• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.15-20
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• 2016

Compared to the MIMO system using the spatial multiplexing methods and the MIMO system using the diversity scheme achieved a high rate, but the lower the diversity gain to improve the data transmission reliability should separate the spatial stream at the MIMO receiver. In this paper, we compared Channel capacity detection methods with the Lattice code, the 3-user interference channel and linear channel interference detection methods ZF (Zero Forcing) and MMSE (Minimum Mean Square Error) detection methods. The channel is a Diagonal channel. In other words, Diagonal channel is confirmed by the inverse matrix satisfies the properties of Jacket are element-wise inverse to $[H]_N[H]_N^{-1}=[I]_N$.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.11
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• pp.18-24
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• 2009

This paper proposes two novel prediction-based adaptive selection cooperation schemes combined with a new relay selection strategy. In the proposed schemes, the destination predicts whether the transmission will be successful or not before a single relay is selected to transmit source's decoded data. Depending on the prediction, the destination feeds back a command to the whole network. Numerical results show that the proposed schemes combined with the relay selection strategy successfully reduce its outage probability, improve its throughput, save transmitted power, and prolong the lifetime of the network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7C
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• pp.481-487
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• 2011

Cyclic delay diversity (CDD) is a simple transmit diversity technique for an OFDM system using multiple transmit antennas. However, the performance of post-FFT estimation, i.e., integer frequency offset (lFO) is deteriorated by high frequency selectivity introduced by CDD. In this paper, the IFO estimation scheme is proposed for OFDM-based DRM+ system with CDD. Based on the pilot subset partitioning, the proposed IFO estimation scheme reduces the effect of performance degradation caused by frequency selectivity in OFDM systems with CDD . The simulation results show that the performance of the proposed IFO estimator is significantly improved when compared to that of the conventional IFO estimator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6C
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• pp.403-411
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• 2011

This paper addresses a cooperative transmission scheme based on Alamouti coding for cognitive radio networks over frequency selective fading channels. In the proposed scheme, the Alamouti coded form at the destination node is constructed through a simple combination of symbols at the source node, instead of the time-reversal operation and the conjugate operation at the relay nodes used in the conventional scheme. Numerical results show that the proposed scheme achieves a higher order cooperative diversity than that of the conventional scheme.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.1
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• pp.95-101
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• 2009

Wireless Sensor Network (WSN) has limited power and bandwidth. In order to high data rate and high speed communication systems are required. Cooperative communication system can help to decrease power consumption through spatial diversity. In cooperative transmission, one partner node assists one sensor node to transmit their data to destination. Instead of using M partners for M sensor nodes, we propose 1 partner for M sensor nodes. And we proposed relay selection scheme base on ARQ. Proposed protocol offers higher diversity order as conventional one with much less bandwidth and power. The destination will consider the one packets received from the best relay to reduce the complexity of the system. We verified BER performance for the proposed protocol through Monte-Carlo simulation over Rayleigh fading plus AWGN.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.61-66
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• 2011

Cooperative Communication using relays which include network separated into fixed cooperative relaying and incremental cooperative relaying defending on method receiving signal from a source. If some nodes included network is Primary user ad source and destination, another is Secondary user as relay, The nodes included network excepting source can help PU transmit signal. In the case of all of SU playing a role as relay, destination can get diversity gain, but useless time slot is consumed for transmitting signal. So in this paper, we analysis cooperative relaying which a node succeeding to sense primary signal send signal to destination. We use matlab simulation tool and consider AF, DF, fixed relaying, incremental relaying

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1180-1187
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• 2012

In this paper, joint transmission space division multiple access(JT-SDMA) scheme is proposed to mitigate inter-cell interference(ICI) in cooperative wireless communications system with limited feedback. We propose a systematic design method for a codebook consisting of a finite number of unitary matrices suitable for network multiple-input multiple-output( MIMO) channel characteristics. A centralized cluster scheduling scheme is proposed to both mitigate ICI and maximizes multiuser diversity gain with limited feedback. It is shown that the proposed JT-SDMA scheme outperforms a existing coordinated SDMA scheme even in wireless network environments where sufficient multiuser diversity order can not be provided through efficient ICI mitigation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.8
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• pp.1234-1240
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• 2002

In this paper, we analyze the block error performance of the CDMA system, whose information data are spread spectrum with PN sequences, and the chip signals are modulated with BPSK signal, combining MRC(Maximum Ratio Combine) diversity techniques with repetition transmission, FEC(Forward Error Correction) code in mobile communication channel which is characterized by Nakagami fading. As a results of study, the coding techniques provide more efficient improvement than a diversity techniques, but coding techniques are required the adding bandwidth as many coding rate. Also, when the system is combined MRC diversity techniques with coding techniques, the amount of improvement is dramatically increased.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.1-7
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• 2010

In this paper, the technique for obtaining diversity gain without increasing the antenna is proposed using symbol share in the OFDM systems. Proposed technique groups symbols which are mapped into different sub-carriers and these symbols are modulated by proposed constellation. Proposed constellation has the identical minimum distance with QPSK modulation constellation and obtain more frequency diversity gain. Also, proposed modulation scheme make it possible to increase data rate using subcarriers allocated symbols.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.11
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• pp.1134-1142
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• 2003

This paper presents a hardware implementation of the STS diversity system, utilizing FPGAs and introduces the function and the design method of each of the modules of the system. In order to improve the performance of the implemented STS system which is an open loop transmit diversity system under fading environment, the exact estimation of the communication channel is essential. Therefore, we propose the optimal forgetting factor to estimate pilot channel in this paper, It is shown in this paper that the pilot channel is estimated using the forgetting factor of 0.7 without increasing the integration range of the pilot channel even when the power of pilot channel is not sufficiently large in CDMA 2000 1x signal environment.