• Journal of IKEEE
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• v.11 no.4
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• pp.340-347
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• 2007

This paper proposes a new class of Space-Time Block Codes, which is manipulated from the existing transmit diversity schemes. We analyze the performance and the receiver complexity of the proposed scheme and confirm that the new diversity scheme can yield performance gain over other existing four-transmit antenna cases. By relaxing the diversity criterion on code designs, the proposed space-time code provides a full transmission rate for four-transmit antennas and makes it possible to approach the open-loop Shannon channel capacity. Outage capacity and simulation results are used to show that substantial improvements in performance while maintaining a simple linear processing receiver structure are obtained in frequency selective channels.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.727-732
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• 2005

OFDM is a digital modulation technique where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of OFDM systems with SFBC and STBC antenna diversity are analyzed, where data is transmitted over time and frequency selective Rayleigh fading channel. The performance of this technique, gauged by the average bit error rate, is analyzed for the OFDM systems.

• Journal of information and communication convergence engineering
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• v.1 no.3
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• pp.119-122
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• 2003

In this paper presents equations which describe an average weighted spectrum of errors and average block error probabilities for noncoherent frequency shift keying (NCFSK) used in D-branch maximal ratio combining (MRC) diversity in independent very slow nonselective Nakagami fading channels. The average is formed over the instantaneous receiver signal to noise ratio (SNR) after combining. the analysis is limited to additive Gaussian noise.

• Journal of electromagnetic engineering and science
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• v.5 no.1
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• pp.1-7
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• 2005

The implementation of a simple analog in-phase combiner is presented for a high capacity radio relay system with space diversity. It provides good performance in terms of simple hardware and easy control, and measured results are in good agreement with simulated ones. To suggest practical applications, signatures with/without diversity are measured for STM-1 signal of 64-QAM radio relay system combined with a 13-tap equalizer, and they provided more than 25 dB fade depth at 10$^{-3}$ BER under the frequency selective fading condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11A
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• pp.924-932
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• 2011

In this paper, we propose a possibility of usage of carrier superpositioning scheme for a specific slow frequency hopping(SFH) transmission method for the satellite data link in which all of hopping carriers have to be synchronized to DSM transponder of our previous work and usage of frequency diversity in the saved frequency to overcome the SFH disadvantage against jammer. We have analyzed anti-jamming performance and LPI performance and confirmed that the proposed scheme can support data service with 18.5dB processing gain against the worst case partial band jamming and give 2.5dB gain in the LPI performance against D&M detector which can estimate the data rate of unknown signals.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.489-498
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• 2003

Recently to introduce new services of ultra-high speed wireless access and systems beyond the 3rd generation mobile communication, 5 GHz band has been highly interested. As a way of getting the required frequency, it is considered that microwave relay bands below 6 GHz, which shows a slow decrease in demand and less cost-effectiveness, should be moved to other bands above 6 GHz. In this paper, as a tool for analyzing microwave link design and its service quality, the outage prediction based upon Vigants & Barnett＇s model is reviewed. To show outage and availability calculation, simulations are performed for the operating 4 GHz radio sites, and some results and features regarding frequency movement to 6.7 as well as 8 GHz are also discussed in terms of diversity techniques, bit error rate, and availability As the results, it is confirmed that only the diversity techniques of space or space and frequency can satisfy the annual objective of availability irrespective of frequency movement.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1643-1648
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• 2005

MIMO system takes advantage of the spatial diversity obtained by spatially separated antennas for high- performance and high-capacity broadband wireless access. In this paper, we propose Carrier Interferometry coded MIMO-OFDM system (MIMO-CI/OFDM) which provides frequency and spatial diversity. One combined diversity gains featly improve the performance of OFDM systems. To perform a performance analysis, we have used SPW platform that provides an easy tool to analyze the performance. The results show that the performance of MIMO-CI/OFDM shows an approximately 4dB gain over the MIMO-OFDM even in highly frequency selective fading channels.

• 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.

• Journal of Korean Society of Rural Planning
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• v.13 no.2
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• pp.1-5
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• 2007

Shannon and Simpson indexes are used for species diversity analysis of ecosystem. In species diversity analysis of ecosystem, not only frequency of each species but also survey size have to be considered. In this study, total information composed with knowledge and ignorance was suggested as a species diversity analysis method for ecosystem survey. To apply developed method, flora in the Sangachun river valley was sampled with 19 sites and 198 species. In applying results, Shannon index shows more reasonable results than Simpson index by the variance of sample size but has difficulties of determining the relation of surveying species number and sample site number. Suggested total information can overcome this difficulty by the relation of knowledge and ignorance.

• ETRI Journal
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• v.25 no.4
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• pp.231-237
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• 2003

We derive and analyze the exact closed-form expression for the average bit error probability (BEP) of M-ary square quadrature amplitude modulation (QAM) for diversity reception in frequency-nonselective Nakagami fading. A maximal ratio combining (MRC) diversity technique with independent or correlated fading cases are considered. Numerical results demonstrate error performance improvement with the use of MRC diversity reception. The presented new expressions offer a convenient way to evaluate the performance of M-ary square QAM with an MRC diversity combiner for various cases of practical interest.