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Diversity Scheme (diversity + scheme)

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Selected Abstracts

Performance of multi level-turbo coding with neural network-based channel estimation over WSSUS MIMO channels

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2009
Ersin Gose
Abstract This paper presents the performance of the transmit diversity-multi level turbo codes (TD-MLTC) over the multiple-input,multiple-output (MIMO) channels based on the wide sense stationary uncorrelated scattering (WSSUS). The multi level-turbo code (ML-TC) system contains more than one turbo encoder/decoder block in its structure. At the transmitter side, the ML-TC uses the group partitioning technique that partitions a signal set into several levels and encodes each level separately by a proper component of the encoder to improve error performance. The binary input sequence is passed through the MLTC encoder and mapped to 4-PSK and then fed into the transmit diversity scheme for high data transmission over wireless fading channels. At the receiver side, distorted multi-path signals are received by multiple receiver antennae. WSSUS MIMO channel parameters are estimated by using an artificial neural network and an iterative combiner. Input sequence of the first level of the MLTC encoder is estimated at the first level of MLTC decoder. Subsequently, the other input sequences are computed by using the estimated input bit streams of the previous levels. 4-PSK two-level turbo codes are simulated for 2Tx,1Rx and 2Tx,2Rx antenna configurations over WSSUS MIMO channels. Here, TD-MLTC and its efficient implementations are discussed and simulation results are given. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Analyzing GPS signals to investigate path diversity effects of non-geostationary orbit satellite communication systems

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2002
Hsin-Piao Lin
Abstract The concept behind path diversity is that a user who can access several satellites simultaneously will be able to communicate more effectively than a user who could only access one. The success of this method depends on the environment, the satellite constellation, and diversity combining technology. This paper explores the path diversity effects of non-geostationary orbit (NGO) satellite personal communication services, for different degrees of user mobility, under various scenarios, using the constellation of the global positioning system (GPS). Measurements are taken near downtown Taipei. Three types of mobilities (fixed-point, pedestrian, and vehicular) are examined, and the switch diversity and maximum ratio combining method are applied to determine the path diversity gain and calculate bit error probability. The error probability performance of applying diversity schemes in coherent binary phase shift keying (BPSK) and non-coherent differential phase shift keying (DPSK) modulations over Rician fading channels are also analysed and evaluated by using the characteristic function method. The results show that fading can be significantly reduced and diversity greatly increased. A significant diversity gain and improvement in bit error rate (BER) can be expected in all cases by simply applying switch diversity scheme. Besides, for the maximum ratio combining method, the results imply that summing two satellite signals suffices to increase diversity and improve the bit error rate performance. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Prediction of triple-orbital diversity performance in Earth-space communication

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2002
A. D. Panagopoulos
Abstract Orbital diversity is considered to be an effective technique to overcome large fade margins in satellite communication links. This paper discusses triple-orbital diversity, which uses three satellites and an Earth receiving site. A method for calculating the outage probability of a triple-orbital diversity protection scheme is proposed. It is based on a model for convective raincells and the lognormal assumption for point rainfall rate statistics. Numerical results are compared with an available set of experimental data taken from a VSAT Earth-station located in Japan. The agreement was found to be quite encouraging. Some useful conclusions, concerning the relative advantage of using triple- against the double-orbital diversity scheme are also deduced. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Analyzing GPS signals to investigate path diversity effects of non-geostationary orbit satellite communication systems

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2002
Hsin-Piao Lin
Abstract The concept behind path diversity is that a user who can access several satellites simultaneously will be able to communicate more effectively than a user who could only access one. The success of this method depends on the environment, the satellite constellation, and diversity combining technology. This paper explores the path diversity effects of non-geostationary orbit (NGO) satellite personal communication services, for different degrees of user mobility, under various scenarios, using the constellation of the global positioning system (GPS). Measurements are taken near downtown Taipei. Three types of mobilities (fixed-point, pedestrian, and vehicular) are examined, and the switch diversity and maximum ratio combining method are applied to determine the path diversity gain and calculate bit error probability. The error probability performance of applying diversity schemes in coherent binary phase shift keying (BPSK) and non-coherent differential phase shift keying (DPSK) modulations over Rician fading channels are also analysed and evaluated by using the characteristic function method. The results show that fading can be significantly reduced and diversity greatly increased. A significant diversity gain and improvement in bit error rate (BER) can be expected in all cases by simply applying switch diversity scheme. Besides, for the maximum ratio combining method, the results imply that summing two satellite signals suffices to increase diversity and improve the bit error rate performance. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Definition of effective diversity gain and how to measure it in a reverberation chamber

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2002
Per-Simon Kildal
Abstract The performance of cellular phones and other mobile or wireless terminals operating in multipath propagation environment can be greatly improved by introducing different diversity schemes. The improvement is characterized in terms of a diversity gain. An effective diversity gain is defined here. This is an absolute measure of diversity gain and can therefore be used to compare different diversity antennas. The Letter also shows how the effective diversity gain can be measured in a reverberation chamber. Measured effective diversity gains agree much better with theoretical diversity gains than measured values published previously. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 56,59, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10372 [source]