• Journal of electromagnetic engineering and science
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• v.6 no.4
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• pp.222-228
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• 2006

In this paper, the performance of a multiuser diversity system combined with a multi-element transmit antenna system is analyzed under the assumption of independent Rayleigh fading. A measure of system .level performance is an average channel capacity as a function of the number of users and antennas. Average channel capacity is obtained from the instantaneous signal-to-noise ratio(SNR) distribution combined by both transmit diversity(TD) at each link and multiuser diversity at system level. Numerical results show that closed-loop antenna techniques provide an additional gain with multiuser diversity system due to array gain, even though space diversity gain reduces multiuser diversity gain. On the other hand, the space-time block coding(STBC) that provides full order space diversity gain only has a destructive influence on multiuser diversity.

• International journal of advanced smart convergence
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• v.7 no.3
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• pp.37-43
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• 2018

Lattice-reduction (LR) techniques have been developed for signal detection in spatial multiplexing multiple input multiple output (MIMO) systems to obtain the largest diversity gain. Thus, an LR-assisted zero-forcing (ZF) receiver can achieve the maximum diversity gain in spatial multiplexing MIMO systems. In this paper, a simplified analysis of the achievable diversity gain is presented by fitting the channel coefficients lattice-reduced by a complex Lenstra-Lenstra-$Lov{\acute{a}}z$ (LLL) algorithm into approximated Gaussian random variables. It will be shown that the maximum diversity gain corresponding to two times the number of receive antennas can be achieved by the LR-based ZF detector. In addition, the approximated bit error rate (BER) expression is also derived. Finally, the analytical BER performance is comparatively studied with the simulated results.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.86-92
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• 2013

The present paper defines diversity gain for stationary users. This deals in particular with gathering the received signal statistics over possible user positions and orientations in space rather than over time, and to define a meaningful diversity gain related to the cumulative improvement of the performances of the 1% users with the worst receiving conditions. The definition is used to evaluate diversity gain for some typical small antennas in an extreme environment with only line-of-sight (LOS). The LOS environment is regarded as user-distributed 3D-random LOS caused by the statistics of an ensemble of stationary users with arbitrary orientations in the horizontal plane (2D), and with arbitrary orientations of their wireless devices in the vertical plane. Thus, an overall 3D-random distribution of user orientation is assumed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.578-588
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• 1998

In this paper, we analyzed the propagation characteristics of polarization diversity in the view of diversity gain, cross correlation coefficient and average received signal strength, and compared it with those of space diversity. From the results, we could confirm that in the care of line of sight(LOS), space diversity gain is bigger than polarization diversity gain by 2 dB and the diversity gain of mobile transmitting with 90 degree is bigger than that of mobile transmitting with 45 degree by 1 dB. However, in the area of non-line of sight(NLOS), the diversity gains were all most the same in two diversity schemes and in specular cases, polarization diversity showed better performances. Also it was verified that under the NLOS conditions, diversity gain of mobile transmitting with 45 degree was at least 1 dB bigger than that of mobile transmitting with 90 degree.

• Journal of IKEEE
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• v.13 no.2
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• pp.220-223
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• 2009

A simple measurement system is built to estimate the dual-antenna diversity gain at 2.4GHz easily in open lab environment. To obtain multipath fading propagation channel, the system consists of two transmission horn that placed on opposite direction and a rotating stage mechanically changing the position of test dual-antenna with time over distance greater than one wavelength. Estimated diversity is nearly same as theoretical value such that measured diversity gain of 30mm separated is about 6dB similar to theoretical value of 5.7dB and increases monotonically with the increasing separation distance as predicted by the theory. Proposed measurement system that is simple enough to fit in a small space can evaluate the performance of various dual-antennas with a reasonable accuracy with lower 5% difference between the ten sets of measured waveform distribution and theoretical Rayleigh cumulative distribution.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.6
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• pp.81-88
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• 2012

Space diversity and space multiplexing gain can be achieved with MIMO system. This paper proposes spatial coding method to MIMO system using data information and antenna selection technique. This technique provides coding gain as well as space diversity gain. For MIMO system with BPSK modulation, BER performance is analyzed and space diversity gains are compared through simulation in terms of data maldistribution degree.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.301-303
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• 2016

This paper proposes a method providing diversity gain using small base stations in a cell coverage in order to improve diversity gain. The small base stations and the conventional base station consist a virtual MIMO array by using the cooperative communication scheme. Also, transmission diversity scheme is applied. A mobile user can receive the signals having the improved reliability by the applied transmission diversity scheme and the cooperative communication scheme.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.233-236
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• 2000

본 논문에서는 다중 경로 페이딩에 의한 성능의 손실을 보상하기 위하여 간단한 equal gain combining diversity를 갖는 802.11a 무선 LAN용 OFDM 시스템의 HER 성능을 다중경로 환경 하에서 분석하였다. 모의 실험 결과에 따르면, 다중경로채널에서 전송 파워를 살펴보면, 2branch equal gain combining diversity를 사용한 무선 LAN용 OFDM시스템이 diversity를 사용하지 않는 OFDM 시스템보다 BER 10/sup -3/에서 3㏈ 정도의 이득을 줄 수 있었다. Branch 수를 3개를 사용한 경우에는 BER 10/sup -3/에서 branch 2개를 사용한 경우보다 약 2㏈정도 이득을 줄 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.369-377
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• 1998

In this paper, we performed the comparisons between polarization diversity using dual polarization antennal which has $\pm45^{\circ}$slanted linear polarization characteristics and conventional space diversity in rural and residential areas. The analysis was done by evaluating the diversity gain improvement and cross correlation coefficients between two received signals through each diversity branch. From the results, we could confirmed that space diversity has bigger diversity gain than polarization diversity by 1~2 dB, and there is a little difference of $\pm0.1$ in cross correlation coefficients by analyzing CDF under portable mobile phone environments.

• Journal of Advanced Navigation Technology
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• v.15 no.6
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• pp.1053-1058
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• 2011

In this paper, we propose a concatenated single antenna diversity system to assure the data transmission reliability between flight type air nodes which move according to their atypical orbit, then analyze its performance. The proposed system achieve a diversity gain using single antenna and a coding gain from convolutional code simultaneously. Simulation result about the bit error rate(BER) of the proposed system shows that its BER performance is about 9.5dB greater than convolutional code at $10^{-4}$ and about 14dB greater than space time block code at $10^{-3}$ which has a full diversity gain. In addition, compared with space time trellis code with diversity gain and coding gain, the proposed system shows the better 4dB at a BER of $10^{-5}$. Therefore, it is necessary that concatenated single antenna diversity should be adopted to the reliable data transmission of flight type air nodes.