• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.37-46
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• 1996

In this paper, we analyzed the performance improvement of the DS-CDMA/dPSK cellular mobile communication system with CCI canceller and RAKE receiver techniques in mobile radio channel which is characterized by AWGN, Multi-user interference (mUI) and frequency-selective rayleigh fading. System capacity i.e., number of user per cell has been derived and the evaluated results are shown in figuraes as a function of PN code sequence length, number of RAKE receiver tap, BER and E$_{b}$/N$_{o}$. The voice activity factor is assumed to be 3/8 the number of sectors in a cell 3 and MUI is modeled as gaussian process. From the results, the capacity of the DS-CDMA/DPSK cellular mobile communication system is improved by adopting CCI canceller. When we adopt the RAKE receiver to mitigate the multipath fading, the error performance is improved and the amount of improvement is proportional ot the number of taps L in the case that each tap contains a signal component and the better of improvement can be obtained, the smaller of the SNR difference in each tap. The system capacity is more increased when the CCI canceller and the RAKE receiver is used in cascade.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.423-428
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• 2004

High-data rate and high speed communication techniques are required for wireless mobile communication systems to provide multimedia services. A multiple antenna technology may be used to meet this demand. In this paper, a method for performance improvement of a WCDMA downlink system using space time block coding is proposed in quasi-static Rayleigh fading channels. The proposed receiver uses the cross correlation matrix obtained by each finger corresponding to multi paths. To obtain maximum diversity gain, the inverse of cross correlation matrix and the Hermitian matrix of the channel matrix for each path arc computed, and then applied to received signals. Various simulation results show that the proposed receiver outperforms a conventional receiver in Rayleigh fading channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.136-143
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• 2010

In this paper, we investigate decode-and-forward (DF) relaying systems with a direct link between the source and the destination node. The objective of this paper is to determine the better relaying strategy between 3-hop DF relaying and dual-hop DF relaying with the best relay selection. Assuming Rayleigh fading channels, we present closed-form outage probability of the 3-hop relaying and the dual-hop relaying, respectively, and compare the performances by numerical investigation. Numerical results show that if the channel is poor, the outage performance of the 3-hop relaying is better than the dual-hop relaying.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.417-421
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• 2005

In the recent digital communication systems, the performance of Turbo Code using the error correction coding depends on the interleaver influencing the free distance determination and the recursive decoding algorithms that is executed in the turbo decoder. However, performance depends on the interleaver depth that needs many delays over the reception process. Moreover, turbo code has been known as the robust coding methods with the confidence over the fading channel. International Telecommunication Union(ITU) has recently adopted it as the standardization of the channel coding over the third generation mobile communications(IMT-2000). Therefore, in this paper, we proposed the interleaver that has the better performance than existing block interleaver, and modified turbo decoder that has the parallel concatenated structure using MAP algorithm. In the real-time voice and video service over third generation mobile communications, the performance of the proposed two methods was analyzed and compared with the existing methods by computer simulation in terms of reduced decoding delay using the variable decoding method over AWGN and fading channels for CDMA environments.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.456-462
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• 2011

This paper investigates the outage behavior of peak interference power limited cognitive radio (CR) networks with multiple transmit antennas. In CR-multi-input single-output (MISO) channel, the total transmit power is distributed over the transmitantennas. First, we use the orthogonal space-time codes (STC) to achieve the transmit diversity at CR-receiver (rx) and investigate the effect of the power distribution on the interference power received at the primary-receiver (P-rx). Then, we investigate the transmit antenna selection (TAS) scheme in which the CR system selects the best transmit antenna and allocates all the power to the selected best antenna. Two transmit antenna selection strategies are proposed depending on if feedback channel is available or not. We derive the closed form expressions of outage probability and outage capacity of all schemes with arbitrary number of transmit-antennas. We show that the proposed schemes significantly improve the outage capacity over the single antenna systems in Rayleigh fading environment. We also show that TAS based scheme outperforms the STC based scheme when peak interference power constraint is imposed on the P-rx only if a feedback channel from CR-rx to CR-transmitter is available.

• The KIPS Transactions:PartC
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• v.13C no.7 s.110
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• pp.865-872
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• 2006

Cooperative communications (CC) have received a great deal of attention recently as an efficient way to obtain the spatial diversity without physical arrays. Thus, space-time block codes (STBC) which are well-known for use in co-located multi-antenna systems can be still utilized for single-antenna users in a distributed fashion. In this paper, we propose a cooperative signaling structure using the $\frac{3}{4}$-rate STBC and derive closed-form BER expression which takes the effect of network geometry and transmit power constraint into account. A variety of simulated and numerical results demonstrated the cooperation considerably outperforms the direct transmission when partners are located in appropriate positions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.3
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• pp.999-1021
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• 2023

Differential spatial modulation uses the antenna index to transmit information, which improves the spectral efficiency, and completely bypasses any channel side information in the recommended setting. A generalized distributed multiple turbo coded-cooperative differential spatial modulation based on distributed multiple turbo code is put forward and its performances in Rayleigh fading channels is analyzed. The generalized distributed multiple turbo coded-cooperative differential spatial modulation scheme is a coded-cooperation communication scheme, in which we proposed a new joint parallel iterative decoding method. Moreover, the code matched interleaver is considered to be the best choice for the generalized multiple turbo coded-cooperative differential spatial modulation schemes, which is the key factor of turbo code. Monte Carlo simulated results show that the proposed cooperative differential spatial modulation scheme is better than the corresponding non-cooperative scheme over Rayleigh fading channels in multiple input and output communication system under the same conditions. In addition, the simulation results show that the code matched interleaver scheme gets a better diversity gain as compared to the random interleaver.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8B
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• pp.1348-1356
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• 2000

In this paper, we proposed a trellis coded Multi-Carrier CDMA 16 QAM system with multiple transmit/receive antenna diversity technique, which is simple and suitable for indoor wireless communications. The proposed multiple transmit/receive antenna diversity technique is that the transmitter sends a trellis coded Multi-Carrier CDMA 16 QAM signal from multiple transmitting antennas with intentional time delays, which makes a receiver possible to distinguish and combine the signals from different antennas. In wireless indoor communication system, if we allow the increase of the complexity of the system, it is also possible to achieve additional diversity gain in the performance with the combination of the proposed technique and the conventional receiving antenna diversity. Furthermore, we have found that the proposed trellis coded Multi-Carrier CDMA 16 QAM system, which employs multiple transmit/receive antenna, is less sensitive to the multiple user interference and fading than conventional receiving antenna diversity systems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.8
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• pp.1-10
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• 2000

Performance analyses of hybrid DS-SFH spread-spectrum systems using coherent MSK and QPSK modulation techniques are considered over Rayleigh fading channel in the presence of multi-tone jamming. The BER equations for MSK and QPSK systems with non-diversity reception in the receiver are derived as the concept of average signal-to-noise power ratio E$\_$b//N$\_$0/ and jamming-to-signal power ratio JSR, and the performances is evaluated for various system parameters. The evaluation of performance is done between fading and nonfading system, and between MSK and QPSK system. Results show that the performances of two systems are similar in low JSR. However, MSK system outperforms QPSK system as JSR increases. Overall performances of two systems are a little improved as the DS spreading gain increases for the total spread-spectrum bandwidth fixed. The performance difference between fading system and nonfading system is similar in low E$\_$b//N$\_$0/, however, it becomes very largewith increase of E$\_$b//N$\_$0/..

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.570-575
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• 2022

The MX-S2X, utilizing high-frequency broadband communication technology, provides a reliable connection between land, ship, and facilities. This technology is expected to be effectively utilized as a future maritime communication infrastructure in the upcoming mixed navigational situation among autonomous and manned and/or unmanned ships. Following the physical layer design and M&S-based performance analysis of the MX-S2X system to overcome maritime multipath fading, this paper confirms the optimized and detailed design of physical layer hardware and implemented it to verify the performance. The PER(Packet Error Rate) performance was then measured by configuring a test environment to verify the implemented hardware. The results showed that the performance degradation was 0.2 dB in the AWGN environment and 1.2 dB in the Multi-path Fading on Sea Environment, thus confirming the successful implementation of the physical layer.