• Journal of Information Processing Systems
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• v.17 no.5
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• pp.933-946
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• 2021

In the non-orthogonal multiple access (NOMA) system, multiple user signals on the single carrier are superimposed in a non-orthogonal manner, which results in the interference between non-orthogonal users and noise interference in the channel. To solve this problem, an improved algorithm combining regularized zero-forcing (RZF) precoding with minimum mean square error-serial interference cancellation (MMSE-SIC) detection is proposed. The algorithm uses RZF precoding combined with successive over-relaxation (SOR) method at the base station to preprocess the source signal, which can balance the effects of non-orthogonal inter-user interference and noise interference, and generate a precoded signal suitable for transmission in the channel. At the receiver, the MMSE-SIC detection algorithm is used to further eliminate the interference in the signal for the received superimposed signal, and reduce the calculation complexity through the QR decomposition of the matrix. The simulation results show that the proposed joint detection algorithm has good applicability to eliminate the interference of non-orthogonal users, and it has low complexity and fast convergence speed. Compared with other traditional method, the improved method has lower error rate under different signal-to-interference and noise ratio (SINR).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.2
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• pp.63-75
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• 1983

This paper has investigated and discussed the effects of multiple PSK signals upon an wideband FM signal in an intersystem interference environment between analog and digital radios. Using the derived approximate equation for the output haseband interference noise, the signal-to-interference noise power ratio(SNR) in the top channel baseband signal has been numerically calculated. The results are plotted in graphs as the functions of carrier-to-noise ratio(CNR), carrier-to interfer power ratio(CIR), and normalized carrier separation. From the results in this paper, one can know some optimu, or suitable, operating conditions(frequency allocation, bandwidth, and power, etc.) for an FM channel in the intersystemn interferences from digital PSK channels.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.11
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• pp.3-11
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• 2015

An advanced receiver which can manage inter-cell interference is required to cope with the explosively increasing mobile data traffic. 3rd Generation Partnership Project (3GPP) has discussed network assisted interference cancellation and suppression (NAICS) to improve signal-to-noise-plus-interference ratio (SINR) and receiver performance by suppression or cancellation of interference signal from inter-cells. In this paper, we propose the advanced receiver based on soft decision to reduce the interference from neighbor cell in LTE-Advanced downlink system. The proposed receiver can suppress and cancel the interference by calculating the unbiased estimation value of interference signal using minimum mean square error (MMSE) or interference rejection combing (IRC) receiver. The interference signal is updated using soft information expressed by log-likelihood ratio (LLR). We perform the system level simulation based on 20MHz bandwidth of 3GPP LTE-Advanced downlink system. Simulation results show that the proposed receiver can improve SINR, throughput, and spectral efficiency of conventional system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4390-4407
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• 2019

The paucity of pilot signals in Massive MIMO system is a vital issue. To accommodate substantial number of users, pilot signals are reused. This leads to interference, resulting in pilot contamination and degrades channel estimation at the Base Station (BS). Hence, mitigation of pilot contamination is exigency in Massive MIMO system. The proposed Time Shifted Pilot Signal Transmission with Pilot signal Hopping (TSPTPH), addresses the pilot contamination issue by transmitting pilot signals in non-overlapping time interval with hopping of pilot signals in each transmission slot. Hopping is carried by switching user to new a pilot signal in each transmission slot, resulting in random change of interfering users. This contributes to the change in channel coefficient, which leads to improved channel estimation at the BS and therefore enhances the efficiency of Massive MIMO system. In this system, Uplink Signal Power to Interference plus Noise Power Ratio (SINR) and data-rate are calculated for pilot signal reuse factor 1 and 3, by estimating the channel with Least Square estimation. The proposed system also reduces the uplink Signal power for data transmission of each User Equipment for normalized spectral efficiency with rising number of antennas at the BS and thus improves battery life.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.727-730
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• 2002

This paper proposes the interference cancellation improvement in smart antenna system by using Applebaum array covariance matrix adjustment. This technique adds the specific adjustable multipliers with both desired signal covariance matrix and interference signal covariance matrices in order to overcome some disadvantages and improve the interference cancellation efficiency of Applebaum array. It is based on the desired and undesired signal power or desired signal-to-interference-plus-thermal noise ratio (SINR). As the result from demonstration, the proposed technique can improve and increase the interference cancellation efficiency in smart antenna better than the conventional technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1A
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• pp.84-92
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• 2004

Eigenstructure-based adaptive beamfoming has advantages of fast convergence and the insentivity to errors in the arrival angle of the desired signal. Eigen-decomposing the sample matrix to extract a basis for the Sl (signal plus interference) subspace, however, is very computationally expensive. In this paper, we present a simple subspace based beamforming which utilizes off-diagonal elements of the sample matrix to estimate the Sl subspace. The outputs of overlapped subarrays are combined to produce the final adaptive output, which improves SINR (signal-to-interference-plus-noise ratio) comapred to exploiting a single subarray. The proposed adaptive beamformer, which employs an efficient angle estimation is very roubust to errors in both the arrival angles and the number of the incident signals, while the eigenstructure-based beamforer suffers from severe performance degradation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.4
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• pp.350-359
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• 2013

In this paper, Inter user interference elimination algorithm based on Block Diagonal Geometric Mean Decomposition(BD-GMD) for eliminating inter user interference apply to Zero-Forcing in the Successive Signal to Leakage plus Noise Ratio(SSLNR) in Coordinated Multi-Point Coordinated Beamforming system(CoMP CB). As a result, the leakage power is eliminated. The inter user interference elimination algorithm, however, cannot guarantee the enough desired signal power therefore we perform the channel ordering to overcome this disadvantage and increase the desired signal power. The simulation results show that the proposed scheme provides the improved Bit Error Rate(BER) performance compared with existing SSLNR-Zero-Forcing-Tomlinson Harashima precoding(SSLNR-ZF-THP).

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.75-77
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• 2005

When measuring impedance of electronic component and so on, even the small size can reject the interference to shielding object. But, the interference through human body is grown when measuring bioimpedance without establishing shield specially. Consequently, when measuring bioimpedance in this paper, it proposed impedance measurement method to take advantage of spread spectrum technology, so that can reject the interference without establishing shield specially. Spread spectrum impedance measurement method to propose in this paper can reject the interference signal that occurring from medical instruments in the human body, the interference signal that is flowed in from surrounding environment when measuring impedance. It improved SJR(signal to jamming ratio) about 22dB than conventional method that actually realize and experiment spread spectrum impedance measurement method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.6 no.1
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• pp.21-26
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• 1981

The effect of wideband FDM-FM signal on binary CPSK signal in an interchannel interference environment has been investigated. A general equation of the bir error rate of binary CPSK signal with cochannel and adjacent channel interference from FDM-FM signal has been derived. The numerical results are given in graphs as the functions of carrier to noise ratio (CNR), carrier to interference ratio(CIR) and normalized carrier separation between PSK and FM signals. The results obtained can be used om desogmomg tje freqiemcy allocation, bandwidths and powers of PSK and FM signals in same radio frequency (RF) bands.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.357-360
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• 1998

DS/CDMA system rejected narrow-band interference and additional White Gaussian noise which are occured at multipath, intentional jammer and multiuser to share same bandwidth in mobile communication systems. Because of having not sufficiently obtained processing gain which is related to system performance, they were not effectively suppressed. In this paper, an matched filter channel model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in DS/CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in matched filter receiver scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of matched filter using backpropagation neural network improved than that of RAKE receiver of direct sequence spread spectrum considering of con-channel and narrow-band interference.