• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.560-569
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• 2005

This paper proposes an algorithm for transmit antenna selection in a multi-input multi-output(MIMO) spatial multiplexing system with per antenna rate control(PARC) and an ordered successive interference cancellation (OSIC) receiver. The active antenna subset is determined at the receiver and conveyed to the transmitter using feedback information on transmission rate per antenna. We propose a serial decision procedure consisting of a successive process that tests whether antenna selection gain exists when the antenna with the lowest pre-processing signal to interference and noise ratio(SINR) is discarded at each stage. Furthermore, we show that 'reverse detection ordering', whereby the signal with the lowest SINR is decoded at each stage of successive decoding, widens the disparities among fractions of the whole capacity allocated to each individual antenna and thus maximizes a gain of antenna selection. Numerical results show that the proposed reverse detection ordering based serial antenna selection approaches the closed-loop MIMO capacity and that it induces a negligible capacity loss compared with the heuristic selection strategy even with considerably reduced complexity.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.587-592
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• 2002

A new digital correlator fur an airborne synthetic aperture radiometer was designed in order to replace the conventional analog correlator unit which will become very complicated while the number of channels is increasing. The digital correlator uses digital IQ demodulator instead of the intermediate frequency (IF) phase shifter to make the correlation processing performed digitally at base band instead of analogly at IF. This technique has been applied to the digital receiver in softradio. The down-converted IF signals from each pair of receiver channels become low rate base-band digital signals after under-sampled, Digitally Down-Converted (DDC), decimated and filtered by FIR filters. The digital signals are further processed by two digital multipliers (complex correlation), the products are integrated by the integrators and finally the outputs from the integrators compose of the real part and the imaginary part of a sample of the visibility function. This design is tested by comparing the results from digital correlators and that from analog correlators. They are agreed with each other very well. Due to the fact that the digital correlators are realized with the help of Analog-Digital Converter (ADC) chips and the FPGA technology, the realized volume, mass, power consumption and complexity turned out to be greatly reduced compared with that of the analog correlators. Simulations show that the resolution of ADC has an influence on the synthesized antenna patterns, but this can be neglected if more than 2bit is used.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.9
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• pp.3172-3193
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• 2022

Cognitive radio-simultaneous wireless information and power transfer (CR-SWIPT) has attracted much interest since it can improve both the spectrum and energy efficiency of wireless networks. This paper focuses on the resource sharing between a point-to-point primary system (PRS) and a multiuser multi-antenna cellular cognitive radio system (CRS) containing a large number of cognitive users (CUs). The resource sharing optimization problem is formulated by jointly scheduling CUs and adjusting the transmit power at the cognitive base station (CBS). The effect of accessing CUs' spatial channel correlation on the possible transmit power of the CBS is investigated. Accordingly, we provide a low-complexity suboptimal approach termed the semi-correlated semi-orthogonal user selection (SC-SOUS) algorithm to enhance the spectrum efficiency. In the proposed algorithm, CUs that are highly correlated to the information decoding primary receiver (IPR) and mutually near orthogonal are selected for simultaneous transmission to reduce the interference to the IPR and increase the sum rate of the CRS. We further develop a spatial correlation-based resource sharing (SC-RS) strategy to improve energy sharing performance. CUs nearly orthogonal to the energy harvesting primary receiver (EPR) are chosen as candidates for user selection. Therefore, the EPR can harvest more energy from the CBS so that the energy utilization of the network can improve. Besides, zero-forcing precoding and power control are adopted to eliminate interference within the CRS and meet the transmit power constraints. Simulation results and analysis show that, compared with the existing CU selection methods, the proposed low-complex strategy can enhance both the achievable sum rate of the CRS and the energy sharing capability of the network.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.8
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• pp.10-15
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• 2009

In this paper, we propose a frequency-domain tone interference cancellation algorithm for direct-sequence spread spectrum systems. In the previously proposed frequency-domain interference cancellation algorithms, the interference signal is estimated and compensated in the frequency-domain and then, with IFFT (inverse Fourier transform), the compensated frequency-domain signal is transformed to the time domain signal for the remaining receiver operations. Unlike the previous works, the proposed algorithm does not requires IFFT and thus, the proposed algorithm not only shows the virtually identical performance but also requires lower hardware complexity compared to the previous works.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.86-93
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• 2009

We investigate lattice-reduction-aided precoding techniques for multi-user multiple-input multiple-output (MIMO) channels. When assuming full knowledge of the channel state information only at the transmitter, a vector perturbation (VP) is a promising precoding scheme that approaches sum capacity and has simple receiver. However, its encoding is nondeterministic polynomial time (NP)-hard problem. Vector perturbation using lattice reduction algorithms can remarkably reduce its encoding complexity. In this paper, we propose a vector perturbation scheme using Seysen's lattice reduction (VP-SLR) with simultaneously reducing primal basis and dual one. Simulation results show that the proposed VP-SLR has better bit error rate (BER) and larger capacity than vector perturbation with Lenstra-Lenstra-Lovasz lattice reduction (VP-LLL) in addition to less encoding complexity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.3
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• pp.276-282
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• 2003

OFDM is effective for the high speed data transmission. However, the nonlinear distortion is a serious problem because of the high PAPR due to many subcarriers. The conventional SLM selects the OFDM signal with the lowest PAPR. In this method, OFDM data can be correctly recovered only if the side information about the phase sequence is transmitted to receiver. This paper proposes a new method of side information insertion into the conventional SLM and reduces the computational complexity by adaptive method. Performances are compared in case that three kinds of phase sequences are used for phase rotation factor. The adaptive SLM method has the same PAPR reduction as the conventional SLM method. The required BER can be guaranteed by the proposed method. When subcarrier number N=32, computational complexity is reduced to 48 %, 72 % and 51 % for the branch number U=4, 8 and 16, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1287-1296
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• 2009

It is very important to estimate the Signal to Noise Ratio(SNR) of received signal in time varying channel state. Most SNR estimation techniques derive the SNR estimates solely from the samples of the received signal after the matched filter. In the severe distorted wireless channel, the performance of these estimators become unstable and degraded. LP-based SNR estimator which can operate on data samples collected at the front-end of a receiver shows more stable performance than other SNR estimator. In this paper, we study an efficient SNR estimation algorithm based on LP and propose a new estimation method to decrease the computation complexity. Proposed algorithm accomplishes the SNR estimation process efficiently because it uses the forward prediction error and its conjugate value during the linear prediction error update. Via the computer simulation, the performance of this proposed estimation method is compared and discussed with other conventional SNR estimators in digital communication channels.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.749-756
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• 2010

The signal space diversity is one of the promising transmission techniques in next generation mobile TV service. However, DVB-T2 does not consider the multiple antennas (MIMO) so that the cyclic Q-delay method, a component interleaver in DVB-T2, causes a critical issue in detecting symbols at the receiver side by increasing the inter-symbol dependency. To solve this problem, the component-swapping technique is proposed, which limits the inter-symbol dependency in order to reduce detection complexity. In this paper, the achievable gain of a component-swapping technique combined with 16K LDPC code defined in DVB-T2 is evaluated by computer simulations. From the results, the gain is confirmed in terms of BER and receive complexity compared to legacy component interleaver methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.413-417
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• 2014

In coherent superhigh speed optical transmission link, compensating the system impairments are critical issues. Among these issues, phase noise and carrier frequency offset are the most important impairments which interrupt the signal recovery. This paper suggests a algorithm of digital signal processing that compensates the phase noise and carrier frequency offset and verified its validity. The suggested digital signal processing algorithm has a lower computational complexity compared with the previous algorithms, so it can ease the burden of signal processing at the receiver to provide high speed optical transmission system.

• Journal of Broadcast Engineering
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• v.4 no.1
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• pp.32-43
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• 1999

This paper addresses schemes which securely transmit voice and data information under the worst communication environment using the frequency hopping(FH) communication system to avoid monitoring or interference against enemy. In case of using the conventional FEC and bit interleaving scheme. the processing time for error control coding and bit interleaving due to system complexity is highly demanded. In this paper. the effective information coding scheme of maprity error correction and block interleaving compatible to the proposed FH communication system is proposed to transmit voice or data (I6Kbps. 4.8Kbps. 2.4Kbps. 1.2Kbps, O.6Kbps) under the worst FH communication channel. In transmitter. low rate data signals are configured to majority data blocks. and transmitted repeatedly to FH channel which are structured to 20Kbps hopping frame cells. In receiver. the received data are decoded block by block, and taken majority error correction. Consequently. burst or random errors are corrected at the block deinterleaver and the majority decoder. The proposed coder structure reduces the coding/decnding processing time as well as the jamming interferences, and further simplify the data processing complexity for FH communication. Improved performance of the proposed scheme was verified under simulated channel environments.