellation and the loss reduction of effective channel gain during the beamforming process, the proposed method improves the system sum rate, when compared to the conventional method by an average of 0.55bps/Hz in different number of total users per cell. It also outperforms the conventional method by approximately 0.38bps/Hz using different SNRs.

• Proceedings of the Korean Information Science Society Conference
• /
• 2003.04a
• /
• pp.788-790
• /
• 2003

본 논문은 멀티미디어를 위한 초고속 통신망으로서의 역할을 하고 있는 VDSL망에서, 라디오 주파수 인터피어런스(RFI: Radio Frequency Interference)가 가해진 VDSL 시스템의 데이터 전송 능력을 분석하였다. 이를 위해 ANSI 표준문서와 FSAN의 제안서를 참조하여 VDSL관점에서 ANSI DSL Standard Group T1E1.4에 제시된 VDSL Test Loop를 사용하였다. .국내에서 사용되고 있는 아마추어 무선(HAM)용 주파수 대역에 적용한 경우에 대해 VDSL 전송 능력을 파악하였으며, 이를 위해 Matlab tool을 이용하여 컴퓨터 시뮬레이션 하였다. VDSL 방식 이론에 근거한 전승 속도에 대한 계산에서, RFI 유입을 방지하기 위해 notch를 형성한 PSD(Power Spectral Density)를 사용하였으며, 이에 대한 실험을 통하여 VDSL 시스템의 전송 속도 감소를 확인하였다.

• International Journal of Advanced Culture Technology
• /
• v.9 no.3
• /
• pp.283-290
• /
• 2021

Recently, correlated superposition coding (CSC) has been proposed to implement non-orthogonal multiple access (NOMA) without successive interference cancellation (SIC), without loss of spectral efficiency, in contrast to conventional independent superposition coding (ISC). However, correlation between signals has reduced the average total allocated power, which results in degraded performance. Thus, in order to avoid the reduction of the average total allocated power owing to correlation between signals, this paper proposes a cross-correlated quadrature amplitude modulation (QAM) NOMA scheme under Rayleigh fading channel surroundings. First, we design the cross-correlated QAM NOMA scheme. Then, simulations demonstrate that for the weaker channel gain's user, the symbol error rate (SER) performance of the proposed cross-correlated QAM NOMA improves largely, whereas for the stronger channel gain's user, the SER performance of the proposed cross-correlated QAM CSM NOMA degrades little, compared to that of the conventional QAM NOMA.

• Journal of the Korean Chemical Society
• /
• v.29 no.4
• /
• pp.382-389
• /
• 1985

The effect of plasma operational parameters for the determination of rare earth elements(REE) by means of inductively coupled plasma(ICP) spectrometry was investigated. While the increase in the flow rate of carrier gas argon enhanced the sensitivity and lowered the detection limit, significant ionization interferences were observed. The decrease in RF power increased the signal to background ratio. The observation point showing the lowest ionization interference was slightly higher than the position where the spatial profile of the analyte reached the maximum. The detection limits of the spectral lines commonly used for the determination of REE were measured and the spectral lines relatively free from spectral interferences were chosen.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.6
• /
• pp.2697-2710
• /
• 2018

Owing to the development of Internet of Things (IoT), the fifth-generation (5G) wireless communication is going to foresee a substantial increase of mobile traffic demand. Energy efficiency and spectral efficiency are the challenges in a 5G network. Non-orthogonal multiple access (NOMA) is a promising technique to increase the system efficiency by adaptive power control (PC) in a 5G network. This paper proposes an efficient PC scheme based on evolutionary game theory (EGT) model for uplink power-domain NOMA system. The proposed PC scheme allows users to adaptively adjusts their transmit power level in order to improve their payoffs or throughput which results in an increase of the system efficiency. In order to separate the user signals, a successive interference cancellation (SIC) receiver installed at the base station (BS) site. The simulation results demonstrate that the proposed EGT-based PC scheme outperforms the traditional game theory-based PC schemes and orthogonal multiple access (OMA) in terms of energy efficiency and spectral efficiency.